Bidirectional single-stage single-phase AC / DC converter modulation method based on SRDAB improved topology

Abstract

The invention discloses a bidirectional single-stage single-phase AC / DC converter modulation method based on an SRDAB improved topology, and the key parameters of the modulation method comprise the switching frequency of a converter, the resonant frequency of the SRDAB topology, the maximum normalized switching frequency, the minimum normalized switching frequency, the normalized switching frequency, and the phase shift angle between a DC side A bridge and a DC side B bridge. And a phase shift angle, a phase shift angle ratio and a virtual phase shift angle between the AC-side C bridge and the DC-side A bridge. Through a linearized relationship, each key parameter is associated so as to simplify the complexity of a modulation strategy. And meanwhile, the soft switching range is changed by adjusting the phase-shifting angle ratio. The phase-shifting angle ratio is increased, and the soft switching range is reduced; the phase-shifting angle ratio is reduced, and the soft switching range is enlarged. The modulation strategy of the converter of the type can be well simplified, the soft switching range is widened, and the efficiency of the converter of the type is further improved.

Description

Technical Field

[0001] This invention belongs to the field of AC / DC converter modulation technology, specifically relating to a bidirectional single-stage single-phase AC / DC converter modulation method based on an improved SRDAB topology. Background Technology

[0002] Currently, with the rapid development of new energy fields such as electric vehicles, residential photovoltaic power generation, and residential energy storage, higher requirements are being placed on AC / DC converters such as on-board chargers (OBCs), micro-PV inverters, and residential energy storage converters. However, current converters in these industries still employ a two-stage topology. The first stage typically uses an isolated DC / DC converter for electrical isolation; the second stage typically uses a non-isolated bidirectional DC / AC topology to convert DC to AC. This topology requires a large intermediate bus capacitor to absorb secondary power ripple. This leads to an increase in converter size and a decrease in converter efficiency. Although the intermediate bus capacitor can be reduced by improving control strategies, this results in excessive ripple current in the intermediate bus capacitor, increased capacitor heating, and a shortened capacitor lifespan.

[0003] With the rapid development of power electronics technology, single-stage topologies have become increasingly mature. These single-stage AC / DC converters are basically improvements on traditional isolated DC / DC converter topologies. Currently, the flyback topology is widely used, but it cannot achieve soft switching, and the inherent transformer leakage inductance reduces conversion efficiency. There are already many research results on DAB-based improved topologies, but DAB has a large turn-off current, leading to increased turn-off losses and reduced conversion efficiency. While SRDAB-based improved topologies can reduce turn-off current, their models and modulation strategies are complex. They typically use lookup tables to achieve optimal efficiency, but this results in large amounts of stored data, requiring additional off-chip FLASH memory in hardware design, increasing converter costs. Furthermore, different lookup tables need to be created for different project requirements. Lookup tables can be obtained through theoretical calculations or experimental measurements. Theoretically calculated lookup tables can be generated by computers, but there are discrepancies between the parameters of the theoretical model and the experimental model, resulting in certain errors. Since the modulation strategy is mostly on the boundary of constraints under light loads, it is quite sensitive to errors, easily affecting converter performance. Experimental measurements require measuring the optimal points under different operating conditions, but this requires significant hardware resources and a long research and development period. Summary of the Invention

[0004] To overcome the shortcomings of existing technologies, this invention provides a modulation method for a bidirectional single-stage single-phase AC / DC converter based on an improved SRDAB topology. Key parameters of this modulation method include the converter's switching frequency, the resonant frequency of the SRDAB topology, the maximum normalized switching frequency, the minimum normalized switching frequency, the normalized switching frequency, the phase shift angle between the DC-side A-bridge and B-bridge, the phase shift angle between the AC-side C-bridge and the DC-side A-bridge, the phase shift ratio, and the virtual phase shift angle. These key parameters are correlated through linearization to simplify the complexity of the modulation strategy. Simultaneously, the soft-switching range is changed by adjusting the phase shift ratio. Increasing the phase shift ratio decreases the soft-switching range; decreasing the phase shift ratio increases the soft-switching range. This invention effectively simplifies the modulation strategy of this type of converter, improves the soft-switching range, and further enhances the efficiency of this type of converter.

[0005] The technical solution adopted by this invention to solve its technical problem is as follows: Step 1: Construct AC / DC converter topology one, including switches S1, S2, S3, S4, S5a, S5b, S6a, S6b, S7a, S7b, S8a, S8b, and resonant inductor. resonant capacitor Transformer T; Switches S1 and S2 form the DC-side A bridge arm, switches S3 and S4 form the DC-side B bridge arm, switches S5a, S5b, S6a and S6b form the AC-side C bridge arm, and switches S7a, S7b, S8a and S8b form the DC-side D bridge arm. Step 2: Construct AC / DC converter topology two. Based on the AC / DC converter topology, two capacitors are used to replace the D-bridge arm, and the rest is completely the same. Step 3: Define the key parameters of the modulation method for the bidirectional single-stage single-phase AC / DC converter, including the converter's switching frequency. The resonant frequency of the SRDAB topology Maximum normalized switching frequency Minimum normalized switching frequency Normalized switching frequency Phase shift angle between DC-side A-arm and B-arm Phase shift angle between AC-side C-arm and DC-side A-arm Phase shift ratio Virtual phase shift angle Virtual phase shift angle ;in, Related to the range of soft switching, Increasing the value reduces the soft-switching range. Decrease the value, and increase the soft-switching range; Step 4: Determine the modulation strategy when the AC / DC converter is used as an inverter; Phase shift angle Provided by the controller; The phase angle of the C-arm on the AC side lags behind that of the A-arm on the DC side. ; The phase angle of the DC-side B bridge arm lags behind that of the DC-side A bridge arm. ; Phase shift angle Phase shift angle of times, that is ;when hour, ; Normalized switching frequency With phase angle They have an inverse linear relationship, that is... ; Switching frequency Resonant frequency of times, that is ; The resonant frequency is determined by the resonant capacitance in the topology. and resonant inductor Decision, that is ; Step 5: Determine the modulation strategy when the AC / DC converter is used as a rectifier; Virtual phase shift angle Provided by the controller; The phase angle of the C-arm on the AC side leads the phase angle of the A-arm on the DC side. ; The phase angle of the DC-side B bridge arm lags behind that of the DC-side A bridge arm. ; Phase shift angle Phase shift angle of times, that is ;when hour, ; Virtual phase shift angle and and Linear dependence, satisfying ; Phase shift angle and and Linear dependence, satisfying ; Normalized switching frequency With phase angle They have an inverse linear relationship, that is... ; Switching frequency Resonant frequency of times, that is ; The resonant frequency is determined by the resonant capacitance in the topology. and resonant inductor Decision, that is ; Step 6: Apply the two modulation strategies from Step 4 and Step 5 to AC / DC converter topology one and AC / DC converter topology two.

[0006] Preferably, the controller is a PI controller.

[0007] Preferably, the controller is a PR controller.

[0008] Preferably, the controller is an MPC controller.

[0009] An electronic device includes: a processor and a memory; the memory is used to store a computer program, and the processor is used to execute the computer program stored in the memory to enable the electronic device to perform the above-described bidirectional single-stage single-phase AC / DC converter modulation method.

[0010] A computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the above-described bidirectional single-stage single-phase AC / DC converter modulation method.

[0011] A chip includes a processor for retrieving and running a computer program from a memory, causing a device equipped with the chip to perform the above-described bidirectional single-stage single-phase AC / DC converter modulation method.

[0012] A computer program product includes a computer storage medium storing a computer program, the computer program including instructions executable by at least one processor, which, when executed by the at least one processor, implement the above-described bidirectional single-stage single-phase AC / DC converter modulation method.

[0013] The beneficial effects of this invention are as follows: This invention can provide a wide soft-switching range under a wide range of AC voltages, and avoid the dependence of the lookup table method on external FLASH; it can simplify the modulation and control strategies, and improve the efficiency of AC-DC converters. Attached Figure Description

[0014] Figure 1 It is a single-stage topology based on SRDAB improvement, with a bidirectional switching full-bridge on the AC side, which can realize bidirectional AC-DC conversion.

[0015] Figure 2It is a single-stage topology based on SRDAB improvement, with a bidirectional switching half-bridge on the AC side, which can realize bidirectional AC-DC conversion.

[0016] Figure 3 This is a schematic diagram showing the waveform relationship of the switching transistors when the AC voltage is greater than 0 in the inverter mode. Sxb represents the switching transistors S5b, S6b, S7b, and S8b.

[0017] Figure 4 This is a schematic diagram showing the waveform relationship of the switching transistors when the AC voltage is greater than 0 in the case of a rectifier. Sxb represents the switching transistors S5b, S6b, S7b, and S8b.

[0018] Figure 5 This is a schematic diagram of the waveform relationship of the switching transistors when the AC voltage is less than 0 in the case of an inverter. Sxa represents the switching transistors S5a, S6a, S7a and S8a.

[0019] Figure 6 This is a schematic diagram of the waveform relationship of the switching transistors when the AC voltage is less than 0 in the case of a rectifier. Sxa represents the switching transistors S5a, S6a, S7a and S8a.

[0020] Figure 7 This is the control block diagram for the inverter configuration.

[0021] Figure 8 This is the control block diagram for the rectifier case. Detailed Implementation

[0022] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0023] To address the shortcomings of existing technologies, this invention discloses a modulation method for a bidirectional single-stage single-phase AC / DC converter based on an improved SRDAB topology. This modulation method, applied to bidirectional single-stage single-phase AC / DC converters, simplifies the design of modulation and control strategies and eliminates the need for external FLASH memory in hardware implementation. It provides a wide soft-switching range over a broad range of AC voltages while avoiding reliance on external FLASH memory for lookup table methods; it simplifies both modulation and control strategies and improves the efficiency of the AC / DC converter.

[0024] To achieve the above objectives, the specific solution of the present invention is as follows: A key parameter in a modulation method for a bidirectional single-stage single-phase AC / DC converter based on an improved SRDAB topology is the converter's switching frequency. The resonant frequency of the SRDAB topology Maximum normalized switching frequency Minimum normalized switching frequency Normalized switching frequency Phase shift angle between DC-side bridge A and bridge B Phase shift angle between AC-side C-bridge and DC-side A-bridge Phase shift ratio Virtual phase shift angle Virtual phase shift angle .in, Related to the range of soft switching, Increasing the value reduces the soft-switching range. The soft-switching range is reduced as the number of switches decreases.

[0025] (1) When the AC-DC converter is used as an inverter, the phase shift angle Provided by the controller.

[0026] The phase angle of the C-arm on the AC side lags behind that of the A-arm on the DC side. .

[0027] The phase angle of the DC-side B bridge arm lags behind that of the DC-side A bridge arm. .

[0028] Phase shift angle Phase shift angle of times, that is ;when hour, .

[0029] Normalized switching frequency With phase angle They have an inverse linear relationship, that is... .

[0030] Switching frequency The resonant frequency of times, that is .

[0031] The resonant frequency is determined by the resonant capacitance in the topology. and resonant inductor Decision, that is .

[0032] (2) When the AC / DC converter is used as a rectifier, the virtual phase shift angle Provided by the controller.

[0033] The phase angle of the C-arm on the AC side leads the phase angle of the A-arm on the DC side. .

[0034] The phase angle of the DC-side B bridge arm lags behind that of the DC-side A bridge arm. .

[0035] Phase shift angle Phase shift angle of times, that is ;when hour, .

[0036] Virtual phase shift angle and and Linear dependence, satisfying .

[0037] Phase shift angle and and Linear dependence, satisfying .

[0038] Normalized switching frequency With phase angle They have an inverse linear relationship, that is... .

[0039] Switching frequency The resonant frequency of times, that is .

[0040] The resonant frequency is determined by the resonant capacitance in the topology. and resonant inductor Decision, that is .

[0041] Example: The modulation method of the present invention is used in a bidirectional single-stage single-phase AC / DC converter based on an improved SRDAB topology. Figure 1 and Figure 2 Both belong to two topologies of this converter. Figure 1 The AC side of the topology is a bidirectional switch full bridge. Figure 2 The AC side of the mid-topology is a bidirectional switch half-bridge.

[0042] for Figure 1 The AC / DC converter topology includes switching transistors S1, S2, S3, S4, S5a, S5b, S6a, S6b, S7a, S7b, S8a, and S8b, and a resonant inductor. resonant capacitor Transformer T. Switches S1 and S2 form the DC-side A-arm, switches S3 and S4 form the DC-side B-arm, switches S5a, S5b, S6a and S6b form the AC-side C-arm, and switches S7a, S7b, S8a and S8b form the DC-side D-arm.

[0043] With based Figure 1 Compared to AC / DC converters based on topology, Figure 2The AC / DC converter in this topology uses two capacitors instead of the D-bridge arm; the rest is identical. Both topologies are applicable to the modulation strategy of this invention. Because... Figure 2 The topology does not have a D-arm, so it can be ignored. Figure 3 , Figure 4 , Figure 5 , Figure 6 The waveforms of S7a, S7b, S8a, and S8b are applicable to all others. Figure 2 The topology in.

[0044] The key parameter of the modulation strategy in this invention is the switching frequency of the converter. The resonant frequency of the SRDAB topology Maximum normalized switching frequency Minimum normalized switching frequency Normalized switching frequency Phase shift angle between DC-side bridge A and bridge B Phase shift angle between AC-side C-bridge and DC-side A-bridge Phase shift ratio Virtual phase shift angle Virtual phase shift angle .

[0045] Inverter mode: For inverters, adopt Figure 7 The control structure in the middle will give the absolute value of the given AC voltage. The absolute value of the AC voltage obtained from actual sampling The difference is calculated, and then the phase shift angle is obtained through a PI controller. .

[0046] The phase angle of the C-arm on the AC side lags behind that of the A-arm on the DC side. .

[0047] The phase angle of the DC-side B bridge arm lags behind that of the DC-side A bridge arm. .

[0048] Phase shift angle Phase shift angle of times, that is ;when hour, .

[0049] Normalized switching frequency With phase angle They have an inverse linear relationship, that is... .

[0050] Switching frequency The resonant frequency of times, that is .

[0051] The resonant frequency is determined by the resonant capacitance in the topology. and resonant inductor Decision, that is .

[0052] Given AC voltage At that time, the waveform of its switching transistor is as follows Figure 3 As shown, , , , This indicates their respective complementary signals. S1 and S2 are complementary, S3 and S4 are complementary, S5a and S6a are complementary, and S7a and S8a are complementary, with each having a 50% duty cycle. The high and low levels each occupy a phase angle. S5b, S6b, S7b, and S8b are normally open. S3 lags behind S1 in phase angle. That is, the phase angle of the DC-side B bridge arm lags behind that of the DC-side A bridge arm. S5a lags behind S1 phase angle That is, the phase angle of the C-arm on the AC side lags behind that of the A-arm on the DC side. .

[0053] Given AC voltage At that time, the waveform of its switching transistor is as follows Figure 5 As shown, , , , This indicates their respective complementary signals. S1 and S2 are complementary, S3 and S4 are complementary, S5b and S6b are complementary, and S7b and S8b are complementary, with each having a 50% duty cycle. The high and low levels each occupy a phase angle. S5a, S6a, S7a, and S8a are normally open. S3 lags behind S1 by a phase angle. That is, the phase angle of the DC-side B bridge arm lags behind that of the DC-side A bridge arm. S6b lags behind S1 phase angle That is, the phase angle of the C-arm on the AC side lags behind that of the A-arm on the DC side. .

[0054] Rectifier mode: For rectifiers, adopt Figure 8 The control structure in the model calculates the difference between the given DC voltage and the sampled DC voltage, and then uses PI control to obtain the amplitude of the AC side current. AC side current amplitude The absolute value of the phase sine of the PPL output Multiplying them gives the absolute value of the given AC side current. . The virtual phase shift angle is obtained by subtracting the absolute value of the actual sampled AC current and then controlling it through a PI controller. .

[0055] The phase angle of the C-arm on the AC side leads the phase angle of the A-arm on the DC side. .

[0056] The phase angle of the DC-side B bridge arm lags behind that of the DC-side A bridge arm. .

[0057] Phase shift angle Phase shift angle of times, that is ;when hour, .

[0058] Virtual phase shift angle and and Linear dependence, satisfying .

[0059] Phase shift angle and and Linear dependence, satisfying .

[0060] Normalized switching frequency With phase angle They have an inverse linear relationship, that is... .

[0061] Switching frequency The resonant frequency of times, that is .

[0062] The resonant frequency is determined by the resonant capacitance in the topology. and resonant inductor Decision, that is .

[0063] AC voltage At that time, the waveform of its switching transistor is as follows: Figure 4 As shown, , , , This indicates their respective complementary signals. S1 and S2 are complementary, S3 and S4 are complementary, S5a and S6a are complementary, and S7a and S8a are complementary, with each having a 50% duty cycle. The high and low levels each occupy a phase angle. S5b, S6b, S7b, and S8b are normally open. S3 lags behind S1 in phase angle. That is, the phase angle of the DC-side B bridge arm lags behind that of the DC-side A bridge arm. S5a leads S1 phase angle. That is, the phase angle of the AC side C-arm leading the DC side A-arm. .

[0064] AC voltage At that time, the waveform of its switching transistor is as follows Figure 6 As shown, , , , This indicates their respective complementary signals. S1 and S2 are complementary, S3 and S4 are complementary, S5b and S6b are complementary, and S7b and S8b are complementary, with each having a 50% duty cycle. The high and low levels each occupy a phase angle. S5a, S6a, S7a, and S8a are normally open. S3 lags behind S1 by a phase angle. That is, the phase angle of the DC-side B bridge arm lags behind that of the DC-side A bridge arm. S6b leads S1 phase angle. That is, the phase angle of the C-arm on the AC side lags behind that of the A-arm on the DC side. .

[0065] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. The controller in the control block diagram may be a PR controller or an MPC controller, and the structure of the control block diagram may also be other structures. Those skilled in the art should understand that, based on the modulation strategy scheme of the present invention, various modifications or variations can be made without creative effort and are still within the scope of protection of the present invention.

Claims

1. A modulation method for a bidirectional single-stage single-phase AC-DC converter based on SR DAB improved topology, characterized in that, Includes the following steps: Step 1: Constructing AC-DC converter topology one, including switch tubes S1, S2, S3, S4, S5a, S5b, S6a, S6b, S7a, S7b, S8a, S8b, resonant inductor , resonant capacitor and transformer T; switch tubes S1 and S2 constitute DC side A bridge arm, switch tube S3 and switch tube S4 constitute DC side B bridge arm, switch tube S5a, S5b, S6a and S6b constitute AC side C bridge arm, switch tube S7a, S7b, S8a and S8b constitute DC side D bridge arm; Step 2: Construct AC / DC converter topology two. Based on the AC / DC converter topology, two capacitors are used to replace the D-bridge arm, and the rest is completely the same. Step 3: define the key parameters of the modulation method of the bidirectional single-stage single-phase AC-DC converter, including the switching frequency of the converter , the resonant frequency of the SRDAB topology , the maximum normalized switching frequency , the minimum normalized switching frequency , the normalized switching frequency , the phase shift angle between the A bridge arm and the B bridge arm on the DC side , the phase shift angle between the C bridge arm on the AC side and the A bridge arm on the DC side , the phase shift angle ratio , the virtual phase shift angle , the virtual phase shift angle ; wherein, is related to the range of soft switching, increases, the range of soft switching decreases; decreases, the range of soft switching increases; Step 4: Determine the modulation strategy when the AC / DC converter is used as an inverter; Phase shift angle Given by the controller; AC side C bridge arm phase lag DC side A bridge arm phase angle ; The DC side B bridge arm phase lags the DC side A bridge arm phase angle ; phase shift angle is the phase shift angle of times, i.e. ; when , ; Normalized switching frequency inversely related to the phase shift angle linearly, i.e. ; Switching frequency is the resonant frequency of i.e. ; The resonant frequency is determined by the resonant capacitance in the topology. and resonant inductor Decision, that is ; Step 5: Determine the modulation strategy when the AC / DC converter is used as a rectifier; Virtual phase shift angle Provided by the controller; The phase angle of the C-arm on the AC side leads the phase angle of the A-arm on the DC side. ; The phase angle of the DC-side B bridge arm lags behind that of the DC-side A bridge arm. ; Phase shift angle Phase shift angle of times, that is ;when hour, ; Virtual phase shift angle and and Linear dependence, satisfying ; Phase shift angle and and Linear dependence, satisfying ; Normalized switching frequency With phase angle They have an inverse linear relationship, that is... ; Switching frequency Resonant frequency of times, that is ; The resonant frequency is determined by the resonant capacitance in the topology. and resonant inductor Decision, that is ; Step 6: Apply the two modulation strategies from Step 4 and Step 5 to AC / DC converter topology one and AC / DC converter topology two.

2. The modulation method for a bidirectional single-stage single-phase AC / DC converter based on an improved SRDAB topology according to claim 1, characterized in that, The controller is a PI controller.

3. The modulation method for a bidirectional single-stage single-phase AC / DC converter based on an improved SRDAB topology according to claim 1, characterized in that, The controller is a PR controller.

4. The modulation method for a bidirectional single-stage single-phase AC / DC converter based on an improved SRDAB topology according to claim 1, characterized in that, The controller is an MPC controller.

5. An electronic device, characterized in that, include: Processor and memory; The memory is used to store a computer program, and the processor is used to execute the computer program stored in the memory to cause the electronic device to perform the method as described in any one of claims 1 to 4.

6. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the method as described in any one of claims 1 to 4.

7. A chip, characterized in that, include: A processor for retrieving and running a computer program from memory, causing a device on which the chip is mounted to perform the method as described in any one of claims 1 to 4.

8. A computer program product, characterized in that, The computer program product includes a computer storage medium storing a computer program, the computer program including instructions executable by at least one processor, which, when executed by the at least one processor, implement the method as described in any one of claims 1 to 4.

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