阅读说明：本技术 单相非隔离型逆变器及其控制方法 (Single-phase non-isolated inverter and control method thereof ) 是由 汪洪亮 田子翔 朱晓楠 岳秀梅 罗安 于 2020-11-09 设计创作，主要内容包括：本发明涉及一种单相非隔离型逆变器及其控制方法,每路直流输入电源均连接一路前级boost单元,各路前级boost单元的输出并联连接到母线电容和后级逆变单元。调制单元能够实时获取输入电压值、负载电压值,根据预设的负载周期以及输入电压值、负载电压值控制前级boost单元和后级逆变单元分时或部分分时工作在高频调制状态。各路所述前级boost单元输出并联,拓宽了电压范围,而且优化的母线电容设计,避免了传统两级式逆变器需要大电解电容实现解耦,减小电容容值,提高了电容的寿命,在调制单元的控制下前级boost单元和后级逆变单元不需要同时工作在高频调制状态,减小了逆变器可控开关整体的开关损耗,提高了效率。(The invention relates to a single-phase non-isolated inverter and a control method thereof. The modulation unit can acquire an input voltage value and a load voltage value in real time, and controls the front-stage boost unit and the rear-stage inversion unit to work in a high-frequency modulation state in a time-sharing or partially time-sharing mode according to a preset load cycle, the input voltage value and the load voltage value. Each way preceding stage boost unit output is parallelly connected, has widened voltage range, and the bus capacitor design of optimizing has moreover avoided traditional two-stage formula dc-to-ac converter to need big electrolytic capacitor to realize the decoupling zero, reduces the electric capacity value, has improved the life-span of electric capacity, and preceding stage boost unit and back stage contravariant unit need not work simultaneously at the high frequency modulation state under the control of modulation unit, have reduced the holistic switching loss of inverter controllable switch, have improved efficiency.)

1. A single-phase non-isolated inverter is applied to a circuit comprising at least two direct current input power supplies, and comprises: the front-stage boost unit, the rear-stage inversion unit, the bus capacitor and the modulation unit; each direct current input power supply is connected with one front-stage boost unit;

the outputs of the front-stage boost units are connected in parallel, the first output ends of the front-stage boost units are simultaneously connected with the first end of the bus capacitor and the first input end of the rear-stage inversion unit, and the second output ends of the front-stage boost units are simultaneously connected with the second end of the bus capacitor and the second input end of the rear-stage inversion unit;

the output of the rear-stage inversion unit is connected with the load unit; the modulation unit is connected with a plurality of control ends of the rear-stage inversion unit and control ends of all the front-stage boost units;

the modulation unit is used for acquiring input voltage values of all paths of the direct current input power supplies and load voltage values of the load units in real time, and controlling the working states of the front-stage boost unit and the rear-stage inversion unit according to the input voltage values, the load voltage values and a preset load period, so that the front-stage boost unit and the rear-stage inversion unit work in a high-frequency modulation state in a time-sharing or partially time-sharing mode.

2. The single-phase non-isolated inverter according to claim 1, wherein each of the preceding boost units comprises a preceding inductor, a preceding diode and a preceding controllable switch;

the first end of the preceding stage inductor is connected with the positive electrode of the direct current input power supply of the corresponding path, the second end of the preceding stage inductor is connected with the positive electrode of the preceding stage diode of the corresponding path and the first end of the preceding stage controllable switch of the corresponding path at the same time, the second end of the preceding stage controllable switch of the corresponding path is connected with the negative electrode of the direct current input power supply of the corresponding path and is used as the second output end of the preceding stage boost unit of the corresponding path at the same time, the negative electrode of the preceding stage diode of the corresponding path is used as the first output end of the preceding stage boost unit of the corresponding path, and the third end of the preceding stage controllable switch in each path of the preceding stage boost unit is used as a plurality of control ends of the preceding stage boost unit.

3. The single-phase non-isolated inverter according to claim 1, wherein each path of the direct current input power supply is further connected with a filtering unit;

each filtering unit comprises a filtering capacitor, and the filtering capacitor is connected with the direct current input power supply of the corresponding path in parallel; and/or

The load unit comprises a filter inductor and a load interface for connecting a load;

the first end of the filter inductor is connected with the first output end of the rear-stage inversion unit, and the second end of the filter inductor is connected with the first end of the load interface;

and the second end of the load interface is connected with the second output end of the rear-stage inversion unit.

4. The single-phase non-isolated inverter according to claim 1, wherein the post-stage inverting unit includes first to fourth inverting controllable switches;

the first end of the first inversion controllable switch is connected with the first end of the third inversion controllable switch and serves as the first input end of the rear-stage inversion unit;

a second end of the second inversion controllable switch is connected with a second end of the fourth inversion controllable switch and serves as a second input end of the rear-stage inversion unit;

the second end of the first inversion controllable switch is connected with the first end of the second inversion controllable switch and serves as the first output end of the rear-stage inversion unit;

a second end of the third inversion controllable switch is connected with a first end of the fourth inversion controllable switch and serves as a second output end of the rear-stage inversion unit;

and the third ends from the first inversion controllable switch to the fourth inversion controllable switch are used as the plurality of control ends of the rear-stage inversion unit and are connected with the modulation unit.

5. The single-phase non-isolated inverter according to claim 4, wherein the modulation unit is configured to, if it is detected in real time that at least one input voltage value of the dc input power supply is greater than the load voltage value, determine a maximum voltage value of all the input voltage values as a target voltage value, send an instruction to the control terminals of all the preceding boost units except for the path corresponding to the maximum voltage value, and control the preceding controllable switches except for the path corresponding to the maximum voltage value to operate, so that the voltage value output by each preceding boost unit is the target voltage value.

6. The single-phase non-isolated inverter according to claim 5, wherein a preceding controllable switch in the preceding boost unit of the path corresponding to the maximum voltage value does not operate.

7. The single-phase non-isolated inverter according to claim 5, wherein if it is detected in real time that at least one input voltage value of the dc input power source is greater than the load voltage value, the modulation unit is further configured to send a command to third terminals of the first inverter controllable switch and the fourth inverter controllable switch to control the first inverter controllable switch and the fourth inverter controllable switch to operate in a high-frequency modulation state if the load is in a positive half cycle; and if the load is in a negative half cycle, sending an instruction to the third ends of the second inversion controllable switch and the third inversion controllable switch to control the second inversion controllable switch and the third inversion controllable switch to work in a high-frequency modulation state.

8. The single-phase non-isolated inverter according to claim 4, wherein the modulation unit is further configured to, if it is detected in real time that all the input voltage values of the lines are less than or equal to the load voltage value, send an instruction to the control terminal of each previous-stage boost unit to control the previous-stage controllable switches in each previous-stage boost unit to operate in a high-frequency modulation state.

9. The single-phase non-isolated inverter according to claim 8, wherein if it is detected in real time that all the input voltage values of the two paths are less than or equal to the load voltage value, the modulation unit is further configured to send a command to third terminals of the first and fourth inverse controllable switches to control the first and fourth inverse controllable switches to operate at a load frequency state if the load is in a positive half cycle; and if the load is in a negative half cycle, sending an instruction to the third ends of the second inversion controllable switch and the third inversion controllable switch to control the second inversion controllable switch and the third inversion controllable switch to work in a load frequency state.

10. The single-phase non-isolated inverter of claim 7 or 9, wherein the second and third controllable switches are not operated if the load is in a positive half cycle; and if the load is in a negative half cycle, the first inversion controllable switch and the fourth inversion controllable switch do not work.

11. A control method of a single-phase non-isolated inverter, wherein the control method is applied to the single-phase non-isolated inverter according to any one of claims 1 to 10, and the control method comprises:

acquiring input voltage values of all direct current input power supplies and load voltage values of load units in real time;

and controlling the working states of a front-stage boost unit and a rear-stage inversion unit according to the input voltage value, the load voltage value and a preset load period, so that the front-stage boost unit and the rear-stage inversion unit work in a high-frequency modulation state in a time-sharing or partially time-sharing mode.

12. The method of claim 11, wherein the controlling the operating states of a front-stage boost unit and a rear-stage inverter unit according to the input voltage value, the load voltage value, and a preset load cycle comprises:

if the fact that the input voltage value of at least one direct current input power supply is larger than the load voltage value is detected in real time, determining the maximum voltage value in all the input voltage values as a target voltage value, sending an instruction to the control ends of the preceding stage boost units of all the other paths except the path corresponding to the maximum voltage value, and controlling the operation of the preceding stage controllable switches corresponding to all the other paths except the path corresponding to the maximum voltage value so that the voltage values output by the preceding stage boost units of all the paths are the target voltage value; and/or

And if the input voltage values of all the paths are detected to be smaller than or equal to the load voltage value in real time, sending an instruction to the control end of each path of the preceding-stage boost unit to control the preceding-stage controllable switches in each path of the preceding-stage boost unit to work in a high-frequency modulation state.

13. The method of claim 12, wherein the controlling the operating states of a front-stage boost unit and a rear-stage inverter unit according to the input voltage value, the load voltage value, and a preset load cycle further comprises:

if the fact that the input voltage value of at least one direct current input power supply is larger than the load voltage value is detected in real time, if the load is in a positive half cycle, sending an instruction to third ends of a first inversion controllable switch and a fourth inversion controllable switch, and controlling the first inversion controllable switch and the fourth inversion controllable switch to work in a high-frequency modulation state; if the load is in a negative half cycle, sending an instruction to third ends of a second inversion controllable switch and a third inversion controllable switch to control the second inversion controllable switch and the third inversion controllable switch to work in a high-frequency modulation state; and/or

If the input voltage values of all the paths are detected to be smaller than or equal to the load voltage value in real time, if the load is in a positive half cycle, sending an instruction to the third ends of the first inversion controllable switch and the fourth inversion controllable switch to control the first inversion controllable switch and the fourth inversion controllable switch to work in a load frequency state, and if the load is in a negative half cycle, sending an instruction to the third ends of the second inversion controllable switch and the third inversion controllable switch to control the second inversion controllable switch and the third inversion controllable switch to work in a load frequency state.

Technical Field

The invention relates to the technical field of power electronic conversion, in particular to a single-phase non-isolated inverter and a control method thereof.

Background

The single-phase non-isolated inverter has the advantages of small size, light weight, high efficiency and the like, and is widely applied to various fields relating to power conversion, such as photovoltaic power generation, energy storage and the like. At present, a single-phase non-isolated inverter has two structures, namely a single-stage structure and a two-stage structure. The input voltage range of the traditional single-stage non-isolated inverter is limited, so that the power energy level is limited; in the traditional two-stage non-isolated inverter, a large capacitor is needed between two stages for energy decoupling control, so that the service life and the power density of the inverter are limited, and meanwhile, two stages of circuits need to work in a high-frequency modulation state at the same time, so that the overall switching loss of the system is large, and the efficiency of the system is influenced.

Disclosure of Invention

In view of this, the present invention provides a single-phase non-isolated inverter and a control method thereof, so as to overcome the limitation of the input voltage range of the conventional single-stage non-isolated inverter, which results in the limitation of the power energy level; and the traditional two-stage non-isolated inverter has the problem that the overall switching loss of the system is large, so that the efficiency of the system is influenced.

In order to achieve the purpose, the invention adopts the following technical scheme:

a single-phase non-isolated inverter is applied to a circuit comprising at least two direct current input power supplies, and comprises: the front-stage boost unit, the rear-stage inversion unit, the bus capacitor and the modulation unit; each direct current input power supply is connected with one front-stage boost unit;

the outputs of the front-stage boost units are connected in parallel, the first output ends of the front-stage boost units are simultaneously connected with the first end of the bus capacitor and the first input end of the rear-stage inversion unit, and the second output ends of the front-stage boost units are simultaneously connected with the second end of the bus capacitor and the second input end of the rear-stage inversion unit;

the output of the rear-stage inversion unit is connected with the load unit; the modulation unit is connected with a plurality of control ends of the rear-stage inversion unit and control ends of all the front-stage boost units;

the modulation unit is used for acquiring input voltage values of all paths of the direct current input power supplies and load voltage values of the load units in real time, and controlling the working states of the front-stage boost unit and the rear-stage inversion unit according to the input voltage values, the load voltage values and a preset load period, so that the front-stage boost unit and the rear-stage inversion unit work in a high-frequency modulation state in a time-sharing or partially time-sharing mode.

Furthermore, in the single-phase non-isolated inverter, each of the preceding-stage boost units includes a preceding-stage inductor, a preceding-stage diode, and a preceding-stage controllable switch;

the first end of the preceding stage inductor is connected with the positive electrode of the direct current input power supply of the corresponding path, the second end of the preceding stage inductor is connected with the positive electrode of the preceding stage diode of the corresponding path and the first end of the preceding stage controllable switch of the corresponding path at the same time, the second end of the preceding stage controllable switch of the corresponding path is connected with the negative electrode of the direct current input power supply of the corresponding path and is used as the second output end of the preceding stage boost unit of the corresponding path at the same time, the negative electrode of the preceding stage diode of the corresponding path is used as the first output end of the preceding stage boost unit of the corresponding path, and the third end of the preceding stage controllable switch in each path of the preceding stage boost unit is used as a plurality of control ends of the preceding stage boost unit.

Furthermore, each path of the single-phase non-isolated inverter is also connected with a filtering unit;

each filtering unit comprises a filtering capacitor, and the filtering capacitor is connected with the direct current input power supply of the corresponding path in parallel; and/or

The load unit comprises a filter inductor and a load interface for connecting a load;

the first end of the filter inductor is connected with the first output end of the rear-stage inversion unit, and the second end of the filter inductor is connected with the first end of the load interface;

and the second end of the load interface is connected with the second output end of the rear-stage inversion unit.

Further, in the single-phase non-isolated inverter described above, the post-stage inverting unit includes a first inverting controllable switch to a fourth inverting controllable switch;

the first end of the first inversion controllable switch is connected with the first end of the third inversion controllable switch and serves as the first input end of the rear-stage inversion unit;

a second end of the second inversion controllable switch is connected with a second end of the fourth inversion controllable switch and serves as a second input end of the rear-stage inversion unit;

the second end of the first inversion controllable switch is connected with the first end of the second inversion controllable switch and serves as the first output end of the rear-stage inversion unit;

a second end of the third inversion controllable switch is connected with a first end of the fourth inversion controllable switch and serves as a second output end of the rear-stage inversion unit;

and the third ends from the first inversion controllable switch to the fourth inversion controllable switch are used as the plurality of control ends of the rear-stage inversion unit and are connected with the modulation unit.

Further, in the single-phase non-isolated inverter described above, the modulation unit is configured to determine, if it is detected in real time that at least one input voltage value of the dc input power supply is greater than the load voltage value, a maximum voltage value of all the input voltage values as a target voltage value, send an instruction to the control terminals of the preceding-stage boost units in all the other lines except the one corresponding to the maximum voltage value, and control the operation of the preceding-stage controllable switches corresponding to all the other lines except the one corresponding to the maximum voltage value, so that the voltage values output by each preceding-stage boost unit are the target voltage value.

Further, in the single-phase non-isolated inverter, the preceding-stage controllable switch in the preceding-stage boost unit in the path corresponding to the maximum voltage value does not operate.

Further, if it is detected in real time that the input voltage value of at least one path of the dc input power is greater than the load voltage value, the modulation unit is further configured to send an instruction to third terminals of the first inverter controllable switch and the fourth inverter controllable switch to control the first inverter controllable switch and the fourth inverter controllable switch to operate in a high-frequency modulation state if the load is in a positive half cycle; and if the load is in a negative half cycle, sending an instruction to the third ends of the second inversion controllable switch and the third inversion controllable switch to control the second inversion controllable switch and the third inversion controllable switch to work in a high-frequency modulation state.

Further, in the single-phase non-isolated inverter, the modulation unit is further configured to send an instruction to a control end of each previous-stage boost unit if it is detected in real time that all the input voltage values of all the paths are less than or equal to the load voltage value, so as to control the previous-stage controllable switches in each previous-stage boost unit to operate in a high-frequency modulation state.

Further, if the single-phase non-isolated inverter detects that the input voltage values of all the paths are smaller than or equal to the load voltage value in real time, the modulation unit is further configured to send an instruction to third terminals of the first inversion controllable switch and the fourth inversion controllable switch to control the first inversion controllable switch and the fourth inversion controllable switch to operate in a load frequency state if the load is in a positive half cycle; and if the load is in a negative half cycle, sending an instruction to the third ends of the second inversion controllable switch and the third inversion controllable switch to control the second inversion controllable switch and the third inversion controllable switch to work in a load frequency state.

Further, in the single-phase non-isolated inverter, if the load is in a positive half cycle, the second inverting controllable switch and the third inverting controllable switch do not work; and if the load is in a negative half cycle, the first inversion controllable switch and the fourth inversion controllable switch do not work.

The invention also provides a control method of the single-phase non-isolated inverter, which is applied to the single-phase non-isolated inverter, and the control method comprises the following steps:

acquiring input voltage values of all direct current input power supplies and load voltage values of load units in real time;

and controlling the working states of a front-stage boost unit and a rear-stage inversion unit according to the input voltage value, the load voltage value and a preset load period, so that the front-stage boost unit and the rear-stage inversion unit work in a high-frequency modulation state in a time-sharing or partially time-sharing mode.

Further, the method for controlling a single-phase non-isolated inverter according to the above includes controlling the operating states of a front-stage boost unit and a rear-stage inverter unit according to the input voltage value, the load voltage value, and a preset load cycle, and includes:

if the fact that the input voltage value of at least one direct current input power supply is larger than the load voltage value is detected in real time, determining the maximum voltage value in all the input voltage values as a target voltage value, sending an instruction to the control ends of the preceding stage boost units of all the other paths except the path corresponding to the maximum voltage value, and controlling the operation of the preceding stage controllable switches corresponding to all the other paths except the path corresponding to the maximum voltage value so that the voltage values output by the preceding stage boost units of all the paths are the target voltage value; and/or

And if the input voltage values of all the paths are detected to be smaller than or equal to the load voltage value in real time, sending an instruction to the control end of each path of the preceding-stage boost unit to control the preceding-stage controllable switches in each path of the preceding-stage boost unit to work in a high-frequency modulation state.

Further, the method for controlling a single-phase non-isolated inverter according to the above includes controlling the operating states of a front-stage boost unit and a rear-stage inverter unit according to the input voltage value, the load voltage value, and a preset load cycle, and further includes:

if the fact that the input voltage value of at least one direct current input power supply is larger than the load voltage value is detected in real time, if the load is in a positive half cycle, sending an instruction to third ends of a first inversion controllable switch and a fourth inversion controllable switch, and controlling the first inversion controllable switch and the fourth inversion controllable switch to work in a high-frequency modulation state; if the load is in a negative half cycle, sending an instruction to third ends of a second inversion controllable switch and a third inversion controllable switch to control the second inversion controllable switch and the third inversion controllable switch to work in a high-frequency modulation state; and/or

If the input voltage values of all the paths are detected to be smaller than or equal to the load voltage value in real time, if the load is in a positive half cycle, sending an instruction to the third ends of the first inversion controllable switch and the fourth inversion controllable switch to control the first inversion controllable switch and the fourth inversion controllable switch to work in a load frequency state, and if the load is in a negative half cycle, sending an instruction to the third ends of the second inversion controllable switch and the third inversion controllable switch to control the second inversion controllable switch and the third inversion controllable switch to work in a load frequency state.

The single-phase non-isolated inverter and the control method thereof provided by the scheme of the application are applied to a photovoltaic power generation circuit comprising at least two direct current input power supplies, and the inverter comprises a rear-stage inverter unit, a modulation unit, a front-stage boost unit and a bus capacitor, wherein each direct current input power supply corresponds to one front-stage boost unit connected in parallel. The modulation unit can acquire input voltage values of all direct current input power supplies and load voltage values of the load units in real time, and controls the working states of the controllable switches in the front-stage boost unit and the rear-stage inversion unit according to the input voltage values, the load voltage values and a preset period. According to the technical scheme, the preceding stage adopts the preceding stage boost units which are connected in parallel in a staggered mode, the input voltage range is wide, the system stability is improved while ripples output from a direct current side are reduced, the optimized bus capacitor design overcomes the defect that a large electrolytic capacitor is required to play a decoupling role in a traditional two-stage inverter, the capacitance value of the capacitor is reduced, the volume of the capacitor is reduced, the service life of the capacitor is prolonged, the power density and the efficiency of the inverter are improved, the preceding stage boost unit and the subsequent stage inversion unit do not need to work in a high-frequency modulation state at the same time, and the overall switching loss of a switching tube of the inverter is reduced.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

FIG. 1 is a circuit diagram provided by one embodiment of a single-phase non-isolated inverter of the present invention;

fig. 2 is a circuit diagram provided by another embodiment of a single-phase non-isolated inverter of the present invention;

FIG. 3 is a graph of voltage relationships for one operating condition of the circuit shown in FIG. 2;

FIG. 4 is a graph of voltage relationships for another operating condition of the circuit shown in FIG. 2;

FIG. 5 is a graph of voltage relationships for another operating condition of the circuit shown in FIG. 2;

fig. 6 is a circuit diagram provided by another embodiment of a single-phase non-isolated inverter of the present invention;

fig. 7 is a flowchart provided by an embodiment of a control method of a single-phase non-isolated inverter according to the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be described in detail below. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the examples given herein without any inventive step, are within the scope of the present invention.

Examples

Fig. 1 is a circuit diagram provided by an embodiment of a single-phase non-isolated inverter of the present invention. Referring to fig. 1, the single-phase non-isolated inverter of the present embodiment is applied to a circuit including at least two dc input power sources. Single-phase non-isolatedThe inverter includes: rear-stage inversion unit 11, modulation unit, front-stage boost unit 12 and bus capacitor C_bus. And each direct current input power supply is connected with one front-stage boost unit.

In this embodiment, the outputs of the preceding stage boost units are connected in parallel, the first output end of each preceding stage boost unit is connected to the first end of the bus capacitor and the first input end of the subsequent stage inversion unit at the same time, the second output end of each preceding stage boost unit is connected to the second end of the bus capacitor and the second input end of the subsequent stage inversion unit at the same time, and the output of the subsequent stage inversion unit is connected to the load unit; the modulation unit is connected with a plurality of control ends of the rear-stage inversion unit and control ends of all the front-stage boost units.

The modulation unit is used for acquiring input voltage values of all direct current input power supplies and load voltage values of the load units in real time, and controlling the working states of the front-stage boost unit 12 and the rear-stage inversion unit 11 according to the input voltage values, the load voltage values and a preset load period, so that the front-stage boost unit 12 and the rear-stage inversion unit 11 work in a high-frequency modulation state in a time-sharing or partially time-sharing mode.

Furthermore, each front-stage boost unit comprises a front-stage inductor, a front-stage diode and a front-stage controllable switch. As shown in FIG. 1, the present embodiment includes a first DC input power source V_in1Second DC input power supply V_in2…, n-th DC input power supply V_innN-path DC input power supply V_inThen, correspondingly setting n-way front-stage boost units. The first front-stage boost unit may include a first front-stage inductor L_b1First front stage diode D_b1And a first preceding controllable switch T_b1The second front-stage boost unit may include a second front-stage inductor L_b2The second front stage diode D_b2And a second preceding controllable switch T_b2…, the nth previous stage boost unit may include an nth previous stage inductor L_bnThe nth front stage diode D_bnAnd an nth preceding controllable switch T_bnAnd n is a positive integer of 2 or more.

The connection mode among all components in each front-stage boost unit is the same, and as shown in fig. 1, all the components are: the first end of the preceding stage inductor is connected with the anode of the direct current input power supply of the corresponding path, the second end of the preceding stage inductor is simultaneously connected with the anode of the preceding stage diode of the corresponding path and the first end of the preceding stage controllable switch, the cathode of the preceding stage diode of the corresponding path is used as the first output end of the preceding stage boost unit of the corresponding path, and the second end of the preceding stage controllable switch of the corresponding path is connected with the cathode of the direct current input power supply of the corresponding path and is simultaneously used as the second output end of the preceding stage boost unit of the corresponding path. The output ends of the front-stage boost units of each path are connected in parallel, namely all the first output ends are connected together and all the second output ends are connected together. The third terminals of the front-stage controllable switches in the front-stage boost units of each path are used as a plurality of control terminals of the front-stage boost unit 12 and are connected with the modulation unit.

Bus capacitor C_busThe first end of the first bus capacitor C is connected with the first input end of the rear-stage inversion unit 11 and the first output ends of all the front-stage boost units at the same time, and the bus capacitor C_busAnd the second end of the second input terminal is connected with the second input terminal of the later stage inversion unit 11 and the second output terminals of all the previous stage boost units. A first output end of the rear-stage inversion unit 11 is connected with a first end of the load unit 13, and a second output end of the rear-stage inversion unit 11 is connected with a second end of the load unit 13. The modulation unit is connected with a plurality of control ends of the rear-stage inversion unit 11 and third ends of all front-stage controllable switches.

The front-stage controllable switch in each front-stage boost unit can adopt an IGBT (insulated gate bipolar transistor) or MOSFET (metal oxide semiconductor field effect transistor) device and the like. However, the present invention is not limited to IGBT devices and MOSFET devices, and may be implemented using other controllable switches. In this embodiment, an N-channel MOSFET is taken as an example for explanation, and a first terminal of the N-channel MOSFET refers to a drain, a second terminal refers to a source, and a third terminal refers to a gate.

Further, in the single-phase non-isolated inverter of the present embodiment, each path of the dc input power is further connected to a filtering unit.

Each filter unit includes a filter capacitor. For the first DC input power supply V_in1Second DC input power supply V_in2…, n-th DC input power supply V_innIf n DC input power supplies are used, the first power supply is set correspondinglyContainer C₁A second capacitor C₂… n th capacitor C_nAnd n filter capacitors.

In this embodiment, all the filter capacitors are connected in the same manner, as shown in fig. 1, the filter capacitor is connected in parallel with the corresponding dc input power supply, that is, the first end of the filter capacitor is connected to the positive electrode of the corresponding dc input power supply and the first end of the preceding stage inductor of the corresponding circuit at the same time, and the second end of the filter capacitor is connected to the negative electrode of the corresponding dc input power supply and the second end of the preceding stage controllable switch of the corresponding circuit at the same time.

Further, in the single-phase non-isolated inverter of the present embodiment, the load unit 13 includes a filter inductor L_gAnd a load interface S for connecting a load. Wherein, the filter inductance L_gIs connected with the first output end of the rear-stage inversion unit 11, and the filter inductor L_gThe second end of the load interface S is connected to the first end of the load interface S, and the second end of the load interface S is connected to the second output end of the post-stage inverter unit 11. Wherein a minimum inversion voltage V of the inverter is set_inv(min)For a load with an AC voltage V across it_gPeak value of (a).

Further, in the single-phase non-isolated inverter of the present embodiment, the post-stage inverting unit 11 includes a first inverting controllable switch T₁To the fourth inverse transformation controllable switch T₄。

Specifically, the first inversion controllable switch T₁First terminal and third inversion controllable switch T₃Is connected with the first end and is used as the first input end of a rear-stage inversion unit 11, and a second inversion controllable switch T₂Second terminal and fourth inverse-change controllable switch T₄Is connected with the second end of the first inverter and is used as the second input end of the later stage inverter unit 11, and the first inverter controllable switch T₁And a second inverter controllable switch T₂Is connected with the first end of the third inverter controllable switch T and is used as the first output end of the rear-stage inverter unit 11₃Second terminal and fourth inverse-change controllable switch T₄And is connected to serve as a second output terminal of the subsequent stage inverter unit 11. First inversion controllable switch T₁To the fourth inverse transformation controllable switch T₄As a rear stageAnd a plurality of control ends of the inversion unit 11 are connected with the modulation unit.

Wherein, the first inversion controllable switch T₁To the fourth inverse transformation controllable switch T₄IGBT or MOSFET devices and the like may also be employed. However, the present invention is not limited to IGBT devices and MOSFET devices, and may be implemented using other controllable switches. In this embodiment, the first inverter controllable switch T₁To the fourth inverse transformation controllable switch T₄An N-channel MOSFET is taken as an example for explanation, wherein a first terminal of the N-channel MOSFET refers to a drain electrode, a second terminal refers to a source electrode, and a third terminal refers to a gate electrode.

In this embodiment, the modulation unit can obtain voltage values of all the lines of dc input power supplies, that is, input voltage values of all the lines of preceding boost units (for convenience of description, referred to as input voltage values of the dc input power supplies for short) and load voltage values of the load units 13 in real time, and control the operating states of the preceding boost units 12 and the subsequent inverter units 11 according to the input voltage values, the load voltage values, and a preset load period, so that the preceding boost units 12 and the subsequent inverter units 11 operate in a high-frequency modulation state in a time-sharing or partially time-sharing manner.

The high-frequency modulation state refers to that controllable switches in the front-stage boost unit 12 and the rear-stage inverter unit 11 are switched on and off at respective preset switching frequencies when working. The preset switching frequencies of the front stage boost unit 12 and the rear stage inverter unit 11 may be the same or different, and the present invention is not limited thereto.

Specifically, if the modulation unit detects that the input voltage value of at least one direct current input power supply is greater than the load voltage value in real time, the circuit control may be performed in the following manner:

and determining the maximum voltage value in all the input voltage values as a target voltage value, and sending an instruction to the third end of the controllable switch by the modulation unit to control the front-stage controllable switches corresponding to all the other circuits except the circuit corresponding to the maximum voltage value to work so as to enable the voltage values output by the front-stage boost unit of each circuit to be the target voltage value. If the load is in the positive half cycle, the first inversion controllable switch T is turned to₁And a fourth inverse-change controllable switch T₄The third end of the inverter sends an instruction to control the first inverter controllable switch T₁And a fourth inverse-change controllable switch T₄Working in a high-frequency modulation state; if the load is in the negative half cycle, the second inversion controllable switch T is turned to₂And a third inversion controllable switch T₃The third end of the inverter sends a command to control the second inverter controllable switch T₂And a third inversion controllable switch T₃And the high-frequency modulation state is operated.

The operation of the preceding-stage controllable switches corresponding to all the other paths except the path corresponding to the maximum voltage value means that the preceding-stage controllable switches corresponding to all the other paths except the path corresponding to the maximum voltage value are turned on and off at a preset switching frequency, so that the voltage values output by the preceding-stage boost units of the path corresponding to the preceding-stage controllable switches are all target voltage values. That is, at this time, the boosting ratio of all the previous-stage boost units except the maximum voltage value corresponding path is constant, and is equal to the maximum voltage value divided by the input voltage value of the corresponding previous-stage boost unit. The front stage controllable switch of the circuit corresponding to the maximum voltage value does not work.

The modulation unit is further configured to perform circuit control in the following manner if it is detected in real time that all input voltage values are less than or equal to the load voltage value:

the modulation unit sends an instruction to the control end of the controllable switch to control the front-stage controllable switch in each front-stage boost unit to work in a high-frequency modulation state. If the load is in the positive half cycle, the first inversion controllable switch T is turned to₁And a fourth inverse-change controllable switch T₄The third end of the inverter sends an instruction to control the first inverter controllable switch T₁And a fourth inverse-change controllable switch T₄Working in a load frequency state; if the load is in the negative half cycle, the second inversion controllable switch T is turned to₂And a third inversion controllable switch T₃The third end of the inverter sends a command to control the second inverter controllable switch T₂And a third inversion controllable switch T₃And operating in a load frequency state.

The load frequency state refers to that the controllable switches in the front-stage boost unit 12 and the rear-stage inverter unit 11 are switched on and off by taking the load frequency as the switching frequency when working.

The operation of the preceding-stage controllable switches in each preceding-stage boost unit in the high-frequency modulation state means that the preceding-stage controllable switches in each preceding-stage boost unit are switched on and off at a preset switching frequency under the state, so that the output voltage of each preceding-stage boost unit is completely consistent with the load voltage in real time. That is, in this state, the boost ratio of the front-stage boost unit in each line is a variable, and changes in real time with the change of the load voltage value, and is equal to the absolute value of the load voltage divided by the input voltage value of the front-stage boost unit in the corresponding line.

Fig. 2 is a circuit diagram of another embodiment of a single-phase non-isolated inverter of the present invention. As shown in FIG. 2, the present embodiment is designed to set a first DC input power V_in1Second DC input power supply V_in2The technical scheme is further explained by taking 2 paths of direct current input power supplies as an example.

Specifically, if 2-way dc input power is provided, a first previous-stage boost unit and a second previous-stage boost unit are correspondingly provided, and a first filtering unit and a second filtering unit are correspondingly provided. The first front stage boost unit comprises a first front stage inductor L_b1First front stage diode D_b1And a first preceding controllable switch T_b1In this embodiment, the second front stage boost unit includes a second front stage inductor L_b2The second front stage diode D_b2And a second preceding controllable switch T_b2. The first filter unit comprises a first capacitor C₁The second filter unit comprises a second capacitor C₂. Fig. 2 shows a circuit diagram obtained by connecting the components in the connection manner described in the above embodiment.

According to the input side, as shown in FIG. 2, two paths of input DC voltage V_in1And V_in2And minimum inversion voltage V_inv(min)The following 3 operating conditions exist in this embodiment:

the first operating condition is:

fig. 3 is a voltage relationship diagram for one operating condition of the circuit shown in fig. 2. As shown in FIG. 3, under this condition, two input voltages V_in1And V_in2Are all less than the minimum inversion voltage V_inv(min). In this embodiment, V is set_in1＜V_in2Then is oneThe voltage relationships that may exist during the duty cycle are shown in fig. 3.

Wherein, in the positive half cycle of the load cycle, the second inversion controllable switch T₂And a third inversion controllable switch T₃Non-working negative half-cycle first inversion controllable switch T₁And a fourth inverse-change controllable switch T₄And does not work. The specific working conditions of the circuit in time intervals are as follows:

[t₀，t₁]: at this stage, in the positive half cycle of the duty cycle, and satisfy | V_g|＜V_in1＜V_in2First front controllable switch T_b1Working to boost the output voltage of the first boost unit to V_in2Second preceding controllable switch T_b2And does not work. Thus, the bus voltage is maintained at V_in2First inverter controllable switch T₁And a fourth inverse-change controllable switch T₄And the high-frequency modulation state is operated.

[t₁，t₂]: at this stage, the load cycle is in the positive half cycle and V is satisfied_in1＜|V_g|＜V_in2First front controllable switch T_b1Working to boost the output voltage of the first boost unit to V_in2Second preceding controllable switch T_b2And does not work. Thus, the bus voltage is maintained at V_in2First inverter controllable switch T₁And a fourth inverse-change controllable switch T₄And the high-frequency modulation state is operated.

[t₂，t₃]: at this stage, the load cycle is in the positive half cycle and V is satisfied_in1＜V_in2＜|V_gI, the first preceding stage controllable switch T_b1The second front stage controllable switch T_b2All work in a high-frequency modulation state, and the first inversion controllable switch T₁And a fourth inverse-change controllable switch T₄And operating in a load frequency state.

[t₃，t₄]: at this stage, the load cycle is in the positive half cycle and V is satisfied_in1＜|V_g|＜V_in2First front controllable switch T_b1Working to boost the output voltage of the first boost unit to V_in2Second preceding stage controllable switchT_b2And does not work. Thus, the bus voltage is maintained at V_in2First inverter controllable switch T₁And a fourth inverse-change controllable switch T₄And the high-frequency modulation state is operated.

[t₄，t₅]: at this stage, in the positive half cycle of the duty cycle, and satisfy | V_g|＜V_in1＜V_in2First front controllable switch T_b1Working to boost the output voltage of the first boost unit to V_in2Second preceding controllable switch T_b2And does not work. Thus, the bus voltage is maintained at V_in2First inverter controllable switch T₁And a fourth inverse-change controllable switch T₄And the high-frequency modulation state is operated.

[t₅，t₆]: at this stage, in the negative half cycle of the load cycle, the control process is similar to the above-mentioned positive half cycle, and when | V is satisfied_g|＜V_in1＜V_in2Or V_in1＜|V_g|＜V_in2While, the first preceding stage controllable switch T_b1Working to boost the output voltage of the first boost unit to V_in2Second preceding controllable switch T_b2And does not work. Thus, the bus voltage is maintained at V_in2Second inversion controllable switch T₂And a third inversion controllable switch T₃Working in a high-frequency modulation state; when V is satisfied_in1＜V_in2＜|V_gWhen l, the first preceding controllable switch T_b1And a second preceding controllable switch T_b2All work in a high-frequency modulation state, and the second inversion controllable switch T₂And a third inversion controllable switch T₃And operating in a load frequency state.

Compared with a boost parallel two-stage inverter, the controllable switch in the front stage boost unit and the controllable switch in the rear stage inverter unit of the single-phase non-isolated inverter in the first working condition of the embodiment work in a high-frequency modulation state in a time-sharing or partially time-sharing mode, so that the loss of the overall switching tube of the inverter is reduced.

The second operating condition is as follows:

fig. 4 is a voltage relationship diagram for another operating condition of the circuit shown in fig. 2. Such asFIG. 4 shows that under such a condition, one of the two inputs is less than the minimum inversion voltage V_inv(min)The other path is greater than the minimum inversion voltage V_inv(min). In this embodiment, an input voltage V is set_in1Less than minimum inversion voltage V_inv(min)Input voltage V_in2Greater than the minimum inversion voltage V_inv(min)The voltage relationship existing during one duty cycle is shown in fig. 4.

Wherein the second inversion controllable switch T of the positive half cycle of the load cycle₂And a third inversion controllable switch T₃Non-working negative half-cycle first inversion controllable switch T₁And a fourth inverse-change controllable switch T₄And does not work. The specific working conditions of the circuit in time intervals are as follows:

[t₀，t₁]: at this stage, in the positive half cycle of the duty cycle, and satisfy | V_g|＜V_in1＜V_in2First front controllable switch T_b1Working to boost the output voltage of the first boost unit to V_in2Second preceding controllable switch T_b2And does not work. Thus, the bus voltage is maintained at V_in2First inverter controllable switch T₁And a fourth inverse-change controllable switch T₄And the high-frequency modulation state is operated.

[t₁，t₂]: at this stage, the load cycle is in the positive half cycle and V is satisfied_in1＜|V_g|＜V_in2First front controllable switch T_b1Working to boost the output voltage of the first boost unit to V_in2Second preceding controllable switch T_b2And does not work. Thus, the bus voltage is maintained at V_in2First inverter controllable switch T₁And a fourth inverse-change controllable switch T₄And the high-frequency modulation state is operated.

[t₂，t₃]: at this stage, in the positive half cycle of the duty cycle, and satisfy | V_g|＜V_in1＜V_in2First front controllable switch T_b1Working to boost the output voltage of the first boost unit to V_in2Second preceding controllable switch T_b2And does not work. Thus, the bus voltage is maintained at V_in2First inverter controllable switch T₁And a fourth inverse-change controllable switch T₄And the high-frequency modulation state is operated.

[t₃，t₄]: at this stage, in the negative half cycle of the load cycle, the control process is similar to the positive half cycle when | V is satisfied_g|＜V_in1＜V_in2Or V_in1＜|V_g|＜V_in2First front controllable switch T_b1Working to boost the output voltage of the first boost unit to V_in2Second preceding controllable switch T_b2And does not work. Thus, the bus voltage is maintained at V_in2Second inversion controllable switch T₂And a third inversion controllable switch T₃And the high-frequency modulation state is operated.

The third operating condition:

fig. 5 is a voltage relationship diagram for another operating condition of the circuit shown in fig. 2. As shown in fig. 5, two input voltages V_in1And V_in2Are all greater than the minimum inversion voltage V_inv(min). In this embodiment, V is set_in1＜V_in2The voltage relationship existing during one duty cycle is shown in fig. 5.

Wherein the second inversion controllable switch T of the positive half cycle of the load cycle₂And a third inversion controllable switch T₃Non-working negative half-cycle first inversion controllable switch T₁And a fourth inverse-change controllable switch T₄And does not work. The specific working conditions of the circuit in time intervals are as follows:

[t₀，t₁]: at this stage, in the positive half cycle of the duty cycle, and satisfy | V_g|＜V_in1＜V_in2First front controllable switch T_b1Working to boost the output voltage of the first boost unit to V_in2Second preceding controllable switch T_b2And does not work. Thus, the bus voltage is maintained at V_in2First inverter controllable switch T₁And a fourth inverse-change controllable switch T₄And the high-frequency modulation state is operated.

[t₁，t₂]: at this stage, the load cycle is in the negative half cycle and | V is satisfied_g|＜V_in1＜V_in2The control process is similar to the positive half cycle, and the first front stage controllable switch T_b1Working to boost the output voltage of the first boost unit to V_in2Second preceding controllable switch T_b2And does not work. Thus, the bus voltage is maintained at V_in2Second inversion controllable switch T₂And a third inversion controllable switch T₃And the high-frequency modulation state is operated.

In the second and third operating conditions, compared with the existing boost parallel type two-stage inverter, the operating conditions of the controllable switches in the single-phase non-isolated inverter of the embodiment are the same, so that the controllable switching losses are not different.

By comprehensively analyzing the three working conditions, on the whole, the single-phase non-isolated inverter of the embodiment adopts a two-stage structure, but the front-stage boost unit and the rear-stage inverter unit work in a high-frequency modulation state in a time-sharing or partially time-sharing mode, so that compared with a traditional two-stage control strategy, the switching loss of a system controllable switch can be reduced, the power loss of the controllable switch can be reduced, the power energy utilization rate of the inverter can be improved, and further the working efficiency of the inverter can be improved.

Fig. 6 is a circuit diagram of another embodiment of a single-phase non-isolated inverter of the present invention. In specific application, the dc input power is a photovoltaic array, and two sets of PV arrays are provided in this embodiment₁And PV₂Fig. 6 shows a specific example of the two-way dc input power supply.

It should be noted that only two sets of photovoltaic arrays PV are used here₁And PV₂The number of photovoltaic arrays is not limited, but is illustrated by way of example. Fig. 6 is only one embodiment of the present invention applied to a photovoltaic power generation system, but the present invention is not limited to the application to the photovoltaic power generation system, and may be applied to other occasions requiring an inverter, such as energy storage.

Based on one general inventive concept, the present embodiment also provides a control method of a single-phase non-isolated inverter, which may be applied to the single-phase non-isolated inverter of the above embodiments.

Fig. 7 is a flowchart provided by an embodiment of a control method of a single-phase non-isolated inverter according to the present invention. As shown in fig. 7, the control method of the single-phase non-isolated inverter of the present embodiment includes:

s101, acquiring input voltage values of all direct current input power supplies and load voltage values of load units in real time;

s102, controlling the working states of a front-stage boost unit and a rear-stage inversion unit according to an input voltage value, a load voltage value and a preset load period, and enabling the front-stage boost unit and the rear-stage inversion unit to work in a high-frequency modulation state in a time-sharing or partially time-sharing mode.

Specifically, if it is detected in real time that the input voltage value of at least one direct current input power supply is greater than the load voltage value, determining the maximum voltage value of all the input voltage values as a target voltage value, sending an instruction to the third terminals of the front-stage controllable switches in the front-stage boost unit of all the other circuits except the circuit corresponding to the maximum voltage value, and controlling the front-stage controllable switches corresponding to all the other circuits except the circuit corresponding to the maximum voltage value to work, so that the voltage value output by each circuit of the front-stage boost unit is the target voltage value. At this time, the front controllable switch in the front boost unit of the circuit corresponding to the maximum voltage value does not work.

If the load is in the positive half cycle, the first inversion controllable switch T is turned to₁And a fourth inverse-change controllable switch T₄The third end of the inverter sends an instruction to control the first inverter controllable switch T₁And a fourth inverse-change controllable switch T₄Working in high-frequency modulation state, the second inversion controllable switch T₂And a third inversion controllable switch T₃Not working; if the load is in the negative half cycle, the second inversion controllable switch T is turned to₂And a third inversion controllable switch T₃The third end of the inverter sends a command to control the second inverter controllable switch T₂And a third inversion controllable switch T₃Working in high-frequency modulation state, the first inversion controllable switch T₁And a fourth inverse-change controllable switch T₄Not working;

and if all the input voltage values are detected to be smaller than or equal to the load voltage value in real time, sending an instruction to the third end of the front-stage controllable switch in each front-stage boost unit, and controlling the front-stage controllable switch in each front-stage boost unit to work in a high-frequency modulation state.

If the load is in the positive half cycle, the first inversion controllable switch T is turned to₁And a fourth inverse-change controllable switch T₄The third end of the inverter sends an instruction to control the first inverter controllable switch T₁And a fourth inverse-change controllable switch T₄Working at load frequency, the second inverter controllable switch T₂And a third inversion controllable switch T₃Not working; if the load is in the negative half cycle, the second inversion controllable switch T is turned to₂And a third inversion controllable switch T₃The third end of the inverter sends a command to control the second inverter controllable switch T₂And a third inversion controllable switch T₃Working at load frequency, the first inversion controllable switch T₁And a fourth inverse-change controllable switch T₄And does not work.

It is understood that the same or similar parts in the above embodiments may be mutually referred to, and the same or similar parts in other embodiments may be referred to for the content which is not described in detail in some embodiments.

It should be noted that the terms "first," "second," and the like in the description of the present invention are used for descriptive purposes only and are not to be construed as indicating or implying relative importance. Further, in the description of the present invention, the meaning of "a plurality" means at least two unless otherwise specified.

Any process or method descriptions in flow charts or otherwise described herein may be understood as representing modules, segments, or portions of code which include one or more executable instructions for implementing specific logical functions or steps of the process, and alternate implementations are included within the scope of the preferred embodiment of the present invention in which functions may be executed out of order from that shown or discussed, including substantially concurrently or in reverse order, depending on the functionality involved, as would be understood by those reasonably skilled in the art of the present invention.

It should be understood that portions of the present invention may be implemented in hardware, software, firmware, or a combination thereof. In the above embodiments, the various steps or methods may be implemented in software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, any one or combination of the following techniques, which are known in the art, may be used: a discrete logic circuit having a logic gate circuit for implementing a logic function on a data signal, an application specific integrated circuit having an appropriate combinational logic gate circuit, a Programmable Gate Array (PGA), a Field Programmable Gate Array (FPGA), or the like.

It will be understood by those skilled in the art that all or part of the steps carried by the method for implementing the above embodiments may be implemented by hardware related to instructions of a program, which may be stored in a computer readable storage medium, and when the program is executed, the program includes one or a combination of the steps of the method embodiments.

In addition, functional units in the embodiments of the present invention may be integrated into one processing module, or each unit may exist alone physically, or two or more units are integrated into one module. The integrated module can be realized in a hardware mode, and can also be realized in a software functional module mode. The integrated module, if implemented in the form of a software functional module and sold or used as a stand-alone product, may also be stored in a computer readable storage medium.

The storage medium mentioned above may be a read-only memory, a magnetic or optical disk, etc.

In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.