Resonant DC link soft switching inverter and circuit modulation method thereof

Abstract

The present application relates to the technical field of inverters, and discloses a resonant DC link soft-switching inverter and a circuit modulation method thereof, wherein the circuit modulation method comprises: firstly, reducing the loss of the three-phase inverter bridge by adopting a discontinuous pulse width modulation strategy; secondly, further reducing the loss of the three-phase inverter bridge by adopting a synchronous modulation strategy; thirdly, minimizing the operating frequency of the auxiliary commutation circuit and reducing the loss of the auxiliary commutation circuit by using a sawtooth wave with alternating positive and negative slopes as a carrier; finally, separating the resonant current from the load current in the auxiliary commutation circuit by adopting a shunt dead zone modulation strategy, reducing the current stress of the auxiliary commutation circuit, and further reducing the loss of the auxiliary commutation circuit; in summary, improving the efficiency of the resonant DC link soft-switching inverter.

Description

Technical Field

[0001] The present application relates to the field of inverter technology, for example, to a resonant DC link soft-switching inverter and a circuit modulation method thereof. Background Art

[0002] At present, power electronic devices are an important part of power electronic technology. Historically, the innovation and development of the power electronics field are inseparable from power electronic devices. In recent years, with the continuous maturity of wide bandgap devices, wide bandgap inverters used in switching power supplies, new energy grid connection, motor drives and other occasions have gradually become a research hotspot. However, when the wide bandgap inverter operates at a switching frequency of tens of kilohertz or even hundreds of kilohertz, its switching loss also increases rapidly with the increase of switching frequency. In order to further improve the performance of wide bandgap inverters, soft switching technology is a way worth exploring.

[0003] The soft-switching inverter was first proposed by Dr. DM Divan of the University of Wisconsin in 1989. Since the resonant circuit in the topology proposed by Dr. Divan is located on the DC power supply side, it is called a resonant DC link soft-switching inverter. The resonant DC link soft-switching inverter not only achieves miniaturization and lightness of the inverter, but also successfully reduces switching losses to achieve high efficiency and suppresses electromagnetic interference by reducing the voltage change rate dv / dt and current change rate di / dt.

[0004] However, traditional resonant DC link soft-switching inverters generally have problems such as large voltage stress on the main power switch tube and high content of low-order harmonics in the output voltage. In order to solve the above problems, researchers have proposed an active clamped resonant DC link soft-switching inverter and its supporting modulation strategy, which can greatly reduce the voltage stress of the main power switch tube and adopt SVPWM (space vector pulse width modulation) modulation strategy to facilitate filter design to reduce low-order harmonics of the output voltage. However, since the auxiliary resonant inductor of the active clamped resonant DC link soft-switching inverter is located on the DC bus and works for a long time, its conduction loss increases, resulting in reduced inverter efficiency. In order to solve this problem, researchers have proposed a parallel resonant DC link soft-switching inverter, which transfers the auxiliary resonant inductor to the auxiliary commutation circuit in parallel with the inverter bridge, avoiding the long-term conduction loss of the auxiliary resonant inductor while further reducing the voltage stress of the main power switch tube. However, parallel resonant DC link soft-switching inverters also have some disadvantages. For example, some need to set the auxiliary resonant inductor current threshold, which reduces the practicality and reliability of the topology for the detection and control of the inductor current; some need to use split capacitors as auxiliary power supplies, which brings about the problem of neutral point potential changes and limited service life; some need to use coupled inductors or transformers, and the presence of coupled magnetic components makes parameter design complicated and limits the power density.

[0005] In order to overcome the above problems, an article entitled "Resonant Inductance Design and Loss Analysis of a Novel Resonant DC Link Inverter" in "IEEE Transactions on Power Electronics" and an article entitled "Parallel Resonant DC Link Inverter Topology and Analysis of Its Operation Principle" in "IEEE Journal of Emerging and Selected Topics in Power Electronics" disclose a novel resonant DC link soft switching inverter topology (such as Figure 1 The auxiliary commutation circuit of the novel resonant DC link soft-switching inverter includes a bus switch tube S L And an anti-parallel diode D L , 2 auxiliary switch tubes S a1 and S a2 , 3 resonant capacitors C L , C a1 and C a2 , 2 resonant inductors L a1 and L a2 and 4 auxiliary diodes D a1 , D a2 , D a3 and D a4 This topology can not only realize the soft switching action of all switches, but also avoid many problems such as split capacitor causing change of neutral point potential and setting inductor current threshold making control process complicated. It has excellent performance in all aspects, but it still has the following disadvantages: ① The auxiliary commutation circuit uses too many devices, the hardware cost is high, and it is not conducive to the miniaturization and high power density of soft switching inverter; ② The traditional SPWM (sinusoidal pulse width modulation) triangle carrier modulation strategy is adopted. The auxiliary commutation circuit needs to act 6 times in one switching cycle. The action frequency of the auxiliary commutation circuit is too high, which brings a lot of losses; ③ The current stress of the auxiliary commutation circuit is too large. The current stress of the auxiliary commutation circuit is close to twice the peak value of the load current. On the one hand, it threatens the safe operation of the auxiliary switch tube, and on the other hand, it also greatly increases the loss, resulting in reduced inverter efficiency.

[0006] It should be noted that the information disclosed in the above background technology section is only used to enhance the understanding of the background of the present application, and therefore may include information that does not constitute the prior art known to ordinary technicians in the field. Summary of the invention

[0007] In order to provide a basic understanding of some aspects of the disclosed embodiments, a brief summary is given below. The summary is not an extensive review, nor is it intended to identify key / critical components or delineate the scope of protection of these embodiments, but rather serves as a prelude to the detailed description that follows.

[0008] The disclosed embodiments provide a resonant DC link soft-switching inverter and a circuit modulation method thereof, which reduces the number of auxiliary commutation circuit components, reduces the three-phase inverter bridge loss, reduces the auxiliary commutation circuit operation frequency and current stress, and improves the inverter efficiency.

[0009] In some embodiments, the resonant DC link soft-switching inverter comprises: an auxiliary commutation circuit, an inverter bridge, a load circuit, a control circuit and a DC power supply;

[0010] The auxiliary commutation circuit includes a bus switch tube, an auxiliary switch tube, an auxiliary resonant inductor, a main resonant capacitor, an auxiliary resonant capacitor, an anti-parallel diode of the bus switch tube, a first auxiliary diode, and a second auxiliary diode;

[0011] The collector of the bus switch tube is connected to the positive electrode of the DC power supply, the emitter of the bus switch tube is connected to the inverter bridge, the anode of the anti-parallel diode of the bus switch tube is connected to the emitter of the bus switch tube, and the cathode of the anti-parallel diode of the bus switch tube is connected to the collector of the bus switch tube;

[0012] The positive electrode of the main resonant capacitor is connected to the collector of the bus switch tube and the collector of the auxiliary switch tube, the negative electrode of the main resonant capacitor is connected to the emitter of the bus switch tube, the emitter of the auxiliary switch tube is connected to one end of the auxiliary resonant inductor, and the other end of the auxiliary resonant inductor is connected to the emitter of the bus switch tube;

[0013] The cathode of the first auxiliary diode is connected to the emitter of the auxiliary switch tube, the anode of the first auxiliary diode is connected to the negative electrode of the auxiliary resonant capacitor, the positive electrode of the auxiliary resonant capacitor is connected to the emitter of the bus switch tube, the anode of the second auxiliary diode is connected to the negative electrode of the DC power supply, and the cathode of the second auxiliary diode is connected to the negative electrode of the auxiliary resonant capacitor;

[0014] The inverter bridge is a three-phase inverter bridge, the collectors of the upper bridge arm main power switch tubes of each phase inverter bridge are connected to each other as the positive end of the inverter bridge, and the emitters of the lower bridge arm main power switch tubes of each phase inverter bridge are connected to each other as the negative end of the inverter bridge;

[0015] The load circuit is a three-phase load circuit, and each phase load circuit includes a resistor and an inductor; one end of the resistor in the three-phase load circuit is respectively connected to three single-phase AC output ends of the three-phase inverter bridge, the other end of the resistor in the three-phase load circuit is respectively connected to one end of three inductors, and the other ends of the three inductors are connected to each other as a load neutral point, and the load currents output by the three single-phase AC output ends are sampled by sensors and respectively input into the control circuit as input signals;

[0016] The negative electrode of the DC power supply is connected to the negative end of the inverter bridge, the positive electrode of the DC power supply is connected to the collector of the bus switch tube in the auxiliary commutation circuit, and the emitter of the bus switch tube is connected to the positive end of the inverter bridge;

[0017] The gates of the bus switch tube, the auxiliary switch tube and each main power switch tube in the inverter bridge are all connected to the control circuit, and the control circuit sends a control signal to control the opening and closing of the bus switch tube, the auxiliary switch tube and each main power switch tube in the inverter bridge.

[0018] In some embodiments, the circuit modulation method is applied to the resonant DC link soft-switching inverter as described in the present application, and adopts a discontinuous pulse width modulation strategy. Under the pulse width modulation strategy, the three-phase inverter bridge performs a clamping operation according to a preset clamping rule;

[0019] A sawtooth wave with an alternating positive and negative slope is used as a carrier wave. When the load current of the single-phase inverter bridge is positive, the sawtooth carrier wave slope of the single-phase inverter bridge is positive. When the load current of the single-phase inverter bridge is negative, the sawtooth carrier wave slope of the single-phase inverter bridge is negative.

[0020] The circuit modulation method adopts a shunt dead zone modulation strategy, including:

[0021] The turn-off time of the bus switch tube is earlier than the start time of the zero vector state under the DPWM modulation strategy by a first preset time;

[0022] When the zero vector state begins, the inverter enters the circulating current state. During the circulating current state, the bus switch tube remains in the off state until the auxiliary switch tube is turned on;

[0023] The turn-on time of the auxiliary switch tube is delayed by a second preset time compared to the end time of the zero vector state;

[0024] The turning-on time of the bus switch tube is delayed by a third preset time compared to the turning-on time of the auxiliary switch tube, and the auxiliary switch tube is turned off after the bus switch tube is turned on for a fourth preset time.

[0025] The embodiments of the present disclosure provide a resonant DC link soft-switching inverter and a circuit modulation method thereof, which can achieve the following technical effects:

[0026] The resonant DC link soft-switching inverter and the circuit modulation method thereof provided by the embodiments of the present disclosure can achieve the following technical effects: the auxiliary commutation circuit of the resonant DC link soft-switching inverter has a simple structure, and the number of components used is greatly reduced compared with the auxiliary commutation circuit of the existing soft-switching inverter, thereby reducing the hardware cost; by adopting the DPWM modulation strategy, the three-phase inverter bridge loss is reduced; on the basis of the DPWM modulation strategy, a synchronous modulation strategy is applied to further reduce the three-phase inverter bridge loss; at the same time, a sawtooth wave with alternating positive and negative slopes is used as a carrier to minimize the auxiliary commutation circuit operation frequency and reduce the auxiliary commutation circuit loss; finally, on the basis of the above three, a shunt dead zone modulation strategy is adopted to separate the resonant current in the auxiliary commutation circuit from the load current, thereby greatly reducing the current stress of the auxiliary commutation circuit and its internal components, and further reducing the auxiliary commutation circuit loss; in summary, the efficiency of the resonant DC link soft-switching inverter is improved.

[0027] The above general description and the following description are exemplary and explanatory only and are not intended to limit the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] One or more embodiments are exemplarily described by corresponding drawings, which do not limit the embodiments. Elements with the same reference numerals in the drawings are shown as similar elements, and the drawings do not constitute a scale limitation, and wherein:

[0029] Figure 1 It is a schematic diagram of the circuit principle of an existing soft-switching inverter;

[0030] Figure 2 A schematic diagram of the circuit principle of a resonant DC link soft-switching inverter provided in an embodiment of the present disclosure;

[0031] Figure 3 It is a schematic diagram of the three-phase inverter bridge drive signal of the existing soft-switching inverter under the traditional SPWM triangle carrier modulation strategy;

[0032] Figure 4 A schematic diagram of a three-phase inverter bridge drive signal of a resonant DC link soft-switching inverter under its modulation method provided by an embodiment of the present disclosure;

[0033] Figure 5 A schematic diagram of characteristic operating waveforms of main components of a resonant DC link soft-switching inverter under its modulation method provided by an embodiment of the present disclosure;

[0034] FIG6( a ) is a schematic diagram of an equivalent circuit of a resonant DC link soft-switching inverter in a commutation working mode M0 under its modulation method provided by an embodiment of the present disclosure;

[0035] FIG6( b ) is a schematic diagram of an equivalent circuit of a resonant DC link soft-switching inverter in a commutation working mode M1 under its modulation method provided by an embodiment of the present disclosure;

[0036] FIG6( c ) is a schematic diagram of an equivalent circuit of a resonant DC link soft-switching inverter in a commutation working mode M2 ​​under its modulation method provided by an embodiment of the present disclosure;

[0037] FIG6( d ) is a schematic diagram of an equivalent circuit of a resonant DC link soft-switching inverter in a commutation working mode M3 under its modulation method provided by an embodiment of the present disclosure;

[0038] FIG6(e) is a schematic diagram of an equivalent circuit of a resonant DC link soft-switching inverter in a commutation working mode M4 under its modulation method provided by an embodiment of the present disclosure;

[0039] FIG6( f ) is a schematic diagram of an equivalent circuit of a resonant DC link soft-switching inverter in a commutation working mode M5 under its modulation method provided by an embodiment of the present disclosure;

[0040] FIG6(g) is a schematic diagram of an equivalent circuit of a resonant DC link soft-switching inverter in a commutation working mode M6 under its modulation method provided by an embodiment of the present disclosure;

[0041] FIG6(h) is a schematic diagram of an equivalent circuit of a resonant DC link soft-switching inverter in a commutation working mode M7 under its modulation method provided by an embodiment of the present disclosure;

[0042] FIG6(i) is a schematic diagram of an equivalent circuit of a resonant DC link soft-switching inverter in a commutation working mode M8 under its modulation method provided by an embodiment of the present disclosure;

[0043] FIG6(j) is a schematic diagram of an equivalent circuit of a resonant DC link soft-switching inverter in a commutation working mode M9 under its modulation method provided by an embodiment of the present disclosure;

[0044] FIG6( k ) is a schematic diagram of an equivalent circuit of a resonant DC link soft-switching inverter in a commutation working mode M10 under its modulation method provided by an embodiment of the present disclosure;

[0045] Figure 7 A schematic diagram of simulation waveforms of main components of a resonant DC link soft-switching inverter under its modulation method provided by an embodiment of the present disclosure;

[0046] Figure 8 The voltage v when the first main power switch tube S1 is turned on in a resonant DC link soft switch inverter provided in an embodiment of the present disclosure under its modulation method is S1 and current i S1 Schematic diagram of simulation waveform;

[0047] Fig. 9 The voltage v when the first main power switch tube S1 is turned off in a resonant DC link soft switch inverter provided in an embodiment of the present disclosure under its modulation method is S1 and current i S1 Schematic diagram of simulation waveform;

[0048] Fig.10 The voltage v when the second main power switch tube S2 is turned on in a resonant DC link soft switch inverter provided in an embodiment of the present disclosure under its modulation method is S2 and current i S2 Schematic diagram of simulation waveform;

[0049] Fig.11 The voltage v when the second main power switch tube S2 is turned off in a resonant DC link soft switch inverter provided in an embodiment of the present disclosure under its modulation method is S2 and current i S2 Schematic diagram of simulation waveform;

[0050] Fig.12 The voltage v of the third main power switch tube S3 of a resonant DC link soft-switching inverter provided in an embodiment of the present disclosure under its modulation method is S3 and current i S3 Schematic diagram of simulation waveform;

[0051] Fig.13 The voltage v of the fourth main power switch tube S4 of a resonant DC link soft switching inverter provided in an embodiment of the present disclosure under its modulation method is S4 and current i S4 Schematic diagram of simulation waveform;

[0052] Fig.14 The voltage v of the fifth main power switch tube S5 of a resonant DC link soft switching inverter provided in an embodiment of the present disclosure under its modulation method is S5 and current i S5 Schematic diagram of simulation waveform;

[0053] Fig.15 The voltage v of the sixth main power switch tube S6 of a resonant DC link soft-switching inverter provided in an embodiment of the present disclosure under its modulation method is S6 and current i S6 Schematic diagram of simulation waveform;

[0054] Fig.16 The auxiliary switch tube S of a resonant DC link soft switching inverter under the modulation method provided by the embodiment of the present disclosure is a The voltage at turn-on is v Sa and current i Sa Schematic diagram of simulation waveform;

[0055] Fig.17 The auxiliary switch tube S of a resonant DC link soft switching inverter under the modulation method provided by the embodiment of the present disclosure is a The voltage at off time v Sa and current i Sa Schematic diagram of simulation waveform;

[0056] Fig.18 A bus switch tube S of a resonant DC link soft switch inverter under a modulation method provided by an embodiment of the present disclosure L The voltage at turn-on is v SL and current i SL Schematic diagram of simulation waveform;

[0057] Fig.19 A bus switch tube S of a resonant DC link soft switch inverter under a modulation method provided by an embodiment of the present disclosure L The voltage at off time v SL and current i SL Schematic diagram of simulation waveform;

[0058] Fig. 20 It is a schematic diagram of the simulation waveform of the driving signal of the main power switch tube (S1-S6) in the next switching cycle of the existing soft-switching inverter under the traditional SPWM triangle carrier modulation strategy;

[0059] Fig.21 A schematic diagram of a simulated waveform of a driving signal of a main power switch tube (S1-S6) in a switching cycle of a modulation method of a resonant DC link soft-switching inverter provided in an embodiment of the present disclosure;

[0060] Fig. 22 The DC bus voltage v is the current value of the soft-switching inverter in the conventional SPWM triangle carrier modulation strategy during the next switching cycle. bus Schematic diagram of simulation waveform;

[0061] Fig.23 A resonant DC link soft switching inverter provided in an embodiment of the present disclosure has a DC bus voltage v in a switching cycle in its modulation method. bus Schematic diagram of simulation waveform;

[0062] Fig.24 The first auxiliary resonant inductor L is a conventional SPWM triangle carrier modulation strategy for the existing soft switching inverter in a switching cycle. a1 The current i La1 Schematic diagram of simulation waveform;

[0063] Fig.25A resonant DC link soft switching inverter provided by the embodiment of the present disclosure provides an auxiliary resonant inductor L in the next switching cycle of its modulation method. a The current i La Schematic diagram of simulation waveform;

[0064] Fig.26 A resonant DC link soft switching inverter provided in an embodiment of the present disclosure has a three-phase load current i under its modulation method. A 、i B 、i C Schematic diagram of simulation waveform. DETAILED DESCRIPTION

[0065] In order to be able to understand the features and technical contents of the embodiments of the present disclosure in more detail, the implementation of the embodiments of the present disclosure is described in detail below in conjunction with the accompanying drawings. The attached drawings are for reference only and are not used to limit the embodiments of the present disclosure. In the following technical description, for the convenience of explanation, a full understanding of the disclosed embodiments is provided through multiple details. However, one or more embodiments can still be implemented without these details. In other cases, to simplify the drawings, well-known structures and devices can be simplified for display.

[0066] The terms "first", "second", etc. in the specification and claims of the embodiments of the present disclosure and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the terms used in this way can be interchanged where appropriate, so that the embodiments of the embodiments of the present disclosure described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions.

[0067] Unless otherwise stated, the term "plurality" means two or more.

[0068] In the embodiment of the present disclosure, the character " / " indicates that the preceding and following objects are in an "or" relationship. For example, A / B indicates: A or B.

[0069] The term "and / or" is a description of the association relationship between objects, indicating that three relationships can exist. For example, A and / or B means: A or B, or, A and B.

[0070] The term "correspondence" may refer to an association relationship or a binding relationship. The correspondence between A and B means that there is an association relationship or a binding relationship between A and B.

[0071] Combination Figure 2 The embodiment of the present disclosure provides a resonant DC link soft switching inverter, including: an auxiliary commutation circuit 1, an inverter bridge 2, a load circuit 3, a control circuit 4 and a DC power supply E.

[0072] The auxiliary commutation circuit 1 includes a bus switch tube S L , auxiliary switch tube S a , auxiliary resonant inductor L a , main resonant capacitor C L , auxiliary resonant capacitor C a , the anti-parallel diode D of the bus switch tube L , the first auxiliary diode D a1 , the second auxiliary diode D a2 .

[0073] Busbar switch tube S L The collector is connected to the positive pole of the DC power supply E, and the bus switch tube S L The emitter of is connected to the inverter bridge 2, and the anti-parallel diode D of the bus switch tube L The anode of the busbar switch tube S L The emitter of the bus switch tube is connected in parallel with the diode D L The cathode of the busbar switch tube S is connected L The collector of the main resonant capacitor C L The positive pole is connected to the bus switch tube S L The collector and auxiliary switch tube S a The collector of the main resonant capacitor C L The negative pole is connected to the bus switch tube S L The emitter of the auxiliary switch tube S a The emitter of the auxiliary resonant inductor L a One end of the auxiliary resonant inductor L a The other end is connected to the bus switch tube S L The emitter of the first auxiliary diode D a1 The cathode of the auxiliary switch tube S is connected a The emitter of the first auxiliary diode D a1 The anode of the auxiliary resonant capacitor C a The negative pole of the auxiliary resonant capacitor C a The positive pole is connected to the bus switch tube S L The emitter of the second auxiliary diode D a2 The anode of the second auxiliary diode D is connected to the negative electrode of the DC power supply E. a2 The cathode of the auxiliary resonant capacitor C a of the negative electrode.

[0074] The inverter bridge 2 is a three-phase inverter bridge, including an A-phase inverter bridge, a B-phase inverter bridge and a C-phase inverter bridge.

[0075] The A-phase inverter bridge includes a first main power switch tube S1, an anti-parallel freewheeling diode D1 of the first main power switch tube, a parallel buffer capacitor C1 of the first main power switch tube, a second main power switch tube S2, an anti-parallel freewheeling diode D2 of the second main power switch tube, and a parallel buffer capacitor C2 of the second main power switch tube, wherein the first main power switch tube S1 is the main power switch tube of the upper bridge arm in the A-phase inverter bridge, and the second main power switch tube S2 is the main power switch tube of the lower bridge arm; the emitter of the first main power switch tube S1 is connected to the collector of the second main power switch tube S2, and the lead-out line at the connection point of the first main power switch tube S1 and the second main power switch tube S2 is the A-phase AC output terminal.

[0076] The B-phase inverter bridge includes a third main power switch tube S3, an anti-parallel freewheeling diode D3 of the third main power switch tube, a parallel buffer capacitor C3 of the third main power switch tube, a fourth main power switch tube S4, an anti-parallel freewheeling diode D4 of the fourth main power switch tube and a parallel buffer capacitor C4 of the fourth main power switch tube, wherein the third main power switch tube S3 is the main power switch tube of the upper bridge arm in the B-phase inverter bridge, and the fourth main power switch tube S4 is the main power switch tube of the lower bridge arm; the emitter of the third main power switch tube S3 is connected to the collector of the fourth main power switch tube S4, and the lead-out line at the connection point of the third main power switch tube S3 and the fourth main power switch tube S4 is the B-phase AC output terminal.

[0077] The C-phase inverter bridge includes a fifth main power switch tube S5, an anti-parallel freewheeling diode D5 of the fifth main power switch tube, a parallel buffer capacitor C5 of the fifth main power switch tube, a sixth main power switch tube S6, an anti-parallel freewheeling diode D6 of the sixth main power switch tube and a parallel buffer capacitor C6 of the sixth main power switch tube, wherein the fifth main power switch tube S5 is the main power switch tube of the upper bridge arm in the C-phase inverter bridge, and the sixth main power switch tube S6 is the main power switch tube of the lower bridge arm; the emitter of the fifth main power switch tube S5 is connected to the collector of the sixth main power switch tube S6, and the lead-out line at the connection point of the fifth main power switch tube S5 and the sixth main power switch tube S6 is the C-phase AC output terminal.

[0078] The collectors of the first main power switch tube S1, the third main power switch tube S3 and the fifth main power switch tube S5 in the inverter bridge are connected to each other as the positive end of the inverter bridge 2; the emitters of the second main power switch tube S2, the fourth main power switch tube S4 and the sixth main power switch tube S6 in the inverter bridge are connected to each other as the negative end of the inverter bridge 2.

[0079] The load circuit 3 is a three-phase resistive-inductive load circuit, including a first resistor R A , the second resistor R B , the third resistor R C and the first inductor L A , the second inductor LB , the third inductor L C The first resistor R A , the second resistor R B , the third resistor R C One end of each resistor R is connected to the A phase AC output terminal, the B phase AC output terminal and the C phase AC output terminal respectively. A , the second resistor R B , the third resistor R C The other end of each is connected to the first inductor L A , the second inductor L B , the third inductor L C One end of the first inductor L A , the second inductor L B , the third inductor L C The other ends of the A-phase AC output terminal, the B-phase AC output terminal, and the C-phase AC output terminal output load current i A 、i B and i C After being sampled by the sensor, they are used as input signals d iA ,d iB and d iC They are respectively connected to the control circuit 4.

[0080] The negative pole of the DC power source E is connected to the negative terminal of the inverter bridge 2, and the positive pole of the DC power source E is connected to the bus switch tube S in the auxiliary commutation circuit. L The collector of the bus switch tube S L The emitter of is connected to the positive end of the inverter bridge 2; the anti-parallel diode D of the bus switch tube L The anode of the busbar switch tube S L The emitter of the bus switch tube is connected in parallel with the diode D L The cathode of the busbar switch tube S is connected L The collector.

[0081] Busbar switch tube S L , auxiliary switch tube S a The gates of the first main power switch tube S1, the second main power switch tube S2, the third main power switch tube S3, the fourth main power switch tube S4, the fifth main power switch tube S5 and the sixth main power switch tube S6 in the inverter bridge 2 are all connected to the control circuit 4, and the control circuit 4 sends a control signal d SL ,d Sa ,d S1 ,d S2 ,d S3 ,d S4 ,d S5 ,d S6 Control bus switch tube S separately L, auxiliary switch tube S a And the opening and closing of the first main power switch tube S1, the second main power switch tube S2, the third main power switch tube S3, the fourth main power switch tube S4, the fifth main power switch tube S5, and the sixth main power switch tube S6 in the inverter bridge 2.

[0082] The resonant DC link soft-switching inverter provided in this embodiment has an auxiliary commutation circuit in which the number of components used is greatly reduced compared to the auxiliary commutation circuit of the existing soft-switching inverter, thereby reducing hardware costs.

[0083] Optionally, the bus switch tube, the auxiliary switch tube and the first main power switch tube, the second main power switch tube, the third main power switch tube, the fourth main power switch tube, the fifth main power switch tube and the sixth main power switch tube in the inverter bridge all use fully controlled switching devices.

[0084] Optionally, the fully controlled switch device includes one or more of a silicon-based insulated gate bipolar transistor, a silicon-based metal oxide semiconductor field effect transistor, a gallium nitride high electron mobility transistor, or a silicon carbide metal oxide semiconductor field effect transistor. In this way, the switch circuit can be directly controlled by the control circuit; all fully controlled switch devices realize soft switching, reducing switching losses.

[0085] Optionally, the anti-parallel diode of the bus switch tube, the first auxiliary diode, the second auxiliary diode and the anti-parallel freewheeling diode of the first main power switch tube in the inverter bridge, the anti-parallel freewheeling diode of the second main power switch tube, the anti-parallel freewheeling diode of the third main power switch tube, the anti-parallel freewheeling diode of the fourth main power switch tube, the anti-parallel freewheeling diode of the fifth main power switch tube, and the anti-parallel freewheeling diode of the sixth main power switch tube are all fast recovery diodes or high-frequency diodes.

[0086] Optionally, the DC power supply is a DC voltage source or a voltage source obtained through DC-DC (direct current-direct current) conversion and rectification.

[0087] The resonant DC link soft-switching inverter provided in this embodiment has a simple structure and is applicable to a variety of inverter occasions, and can play an important role in industrial production, transportation, communication systems, power systems, new energy systems, various power supply systems, aerospace and other fields. In some embodiments, in a variable frequency speed regulation system, the working process of the resonant DC link soft-switching inverter of the embodiment of the present disclosure is analyzed.

[0088] In some embodiments, the DC power supply E obtains relatively stable DC power by rectifying three-phase AC power, and inputs the DC power into a resonant DC link soft-switching inverter with a simple structure provided in the embodiment of the present disclosure for power conversion. The specific power conversion process is shown below.

[0089] The existing soft-switching inverter adopts the traditional SPWM triangle carrier modulation strategy, which uses a triangle wave with a fixed slope as the carrier, and generates the driving signal of each main power switch tube by comparing with the three-phase sinusoidal modulation wave of A, B, and C with a phase difference of 120°. The driving signals of the first main power switch tube and the second main power switch tube of the A-phase inverter bridge are complementary and turned on, and the phases are 180° electrical angle apart from each other, the driving signals of the third main power switch tube and the fourth main power switch tube of the B-phase inverter bridge are complementary and turned on, and the phases are 180° electrical angle apart from each other, and the driving signals of the fifth main power switch tube and the sixth main power switch tube of the C-phase inverter bridge are complementary and turned on, and the phases are 180° electrical angle apart from each other. When the main power switch tubes in each phase inverter bridge are commutating, the auxiliary commutation circuit operates in advance to create a DC bus zero voltage groove for the soft switching of each main power switch tube in the inverter bridge. Before the auxiliary commutation circuit operates, the working process of the soft switching inverter is the same as the working process of the traditional hard switching inverter. After the main power switch tubes of the inverter bridge complete the soft switching in the DC bus zero voltage groove, the DC bus voltage returns to the DC power supply voltage, and the commutation process is completed.

[0090] The driving signals of the main power switches in the three-phase inverter bridge of the existing soft-switching inverter under the traditional SPWM triangle carrier modulation strategy are as follows: Figure 3 shown. Figure 3 The B-phase modulation wave signal is less than zero, and the A-phase and C-phase modulation wave signals are greater than zero. Figure 3 The solid line in the three-phase inverter bridge drive signal represents the main power switch tube drive signal in the upper bridge arm of each phase inverter bridge, that is, the drive signal of the first main power switch tube of the A phase inverter bridge, the drive signal of the third main power switch tube of the B phase inverter bridge, and the drive signal of the fifth main power switch tube of the C phase inverter bridge; the dotted line represents the main power switch tube drive signal in the lower bridge arm of each phase inverter bridge, that is, the drive signal of the second main power switch tube in the A phase inverter bridge, the drive signal of the fourth main power switch tube in the B phase inverter bridge, and the drive signal of the sixth main power switch tube in the C phase inverter bridge, v bus is the DC bus voltage, i La1 is the current in the first auxiliary resonant inductor, T s is the switching cycle, I omax is the peak value of the load current.

[0091] Analysis Figure 3It can be seen from the soft switching inverter under the traditional SPWM triangle carrier modulation strategy shown in the figure that: in one switching cycle, the main power switch tube in the three-phase inverter bridge has a total of 6 switching actions. In order to realize the soft switching action of each main power switch tube, the auxiliary commutation circuit needs to form a zero voltage groove on the DC bus. The zero voltage groove is generated by the resonance of the capacitor and the inductor. Therefore, each action of the auxiliary commutation circuit will form a current peak on the auxiliary resonant inductor. The maximum value of the current peak is the current stress of the auxiliary commutation circuit. Further analysis shows that the auxiliary commutation circuit needs to act 6 times to realize the soft switching of the corresponding main power switch tube. During this period, the auxiliary commutation circuit current stress is formed that is approximately twice the peak value of the load current. Obviously, such a large number of actions will bring a lot of losses, and the huge current stress will further amplify this loss.

[0092] The present disclosure provides a modulation method for a resonant DC link soft-switching inverter, including:

[0093] (1) A discontinuous pulse width modulation strategy (DPWM) is adopted. Under the DPWM modulation strategy, at any time, the single-phase inverter bridge that meets the preset conditions in the three-phase inverter bridge performs a clamping operation according to a preset clamping rule. Optionally, the single-phase inverter bridge that meets the preset conditions in the three-phase inverter bridge includes: a single-phase inverter bridge with the largest absolute value of the load current in the three-phase inverter bridge. Optionally, the clamping rule includes: when the load current of the single-phase inverter bridge that meets the preset conditions is positive, the main power switch tube of the upper arm of the single-phase inverter bridge is clamped to the positive pole of the DC power supply; when the load current of the single-phase inverter bridge that meets the preset conditions is negative, the main power switch tube of the lower arm of the single-phase inverter bridge is clamped to the negative pole of the DC power supply. The clamping operation is that one of the main power switch tubes of the single-phase inverter bridge is always kept in the on state, and the main power switch tube on the opposite side of the same bridge arm is always kept in the off state. For example, the load current of the A-phase inverter bridge in the three-phase inverter bridge is positive and has the largest absolute value. The main power switch tube of the upper arm of the A-phase inverter bridge is clamped to the positive pole of the DC power supply. Then, the main power switch tube of the upper arm of the A-phase inverter bridge is always kept in the on state, and the main power switch tube of the lower arm of the A-phase inverter bridge is always kept in the off state.

[0094] (2) Adopting a synchronous modulation strategy. Based on (1), a synchronous modulation strategy is adopted. Under the synchronous modulation strategy, at any time, the single-phase inverter bridge that meets the preset conditions in the three-phase inverter bridge performs a clamping operation according to the preset clamping rule. Optionally, the single-phase inverter bridge that meets the preset conditions in the three-phase inverter bridge includes: a single-phase inverter bridge with the second largest absolute value of the load current in the three-phase inverter bridge. Optionally, the clamping rule includes: when the load current of the single-phase inverter bridge that meets the preset conditions is positive, the main power switch tube of the upper arm of the single-phase inverter bridge is clamped to the positive pole of the DC power supply; when the load current of the single-phase inverter bridge that meets the preset conditions is negative, the main power switch tube of the lower arm of the single-phase inverter bridge is clamped to the negative pole of the DC power supply. Under the combined effect of (1) and (2), the operating frequency of the three-phase inverter bridge is reduced to 1 / 3 of the traditional SPWM (sinusoidal pulse width modulation) triangle carrier modulation strategy, avoiding the loss caused by the frequent operation of the three-phase inverter bridge.

[0095] (3) A sawtooth wave with alternating positive and negative slopes is used as a carrier. When the load current of the single-phase load circuit is positive, the sawtooth carrier slope of the single-phase load circuit is positive; when the load current of the single-phase load circuit is negative, the sawtooth carrier slope of the single-phase load circuit is negative. Under the combined effect of (1), (2) and (3), the operating frequency of the auxiliary commutation circuit is reduced to 1 / 6 of the traditional SPWM triangle carrier modulation strategy, avoiding the loss caused by the frequent operation of the auxiliary commutation circuit.

[0096] (4) Adopting the shunt dead zone modulation strategy, based on (1), (2) and (3), adopting the shunt dead zone modulation strategy can reduce the current stress of the auxiliary commutation circuit and thus reduce the loss caused by the large current. The shunt dead zone modulation strategy is as follows:

[0097] The turn-off time of the bus switch tube is earlier than the start time of the zero vector (000 or 111 switch vector) state under the DPWM modulation strategy (before the synchronous modulation strategy is used) by the first preset time δ1; when the zero vector state starts, the inverter enters the circulating state, during which the bus switch tube remains in the off state until the auxiliary switch tube is turned on; the turn-on time of the auxiliary switch tube is delayed by the second preset time δ2 compared with the end time of the zero vector state; the turn-on time of the bus switch tube is delayed by the third preset time δ3 compared with the turn-on time of the auxiliary switch tube, and the auxiliary switch tube is turned off after the bus switch tube is turned on for the fourth preset time δ4. Optionally, the circulating state is a state in which the three-phase load current circulates in the main power switch tube of the inverter bridge or its anti-parallel freewheeling diode and does not exchange energy with the DC power supply.

[0098] Optionally, the first preset time and the third preset time meet the following conditions: the first preset time δ1 is greater than or equal to the first set threshold, the third preset time δ3 is greater than or equal to the second set threshold, and the sum of the first preset time and the third preset time is less than or equal to the third set threshold. Optionally, δ2 and δ4 are set fixed time periods.

[0099] Optionally, by calculating Get the first set threshold; by calculating Obtain the second set threshold; by calculating Obtain the third set threshold; where Y1 is the first set threshold, E max is the maximum DC power supply voltage, E min is the minimum DC power supply voltage, C a is the capacitance value of the main resonant capacitor, C b is the capacitance value of the auxiliary resonant capacitor, I omax is the load current peak value, Y2 is the second set threshold, L is the inductance value of the auxiliary resonant inductor, Y3 is the third set threshold, T s is the switching cycle.

[0100] The modulation method of the resonant DC link soft-switching inverter provided by the embodiment of the present disclosure reduces the operating frequency of the three-phase inverter bridge to 1 / 3 of the traditional SPWM triangle carrier modulation by adopting the DPWM modulation strategy and the synchronous modulation strategy, thereby reducing the loss of the three-phase inverter bridge; at the same time, the sawtooth wave with alternating positive and negative slopes is used as the carrier to reduce the operating frequency of the auxiliary commutation circuit to 1 / 6 of the traditional SPWM triangle carrier modulation, thereby greatly reducing the loss of the auxiliary commutation circuit; on this basis, the shunt dead zone modulation strategy is adopted to greatly reduce the current stress of the auxiliary commutation circuit, thereby further reducing the loss of the auxiliary commutation circuit; in summary, the efficiency of the resonant DC link soft-switching inverter is improved. Moreover, by adopting the modulation method provided by the embodiment of the present disclosure, the auxiliary commutation circuit of the existing soft-switching inverter can be simplified, and the number of components can be reduced to reduce the hardware cost.

[0101] Combination Figure 4 As shown, Figure 4 A schematic diagram of a three-phase inverter bridge drive signal of a resonant DC link soft-switching inverter under its modulation method provided in an embodiment of the present disclosure. Figure 4The solid line in the three-phase inverter bridge drive signal represents the main power switch tube drive signal in the upper bridge arm of each phase inverter bridge, that is, the drive signal of the first main power switch tube of the A phase inverter bridge, the drive signal of the third main power switch tube of the B phase inverter bridge, and the drive signal of the fifth main power switch tube of the C phase inverter bridge; the dotted line represents the main power switch tube drive signal in the lower bridge arm of each phase inverter bridge, that is, the drive signal of the second main power switch tube in the A phase inverter bridge, the drive signal of the fourth main power switch tube in the B phase inverter bridge, and the drive signal of the sixth main power switch tube in the C phase inverter bridge; bus is the DC bus voltage, i La is the current in the auxiliary resonant inductor, T s is the switching cycle, I omax is the load current peak value; in some embodiments, the absolute value of the load current of the B-phase inverter bridge is the largest and negative, the absolute value of the load current of the C-phase inverter bridge is the second largest and positive, and the absolute value of the load current of the A-phase inverter bridge is the smallest and positive, that is, the slope of the B-phase sawtooth carrier is negative, the slope of the A-phase and C-phase sawtooth carrier is positive, the main power switch tube of the lower bridge arm of the B-phase is clamped to the negative pole of the DC power supply, the main power switch tube of the upper bridge arm of the C-phase is clamped to the positive pole of the DC power supply, and the A-phase inverter bridge switches normally. Figure 4 It can be seen that by adopting the DPWM modulation strategy and the synchronous modulation strategy, the main power switch tubes of the upper and lower bridge arms of the B-phase and C-phase inverter bridges do not perform switching actions, so the number of actions of the auxiliary commutation circuit is reduced from 6 times under the traditional SPWM triangle carrier modulation to 2 times. Figure 4 Further analysis shows that under the DPWM modulation strategy and the synchronous modulation strategy, the two commutation actions of the main power switch tube can be divided into: the commutation action of the main power switch tube to the anti-parallel freewheeling diode on the opposite side of the same bridge arm and the commutation action of the anti-parallel freewheeling diode to the main power switch tube on the opposite side of the same bridge arm. The latter can naturally achieve soft switching with the help of the buffer capacitors in parallel with the upper and lower bridge arms of the inverter bridge. The use of the sawtooth carrier with alternating positive and negative slopes makes the commutation action of the anti-parallel freewheeling diode to the main power switch tube on the opposite side of the same bridge arm located at the vertical edge of the sawtooth carrier. At this moment, the auxiliary commutation circuit can achieve soft switching of the corresponding main power switch tube by operating once. Therefore, under the combined effect of (1), (2) and (3) above, the operating frequency of the three-phase inverter bridge and the auxiliary commutation circuit is reduced to 1 / 3 and 1 / 6 of the traditional SPWM triangle carrier modulation strategy, respectively, avoiding the loss caused by the frequent operation of the three-phase inverter bridge and the auxiliary commutation circuit.

[0102] In some embodiments, the devices used in the resonant DC link soft switching inverter all operate under ideal conditions, ignoring the influence of parasitic parameters on the commutation process; the switching frequency f selected by the resonant DC link soft switching inverter s Greater than the output AC frequency f o , so in a switching state the bus current i busKeep constant; the parallel buffer capacitance value of each main power switch tube in the resonant DC link soft switching inverter is equal, that is, C1=C2=C3=C4=C5=C6, and the main resonant capacitance value C L =3C x .

[0103] Combination Figure 5 As shown, Figure 5 The present disclosure provides a schematic diagram of characteristic operating waveforms of main components of a resonant DC link soft-switching inverter under its modulation method; wherein, v bus is the DC bus voltage, v CL The main resonant capacitor C L Voltage across the terminals, v Ca Auxiliary resonant capacitor C a Voltage across the two ends; i bus is the bus current, i CL The main resonant capacitor C L The current in, i Ca Auxiliary resonant capacitor C a The current in, i La is the auxiliary resonant inductor L a The current in t dead The switching dead time is set to prevent the upper and lower bridge arm switches of the inverter from being turned on at the same time. The resonant DC link soft inverter has 11 working modes M0, M1, M2, M3, M4, M5, M6, M7, M8, M9, and M10 in one commutation process. The equivalent circuit diagrams of the 11 working modes are shown in the figure. Figures 6(a) to 6(k) As shown, the dotted line indicates no action in the corresponding mode, and the mode only includes the solid line loop. The commutation working mode of the loop is specifically analyzed below.

[0104] Mode M0[~t0]: As shown in the equivalent circuit diagram of Figure 6(a), before time t0, the bus switch tube S L The auxiliary switch tube S is turned on. a Shut down, DC power supply through bus switch tube S L Power is supplied to the load and the circuit is in a stable working state.

[0105] Mode M1[t0~t1]: As shown in the equivalent circuit diagram of Figure 6(b), at time t0, the bus switch tube S L Shutdown, bus current i bus Immediately commutates to the main resonant capacitor C L , auxiliary resonant capacitor C a The parallel buffer capacitors C1, C3, and C6 of the first, third, and sixth main power switch tubes, and the voltage across the main resonant capacitor v CL Starting from zero, the voltage across the auxiliary resonant capacitor v CaThe voltage across the parallel buffer capacitor of the first, third, and sixth main power switch tubes is v C1 、v C3 、v C6 The DC power supply voltage E starts to decrease slowly and linearly, and the bus switch tube S L Quasi-ZVS (zero voltage shutdown) is achieved. When the voltage across the auxiliary resonant capacitor v Ca The voltage across the parallel buffer capacitor of the first, third, and sixth main power switch tubes is v C1 、v C3 、v C6 When it drops to zero, the mode ends.

[0106] Mode M2[t1~t2]: As shown in the equivalent circuit diagram of Figure 6(c), at time t1, the voltage across the main resonant capacitor v CL Charged to the DC power supply voltage E, the voltage across the auxiliary resonant capacitor v Ca The voltage across the parallel buffer capacitor of the first, third, and sixth main power switch tubes is v C1 、v C3 、v C6 After discharging to zero, the anti-parallel freewheeling diodes D3 and D6 of the third and sixth main power switch tubes realize ZVS opening, and the circuit is in the circulation state 1 until the first main power switch tube S1 is turned on, and the mode ends.

[0107] Mode M3[t2~t3]: As shown in the equivalent circuit diagram of FIG6(d), at time t2, the first main power switch tube S1 is turned on. At this time, the voltage across the parallel buffer capacitors of each main power switch tube is still zero, so the first main power switch tube S1 realizes ZVZCS turn-on, and the circuit is in the circulation state 2 until the auxiliary switch tube S a Activate, and the mode ends.

[0108] Mode M4 [t3-t4]: As shown in the equivalent circuit diagram of FIG6(e), at time t3, the auxiliary switch tube S a The second, third and sixth main power switch tubes' anti-parallel freewheeling diodes D2, D3 and D6 are connected to the auxiliary resonant inductor L a Auxiliary resonant inductor L a The voltage across the two ends is the DC power supply voltage E. a Under the action, the auxiliary switch tube S a The current i Sa Starting from zero, the auxiliary switch tube S a Quasi-ZCS (zero current) switching is achieved. When the auxiliary resonant inductor L a The current i La Rising to bus current i bus , the mode ends.

[0109] Mode M5 [t4-t5]: As shown in the equivalent circuit diagram of Figure 6(f), at time t4, the auxiliary resonant inductor L a The current i La Rising to bus current i bus After that, the anti-parallel freewheeling diodes D2, D3, and D6 of the second, third, and sixth main power switch tubes are all ZCS-turned off, and the main resonant capacitor C L The parallel buffer capacitors C2, C3, C6 and the auxiliary resonant inductor L of the second, third and sixth main power switch tubes a Resonance occurs. When the voltage across the main resonant capacitor v CL Drops to zero, the voltage across the parallel buffer capacitors of the second, third, and sixth main power switch tubes v C2 、v C3 、v C6 When the DC power supply voltage rises to E, the anti-parallel freewheeling diode D of the bus switch tube L This mode ends.

[0110] Mode M6 [t5-t6]: As shown in the equivalent circuit diagram of Figure 6 (g), at time t5, the voltage across the main resonant capacitor v CL Drops to zero, the voltage across the parallel buffer capacitors of the second, third, and sixth main power switch tubes v C2 、v C3 、v C6 Rising to the DC power supply voltage E, the auxiliary resonant inductor L a The current i La Reach the maximum value i Lamax . The anti-parallel freewheeling diode D of the bus switch tube L During the conduction period, the bus switch tube S is turned on. L The ZVZCS can be turned on. a When it is turned off, this mode ends. Optionally, by calculating The maximum value of the current in the auxiliary resonant inductor is obtained.

[0111] Mode M7 [t6-t7]: As shown in the equivalent circuit diagram of FIG6(h), at time t6, the auxiliary switch tube S a Turn off, the first auxiliary diode D a1 The auxiliary resonant capacitor C a and auxiliary resonant inductor L a Resonance starts, bus current i bus Immediately switch to bus switch tube S L The voltage across the auxiliary resonant capacitor is v Ca Starting from zero, the resonance rises slowly, and the auxiliary switch tube S a Quasi-ZVS shutdown is achieved. When the auxiliary resonant capacitor C a This mode ends when the DC power supply voltage E is charged.

[0112] Mode M8 [t7-t8]: As shown in the equivalent circuit diagram of Figure 6 (i), at time t7, the auxiliary resonant capacitor C a is charged to the DC power supply voltage E, the second auxiliary diode D a2 Auxiliary resonant inductor L a Through the first auxiliary diode D a1 , the second auxiliary diode D a2 And the anti-parallel freewheeling diode D of the bus switch tube L Feedback energy to the DC power supply. Auxiliary resonant inductor L a The current i La Linearly decreases when the auxiliary resonant inductor L a The current i La Reduced to bus current i bus , the mode ends.

[0113] Mode M9 [t8-t9]: As shown in the equivalent circuit diagram of Figure 6(j), at time t8, the auxiliary resonant inductor L a The current i La Reduced to bus current i bus , under the action of the DC power supply voltage E, the auxiliary resonant inductor L a The current i La Continue to decrease linearly, the bus switch tube S L The current i SL Starting from zero, the bus current i bus Starting from the auxiliary resonant inductor L a To the bus switch tube S L Linear transfer. When the auxiliary resonant inductor L a The current i La When the first auxiliary diode D a1 and the second auxiliary diode D a2 Shutdown, bus current i bus To the bus switch tube S L The transfer is complete and the mode ends.

[0114] Mode M10 [t9~t 10 ]: As shown in the equivalent circuit diagram of Figure 6(k), at time t9, the bus current i bus To the bus switch tube S L After the transfer is completed, the DC power is transferred through the bus switch tube S L Provide stable power to the load and prepare for the next commutation process.

[0115] Through the analysis of the action principle, it can be seen that in mode M1 within the shunt dead zone δ1, the auxiliary resonant capacitor C aThe energy is obtained by using the bus current i bus Fully released, the maximum current flowing through the auxiliary commutation circuit is i Lamax . Auxiliary resonant capacitor C a The maximum current flowing through the auxiliary commutation circuit is approximately equal to the bus current i bus The peak value, that is, the peak value of the load current I omax It effectively avoids the problem of superposition of the resonant current generated by the auxiliary commutation circuit and the load current, thereby greatly reducing the current stress of the auxiliary switch tube and the loss of the auxiliary commutation circuit.

[0116] To verify the correctness of the above theory, according to Figure 2 A simulation platform was built based on the circuit schematic shown in the figure for verification, and the corresponding simulation results are shown below.

[0117] Under the modulation method provided in the embodiment of the present disclosure, the simulation waveforms of the main components of the resonant DC link soft switching inverter provided in the embodiment of the present disclosure are as follows: Figure 7 As shown, from Figure 7 It can be seen from the above simulation waveform and Figure 5 The characteristic working waveforms shown are consistent, proving the correctness of the commutation working mode.

[0118] Under the modulation method provided in the embodiment of the present disclosure, the voltage v when the first main power switch tube S1 of the resonant DC link soft switching inverter provided in the embodiment of the present disclosure is turned on and off S1 and current i S1 The simulation waveform is as follows Figure 8 and Fig. 9 As shown, from Figure 8 In the I region, we can see that the voltage v of the first main power switch tube S1 S1 After a period of time when the linear discharge reaches zero, the first main power switch tube S1 is turned on, so the first main power switch tube S1 realizes ZVZCS turning on; Fig. 9 It can be seen from the II area that after the first main power switch tube S1 is turned off, the voltage v across its two ends S1 It rises linearly from zero, so the first main power switch tube S1 achieves quasi-ZVS shutdown.

[0119] Under the modulation method provided in the embodiment of the present disclosure, the voltage v when the second main power switch tube S2 of the resonant DC link soft switching inverter provided in the embodiment of the present disclosure is turned on and off S2 and current i S2 The simulation waveform is as follows Fig.10 and Fig.11 As shown, from Fig.10 The voltage v of the second main power switch tube S2 can be seen in the I area S2After the linear discharge reaches zero, the second main power switch tube S2 is turned on, but its current i S2 Keep it at zero, so the second main power switch tube S2 realizes ZVZCS opening; Fig.11 It can be seen from the II area that after the second main power switch tube S2 is turned off, the voltage v across its two ends S2 It starts to resonate from zero, but its current i S2 Still remains zero, so the second main power switch tube S2 achieves ZVZCS shutdown.

[0120] Under the modulation method provided in the embodiment of the present disclosure, the voltage v of the third main power switch tube S3 of the resonant DC link soft switching inverter provided in the embodiment of the present disclosure is S3 and current i S3 The simulation waveform is as follows Fig.12 As shown, the voltage v of the fourth main power switch tube S4 S4 and current i S4 The simulation waveform is as follows Fig.13 As shown. Fig.12 It can be seen that the current i of the third main power switch tube S3 S3 is always zero, so the third main power switch tube S3 remains in the off state; Fig.13 It can be seen that the current i of the fourth main power switch tube S4 S4 It is not zero all the time, so the fourth main power switch tube S4 remains in the on state. Therefore, in this interval, there is no switching action between the third main power switch tube S3 and the fourth main power switch tube S4.

[0121] Under the modulation method provided in the embodiment of the present disclosure, the voltage v of the fifth main power switch tube S5 of the resonant DC link soft-switching inverter provided in the embodiment of the present disclosure is S5 and current i S5 The simulation waveform is as follows Fig.14 As shown, the voltage v of the sixth main power switch tube S6 S6 and current i S6 The simulation waveform is as follows Fig.15 As shown. Fig.14 It can be seen that the current i of the fifth main power switch tube S5 S5 is not zero, so the fifth main power switch tube S5 remains on; Fig.15 It can be seen that the current i of the sixth main power switch tube S6 S6 The sixth main power switch tube S6 is always zero, so the sixth main power switch tube S6 remains in the off state. Therefore, in this interval, the fifth main power switch tube S5 and the sixth main power switch tube S6 do not have a switching action.

[0122] Under the modulation method provided in the embodiment of the present disclosure, the auxiliary switch tube S of the resonant DC link soft switching inverter provided in the embodiment of the present disclosure aThe voltage at turn-on and turn-off is v Sa and current i Sa The simulation waveform is as follows Fig.16 and Fig.17 As shown, from Fig.16 The I region shows that the auxiliary switch S a After opening, the current flows through the auxiliary switch tube S a The current i Sa Starting from zero, the auxiliary switch S a Achieved quasi-ZCS opening; Fig.17 In the II area, it can be seen that the auxiliary switch tube S a After shutdown, the auxiliary switch tube S a The voltage across the two ends is v Sa Starting from zero, the resonance rises slowly, so the auxiliary switch tube S a A quasi-ZVS shutdown is achieved.

[0123] Under the modulation method provided in the embodiment of the present disclosure, the bus switch tube S of the resonant DC link soft switching inverter provided in the embodiment of the present disclosure L The voltage at turn-on and turn-off is v SL and current i SL The simulation waveform is as follows Fig.18 and Fig.19 As shown, from Fig.18 The I area shows that the busbar switch tube S L The voltage across the two ends is v SL After the resonance drops to zero for a period of time, the bus switch tube S L It is only turned on, so the bus switch tube S L The ZVZCS was opened; Fig.19 In the II area, it can be seen that the busbar switch tube S L After shutdown, the voltage across its two ends is v SL It starts from zero and rises linearly, so the bus switch tube S L A quasi-ZVS shutdown is achieved.

[0124] The above switching tube action waveforms illustrate that, under the improved modulation method provided in the embodiment of the present disclosure, all switching tubes of the resonant DC link soft-switching inverter provided in the embodiment of the present disclosure achieve soft switching.

[0125] Under the traditional SPWM triangle carrier modulation strategy, the drive signal V of each main power switch tube in a switching cycle of the existing soft switching inverter is gs1 ~V gs6 The simulation waveform is as follows Fig. 20 As shown; under the modulation method provided in the embodiment of the present disclosure, the drive signal V of each main power switch tube of the resonant DC link soft switching inverter provided in the embodiment of the present disclosure in one switching cycle gs1~V gs6 The simulation waveform is as follows Fig.21 As shown. By comparing the two, it can be seen that: in one switching cycle, under the traditional SPWM triangle carrier modulation strategy, the main power switch tube switches 6 times, while under the modulation method provided in the embodiment of the present disclosure, the main power switch tube only switches 2 times. Therefore, the operation frequency of the three-phase inverter bridge under the modulation method provided in the embodiment of the present disclosure is reduced to 1 / 3 of the traditional SPWM triangle carrier modulation strategy. Since each switching action of the main power switch tube is accompanied by switching loss, even if it is in a soft switching state, there is still a certain switching loss. Therefore, the modulation method provided in the embodiment of the present disclosure can reduce the loss of the three-phase inverter bridge and improve the efficiency of the resonant DC link soft switching inverter.

[0126] Under the traditional SPWM triangle carrier modulation strategy, the DC bus voltage v bus The simulation waveform is as follows Fig. 22 As shown; under the modulation method provided in the embodiment of the present disclosure, the DC bus voltage v of the resonant DC link soft switching inverter provided in the embodiment of the present disclosure is within one switching cycle bus The simulation waveform is as follows Fig.23 As shown. By comparing the two, it can be seen that: in one switching cycle, under the traditional SPWM triangle carrier modulation strategy, 6 zero voltage grooves appear on the DC bus, while under the modulation method provided in the embodiment of the present disclosure, there is only 1 zero voltage groove on the DC bus. The number of zero voltage grooves represents the number of times the auxiliary commutation circuit operates. Therefore, the operation frequency of the auxiliary commutation circuit under the modulation method provided in the embodiment of the present disclosure is reduced to 1 / 6 of the traditional SPWM triangle carrier modulation strategy. Since each occurrence of a zero voltage groove will cause a certain loss in the auxiliary commutation circuit, the modulation method provided in the embodiment of the present disclosure can greatly reduce the loss of the auxiliary commutation circuit, thereby greatly improving the efficiency of the resonant DC link soft switching inverter.

[0127] Under the traditional SPWM triangle carrier modulation strategy, the first auxiliary resonant inductor L a1 The current i La1 The simulation waveform is as follows Fig.24 As shown; under the modulation method provided in the embodiment of the present disclosure, the resonant DC link soft switching inverter provided in the embodiment of the present disclosure assists the resonant inductor L in one switching cycle a The current i La The simulation waveform is as follows Fig.25 As shown. By comparing the two, it can be seen that: in one switching cycle, under the traditional SPWM triangle carrier modulation strategy, the first auxiliary resonant inductor L a1 The current i La1There are 6 peaks, and the maximum peak current is 103.0A. Under the modulation method provided in the embodiment of the present disclosure, the auxiliary resonant inductor L a The current i La Only one peak appears, and its maximum peak current is 52.5A. The number of peaks of the auxiliary resonant inductor current and its maximum peak current represent the number of actions of the auxiliary commutation circuit and its current stress, which once again illustrates that the action frequency of the auxiliary commutation circuit under the modulation method provided in the embodiment of the present disclosure is reduced to 1 / 6 of the traditional SPWM triangle carrier modulation strategy. At the same time, due to the significant reduction in current stress, the auxiliary commutation circuit loss can be further reduced, thereby further improving the efficiency of the resonant DC link soft-switching inverter.

[0128] Under the modulation method provided in the embodiment of the present disclosure, the three-phase load current i of the resonant DC link soft switching inverter provided in the embodiment of the present disclosure is A 、i B 、i C The simulation waveform is as follows Fig.26 As shown, from Fig.24 It can be seen that the three-phase load current i of the resonant DC link soft switching inverter A 、i B 、i C The waveform is still smooth and the distortion is small, which indicates that the auxiliary commutation circuit and modulation method provided by the embodiments of the present disclosure have no effect on the normal operation of the inverter.

[0129] The auxiliary commutation circuit of the resonant DC link soft-switching inverter provided by the embodiment of the present disclosure has a simple structure, and the number of components used is greatly reduced compared with the auxiliary commutation circuit of the existing soft-switching inverter, thereby reducing the hardware cost; the operating frequency of the three-phase inverter bridge of the resonant DC link soft-switching inverter is reduced to 1 / 3 of the traditional SPWM triangle carrier modulation strategy, thereby reducing the loss of the three-phase inverter bridge; the operating frequency of the auxiliary commutation circuit of the resonant DC link soft-switching inverter is reduced to 1 / 6 of the traditional SPWM triangle carrier modulation strategy, thereby greatly reducing the loss of the auxiliary commutation circuit; on this basis, a shunt dead zone modulation strategy is applied to separate the resonant current in the auxiliary commutation circuit from the load current, thereby greatly reducing the current stress of the auxiliary commutation circuit and its internal components, and further reducing the loss of the auxiliary commutation circuit; in summary, the efficiency of the resonant DC link soft-switching inverter is greatly improved.

[0130] The above description and the accompanying drawings sufficiently illustrate the 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. Unless explicitly required, individual components and functions are optional, and the order of operations may vary. Portions and features of some embodiments may be included in or replace portions and features of other embodiments. The 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 the scope thereof. The scope of the present disclosure is limited only by the appended claims.

Claims

1. A resonant DC link soft switching inverter, characterized in that: include: Auxiliary commutation circuit, inverter bridge, load circuit, control circuit and DC power supply; The auxiliary commutation circuit includes a bus switch tube, an auxiliary switch tube, an auxiliary resonant inductor, a main resonant capacitor, an auxiliary resonant capacitor, an anti-parallel diode of the bus switch tube, a first auxiliary diode, and a second auxiliary diode; The collector of the bus switch tube is connected to the positive electrode of the DC power supply, the emitter of the bus switch tube is connected to the inverter bridge, the anode of the anti-parallel diode of the bus switch tube is connected to the emitter of the bus switch tube, and the cathode of the anti-parallel diode of the bus switch tube is connected to the collector of the bus switch tube; The positive electrode of the main resonant capacitor is connected to the collector of the bus switch tube and the collector of the auxiliary switch tube, the negative electrode of the main resonant capacitor is connected to the emitter of the bus switch tube, the emitter of the auxiliary switch tube is connected to one end of the auxiliary resonant inductor, and the other end of the auxiliary resonant inductor is connected to the emitter of the bus switch tube; The cathode of the first auxiliary diode is connected to the emitter of the auxiliary switch tube, the anode of the first auxiliary diode is connected to the negative electrode of the auxiliary resonant capacitor, the positive electrode of the auxiliary resonant capacitor is connected to the emitter of the bus switch tube, the anode of the second auxiliary diode is connected to the negative electrode of the DC power supply, and the cathode of the second auxiliary diode is connected to the negative electrode of the auxiliary resonant capacitor; The inverter bridge is a three-phase inverter bridge, the collectors of the upper bridge arm main power switch tubes of each phase inverter bridge are connected to each other as the positive end of the inverter bridge, and the emitters of the lower bridge arm main power switch tubes of each phase inverter bridge are connected to each other as the negative end of the inverter bridge; The load circuit is a three-phase load circuit, and each phase load circuit includes a resistor and an inductor; one end of the resistor in the three-phase load circuit is respectively connected to three single-phase AC output ends of the three-phase inverter bridge, the other end of the resistor in the three-phase load circuit is respectively connected to one end of three inductors, and the other ends of the three inductors are connected to each other as a load neutral point, and the load currents output by the three single-phase AC output ends are sampled by sensors and respectively input into the control circuit as input signals; The negative electrode of the DC power supply is connected to the negative end of the inverter bridge, the positive electrode of the DC power supply is connected to the collector of the bus switch tube in the auxiliary commutation circuit, and the emitter of the bus switch tube is connected to the positive end of the inverter bridge; The gates of the bus switch tube, the auxiliary switch tube and each main power switch tube in the inverter bridge are all connected to the control circuit, and the control circuit sends a control signal to control the opening and closing of the bus switch tube, the auxiliary switch tube and each main power switch tube in the inverter bridge.

2. The resonant DC link soft switching inverter according to claim 1, characterized in that: Each phase of the inverter bridge comprises an upper bridge arm main power switch tube, an anti-parallel freewheeling diode of the upper bridge arm main power switch tube, a parallel buffer capacitor of the upper bridge arm main power switch tube, a lower bridge arm main power switch tube, an anti-parallel freewheeling diode of the lower bridge arm main power switch tube and a parallel buffer capacitor of the lower bridge arm main power switch tube. The emitter of the upper bridge arm main power switch tube in each phase of the inverter bridge is connected to the collector of the lower bridge arm main power switch tube, and the lead-out line at the connection point of the upper bridge arm main power switch tube and the lower bridge arm main power switch tube is a single-phase AC output terminal.

3. The resonant DC link soft switching inverter according to claim 1, characterized in that: The bus switch tube, the auxiliary switch tube and each main power switch tube in the inverter bridge are all fully controlled switch devices.

4. The resonant DC link soft switching inverter according to claim 3, characterized in that: The fully controlled switch device includes one or more of a silicon-based insulated gate bipolar transistor, a silicon-based metal oxide semiconductor field effect transistor, a gallium nitride high electron mobility transistor or a silicon carbide metal oxide semiconductor field effect transistor.

5. The resonant DC link soft switching inverter according to claim 1, characterized in that: The anti-parallel diode of the bus switch tube, the first auxiliary diode, the second auxiliary diode and the anti-parallel freewheeling diode of each main power switch tube in the inverter bridge are all fast recovery diodes or high-frequency diodes.

6. The resonant DC link soft switching inverter according to claim 1, characterized in that: The DC power supply is a DC voltage source or a voltage source obtained through DC-DC conversion and rectification.

7. A circuit modulation method, characterized in that: Applied to the resonant DC link soft-switching inverter according to any one of claims 1 to 6, a discontinuous pulse width modulation strategy is adopted, under which the three-phase inverter bridge performs a clamping operation according to a preset clamping rule; A sawtooth wave with an alternating positive and negative slope is used as a carrier wave. When the load current of the single-phase inverter bridge is positive, the sawtooth carrier wave slope of the single-phase inverter bridge is positive. When the load current of the single-phase inverter bridge is negative, the sawtooth carrier wave slope of the single-phase inverter bridge is negative. The circuit modulation method adopts a shunt dead zone modulation strategy, including: The turn-off time of the bus switch tube is earlier than the start time of the zero vector state under the DPWM modulation strategy by a first preset time; When the zero vector state begins, the inverter enters the circulating current state. During the circulating current state, the bus switch tube remains in the off state until the auxiliary switch tube is turned on; The turn-on time of the auxiliary switch tube is delayed by a second preset time compared to the end time of the zero vector state; The turning-on time of the bus switch tube is delayed by a third preset time compared to the turning-on time of the auxiliary switch tube, and the auxiliary switch tube is turned off after the bus switch tube is turned on for a fourth preset time.

8. The circuit modulation method according to claim 7, characterized in that: The discontinuous pulse width modulation strategy is adopted. Under the pulse width modulation strategy, the clamping rules of the three-phase inverter bridge include: At any time, the single-phase inverter bridge with the largest absolute value of the load current in the three-phase inverter bridge is clamped. If the load current of this phase is positive, the main power switch tube of the upper bridge arm of the single-phase inverter bridge is clamped to the positive electrode of the DC power supply; if the load current of this phase is negative, the main power switch tube of the lower bridge arm of the single-phase inverter bridge is clamped to the negative electrode of the DC power supply; and, On the basis of the pulse width modulation strategy, a synchronous modulation strategy is applied. Under the synchronous modulation strategy, the clamping rule of the three-phase inverter bridge is as follows: at any time, the single-phase inverter bridge with the second largest absolute value of the load current in the three-phase inverter bridge is clamped. If the load current of this phase is positive, the main power switch tube of the upper bridge arm of the single-phase inverter bridge is clamped to the positive pole of the DC power supply; if the load current of this phase is negative, the main power switch tube of the lower bridge arm of the single-phase inverter bridge is clamped to the negative pole of the DC power supply.

9. The circuit modulation method according to claim 7, characterized in that: The conditions satisfied by the first preset time and the third preset time are: the first preset time is greater than or equal to the first set threshold, the third preset time is greater than or equal to the second set threshold, and the sum of the first preset time and the third preset time is less than or equal to the third set threshold.

10. The circuit modulation method according to claim 9, characterized in that: By calculation Obtaining a first set threshold value; By calculation Obtaining a second set threshold value; By calculation obtaining a third set threshold value; Among them, Y1 is the first set threshold, E max is the maximum DC power supply voltage, E min is the minimum DC power supply voltage, C a is the capacitance value of the main resonant capacitor, C b is the capacitance value of the auxiliary resonant capacitor, I omax is the load current peak value, Y2 is the second set threshold, L is the inductance value of the auxiliary resonant inductor, Y3 is the third set threshold, T s is the switching cycle.

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