Non-isolated inverter circuit with zero switching loss and reduced on-state loss and modulation method

Abstract

The application discloses a zero-switching-loss non-isolation inverter circuit with reduced on-state loss and a modulation method, and belongs to the technical field of soft switching of inverter circuits. The inverter circuit comprises a direct-current capacitor branch, a main switch group, a freewheeling diode group and an auxiliary resonance network; by adding a resonance network composed of a full-control switch, a resonance capacitor and a resonance inductor, under a corresponding modulation method, on one hand, zero-current turn-on and zero-current turn-off of the main switch group S1-S6, zero-current turn-on and zero-current turn-off of the auxiliary switch S 5a and S 6a , zero-current turn-off of the auxiliary diode D a1 and D a2 , and zero-current turn-off of the freewheeling diode D f1 and D f2 can be realized; on the other hand, the conduction loss of the power switch in the main switch group is not additionally increased, and the maximum current in the whole circuit is the amplitude of the resonance current; the application enables the non-isolation grid-connected inverter to realize zero-switching-loss operation, is beneficial to improving the switching frequency, miniaturizing passive components and integrating a prototype, and is suitable for application of small and medium power non-isolation grid-connected systems.

Description

Technical Field

[0001] This invention belongs to the field of soft-switching technology for inverter circuits, specifically relating to a zero-switching-loss non-isolated inverter circuit and modulation method for reducing conduction losses. Background Technology

[0002] In recent years, the proportion of photovoltaic power generation in new energy power generation has been increasing year by year. Non-isolated inverter circuits are low in cost, high in efficiency, and small in size, making them suitable for distributed photovoltaic power generation applications. Parasitic capacitance exists between the photovoltaic panel and the ground, and the common-mode leakage current generated by the high-frequency operation of the inverter can cause serious safety problems. An effective measure to suppress leakage current is to maintain a constant common-mode voltage. Typically, inverter circuits use hard switching, and switching losses limit the increase in switching frequency, resulting in larger and more expensive passive components, thus limiting the increase in power density. Soft-switching technology can reduce or even eliminate switching losses and is an important way to improve inverter efficiency and promote its high-frequency operation.

[0003] Patent CN 104242719B discloses a lossless full-bridge non-isolated photovoltaic grid-connected inverter and its switching control timing, which can enable power devices to operate with zero switching losses and maintain a constant common-mode voltage to eliminate leakage current. The drawback is that the resonant network doubles the current amplitude on the main switch, which increases the power level of the main switch and leads to increased conduction losses. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a zero-switching-loss non-isolated inverter circuit and its modulation method for reducing conduction losses.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] The zero-switching-loss non-isolated inverter circuit with reduced conduction losses includes a DC capacitor branch, a main switch group, a freewheeling diode group, and a resonant network. The DC capacitor branch maintains a stable input voltage, while the freewheeling diode group and the resonant network enable zero-current switching of the power switches in the main switch group.

[0007] Furthermore, the DC capacitor branch includes a first DC capacitor C. dc1 Second DC capacitor C dc2 .

[0008] Furthermore, the main switch group includes: a parallel combination of a first power switch S1 and a first power diode D1, a parallel combination of a second power switch S2 and a second power diode D2, a parallel combination of a third power switch S3 and a third power diode D3, a parallel combination of a fourth power switch S4 and a fourth power diode D4, a parallel combination of a fifth power switch S5 and a fifth power diode D5, and a parallel combination of a sixth power switch S6 and a sixth power diode D6.

[0009] Furthermore, the freewheeling diode group includes a first freewheeling diode D. f1 Second freewheeling diode D f2 .

[0010] Furthermore, the resonant network includes: a fifth auxiliary power switch S 5a The sixth auxiliary power switch S 6a First auxiliary diode D a1 Second auxiliary diode D a2 Fifth auxiliary resonant capacitor C 5a Fifth auxiliary resonant inductor L 5a The sixth auxiliary resonant capacitor C 6a and the sixth auxiliary resonant inductor L 6a .

[0011] Furthermore, the first DC capacitor C dc1 The positive terminal is connected to the positive output terminal of the solar cell PV, the fifth power switch S5, and the fifth auxiliary switch S. 5a The drain of the fully controlled device and the cathode of the fifth power diode D5; the first DC capacitor C dc1 The negative terminal is connected to the second DC capacitor C. dc2 The positive terminal, the fifth auxiliary resonant inductor L 5a One end, and the sixth auxiliary resonant inductor L 6a One end;

[0012] The second DC capacitor C dc2 The negative electrode is connected to the negative output terminal of the solar cell PV, the source of the sixth power switch S6, and the cathode of the diode in the sixth auxiliary switch S6;

[0013] The source of the fifth power switch S5 is connected to the first auxiliary diode D. a1 and the first freewheeling diode D f1 The cathode of the first power switch S1 and the drain of the third power switch S3, and the cathode of the first power diode D1 and the third power diode D3.

[0014] The drain of the sixth power switch S6 is connected to the second auxiliary diode D.a2 Second freewheeling diode D f2 The anode of the second power switch S2 and the source of the fourth power switch S4, and the anode of the second power diode D2 and the fourth power diode D4;

[0015] The fifth auxiliary resonant capacitor C 5a One end is connected to the first auxiliary diode D a1 The anode and the fifth auxiliary switch S 5a The cathode of the diode; the fifth auxiliary resonant capacitor C 5a The other end is connected to the first freewheeling diode D f1 The anode and the fifth auxiliary resonant inductor L 5a The other end;

[0016] The sixth auxiliary resonant capacitor C 6a One end is connected to the second auxiliary diode D a2 The cathode and the fifth auxiliary switch S 5a The drain of the fully controlled device; the sixth auxiliary resonant capacitor C 6a The other end is connected to the second freewheeling diode D. f2 The cathode and the sixth auxiliary resonant inductor L 6a The other end.

[0017] Furthermore, only one DC capacitor is provided in the DC capacitor branch;

[0018] The main switch group comprises: a parallel combination of a first power switch S1 and a first power diode D1, a parallel combination of a second power switch S2 and a second power diode D2, a parallel combination of a third power switch S3 and a third power diode D3, a parallel combination of a fourth power switch S4 and a fourth power diode D4, a parallel combination of a fifth power switch S5 and a fifth power diode D5, and a parallel combination of a sixth power switch S6 and a sixth power diode D6.

[0019] The freewheeling diode group includes a first freewheeling diode D. f1 Second freewheeling diode D f2 ;

[0020] The resonant network includes a fifth auxiliary power switch S. 5a The sixth auxiliary power switch S 6a First auxiliary diode D a1 Second auxiliary diode D a2 Fifth auxiliary resonant capacitor C 5a Auxiliary resonant inductor L a and the sixth auxiliary resonant capacitor C 6a .

[0021] Furthermore, the DC capacitor branch includes a first DC capacitor C. dc1 and the first DC capacitor C dc2 ;

[0022] The main switch group includes: a parallel combination of a first power switch S1 and a first power diode D1, a parallel combination of a second power switch S2 and a second power diode D2, a parallel combination of a third power switch S3 and a third power diode D3, a parallel combination of a fourth power switch S4 and a fourth power diode D4, a parallel combination of a fifth power switch S5 and a fifth power diode D5, a parallel combination of a sixth power switch S6 and a sixth power diode D6, a seventh power diode D7, and an eighth power diode D8;

[0023] The freewheeling diode group includes a first freewheeling diode D. f1 Second freewheeling diode D f2 ;

[0024] The resonant network includes: a fifth auxiliary power switch S 5a The sixth auxiliary power switch S 6a First auxiliary diode D a1 Second auxiliary diode D a2 Fifth auxiliary resonant capacitor C 5a Auxiliary resonant inductor L a and the sixth auxiliary resonant capacitor C 6a .

[0025] Furthermore, the first power switch S1, the second power switch S2, the third power switch S3, the fourth power switch S4, the fifth power switch S5, and the sixth power switch S6 are fully controllable devices; the fifth auxiliary power switch S... 5a and the sixth auxiliary power switch S 6a It is a fully controlled device that does not contain anti-parallel diodes.

[0026] The modulation method of the above circuit includes:

[0027] The first power switch S1 and the fourth power switch S4 are always on during the positive half-cycle of the grid current and always off during the negative half-cycle. The second power switch S2 and the third power switch S3 are always on during the negative half-cycle of the grid current and always off during the positive half-cycle.

[0028] There is a certain dead time between the first power switch S1, the second power switch S2, the third power switch S3 and the fourth power switch S4.

[0029] The fifth power switch S5 and the sixth power switch S6 operate at high frequency in unipolar SPWM mode throughout the entire cycle. The fifth auxiliary power switch S... 5a and the sixth auxiliary power switch S 6a It operates at high frequency throughout the entire cycle;

[0030] Fifth auxiliary switch S 5a The turn-on of the transistor is delayed until the turn-on of the fifth power switch S5, and both are turned off simultaneously.

[0031] Sixth auxiliary switch S 6a The turn-on of the transistor is delayed until the turn-on of the sixth power switch S6, and both are turned off simultaneously.

[0032] The beneficial effects of this invention are:

[0033] 1. In the inverter circuit of this invention, the clamping structure can fix the common-mode voltage at a constant value, which can eliminate leakage current in non-isolated grid-connected inverter systems;

[0034] 2. The inverter circuit of this invention utilizes an auxiliary resonant network and a freewheeling diode array to achieve zero switching loss operation of power devices, breaking through the efficiency limitation on switching frequency;

[0035] 3. The operating mode of the inverter circuit of this invention determines that the introduction of the resonant network will not increase the current amplitude and conduction loss of the main switch. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 This is a schematic diagram of the main circuit structure of Embodiment 1 of the present invention;

[0038] Figure 2 This is a schematic diagram of the modulation method in Embodiment 1 of the present invention;

[0039] Figure 3 This is the theoretical working waveform diagram of Embodiment 1 of the present invention on the high-frequency switching cycle scale;

[0040] Figure 4 These are schematic diagrams of various modes in Embodiment 1 of the present invention;

[0041] Figure 5 This is the simulated operating waveform of the electrical component in Embodiment 1 of the present invention;

[0042] Figure 6These are the experimental waveforms of the electrical components in Embodiment 1 of the present invention;

[0043] Figure 7 This is a schematic diagram of the main circuit of Embodiment 2 of the present invention;

[0044] Figure 8 This is a schematic diagram of the main circuit of Embodiment 3 of the present invention.

[0045] In the diagram, u g U is the grid voltage; PV L1 is the output voltage of the solar panel; L2 and L1 are the grid-connected filter inductors; C f For the input filter capacitor; i g This is the grid-connected current. Detailed Implementation

[0046] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0047] Example 1

[0048] like Figure 1 As shown, a zero-switching-loss non-isolated inverter circuit with reduced conduction losses includes a DC capacitor branch 1, a main switch group 2, a freewheeling diode group 3, and a resonant network 4. The DC capacitor branch 1 is used to maintain input voltage stability. Under appropriate modulation methods, the freewheeling diode group 3 and the resonant network 4 can incorporate a fully controlled switch, a resonant capacitor, and a resonant inductor, enabling zero-current switching of the power switches in the main switch group 2. The DC capacitor branch 1 includes a first DC capacitor C. dc1 Second DC capacitor C dc2 ;

[0049] The main switch group 2 includes: a parallel combination of a first power switch S1 and a first power diode D1, a parallel combination of a second power switch S2 and a second power diode D2, a parallel combination of a third power switch S3 and a third power diode D3, a parallel combination of a fourth power switch S4 and a fourth power diode D4, a parallel combination of a fifth power switch S5 and a fifth power diode D5, and a parallel combination of a sixth power switch S6 and a sixth power diode D6; wherein, the first power switch S1, the second power switch S2, the third power switch S3, the fourth power switch S4, the fifth power switch S5, and the sixth power switch S6 are fully controllable devices;

[0050] Freewheeling diode group 3 includes: a first freewheeling diode Df1 Second freewheeling diode D f2 ;

[0051] Resonant network 4 includes: a fifth auxiliary power switch S 5a The sixth auxiliary power switch S 6a First auxiliary diode D a1 Second auxiliary diode D a2 Fifth auxiliary resonant capacitor C 5a Fifth auxiliary resonant inductor L 5a The sixth auxiliary resonant capacitor C 6a and the sixth auxiliary resonant inductor L 6a Fifth auxiliary power switch S 5a and the sixth auxiliary power switch S 6a It is a fully controlled device that does not contain anti-parallel diodes.

[0052] First DC capacitor C dc1 The positive terminal is connected to the positive output terminal of the solar cell PV, the fifth power switch S5, and the fifth auxiliary switch S. 5a The drain of the fully controlled device and the cathode of the fifth power diode D5; the first DC capacitor C dc1 The negative terminal is connected to the second DC capacitor C. dc2 The positive terminal, the fifth auxiliary resonant inductor L 5a One end, and the sixth auxiliary resonant inductor L 6a One end;

[0053] Second DC capacitor C dc2 The negative electrode is connected to the negative output terminal of the solar cell PV, the source of the sixth power switch S6, and the cathode of the diode in the sixth auxiliary switch S6;

[0054] The source of the fifth power switch S5 is connected to the first auxiliary diode D. a1 and the first freewheeling diode D f1 The cathode of the first power switch S1 and the drain of the third power switch S3, and the cathode of the first power diode D1 and the third power diode D3.

[0055] The drain of the sixth power switch S6 is connected to the second auxiliary diode D. a2 Second freewheeling diode D f2 The anode of the second power switch S2 and the source of the fourth power switch S4, and the anode of the second power diode D2 and the fourth power diode D4;

[0056] Fifth auxiliary resonant capacitor C 5a One end is connected to the first auxiliary diode D a1 The anode and the fifth auxiliary switch S5a The cathode of the diode; the fifth auxiliary resonant capacitor C 5a The other end is connected to the first freewheeling diode D f1 The anode and the fifth auxiliary resonant inductor L 5a The other end;

[0057] Sixth auxiliary resonant capacitor C 6a One end is connected to the second auxiliary diode D a2 The cathode and the fifth auxiliary switch S 5a The drain of the fully controlled device; the sixth auxiliary resonant capacitor C 6a The other end is connected to the second freewheeling diode D. f2 The cathode and the sixth auxiliary resonant inductor L 6a The other end.

[0058] like Figure 2 As shown, the modulation method of this circuit is as follows: the first power switch S1 and the fourth power switch S4 are always on during the positive half-cycle of the grid current and always off during the negative half-cycle; the second power switch S2 and the third power switch S3 are always on during the negative half-cycle of the grid current and always off during the positive half-cycle; to ensure reliable commutation, a certain dead time is left between the first power switch S1 and the second power switch S2, the third power switch S3 and the fourth power switch S4; the fifth power switch S5 and the sixth power switch S6 operate at high frequency in unipolar SPWM mode throughout the entire cycle; the fifth auxiliary power switch S... 5a and the sixth auxiliary power switch S 6a High-frequency switching operation throughout the entire cycle; fifth auxiliary switch S 5a The conduction of the sixth auxiliary switch is delayed compared to the conduction of the fifth power switch S5, and both are turned off simultaneously; 6a The turn-on of the transistor is delayed until the turn-on of the sixth power switch S6, and both are turned off simultaneously.

[0059] Figure 3 This is the theoretical working waveform diagram of Embodiment 1 of the present invention on the high-frequency switching cycle scale. Figure 4 (a) to Figure 4 (h) is the equivalent operating mode diagram of modes 1 to 8 in one switching cycle of Embodiment 1 of the present invention;

[0060] To further verify the effectiveness of the circuit and modulation method in this embodiment, a specific example is given below.

[0061] Solar panel voltage U PV =400V, mains voltage u g =220VRMS, power grid frequency f g =50Hz, rated power P=1000W, DC bus capacitance C dc1=C dc2 =470μF; Filter inductor L1=L2=0.5mH; Filter capacitor C1=2.2μF; Solar panel parasitic capacitance to ground C pv1 =C pv2 =0.15μF; switching frequency f = 50kHz, resonant parameter L r =12μH,C r =47nF.

[0062] Figure 5 (a), (b), (c), (d), and (e) respectively show the resonant voltage and resonant current, the voltage and current of power switch S5, and the voltage and current of auxiliary switch S. 5a Voltage and current, auxiliary diode D a1 The voltage, current and freewheeling diode D f1 Simulated working waveforms of voltage and current; Figure 6 (a), (b), (c), and (d) in the diagram represent the main power switch S5 and the auxiliary power switch S6. 5a Auxiliary power diode D a1 and freewheeling power diode D f1 The experimental waveform;

[0063] from Figure 5 (a) to Figure 5 (e) Figure 6 (a) to Figure 6 The implementation results of (d) show that, Figure 1 The circuit structure shown is compatible with Figure 2 With the modulation method shown, zero-current turn-on and zero-current turn-off of the fifth power switch S5 and the sixth power switch S6 can be achieved, and the fifth auxiliary power switch S... 5a The sixth auxiliary power switch S 6a Zero-current turn-on and zero-current turn-off are achieved by the first auxiliary power switch D. a1 Second auxiliary power diode D a2 Zero-current turn-off is achieved by the first auxiliary power diode D. f1 Second auxiliary power diode D f2 The zero-current turn-off eliminates the reverse recovery problem in the power diodes, and the current on the power switching transistors of the main switching group does not exceed the grid current. It also ensures that the common-mode voltage of the inverter is always half of the battery voltage during the power transmission, resonance and freewheeling phases.

[0064] Example 2

[0065] like Figure 7 As shown, the main circuit includes: a DC capacitor branch 1, a main switch group 2, a freewheeling diode group 3, and a resonant network 4; the DC capacitor branch 1 includes a DC capacitor C.dc The main switch group 2 comprises: a parallel combination of a first power switch S1 and a first power diode D1, a parallel combination of a second power switch S2 and a second power diode D2, a parallel combination of a third power switch S3 and a third power diode D3, a parallel combination of a fourth power switch S4 and a fourth power diode D4, a parallel combination of a fifth power switch S5 and a fifth power diode D5, and a parallel combination of a sixth power switch S6 and a sixth power diode D6; the freewheeling diode group 3 comprises a first freewheeling diode D... f1 Second freewheeling diode D f2 The resonant network 4 includes a fifth auxiliary power switch S. 5a The sixth auxiliary power switch S 6a First auxiliary diode D a1 Second auxiliary diode D a2 Fifth auxiliary resonant capacitor C 5a Auxiliary resonant inductor L a and the sixth auxiliary resonant capacitor C 6a .

[0066] DC capacitor C dc The positive terminal is connected to the positive output terminal of the solar cell PV, the fifth power switch S5, and the fifth auxiliary switch S. 5a The drain of a fully controllable device;

[0067] DC capacitor C dc The negative terminal is connected to the negative output terminal of the solar cell PV, the source of the sixth power switch S6, and the cathode of the diode in the sixth auxiliary switch S6.

[0068] The source of the fifth power switch S5 is connected to the first auxiliary diode D. a1 and the first freewheeling diode D f1 The cathode of the first power switch S1 and the drain of the third power switch S3, and the cathode of the first power diode D1 and the third power diode D3.

[0069] The drain of the sixth power switch S6 is connected to the second auxiliary diode D. a2 Second freewheeling diode D f2 The anode of the second power switch S2 and the source of the fourth power switch S4, and the anode of the second power diode D2 and the fourth power diode D4;

[0070] Fifth auxiliary resonant capacitor C 5a One end is connected to the first auxiliary diode D a1 The anode and the fifth auxiliary switch S 5a The cathode of the diode; the fifth auxiliary resonant capacitor C 5aThe other end is connected to the first freewheeling diode D f1 anode and auxiliary resonant inductor L a The other end;

[0071] Sixth auxiliary resonant capacitor C 6a One end is connected to the second auxiliary diode D a2 The cathode and the fifth auxiliary switch S 5a The drain of the fully controlled device; the sixth auxiliary resonant capacitor C 6a The other end is connected to the second freewheeling diode D. f2 Cathode and auxiliary resonant inductor L a The other end.

[0072] The circuit modulation method in this embodiment is the same as that in Embodiment 1. Specifically, the first power switch S1 and the fourth power switch S4 are continuously on during the positive half-cycle of the grid current and continuously off during the negative half-cycle. The second power switch S2 and the third power switch S3 are continuously on during the negative half-cycle of the grid current and continuously off during the positive half-cycle. To ensure reliable commutation, a certain dead time is provided between the first power switch S1 and the second power switch S2, the third power switch S3 and the fourth power switch S4. The fifth power switch S5 and the sixth power switch S6 operate at high frequency in unipolar SPWM mode throughout the entire cycle. The fifth auxiliary power switch S... 5a and the sixth auxiliary power switch S 6a It operates at high frequency throughout the entire cycle. Fifth auxiliary switch S 5a The conduction of the sixth auxiliary switch is delayed compared to the conduction of the fifth power switch S5, and both are turned off simultaneously; 6a The turn-on of the transistor is delayed until the turn-on of the sixth power switch S6, and both are turned off simultaneously.

[0073] exist Figure 7 The circuit structure shown is compatible with Figure 2 With the modulation method shown, zero-current turn-on and zero-current turn-off of the fifth power switch S5 and the sixth power switch S6 can be achieved, and the fifth auxiliary power switch S... 5a The sixth auxiliary power switch S 6a Zero-current turn-on and zero-current turn-off are achieved by the first auxiliary power switch D. 1a Second auxiliary power diode D 2a Zero-current turn-off is achieved by the first auxiliary power diode D. f1 Second auxiliary power diode D f2 The zero-current turn-off eliminates the reverse recovery problem in the power diodes, and the current on the power switching transistors of the main switch group does not exceed the grid current.

[0074] Example 3

[0075] Figure 8 The diagram shows the main circuit of this embodiment, including a DC capacitor branch 1, a main switch group 2, a freewheeling diode group 3, and a resonant network 4; the DC capacitor branch 1 includes a first DC capacitor C. dc1 First DC capacitor C dc2 The main switch group 2 includes a parallel combination of a first power switch S1 and a first power diode D1, a parallel combination of a second power switch S2 and a second power diode D2, a parallel combination of a third power switch S3 and a third power diode D3, a parallel combination of a fourth power switch S4 and a fourth power diode D4, a parallel combination of a fifth power switch S5 and a fifth power diode D5, a parallel combination of a sixth power switch S6 and a sixth power diode D6, a seventh power diode D7, and an eighth power diode D8; the freewheeling diode group 3 includes a first freewheeling diode D... f1 Second freewheeling diode D f2 The resonant network 4 includes: a fifth auxiliary power switch S. 5a The sixth auxiliary power switch S 6a First auxiliary diode D a1 Second auxiliary diode D a2 Fifth auxiliary resonant capacitor C 5a Auxiliary resonant inductor L a and the sixth auxiliary resonant capacitor C 6a .

[0076] First DC capacitor C dc1 The positive terminal is connected to the positive output terminal of the solar cell PV, the fifth power switch S5, and the fifth auxiliary switch S. 5a The drain of the fully controlled device; the first DC capacitor C dc1 The negative terminal is connected to the second DC capacitor C. dc2 The positive terminal of the seventh power diode, the anode of the seventh power diode, and the cathode of the eighth power diode;

[0077] Second DC capacitor C dc2 The negative terminal is connected to the negative output terminal of the solar cell PV, the source of the sixth power switch S6, and the cathode of the diode in the sixth auxiliary switch S6.

[0078] The source of the fifth power switch S5 is connected to the first auxiliary diode D. a1 First freewheeling diode D f1 The cathode of the seventh power switch, the drain of the first power switch S1 and the third power switch S3, and the cathode of the first power diode D1 and the third power diode D3.

[0079] The drain of the sixth power switch S6 is connected to the second auxiliary diode D. a2Second freewheeling diode D f2 And the anode of the eighth power diode, the source of the second power switch S2 and the fourth power switch S4, and the anode of the second power diode D2 and the fourth power diode D4;

[0080] Fifth auxiliary resonant capacitor C 5a One end is connected to the first auxiliary diode D a1 The anode and the fifth auxiliary switch S 5a The cathode of the diode; the fifth auxiliary resonant capacitor C 5a The other end is connected to the first freewheeling diode D f1 anode and auxiliary resonant inductor L a The other end;

[0081] Sixth auxiliary resonant capacitor C 6a One end is connected to the second auxiliary diode D a2 The cathode and the fifth auxiliary switch S 5a The drain of the fully controlled device; the sixth auxiliary resonant capacitor C 6a The other end is connected to the second freewheeling diode D. f2 Cathode and auxiliary resonant inductor L a The other end.

[0082] The modulation method in this embodiment is the same as that in Embodiment 1, specifically: the first power switch S1 and the fourth power switch S4 are continuously on during the positive half-cycle of the grid current and continuously off during the negative half-cycle; the second power switch S2 and the third power switch S3 are continuously on during the negative half-cycle of the grid current and continuously off during the positive half-cycle; to ensure reliable commutation, a certain dead time is provided between the first power switch S1 and the second power switch S2, the third power switch S3 and the fourth power switch S4. The fifth power switch S5 and the sixth power switch S6 operate at high frequency in unipolar SPWM mode throughout the entire cycle, and the fifth auxiliary power switch S... 5a and the sixth auxiliary power switch S 6a It operates at high frequency throughout the entire cycle. Fifth auxiliary switch S 5a The conduction of the sixth auxiliary switch is delayed compared to the conduction of the fifth power switch S5, and both are turned off simultaneously; 6a The turn-on of the transistor is delayed until the turn-on of the sixth power switch S6, and both are turned off simultaneously.

[0083] exist Figure 8 The circuit structure shown is compatible with Figure 2 With the modulation method shown, zero-current turn-on and zero-current turn-off of the fifth power switch S5 and the sixth power switch S6 can be achieved, and the fifth auxiliary power switch S... 5a The sixth auxiliary power switch S 6aZero-current turn-on and zero-current turn-off are achieved by the first auxiliary power switch D. 1a Second auxiliary power diode D 2a Zero-current turn-off, enabling the first freewheeling diode D f1 Second freewheeling diode D f2 The zero-current turn-off eliminates the reverse recovery problem in the power diodes, and the current on the power switching transistors of the main switching group does not exceed the grid current. It also ensures that the common-mode voltage of the inverter is always half of the battery voltage during the power transmission, resonance and freewheeling phases.

[0084] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0085] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A zero-switching-loss non-isolated inverter circuit with reduced conduction losses, characterized in that, It includes a DC capacitor branch (1), a main switch group (2), a freewheeling diode group (3), and a resonant network (4); among which, the DC capacitor branch (1) can maintain the stability of the input voltage, and the freewheeling diode group (3) and the resonant network (4) can enable the power switch tubes in the main switch group (2) to switch with zero current. The DC capacitor branch (1) includes a first DC capacitor C dc1 Second DC capacitor C dc2 ; The main switch group (2) includes: a parallel combination of a first power switch S1 and a first power diode D1, a parallel combination of a second power switch S2 and a second power diode D2, a parallel combination of a third power switch S3 and a third power diode D3, a parallel combination of a fourth power switch S4 and a fourth power diode D4, a parallel combination of a fifth power switch S5 and a fifth power diode D5, and a parallel combination of a sixth power switch S6 and a sixth power diode D6. The freewheeling diode group (3) includes a first freewheeling diode D. f1 Second freewheeling diode D f2 ; The resonant network (4) includes: a fifth auxiliary power switch S 5a The sixth auxiliary power switch S 6a First auxiliary diode D a1 Second auxiliary diode D a2 Fifth auxiliary resonant capacitor C 5a Fifth auxiliary resonant inductor L 5a The sixth auxiliary resonant capacitor C 6a and the sixth auxiliary resonant inductor L 6a ; The first DC capacitor C dc1 The positive terminal is connected to the positive output terminal of the solar cell PV, the fifth power switch S5, and the fifth auxiliary switch S. 5a The drain of the fully controlled device and the cathode of the fifth power diode D5; the first DC capacitor C dc1 The negative terminal is connected to the second DC capacitor C. dc2 The positive terminal, the fifth auxiliary resonant inductor L 5a One end, and the sixth auxiliary resonant inductor L 6a One end; The second DC capacitor C dc2 The negative electrode is connected to the negative output terminal of the solar cell PV, the source of the sixth power switch S6, and the cathode of the diode in the sixth auxiliary switch S6; The source of the fifth power switch S5 is connected to the first auxiliary diode D. a1 and the first freewheeling diode D f1 The cathode of the first power switch S1 and the drain of the third power switch S3, and the cathode of the first power diode D1 and the third power diode D3. The drain of the sixth power switch S6 is connected to the second auxiliary diode D. a2 Second freewheeling diode D f2 The anode of the second power switch S2 and the source of the fourth power switch S4, and the anode of the second power diode D2 and the fourth power diode D4; The fifth auxiliary resonant capacitor C 5a One end is connected to the first auxiliary diode D a1 The anode and the fifth auxiliary switch S 5a The cathode of the diode; the fifth auxiliary resonant capacitor C 5a The other end is connected to the first freewheeling diode D f1 The anode and the fifth auxiliary resonant inductor L 5a The other end; The sixth auxiliary resonant capacitor C 6a One end is connected to the second auxiliary diode D a2 The cathode and the fifth auxiliary switch S 5a The drain of the fully controlled device; the sixth auxiliary resonant capacitor C 6a The other end is connected to the second freewheeling diode D. f2 The cathode and the sixth auxiliary resonant inductor L 6a The other end.

2. The zero-switching-loss non-isolated inverter circuit with reduced conduction losses according to claim 1, characterized in that, The first power switch S1, the second power switch S2, the third power switch S3, the fourth power switch S4, the fifth power switch S5, and the sixth power switch S6 are fully controllable devices; the fifth auxiliary power switch S6... 5a and the sixth auxiliary power switch S 6a It is a fully controlled device that does not contain anti-parallel diodes.

3. A zero-switching-loss non-isolated inverter circuit with reduced conduction losses, characterized in that, It includes a DC capacitor branch (1), a main switch group (2), a freewheeling diode group (3), and a resonant network (4); among which, the DC capacitor branch (1) can maintain the stability of the input voltage, and the freewheeling diode group (3) and the resonant network (4) can enable the power switch tubes in the main switch group (2) to switch with zero current. Only one DC capacitor is set in the DC capacitor branch (1); The main switch group (2) comprises: a parallel combination of a first power switch S1 and a first power diode D1, a parallel combination of a second power switch S2 and a second power diode D2, a parallel combination of a third power switch S3 and a third power diode D3, a parallel combination of a fourth power switch S4 and a fourth power diode D4, a parallel combination of a fifth power switch S5 and a fifth power diode D5, and a parallel combination of a sixth power switch S6 and a sixth power diode D6. The freewheeling diode group (3) includes a first freewheeling diode D. f1 Second freewheeling diode D f2 ; The resonant network (4) includes a fifth auxiliary power switch S. 5a The sixth auxiliary power switch S 6a First auxiliary diode D a1 Second auxiliary diode D a2 Fifth auxiliary resonant capacitor C 5a Auxiliary resonant inductor L a and the sixth auxiliary resonant capacitor C 6a ; DC capacitor C dc The positive terminal is connected to the positive output terminal of the solar cell PV, the fifth power switch S5, and the fifth auxiliary switch S. 5a The drain of a fully controllable device; DC capacitor C dc The negative terminal is connected to the negative output terminal of the solar cell PV, the source of the sixth power switch S6, and the cathode of the diode in the sixth auxiliary switch S6. The source of the fifth power switch S5 is connected to the first auxiliary diode D. a1 and the first freewheeling diode D f1 The cathode of the first power switch S1 and the drain of the third power switch S3, and the cathode of the first power diode D1 and the third power diode D3. The drain of the sixth power switch S6 is connected to the second auxiliary diode D. a2 Second freewheeling diode D f2 The anode of the second power switch S2 and the source of the fourth power switch S4, and the anode of the second power diode D2 and the fourth power diode D4; Fifth auxiliary resonant capacitor C 5a One end is connected to the first auxiliary diode D a1 The anode and the fifth auxiliary switch S 5a The cathode of the diode; the fifth auxiliary resonant capacitor C 5a The other end is connected to the first freewheeling diode D f1 anode and auxiliary resonant inductor L a The other end; Sixth auxiliary resonant capacitor C 6a One end is connected to the second auxiliary diode D a2 The cathode and the fifth auxiliary switch S 5a The drain of the fully controlled device; the sixth auxiliary resonant capacitor C 6a The other end is connected to the second freewheeling diode D. f2 Cathode and auxiliary resonant inductor L a The other end.

4. The zero-switching-loss non-isolated inverter circuit with reduced conduction losses according to claim 3, characterized in that, The first power switch S1, the second power switch S2, the third power switch S3, the fourth power switch S4, the fifth power switch S5, and the sixth power switch S6 are fully controllable devices; the fifth auxiliary power switch S6... 5a and the sixth auxiliary power switch S 6a It is a fully controlled device that does not contain anti-parallel diodes.

5. A zero-switching-loss non-isolated inverter circuit with reduced conduction losses, characterized in that, It includes a DC capacitor branch (1), a main switch group (2), a freewheeling diode group (3), and a resonant network (4); among which, the DC capacitor branch (1) can maintain the stability of the input voltage, and the freewheeling diode group (3) and the resonant network (4) can enable the power switch tubes in the main switch group (2) to switch with zero current. The DC capacitor branch (1) includes a first DC capacitor C dc1 Second DC capacitor C dc2 ; The main switch group (2) includes: a parallel combination of a first power switch S1 and a first power diode D1, a parallel combination of a second power switch S2 and a second power diode D2, a parallel combination of a third power switch S3 and a third power diode D3, a parallel combination of a fourth power switch S4 and a fourth power diode D4, a parallel combination of a fifth power switch S5 and a fifth power diode D5, a parallel combination of a sixth power switch S6 and a sixth power diode D6, a seventh power diode D7, and an eighth power diode D8; The freewheeling diode group (3) includes a first freewheeling diode D. f1 Second freewheeling diode D f2 ; The resonant network (4) includes: a fifth auxiliary power switch S 5a The sixth auxiliary power switch S 6a First auxiliary diode D a1 Second auxiliary diode D a2 Fifth auxiliary resonant capacitor C 5a Auxiliary resonant inductor L a and the sixth auxiliary resonant capacitor C 6a ; First DC capacitor C dc1 The positive terminal is connected to the positive output terminal of the solar cell PV, the fifth power switch S5, and the fifth auxiliary switch S. 5a The drain of the fully controlled device; the first DC capacitor C dc1 The negative terminal is connected to the second DC capacitor C. dc2 The positive terminal of the seventh power diode, the anode of the seventh power diode, and the cathode of the eighth power diode; Second DC capacitor C dc2 The negative terminal is connected to the negative output terminal of the solar cell PV, the source of the sixth power switch S6, and the cathode of the diode in the sixth auxiliary switch S6. The source of the fifth power switch S5 is connected to the first auxiliary diode D. a1 First freewheeling diode D f1 The cathode of the seventh power switch, the drain of the first power switch S1 and the third power switch S3, and the cathode of the first power diode D1 and the third power diode D3. The drain of the sixth power switch S6 is connected to the second auxiliary diode D. a2 Second freewheeling diode D f2 And the anode of the eighth power diode, the source of the second power switch S2 and the fourth power switch S4, and the anode of the second power diode D2 and the fourth power diode D4; Fifth auxiliary resonant capacitor C 5a One end is connected to the first auxiliary diode D a1 The anode and the fifth auxiliary switch S 5a The cathode of the diode; the fifth auxiliary resonant capacitor C 5a The other end is connected to the first freewheeling diode D f1 anode and auxiliary resonant inductor L a The other end; Sixth auxiliary resonant capacitor C 6a One end is connected to the second auxiliary diode D a2 The cathode and the fifth auxiliary switch S 5a The drain of the fully controlled device; the sixth auxiliary resonant capacitor C 6a The other end is connected to the second freewheeling diode D. f2 Cathode and auxiliary resonant inductor L a The other end.

6. The zero-switching-loss non-isolated inverter circuit with reduced conduction losses according to claim 5, characterized in that, The first power switch S1, the second power switch S2, the third power switch S3, the fourth power switch S4, the fifth power switch S5, and the sixth power switch S6 are fully controllable devices; the fifth auxiliary power switch S6... 5a and the sixth auxiliary power switch S 6a It is a fully controlled device that does not contain anti-parallel diodes.

7. The modulation method of the circuit according to any one of claims 1-6, characterized in that, include: The first power switch S1 and the fourth power switch S4 are always on during the positive half-cycle of the grid current and always off during the negative half-cycle. The second power switch S2 and the third power switch S3 are always on during the negative half-cycle of the grid current and always off during the positive half-cycle. There is a certain dead time between the first power switch S1, the second power switch S2, the third power switch S3 and the fourth power switch S4. The fifth power switch S5 and the sixth power switch S6 operate at high frequency in unipolar SPWM mode throughout the entire cycle. The fifth auxiliary power switch S... 5a and the sixth auxiliary power switch S 6a It operates at high frequency throughout the entire cycle; Fifth auxiliary switch S 5a The turn-on of the transistor is delayed until the turn-on of the fifth power switch S5, and both are turned off simultaneously. Sixth auxiliary switch S 6a The turn-on of the transistor is delayed until the turn-on of the sixth power switch S6, and both are turned off simultaneously.

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