A non-resonant capacitor type parallel resonant DC link soft switching inverter applied to a photovoltaic hydrogen production system
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- NORTHEASTERN UNIV CHINA
- Filing Date
- 2026-04-21
- Publication Date
- 2026-08-07
AI Technical Summary
与此同时，光伏发电系统中的逆变器作为能量转换的核心部件，正朝着高功率密度、小型化、高效化方向快速发展，传统硬开关逆变器因开关损耗大、电磁干扰强，能量转换效率低，还难以适配高功率密度的设计需求，因此软开关技术被广泛引入到逆变器中，以有效降低开关损耗、抑制电磁干扰，提升逆变器的效率与功率密度，保障光伏制氢系统的高效稳定运行
[0014]The auxiliary circuit of the capacitor-free parallel resonant DC-link soft-switching inverter reduces the number of auxiliary diodes by 2 and resonant capacitors by 9, resulting in a simpler structure and a significantly reduced number of components compared to existing soft-switching inverters, thus greatly lowering hardware costs. Furthermore, it achieves current stress decoupling in the auxiliary circuit, eliminating the use of shunt dead zones and minimizing current stress under both light and heavy loads, further reducing losses in the auxiliary commutation circuit. In summary, this improves the efficiency of the resonant DC-link soft-switching inverter.
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Figure CN122533428A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of inverter technology and relates to a soft-switching inverter with a non-resonant capacitor parallel resonant DC link applied to a photovoltaic hydrogen production system. Background Technology
[0002] Against the backdrop of global energy transition and the "dual carbon" goal, traditional high-carbon-emission gray hydrogen is insufficient to meet decarbonization needs, making green hydrogen the core of the hydrogen production industry's transformation. Photovoltaic power generation, as the mainstay of zero-carbon electricity, provides clean support for green hydrogen production, while simultaneously addressing the problem of intermittent solar curtailment by absorbing surplus electricity through hydrogen production. Meanwhile, inverters in photovoltaic power generation systems, as the core component of energy conversion, are rapidly developing towards higher power density, miniaturization, and higher efficiency. Traditional hard-switching inverters, due to high switching losses, strong electromagnetic interference, and low energy conversion efficiency, are difficult to adapt to the design requirements of high power density. Therefore, soft-switching technology has been widely introduced into inverters to effectively reduce switching losses, suppress electromagnetic interference, improve inverter efficiency and power density, and ensure the efficient and stable operation of photovoltaic hydrogen production systems. Figure 1 The symmetrical resonant circuit parallel resonant DC link soft-switching inverter shown solves many structural problems in the topologies proposed by predecessors. For example, the electrolytic capacitor acts as an auxiliary power supply, and potential drift under high-frequency conditions affects the soft-switching operation; the parameters of the coupling magnetic components are complex to design and there is a magnetic reset problem; both positive and negative DC buses are equipped with long-term conducting bus switches, which greatly increases conduction losses.
[0003] However, existing resonant DC-link soft-switching inverters still have shortcomings: under light load, the auxiliary circuit current stress is too high, resulting in reduced efficiency; the auxiliary circuit uses too many components, leading to high hardware costs and hindering the miniaturization and high power density of soft-switching inverters. Summary of the Invention
[0004] To address the aforementioned technical problems, the present invention aims to provide a soft-switching inverter with a non-resonant capacitor parallel resonant DC link for use in photovoltaic hydrogen production systems. This soft-switching inverter has low hardware cost and low current stress in its auxiliary circuits.
[0005] This invention provides a non-resonant capacitor-type parallel resonant DC link soft-switching inverter for use in photovoltaic hydrogen production systems, comprising: an auxiliary circuit, an inverter bridge, a load circuit, and a DC power supply;
[0006] The auxiliary circuit includes: a bus switch transistor, a first auxiliary switch transistor, a second auxiliary switch transistor, a first auxiliary resonant inductor, a second auxiliary resonant inductor, a first auxiliary diode, and a second auxiliary diode;
[0007] The drain of the bus switch transistor is connected to the positive terminal of the DC power supply, the anode of the body diode of the bus switch transistor and the negative terminal of the parasitic capacitance of the bus switch transistor are connected to the source terminal of the bus switch transistor, and the cathode of the body diode of the bus switch transistor and the positive terminal of the parasitic capacitance of the bus switch transistor are connected to the drain terminal of the bus switch transistor.
[0008] The drain of the first auxiliary switch, the cathode of the body diode of the first auxiliary switch, and the positive terminal of the parasitic capacitance of the first auxiliary switch are all connected to the positive terminal of the DC power supply. The source of the first auxiliary switch, the anode of the body diode of the first auxiliary switch, and the negative terminal of the parasitic capacitance of the first auxiliary switch are all connected to one end of the first auxiliary resonant inductor. The first auxiliary resonant inductor and the second auxiliary resonant inductor are connected in series. The other end of the second auxiliary resonant inductor is connected to the drain of the second auxiliary switch, the cathode of the body diode of the second auxiliary switch, and the positive terminal of the parasitic capacitance of the second auxiliary switch. The source of the second auxiliary switch, the anode of the body diode of the second auxiliary switch, and the negative terminal of the parasitic capacitance of the second auxiliary switch are all connected to the negative terminal of the DC power supply. The connection point of the first auxiliary resonant inductor and the second auxiliary resonant inductor connected in series is connected to the source of the bus switch.
[0009] The cathode of the second auxiliary diode is connected to the positive terminal of the DC power supply, and the anode is connected to the drain of the second auxiliary switch; the anode of the first auxiliary diode is connected to the negative terminal of the DC power supply, and the cathode is connected to the source of the first auxiliary switch.
[0010] The inverter bridge is a three-phase inverter bridge. The drains of the main power switching transistors in the upper arms of each phase inverter bridge are connected to each other as the positive terminal of the inverter bridge, and the sources of the main power switching transistors in the lower arms of each phase inverter bridge are connected to each other as the negative terminal of the inverter bridge.
[0011] The load circuit is a three-phase load circuit, and each phase of the load circuit includes a resistor and an inductor. One end of the resistor in the three-phase load circuit is connected to the three single-phase AC output terminals of the three-phase inverter bridge, and the other end of the resistor in the three-phase load circuit is connected to one end of the three inductors. The other ends of the three inductors are connected to each other as the load neutral point.
[0012] The negative terminal of the DC power supply is connected to the negative terminal of the inverter bridge, the positive terminal of the DC power supply is connected to the drain of the bus switch transistor in the auxiliary circuit, and the source of the bus switch transistor is connected to the positive terminal of the inverter bridge.
[0013] The present invention provides a non-resonant capacitor-type parallel resonant DC link soft-switching inverter for use in a photovoltaic hydrogen production system, which has the following advantages:
[0014] The auxiliary circuit of the capacitor-free parallel resonant DC-link soft-switching inverter reduces the number of auxiliary diodes by 2 and resonant capacitors by 9, resulting in a simpler structure and a significantly reduced number of components compared to existing soft-switching inverters, thus greatly lowering hardware costs. Furthermore, it achieves current stress decoupling in the auxiliary circuit, eliminating the use of shunt dead zones and minimizing current stress under both light and heavy loads, further reducing losses in the auxiliary commutation circuit. In summary, this improves the efficiency of the resonant DC-link soft-switching inverter. Attached Figure Description
[0015] Figure 1 This is a schematic diagram of the circuit principle of a parallel resonant DC link soft-switching inverter with a symmetrical resonant circuit, which is a prior art technology.
[0016] Figure 2 A circuit diagram of a non-resonant capacitor type parallel resonant DC link soft-switching inverter for use in a photovoltaic hydrogen production system is provided in this embodiment of the invention.
[0017] Figure 3 The following are equivalent circuit diagrams for the commutation operating modes M0-M6 of this invention; wherein, (a) is an equivalent circuit diagram for commutation operating mode M0; (b) is an equivalent circuit diagram for commutation operating modes M1-a; (c) is an equivalent circuit diagram for commutation operating modes M1-b; (d) is an equivalent circuit diagram for commutation operating mode M2; (e) is an equivalent circuit diagram for commutation operating mode M3; (f) is an equivalent circuit diagram for commutation operating mode M4; (g) is an equivalent circuit diagram for commutation operating mode M5; and (h) is an equivalent circuit diagram for commutation operating mode M6.
[0018] Figure 4 The following are equivalent circuit diagrams for each of the following embodiments of the present invention operating in commutation modes M7-M15: (a) Equivalent circuit diagram for commutation mode M7; (b) Equivalent circuit diagram for commutation mode M8; (c) Equivalent circuit diagram for commutation mode M9-a; (d) Equivalent circuit diagram for commutation mode M9-b; (e) Equivalent circuit diagram for commutation mode M10; (f) Equivalent circuit diagram for commutation mode M11; (g) Equivalent circuit diagram for commutation mode M12; (h) Equivalent circuit diagram for commutation mode M13; (i) Equivalent circuit diagram for commutation mode M14; (j) Equivalent circuit diagram for commutation mode M15.
[0019] Figure 5The following is a schematic diagram of the simulated voltage and current of the first main power switch S1 in an embodiment of the present invention; wherein, (a) is a schematic diagram of the simulated voltage and current when the first main power switch S1 is turned on; and (b) is a schematic diagram of the simulated voltage and current when the first main power switch S1 is turned off.
[0020] Figure 6 The bus switch S in this embodiment of the invention L The simulation waveforms of voltage and current are shown in the diagram; where (a) is the bus switch S. L (a) Schematic diagram of simulated voltage and current waveforms during turn-on; (b) Bus switch S L A schematic diagram of the simulated voltage and current waveforms during shutdown;
[0021] Figure 7 The first auxiliary switch S in this embodiment of the invention a1 Schematic diagram of simulated voltage and current waveforms; where (a) is the first auxiliary switch S. a1 (a) Simulation waveform diagram of voltage and current during turn-on; (b) is the first auxiliary switch S. a1 A schematic diagram of the simulated voltage and current waveforms during shutdown;
[0022] Figure 8 The second auxiliary switch S in this embodiment of the invention a2 Schematic diagram of simulated voltage and current waveforms; where (a) is the second auxiliary switch S. a2 (a) Schematic diagram of simulated voltage and current during turn-on; (b) shows the second auxiliary switch S. a2 A schematic diagram of the simulated voltage and current waveforms during shutdown;
[0023] Figure 9 The load current and auxiliary resonant inductor current of a parallel resonant DC-link soft-switching inverter with a symmetrical resonant circuit are shown under heavy load and light load conditions; wherein, (a) is the load current and auxiliary resonant inductor current of the parallel resonant DC-link soft-switching inverter with a symmetrical resonant circuit under heavy load; and (b) is the load current and auxiliary resonant inductor current of the parallel resonant DC-link soft-switching inverter with a symmetrical resonant circuit under light load.
[0024] Figure 10 This invention relates to a non-resonant capacitor parallel resonant DC soft-switching inverter applied to a photovoltaic hydrogen production system, and presents the load current and auxiliary resonant inductor current under heavy load and light load conditions. Among them, (a) represents the load current and auxiliary resonant inductor current of the soft-switching inverter under heavy load; and (b) represents the load current and auxiliary resonant inductor current of the soft-switching inverter under light load. Detailed Implementation
[0025] The implementation of the embodiments of this disclosure will be described in detail below with reference to the accompanying drawings.
[0026] The terms "first," "second," etc., used in the specification, claims, and accompanying drawings of this disclosure are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate for the embodiments of this disclosure described herein.
[0027] Combination Figure 2 As shown, the present invention provides a non-resonant capacitor type parallel resonant DC link soft-switching inverter for use in photovoltaic hydrogen production systems, comprising: an auxiliary circuit 1, an inverter bridge 2, a load circuit 3, and a DC power supply E.
[0028] Auxiliary circuit 1 includes bus switch S L The body diode D of the bus switch transistor L Parasitic capacitance C of the bus switch transistor L First auxiliary switch S a1 Second auxiliary switch S a2 The body diode D of the first auxiliary switch a1 The body diode D of the second auxiliary switch a2 The parasitic capacitance C of the first auxiliary switch transistor a1 The parasitic capacitance C of the second auxiliary switch a2 First auxiliary resonant inductor L a1 Second auxiliary resonant inductor L a2 and the first auxiliary diode D r1 Second auxiliary diode D r2 .
[0029] Busbar switch tube S L The drain of the transistor is connected to the positive terminal of the DC power supply E, and the body diode D of the bus switch transistor is connected to the positive terminal of the DC power supply E. L The parasitic capacitance C of the anode and bus switch transistor L The negative terminals are all connected to the bus switch transistor S. L The source of the bus switch transistor, the body diode D L The parasitic capacitance C of the cathode and bus switch transistor L The positive terminals are all connected to the drain of the bus switch transistor.
[0030] First auxiliary switch S a1 The drain of the first auxiliary switch transistor and the body diode D a1 The parasitic capacitance C of the cathode and the first auxiliary switch. a1 The positive terminals of all are connected to the positive terminal of the DC power supply E, and the first auxiliary switch S a1 The source of the first auxiliary switch, the body diode D a1The anode and the parasitic capacitance C of the first auxiliary switch. a1 The negative terminals are all connected to the first auxiliary resonant inductor L. a1 One end, the first auxiliary resonant inductor L a1 Second auxiliary resonant inductor L a2 Series connection, second auxiliary resonant inductor L a2 The other end is connected to the second auxiliary switch S a2 The drain of the second auxiliary switch, the body diode D a2 The parasitic capacitance C of the cathode and the second auxiliary switch a2 The positive terminal, the second auxiliary switch S a2 The source of the second auxiliary switch, the body diode D a2 The parasitic capacitance C of the anode and the second auxiliary switch. a2 The negative terminals of all components are connected to the negative terminal of the DC power supply E, and the first auxiliary resonant inductor L... a1 Second auxiliary resonant inductor L a2 The series connection point and the bus switch S L The source poles are connected.
[0031] Second auxiliary diode D r2 The cathode is connected to the positive terminal of the DC power supply E, and the anode is connected to the second auxiliary switch S. a2 The drain of the first auxiliary diode D; r1 The anode is connected to the negative terminal of the DC power supply E, and the cathode is connected to the first auxiliary switch S. a1 The source pole.
[0032] Inverter bridge 2 is a three-phase inverter bridge, including phase A inverter bridge, phase B inverter bridge and phase C inverter bridge.
[0033] The A-phase inverter bridge includes a first main power switch S1, a body diode D1 of the first main power switch, a parasitic capacitance C1 of the first main power switch, a second main power switch S2, a body diode D2 of the second main power switch, and a parasitic capacitance C2 of the second main power switch. The first main power switch S1 is the main power switch of the upper bridge arm in the A-phase inverter bridge, and the second main power switch S2 is the main power switch of the lower bridge arm. The source of the first main power switch S1 is connected to the drain of the second main power switch S2, and the lead at the connection point of the first main power switch S1 and the second main power switch S2 is the AC output terminal of the A-phase.
[0034] The B-phase inverter bridge includes a third main power switch S3, a body diode D3 of the third main power switch, a parasitic capacitance C3 of the third main power switch, a fourth main power switch S4, a body diode D4 of the fourth main power switch, and a parasitic capacitance C4 of the fourth main power switch. The third main power switch S3 is the main power switch of the upper arm of the B-phase inverter bridge, and the fourth main power switch S4 is the main power switch of the lower arm. The source of the third main power switch S3 is connected to the drain of the fourth main power switch S4, and the lead at the connection point of the third main power switch S3 and the fourth main power switch S4 is the B-phase AC output terminal.
[0035] The C-phase inverter bridge includes a fifth main power switch S5, a body diode D5 of the fifth main power switch, a parasitic capacitance C5 of the fifth main power switch, a sixth main power switch S6, a body diode D6 of the sixth main power switch, and a parasitic capacitance C6 of the sixth main power switch. The fifth main power switch S5 is the upper arm main power switch of the C-phase inverter bridge, and the sixth main power switch S6 is the lower arm main power switch. The source of the fifth main power switch S5 is connected to the drain of the sixth main power switch S6, and the lead at the connection point of the fifth main power switch S5 and the sixth main power switch S6 is the C-phase AC output terminal.
[0036] The drains of the first main power switch S1, the third main power switch S3, and the fifth main power switch S5 in the inverter bridge are connected to each other, serving as the positive terminal of inverter bridge 2; the sources of the second main power switch S2, the fourth main power switch S4, and the sixth main power switch S6 in the inverter bridge are connected to each other, serving as the negative terminal of inverter bridge 2.
[0037] Load circuit 3 is a three-phase resistive-inductive load circuit, including a first resistor R. A Second resistor R B Third resistor R C and the first inductor L A Second inductor L B Third inductor L C First resistor R A Second resistor R B Third resistor R C One end is connected to the AC output terminals of phases A, B, and C respectively, and the first resistor R A Second resistor R B Third resistor R C The other end is connected to the first inductor L. A Second inductor L B Third inductor L C One end, the first inductor L A Second inductor L B Third inductor L CThe other end is connected to each other as the load neutral point.
[0038] The negative terminal of DC power supply E is connected to the negative terminal of inverter bridge 2, and the positive terminal of DC power supply E is connected to the auxiliary circuit bus switch S. L The drain of the bus switch S L The source terminal is connected to the positive terminal of the inverter bridge 2.
[0039] The non-resonant capacitor parallel resonant DC link soft-switching inverter provided in this embodiment for use in photovoltaic hydrogen production systems has a significantly reduced number of components in its auxiliary circuit compared to existing soft-switching inverters, thus reducing hardware costs.
[0040] Optionally, the bus switch, auxiliary switch, and each main power switch in the inverter bridge are all silicon carbide metal oxide semiconductor field-effect transistors.
[0041] Optionally, the first auxiliary diode D r1 Second auxiliary diode D r2 All of them are fast recovery diodes or high-frequency diodes.
[0042] Optionally, the DC power supply is a DC voltage source or a voltage source obtained by DC-DC (direct current to direct current) conversion and rectification.
[0043] Since all the switching transistors use the same model, the parasitic capacitance C of the first auxiliary switching transistor is... a1 The parasitic capacitance C of the second auxiliary switch a2 Parasitic capacitance C of the bus switch transistor L The parasitic capacitances C1, C2, C3, C4, C5, and C6 of the first, second, third, fourth, fifth, and sixth main power switches are all equal, with a capacitance value of C. s Set the first auxiliary resonant inductor L. a1 Second auxiliary resonant inductor L a2 Equal, the inductance value is L. s Due to the setting of the switching frequency f s Much greater than the inverter output frequency f o Therefore, the load current i of phase A during the switching vector time is... A Phase B load current i B C-phase load current i C All of them can be considered constant values.
[0044] The modulation strategy adopted in this embodiment is as follows: At the same time as the main power switch S2 of the lower arm of phase A and the main power switch S6 of the lower arm of phase C are turned off, the bus switch S... L Shutdown, bus switch SL At the same time as the second auxiliary switch S is turned off a2 Turn on, second auxiliary switch S a2 Open t dead After a delay, the second auxiliary switch S is turned off. a2 At the same time as the switch is turned off, the main power switch S1 of phase A upper arm and the main power switch S5 of phase C upper arm are turned on, and the second auxiliary switch S1 is turned on. a2 After the turn-off delay time δ1, the first auxiliary switch S a1 Turn on, first auxiliary switch S a1 After the δ2 delay time is turned on, the bus switch S L Busbar switch S L After the δ3 delay time is turned on, the first auxiliary switch S a1 Turn off.
[0045] like Figure 3 and Figure 4 As shown, the specific converter operating modes are described below.
[0046] Pattern M0 (~ t0]: such as Figure 3 (a) Before time t0, the main inverter circuit circulates through the body diode D2 of the second main power switch, the body diode D6 of the fourth main power switch, and the body diode D6 of the sixth main power switch. Bus switch S... L Although it is turned on, no current flows through it; the first auxiliary diode S... a1 Second auxiliary diode S a2 The first main power switch S1, the third main power switch S3, and the fifth main power switch S5 are all in the off state.
[0047] Mode M1 [t0, t1]: Bus switch S L At the same time as being turned off, the second auxiliary switch S a2 It was turned on. Although the second auxiliary resonant inductor L a2 The presence of [something] has a suppressive effect on current changes, but the parasitic capacitance C of the second auxiliary switch [is also affected]. a2 The stored energy will be transmitted through the second auxiliary switch S. a2 Rapid release causes the second auxiliary switch S to... a2 current i Sa2 A small current spike is generated, therefore the second auxiliary switch S a2 For lossy quasi-ZCS turn-on. First auxiliary resonant inductor L a1 Second auxiliary resonant inductor L a2 Parasitic capacitance C of the bus switch transistor L The parasitic capacitance C of the first auxiliary switch transistor a1The parasitic capacitances C1 of the first main power switch, C3 of the third main power switch, and C5 of the fifth main power switch begin to resonate. For ease of analysis and calculation, this is divided into two sub-modes:
[0048] Mode M1-a: such as Figure 3 As shown in (b), the second auxiliary resonant inductor L a2 Parasitic capacitance C of the bus switch transistor L The parasitic capacitance C of the first auxiliary switch transistor a1 The parasitic capacitances C1, C3, and C5 of the first, third, and fifth main power switches resonate. These capacitances begin to discharge resonantly from the DC power supply voltage E. The parasitic capacitance C of the bus switch... L Resonant charging begins from zero. This mode ends when the parasitic capacitance C1 of the first main power switch, the parasitic capacitance C3 of the third main power switch, and the parasitic capacitance C5 of the fifth main power switch discharge to zero. At this time, the second auxiliary resonant inductor L... a2 current i La2 Reaching the maximum value i La2max .
[0049] Mode M1-b: such as Figure 3 As shown in (c), the first auxiliary resonant inductor L a1 and the parasitic capacitance C of the first auxiliary switch a1 Resonance, first auxiliary resonant inductor L a1 and the parasitic capacitance C of the first auxiliary switch a1 All start resonant charging from zero. When the parasitic capacitance C of the first auxiliary switch transistor... a1 This mode ends when the charge reaches the DC power supply voltage E.
[0050] Pattern M2 [t1, t2]: such as Figure 3 As shown in (d), after the parasitic capacitance C1 of the first main power switch, the parasitic capacitance C3 of the third main power switch, and the parasitic capacitance C5 of the fifth main power switch are discharged to zero, the current i of the second auxiliary resonant inductor... La2 Through (the second auxiliary resonant inductor L) a2 -Second auxiliary switch S a2 - Parasitic capacitance D3 of the third main power switch - Circulating current in the circuit of the fourth main power switch S4, and current i of the first auxiliary resonant inductor. La1 Through (first auxiliary resonant inductor L) a1 -Second auxiliary resonant inductor L a2 -Second auxiliary switch S a2- Parasitic capacitance D of the first auxiliary switch r1 The load current circulates through the loop (parasitic capacitance D2 of the second main power switch - parasitic capacitance D6 of the fourth main power switch - parasitic capacitance D6 of the sixth main power switch) until it reaches the second auxiliary switch S. a2 Turn off; this mode ends.
[0051] Pattern M3 [t2, t3]: such as Figure 3 As shown in (e), the second auxiliary switch S a2 Simultaneously with the turn-off, the first main power switch S1 and the fifth main power switch S5 are turned on. Since the voltages at the terminals of the first main power switch S1 and the fifth main power switch S5 are zero, ZVZCS turn-on can be achieved. Due to the parasitic capacitance C of the second auxiliary switch... a2 The presence of the second auxiliary switch S a2 It is a hard turn-off, but considering the second auxiliary resonant inductor L a2 Maximum current i La2max The value is relatively small and the SiC MOSFET device is carefully selected, so its turn-off loss is limited; the second auxiliary switch S a2 After being turned off, the second auxiliary resonant inductor L a2 Parasitic capacitance C of the second auxiliary switch a2 Resonance. Until the parasitic capacitance C of the second auxiliary switch. a2 The mode ends when the DC power supply voltage E is reached.
[0052] Pattern M4 [t3, t4]: (e.g.) Figure 3 As shown in (f), the parasitic capacitance C of the second auxiliary switch is... a2 After charging to the DC power supply voltage E, the second auxiliary diode D r2 The second auxiliary resonant inductor L is turned on. a2 current i La2 Linearly decrease and through the second auxiliary diode D r2 Energy is fed back to the power source. When the second auxiliary resonant inductor L... a2 current i La2 The mode ends when the number of elements decreases to zero.
[0053] Pattern M5 [t4, t5]: (e.g.) Figure 3 As shown in (g), the second auxiliary resonant inductor L a2 current i La2 After dropping to zero, due to the second auxiliary diode D r2 The reverse recovery effect of the second auxiliary resonant inductor L a2 current i La2 Reverse flow will reduce the parasitic capacitance C of the second auxiliary switch. a2Energy storage release, parasitic capacitance C of the second auxiliary switch a2 After discharging to zero, the second auxiliary switch D... a2 Once the circuit is activated, this mode will end.
[0054] Pattern M6 [t5, t6]: (e.g.) Figure 3 As shown in (h), the body diode D of the second auxiliary switch is... a2 After conduction, the first auxiliary resonant inductor L a1 current i La1 Through (first auxiliary diode D) r1 -First auxiliary resonant inductor L a1 - First main power switch S1 - Body diode D2 of the second main power switch - Body diode D3 of the third main power switch - Fourth main power switch S4 - Fifth main power switch S5 - Body diode D6 of the sixth main power switch) Circulating current in the circuit, second auxiliary resonant inductor L a2 current i La2 Through (the body diode D of the second auxiliary switch) a2 -Second auxiliary resonant inductor L a2 The current circulates through the loop from the first main power switch S1 to the body diode D2 of the second main power switch, the body diode D3 of the third main power switch, the fourth main power switch S4, the fifth main power switch S5, and the body diode D6 of the sixth main power switch, until the first auxiliary switch S... a1 Once activated, this mode will end.
[0055] Pattern M7 [t6, t7]: (e.g.) Figure 4 As shown in (a), the first auxiliary switch S a1 After activation, the parasitic capacitance C of the first auxiliary switch transistor... a1 Energy is stored in the middle through the first auxiliary switch S a1 Rapidly released, and at this time the first auxiliary diode D r1 To the first auxiliary switch S a1 Commutation occurs during the commutation process, but reverse recovery is possible due to the parasitic capacitance C of the first auxiliary switch. a1 The existence of , and the first auxiliary resonant inductor L a1 current i La1 (t1) is relatively small, and the reverse recovery energy is limited, therefore the first auxiliary switch S a1 Still lossy quasi-ZCS turn-on. First auxiliary diode D r1 To the first auxiliary switch S a1 After commutation, the body diodes D2, D6, and D3 of the second main power switch, and the sixth main power switch, respectively, supply power to the first auxiliary resonant inductor L. a1 Commutation, first auxiliary resonant inductor La1 current i La1 The current increases linearly, rising to the current (i) La2 (t5)-i B After that, the mode ends.
[0056] Pattern M8 [t7, t8]: (e.g.) Figure 4 As shown in (b), the first auxiliary resonant inductor L a1 current i La1 Rise to current (i La2 (t5)-i B After that, the body diode D of the second auxiliary switch transistor a2 Second auxiliary resonant inductor L a2 To the first auxiliary resonant inductor L a1 Commutation, first auxiliary resonant inductor L a1 current i La1 The intermediate current continues to increase linearly, rising to the current (-i) B After that, the mode ends.
[0057] Mode M9 [t8, t9]: Body diode D of the second auxiliary switch a2 Second auxiliary resonant inductor L a2 To the first auxiliary resonant inductor L a1 After the commutation is completed, the first auxiliary resonant inductor L a1 Second auxiliary resonant inductor L a2 Parasitic capacitance C of the bus switch transistor L The parasitic capacitance C of the second auxiliary switch a2 The parasitic capacitances C2, C3, and C6 of the second, third, and sixth main power switches begin to resonate. For ease of analysis and calculation, this is divided into two sub-modes:
[0058] M9-a: such as Figure 4 As shown in (c), the first auxiliary resonant inductor L a1 from(-i B Resonant charging begins, and the parasitic capacitances C2, C3, and C6 of the second, third, and sixth main power switches resonate from zero. The parasitic capacitance C of the bus switch also begins resonant charging. L Resonant discharge begins from the DC power supply voltage E. When the voltage v of the parasitic capacitance C2 of the second main power switch transistor... C2 The voltage v of the parasitic capacitance C3 of the third main power switch transistor C3 The voltage v of the parasitic capacitance C6 of the sixth main power switch transistor C6 This mode ends when all components are charged to the DC power supply voltage E. At this time, the first auxiliary resonant inductor L... a1current i La1 Reaching the maximum value i La1max .
[0059] Mode M9-b: such as Figure 4 As shown in (d), the second auxiliary resonant inductor L a2 The parasitic capacitance C of the second auxiliary switch a2 Resonance, second auxiliary resonant inductor L a2 The parasitic capacitance C of the second auxiliary switch a2 All start resonant charging from zero. When the parasitic capacitance C of the second auxiliary switch... a2 This mode ends when the charge reaches the DC power supply voltage E.
[0060] Pattern M10 [t9, t 10 ]:like Figure 4 As shown in (e), when the parasitic capacitance C of the second auxiliary switch transistor... a2 After charging to the DC power supply voltage E, the second auxiliary diode D r2 The second auxiliary resonant inductor L is turned on. a2 current i La2 Through (the second auxiliary resonant inductor L) a2 -Second auxiliary diode D r2 -First auxiliary switch S a1 -First auxiliary resonant inductor L a1 ) Loop current, first auxiliary resonant inductor L a1 current i La1 Through (first auxiliary resonant inductor L) a1 -Body diode D of the bus switch transistor L -First auxiliary switch S a1 ) Circulating current in the circuit; if the bus switch S is turned on during this period... L This allows for the ZVZCS turn-on to be achieved until the first auxiliary switch S is activated. a1 Turn off; this mode ends.
[0061] Mode M11 [t 10 , t 11 ]:like Figure 4 As shown in (f), the first auxiliary switch S a1 After being turned off, the parasitic capacitance C of the first auxiliary switch transistor... a1 Energy is stored in the middle through the first auxiliary switch S a1 Rapid release, similar to the above, the first auxiliary switch S a1 It remains a hard-shutdown mechanism with limited losses. First auxiliary inductor L a1 Parasitic capacitance C of the first auxiliary switch a1 Resonance, first auxiliary inductor L a1 From the first auxiliary inductor La1 Maximum current i La1max Resonant discharge begins until the parasitic capacitance C of the first auxiliary switch is reached. a1 The mode ends when the DC power supply voltage E is reached.
[0062] Mode M12 [t 11 , t 12 ] and mode M13 [t 12 , t 13 ]:like Figure 4 (g) and Figure 4 As shown in (h), the parasitic capacitance C of the first auxiliary switch is... a1 After charging to the DC power supply voltage E, the first auxiliary diode D r1 On. First auxiliary inductor L a1 current i La1 In E / L s The slope decreases linearly when the first auxiliary inductor L a1 current i La1 Decrease to (-i) B +i La2 (t9)) when the body diode D of the bus switch transistor is used. L Conduction switching to bus switch S L On, the first auxiliary inductor L a1 current i La1 Continue to decrease until the first auxiliary inductor L a1 current i La1 If the value is zero, the mode ends.
[0063] M14 [t 13 , t 14 ]:like Figure 4 As shown in (i), the first auxiliary inductor L a1 current i La1 After decreasing to zero, due to the first auxiliary diode D r1 Reverse recovery function, first auxiliary inductor L a1 current i La1 Reverse flow causes the parasitic capacitance C of the first auxiliary switch to... a1 Resonant discharge, when the parasitic capacitance C of the first auxiliary switch... a1 voltage v Ca1 The mode ends when the temperature drops to zero.
[0064] Mode M15 [t 14 , t 15 ]:like Figure 4 As shown in (j), the parasitic capacitance C of the first auxiliary switch is... a1 voltage v Ca1 After dropping to zero, the body diode D of the first auxiliary switch transistor...a1 On. First auxiliary inductor L a1 current i La1 In (first auxiliary inductor L) a1 -The body diode D of the first auxiliary switch transistor a1 -Bus switch S L The second auxiliary inductor L gradually loses power to zero in the circuit. a2 current i La2 In (second auxiliary inductor L) a2 -Second auxiliary diode D r2 -Bus switch S L The power supply gradually depletes to zero in the circuit, ending this mode. The DC power supply E is supplied via the bus switch S. L The first main power switch S1, the fourth main power switch S4, and the fifth main power switch S5 supply power to the load.
[0065] To verify the correctness of the above theory, according to Figure 2 The circuit schematic shown was used to build a simulation platform for verification, and the corresponding simulation results are shown below.
[0066] This invention provides an embodiment of the voltage v of the first main power switch S1 during turn-on and turn-off of a non-resonant capacitor-type parallel resonant DC-link soft-switching inverter applied to a photovoltaic hydrogen production system. S1 and current i S1 The simulated waveform is as follows Figure 5 As shown, from Figure 5 (a) The region shows the voltage v of the first main power switch S1. S1 After rapidly discharging to zero, the first main power switch S1 only turns on after a certain period of time, thus achieving ZVZCS turn-on. From Figure 5 (b) As can be seen from the region, the current i of the first main power switch S1 S1 When the voltage v of the first main power switch S1 drops to approximately zero, S1 The waveform begins to rise slowly, so the first main power switch S1 achieves quasi-ZVS turn-off. The simulation waveforms of the other main power switches are similar to those of the first main power switch S1, and will not be described in detail here.
[0067] The present invention discloses a bus switch S for a non-resonant capacitor-type parallel resonant DC link soft-switching inverter applied to a photovoltaic hydrogen production system. L Voltage v during turn-on and turn-off SL and current i SL Simulated waveforms Figure 6 As shown, from Figure 6 (a) The area shows the bus switch S L Voltage v across the terminals SL After the resonance drops to zero for a period of time, the bus switch S L It has just been put into operation, so the bus switch S L ZVZCS activation has been achieved; from Figure 6 (b) The area shows the bus switch S L After being turned off, the voltage v across its terminals SL Starting from zero, the current increases linearly while remaining at zero, therefore the bus switch S... L ZCZVS shutdown was implemented.
[0068] The present invention discloses an embodiment of a first auxiliary switch S of a non-resonant capacitor-type parallel resonant DC-link soft-switching inverter applied to a photovoltaic hydrogen production system. a1 Voltage v during turn-on and turn-off Sa1 and current i Sa1 Simulated waveforms Figure 7 As shown, from Figure 7 (a) The area shows the first auxiliary switch S a1 voltage v Sa1 After rapidly dropping to zero, the current flows through the first auxiliary switch S. a1 current i Sa1 Starting from zero and gradually increasing, the first auxiliary switch S a1 Quasi-ZCS activation has been achieved. From Figure 7 (b) As can be seen from the area, the first auxiliary switch S a1 For hard shutdown, due to the first auxiliary switch S a1 As a SiCMOSFET device, it has no minority carrier storage effect, no tail current during turn-off, and extremely short voltage-current overlap time, thus its turn-off loss is limited.
[0069] The present invention discloses a second auxiliary switch S of a non-resonant capacitor-type parallel resonant DC-link soft-switching inverter applied to a photovoltaic hydrogen production system. a2 Voltage v during turn-on and turn-off Sa2 and current i Sa2 The simulated waveform is as follows Figure 8 As shown, from Figure 8 (a) The area shows the second auxiliary switch S a2 voltage v Sa2 After rapidly dropping to zero, the current flows through the second auxiliary switch S. a2 current i Sa2 Starting from zero and gradually increasing, the second auxiliary switch S...a2 Quasi-ZCS activation has been achieved. From Figure 8 (b) As can be seen from the area, the second auxiliary switch S a2 For hard shutdown, due to the second auxiliary switch S a2 As a SiC MOSFET device, it has no minority carrier storage effect, no tail current during turn-off, and extremely short voltage-current overlap time, thus its turn-off loss is limited.
[0070] Existing symmetrical resonant circuit parallel resonant DC link soft-switching inverters have load current i under heavy and light load conditions. R and auxiliary resonant inductor current i L Each as Figure 9 As shown in (a) and 9(b), the disclosed embodiments of the present invention provide a load current i of a non-resonant capacitor-type parallel resonant DC link soft-switching inverter applied to a photovoltaic hydrogen production system under heavy load and light load conditions. R and auxiliary resonant inductor current i L like Figure 10 As shown in (a) and 10(b), a comparison reveals that: the symmetrical resonant circuit parallel resonant DC-link soft-switching inverter has auxiliary resonant inductor currents of 53.94A and 24.87A under heavy and light load conditions, respectively; the capacitor-free parallel resonant DC-link soft-switching inverter provided in this disclosure has auxiliary resonant inductor currents of 42.27A and 7.19A under heavy and light load conditions, respectively; under the scheme of the embodiments of this disclosure, the peak value of the auxiliary resonant inductor current is reduced by more than 10A, especially under light load conditions, the peak value of the auxiliary resonant inductor current is reduced by 17.68A, and the current stress of the auxiliary circuit is close to the load current, which helps to reduce the loss of the auxiliary circuit.
[0071] The auxiliary circuit of the capacitor-free parallel resonant DC-link soft-switching inverter for photovoltaic hydrogen production systems provided by this invention reduces the number of auxiliary diodes by two and resonant capacitors by nine. This results in a simpler structure and a significantly reduced number of components compared to existing soft-switching inverter auxiliary circuits, thus substantially lowering hardware costs. At the hardware level, the resonant current and load current in the auxiliary converter circuit are separated, significantly reducing the current stress on the auxiliary converter circuit and its internal components, further reducing auxiliary converter circuit losses. In summary, this invention significantly improves the efficiency of the resonant DC-link soft-switching inverter.
[0072] The foregoing description and accompanying drawings fully illustrate embodiments of the present disclosure to enable those skilled in the art to practice them. Other embodiments may include structural and other changes. The embodiments represent only possible variations. Individual components and functions are optional unless explicitly required, and the order of operation may vary. Parts and features of some embodiments may be included or substituted for parts and features of other embodiments. Embodiments of the present disclosure are not limited to the structures described above and shown in the accompanying drawings, and various modifications and changes may be made without departing from its scope. The scope of the present disclosure is limited only by the appended claims.
Claims
1. A capacitor-free parallel resonant DC-DC soft-switching inverter for use in photovoltaic hydrogen production systems, characterized in that, include: Auxiliary circuit, inverter bridge, load circuit and DC power supply; The auxiliary circuit includes: a bus switch transistor, a first auxiliary switch transistor, a second auxiliary switch transistor, a first auxiliary resonant inductor, a second auxiliary resonant inductor, a first auxiliary diode, and a second auxiliary diode; The drain of the bus switch transistor is connected to the positive terminal of the DC power supply, the anode of the body diode of the bus switch transistor and the negative terminal of the parasitic capacitance of the bus switch transistor are connected to the source terminal of the bus switch transistor, and the cathode of the body diode of the bus switch transistor and the positive terminal of the parasitic capacitance of the bus switch transistor are connected to the drain terminal of the bus switch transistor. The drain of the first auxiliary switch, the cathode of the body diode of the first auxiliary switch, and the positive terminal of the parasitic capacitance of the first auxiliary switch are all connected to the positive terminal of the DC power supply. The source of the first auxiliary switch, the anode of the body diode of the first auxiliary switch, and the negative terminal of the parasitic capacitance of the first auxiliary switch are all connected to one end of the first auxiliary resonant inductor. The first auxiliary resonant inductor and the second auxiliary resonant inductor are connected in series. The other end of the second auxiliary resonant inductor is connected to the drain of the second auxiliary switch, the cathode of the body diode of the second auxiliary switch, and the positive terminal of the parasitic capacitance of the second auxiliary switch. The source of the second auxiliary switch, the anode of the body diode of the second auxiliary switch, and the negative terminal of the parasitic capacitance of the second auxiliary switch are all connected to the negative terminal of the DC power supply. The connection point of the first auxiliary resonant inductor and the second auxiliary resonant inductor connected in series is connected to the source of the bus switch. The cathode of the second auxiliary diode is connected to the positive terminal of the DC power supply, and the anode is connected to the drain of the second auxiliary switch; the anode of the first auxiliary diode is connected to the negative terminal of the DC power supply, and the cathode is connected to the source of the first auxiliary switch. The inverter bridge is a three-phase inverter bridge. The drains of the main power switching transistors in the upper arms of each phase inverter bridge are connected to each other as the positive terminal of the inverter bridge, and the sources of the main power switching transistors in the lower arms of each phase inverter bridge are connected to each other as the negative terminal of the inverter bridge. The load circuit is a three-phase load circuit, and each phase of the load circuit includes a resistor and an inductor. One end of the resistor in the three-phase load circuit is connected to the three single-phase AC output terminals of the three-phase inverter bridge, and the other end of the resistor in the three-phase load circuit is connected to one end of the three inductors. The other ends of the three inductors are connected to each other as the load neutral point. The negative terminal of the DC power supply is connected to the negative terminal of the inverter bridge, the positive terminal of the DC power supply is connected to the drain of the bus switch transistor in the auxiliary circuit, and the source of the bus switch transistor is connected to the positive terminal of the inverter bridge.
2. The non-resonant capacitor-type parallel resonant DC link soft-switching inverter for photovoltaic hydrogen production systems according to claim 1, characterized in that, Each phase of the inverter bridge includes an upper arm main power switch, a body diode of the upper arm main power switch, a parasitic capacitance of the upper arm main power switch, a lower arm main power switch, a body diode of the lower arm main power switch, and a parasitic capacitance of the lower arm main power switch. The source of the upper arm main power switch in each phase inverter bridge is connected to the drain of the lower arm main power switch. The lead at the connection point between the upper arm main power switch and the lower arm main power switch is a single-phase AC output terminal.
3. The non-resonant capacitor-type parallel resonant DC link soft-switching inverter for photovoltaic hydrogen production systems according to claim 1, characterized in that, The bus switch, auxiliary switch, and main power switch in the inverter bridge are all silicon carbide metal oxide semiconductor field-effect transistors.
4. The non-resonant capacitor-type parallel resonant DC link soft-switching inverter for photovoltaic hydrogen production systems according to claim 1, characterized in that, Both the first auxiliary diode and the second auxiliary diode are fast recovery diodes or high-frequency diodes.
5. The non-resonant capacitor-type parallel resonant DC link soft-switching inverter for photovoltaic hydrogen production systems according to claim 1, characterized in that, The DC power supply is a DC voltage source or a voltage source obtained by DC-DC conversion and rectification.