阅读说明：本技术 电源装置 (Power supply device ) 是由 田边义清 渡边胜广 于 2019-12-16 设计创作，主要内容包括：本公开的课题在于提供如下电源装置：能够不使用变压器地进行变压,且能够输出任意频率的交流。电源装置(1)具备：正转换电路(2),其具有多个正转换开关元件,用于从三相交流的一次电源针对各相相独立地分别取出正的电压和负的电压；平滑电路(3),其具有利用正转换电路(2)被进行充电的相互串联连接的一对平滑电容器以及分别配设在正转换电路(2)与平滑电容器之间的多个平滑电感器；逆转换电路(4),其具有多个逆转换开关元件,用于将平滑电路(3)的输出逆转换为交流；以及控制电路(5),其控制多个正转换开关元件的开关,使得平滑电路(3)的输出电压为期望的电压且流过正转换电路(2)的各相的电流为期望的电流。(The subject of the present disclosure is to provide a power supply device: the transformer can transform without using a transformer, and can output alternating current of any frequency. A power supply device (1) is provided with: a positive conversion circuit (2) having a plurality of positive conversion switching elements for taking out a positive voltage and a negative voltage from a three-phase alternating-current primary power supply for each phase independently; a smoothing circuit (3) having a pair of smoothing capacitors connected in series to each other and charged by the positive conversion circuit (2), and a plurality of smoothing inductors respectively disposed between the positive conversion circuit (2) and the smoothing capacitors; a reverse conversion circuit (4) having a plurality of reverse conversion switching elements for reverse-converting the output of the smoothing circuit (3) into an alternating current; and a control circuit (5) that controls the switching of the plurality of positive conversion switching elements so that the output voltage of the smoothing circuit (3) is a desired voltage and the current flowing through each phase of the positive conversion circuit (2) is a desired current.)

1. A power supply device is provided with:

a positive conversion circuit having a plurality of positive conversion switching elements for taking out a positive voltage and a negative voltage from a primary power supply of a three-phase alternating current for each phase independently;

a smoothing circuit having a pair of smoothing capacitors connected in series to each other and charged by the positive converter circuit, and a plurality of smoothing inductors respectively disposed between the positive converter circuit and the smoothing capacitors;

a reverse conversion circuit having a plurality of reverse conversion switching elements for reverse-converting an output of the smoothing circuit into an alternating current; and

and a control circuit that controls switching of the plurality of positive changeover switching elements such that an output voltage of the smoothing circuit becomes a desired voltage and a current flowing through each phase of the positive changeover circuit becomes a desired current.

2. The power supply device according to claim 1,

the smoothing inductors are respectively disposed between the positive output of each phase of the positive conversion circuit and the smoothing capacitor and between the negative output of each phase of the positive conversion circuit and the smoothing capacitor.

3. The power supply device according to claim 1 or 2,

the control circuit controls the current flowing through each phase of the positive conversion circuit so that the potential at the midpoint of the pair of smoothing capacitors becomes a predetermined potential or a potential within a predetermined range.

4. The power supply device according to any one of claims 1 to 3,

the control circuit controls the current flowing through each phase of the positive conversion circuit so as to increase the power factor of each phase of the positive conversion circuit or suppress the peak current.

5. The power supply device according to any one of claims 1 to 4,

the positive conversion circuit further includes a plurality of regenerative switching elements, each of which is provided so as to correspond to the positive conversion switching element and is capable of flowing a current in a reverse direction,

the smoothing circuit further includes a plurality of boost switching elements each connecting a position on the forward conversion circuit side of the smoothing inductor and a midpoint between the pair of smoothing capacitors,

the reverse conversion circuit is configured to be capable of converting an alternating-current voltage supplied from an output side into a direct-current voltage,

the control circuit controls the boost switching element so that a voltage supplied from the smoothing circuit to the forward conversion circuit becomes equal to a peak value of a voltage of the primary power supply, and controls the regenerative switching element so that a voltage synchronized with the primary power supply is extracted from the voltage of the smoothing circuit and supplied to the primary power supply.

6. The power supply device according to any one of claims 1 to 5,

the device further includes an insulation deterioration detection circuit that grounds an intermediate point of the pair of smoothing capacitors via a detection switch and a detection resistor.

Technical Field

The present invention relates to a power supply device.

Background

Conventionally, devices (industrial machines) using motors driven by an ac power supply have been widely used for industrial purposes. The voltage of the ac power source available to the user, that is, the voltage of the internal power distribution system, sometimes differs depending on the user. Generally, although internal distribution is performed by three-phase AC of AC200V in japan, there are many cases where distribution systems of about AC380V to AC480V are used in other countries. In addition, there are also the following cases: even in the same country, the voltage of the internal power distribution system differs depending on the structure of the power receiving apparatus.

For example, in industrial robots and the like, there are various sizes, the number of axes, and system configurations, and there are various power supply voltages available to users, and therefore it is not easy to change the design of the device in accordance with individual voltages. In addition, when the design of the device is changed for each voltage, there is a problem that maintenance becomes complicated. Therefore, when the voltage of the power supply available to the user is different from the voltage of the existing device, a transformer is often provided between the power supply and the device to cope with the difference. However, when a transformer is utilized, the size and weight of the apparatus increase, and the cost increases.

In industrial robots and the like, a power supply device that converts ac into dc and then converts the dc back into ac of a desired frequency is sometimes used to drive a servo motor, as described in patent document 1, for example. In this case, it is conceivable that the output voltage optimum for the motor can be obtained regardless of the power supply voltage by transforming the direct current. That is, if a chopper circuit is added to the dc portion of the power supply device described in patent document 1, the voltage of the output ac can be adjusted.

Disclosure of Invention

Problems to be solved by the invention

An alternating-current power supply capable of controlling a motor for AC200V can be obtained by converting the voltage of AC380V to AC480V power supplies, which are commonly used abroad and have a neutral point grounded, by a chopper circuit. In this case, when the three-phase alternating current is converted again by the reverse conversion circuit, the neutral point of the three-phase alternating current power supply that causes the output becomes a potential different from the ground potential.

When the difference between the neutral point of the output ac and the ground potential is large, a load circuit such as a servo motor needs a high insulation breakdown voltage with respect to the ground, and the insulation breakdown voltage may be insufficient and may not be used. When the difference between the neutral point potential and the ground potential is large, switching noise increases, and the risk of malfunction increases.

In addition, in a power supply device for driving a servo motor, since a current flows into a capacitor having a large capacity, a large peak current including harmonics flows when the servo motor is accelerated, and a large capacity of a device power supply is required. As a countermeasure, a method of improving the power factor and suppressing the peak current has been developed, but these methods cannot be easily applied because they require high cost and large size.

Accordingly, an object of the present invention is to provide a power supply device including: the transformer can transform without using a transformer, and can output alternating current of any frequency.

Means for solving the problems

(1) The power supply device (for example, power supply devices 1, 1a, 1b, and 1C described below) according to the present invention includes a positive converter circuit (for example, positive converter circuits 2 and 2a described below) having a plurality of positive converter switching elements (for example, positive converter switching elements T11, T12, T13, T14, T15, and T16 described below) for independently extracting a positive voltage and a negative voltage from a primary power supply for three-phase alternating current for each phase, a smoothing circuit (for example, smoothing circuits 3, 3a, 3b, and 3C described below) having a pair of smoothing capacitors (for example, smoothing capacitors C1 and C2 described below) connected in series to each other and charged by the positive converter circuit, and a plurality of smoothing inductors (for example, smoothing inductors L, L, 6863, L, L, 366, L, and 378) disposed between the positive converter circuit and the smoothing capacitors, respectively (for example, smoothing inductors 635, 3b, and 3C) for controlling the reverse converter circuits (for example, 465) to flow of a desired voltage, 465) for each phase, and a desired converter circuit (for example, 465) and for controlling the reverse converter circuit to output a desired voltage.

(2) In the power supply device of (1), the smoothing inductors may be disposed between the positive output of each phase of the positive converter circuit and the smoothing capacitor, and between the negative output of each phase of the positive converter circuit and the smoothing capacitor, respectively.

(3) In the power supply device of (1) or (2), the current flowing through the positive conversion circuit may be controlled so that the potential at the midpoint between the pair of smoothing capacitors becomes a predetermined potential (for example, ground potential) or a potential within a predetermined range.

(4) In the power supply devices of (1) to (3), the current flowing through each phase of the positive converter circuit may be controlled so as to increase the power factor of each phase of the positive converter circuit or suppress the peak current.

(5) In the power supply devices of (1) to (4), the forward converter circuit may further include a plurality of regenerative switching elements (e.g., regenerative switching elements T31, T32, T33, T34, T35, and T36 described later), each of the plurality of regenerative switching elements being provided so as to correspond to the forward converter element and being capable of flowing a current in a reverse direction, the smoothing circuit may further include a plurality of boost switching elements (e.g., boost switching elements T41, T42, T43, T44, T45, and T46 described later), the plurality of boost switching elements being respectively disposed between a position on the forward conversion circuit side of the smoothing inductor and an intermediate point between the pair of smoothing capacitors, the reverse converter circuit may be configured to be capable of converting an ac voltage supplied from an output side into a dc voltage, and the control circuit may control the boost switching elements, the voltage supplied from the smoothing circuit to the positive conversion circuit is made equal to the peak value of the voltage of the primary power supply, and the control circuit controls the regenerative switching element so that a voltage synchronized with the primary power supply is extracted from the voltage of the smoothing circuit and supplied to the primary power supply.

(6) The power supply devices (1) to (5) may further include a detection circuit (e.g., an insulation deterioration detection circuit 6 described later) that grounds an intermediate point of the pair of smoothing capacitors via a detection switch and a detection resistor.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, the following power supply device can be provided: the transformer can transform without using a transformer, and can output alternating current of any frequency.

Drawings

Fig. 1 is a circuit diagram showing a configuration of a power supply device according to an embodiment of the present invention.

Fig. 2 is a timing chart showing an operation pattern of the positive changeover switching element in the power supply device of fig. 1.

Fig. 3 is a circuit diagram showing a configuration of a power supply device according to an embodiment of the present invention different from that of fig. 1.

Fig. 4 is a circuit diagram showing a configuration of a power supply device according to an embodiment of the present invention different from that of fig. 1 and 3.

Fig. 5 is a circuit diagram showing a configuration of a power supply device according to an embodiment of the present invention different from those shown in fig. 1, 3, and 4.

Description of the reference numerals

1. 1a, 1b, 1C, a power supply device, 2a, a positive conversion circuit, 3a, 3b, 3C, a smoothing circuit, 4 a reverse conversion circuit, 5a, 5b, 5C, a control circuit, 6 an insulation degradation detection circuit, C1, C2, a smoothing capacitor, Cg, a grounding capacitor, L1, L2, L3, L4, L5, L6, L7, L8, a smoothing inductor, S, a primary power supply, T11, T12, T13, T14, T15, T16, a positive conversion switching element, T21, T22, T23, T24, T25, T26, a reverse conversion switching element, T31, T32, T33, T34, T35, T36, a regenerative switching element, T41, T42, T43, T44, a boost switching element, T44, a regenerative switching element.

Detailed Description

Embodiments of the present invention will be described below with reference to the drawings.

Fig. 1 is a circuit diagram showing a configuration of a power supply device 1 according to an embodiment of the present invention.

The power supply device 1 is a device that converts three-phase ac power supplied from a primary power supply (ac power supply) S into three-phase ac power having different voltages and frequencies and supplies the three-phase ac power to a load (in the present embodiment, a motor M). More specifically, the power supply device 1 is connected to a primary power supply S having a voltage equal to or higher than the rated voltage of the motor M and having a neutral point grounded, and converts a three-phase ac of the primary power supply S into a three-phase ac having a voltage equal to the rated voltage of the motor M and a frequency equal to the frequency of an external device or a frequency set by a user, and supplies the three-phase ac to the motor M.

The power supply device 1 includes: a positive conversion circuit 2 for taking out a positive voltage and a negative voltage from the primary power supply for each phase independently; a smoothing circuit 3 that obtains a stable direct current by smoothing the current supplied from the positive conversion circuit 2; a reverse conversion circuit 4 that outputs an alternating current of a desired frequency by reversely converting the output of the smoothing circuit 3 into an alternating current; and a control circuit 5 that controls the positive conversion circuit 2 and the negative conversion circuit 4.

The positive conversion circuit 2 has a plurality of positive conversion switching elements (a positive conversion switching element T11 for taking out a positive voltage of the 1 st phase, a positive conversion switching element T12 for taking out a positive voltage of the 2 nd phase, a positive conversion switching element T13 for taking out a positive voltage of the 3 rd phase, a positive conversion switching element T14 for taking out a negative voltage of the 1 st phase, a positive conversion switching element T15 for taking out a negative voltage of the 2 nd phase, and a positive conversion switching element T16 for taking out a negative voltage of the 3 rd phase).

The positive changeover switching elements T11, T12, T13, T14, T15, and T16 are, for example, semiconductor switching elements such as illustrated FETs, and their on/off states are controlled by a control circuit 5 described later.

The smoothing circuit 3 includes a pair of smoothing capacitors (a smoothing capacitor C1 charged with a positive voltage and a smoothing capacitor C2 charged with a negative voltage) having the same capacitance and connected in series with each other and charged by the positive switching circuit 2, a grounding capacitor Cg grounding an intermediate point of the pair of smoothing capacitors, a plurality of smoothing inductors (a smoothing inductor L1 to which a positive voltage of the 1 st phase is applied, a smoothing inductor L2 to which a positive voltage of the 2 nd phase is applied, a smoothing inductor L03 to which a positive voltage of the 3 rd phase is applied, a smoothing inductor L14 to which a negative voltage of the 1 st phase is applied, a smoothing inductor L to which a negative voltage of the 2 nd phase is applied, and a smoothing inductor L to which a negative voltage of the 3 rd phase is applied, a smoothing inductor 465 to which a negative voltage of the 2 nd phase is applied, and a smoothing inductor 365 to which a negative voltage of the 3 rd phase is applied, a smoothing inductor 465 to which a negative voltage of the 2 nd phase is applied, and a smoothing inductor L to which a negative voltage of the reverse flow preventing diode is applied, a smoothing inductor 865 connected with an intermediate point of the pair of the smoothing capacitors (a positive switching diode C diodes 3 nd phase switching circuit 2 to which a positive switching diode added, a negative diode added, 363 connected with a positive diode added, a negative diode 363 rd phase diode added, a negative diode added, 363 connected with a negative diode 363, a negative diode added, a negative diode 367 connected with a negative diode added, 363, a reverse flow preventing diode added, a reverse current, a negative diode 363 connected with a reverse current, a reverse current-added, a reverse current-preventing diode 2 connected between the circuit connected between the positive switching diode 363, a positive diode 2 connected between the positive switching circuit connected between the positive diode added, a positive diode 363 connected with a reverse current-added, a reverse-connected between a reverse-added diode 2 connected between the positive diode 363-added-connected between the positive diode 363.

The smoothing capacitors C1 and C2 are charged with a current supplied through the smoothing inductors L1, L2, L3, L4, L5, and L6, show a dc voltage corresponding to the charge amount, and supply a current to the reverse conversion circuit 4 by discharging, thereby stabilizing the output voltage.

Here, the positive output terminal of the smoothing circuit 3 to the reverse conversion circuit 4 (the positive side of the smoothing capacitor C1 on the positive side) is set to a point P1, the negative output terminal of the smoothing circuit 3 to the reverse conversion circuit 4 (the negative side of the smoothing capacitor C2 on the negative side) is set to a point P2, and the midpoint between the smoothing capacitors C1 and C2 is set to a point P0.

A difference in voltage is generated by a current flowing through the grounding capacitor Cg, which is a difference between a current flowing through the smoothing capacitor C1 and a current flowing through the smoothing capacitor C2. When the potential of the intermediate point P0 between the smoothing capacitors C1 and C2 is deviated for some reason, the difference between the intermediate point P0 and the ground potential can be reduced by the current difference between the positive side smoothing capacitor C1 and the negative side smoothing capacitor C2. Since the capacitance of the grounding capacitor Cg is smaller than the capacitances of the smoothing capacitors C1 and C2, the potential of the intermediate point P0 can be controlled at the same time while controlling the potentials (output voltages) of the points P1 and P2.

Smoothing inductors L1, L2, L03, L14, L5, L6 are used to mitigate voltage variations caused by the turning on and off of corresponding positive changeover switching elements T11, T12, T13, T14, T15, T16. smoothing inductors L1, L2, L3, L4, L5, L6 may be constituted by one coil, or by a plurality of coils connected in series, in parallel, or both.

The flywheel diodes Dr1, Dr2, Dr3, Dr4, Dr5, and Dr6 form a closed circuit so that current can flow to the smoothing inductors L1, L2, L3, L4, L5, and L6 in a state where the positive changeover switching elements T11, T12, T13, T14, T15, and T16 are turned off.

The backflow prevention diodes Dc1, Dc2, Dc3, Dc4, Dc5, and Dc6 are used to prevent a reverse voltage from being applied to the positive conversion switching elements T11, T12, T13, T14, T15, and T16 when the positive conversion switching elements T11, T12, T13, T14, T15, and T16 are turned off, and to protect the positive conversion switching elements T11, T12, T13, T14, T15, and T16 (particularly, prevent the parasitic diodes thereof from being broken by an excessive current flowing therethrough).

The reverse conversion circuit 4 has a plurality of reverse conversion switching elements (a switching element T21 for outputting a positive voltage of the 1 st phase, a switching element T22 for outputting a positive voltage of the 2 nd phase, a switching element T23 for outputting a positive voltage of the 3 rd phase, a switching element T24 for outputting a negative voltage of the 1 st phase, a switching element T25 for outputting a negative voltage of the 2 nd phase, and a switching element T26 for outputting a negative voltage of the 3 rd phase).

The reverse changeover switching elements T21, T22, T23, T24, T25, and T26 may be semiconductor switching elements such as FETs.

The control circuit 5 may have a microprocessor configuration. The control circuit 5 acquires information necessary for controlling the forward converter circuit 2 and the reverse converter circuit 4 from the primary power supply monitor a1, the forward converter circuit current monitor a2, the DC link voltage monitor A3, and the virtual neutral point voltage monitor a 4. Note that, for simplification, the circuit configuration of the control circuit 5 and the monitors a1 to a4 is not shown in fig. 1, and the forward converting circuit 2, the smoothing circuit 3, and the reverse converting circuit 4 required for control, and signal lines between the monitors a1 to a4 and the control circuit 5, for example, signal lines for controlling the forward converting switching elements T11, T12, T13, T14, T15, T16, and the reverse converting switching elements T21, T22, T23, T24, T25, and T26, are collectively shown as a single line having an arrow between the forward converting circuit 2, the smoothing circuit 3, and the reverse converting circuit 4, and the control circuit 5.

The control circuit 5 controls the switching of the positive changeover switching elements T11, T12, T13, T14, T15, and T16 such that the output voltage of the smoothing circuit 3 (the voltage between the point P1 and the point P2) is 2 times the peak value of the desired voltage, that is, the required output voltage of the power supply apparatus 1 (the output voltage of the reverse changeover circuit 4). The output voltage of the smoothing circuit 3 can be adjusted by PWM (Pulse width modulation) control in which the positive changeover switching elements T11, T12, T13, T14, T15, and T16 are turned on and off in a short period and the length of the on time is controlled.

Meanwhile, the control circuit 5 individually controls the switching of the positive changeover switching elements T11, T12, T13, T14, T15, and T16 so that the current flowing through each phase of the positive changeover circuit becomes a desired current.

The control circuit 5 adjusts the switches of the positive changeover switching elements T11, T12, T13, T14, T15, and T16 so that the potential at the midpoint P0 of the smoothing capacitors C1 and C2 becomes equal to a predetermined potential or a potential within a predetermined range, for example, a ground potential. The electric potential at the intermediate point P0 between the smoothing capacitors C1 and C2 is made substantially equal to the ground electric potential by equalizing the electric currents flowing through the positive changeover switching elements T11, T12, and T13 on the positive side and the electric currents flowing through the positive changeover switching elements T14, T15, and T16 on the negative side. However, the potential of the intermediate point P0 is not necessarily the ground potential due to variations in the input voltage, variations in the operation of the positive changeover switching elements T11, T12, T13, T14, T15, and T16, a leakage current flowing to the ground due to the parasitic capacitance of the load circuit (motor M), and the like. When the voltage of the primary power source S is reduced or in a phase in which the voltage is reduced, if the input voltage is equal to or lower than the voltage of the smoothing capacitors C1 and C2, no current flows through the smoothing circuit 3, which causes the neutral point potential of the three-phase alternating current output to the motor M to deviate from the ground potential. In this case, the potential of the intermediate point P0 between the smoothing capacitors C1 and C2 can be adjusted by providing a difference between the time length for which the positive changeover switching elements T11, T12, and T13 on the positive side are turned on and the time length for which the positive changeover switching elements T14, T15, and T16 on the negative side are turned on, thereby providing a difference between the current flowing through the smoothing capacitor C1 and the current flowing through the smoothing capacitor C2.

Fig. 2 shows operation patterns of the positive changeover switching elements T11, T12, T13, T14, T15, and T16 in the power supply device 1. Fig. 2 (a) shows voltage waveforms of the phases of the primary power source S and positive and negative output potentials of the power source device 1, that is, a potential E1 at a point P1 and a potential E2 at a point P2.

Fig. 2 (B) shows periods (hereinafter, may be referred to as PWM control periods) in which the voltages of the respective phases can be extracted from the primary power source S for the positive changeover switching elements T11, T12, T13, T14, T15, and T16. When the absolute value of the voltage of each phase is equal to or greater than the absolute value of the potential E1 at the point P1 or the potential E2 at the point P2, the positive changeover switching elements T11, T12, T13, T14, T15, and T16 are turned on, and the voltage of each phase can be extracted. On the contrary, the control circuit 5 does not turn on the positive changeover switching elements T11, T12, T13, T14, T15, and T16 in the periods other than the period shown in fig. 2 (B).

By PWM control in which the positive changeover switching elements T11, T12, T13, T14, T15, and T16 are turned on and off at short cycles and the on time is adjusted in the period shown in fig. 2 (B), the current supplied to the smoothing capacitors C1 and C2 is adjusted, and the potential E1 at the point P1 and the potential E2 at the point P2, which are proportional to the charge amounts of the smoothing capacitors C1 and C2, are maintained at desired values. As a specific example, fig. 2 (C) shows an example of PWM control of the positive changeover switching element T12 of the 2 nd phase. Preferably, when the phase voltage of the primary power source S is high, the time (pulse width) for turning on the positive changeover switching element T12 is short. As a result, as shown in fig. 2D, the current flowing through the positive changeover switching element T12 (corresponding phase of the positive changeover circuit 2) when the phase voltage of the primary power source S is high can be suppressed, and the variation in the current value (I12) during the PWM control period can be reduced. Further, by increasing or decreasing the total of the time during which the positive changeover switching element T12 is turned on in the PWM control period, the peak value of the current can be adjusted as indicated by the broken line in fig. 2 (D).

In this case, in order to suppress a decrease in power factor, it is preferable to control the on time of the positive changeover switching elements T11, T12, T13, T14, T15, and T16 so that the current of the primary power supply flows in proportion to the voltage of the primary power supply as much as possible. When the output voltage (the potential difference between the point P1 and the point P2) of the power supply apparatus 1 is higher than the input voltage, the smoothing capacitors C1 and C2 cannot be charged, and therefore the PWM control is stopped (the positive changeover switching elements T11, T12, T13, T14, T15, and T16 are not turned on). The same occurs when the voltage of the primary power source S is lower than the output voltage of the power supply device 1. When the PWM control stop period is long, the power factor deteriorates. In order to improve this, when the inter-phase voltage of the primary power source S is greater than the output voltage (the potential difference between the point P1 and the point P2) instead of the inter-phase voltage of the primary power source S being greater than the output voltage, the PWM control period can be extended by allowing the neutral point potential to fluctuate. In this case, the PWM control period is extended under the condition that the variation of the neutral point potential is limited to a certain degree, and the power factor improvement and the peak current suppression can be further improved.

That is, there is a trade-off between the PWM control period and the range of variation of the neutral point potential, and not only the neutral point potential is fixed to the ground potential but also variation of the neutral point potential is allowed to some extent, whereby optimum control according to the purpose can be performed. The larger the difference between the voltage of the primary power source S and the output voltage is, the more the controllability can be improved. For example, when the voltage of the primary power source S is AC380V to AC480V and the rated voltage of the motor is AC200V, there is a voltage difference of about 2 times between the primary power source voltage and the output voltage, and thus there is an advantage that the PWM control period is extended and the controllability can be improved.

Further, since the smoothing circuit 3 includes the smoothing inductors L1, L2, L3, L4, L5, and L6, the current for charging the smoothing capacitors C1 and C2 is limited with respect to the voltage applied for a short time by the positive-conversion switching elements T11, T12, T13, T14, T15, and T16, respectively, and the output voltage of the smoothing circuit 3 can be stabilized.

Further, since the smoothing circuit 3 includes the flywheel diodes Dr1, Dr2, Dr3, Dr4, Dr5, and Dr6, it is possible to continue flowing current to the smoothing inductors L1, L2, L3, L4, L5, and L6 even after the positive changeover switching elements T11, T12, T13, T14, T15, and T16 are turned off, and thus unnecessary surge voltage can be suppressed, and the output voltage of the smoothing circuit 3 can be further stabilized.

In the adjustment of the potential at the intermediate point P0 between the smoothing capacitors C1 and C2, the on-time ratio of the PWM control of the positive changeover switching elements T11, T12 and T13 on the positive side and the positive changeover switching elements T14, T15 and T16 on the negative side may be decreased or increased, or one may be decreased and the other may be increased. Since the smoothing capacitors C1 and C2 use large-capacity capacitors and the grounding capacitor Cg uses a small-capacity capacitor, the difference between the current flowing through the positive changeover switching elements T11, T12, and T13 and the current flowing through the positive changeover switching elements T14, T15, and T16 is very small compared with the total current, and there is little influence of the increase or decrease in the output voltage of the smoothing circuit 3 due to the control of the neutral point potential.

As described above, the power supply device 1 can transform without using a transformer, and can output ac of any frequency by setting the potential of the neutral point to a predetermined voltage.

More specifically, according to the power supply apparatus 1, the on-time ratio of the PWM control is controlled for the positive changeover switching elements T11, T12, T13, T14, T15, and T16, whereby the output voltage of the smoothing circuit 3 and, in turn, the output voltage of the reverse changeover circuit 4 can be adjusted. When the outputs of the phases of the positive converter circuit 2 are not independent, current flows only to the phase having the largest phase voltage, and the PWM control period is shortened, thereby reducing the power factor. The power supply device 1 compares the phase voltage of each phase with the output voltage, and performs PWM control when the phase voltage is high, whereby a current can flow even in a phase having a relatively low phase voltage. As a result, the PWM control period of each phase can be extended, and thus the power factor can be improved and the peak current can be suppressed. When the output current to the reverse converter circuit increases and the output voltage of the forward converter circuit 2 decreases, the PWM control period becomes longer, and the power factor is further improved. When the output current to the inverter decreases and the output voltage of the forward converter circuit 2 increases, the PWM control period is shortened, but the output current decreases, and the influence of the decrease in the power factor decreases. In this way, the PWM control period can be extended as much as possible for each phase, and the current of the positive conversion circuit 2 can be brought closer to an ideal state.

Further, since the smoothing circuit 3 includes the pair of smoothing capacitors C1 and C2 connected in series, the potential at the midpoint P0 between the pair of smoothing capacitors C1 and C2 varies depending on the difference in voltage for charging the pair of smoothing capacitors C1 and C2. Therefore, the positive changeover switching elements T11, T12, T13, T14, T15, and T16 are controlled by the control circuit 5 so that the potential of the intermediate point P0 between the pair of smoothing capacitors C1 and C2 is equal to a predetermined potential, for example, the ground potential, whereby the positive and negative output voltages of the smoothing circuit 3 are equal to each other. Thus, the reverse converter circuit 4 maintains the potential of the neutral point of the output voltage obtained by converting the output voltage of the smoothing circuit into the ac voltage at a potential equal to the ground potential. Therefore, the power supply device 1 according to the present invention can transform without using a transformer, and can output an alternating current of an arbitrary frequency by setting the potential of the neutral point to a predetermined voltage.

The control circuit 5 controls the current flowing through each phase of the converter circuit 2 so as to stabilize the output voltage of the positive converter circuit 2, stabilize the neutral point potential, improve the power factor of each phase, or suppress the peak current. This reduces the ratio of the capacity, the insulation durability, and the like required for each component of the power supply apparatus 1, and can reduce the apparatus cost, reduce the risk of malfunction due to switching noise, and further reduce the apparatus power supply capacity.

The power supply device 1 adjusts the on-time ratio of the PWM control for switching the positive changeover switching elements T11, T12, T13, T14, T15, and T16 so that the charging currents of the pair of smoothing capacitors C1 and C2 are equal. This makes it possible to equalize the potentials of the pair of smoothing capacitors C1 and C2.

In the power supply device 1, the smoothing circuit includes a plurality of smoothing inductors L1, L2, L3, L4, L5, L6 respectively disposed between the positive and negative outputs of each phase of the positive converter circuit 2 and the smoothing capacitors C1, C2, and thus, the output voltage of the smoothing circuit 3 can be stabilized by suppressing the variation in the charging current of the smoothing capacitors C1, C2.

Fig. 3 is a circuit diagram showing a configuration of a power supply device 1a according to an embodiment of the present invention different from that of fig. 1. In the power supply device 1a of fig. 3, the same components as those of the power supply device 1 of fig. 1 are denoted by the same reference numerals, and redundant description thereof is omitted.

The power supply device 1a is a device that converts three-phase ac supplied from a primary power supply S into three-phase ac having different voltages and frequencies and supplies the three-phase ac to a motor M (power running). The power supply device 1a can perform a regenerative operation in which the electric power output from the electric motor M is converted into synchronous electric power having a voltage and a frequency equal to those of the primary power supply S and then supplied to the primary power supply S, using the electric motor M as a generator.

The power supply device 1a includes: a positive conversion circuit 2a that takes out a positive voltage and a negative voltage from the primary power supply for each phase independently; a smoothing circuit 3a that obtains a stable direct current by smoothing the current supplied from the positive conversion circuit 2 a; a reverse conversion circuit 4 that outputs an alternating current of a desired frequency by reversely converting the output of the smoothing circuit 3a into an alternating current; an insulation deterioration detection circuit 6 for detecting an abnormality of the motor M; and a control circuit 5a that controls the positive converter circuit 2a, the smoothing circuit 3a, the reverse converter circuit 4, and the insulation deterioration detection circuit 6. In fig. 3, various monitors for acquiring information necessary for the control circuit 5a to perform control are also omitted.

The positive conversion circuit 2a has: a plurality of positive changeover switching elements T11, T12, T13, T14, T15, T16; and a plurality of regenerative switching elements (a regenerative switching element T31 disposed in series with the positive changeover switching element T11, a regenerative switching element T32 disposed in series with the positive changeover switching element T12, a regenerative switching element T33 disposed in series with the positive changeover switching element T13, a regenerative switching element T34 disposed in series with the positive changeover switching element T14, a regenerative switching element T35 disposed in series with the positive changeover switching element T15, and a regenerative switching element T36 disposed in series with the positive changeover switching element T16) which are provided so as to correspond to the positive changeover switching elements T11, T12, T13, T14, T15, and T16 and which are capable of causing a current to flow in a reverse direction.

The regenerative switching elements T31, T32, T33, T34, T35, and T36 may be semiconductor switching elements.

In the present embodiment, the positive changeover switching elements T11, T12, T13, T14, T15, and T16 and the regenerative switching elements T31, T32, T33, T34, T35, and T36 are each configured by an FET having a parasitic diode that causes a current to flow in the reverse direction. Therefore, by connecting the positive changeover switching elements T11, T12, T13, T14, T15, and T16 in series with the regenerative switching elements T31, T32, T33, T34, T35, and T36, and turning on one of the positive changeover switching elements T11, T12, T13, T14, T15, T16 and the regenerative switching elements T31, T32, T33, T34, T35, and T36, it is possible to make the current flow in one direction. When a switching element having no parasitic diode is used, diodes may be provided in parallel with the positive changeover switching elements T11, T12, T13, T14, T15, T16 and the regenerative switching elements T31, T32, T33, T34, T35, T36, respectively, or the positive changeover switching elements T11, T12, T13, T14, T15, T16 may be connected in parallel with the regenerative switching elements T31, T32, T33, T34, T35, T36.

The smoothing circuit 3a includes a pair of smoothing capacitors (a smoothing capacitor C1 charged with a positive voltage and a smoothing capacitor C2 charged with a negative voltage) connected in series with each other and charged by a positive converter circuit 2a, a ground capacitor Cg grounding an intermediate point of the pair of smoothing capacitors, a plurality of smoothing inductors (a smoothing inductor L to which a positive voltage of the 1 st phase is applied, a smoothing inductor L to which a positive voltage of the 2 nd phase is applied, a smoothing inductor 68603 to which a positive voltage of the 3 rd phase is applied, a smoothing inductor L14 to which a negative voltage of the 1 st phase is applied, a smoothing inductor L to which a negative voltage of the 2 nd phase is applied, and a smoothing inductor L to which a negative voltage of the 3 rd phase is applied) arranged between positive and negative outputs of the positive and the smoothing capacitors of the positive converter circuit and the smoothing capacitors, a plurality of smoothing inductors are connected to the smoothing capacitor C5872 and the boost switch L, a smoothing inductor L connected to the boost switch C72, L, a smoothing inductor L, a boost switch L, a smoothing inductor L, a L connected to the boost switch L, a smoothing inductor L, a plurality of smoothing inductors 8672 and a smoothing inductor L connected to the boost switch L connected to the smoothing inductor L (L, L connected to the boost switch L, L connected to the smoothing inductor L, L connected to the smoothing inductor L, L connected to the boost switch L connected to the.

In the present embodiment, the boost switching elements T41, T42, T43, T44, T45, and T46 may be configured by semiconductor switching elements, and the boost switching elements T41, T42, T43, T44, T45, and T46 may be configured by FETs having parasitic diodes that function as free-wheeling diodes that can continue to flow current to the smoothing inductors L, L2, L, L, L, and L even after the positive transfer switching elements T11, T12, T13, T14, T15, and T16 are turned off.

The reverse conversion circuit 4 has a plurality of reverse conversion switching elements T21, T22, T23, T24, T25, and T26. The reverse conversion circuit is configured to be capable of converting an alternating-current voltage supplied from an output side into a direct-current voltage. Specifically, the reverse conversion switching elements T21, T22, T23, T24, T25, and T26 are configured by FETs having parasitic diodes, and thus ac supplied from the motor M can be converted into dc to charge the smoothing capacitors C1 and C2 of the smoothing circuit 3 a.

The insulation degradation detection circuit 6 includes a detection switch Sw and a detection resistor Rd connected in series, and is configured to ground an intermediate point P0 between a pair of smoothing capacitors C1 and C2 via the detection switch Sw and the detection resistor Rd.

Since the operation speed is not required for the detection switch Sw, the detection switch Sw may be configured by a relay or the like in addition to the semiconductor switching element, or may be configured by a switch which is operated by the operator.

The detection resistor Rd is a resistor which can detect that a current flows by generating a potential difference between both ends thereof when a current flows.

The control circuit 5a of the power supply apparatus 1a of fig. 3 can perform control for performing the regenerative operation as described below, in addition to control for performing the same powering operation as the control circuit 5 of the power supply apparatus 1 of fig. 1.

The control circuit 5a controls the boost switching elements T41, T42, T43, T44, T45, and T46 so that the voltage supplied from the smoothing circuit 3a to the positive conversion circuit 2a becomes equal to the peak value of the voltage on the primary side of the positive conversion circuit 2a, that is, the smoothing circuit 3a has a function as boost chopper in which energy is accumulated in the smoothing inductors L1, L2, L3, L4, L5, and L6 by turning on the boost switching elements T41, T42, T43, T44, T45, and T46, and a voltage higher than the voltage of the smoothing capacitors C1 and C2 is applied to the regeneration switching elements T31, T32, T33, T34, T35, and T36.

The control circuit 5a controls the regenerative switching elements T31, T32, T33, T34, T35, T36 such that a voltage synchronized with the primary power source S is taken out from the voltage of the smoothing circuit 3a and supplied to the primary power source.

As described above, the power supply device 1a can perform a regenerative operation of supplying electric power to the primary power source S using the electric motor M as a generator while performing voltage transformation without using a transformer and outputting ac of an arbitrary frequency by setting the potential of the neutral point to a predetermined voltage.

More specifically, in the power supply device 1a, the forward conversion circuit 2a includes a plurality of regenerative switching elements T31, T32, T33, T34, T35, T36 provided so as to correspond to the forward conversion switching elements T11, T12, T13, T14, T15, T16 and capable of causing a current to flow in a reverse direction, and the smoothing circuit 3a includes a plurality of boost switching elements T1, T3646 disposed between a position on the forward conversion circuit 2a side of the smoothing inductor and an intermediate point between a pair of smoothing capacitors C1, C1 and is configured so as to be capable of converting an ac voltage supplied from the output side into a dc voltage, the control circuit 5a controls the boost switching elements T1, T1 and T1, and the power supply voltage from the smoothing circuit T1 a power supply circuit T1, T1 a to the forward conversion circuit 2a, T1 is connected to the smoothing circuit 1, T1 and the power supply circuit T1, T1 and T1 are connected to the smoothing switch circuits for once.

The power supply device 1a includes an insulation deterioration detection circuit 6 that connects the midpoint between the pair of smoothing capacitors C1 and C2 to ground via a detection switch Sw and a detection resistor Rd. Thus, by turning on only one of the reverse conversion switching elements T21, T22, T23, T24, T25, and T26, a fault such as a ground short circuit or insulation deterioration of the load connected to the output side of the reverse conversion circuit 4 can be detected.

Fig. 4 is a circuit diagram showing a configuration of a power supply device 1b according to an embodiment of the present invention different from that of fig. 1 and 3. The power supply device 1b of fig. 4 includes: a positive conversion circuit 2 that takes out a positive voltage and a negative voltage from the primary power source S for each phase independently; a smoothing circuit 3b that obtains a stable direct current by smoothing the current supplied from the positive conversion circuit 2; a reverse conversion circuit 4 that outputs an alternating current of a desired frequency by reversely converting the output of the smoothing circuit 3b into an alternating current; and a control circuit 5b that controls the positive conversion circuit 2, the smoothing circuit 3b, and the reverse conversion circuit 4.

In the smoothing circuit 3b of the power supply device 1b of fig. 4, a single smoothing inductor L7 is provided instead of the positive smoothing inductors L1, L2 and L3 of the smoothing circuit 3 of the power supply device 1 of fig. 1, and a single smoothing inductor L8 is provided instead of the negative smoothing inductors L4, L5 and L6, and therefore, the same components as those of the power supply device 1 of fig. 1 are denoted by the same reference numerals and overlapping descriptions are omitted with respect to the power supply device 1b of fig. 4.

The smoothing circuit 3b is configured to supply a current to the positive smoothing capacitor C1 via the smoothing inductor L7 so that the positive phase outputs of the positive converter circuit 2 are combined into one output, and to supply a current to the negative smoothing capacitor C2 via the smoothing inductor L8 so that the negative phase outputs of the positive converter circuit 2 are combined into one output.

In the power supply device 1b of fig. 4, the control circuit 5b may control the positive changeover switching elements T11, T12, T13, T14, T15, and T16 of the positive changeover circuit 2 in the same manner as the power supply device 1 of fig. 1. In this case, positive transfer switching elements T11, T12, T13, T14, T15, and T16 of the plurality of phases may be turned on at the same time, but a current may flow only to a phase having a large absolute value of potential. In the power supply apparatus 1b of fig. 4, the control circuit 5b may turn on any one of the positive conversion switching elements T11, T12, and T13 of the positive conversion circuit 2 to extract the voltage of the phase having the highest potential among the phases of the primary power source S, and turn on any one of the negative conversion switching elements T14, T15, and T16 of the positive conversion circuit 2 to extract the voltage of the phase having the lowest potential among the phases of the primary power source S. The control circuit 5b may control the positive changeover switching elements T11, T12, T13, T14, T15, and T16 so as to alternately turn on phases in which the absolute value of the potential in each phase of the primary power source S is larger than the absolute values of the potentials E1 and E2 at the points P1 and P2 for each cycle of the PWM control.

Since the power supply device 1b of fig. 4 has a small number of components, the device can be reduced in size and cost.

Fig. 5 is a circuit diagram showing a configuration of a power supply device 1c according to an embodiment of the present invention different from that shown in fig. 1, 3, and 4. The power supply device 1c includes: a positive conversion circuit 2a that takes out a positive voltage and a negative voltage from the primary power supply for each phase independently; a smoothing circuit 3c that obtains a stable direct current by smoothing the current supplied from the positive conversion circuit 2 a; a reverse conversion circuit 4 that outputs an alternating current of a desired frequency by reversely converting the output of the smoothing circuit 3a into an alternating current; an insulation deterioration detection circuit 6 for detecting an abnormality of the motor M; and a control circuit 5c that controls the positive converter circuit 2a, the smoothing circuit 3c, the reverse converter circuit 4, and the insulation deterioration detection circuit 6.

In the smoothing circuit 3c of the power supply apparatus 1c of fig. 5, a single smoothing inductor L7 is provided in place of the positive smoothing inductors L1, L2, L3 of the smoothing circuit 3a of the power supply apparatus 1a of fig. 2, and a single smoothing inductor L8 is provided in place of the negative smoothing inductors L4, L5, L6, so that the same reference numerals are given to the same components as those of the power supply apparatus 1a of fig. 2 and redundant description is omitted with respect to the power supply apparatus 1c of fig. 5.

The control circuit 5c of the power supply device 1c of fig. 5 can control the positive changeover switching elements T11, T12, T13, T14, T15, and T16 of the positive changeover circuit 2a at the time of power running, in the same manner as the control circuit 5b of the power supply device 1b of fig. 4 controls the positive changeover switching elements T11, T12, T13, T14, T15, and T16 of the positive changeover circuit 2.

The embodiments of the present invention have been described above, but the present invention is not limited to the above embodiments. The effects described in the present embodiment are merely the best effects produced by the present invention, and the effects of the present invention are not limited to the effects described in the present embodiment.

In the power supply device according to the present invention, the insulation deterioration detection circuit has an arbitrary configuration, and the insulation deterioration detection circuit can be provided even when the power supply device does not have a regeneration function.

In the power supply device according to the present invention, the control circuit may perform PWM control on the switching element of the positive converter circuit so that the voltage of the pair of smoothing capacitors becomes a predetermined voltage, the potential at the midpoint of the pair of smoothing capacitors becomes a predetermined potential, and the current flowing through the positive converter circuit becomes a predetermined current. Thus, the neutral point potential is maintained at a predetermined potential without using a transformer, and then converted to a voltage suitable for the load, thereby further improving the power factor of the input current and suppressing the peak current.