阅读说明：本技术 直流供配电系统 (DC power supply and distribution system ) 是由 桧垣优介 泉喜久夫 地道拓志 宅野嗣大 片冈拓也 于 2019-05-10 设计创作，主要内容包括：本直流供配电系统具备：多个配电线(L1、L2),分别与多个负载(A1、A2)对应地设置；第1变换器(3),将来自商用交流电源(10)的交流电压变换为多个直流电压(VA、VB)而分别供给到多个配电线；第2变换器(7),将来自发电和蓄电源(11)的直流电力变换为多个直流电力(P1、P2)而分别供给到多个配电线；以及电力控制部(9A),根据与第2变换器的效率关联的信息,以使第1变换器的效率上升的方式控制多个直流电力。(This direct current power supply and distribution system is provided with: a plurality of distribution lines (L1, L2) provided corresponding to the plurality of loads (A1, A2), respectively; a1 st converter (3) for converting an AC voltage from a commercial AC power supply (10) into a plurality of DC voltages (VA, VB) and supplying the DC voltages to a plurality of distribution lines, respectively; a2 nd converter (7) for converting the DC power from the power storage and generation source (11) into a plurality of DC powers (P1, P2) and supplying the DC powers to the plurality of power distribution lines, respectively; and a power control unit (9A) that controls the plurality of DC powers so as to increase the efficiency of the 1 st converter, based on information relating to the efficiency of the 2 nd converter.)

1. A DC power supply and distribution system is provided with:

a plurality of distribution lines provided corresponding to the plurality of loads, respectively;

a1 st converter that converts a voltage supplied from a1 st power source into a plurality of dc voltages corresponding to the plurality of loads, respectively, and supplies the plurality of dc voltages to the plurality of power distribution lines, respectively;

a2 nd converter for converting the power supplied from the 2 nd power supply into a plurality of dc powers corresponding to the plurality of loads, and supplying the plurality of dc powers to the plurality of distribution lines, respectively; and

and a1 st control unit configured to control the plurality of dc powers so as to increase efficiency of the 1 st converter, based on information related to efficiency of the 2 nd converter.

2. The DC power supply and distribution system according to claim 1,

the 1 st control unit controls the plurality of dc powers so as to increase the efficiencies of the 1 st and 2 nd inverters, based on the information on the efficiency of the 2 nd inverter and the information on the efficiency of the 1 st inverter.

3. The DC power supply and distribution system according to claim 2,

the DC power supply and distribution system further includes:

a1 st detection unit that detects information related to the efficiency of the 2 nd converter; and

a2 nd detection unit for detecting information related to the efficiency of the 1 st converter,

the 1 st control unit controls the plurality of dc powers based on detection results of the 1 st detection unit and the 2 nd detection unit.

4. The DC power supply and distribution system according to claim 1,

the DC power supply and distribution system further includes a power detection unit that detects power supplied from the 1 st power supply,

the 1 st control unit controls a total value of the plurality of dc powers so that the power value detected by the power detection unit is smaller than a predetermined value.

5. The DC power supply and distribution system according to claim 4,

the 1 st control unit generates an output power target value having a magnitude corresponding to a deviation between the power value detected by the power detection unit and the predetermined value, and controls the plurality of dc powers so that a total value of the plurality of dc powers becomes the output power target value and the output power target value decreases.

6. The DC power supply and distribution system according to claim 1,

a plurality of upper limit values are predetermined for the plurality of dc powers,

the 1 st control unit controls the magnitude of each of the plurality of dc powers so that each of the plurality of dc powers does not exceed the plurality of upper limit values.

7. The DC power supply and distribution system according to claim 1,

the DC power supply and distribution system further includes:

a plurality of load state detection units that detect states of the plurality of loads, respectively; and

and a2 nd control unit configured to control the magnitude of each of the plurality of dc voltages so that the power consumption of each of the plurality of loads becomes minimum, based on the detection results of the plurality of load state detection units.

8. The DC power supply and distribution system according to claim 7,

the 1 st control unit does not control the plurality of dc powers when a magnitude of at least one of the plurality of dc voltages changes.

9. The DC power supply and distribution system according to claim 1,

the 1 st power supply is a commercial ac power supply or a dc power supply,

the 2 nd power supply is a power generation and storage source that outputs direct-current power.

Technical Field

The present disclosure relates to a dc power supply and distribution system.

Background

For example, japanese patent application laid-open No. 2010-057231 (patent document 1) discloses a DC/DC converter that detects consumption current of a load having a plurality of states, detects the state of the load from the detected consumption current, and supplies an optimum power supply voltage in the state to the load.

Further, for example, japanese patent application laid-open No. 2015-163033 (patent document 2) discloses a DC power supply device including a plurality of DC/DC converters that convert DC power supplied from a DC power supply device into a plurality of DC powers and supply the DC powers to a plurality of loads, respectively. When there is a power saving request for instructing peak clipping (peak cut) of the amount of power consumption, supply of dc power to a load with low power consumption is stopped, and dc power is preferentially supplied to a load with high power consumption.

Documents of the prior art

Patent document 1: japanese patent application laid-open No. 2010-057231

Patent document 2: japanese laid-open patent publication No. 2015-163033

Disclosure of Invention

In patent document 1, the power supply voltage of the load is determined according to the consumption current of the load, but the loss generated in the DC/DC converter that generates the power supply voltage is not considered. Therefore, the efficiency of the system as a whole may be reduced.

In patent document 2, dc power is preferentially supplied to a load with large power consumption, but the efficiency of the entire system is not considered.

Therefore, a primary object of the present disclosure is to provide a dc power supply and distribution system with high efficiency.

The disclosed DC power supply and distribution system is provided with a plurality of distribution lines, a1 st converter, a2 nd converter, a1 st detection unit, and a1 st control unit. The plurality of distribution lines are provided corresponding to the plurality of loads, respectively. The 1 st converter converts a voltage supplied from the 1 st power source into a plurality of dc voltages corresponding to the plurality of loads, respectively, and supplies the plurality of dc voltages to the plurality of distribution lines, respectively. The 2 nd converter converts the electric power supplied from the 2 nd power supply into a plurality of dc powers corresponding to the plurality of loads, respectively, and supplies the plurality of dc powers to the plurality of distribution lines, respectively. The 1 st detection unit controls the plurality of direct-current powers so as to increase the efficiency of the 1 st converter based on information related to the efficiency of the 2 nd converter.

In this dc power supply and distribution system, since the plurality of dc powers are controlled so as to increase the efficiency of the 1 st inverter, the efficiency of the entire system can be improved.

Drawings

Fig. 1 is a block diagram showing the structure of a dc power supply and distribution system according to embodiment 1.

Fig. 2 is a circuit block diagram showing the configuration of the inverter 4 and the operation information detection unit 5 shown in fig. 1.

Fig. 3 is a circuit block diagram showing the configuration of the inverter 7 and the operation information detection unit 8 shown in fig. 1.

Fig. 4 is a circuit block diagram showing the configuration of the power control unit shown in fig. 1.

Fig. 5 is a graph showing the efficiency of the converter 4 shown in fig. 1.

Fig. 6 is a flowchart illustrating an operation of the power distribution control unit illustrated in fig. 4.

Fig. 7 is a flowchart illustrating the power distribution limiting process shown in fig. 6.

Fig. 8 is a flowchart showing an operation of the power distribution control unit included in the dc power supply and distribution system according to embodiment 2.

Fig. 9 is a block diagram showing the structure of the dc power supply and distribution system according to embodiment 3.

Fig. 10 is a circuit block diagram showing the configuration of the power control unit shown in fig. 9.

Fig. 11 is a graph showing the efficiency of the converter 7 shown in fig. 9.

Fig. 12 is a flowchart illustrating an operation of the power distribution control unit illustrated in fig. 10.

FIG. 13 is a block diagram showing comparative example 1 of embodiments 1 to 3.

FIG. 14 is a block diagram showing another comparative example 2 of embodiments 1 to 3.

FIG. 15 is a block diagram showing still another comparative example 3 of embodiments 1 to 3.

Fig. 16 is a diagram showing a comparison of the number of stages of the converters of comparative examples 1 to 3.

(symbol description)

A1, a2, B1, B2, C1: a load; L1-L3: distribution lines (distribution lines); 1. 2: a load state detection unit; 3: a voltage control unit; 3a, 9 a: a processing circuit; 4. 7, 75: a converter; 5. 8: an operation information detection unit; 6: a power detection unit; 9. 9A: a power control unit; 10: a commercial alternating current power supply; 11: a power generation and storage source; 15. 60, 71-73: an AC/DC converter; 16. 27: a capacitor; 17. 26, 53, 61, 76: a DC/DC converter; 20-22, 30-32: a voltage detector; 23-25, 33-35: a current detector; 28: a chopper circuit; 40: a subtractor; 41: a PI control unit; 42. 42A: a power distribution control unit; 43: a storage unit; 44: a reference current generating section; 50: an alternating current power receiving apparatus; 51. 77: a DC/AC converter; 52. 54, 55: a main body.

Detailed Description

Embodiment 1.

Fig. 1 is a block diagram showing the structure of a dc power supply and distribution system according to embodiment 1. In fig. 1, the dc power supply and distribution system includes a plurality of (2 in this example) distribution lines L1, L2, load state detection units 1, 2, a voltage control unit 3, inverters 4, 7, operation information detection units 5, 8, a power detection unit 6, and a power control unit 9.

Generally, loads are classified into general power system loads such as air conditioners and elevators, factory power system loads such as conveyor belts and press machines of factories, lighting loads, and general loads such as OA equipment. These loads differ from each other in power usage characteristics for one day and optimal operating voltage for each operating state. Therefore, it is easier to improve efficiency when a specific voltage is supplied to each of the loads than when the same voltage is supplied to the loads.

Since the operating characteristics of at least a power load including a general power load and a plant power load are greatly different from those of other loads (a lighting load and a general load), it is easier to improve the efficiency when the voltage supplied to the power load and the voltage supplied to the other loads are set to different values.

Therefore, in embodiment 1, the loads are divided into a group a (e.g., a power load) and a group B (e.g., another load), and a distribution line L1 that supplies a dc voltage VA to a plurality of (2 in this example) loads a1 and a2 belonging to the group a and a distribution line L2 that supplies a dc voltage VB to a plurality of (2 in this example) loads B1 and B2 belonging to the group B are provided, respectively. The loads a1 and a2 of the group a are connected to the distribution line L1, and the loads B1 and B2 of the group B are connected to the distribution line L2.

In addition, although the positive-side electric wire and the negative-side electric wire are necessary for supplying the dc voltage, only 1 distribution line is shown in fig. 1 for supplying 1 dc voltage for simplification of the drawing and the explanation.

Further, when the dc voltages VA and VB are changed according to the state of the load (such as the load factor, the current consumption, and the power consumption), the efficiency of the load is increased and the power consumption (or the current consumption) is reduced, as compared to the case where the dc voltages VA and VB are fixed to the constant voltages. Therefore, the load state detector 1 is coupled to the distribution line L1, detects the states (e.g., load coefficients) of the loads a1 and a2 of the group a, and supplies a signal Φ 1 indicating the detected values thereof to the voltage controller 3. The load state detector 2 is coupled to the distribution line L2, detects the states (e.g., load coefficients) of the loads B1 and B2 of the group B, and supplies a signal Φ 2 indicating the detected values to the voltage controller 3.

The voltage control unit 3 controls the reference voltage VAR so as to reduce the power consumption (or current consumption) of the loads a1 and a2 of the group a based on the signal Φ 1 from the load state detection unit 1, and sets the reference voltage VAR to an optimum value. The voltage control unit 3 controls the reference voltage VBR so as to reduce the power consumption (or current consumption) of the loads B1 and B2 of the group B based on the signal Φ 2 from the load state detection unit 2, and sets the reference voltage VBR to an optimal value.

The function of the voltage control section 3 can be realized by the processing circuit 3 a. The processing circuit 3a is dedicated hardware such as a dedicated processing circuit, or a processor and a storage device. In the case of using dedicated hardware, the dedicated processing Circuit is a single Circuit, a composite Circuit, a programmed processor, a processor programmed in parallel, an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or a structure obtained by combining them.

When a processor and a storage device are used, the functions described above can be implemented by software, firmware, or a combination thereof. The software or firmware is described as a program and stored in a storage device. The processor reads out and executes the program stored in the storage device. These programs can also be said to be programs that cause a computer to execute the procedures and methods for realizing the functions described above.

As the Memory device, a semiconductor Memory such as a RAM (Random Access Memory), a ROM (Read Only Memory), a flash Memory, an EPROM (Erasable Programmable Read Only Memory), or an EEPROM (Electrically Erasable Programmable Read Only Memory (japanese registered trademark)) is used. The semiconductor memory may be a nonvolatile memory or a volatile memory. The storage device may be a magnetic disk, a flexible disk, an optical disk, a compact disk, a mini disk, or a DVD (Digital Versatile disk), in addition to the semiconductor memory.

Inverter 4 (1 st inverter) converts ac voltage VAC supplied from commercial ac power supply 10 as a main power supply (1 st power supply) into dc voltages VA and VB having the same values as reference voltages VAR and VBR, respectively, and supplies these dc voltages VA and VB to power distribution lines L1 and L2, respectively. The operation information detection unit 5 detects information D1 related to the efficiency η 1 of the inverter 4, and supplies the detected information D1 to the power control unit 9.

Further, a dc power supply may be provided as the main power supply instead of the commercial ac power supply 10. In this case, the converter 4 converts the dc voltage supplied from the dc power supply into dc voltages VA and VB having the same values as the reference voltages VAR and VBR, respectively.

Fig. 2 is a circuit block diagram showing the configuration of the inverter 4 and the operation information detection unit 5. In fig. 2, the converter 4 includes an AC/DC converter 15, a capacitor 16, and a DC/DC converter 17. The AC/DC converter 15 converts a three-phase AC voltage VAC supplied from the commercial AC power supply 10 into a DC voltage VDC 1. The capacitor 16 stabilizes and smoothes the dc voltage VDC 1. The DC/DC converter 17 converts the direct-current voltage VDC1 into a direct-current voltage VA of the same value as the reference voltage VAR, and converts the direct-current voltage VDC1 into a direct-current voltage VB of the same value as the reference voltage VBR.

The DC/DC converter 17 includes, for example, the 1 st and 2 nd voltage followers. The 1 st voltage follower is driven by the dc voltage VDC1, and outputs a dc voltage VA having the same value as the reference voltage VAR to the distribution line L1. The 2 nd voltage follower is driven by the dc voltage VDC1, and outputs the dc voltage VB of the same value as the reference voltage VBR to the distribution line L2. For example, the dc voltage VDC1 is a voltage higher than the dc voltages VA and VB.

The operation information detection unit 5 includes voltage detectors 20 to 22 and current detectors 23 to 25. Voltage detector 20 detects an instantaneous value of ac voltage VAC supplied from commercial ac power supply 10, and outputs signal Φ 20 indicating the detected value. The voltage detector 21 detects the output DC voltage VA of the DC/DC converter 17 and outputs a signal Φ 21 indicating the detected value. The voltage detector 22 detects the output DC voltage VB of the DC/DC converter 17 and outputs a signal Φ 22 indicating the detected value.

The current detector 23 detects an instantaneous value of the alternating current IAC flowing from the commercial alternating-current power supply 10 into the AC/DC converter 15, and outputs a signal Φ 23 indicating the detected value. The current detector 24 detects the direct current IA flowing from the DC/DC converter 17 through the distribution line L1, and outputs a signal Φ 24 indicating the detected value. The current detector 25 detects a direct current IB flowing from the DC/DC converter 17 through the distribution line L2, and outputs a signal Φ 25 indicating the detected value. The signals Φ 20 to Φ 25 are supplied to the power control unit 9 as information D1 relating to the efficiency η 1 of the inverter 4.

When the commercial ac power supply 10 is stable, a set value based on the rated voltage of the commercial ac power supply 10 may be used instead of the output signal Φ 20 of the voltage detector 20. Instead of the output signals Φ 21, Φ 22 of the voltage detectors 21, 22, the reference voltages VAR, VBR may be used. In this case, the configuration of the operation information detection unit 5 can be simplified.

Returning to fig. 1, power detection unit 6 detects ac power P supplied from commercial ac power supply 10 to inverter 4, and supplies signal Φ P representing the detected value to power control unit 9. Power detection unit 6 detects an instantaneous value of ac voltage VAC supplied from commercial ac power supply 10 and an instantaneous value of ac current IAC flowing from commercial ac power supply 10 into converter 4, and obtains ac power from these detected values.

Power detection unit 6 obtains, for example, effective value VACe of ac voltage VAC, effective value IACe of ac current IAC, and phase difference θ between ac voltage VAC and ac current IAC from the detected values of ac voltage VAC and ac current IAC, and obtains ac power P ═ VACe × IACe × cos θ from these values.

The inverter 7 (the 2 nd inverter) is controlled by control signals CNT1 and CNT2 supplied from the power control unit 9, converts dc power supplied from the power generation and storage source 11 as a subsidiary power source (the 2 nd power source) into two dc powers P1 and P2, and supplies the dc powers P1 and P2 to the distribution lines L1 and L2, respectively. The operation information detection unit 8 detects information D2 related to the efficiency η 2 of the inverter 7, and supplies the detected information D2 to the power control unit 9.

Fig. 3 is a circuit block diagram showing the configuration of the inverter 7 and the operation information detection unit 8. In fig. 3, the converter 7 includes a DC/DC converter 26, a capacitor 27, and a chopper circuit 28. DC/DC converter 26 converts DC voltage VDC2 supplied from power generation and storage source 11 into DC voltage VDC3 having the same value as reference voltage VDCR supplied from power control unit 9.

The power generation and storage source 11 is a power generation device that generates dc power, a battery that stores dc power, or a combination thereof, and outputs dc power. Examples of the power generation device include a solar cell, a wind power generation device, a tidal power generation device, a geothermal power generation device, and a fuel cell. Further, as the battery, there are a lead storage battery, a lithium ion battery, and the like, and there are also batteries mounted on automobiles. The capacitor 27 stabilizes and smoothes the dc voltage VDC 3.

The chopper circuit 28 converts the DC power supplied from the DC/DC converter 26 into DC powers P1 and P2 in accordance with control signals CNT1 and CNT2 supplied from the power control unit 9, and supplies the DC powers P1 and P2 to the distribution lines L1 and L2, respectively.

The chopper circuit 28 includes, for example, 1 st and 2 nd choppers. The control signals CNT1 and CNT2 are, for example, PWM (Pulse Width Modulation) signals. For example, the dc voltage VDC3 is a voltage higher than the dc voltages VA and VB. The 1 st chopper converts a direct-current voltage VDC3 supplied from the DC/DC converter 26 into a1 st pulse voltage train in accordance with a control signal CNT1 as a pulse signal train, and supplies the 1 st pulse voltage train to the distribution line L1 via a built-in reactor, thereby outputting a direct-current power P1 to the distribution line L1. When the duty ratio of control signal CNT1 increases or decreases, dc power P1 also increases or decreases.

The 2 nd chopper converts the DC voltage VDC3 supplied from the DC/DC converter 26 into a2 nd pulse voltage train in accordance with a control signal CNT2 as a pulse signal train, and supplies the converted DC voltage to the distribution line L2 via a built-in reactor, thereby outputting the DC power P2 to the distribution line L2. When the duty ratio of control signal CNT2 increases or decreases, dc power P2 also increases or decreases.

Further, in the case where the power generation and storage source 11 is a battery, it is also possible to store the dc power supplied from the inverter 4 and the regenerative power supplied from the load in the power generation and storage source 11. In this case, the chopper circuit 28 converts the dc voltages VA and VB supplied from the converter 4 and the load via the distribution lines L1 and L2 into the dc voltage VDC 3. The DC/DC converter 26 stores the DC power supplied from the chopper circuit 28 in the power generation and storage source 11.

The operation information detection unit 8 includes voltage detectors 30 to 32 and current detectors 33 to 35. The voltage detector 30 detects the dc voltage VDC2 supplied from the power generation and storage source 11, and outputs a signal Φ 30 indicating the detected value. The voltage detector 31 detects the output dc voltage VA of the chopper circuit 28, and outputs a signal Φ 31 indicating the detected value. The voltage detector 32 detects the output dc voltage VB of the chopper circuit 28, and outputs a signal Φ 32 indicating the detected value.

The current detector 33 detects a direct current IDC2 flowing from the power generation and storage source 11 to the DC/DC converter 26, and outputs a signal Φ 33 indicating the detected value. The current detector 34 detects a direct current I1 flowing from the chopper circuit 28 through the distribution line L1, and outputs a signal Φ 34 indicating the detected value. The current detector 35 detects a direct current I2 flowing from the chopper circuit 28 through the distribution line L2, and outputs a signal Φ 35 indicating the detected value. The signals Φ 30 to Φ 35 are supplied to the power control unit 9 as information D2 relating to the efficiency η 2 of the inverter 7.

When the power generation and storage source 11 is stable, a set value based on the rated voltage of the power generation and storage source 11 may be used instead of the output signal Φ 30 of the voltage detector 30.

The power control unit 9 controls the output powers P1 and P2 of the inverter 7 so that the efficiency η of the inverters 4 and 7 becomes maximum, based on the information D1 and D2 from the operation information detection units 5 and 8 and the signal Φ P from the power detection unit 6. The function of the power control unit 9 can be realized by the processing circuit 9 a. The processing circuit 9a is identical to the processing circuit 3 a. The voltage control unit 3 and the power control unit 9 may be configured by 1 processing circuit.

Fig. 4 is a block diagram showing essential parts of the power control section 9. In fig. 4, the power control unit 9 includes a subtractor 40, a PI (Proportional Integral) control unit 41, a power distribution control unit 42, a storage unit 43, and a PWM control unit 44.

The dc power supply and distribution system has a basic function of converting an ac voltage from commercial ac power supply 10 into dc voltages VA and VB and supplying the dc voltages VA and VB to loads a1, a2, B1, and B2, and has an additional function of suppressing the influence of loads a1, a2, B1, and B2 on commercial ac power supply 10. Therefore, in a basic method of using the power generation and storage source 11, the power generation and storage source 11 is charged and discharged so that the ac power P supplied from the commercial ac power source 10 becomes equal to or less than the desired set value PS.

The desired set value PS is an upper limit value or a target value of the received power set in response to a request from a user performing energy management, a remote controller, or the like. The desired set value PS is referred to as a purchase power set value. In this dc power supply and distribution system, the output power target value PT is generated so that the ac power P supplied from the commercial ac power supply 10 becomes equal to or less than the purchased power setting value PS at the present time or immediately before.

Therefore, the subtractor 40 obtains a deviation Δ P between the output signal Φ P of the power detection unit 6 (i.e., the detected value of the ac power P supplied from the commercial ac power supply 10) and the purchased power setting value PS as Φ P-PS. The PI control unit 41 performs PI control on the deviation Δ P to generate an output power target value PT.

The output power target value PT is a value corresponding to the total value (P1+ P2) of the dc powers P1 and P2 supplied from the inverter 7 to the distribution lines L1 and L2. When the received power P exceeds the purchase power setting value PS, the positive output power target value PT can be obtained. When the output power target value PT is positive, dc power is supplied from the power generation and storage source 11 to the loads a1, a2, B1, and B2 via the inverter 7. Although not shown, charging or discharging of the power generation and storage source 11 can be suppressed as necessary by adding a limiter having an upper limit and a lower limit to the output power target value PT.

The power distribution control unit 42 obtains the efficiency η of the inverters 4 and 7 from the information D1 (i.e., the signals Φ 20 to Φ 25) and the information D2 (i.e., the signals Φ 30 to Φ 35) supplied from the operation information detection units 5 and 8, and generates the reference powers P1R and P2R so that the efficiency η is maximized. Wherein, P1R + P2R is PT.

The power distribution control unit 42 obtains the efficiency η of the inverters 4 and 7 as follows, for example. Power distribution control unit 42 obtains effective value VACr of ac voltage VAC from output signal Φ 20 of voltage detector 20 (fig. 2), obtains effective value IACr of ac current IAC from output signal Φ 23 of current detector 23 (fig. 2), obtains phase difference θ between ac voltage VAC and ac current IAC from signals Φ 20 and Φ 23, and obtains power PI1 ═ VACr × IACr × cos θ supplied from commercial ac power supply 10 to inverter 4.

The power distribution control unit 42 obtains the output power PO1 of the inverter 4, i.e., VA × IA + VB × IB, from the output signals Φ 21 and Φ 22 of the voltage detectors 21 and 22 (fig. 2) and the output signals Φ 24 and Φ 25 of the current detectors 24 and 25 (fig. 2).

The power distribution control unit 42 obtains the power PI2 supplied from the power generation and storage source 11 to the inverter 7 as VDC2 × IDC2 from the output signal Φ 30 of the voltage detector 30 (fig. 3) and the output signals Φ 30 and Φ 33 of the current detector 33 (fig. 3).

The power distribution control unit 42 obtains the output power P1 of the inverter 7 as VA × I1 from the output signal Φ 31 of the voltage detector 31 (fig. 3) and the output signal Φ 34 of the current detector 34 (fig. 3). The power distribution control unit 42 obtains the output power P2 of the inverter 7 as VB × I2 from the output signal Φ 32 of the voltage detector 32 (fig. 3) and the output signal Φ 35 of the current detector 35 (fig. 3). Then, power distribution control unit 42 obtains efficiency η of inverters 4 and 7 (PO1+ P1+ P2)/(PI1+ PI2) from PI1, PO1, PI2, P1, and P2.

Fig. 5 is a graph showing the efficiency η 1 of the converter 4. In fig. 5, the abscissa represents the ratio PO1/Pc1 (%) between the output power PO1 of the inverter 4 and the rated power Pc1, and the ordinate represents the efficiency η 1. The efficiency η 1 varies depending on the value of PO1/Pc1, and becomes a peak value at a certain value of PO1/Pc 1. As PO1/Pc1 increases compared to a certain value, the efficiency η 1 slowly decreases. As PO1/Pc1 decreases compared to a certain value, the efficiency η 1 decreases sharply.

The efficiency η 2 of the converter 7 also changes in the same manner as the efficiency η 1 of the converter 4. If the output powers P1, P2 of the inverter 7 are varied, the efficiency η 2 of the inverter 7 varies, and the output power PO1 of the inverter 4 also varies and the efficiency η 1 of the inverter 4 also varies.

Fig. 6 is a flowchart illustrating an operation of the power distribution control unit 42. In step S1 of fig. 6, the power distribution control unit 42 executes the power distribution update process. In the power distribution update process, the power distribution control unit 42 adds the power distribution correction amount Δ R to the previous power distribution rate RAn for the distribution line L1 to obtain the current power distribution rate RA (n +1) ═ RAn + Δ R, and also obtains the current power distribution rate RB (n +1) ═ 1-RA (n +1) for the distribution line L2.

In step S2, the power distribution control unit 42 executes power distribution limiting processing. Upper limit values P1max and P2max are set for dc powers P1 and P2 output to distribution lines L1 and L2, respectively, in accordance with rated power of hardware such as circuit components constituting inverter 7.

Therefore, when the dc power corresponding to the output power target value PT is distributed to the distribution lines L1 and L2, the output powers P1 and P2 distributed to the distribution lines L1 and L2 are limited to ranges not exceeding the upper limit values P1max and P2max, respectively. Therefore, in the power distribution limiting process (S2), the limit values RAmax and RBmax of the power distribution rates RA (n +1) and RB (n +1) are calculated so that the output powers P1 and P2 do not exceed the upper limit values P1max and P2max, respectively, after the update of the power distribution.

Fig. 7 is a flowchart illustrating a method of calculating the limit value RAmax of the power distribution rate RA (n + 1). In step S11 of fig. 7, the power distribution control unit 42 divides the rated power PcA of the portion of the inverter 7 corresponding to the distribution line L1 by the absolute value | PT | of the output power target value PT to calculate the limit value RAmax equal to PcA/| PT |.

In step S12, the power distribution control unit 42 determines whether or not the limit value RAmax is greater than 1.0. When RAmax >1.0, the power distribution control unit 42 sets RAmax to 1.0 in step S13, and stores RAmax to 1.0 in step S14. If RAmax >1.0 is not present, the power distribution control unit 42 stores RAmax calculated in step S11 in step S14.

The limit value RBmax of the power distribution rate RB (n +1) is calculated by the same method as the limit value RAmax of the power distribution rate RA (n + 1). However, when the maximum value of the output power target value PT matches the maximum value of the total value P1+ P2 of the output powers P1 and P2 corresponding to the distribution lines L1 and L2, RBmax becomes 1-RAmax, and therefore RBmax can be easily obtained.

In the power distribution limiting process (S2), the power distribution control unit 42 limits the power distribution rates RA (n +1) and RB (n +1) to the limit values RAmax and RBmax, respectively. As a result, the output powers P1, P2 of the inverter 7 are limited to the upper limit values P1max, P2max, respectively, or less. When P1> P1max and P2< P2max, the power distribution control unit 42 increases P2 by the amount of power (P1-P1 max). When P1< P1max and P2> P2max, the power distribution control unit 42 increases P1 by the amount of power (P2-P2 max).

The power distribution control unit 42 multiplies the output power target value PT by the power distribution ratio RA (n +1) to obtain reference power P1R ═ PT × RA (n +1), and multiplies the output power target value PT by the power distribution ratio RB (n +1) to obtain reference power P2R ═ PT × RB (n + 1).

Returning to fig. 6, in step S3, the power distribution control unit 42 executes power convergence waiting processing. If the power distribution limiting process is executed (S2), the dc power P1, P2 supplied from the inverter 7 to the distribution lines L1, L2 varies. However, when the power distribution ratios RA and RB are not changed, the output powers P1 and P2 are not changed. The output powers P1 and P2 of the inverter 7 are not instantaneously varied but varied with a certain time constant.

Therefore, in the power convergence waiting process (S3), the power distribution control unit 42 waits until the output powers P1 and P2 of the inverter 7 stabilize to constant values. In this case, the timer may measure the time and wait until the set time elapses, or the power detector may detect the powers P1 and P2 and wait until these detection values become constant. After the output powers P1, P2 are stabilized, the process proceeds to the next process. If it is not determined that the stabilization is completed even if the output powers P1 and P2 converge to a constant value, for example, timeout processing may be performed to determine that the stabilization is completed.

In step S4, the power distribution control unit 42 executes the operation information update process. In this process, the power distribution control unit 42 acquires the operation information D1 and D2 of the inverters 4 and 7 from the operation information detection units 5 and 8 and stores the operation information in the storage unit 43, obtains the efficiency η (n +1) of the inverters 4 and 7 from the operation information D1 and D2, and stores the obtained efficiency η (n +1) in the storage unit 43. At this time, the power distribution control unit 42 stores the current operation information D1, D2 and the efficiency η (n +1) at an address different from the stored previous operation information D1, D2 and the efficiency η n.

In step S5, the power distribution control unit 42 executes effect determination processing. In this process, the power distribution control unit 42 compares the previous efficiency η n stored in the storage unit 43 with the current efficiency η (n +1), and determines whether the efficiency η has increased [ η (n +1) > η n ], has not changed [ η (n +1) ═ η n ], or has decreased [ η (n +1) < η n ].

In step S6, the power distribution control section 42 executes power distribution correction amount calculation processing. In this process, the power distribution control unit 42 sets the pre-update power distribution correction amount Δ Rn as the post-update power distribution correction amount Δ R as it is when the efficiency η increases [ η (n +1) > η n ] and when the efficiency η does not change [ η (n +1) = η n ], and returns to step S1.

When the efficiency η is decreased, [ η (n +1) < η n ], the power distribution control unit 42 reverses the polarity of the pre-update power distribution correction amount Δ R to generate the post-update power distribution correction amount Δ R, and returns to step S1. By repeatedly executing steps S1 to S6, the reference powers P1R and P2R can be generated so that the efficiency η of the inverters 4 and 8 becomes maximum.

Returning to fig. 4, the PWM control unit 44 obtains the output power P1 of the inverter 7 as VA × I1 from the output signal Φ 31 of the voltage detector 31 (fig. 3) and the output signal Φ 34 of the current detector 34 (fig. 3) included in the operation information D2. Then, PWM control unit 44 controls the duty ratio of control signal CNT1 so that output power P1 of inverter 7 becomes reference power P1R.

Further, the PWM control unit 44 obtains the output power P2 of the inverter 7 as VB × I2 from the output signal Φ 32 of the voltage detector 32 (fig. 3) and the output signal Φ 35 of the current detector 35 (fig. 3) included in the operation information D2. Then, PWM control unit 44 controls the duty ratio of control signal CNT2 so that output power P2 of inverter 7 becomes reference power P2R.

Next, the operation of the dc power supply and distribution system shown in fig. 1 to 7 will be described. In the dc power supply and distribution system, a plurality of loads are divided into a group a and a group B, the loads a1 and a2 of the group a are connected to the distribution line L1, and the loads B1 and B2 of the group B are connected to the distribution line L2.

The load state detector 1 detects the states (for example, load factors) of the loads a1 and a2, and based on the detection results, the voltage controller 3 generates the optimum reference voltage VAR so that the power consumption (or current consumption) of the loads a1 and a2 is minimized.

Further, the load state detector 2 detects the states (for example, load factors) of the loads B1 and B2, and based on the detection results, the voltage controller 3 generates the optimum reference voltage VBR so that the power consumption (or current consumption) of the loads B1 and B2 is minimized.

Ac voltage VAC supplied from commercial ac power supply 10 is converted by converter 4 into dc voltage VA having the same value as reference voltage VAR and supplied to distribution line L1, and is converted by converter 4 into dc voltage VB having the same value as reference voltage VBR and supplied to distribution line L2.

Ac power P supplied from commercial ac power supply 10 to inverter 4 is detected by power detection unit 6, information D1 relating to the efficiency of inverter 4 is detected by operation information detection unit 5, and information D2 relating to the efficiency of inverter 7 is detected by operation information detection unit 8.

Based on the detection results of the power detection unit 6 and the operation information detection units 5 and 8, the power distribution control unit 42 generates the reference powers P1R and P2R so that the ac power P is equal to or less than the purchased power setting value PS and the efficiency η of the inverters 4 and 7 is maximized.

The dc power supplied from the power generation and storage source 11 is converted by the converter 7 into dc power P1 having the same value as the reference power P1R and supplied to the distribution line L1, and is converted by the converter 7 into dc power P2 having the same value as the reference power P2R and supplied to the distribution line L2.

As described above, in embodiment 1, dc power P1 and P2 are supplied to distribution lines L1 and L2 so that efficiency η of inverters 4 and 7 is maximized, and therefore the efficiency of the entire system can be improved.

Further, since the dc voltage VA of the distribution line L1 is controlled so as to minimize the power consumption (or current consumption) of the loads a1 and a2, and the dc voltage VB of the distribution line L2 is controlled so as to minimize the power consumption (or current consumption) of the loads B1 and B2, an optimal dc voltage can be supplied for each type of load.

In embodiment 1, the case where 1 set of the power generation and storage source 11 and the inverter 7 is provided has been described, but a plurality of sets of the power generation and storage source 11 and the inverter 7 may be provided. When a plurality of sets of the power generation and storage source 11 and the inverter 7 are provided, the operation information detection unit 8 and the power control unit 9 are provided for each set. Alternatively, 1 power control unit 9 may be provided in common for a plurality of inverters 7.

Embodiment 2.

In embodiment 1, voltage controller 3 changes output voltages VA and VB of inverter 4 to optimal values so as to reduce power consumption (or current consumption) of loads a1, a2, B1, and B2. If dc voltages VA and VB change, power consumption (or current consumption) of loads a1, a2, B1, and B2 changes, and voltage control unit 3 further changes output voltages VA and VB of inverter 4. If the output voltages VA and VB of the converter 4 vary, the output power of the converter 4 varies, and the efficiency η 1 of the converter 4 varies (fig. 3).

The power control unit 9 obtains the efficiency η of the inverters 4 and 7 from the operation information D1 and D2 of the inverters 4 and 7, and changes the output powers P1 and P2 of the inverter 7 so as to decrease the efficiency η. Therefore, if output power P1, P2 of inverter 7 is changed by power control unit 9 when output voltage VA, VB of inverter 4 is changed by voltage control unit 3, there is a possibility that power control unit 9 may malfunction under the influence of voltage control unit 3. Embodiment 2 is intended to solve this problem.

Fig. 8 is a flowchart showing an operation of the power distribution control unit 42 included in the dc power supply and distribution system according to embodiment 2, and is a diagram compared with fig. 6. Referring to fig. 8, embodiment 2 differs from embodiment 1 in that steps S21 to S23 are added before step S1.

In step S21, the power distribution control unit 42 executes the operation information update process. In this process, the power distribution control unit 42 acquires the operation information D1 and D2 of the inverters 4 and 7 from the operation information detection units 5 and 8 and stores the information in the storage unit 43. At this time, the power distribution control unit 42 stores the current operation information D1 and D2 in the address different from the stored previous operation information D1 and D2.

In step S22, the power distribution control unit 42 executes an output voltage fluctuation detection process. In this process, the power distribution control unit 42 reads the last output voltages VAn and VBn and the current output voltages VA (n +1) and VB (n +1) from the storage unit 43, and obtains the deviation Δ VA ═ VA (n +1) -VAn and Δ VB ═ VB (n +1) -VBn between the current output voltages VA (n +1) and VB (n +1) and the last output voltages VAn and VBn.

In step S22, power distribution control unit 42 determines that output voltages VA and VB have changed when at least one of the absolute value of Δ VA and the absolute value of Δ VB exceeds a set value, and determines that output voltages VA and VB have not changed when both the absolute value of Δ VA and the absolute value of Δ VB are smaller than the set value.

If it is determined in step S23 that output voltages VA and VB are unchanged, the process proceeds to step S1, and if it is determined in step S23 that output voltages VA and VB are changed, the process returns to step S21. Other structures and operations are the same as those in embodiment 1, and therefore, description thereof will not be repeated.

In embodiment 2, since output power P1, P2 of inverter 7 is not controlled until the change in output voltage VA, VB of inverter 4 disappears, it is possible to prevent power control unit 9 from malfunctioning due to the influence of voltage control unit 3.

Further, a method of preventing the overlap between the time period in which the voltage control unit 3 operates and the time period in which the power control unit 9 operates using the synchronization signal is also considered. However, in this method, when the distance between the installation location of the voltage control unit 3 and the installation location of the power control unit 9 is long, there is a concern that a signal line for transmitting and receiving the synchronization signal between the voltage control unit 3 and the power control unit 9 becomes long, the price of the signal line becomes high, or the synchronization signal becomes poor. In contrast, in embodiment 2, there is no such concern even when the distance between the installation location of the voltage control unit 3 and the installation location of the power control unit 9 is long.

Embodiment 3.

In embodiment 1, the operation information of inverters 4 and 7 is detected by operation information detectors 5 and 8, and output powers P1 and P2 of inverter 7 are controlled based on the detection results. However, when the distance between the installation location of inverter 7 and the installation location of inverter 4 is long, the operation information of inverter 4 may not be used. Therefore, in embodiment 3, a method of performing power distribution control of inverter 7 without using operation information of inverter 4 will be described.

Fig. 9 is a block diagram showing the structure of the dc power supply and distribution system according to embodiment 3, and is a diagram compared with fig. 1. Referring to fig. 9, the dc power supply and distribution system differs from the dc power supply and distribution system of fig. 1 in that the operation information detection unit 5 is removed and the power control unit 9 is replaced with a power control unit 9A.

Fig. 10 is a block diagram showing the configuration of the power control unit 9A, and is a diagram compared with fig. 4. Referring to fig. 10, a point at which power control unit 9A differs from power control unit 9 of fig. 4 is a point at which power distribution control unit 42 is replaced with power distribution control unit 42A. In a range where the efficiency η 2 of the inverter 7 is larger than the lower limit η L, the power distribution control unit 42A generates the reference powers P1R and P2R so that the efficiency η 1 of the inverter 4 becomes maximum, based on the output power target value PT.

That is, the relationship between the output power target value PT corresponding to the sum of the output powers P1, P2 of the inverter 7, the proportional constant Gpi of the PI control unit 41, the ac power P supplied from the commercial ac power supply 10 to the inverter 4, and the utility power setting value PS that is the upper limit value of the ac power P is expressed by the following expression (1).

PT＝Gpi×(P-PS)≥0 …(1)

A relationship between ac power P, the total value PLD of the power consumptions of loads a1, a2, B1, and B2, power loss PL1 of inverter 4, and the total value PO2 of output powers P1 and P2 of inverter 7, which is P1+ P2, is expressed by the following expression (2).

P＝PLD+PL1-PO2 …(2)

The following formula (3) is obtained from the above formulas (1) and (2).

PT＝Gpi(PLD+PL1-PO2-PS) …(3)

From equation (3), it is understood that the output power target value PT of the inverter 7 is proportional to the power loss PL1 of the inverter 4. Therefore, in the power distribution control described in embodiment 1, when the distribution of the output powers P1 and P2 is controlled while maintaining the total value PO2 of the output powers P1 and P2 at a constant value P1+ P2, if the power loss PL1 of the inverter 4 increases or decreases, the output power target value PT increases or decreases.

Therefore, by controlling the distribution of the output powers P1, P2 in accordance with the increase or decrease of the output power target value PT, the power loss PL1 of the inverter 4 can be minimized, and the efficiency η 1 of the inverter 4 can be maximized.

However, even if the efficiency η 1 of the converter 4 becomes the maximum value, if the efficiency η 2 of the converter 7 becomes a very small value, the efficiency of the entire dc power supply and distribution system is lowered. Therefore, in embodiment 3, the power loss PL1 of the inverter 4 is minimized in the range where the efficiency η 2 of the inverter 7 is larger than the lower limit value η L.

Fig. 11 is a graph showing the efficiency η 2 of the converter 7. In fig. 11, the abscissa represents the ratio PO2/Pc2 (%) between the output power PO2 of the inverter 7 and the rated power Pc2, and the ordinate represents the efficiency η 2. The efficiency η 2 varies depending on the value of PO2/Pc2, and becomes a peak value at a certain value of PO2/Pc 2. As PO2/Pc2 increases compared to a certain value, the efficiency η 2 slowly decreases. As PO2/Pc2 decreases compared to a certain value, the efficiency η 2 drops sharply. A lower limit value η L is set for the efficiency η 2 of the converter 7. The lower limit η L is set to a value slightly smaller than the efficiency η 2 when PO2/Pc2 is 100 (%), for example.

Fig. 12 is a flowchart showing an operation of the power distribution control unit 42A, and is a diagram compared with fig. 6. Fig. 12 differs from fig. 6 in that steps S4 to S6 are replaced with steps S4A to S6A, respectively.

In step S4A, power distribution control unit 42A executes the operation information update process. In this process, the power distribution control unit 42A obtains the output power target value PT from the PI control unit 41 (fig. 10) and stores it in the storage unit 43. At this time, the power distribution control unit 42 stores the present output power target value PT (n +1) at an address different from the stored previous output power target value PTn.

Further, power distribution control unit 42A obtains operation information D2 of inverter 7 from operation information detection unit 8 and stores it in storage unit 43, obtains efficiency η 2(n +1) of inverter 7 from this operation information D2, and stores the obtained efficiency η 2(n +1) in storage unit 43. At this time, the power distribution control unit 42A stores the current operation information D2 and the efficiency η 2(n +1) at an address different from the stored previous operation information D2 and efficiency η 2 n.

In step S5A, power distribution control unit 42A executes the effect determination process. In this process, the power distribution control unit 42A determines whether the efficiency η 2(n +1) of the converter 7 is greater than the lower limit η L by [ η 2(n +1) > η L ], the efficiency η 2(n +1) of the converter 7 is the same as the lower limit η L [ η 2(n +1) ═ η L ], or the efficiency η 2(n +1) of the converter 7 is smaller than the lower limit η L by [ η 2(n +1) < η L ].

The power distribution control unit 42A compares the previous output power target value PTn with the current output power target value PT (n +1), and determines whether the output power target value PT has fallen [ PT (n +1) < PTn ], the output power target value PT has not changed [ PT (n +1) < PTn ], or the output power target value PT has risen [ PT (n +1) > PTn ].

In step S6A, the power distribution control portion 42A executes power distribution correction amount calculation processing. In this process, the power distribution control unit 42A sets the power distribution correction amount Δ Rn before updating as the updated power distribution correction amount Δ R as it is when the output power target value PT is decreased and when the output power target value PT is not changed [ PT (n +1) < PTn ] and [ PT (n +1) < PTn ] when [ η 2(n +1) > η L ] of the inverter 7 where the efficiency η 2(n +1) is greater than the lower limit value η L and [ η 2(n +1) = η L ] of the inverter 7 where the efficiency η 2(n +1) is the same as the lower limit value η L, and returns to step S1.

Further, when the output power target value PT increases, [ PT (n +1) > PTn ], the power distribution control unit 42 inverts the polarity of the power distribution correction amount Δ Rn before update to generate the updated power distribution correction amount Δ R and returns to step S1 when [ η 2(n +1) > η L ] where the efficiency η 2(n +1) of the inverter 7 is greater than the lower limit value η L and [ η 2(n +1) > η L ] where the efficiency η 2(n +1) of the inverter 7 is equal to the lower limit value η L.

Further, when the efficiency η 2(n +1) of the inverter 7 is smaller than the lower limit value η L [ η 2(n +1) < η L ], the power distribution control unit 42 reverses the polarity of the pre-update power distribution correction amount Δ Rn to generate the post-update power distribution correction amount Δ R regardless of the output power target value PT, and returns to step S1.

By repeatedly executing steps S1 to S6A, the reference electric powers P1R and P2R can be generated so that the loss PL1 of the inverter 4 is minimized and the efficiency η 1 of the inverter 4 is maximized within the range in which the efficiency η 2 of the inverter 7 is equal to or greater than the lower limit value η L. Other structures and operations are the same as those in embodiment 1, and therefore, description thereof will not be repeated.

In embodiment 3, the power distribution control of inverter 7 can be performed so that efficiency η 1 of inverter 4 is maximized without using the operation information of inverter 4.

Comparative example 1.

FIG. 13 is a block diagram showing comparative example 1 of embodiments 1 to 3. In fig. 13, the load is divided into a plurality of (3 in this example) groups of different types. The loads a1, … … of group a are both connected to the distribution line L1. The load a1 includes: a DC/AC converter 51 that converts a direct-current voltage VA supplied via a distribution line L1 into an alternating-current voltage; and a main body 52 driven by an alternating voltage supplied from the DC/AC converter 51.

The loads B1, … … of group B are both connected to the distribution line L2. The load B1 includes: a DC/DC converter 53 that converts the DC voltage VB supplied via the distribution line L2 into a constant DC voltage; and a main body 54 driven by the direct-current voltage supplied from the DC/DC converter 53. The loads C1, … … of group C are both connected to the distribution line L3. The load C1 includes a main body 55, and the main body 55 is driven by a dc voltage VC supplied via a distribution line L3.

The ac power receiving apparatus 50 supplies the ac voltage supplied from the commercial ac power supply 10 to the converter 4 after, for example, stepping down the ac voltage. The converter 4 includes: an AC/DC converter 15 that converts an alternating-current voltage supplied from the alternating-current power receiving apparatus 50 into a direct-current voltage; and a DC/DC converter 17 that converts the DC voltage supplied from the AC/DC converter 15 into 3 DC voltages VA, VB, and VC, and supplies the converted voltages to the power distribution lines L1 to L3, respectively.

A plurality of sets (2 sets in this example) of inverters 7 and power generation and storage sources 11 are coupled to the distribution lines L1 to L3. The inverter 7 includes: a DC/DC converter 26 that converts the DC voltage supplied from the power generation and storage source 11 into a constant DC voltage; and a chopper Circuit (CP)28 that distributes the DC power supplied from the DC/DC converter 26 to the 3 distribution lines L1 to L3.

In comparative example 1, the efficiency of inverters 4 and 7 is not taken into consideration, and dc voltages VA, VB, and VC are maintained at constant values regardless of the states of loads a1, B1, C1, and … …, respectively, and therefore the efficiency of the entire system is lower than in embodiments 1 to 3.

Comparative example 2.

FIG. 14 is a block diagram showing another comparative example 2 of embodiments 1 to 3. In fig. 14, all the loads a1, B1, C1, … … in the dc power supply and distribution system are connected to 1 distribution line L4. The AC power receiving apparatus 50 supplies the AC voltage supplied from the commercial AC power supply 10 to the AC/DC converter 60 after stepping down the AC voltage, for example. AC/DC converter 60 converts the AC voltage supplied from AC power receiving equipment 50 into DC voltage VD and supplies the DC voltage VD to power distribution line L4.

A plurality of sets (2 sets in this example) of the DC/DC converters 61 and the power generation and storage source 11 are combined to the distribution line L4. Each DC/DC converter 61 converts the DC voltage supplied from the corresponding power generation and storage source 11 into a DC voltage VD and supplies the DC voltage VD to the power distribution line L4.

In comparative example 2, the efficiency of inverters 60 and 61 is not considered, and dc voltage VD is maintained at a constant value regardless of the states of loads a1, B1, C1, and … …, and therefore the efficiency of the entire system is reduced as compared with embodiments 1 to 3.

Comparative example 3.

FIG. 15 is a block diagram showing still another comparative example 3 of embodiments 1 to 3. In fig. 15, all the loads X1, Y1, Z1, … … in the ac power supply and distribution system are connected to 1 distribution line L5.

The load X1 includes: an AC/DC converter 71 that converts an alternating-current voltage VAC supplied via a distribution line L5 into a direct-current voltage; a DC/AC converter 51 that converts the DC voltage supplied from the AC/DC converter 71 into an AC voltage; and a main body 52 driven by an alternating voltage supplied from the DC/AC converter 51.

The load Y1 includes: an AC/DC converter 72 that converts an alternating-current voltage VAC supplied via a distribution line L5 into a direct-current voltage; a DC/DC converter 53 that converts the DC voltage supplied from the AC/DC converter 72 into a constant DC voltage; and a main body 54 driven by the direct-current voltage supplied from the DC/DC converter 53. The load C1 includes: an AC/DC converter 73 that converts an alternating-current voltage VAC supplied via a distribution line L5 into a direct-current voltage; and a main body 55 driven by a direct-current voltage supplied from an AC/DC converter 73.

The ac power receiving apparatus 50 supplies the ac voltage supplied from the commercial ac power supply 10 to the distribution line L5 after, for example, stepping down the ac voltage. To the distribution line L5, a plurality of sets (2 sets in this example) of inverters 75 and a power generation and storage source 11 are incorporated. The inverter 75 includes: a DC/DC converter 76 that converts the DC voltage supplied from the power generation and storage source 11 into a constant DC voltage; and a DC/AC converter 77 that converts the DC power supplied from the DC/DC converter 76 into an AC voltage VAC and supplies the AC voltage VAC to the distribution line L5.

In comparative example 3, the efficiency of inverter 75 is not taken into consideration, and ac voltage VAC is maintained at a constant value regardless of the states of loads X1, Y1, Z1, and … …, and therefore the efficiency of the entire system is lower than in embodiments 1 to 3.

FIG. 16 is a graph comparing the number of stages of inverters in comparative examples 1 to 3. In fig. 16, the main power path is a path through which power is supplied from the commercial ac power supply 10 to the main body 52 of the load. The sub-electric power path is a path for supplying electric power from the power generation and storage source 11 to the main body 52 of the load. Here, the loss is increased in proportion to the number of stages of the converter. In addition, the chopper circuit 28 is treated as a converter.

In comparative example 1, the inverters 15, 17, and 51 of 3 stages are provided in the main power path, and the inverters 26, 28, and 51 of 3 stages are provided in the sub power path. In comparative example 2, the inverters 60 and 51 of 2 stages are provided in the main power path, and the inverters 61 and 51 of 2 stages are provided in the sub power path. In comparative example 3, the inverters 71, 51 of 2 stages are provided in the main power path, and the inverters 76, 77, 71, 51 of 4 stages are provided in the sub power path.

In comparative example 3, the number of stages of the converter in the main power path is 2 and small, but the number of stages of the converter in the sub power path is as many as 4, and therefore, when the power generation and storage source 11 such as a solar cell is actively used, there is a problem that a loss in the converter becomes large.

In comparative example 2, the number of stages of the inverter in the main power path is 2, which is equal to comparative example 3, and the number of stages of the inverter in the sub power path is 2, which is 2 fewer stages than comparative example 3. Therefore, when the power generation and storage source 11 is actively used, it can be said that the configuration is advantageous in terms of efficiency. However, since the AC/DC converter is not included in the load, when the types of loads are mixed, the optimal DC voltage of the DC/AC converter 51 included in the load may be different for each load. Therefore, a dc voltage optimal for each load cannot be supplied, and there is a possibility that the load efficiency is lowered.

In comparative example 1, the load is divided into a plurality of groups, a plurality of distribution lines are provided corresponding to the plurality of load groups, and a dc voltage is supplied to each of the load groups, so that the problem of comparative example 2 in which the load efficiency is lowered can be solved.

In comparative example 1, the number of stages of the inverter in the main power path is 3, 1 stage is added to comparative example 3, and the number of stages of the inverter in the sub-power path is 3, and 1 stage is reduced to comparative example 3. Therefore, in comparison with comparative example 3, comparative example 1 has a configuration that is disadvantageous in terms of efficiency in power transmission from the commercial ac power supply 10 to the load and is advantageous in terms of efficiency in power transmission from the power generation and storage source 11 to the load with respect to the number of stages of the converter.

Therefore, in comparative example 1, an object is to eliminate a decrease in efficiency caused by an increase in the number of stages of the converter in the main power path. In embodiments 1 to 3, the output power of the converter 7 is controlled so that the efficiency η of the converters 4 and 7 is maximized, thereby suppressing the decrease in efficiency caused by the increase in the number of stages of the converter, and the problem of comparative example 1 is solved.

It should be understood that the embodiments disclosed herein are illustrative only and not restrictive in all respects. The present invention is not defined by the above description but is defined by the claims, and is intended to include all modifications within the scope and meaning equivalent to the claims.