A three-phase modular parallel hybrid LCL filter converter and a coordinated current compensation SPWM control method thereof

Abstract

The application discloses a three-phase modular parallel hybrid LCL filter converter and a coordinated current compensation SPWM control method thereof. The proposed modular hybrid converter topology focuses on the modular parallel of the traditional three-phase half-bridge inverter circuit topology, wherein the silicon-based module switch adopts a silicon-based insulated gate bipolar transistor, and the other silicon carbide module switch adopts a silicon carbide-based metal oxide semiconductor field effect transistor. The proposed coordinated current compensation SPWM control method focuses on the large current ripple generated by the silicon-based module, and realizes the low current ripple of the alternating current side load by making the silicon carbide module generate the coordinated current compensation. Meanwhile, the LCL filter is adopted, so that the cost and the filter volume are further reduced under the condition that the performance is similar to that of the full silicon carbide-based power device, and the method has a good engineering promotion prospect.

Description

Technical Field

[0001] This invention relates to the field of power electronics technology, and more particularly to the field of three-phase modular parallel hybrid converters and corresponding control methods. Background Technology

[0002] The rapid development of electric vehicles has fueled the booming market for inverters in low-voltage applications. Modular parallel converters, in particular, have become a research hotspot in both academia and industry due to their advantages such as low cost from modular production and low current ripple from parallel connections. On the other hand, wide-bandgap semiconductor switching devices such as silicon carbide offer advantages over traditional silicon-based semiconductor devices, including lower switching losses and higher operating frequencies, making them well-suited to the high power density and high efficiency development trends of power electronic converters.

[0003] However, the high price has become an obstacle to its widespread adoption. The paper "WBG and Si Hybrid Half-Bridge Power Processing Toward Optimal Efficiency, Power Quality, and Cost Tradeoff" (IEEE Transactions on Power Electronics, 2022, 37) proposes a hybrid half-bridge parallel DC-DC converter using silicon and silicon carbide devices. It achieves low current ripple and high conversion efficiency. However, the proposed converter is only suitable for DC-DC conversion applications and does not provide in-depth research on DC-AC inverter applications. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing technologies. This invention proposes a three-phase modular parallel hybrid LCL filter converter and its coordinated current compensation SPWM control method. The proposed modular hybrid converter topology focuses on modularizing and paralleling the traditional three-phase half-bridge inverter circuit topology. The silicon-based module switch uses silicon-based insulated-gate bipolar transistors (IGBTs) operating at low frequencies, while the other silicon carbide module switch uses silicon carbide metal-oxide-semiconductor (MOSFET) field-effect transistors (MOSFETs) operating at high frequencies, thus balancing high performance and low cost, combining the advantages of both hybrid and parallel converters. The proposed coordinated current compensation SPWM control method addresses the large current ripple generated by the silicon-based module by enabling coordinated current compensation in the silicon carbide module, achieving low current ripple in the AC load. Simultaneously, the use of an LCL filter further reduces cost and filter size while achieving performance similar to all-silicon carbide power devices, making it highly promising for engineering applications.

[0005] The technical solution of the present invention is as follows:

[0006] This invention first provides a three-phase modular parallel hybrid LCL filter converter topology, which includes a first DC power supply, a second DC power supply, a first phase circuit, a second phase circuit, and a third phase circuit with identical structures connected in parallel, and three AC-side loads or a three-phase power grid; the anode of the first DC power supply leads to the first DC bus power terminal; the cathode of the first DC power supply is connected to the anode of the second DC power supply and leads to the DC bus neutral point; the cathode of the second DC power supply leads to the second DC bus power terminal.

[0007] Each phase circuit includes a silicon-based half-bridge module, a silicon carbide half-bridge module, a silicon-based module inductor, a silicon carbide module inductor, a filter capacitor, and an AC-side inductor. The collector of the upper arm of the silicon-based half-bridge module is connected to the first DC bus power terminal, and the emitter of the lower arm of the silicon-based half-bridge module is connected to the second DC bus power terminal. Similarly, the collector of the upper arm of the silicon carbide half-bridge module is connected to the first DC bus power terminal, and the emitter of the lower arm of the silicon carbide half-bridge module is connected to the second DC bus power terminal. The silicon-based module inductor L... 1x One side is connected to the common terminal of the upper and lower bridge arms of the silicon-based half-bridge module; the silicon carbide module inductor L 2x One side is connected to the common terminal of the upper and lower bridge arms of the silicon carbide half-bridge module; the silicon-based module inductor L 1x The other side is connected to the silicon carbide module inductor L 2x The other side is connected to and leads out to the inverter-side output terminal; the load-side inductor L s One side and filter capacitor C f One side is connected to the inverter output terminal;

[0008] The three filter capacitors C of the first phase circuit, the second phase circuit, and the third phase circuit f The other side is interconnected; the three load-side inductors L of the first phase circuit, the second phase circuit, and the third phase circuit are... s The other side is connected to three AC loads or three-phase power grids respectively, and the other side of the three AC loads or three-phase power grids is connected to the load neutral point or power grid neutral point.

[0009] As a preferred embodiment of the present invention, the upper bridge arm switch S of the silicon-based half-bridge module 1x and lower bridge arm switch S 2x All are silicon-based insulated-gate bipolar transistors; the upper bridge arm switch S of the silicon carbide half-bridge module 3x and bridge arm lower switch S 4x All are silicon carbide-based metal oxide semiconductor field-effect transistors.

[0010] Furthermore, the switching frequency of the silicon carbide half-bridge module is 10 to 30 times that of the silicon-based half-bridge module.

[0011] The present invention also provides a coordinated current compensation SPWM control method for the above-mentioned three-phase modular parallel hybrid LCL filter converter topology, which includes the following steps:

[0012] Starting from the given three-phase sinusoidal reference voltage of the silicon-based half-bridge module, the three-phase fundamental frequency voltage of the silicon carbide half-bridge module that makes the output current of the silicon carbide half-bridge module zero is calculated, and the magnitude of the output current ripple of the silicon-based half-bridge module is predicted. In order to compensate for the silicon-based current, the coordination compensation voltage of the silicon carbide half-bridge module is calculated and added to the three-phase fundamental frequency voltage of the silicon carbide half-bridge module to obtain the new three-phase reference voltage of the silicon carbide half-bridge module. The reference voltage of the silicon-based half-bridge module and the new reference voltage of the silicon carbide half-bridge module are used as the modulation wave of the silicon-based half-bridge module and the modulation wave of the silicon carbide half-bridge module, respectively. They are compared with the carrier wave to determine the switching state and switching time of each bridge arm of the three phases, and finally converted into 12-channel PWM signals.

[0013] Compared with existing technologies, the three-phase modular parallel hybrid LCL filter converter and its coordinated current compensation SPWM control method proposed in this invention are applicable to three-phase low-voltage DC-AC inverter applications. The load side can be connected to an RL load or to the power grid. By coordinating and compensating for the large current generated by the low-frequency silicon-based module using a high-frequency silicon carbide module, the ripple size on the load side is significantly reduced. Simultaneously, the use of an LCL filter further reduces the overall size of the converter. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the three-phase circuit topology of a modular parallel hybrid LCL filter converter.

[0015] Figure 2 This is a schematic diagram of the three-phase circuit topology of a grid-connected modular parallel hybrid LCL filter converter.

[0016] Figure 3 This is a schematic diagram of the single-phase circuit topology and equivalent circuit of a modular parallel hybrid LCL filter converter.

[0017] Figure 4 The flowchart shows the coordinated current compensation SPWM control method applied to the converter.

[0018] Figure 5 A schematic diagram of the SPWM control method for coordinating current compensation.

[0019] Figure 6 This is a single-phase load current waveform in one embodiment.

[0020] Figure 7 This is a Fourier spectrum analysis diagram of the single-phase load current in one embodiment.

[0021] Figure 8This is a modulation waveform of the silicon carbide module in one embodiment. Detailed Implementation

[0022] The embodiments of the present invention are described in detail below. These embodiments are implemented based on the technical solution of the present invention, and provide detailed implementation methods and specific operation processes. However, the scope of protection of the present invention is not limited to the following embodiments.

[0023] As power electronic converters continue to evolve towards higher efficiency and higher power density, traditional silicon power devices can no longer meet the requirements for low heat loss at high frequencies. Wide bandgap devices, represented by silicon carbide (SiC), offer lower switching losses and higher operating frequencies compared to traditional silicon power devices, making them suitable for new high-frequency applications. However, considering the high cost of wide bandgap devices, we employ a hybrid parallel topology of silicon-based and SiC device modules, using LCL filtering to further reduce the converter's size and cost. For this hybrid parallel topology, a coordinated current compensation method is used to achieve low current ripple on the load side, achieving performance similar to all-SiC devices while balancing efficiency and cost.

[0024] like Figure 1 As shown, the three-phase modular parallel hybrid LCL filter converter has a completely identical topology consisting of a first-phase circuit, a second-phase circuit, and a third-phase circuit connected in parallel with each other, as well as three AC-side loads. Figure 2 For the grid-connected modular parallel hybrid LCL filter converter three-phase circuit topology, and Figure 1 The difference lies in replacing the three AC-side loads with a three-phase power grid, while the three-phase circuit topology of the converter remains the same for the other parts.

[0025] by Figure 1 For example, the circuit topology of the present invention will be further described. The first DC power supply anode leads to the first DC bus power terminal; the first DC power supply cathode is connected to the second DC power supply anode and leads to the DC bus neutral point (O); the second DC power supply cathode leads to the second DC bus power terminal.

[0026] like Figure 3 As shown, each phase circuit includes a silicon-based half-bridge module, a silicon carbide half-bridge module, a silicon-based module inductor, a silicon carbide module inductor, a filter capacitor, and an AC-side inductor; wherein, the silicon-based half-bridge module consists of an upper switch S 1x and the lower switch S 2x Composition. All switches are silicon-based insulated-gate bipolar transistors. Upper switch S 1x The collector is connected to the power terminal of the first silicon-based module, and the lower switch S... 2x The emitter is connected to the power terminal of the second silicon-based module; the upper switch S 1xThe emitters are respectively connected to the lower switch S. 2x The collector of the silicon carbide half-bridge module is led out from its common terminal to the output terminal of the silicon-based module. Each of the aforementioned silicon carbide half-bridge modules consists of an upper switch S. 3x and the lower switch S 4x Composition. All switches are silicon carbide-based metal-oxide-semiconductor field-effect transistors. Upper switch S 3x The collector is connected to the first silicon carbide module power terminal, and the lower switch S... 4x The emitter is connected to the power terminal of the second silicon carbide module; the upper switch S 3x The emitter is connected to the lower switch S. 4x The collector of the silicon carbide module is led out from its common terminal to the output terminal.

[0027] The first silicon-based module power terminal is connected to the first DC bus power terminal; the second silicon-based module power terminal is connected to the second DC bus power terminal; the first silicon carbide module power terminal is connected to the first DC bus power terminal; and the second silicon carbide module power terminal is connected to the second DC bus power terminal.

[0028] The silicon-based module inductor L 1x One side is connected to the output terminal of the silicon-based module; the silicon carbide module inductor L 2x One side is connected to the output terminal of the silicon carbide module; the silicon-based module inductor L 1x The other side is connected to the silicon carbide module inductor L. 2x The inverter-side output terminal is led out from the other side; the load-side inductor L s One side is connected to the filter capacitor C f On one side, the common terminal is connected to the inverter output terminal; the three filter capacitors C f The other side is connected to each other; the load measuring resistor R s One side is connected to the load-side inductor L s On the other side; the load measuring resistance R s The other side is connected to the load neutral point N.

[0029] for Figure 2 In this context, the three load-side inductors L of the first phase circuit, the second phase circuit, and the third phase circuit... s The other side is connected to the three-phase power grid, and the other side of the three-phase power grid is connected to the neutral point (N) of the power grid.

[0030] In this invention, the three output levels of each phase circuit of the converter are defined as N, O, and P, respectively; for the three output levels, four switching states are selected and defined as S1, S2, S3, S4, S5, S6, S7, S8, S9, S1 ... 2_P S 2_NS3; According to the switching function shown in Equation 1, the four switching states can be represented as shown in Table 1;

[0031]

[0032] Table 1. Four switch states and their corresponding output levels

[0033]

[0034]

[0035] like Figure 3 and Figure 4 As shown, the steps and methods of the coordinated current compensation SPWM control method are as follows: Starting from the given fundamental frequency three-phase sinusoidal reference voltage of the silicon-based half-bridge module, calculate the fundamental frequency three-phase voltage of the silicon carbide half-bridge module that makes the output current of the silicon carbide half-bridge module zero, and predict the magnitude of the output current ripple of the silicon-based half-bridge module; In order to compensate for the silicon-based current, calculate the coordinated compensation voltage of the silicon carbide half-bridge module and add it to the three-phase fundamental frequency voltage of the silicon carbide half-bridge module to obtain the new three-phase reference voltage of the silicon carbide half-bridge module; The reference voltage of the silicon-based half-bridge module and the new reference voltage of the silicon carbide half-bridge module are used as the modulation wave of the silicon-based half-bridge module and the modulation wave of the silicon carbide half-bridge module, respectively, and compared with the carrier wave to determine the switching state and switching time of each bridge arm of the three phases, and finally converted into 12 PWM signals.

[0036] The three-phase reference voltage v of the silicon carbide half-bridge module sic_m,x The calculation method for x = a, b, c is as follows. As shown in Equation 2, the fundamental frequency of the silicon carbide module's three-phase voltage v... sic_1,x x = a, b, c superimposed with a three-phase coordinated compensation voltage v used to compensate for the current ripple of the silicon-based half-bridge module. comp,x After x = a, b, c, the resulting v sic_m,x x = a, b, c serves as the three-phase reference voltage for the silicon carbide half-bridge module.

[0037] v sic_m,x =v sic_1,x +v comp,x x = a, b, c (2)

[0038] Three-phase fundamental frequency voltage of silicon carbide module v sic_1,x The decoupled calculation of x = a, b, c satisfies the following premise:

[0039] a: The voltage V between the neutral point of the second DC bus and the neutral point of the load ON The average voltage during one switching cycle of a silicon-based module is zero. Its expression is shown in Equation 3, where r is the first inductance L of the silicon-based module. 1x With the first inductor L of the silicon carbide module 2xThe ratio:

[0040]

[0041] Since the three-phase modulated waves of the aforementioned coordinated current-compensated SPWM control method are identical except for a 120-degree phase deviation, the switches on the three silicon-based modules (S...) 1x The sum of ) and the switches on the three silicon carbide modules (S) 3x The sum of these values ​​is 3 / 2 within one switching cycle of the silicon-based module. The voltage V between the neutral point of the second DC bus and the neutral point of the load is... ON The average voltage during a switching cycle of a silicon-based module is zero.

[0042] Three-phase fundamental frequency voltage of silicon carbide module v sic_1,x The expression for x = a, b, c is shown in Equation 4; the three-phase coordinated compensation voltage Δv comp,x The expression for x = a, b, c is shown in Equation 5; where ω is the fundamental angular frequency; v igbt_1,x x = a, b, c are given three-phase sinusoidal reference voltages for the silicon-based module; V 1,x The actual output voltage of the inverter is given by equation 6.

[0043]

[0044]

[0045]

[0046] In one specific embodiment, the given parameters are shown in Table 2:

[0047] Table 2 System parameters of a specific embodiment

[0048]

[0049] The simulation topology model in this embodiment was built using the Simulink / PLECS module in Matlab, and the digital control part was implemented using S-function tools and programmed in C language. It should be noted that this embodiment is not grid-connected; the load side is simulated using a load resistor. For ease of comparison, we also built a non-parallel converter model with identical parameters, consisting only of silicon-based half-bridge modules. Their single-phase load steady-state current waveforms are as follows: Figure 6 As shown in (a) and (b) of the figure, the waveforms show that compared to traditional silicon-based half-bridge modular converters, the load current ripple of the hybrid parallel converter is well suppressed, achieving high-frequency operation of the entire system while reducing overall power loss. Meanwhile, their steady-state current Fourier spectrum analysis is as follows: Figure 7As shown in (a) and (b) of the spectrum, it can be seen from the spectrum that the low-frequency harmonic components of the load current of the hybrid parallel converter are eliminated by the coordinated current compensation SPWM control method, which significantly improves the current quality. The modulation waveform of the silicon carbide half-bridge module is shown in Figure 1. Figure 8 As shown, the modulated wave consists of two parts: a 50Hz fundamental frequency component and a 1kHz compensation component for the silicon-based half-bridge module frequency. This verifies the coordinated current compensation SPWM control method described above and meets the requirements of this system design.

[0050] The above embodiments do not limit the invention in any way. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall still fall within the protection scope of the technical solution of the present invention.

Claims

1. A coordinated current compensation SPWM control method based on a three-phase modular parallel hybrid LCL filter converter topology, characterized in that, The three-phase modular parallel hybrid LCL filter converter topology includes a first DC power supply, a second DC power supply, a first phase circuit, a second phase circuit, and a third phase circuit with identical structures connected in parallel, and three AC-side loads or a three-phase power grid; the anode of the first DC power supply leads to the power terminal of the first DC bus; the cathode of the first DC power supply is connected to the anode of the second DC power supply and leads to the neutral point of the DC bus. The second DC power supply cathode leads to the second DC bus power terminal; Each phase circuit includes a silicon-based half-bridge module, a silicon carbide half-bridge module, a silicon-based module inductor, a silicon carbide module inductor, a filter capacitor, and an AC-side inductor. The collector of the upper arm of the silicon-based half-bridge module is connected to the first DC bus power terminal, and the emitter of the lower arm of the silicon-based half-bridge module is connected to the second DC bus power terminal. Similarly, the collector of the upper arm of the silicon carbide half-bridge module is connected to the first DC bus power terminal, and the emitter of the lower arm of the silicon carbide half-bridge module is connected to the second DC bus power terminal. The silicon-based module inductor... One side is connected to the common terminal of the upper and lower arms of the silicon-based half-bridge module; silicon carbide module inductor. One side is connected to the common terminal of the upper and lower bridge arms of the silicon carbide half-bridge module; silicon-based module inductor. On the other side, the silicon carbide module inductor The other side is connected to and leads out to the inverter-side output terminal; load-side inductor One side and filter capacitor One side is connected to the inverter output terminal; The three filter capacitors of the first phase circuit, the second phase circuit, and the third phase circuit The other side is interconnected; the three load-side inductors of the first phase circuit, the second phase circuit, and the third phase circuit. The other side is connected to three AC loads or three-phase power grids respectively, and the other side of the three AC loads or three-phase power grids is connected to the load neutral point (N) or the power grid neutral point (N). The coordinated current compensation SPWM control method includes: Starting from the given three-phase sinusoidal reference voltage of the silicon-based half-bridge module, the three-phase fundamental frequency voltage of the silicon carbide half-bridge module that makes the output current of the silicon carbide half-bridge module zero is calculated, and the magnitude of the output current ripple of the silicon-based half-bridge module is predicted. In order to compensate for the silicon-based current, the coordination compensation voltage of the silicon carbide half-bridge module is calculated and added to the three-phase fundamental frequency voltage of the silicon carbide half-bridge module to obtain the new three-phase reference voltage of the silicon carbide half-bridge module. The reference voltage of the silicon-based half-bridge module and the new reference voltage of the silicon carbide half-bridge module are used as the modulation wave of the silicon-based half-bridge module and the modulation wave of the silicon carbide half-bridge module, respectively. They are compared with the carrier wave to determine the switching state and switching time of each bridge arm of the three phases, and finally converted into 12 PWM signals. The three-phase reference voltage of the silicon carbide half-bridge module The calculation method is shown in equation (2), which is the three-phase fundamental frequency voltage of the silicon carbide half-bridge module. Superimposed with a three-phase coordinated compensation voltage to compensate for the current ripple of the silicon-based half-bridge module After that, what was obtained As the three-phase reference voltage for the silicon carbide module, （2）； The three-phase fundamental frequency voltage of the silicon carbide half-bridge module The expression is shown in equation (4); the three-phase coordinated compensation voltage The expression for is shown in equation (5); where, The fundamental angular frequency; Given a three-phase sinusoidal reference voltage for the silicon-based module; The actual output voltage of the inverter is given by equation (6). （4）； （5）； （6）； Where r is the silicon-based module inductance. With silicon carbide module inductor The ratio.

2. The coordinated current compensation SPWM control method based on a three-phase modular parallel hybrid LCL filter converter topology according to claim 1, characterized in that: The upper bridge arm switch of the silicon-based half-bridge module and lower bridge arm switch All are silicon-based insulated-gate bipolar transistors; the upper bridge arm switch of the silicon carbide half-bridge module. and bridge arm under switch All are silicon carbide-based metal oxide semiconductor field-effect transistors.

3. A coordinated current compensation SPWM control method based on a three-phase modular parallel hybrid LCL filter converter topology according to claim 1 or 2, characterized in that: The switching frequency of the silicon carbide half-bridge module is 10 to 30 times that of the silicon-based half-bridge module.

4. A coordinated current compensation SPWM control method based on a three-phase modular parallel hybrid LCL filter converter topology according to claim 1 or 2, characterized in that: Each phase of the converter has three output levels: N, O, and P. Four switching states are selected to define these three output levels: S1, S2, S3, and S4. 2_P S 2_N The switching functions and output levels corresponding to the four switching states, S3, are shown below: ， In the switching function, 1 represents the corresponding switch being turned on, and 0 represents the corresponding switch being turned off.

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