WO2021103842A1 - 一种选通单元和高效非隔离型三电平并网逆变器 - Google Patents

一种选通单元和高效非隔离型三电平并网逆变器 Download PDF

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Publication number
WO2021103842A1
WO2021103842A1 PCT/CN2020/121684 CN2020121684W WO2021103842A1 WO 2021103842 A1 WO2021103842 A1 WO 2021103842A1 CN 2020121684 W CN2020121684 W CN 2020121684W WO 2021103842 A1 WO2021103842 A1 WO 2021103842A1
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Prior art keywords
terminal
diode
switch
connection
circuit module
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PCT/CN2020/121684
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English (en)
French (fr)
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汪洪亮
朱晓楠
岳秀梅
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湖南大学
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/483—Converters with outputs that each can have more than two voltages levels
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/53—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M7/537—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
    • H02M7/539—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters with automatic control of output wave form or frequency
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/0003—Details of control, feedback or regulation circuits
    • H02M1/0038—Circuits or arrangements for suppressing, e.g. by masking incorrect turn-on or turn-off signals, e.g. due to current spikes in current mode control

Definitions

  • the embodiments of the present application relate to the field of inverters, in particular to a gating unit and a high-efficiency non-isolated three-level grid-connected inverter.
  • the non-isolated grid-connected inverter structure does not contain a transformer, and has the advantages of high conversion efficiency, low volume, weight, and cost.
  • the maximum conversion efficiency of the system can reach more than 98%, and it has quickly gained the attention of scientific researchers from all over the world and the industry. First of all, it has been applied in European countries, and other countries and regions have also shown great interest in non-isolated grid-connected inverters.
  • the single-stage type is suitable for higher DC input voltage, and requires that the minimum input voltage is not lower than the peak value of the grid voltage, and the system conversion efficiency is higher, up to 98.8%.
  • the two-stage type can adapt to a wider input voltage range, and the system is optimized and controlled by stages, so the entire system design is very convenient.
  • non-isolated grid-connected inverters When non-isolated grid-connected inverters are applied to photovoltaic power generation systems, they bring advantages such as high efficiency, small size, light weight and low cost, but also lead to electrical connections between the panels and the grid. Due to the parasitic capacitance of the battery panel to the ground, the switching action of the power device of the grid-connected inverter can cause the high-frequency time-varying voltage to act on the parasitic capacitance, which is caused by the parasitic capacitance of the solar panel, the DC/AC filter and the grid impedance.
  • the impedance is very low due to the optimization of the converter efficiency, so the common mode current (also called leakage current or ground current) generated in the circuit may exceed the allowable range.
  • the generation of high-frequency common-mode current will bring conduction and radiation interference, increase in grid current harmonics and losses, and even endanger the safety of equipment and personnel. Therefore, the elimination of common mode current has become an obstacle that must be overcome for the popularization of non-isolated grid-connected inverters, and has become one of the research hotspots of photovoltaic grid-connected inverters.
  • the switching tubes S1-S4 bear most of the switching losses and also share the conduction losses in the active state.
  • the topological structure device has a balanced loss distribution, which is beneficial to prolong the working life of the switch tube.
  • the HERIC topology requires at least six switching devices and six anti-parallel diodes, resulting in an increase in system cost.
  • the purpose of the embodiments of the present application is to overcome the above-mentioned problems or to at least partially solve or mitigate the above-mentioned problems.
  • a gating unit including:
  • a strobe circuit module has four terminals: a first end, a second end, a third end, and a fourth end, and provides five working modes under the control of a control signal:
  • control to turn on the connection between the first terminal and the third terminal, and turn on the connection between the fourth terminal and the second terminal, and disconnect the other terminals of the four terminals The connection between the end;
  • control unidirectionally conducts the connection between the second terminal and the fourth terminal, and the unidirectional conduction connection between the third terminal and the first terminal, and disconnects the four terminals.
  • control to turn on the connection between the first terminal and the fourth terminal, and turn on the connection between the third terminal and the second terminal, and disconnect the other terminals of the four terminals The connection between the end;
  • control unidirectionally conducts the connection between the second end and the third end, and the unidirectional conduction connection between the fourth end and the first end, and disconnects the four terminals.
  • the strobe circuit module includes: a first circuit submodule, a second circuit submodule, and a third circuit submodule;
  • the first circuit submodule and the second circuit submodule each have a first end, a second end, and a third end;
  • the third circuit submodule has a first end, a second end, a third end, and a fourth end ;
  • the first end of the first circuit submodule, the first end of the second circuit submodule, and the first end of the third circuit submodule are simultaneously connected to the first end of the gate circuit module;
  • the second end of the first circuit submodule, the second end of the second circuit submodule, and the second end of the third circuit submodule are simultaneously connected to the second end of the gate circuit module;
  • the third end of the first circuit submodule is connected to the third end of the strobe circuit module
  • the third end of the second circuit submodule is connected to the fourth end of the gate circuit module
  • the third terminal and the fourth terminal of the third circuit submodule are respectively connected to the third terminal and the fourth terminal of the gate circuit module;
  • the first circuit sub-module provides three working states under the control of the control signal: only the connection between the first terminal and the third terminal is turned on; only the connection between the second terminal and the third terminal is turned on; and the connection between the second terminal and the third terminal is turned off; Open all end-to-end connections;
  • the second circuit sub-module provides three working states under the control of the control signal: only the connection between the first terminal and the third terminal is conducted; only the connection between the second terminal and the third terminal is conducted; and the connection between the second terminal and the third terminal is disconnected. Open all end-to-end connections;
  • the third circuit sub-module provides four working states under the control of the control signal: only the connection between the third terminal and the first terminal and the connection between the second terminal and the fourth terminal are conducted; The connection between the four ends to the first end and the connection between the second end and the third end; only the connection between the third end and the fourth end is conducted; all the connections between the end to the end are disconnected.
  • the first circuit submodule includes: a first switch and a second switch;
  • the first switch has a first terminal and a second terminal, which are respectively connected to the first terminal and the third terminal of the gate circuit module;
  • the second switch has a first terminal and a second terminal.
  • the first terminal of the second switch is simultaneously connected to the second terminal of the first switch and the third terminal of the gate circuit module.
  • the second end of the switch is connected to the second end of the gate circuit module.
  • both the first switch and the second switch are fully controllable devices that can be turned on and off.
  • the second circuit submodule includes: a third switch and a fourth switch;
  • the third switch has a first terminal and a second terminal, which are respectively connected to the first terminal and the fourth terminal of the gate circuit module;
  • the fourth switch has a first terminal and a second terminal.
  • the first terminal of the fourth switch is simultaneously connected to the second terminal of the third switch and the fourth terminal of the gate circuit module.
  • the second end of the switch is connected to the second end of the gate circuit module.
  • the third switch and the fourth switch are both fully controllable devices that can be turned on and off.
  • the third circuit sub-module includes: a first diode, a second diode, a third diode, a fourth diode, a fifth diode, a sixth diode, and a first diode. Five switches;
  • the cathode of the first diode is connected to the first end of the gate circuit module
  • the cathode of the second diode is connected to the cathode of the fifth diode
  • the anode of the second diode is connected to the cathode of the third diode
  • the anode of the third diode is connected to the anode of the sixth diode;
  • the anode of the fourth diode is connected to the second end of the gate circuit module
  • the anode of the fifth diode is connected to the cathode of the sixth diode;
  • the fifth switch has a first end and a second end
  • the common terminal of the second diode and the fifth diode is simultaneously connected to the anode of the first diode and the first terminal of the fifth switch, and the second diode and the third diode
  • the common end of the tube is connected to the third end of the gate circuit module, and the common end of the third diode and the sixth diode is connected to the cathode of the fourth diode and the fifth switch at the same time.
  • the common end of the fifth diode and the sixth diode is connected to the fourth end of the gate circuit module.
  • the fifth switch is a fully-controlled device that can be turned on and off.
  • a high-efficiency non-isolated three-level grid-connected inverter including: a filter and a gating unit as described above, the filter including a first inductor And a second inductor, and both have a first end and a second end;
  • the first end of the first inductor is connected to the third end of the gate circuit module
  • the second end of the second inductor is connected to the fourth end of the gate circuit module
  • the second end of the first inductor and the first end of the second inductor are connected to both ends of the power grid.
  • the common mode voltage can maintain a constant value in each mode, so no leakage current is generated, and the same leakage current suppression effect as the HERIC topology structure can be achieved.
  • the leakage current problem of the non-isolated three-level grid-connected inverter is effectively solved, and the unipolar pulse width modulation method is adopted, the output current ripple is small, and the output power quality is high.
  • Figure 1 is a diagram of the HERIC topology in the prior art
  • Fig. 2 is a topological structure diagram of a high-efficiency non-isolated three-level grid-connected inverter according to an embodiment of the present application
  • Fig. 3 is a schematic diagram of a modulation strategy according to another embodiment of the present application.
  • Fig. 4 is a schematic diagram of a first working mode of an inverter according to another embodiment of the present application.
  • Fig. 5 is a schematic diagram of a second working mode of an inverter according to another embodiment of the present application.
  • Fig. 6 is a schematic diagram of a third working mode of an inverter according to another embodiment of the present application.
  • Fig. 7 is a schematic diagram of a fourth working mode of an inverter according to another embodiment of the present application.
  • Fig. 8 is a schematic diagram of a fifth working mode of an inverter according to another embodiment of the present application.
  • Fig. 9 is a flowchart of a method for suppressing leakage current according to another embodiment of the present application.
  • the high-efficiency non-isolated three-level grid-connected inverter provided by the embodiment of the application has three output voltages: +Vdc, 0 and -Vdc, which can be represented by the three levels of +1, 0 and -1 respectively .
  • the output of the inverter includes five conditions: output +1 level (+Vdc) and active power, output +1 level and reactive power, output -1 level and active power, output -1 level (-Vdc) ) And reactive power, output 0 level, respectively corresponding to the first to fifth working modes of the inverter.
  • Vdc represents the DC input voltage.
  • a gating unit including:
  • a strobe circuit module has four terminals: a first end, a second end, a third end, and a fourth end, and provides five working modes under the control of a control signal:
  • connection In the third working mode, control the connection between the first end and the fourth end, and the connection between the third end and the second end, and disconnect the other end-to-end connections among the four terminals. Connection;
  • a high-efficiency non-isolated three-level grid-connected inverter including: a filter and a gating unit as described above, the filter including a first inductor and a second Two inductors, each having a first end and a second end; the first end of the first inductor is connected to the third end of the gate circuit module; the second end of the second inductor is connected to the fourth end of the gate circuit module; first The second end of the inductor and the first end of the second inductor are connected to both ends of the power grid.
  • Fig. 2 is a topological structure diagram of a high-efficiency non-isolated three-level grid-connected inverter according to an embodiment of the present application.
  • the first end of the above-mentioned strobe circuit module is point P
  • the second end is point N
  • the third end is point A
  • the fourth end is point B.
  • the control is turned on.
  • the connection between the two points of PA and the connection between the two points of BN are turned on, and the other end-to-end connections among the four terminals are disconnected.
  • the gate circuit module includes: a first circuit submodule, a second circuit submodule, and a third circuit submodule. Both the first circuit submodule and the second circuit submodule have a first end, a second end and a third end; the third circuit submodule has a first end, a second end, a third end and a fourth end.
  • the first end of the first circuit submodule, the first end of the second circuit submodule, and the first end of the third circuit submodule are simultaneously connected to the first end of the strobe circuit module; the second end of the first circuit submodule Terminal, the second terminal of the second circuit submodule, and the second terminal of the third circuit submodule are simultaneously connected to the second terminal of the gate circuit module; the third terminal of the first circuit submodule is connected to the gate circuit module The third end of the second circuit submodule is connected to the fourth end of the strobe circuit module; the third and fourth ends of the third circuit submodule are respectively connected to the third end of the strobe circuit module End and fourth end;
  • the first circuit sub-module provides three working states under the control of the control signal: only conducts the connection between the first terminal and the third terminal; only conducts the connection between the second terminal and the third terminal; disconnects all End-to-end connection;
  • the second circuit sub-module provides three working states under the control of the control signal: only conducts the connection between the first terminal and the third terminal; only conducts the connection between the second terminal and the third terminal; disconnects all End-to-end connection;
  • the third circuit sub-module provides four working states under the control of the control signal: only the connection between the third terminal and the first terminal and the connection between the second terminal and the fourth terminal are conducted; only the fourth terminal is conducted The connection between the first end and the connection between the second end and the third end; only the connection between the third end and the fourth end is conducted; all the connections between end-to-end are disconnected.
  • the first circuit sub-module is a first bridge arm composed of switching devices S1 and S2, the first end is connected to the first end P of the gate circuit module, and the second end is connected to the gate circuit module
  • the second end N point of the third end, the midpoint of the first bridge arm, is connected to the third end point A of the gate circuit module.
  • the second circuit submodule is a second bridge arm composed of switching devices S3 and S4, the first end is connected to the first end P of the gate circuit module, and the second end is connected to the second end of the gate circuit module At point N, the third end, that is, the midpoint of the second bridge arm, is connected to point B of the fourth end of the gate circuit module.
  • the third circuit sub-module is a circuit composed of a switching device S5 and diodes D1 to D6.
  • the first end is connected to the first end P of the gate circuit module, and the second end is connected to the second end N of the gate circuit module.
  • Point the third end is connected to the third end point A of the gate circuit module, and the fourth end is connected to the fourth end point B of the gate circuit module.
  • the first circuit submodule includes: a first switch and a second switch; the first switch has a first terminal and a second terminal, which are respectively connected to the first terminal and the second terminal of the gate circuit module. The third end; the second switch has a first end and a second end, the first end of the second switch is connected to the second end of the first switch and the third end of the strobe circuit module at the same time, and the second end of the second switch The terminal is connected to the second terminal of the gate circuit module.
  • both the first switch and the second switch are full-control devices that can be turned on and off.
  • the first circuit sub-module includes: switching devices S1 and S2, the first end and the second end of the switching device S1 are respectively connected to the first end P and the third end A of the gate circuit module, and the switch The first end and the second end of the device S2 are respectively connected to the third end A and the second end N of the gate circuit module.
  • the second circuit submodule includes: a third switch and a fourth switch; the third switch has a first terminal and a second terminal, which are respectively connected to the first terminal and the second terminal of the gate circuit module.
  • the fourth end; the fourth switch has a first end and a second end, the first end of the fourth switch is simultaneously connected to the second end of the third switch and the fourth end of the gate circuit module, and the second end of the fourth switch
  • the terminal is connected to the second terminal of the gate circuit module.
  • both the third switch and the fourth switch are fully controllable devices that can be turned on and off.
  • the second circuit sub-module includes: switching devices S3 and S4, the first end and the second end of the switching device S3 are respectively connected to the first end point P and the fourth end point B of the gate circuit module, the switch The first end and the second end of the device S4 are respectively connected to the fourth end point B and the second end point N of the gate circuit module.
  • the third circuit sub-module includes: a first diode, a second diode, a third diode, a fourth diode, a fifth diode, and a second diode.
  • a pole tube and a fifth switch ; the cathode of the first diode is connected to the first end of the gate circuit module; the cathode of the second diode is connected to the cathode of the fifth diode; the The anode of the second diode is connected to the cathode of the third diode; the anode of the third diode is connected to the anode of the sixth diode; the anode of the fourth diode is connected to the The second end of the gate circuit module; the anode of the fifth diode is connected to the cathode of the sixth diode; the fifth switch has a first end and a second end; the second diode And the common terminal of the fifth diode are simultaneously connected to the ano
  • the third circuit sub-module includes: a switching device S5 and diodes D1 to D6, the first terminal is connected to the first terminal P of the gate circuit module, and the second terminal is connected to the second terminal of the gate circuit module. Terminal N, the third terminal is connected to the third terminal A of the gate circuit module, and the fourth terminal is connected to the fourth terminal B of the gate circuit module.
  • the high-efficiency non-isolated three-level grid-connected inverter provided by an embodiment of the present application may specifically include:
  • Photovoltaic panels PV, capacitor C, switching devices S1, S2, S3, S4 and S5, diodes D1, D2, D3, D4, D5 and D6, and filters;
  • the switching devices S1 and S2 constitute the first bridge arm, and the switching devices S3 and S4 constitute the second bridge arm; the first bridge arm and the second bridge arm are respectively connected in parallel with the capacitor C, and the capacitor C is connected in parallel with the photovoltaic panel PV;
  • the switching device S5 and the diode D4 are connected in series, they are connected in parallel with the capacitor C; the diodes D2 and D3 are connected in parallel with the switching device S5 after being connected in series; the diodes D5 and D6 are connected in parallel with the switching device S5 after being connected in series;
  • the midpoint A of the first bridge arm and the midpoint B of the second bridge arm are respectively connected to the first end and the second end of the filter; the anode of the diode D2 and the cathode of D3 are both connected to the midpoint A of the first bridge arm , The anode of the diode D5 and the cathode of D6 are both connected to the midpoint B of the second bridge arm.
  • the modulation wave of the inverter includes: a first modulation wave and a second modulation wave, the first modulation wave and the second modulation wave are both sine waves, and the phase difference is 180 degrees;
  • the carrier of the device includes: a first carrier and a second carrier, and the first carrier and the second carrier are co-directional stacked carriers.
  • Fig. 3 is a schematic diagram of a modulation strategy according to another embodiment of the present application.
  • the modulation wave of the inverter includes: a first modulation wave um+ and a second modulation wave um- , which are two sine modulation waves with a phase difference of 180 degrees, and both are weak current control signals.
  • the carrier of the inverter includes: a first carrier u a and a second carrier u b , which are stacked carriers in the same direction.
  • Each pulse in the figure is a control signal of the switching device, a high level indicates that the switching device is controlled to be turned on, and a low level indicates that the switching device is controlled to be turned off.
  • the amplitude of the modulation wave is proportional to the amplitude of the AC output of the inverter, so the amplitude of the modulation wave determines the amplitude of the AC voltage output by the inverter.
  • the above two sine modulated waves are compared with the above two triangular wave carriers to generate control signals for the switching devices S1 to S5, as shown in the figure.
  • a first modulation wave u m + u a comparison with the first carrier signal S1 and S4 under control of a second modulated carrier wave u m- u b and the second comparison to obtain a control signal S2 and S3.
  • the control signal of the switching device S1 is high, indicating that S1 is on; if u m+ is less than u a , the control signal of the switching device S1 is low, indicating that S1 is off.
  • the switching device S5 is turned on when the switching devices S1, S2, S3, and S4 are turned off at the same time, thereby providing a zero-level freewheeling loop.
  • Fig. 4 is a schematic diagram of a first working mode of an inverter according to another embodiment of the present application.
  • the switching devices S1 and S4 are turned on, after comparing the second modulated wave with the second carrier, the switching devices S2 and S3 are turned off, and the current From the positive bus to the negative bus through S1, L1, L2, S4, the inverter outputs +1 level (+Vdc) and active power.
  • common-mode voltage (output voltage of the first bridge arm+output voltage of the second bridge arm)/2.
  • the output voltage V AN of the first bridge arm is +Vdc
  • the output voltage V BN of the second bridge arm is 0, and the common mode voltage is Vdc/2; where Vdc is the DC input voltage.
  • Fig. 5 is a schematic diagram of a second working mode of an inverter according to another embodiment of the present application.
  • the switching devices S1 and S4 are disconnected, and after comparing the second modulated wave with the second carrier, the switching devices S2 and S3 are disconnected, and the diode D1, D2, D4, and D6 are turned on, and the current flows from the negative bus to the positive bus through D4, D6, L2, L1, D2, D1, and the inverter outputs +1 level (+Vdc) and reactive power.
  • the output voltage V AN of the first bridge arm is +Vdc
  • the output voltage V BN of the second bridge arm is 0, and the common mode voltage is Vdc/2.
  • Fig. 6 is a schematic diagram of a third working mode of an inverter according to another embodiment of the present application.
  • the switching devices S1 and S4 are disconnected, and after comparing the second modulated wave with the second carrier, the switching devices S2 and S3 are turned on, and the current From the positive bus to the negative bus through S3, L2, L1, S2, the inverter outputs -1 level (-Vdc) and active power.
  • the output voltage V AN of the first bridge arm is 0, the output voltage V BN of the second bridge arm is +Vdc, and the common mode voltage is Vdc/2.
  • Fig. 7 is a schematic diagram of a fourth working mode of an inverter according to another embodiment of the present application.
  • the switching devices S1 and S4 are disconnected; after comparing the second modulated wave with the second carrier, the switching devices S2 and S3 are disconnected, and the diode D3, D4, D1, and D5 are turned on, and the current flows from the negative bus to the positive bus through D4, D3, L1, L2, D5, D1, and the inverter outputs -1 level (-Vdc) and reactive power.
  • the output voltage V AN of the first bridge arm is 0, the output voltage V BN of the second bridge arm is +Vdc, and the common mode voltage is Vdc/2.
  • Fig. 8 is a schematic diagram of a fifth working mode of an inverter according to another embodiment of the present application.
  • the AC output of the inverter is decoupled from the DC input, that is, the grid G is not directly connected to the photovoltaic panel PV, and is composed of the switching device S5 and diodes D2, D3, D5, and D6.
  • Two-way freewheeling circuit the inverter outputs 0 level, and the common mode voltage remains unchanged at Vdc/2 (see references L. Zhang, K. Sun, Y. Xing and M.
  • the active branch and the reactive branch in the topology are complementary, that is, all the active switching devices in the active branch are in the reactive branch. There is no multiplexing in the circuit, so all active switching devices do not need anti-parallel diodes, which saves costs.
  • the filter includes a first inductor L1 and a second inductor L2; the first inductor L1 has a first end and a second end, and the first end is connected to the third end (A Point), the second inductor L2 has a first end and a second end, the second end is connected to the fourth end of the gate circuit module (point B), the second end of the first inductor L1 and the second end of the second inductor L2 One end is connected to both ends of the grid G.
  • the inductances of the first inductor L1 and the second inductor L2 are the same.
  • the common-mode voltage can maintain a constant value in each mode, which effectively solves the problem of leakage current generated by the non-isolated three-level grid-connected inverter, and can reach the HERIC topology.
  • the leakage current suppression effect of the same structure Compared with the HERIC topology in terms of the number of devices, there is one less active switch. Since the cost of the active switch occupies a larger proportion in the inverter system, the system cost is saved.
  • the unipolar pulse width modulation method is adopted, the output current ripple is small, and the output power quality is high.
  • the high-efficiency non-isolated three-level grid-connected inverter provided in this application will be explained by taking its application in a photovoltaic power generation system as an example, but it is not limited to its application in a photovoltaic power generation system.

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Abstract

一种选通单元和高效非隔离型三电平并网逆变器，属于逆变器领域。选通单元包括：一个选通电路模块，具有第一端、第二端、第三端和第四端共四个端子，且在控制信号的控制下提供五种工作模式，在五种不同的工作模式下，分别控制不同端之间的导通和断开，使共模电压在各个工作模式均能保持一个恒定值。所述高效非隔离型三电平并网逆变器包括一个所述选通单元，与HERIC拓扑结构从器件数量上相比，少了一个有源开关，由于逆变器系统中，有源开关的成本占据了较大的比例，因此，节省了成本。本申请有效地解决了逆变器漏电流的问题，另外，采用单极性脉冲宽度调制方式，输出电流纹波小，输出电能质量高。

Description

一种选通单元和高效非隔离型三电平并网逆变器 技术领域
本申请的实施例涉及逆变器领域，特别是涉及一种选通单元和高效非隔离型三电平并网逆变器。
背景技术
非隔离型并网逆变器结构不含变压器，拥有变换效率高，体积、重量和成本低等优势，系统最高变换效率能达到98％以上，迅速得到各国科研人员的重视和工业界的追捧，首先在欧洲国家得到应用，其它国家和地区也对非隔离型并网逆变器表现出了极大兴趣。非隔离并网逆变器有两种构成方式：单级式和双级式。单级式适用于更高的直流输入电压，要求最低输入电压不低于电网电压峰值，系统变换效率更高，最高可达98.8％。双级式可以适应较宽的输入电压范围，系统分级优化和控制，因此整个系统设计非常方便。非隔离型并网逆变器应用于光伏发电系统时，带来效率高、体积小、重量轻和成本低等优势的同时，也导致了电池板和电网之间存在电气连接。由于电池板对地寄生电容的存在，并网逆变器功率器件的开关动作可导致高频时变电压作用在寄生电容之上，而在由电池板寄生电容、直/交流滤波器和电网阻抗等组成的谐振回路中，出于变换器效率优化的考虑其阻抗非常低，从而在该回路中产生的共模电流(也称漏电流或地电流)可能超过允许范围。高频共模电流的产生会带来传导和辐射干扰、进网电流谐波及损耗的增加，甚至危及设备和人员安全。因此，共模电流的消除成为了非隔离式并网逆变器得以普及必须跨越之障碍，成为了光伏并网逆变器的研究热点之一。
针对非隔离型逆变器出现的漏电流问题，国内外学者提出了许多改进的拓扑结构，较为典型的结构有H5、H6、改进型H6、混合H6和HERIC等拓扑结构，其主要思路是：构造新的续流回路，使得在续流阶段光伏电池侧与交流电网侧断开，结合开关调制方式，把续流回路电平箝位至一固定值，即使共模电压保持不变，从而抑制漏电流的产生。参见图1，为Sunways公司提出的HERIC拓扑结构，在交流侧加入了由两个开关管和两个二极管构成的续流回路。其中，开关管S1-S4承担了绝大部分的开关损耗，同时也分担了有源状态下的导通损 耗。该拓扑结构器件损耗分布均衡，有利于延长开关管的工作寿命。但是，HERIC拓扑结构至少需要六个开关器件和六个反并联二极管，导致系统成本增加。
发明内容
本申请实施例的目的在于克服上述问题或者至少部分地解决或缓减解决上述问题。
根据本申请实施例的一个方面，提供了一种选通单元，包括：
一个选通电路模块，具有第一端、第二端、第三端和第四端共四个端子，且在控制信号的控制下提供五种工作模式：
第一工作模式下，控制导通所述第一端和第三端之间的连接，以及导通所述第四端和第二端之间的连接，并断开四个端子中的其它端到端之间的连接；
第二工作模式下，控制单向导通所述第二端至第四端之间的连接，以及单向导通所述第三端至第一端之间的连接，并断开四个端子中的其它端到端之间的连接；
第三工作模式下，控制导通所述第一端和第四端之间的连接，以及导通所述第三端和第二端之间的连接，并断开四个端子中的其它端到端之间的连接；
第四工作模式下，控制单向导通所述第二端至第三端之间的连接，以及单向导通所述第四端至第一端之间的连接，并断开四个端子中的其它端到端之间的连接；
第五工作模式下，控制断开所述第一端和第二端之间的连接，导通所述第三端和第四端之间的连接且构成续流回路，并断开四个端子中的其它端到端之间的连接。
可选的，所述选通电路模块包括：第一电路子模块、第二电路子模块、第三电路子模块；
所述第一电路子模块和第二电路子模块均具有第一端、第二端和第三端；所述第三电路子模块具有第一端、第二端、第三端和第四端；
所述第一电路子模块的第一端、所述第二电路子模块的第一端和所述第三电路子模块的第一端同时连接所述选通电路模块的第一端；
所述第一电路子模块的第二端、所述第二电路子模块的第二端和所述第三电路子模块的第二端同时连接所述选通电路模块的第二端；
所述第一电路子模块的第三端连接所述选通电路模块的第三端；
所述第二电路子模块的第三端连接所述选通电路模块的第四端；
所述第三电路子模块的第三端和第四端分别连接所述选通电路模块的第三端和第四端；
所述第一电路子模块在控制信号的控制下提供三种工作状态：仅导通第一端和第三端之间的连接；仅导通第二端和第三端之间的连接；断开所有端到端之间的连接；
所述第二电路子模块在控制信号的控制下提供三种工作状态：仅导通第一端和第三端之间的连接；仅导通第二端和第三端之间的连接；断开所有端到端之间的连接；
所述第三电路子模块在控制信号的控制下提供四种工作状态：仅导通第三端至第一端之间的连接以及第二端至第四端之间的连接；仅导通第四端至第一端之间的连接以及第二端至第三端之间的连接；仅导通第三端和第四端之间的连接；断开所有端到端之间的连接。
可选的，所述第一电路子模块包括：第一开关和第二开关；
所述第一开关具有第一端和第二端，分别连接所述选通电路模块的第一端和第三端；
所述第二开关具有第一端和第二端，所述第二开关的第一端同时连接所述第一开关的第二端和所述选通电路模块的第三端，所述第二开关的第二端连接所述选通电路模块的第二端。
可选的，所述第一开关和第二开关均为导通和关断都可控的全控型器件。
可选的，所述第二电路子模块包括：第三开关和第四开关；
所述第三开关具有第一端和第二端，分别连接所述选通电路模块的第一端和第四端；
所述第四开关具有第一端和第二端，所述第四开关的第一端同时连接所述第三开关的第二端和所述选通电路模块的第四端，所述第四开关的第二端连接所述选通电路模块的第二端。
可选的，所述第三开关和第四开关均为导通和关断都可控的全控型器件。
可选的，所述第三电路子模块包括：第一二极管、第二二极管、第三二极管、第四二极管、第五二极管、第六二极管和第五开关；
所述第一二极管的负极连接所述选通电路模块的第一端；
所述第二二极管的负极连接所述第五二极管的负极；
所述第二二极管的正极连接所述第三二极管的负极；
所述第三二极管的正极连接所述第六二极管的正极；
所述第四二极管的正极连接所述选通电路模块的第二端；
所述第五二极管的正极连接所述第六二极管的负极；
所述第五开关具有第一端和第二端；
所述第二二极管和第五二极管的公共端同时连接所述第一二极管的正极和所述第五开关的第一端，所述第二二极管和第三二极管的公共端连接所述选通电路模块的第三端，所述第三二极管和第六二极管的公共端同时连接所述第四二极管的负极和所述第五开关的第二端，所述第五二极管和第六二极管的公共端连接所述选通电路模块的第四端。
可选的，所述第五开关为导通和关断都可控的全控型器件。
根据本申请实施例的另一个方面，提供了一种高效非隔离型三电平并网逆变器，包括：一个滤波器和一个如上所述的选通单元，所述滤波器包括第一电感和第二电感，且均具有第一端和第二端；
所述第一电感的第一端连接所述选通电路模块的第三端；
所述第二电感的第二端连接所述选通电路模块的第四端；
所述第一电感的第二端和所述第二电感的第一端连接在电网的两端。
本申请实施例提供的技术方案，共模电压在各个模态均能保持一个恒定值，因此不会产生漏电流，可以达到与HERIC拓扑结构相同的漏电流抑制效果。另外，配合相应的调制策略，有效地解决了非隔离型三电平并网逆变器产生漏电流的问题，而且采用单极性脉冲宽度调制方式，输出电流纹波小，输出电能质量高。
根据下文结合附图对本申请的具体实施例的详细描述，本领域技术人员将会更加明了本申请的上述以及其他目的、优点和特征。
附图说明
后文将参照附图以示例性而非限制性的方式详细描述本申请的一些具体实施例。附图中相同的附图标记标示了相同或类似的部件或部分。本领域技术人员应该理解，这些附图未必是按比例绘制的。附图中：
图1是现有技术中HERIC拓扑结构图；
图2是根据本申请一个实施例的高效非隔离型三电平并网逆变器拓扑结构图；
图3是根据本申请另一个实施例的调制策略示意图；
图4是根据本申请另一个实施例的逆变器第一工作模式示意图；
图5是根据本申请另一个实施例的逆变器第二工作模式示意图；
图6是根据本申请另一个实施例的逆变器第三工作模式示意图；
图7是根据本申请另一个实施例的逆变器第四工作模式示意图；
图8是根据本申请另一个实施例的逆变器第五工作模式示意图；
图9是根据本申请另一个实施例的抑制漏电流的方法流程图。
具体实施方式
本申请实施例提供的高效非隔离型三电平并网逆变器，输出电压包括：+Vdc，0和-Vdc三种，可以分别用+1，0和-1这三个电平来表示。逆变器的输出包括五种情况：输出+1电平(+Vdc)且有功功率，输出+1电平且无功功率，输出-1电平且有功功率，输出-1电平(-Vdc)且无功功率，输出0电平，分别对应逆变器的第一至第五工作模式。其中，Vdc表示直流输入电压。
根据本申请的一个实施例，提供了一种选通单元，包括：
一个选通电路模块，具有第一端、第二端、第三端和第四端共四个端子，且在控制信号的控制下提供五种工作模式：
第一工作模式下，控制导通第一端和第三端之间的连接，以及导通第四端和第二端之间的连接，并断开四个端子中的其它端到端之间的连接；
第二工作模式下，控制单向导通第二端至第四端之间的连接，以及单向导通第三端至第一端之间的连接，并断开四个端子中的其它端到端之间的连接；
第三工作模式下，控制导通第一端和第四端之间的连接，以及导通第三端和第二端之间的连接，并断开四个端子中的其它端到端之间的连接；
第四工作模式下，控制单向导通第二端至第三端之间的连接，以及单向导通第四端至第一端之间的连接，并断开四个端子中的其它端到端之间的连接；
第五工作模式下，控制断开第一端和第二端之间的连接，导通第三端和第四端之间的连接且构成续流回路，并断开四个端子中的其它端到端之间的连接。
根据本申请的另一个实施例，提供了一种高效非隔离型三电平并网逆变器，包括：一个滤波器和一个如上所述的选通单元，该滤波器包括第一电感和第二电感，且均具有第一端和第二端；第一电感的第一端连接选通电路模块的第三端；第二电感的第二端连接选通电路模块的第四端；第一电感的第二端和第二电感的第一端连接在电网的两端。
图2是根据本申请一个实施例的高效非隔离型三电平并网逆变器拓扑结构图。参考图2，上述选通电路模块的第一端为P点，第二端为N点，第三端为 A点，第四端为B点，例如，在第一工作模式下，控制导通PA两点之间的连接，以及导通BN两点之间的连接，并断开该四个端子中的其它端到端之间的连接。
本申请实施例中，可选的，所述选通电路模块包括：第一电路子模块、第二电路子模块、第三电路子模块。第一电路子模块和第二电路子模块均具有第一端、第二端和第三端；第三电路子模块具有第一端、第二端、第三端和第四端。
第一电路子模块的第一端、第二电路子模块的第一端和第三电路子模块的第一端同时连接所述选通电路模块的第一端；第一电路子模块的第二端、第二电路子模块的第二端和第三电路子模块的第二端同时连接所述选通电路模块的第二端；第一电路子模块的第三端连接所述选通电路模块的第三端；第二电路子模块的第三端连接所述选通电路模块的第四端；第三电路子模块的第三端和第四端分别连接所述选通电路模块的第三端和第四端；
第一电路子模块在控制信号的控制下提供三种工作状态：仅导通第一端和第三端之间的连接；仅导通第二端和第三端之间的连接；断开所有端到端之间的连接；
第二电路子模块在控制信号的控制下提供三种工作状态：仅导通第一端和第三端之间的连接；仅导通第二端和第三端之间的连接；断开所有端到端之间的连接；
第三电路子模块在控制信号的控制下提供四种工作状态：仅导通第三端至第一端之间的连接以及第二端至第四端之间的连接；仅导通第四端至第一端之间的连接以及第二端至第三端之间的连接；仅导通第三端和第四端之间的连接；断开所有端到端之间的连接。
参考图2，第一电路子模块为开关器件S1和S2所组成的第一桥臂，第一端连接所述选通电路模块的第一端P点，第二端连接所述选通电路模块的第二端N点，第三端即第一桥臂的中点连接所述选通电路模块的第三端A点。第二电路子模块为开关器件S3和S4所组成的第二桥臂，第一端连接所述选通电路模块的第一端P点，第二端连接所述选通电路模块的第二端N点，第三端即第二桥臂的中点连接所述选通电路模块的第四端B点。第三电路子模块为开关器件S5和二极管D1至D6组成的电路，第一端连接所述选通电路模块的第一端P点，第二端连接所述选通电路模块的第二端N点，第三端连接所述选通电路模块的第三端A点，第四端连接所述选通电路模块的第四端B点。
本申请实施例中，可选的，第一电路子模块包括：第一开关和第二开关；第一开关具有第一端和第二端，分别连接所述选通电路模块的第一端和第三端；第二开关具有第一端和第二端，第二开关的第一端同时连接第一开关的第二端和所述选通电路模块的第三端，第二开关的第二端连接所述选通电路模块的第二端。其中，可选的，第一开关和第二开关均为导通和关断都可控的全控型器件。
参考图2，第一电路子模块包括：开关器件S1和S2，开关器件S1的第一端和第二端分别连接所述选通电路模块的第一端P点和第三端A点，开关器件S2的第一端和第二端分别连接所述选通电路模块的第三端A点和第二端N点。
本申请实施例中，可选的，第二电路子模块包括：第三开关和第四开关；第三开关具有第一端和第二端，分别连接所述选通电路模块的第一端和第四端；第四开关具有第一端和第二端，第四开关的第一端同时连接第三开关的第二端和所述选通电路模块的第四端，第四开关的第二端连接所述选通电路模块的第二端。可选的，第三开关和第四开关均为导通和关断都可控的全控型器件。
参考图2，第二电路子模块包括：开关器件S3和S4，开关器件S3的第一端和第二端分别连接所述选通电路模块的第一端P点和第四端B点，开关器件S4的第一端和第二端分别连接所述选通电路模块的第四端B点和第二端N点。
本申请实施例中，可选的，第三电路子模块包括：第一二极管、第二二极管、第三二极管、第四二极管、第五二极管、第六二极管和第五开关；所述第一二极管的负极连接所述选通电路模块的第一端；所述第二二极管的负极连接所述第五二极管的负极；所述第二二极管的正极连接所述第三二极管的负极；所述第三二极管的正极连接所述第六二极管的正极；所述第四二极管的正极连接所述选通电路模块的第二端；所述第五二极管的正极连接所述第六二极管的负极；所述第五开关具有第一端和第二端；所述第二二极管和第五二极管的公共端同时连接所述第一二极管的正极和所述第五开关的第一端，所述第二二极管和第三二极管的公共端连接所述选通电路模块的第三端，所述第三二极管和第六二极管的公共端同时连接所述第四二极管的负极和所述第五开关的第二端，所述第五二极管和第六二极管的公共端连接所述选通电路模块的第四端。可选的，第五开关为导通和关断都可控的全控型器件。
参考图2，第三电路子模块包括：开关器件S5和二极管D1至D6，第一端连接所述选通电路模块的第一端P点，第二端连接所述选通电路模块的第二端N点，第三端连接所述选通电路模块的第三端A点，第四端连接所述选通电路 模块的第四端B点。
参见图2，本申请一实施例提供的高效非隔离型三电平并网逆变器可以具体包括：
光伏电池板PV，电容C，开关器件S1、S2、S3、S4和S5，二极管D1、D2、D3、D4、D5和D6，以及滤波器；
开关器件S1和S2构成第一桥臂，开关器件S3和S4构成第二桥臂；第一桥臂、第二桥臂分别与电容C并联，电容C与光伏电池板PV并联；
二极管D1、开关器件S5和二极管D4串联后，与电容C并联；二极管D2和D3串联后与开关器件S5并联；二极管D5和D6串联后与开关器件S5并联；
第一桥臂的中点A和第二桥臂的中点B，分别连接滤波器的第一端和第二端；二极管D2的正极和D3的负极均与第一桥臂的中点A连接，二极管D5的正极和D6的负极均与第二桥臂的中点B连接。
本实施例中，可选的，上述逆变器的调制波包括：第一调制波和第二调制波，第一调制波和第二调制波均为正弦波，且相位相差180度；逆变器的载波包括：第一载波和第二载波，且第一载波和第二载波为同向层叠载波。
图3是根据本申请另一个实施例的调制策略示意图。参见图3，逆变器的调制波包括：第一调制波u m+和第二调制波u m-，它们为两个相位相差180度的正弦调制波，且均是弱电控制信号。逆变器的载波包括：第一载波u a和第二载波u b，它们为同向层叠载波。图中的各个脉冲是开关器件的控制信号，高电平表示控制该开关器件导通，低电平表示控制该开关器件断开。调制波幅值与逆变器的交流输出幅值是成比例的，因此调制波幅值的大小决定了逆变器输出交流电压幅值的大小。上述两个正弦调制波与上述两个三角波载波进行比较，产生开关器件S1～S5的控制信号，如图所示。第一调制波u m+与第一载波u a比较得到S1与S4的控制信号，第二调制波u m-与第二载波u b比较得到S2与S3的控制信号。例如，u m+大于u a，则开关器件S1的控制信号就为高电平，表示S1导通；u m+小于u a，则开关器件S1的控制信号就为低电平，表示S1断开。开关器件S5在开关器件S1，S2，S3，S4同时关断的时候开通，从而提供零电平续流回路。
图4是根据本申请另一个实施例的逆变器第一工作模式示意图。参见图4，在第一工作模式下，经第一调制波和第一载波比较，开关器件S1和S4导通， 经第二调制波和第二载波比较，开关器件S2和S3断开，电流从正母线经过S1，L1，L2，S4回到负母线，逆变器输出+1电平(+Vdc)且有功功率。
逆变器的共模电压计算方法如下：共模电压＝(第一桥臂的输出电压+第二桥臂的输出电压)/2。第一桥臂的输出电压V AN为+Vdc，第二桥臂的输出电压V BN为0，共模电压为Vdc/2；其中，Vdc为直流输入电压。
图5是根据本申请另一个实施例的逆变器第二工作模式示意图。参见图5，在第二工作模式下，经第一调制波和第一载波比较，开关器件S1和S4断开，经第二调制波和第二载波比较，开关器件S2和S3断开，二极管D1、D2、D4和D6导通，电流由负母线经过D4，D6，L2，L1，D2，D1回到正母线，逆变器输出+1电平(+Vdc)且无功功率。第一桥臂的输出电压V AN为+Vdc，第二桥臂的输出电压V BN为0，共模电压为Vdc/2。
图6是根据本申请另一个实施例的逆变器第三工作模式示意图。参见图6，在第三工作模式下，经第一调制波和第一载波比较，开关器件S1和S4断开，经第二调制波和第二载波比较，开关器件S2和S3导通，电流从正母线经过S3，L2，L1，S2回到负母线，逆变器输出-1电平(-Vdc)且有功功率。第一桥臂的输出电压V AN为0，第二桥臂的输出电压V BN为+Vdc，共模电压为Vdc/2。
图7是根据本申请另一个实施例的逆变器第四工作模式示意图。参见图7，在第四工作模式下，经第一调制波和第一载波比较，开关器件S1和S4断开，经第二调制波和第二载波比较，开关器件S2和S3断开，二极管D3、D4、D1和D5导通，电流由负母线经过D4，D3，L1，L2，D5，D1回到正母线，逆变器输出-1电平(-Vdc)且无功功率。第一桥臂的输出电压V AN为0，第二桥臂的输出电压V BN为+Vdc，共模电压为Vdc/2。
图8是根据本申请另一个实施例的逆变器第五工作模式示意图。参见图8，在第五工作模式下，逆变器的交流输出与直流输入实现解耦，即电网G不与光伏电池板PV直接相连，由开关器件S5和二极管D2、D3、D5及D6构成双向续流回路，逆变器输出0电平，共模电压维持Vdc/2不变(见参考文献L.Zhang,K.Sun,Y.Xing and M.Xing,"H6 Transformerless Full-Bridge PV Grid-Tied Inverters"in IEEE Transactions on Power Electronics,vol.29,no.3,pp.1229-1238,March 2014.doi:10.1109/TPEL.2013.2260178)。其中，在输出0电平且电流为正时，由点A经L1、L2、二极管D5、开关器件S5和二极管D3构成一条续流回路；在输出0电平且电流为负时，由点B经L2、L1、二极管D2、开关器件S5和二极管D6构成另一条续流回路。
本申请提供的高效非隔离型三电平并网逆变器，拓扑结构中有功支路和无功支路是互补的，也就是说，有功支路中的所有有源开关器件在无功支路中不复用，因此所有有源开关器件均不需要反并联二极管，节省了成本。
本申请中，可选的，滤波器包括第一电感L1和第二电感L2；第一电感L1具有第一端和第二端，第一端连接所述选通电路模块的第三端(A点)，第二电感L2具有第一端和第二端，第二端连接所述选通电路模块的第四端(B点)，第一电感L1的第二端和第二电感L2的第一端连接在电网G的两端。优选地，第一电感L1和第二电感L2的感抗相同。
本实施例提供的上述逆变器，共模电压在各个模态均能保持一个恒定值，有效地解决了非隔离型三电平并网逆变器产生漏电流的问题，可以达到与HERIC拓扑结构相同的漏电流抑制效果。与HERIC拓扑结构从器件数量上相比，少了一个有源开关，由于逆变器系统中，有源开关的成本占据了较大的比例，因此，节省了系统成本。另外，采用单极性脉冲宽度调制方式，输出电流纹波小，输出电能质量高。
本申请提供的高效非隔离型三电平并网逆变器，为便于描述，以应用于光伏发电系统为例进行阐述，但不局限应用于光伏发电系统。
以上所述，仅为本申请较佳的具体实施方式，但本申请的保护范围并不局限于此，任何熟悉本技术领域的技术人员在本申请揭露的技术范围内，可轻易想到的变化或替换，都应涵盖在本申请的保护范围之内。因此，本申请的保护范围应该以权利要求的保护范围为准。

Claims (10)

  1. 一种选通单元，包括：
    一个选通电路模块，具有第一端、第二端、第三端和第四端共四个端子，且在控制信号的控制下提供五种工作模式：
    第一工作模式下，控制导通所述第一端和第三端之间的连接，以及导通所述第四端和第二端之间的连接，并断开四个端子中的其它端到端之间的连接；
    第二工作模式下，控制单向导通所述第二端至第四端之间的连接，以及单向导通所述第三端至第一端之间的连接，并断开四个端子中的其它端到端之间的连接；
    第三工作模式下，控制导通所述第一端和第四端之间的连接，以及导通所述第三端和第二端之间的连接，并断开四个端子中的其它端到端之间的连接；
    第四工作模式下，控制单向导通所述第二端至第三端之间的连接，以及单向导通所述第四端至第一端之间的连接，并断开四个端子中的其它端到端之间的连接；
    第五工作模式下，控制断开所述第一端和第二端之间的连接，导通所述第三端和第四端之间的连接且构成续流回路，并断开四个端子中的其它端到端之间的连接。
  2. 根据权利要求1所述的选通单元，其特征在于，所述选通电路模块包括：第一电路子模块、第二电路子模块、第三电路子模块；
    所述第一电路子模块和第二电路子模块均具有第一端、第二端和第三端；所述第三电路子模块具有第一端、第二端、第三端和第四端；
    所述第一电路子模块的第一端、所述第二电路子模块的第一端和所述第三电路子模块的第一端同时连接所述选通电路模块的第一端；
    所述第一电路子模块的第二端、所述第二电路子模块的第二端和所述第三电路子模块的第二端同时连接所述选通电路模块的第二端；
    所述第一电路子模块的第三端连接所述选通电路模块的第三端；
    所述第二电路子模块的第三端连接所述选通电路模块的第四端；
    所述第三电路子模块的第三端和第四端分别连接所述选通电路模块的第三端和第四端；
    所述第一电路子模块在控制信号的控制下提供三种工作状态：仅导通第一端和第三端之间的连接；仅导通第二端和第三端之间的连接；断开所有端到端之间的连接；
    所述第二电路子模块在控制信号的控制下提供三种工作状态：仅导通第一端和第三端之间的连接；仅导通第二端和第三端之间的连接；断开所有端到端之间的连接；
    所述第三电路子模块在控制信号的控制下提供四种工作状态：仅导通第三端至第一端之间的连接以及第二端至第四端之间的连接；仅导通第四端至第一端之间的连接以及第二端至第三端之间的连接；仅导通第三端和第四端之间的连接；断开所有端到端之间的连接。
  3. 根据权利要求2所述的选通单元，其特征在于，所述第一电路子模块包括：第一开关和第二开关；
    所述第一开关具有第一端和第二端，分别连接所述选通电路模块的第一端和第三端；
    所述第二开关具有第一端和第二端，所述第二开关的第一端同时连接所述第一开关的第二端和所述选通电路模块的第三端，所述第二开关的第二端连接所述选通电路模块的第二端。
  4. 根据权利要求3所述的选通单元，其特征在于，所述第一开关和第二开关均为导通和关断都可控的全控型器件反向并联一个单向导通器件。
  5. 根据权利要求2所述的选通单元，其特征在于，所述第二电路子模块包括：第三开关和第四开关；
    所述第三开关具有第一端和第二端，分别连接所述选通电路模块的第一端和第四端；
    所述第四开关具有第一端和第二端，所述第四开关的第一端同时 连接所述第三开关的第二端和所述选通电路模块的第四端，所述第四开关的第二端连接所述选通电路模块的第二端。
  6. 根据权利要求5所述的选通单元，其特征在于，所述第三开关和第四开关均为导通和关断都可控的全控型器件反向并联一个单向导通器件。
  7. 根据权利要求2所述的选通单元，其特征在于，所述第三电路子模块包括：第一二极管、第二二极管、第三二极管、第四二极管、第五二极管、第六二极管和第五开关；
    所述第一二极管的负极连接所述选通电路模块的第一端；
    所述第二二极管的负极连接所述第五二极管的负极；
    所述第二二极管的正极连接所述第三二极管的负极；
    所述第三二极管的正极连接所述第六二极管的正极；
    所述第四二极管的正极连接所述选通电路模块的第二端；
    所述第五二极管的正极连接所述第六二极管的负极；
    所述第五开关具有第一端和第二端；
    所述第二二极管和第五二极管的公共端同时连接所述第一二极管的正极和所述第五开关的第一端，所述第二二极管和第三二极管的公共端连接所述选通电路模块的第三端，所述第三二极管和第六二极管的公共端同时连接所述第四二极管的负极和所述第五开关的第二端，所述第五二极管和第六二极管的公共端连接所述选通电路模块的第四端。
  8. 根据权利要求7所述的选通单元，其特征在于，所述第五开关为导通和关断都可控的全控型器件反向并联一个单向导通器件。
  9. 一种高效非隔离型三电平并网逆变器，其特征在于，包括：
    一个滤波器和一个如权利要求1-8中任一项所述的选通单元，所述滤波器包括第一电感和第二电感，且均具有第一端和第二端；
    所述第一电感的第一端连接所述选通电路模块的第三端；
    所述第二电感的第二端连接所述选通电路模块的第四端；
    所述第一电感的第二端和所述第二电感的第一端连接在电网的两端。
  10. 根据权利要求9所述的非隔离型三电平并网逆变器，其特征在于，还包括：一个直流电源和一个电容；
    所述直流电源的正极连接所述选通电路模块的第一端；
    所述直流电源的负极连接所述选通电路模块的第二端；
    所述电容并联连接在所述直流电源的两端。
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