Control method and system of three-phase dual active bridge converter

Abstract

The application relates to the field of power electronics, in particular to a control method and system of a three-phase dual active bridge converter, which is used for controlling the conduction and cut-off of the primary side switch tube and the secondary side switch tube of the three-phase dual active bridge converter, realizing power transmission and making all the switch tubes meet zero voltage turn-on, comprising the following steps: collecting the input voltage and output voltage of the three-phase dual active bridge converter in real time, and calculating the reference current according to the transformer ratio in the three-phase dual active bridge converter n The calculated voltage ratio M , and the preset transmission power P and the input voltage; the application is based on the actual parasitic capacitance parameters of the MOSFET and the energy conservation condition, accurately calculates the current threshold required for realizing zero voltage turn-on, and uses the current threshold as the soft switch target current in each mode, so that the switch tube can reliably realize zero voltage turn-on in actual application, and the hard switch problem caused by incomplete charging and discharging of the parasitic capacitance is avoided.

Description

Technical Field

[0001] This invention relates to the field of power electronics, and in particular to a control method and a control system for a three-phase dual active bridge converter. Background Technology

[0002] The working principle of a dual active bridge (DAB) converter is to control the phase shift angle between the primary and secondary H-bridges, thereby regulating the current flowing through the transformer leakage inductance (or external series inductance) and thus controlling the magnitude and direction of transmitted power. Traditional control methods use single-phase shift (SPS) modulation, which involves fixing the switching frequency and controlling power solely by adjusting the phase shift ratio (i.e., the inner phase shift angle) between the primary and secondary bridge arms. Existing research mainly focuses on frequency conversion control strategies for single-phase DAB topologies, such as adjusting the switching frequency to keep the converter operating in a resonant state or adjusting the frequency according to load changes to maintain soft-switching conditions. Some solutions in the literature employ a combination of frequency conversion and phase shift control, using real-time calculations to ensure the switching current meets the zero-voltage switching (ZVS) condition. However, most of these solutions are based on quasi-ZVS criteria, meaning they only determine soft-switching potential based on the current direction at the moment the switch is turned off, without accurately considering the actual charging and discharging process of the MOSFET parasitic capacitance. This leads to discrepancies between the practical soft-switching effect and the theoretical performance. Summary of the Invention

[0003] To address the technical problem of discrepancies between the soft-switching effect and theoretical performance, this invention provides a control method and a control system for a three-phase dual active bridge converter. Firstly, a control method for a three-phase dual active bridge converter is provided, used to control the on / off state of the primary and secondary switches of the three-phase dual active bridge converter, to achieve power transmission and ensure that all switches meet zero-voltage turn-on, including: Real-time acquisition of input voltage of three-phase dual active bridge converter and output voltage And based on the transformer turns ratio in the three-phase dual active bridge converter n Calculate the voltage ratio M ,and ; According to the preset transmission power P and input voltage Calculate the reference current ; Obtain the equivalent junction capacitance of the switching transistor. C Equivalent leakage inductance of transformer LCalculate the minimum current required for soft switching. ,in, ; Select the voltage ratio M The control mode and shift ratio corresponding to the interval. and switching frequency f The calculation formula for the transmission power was used to verify the transmission power. P Whether the corresponding inequalities are satisfied to ensure that all the aforementioned switching transistors achieve zero-voltage turn-on; the voltage transformation ratio M The interval includes: 0≤ M <2 and M ≥2.

[0004] Preferably, when the voltage transformation ratio M In the state of 0≤ M When the value is ≤0.5, variable frequency single-phase shift control is used: ; .

[0005] Preferably, when the voltage transformation ratio M At 0.5 < M When the value is ≤0.521367, a fixed-frequency single-phase-shift control is used: the switching frequency is fixed at [value missing]. f =80000Hz, .

[0006] Preferably, when the voltage transformation ratio M At 0.521367 M When the value is less than 1, variable frequency single-phase shift control is used: ; .

[0007] Preferably, when the voltage transformation ratio M When =1, fixed-frequency single-phase-shift control is used: the switching frequency is fixed at... f =80000Hz, .

[0008] Preferably, when the voltage transformation ratio M In 1< M When the value is less than 1.84849, variable frequency single-phase shift control is used: ; .

[0009] Preferably, when the voltage transformation ratio MWhen the value is in the range of 1.84849 ≤ M < 2, a fixed-frequency single-phase-shift control is used: the switching frequency is fixed at [value missing]. f =80000Hz, .

[0010] Preferably, when the voltage transformation ratio M When M≥2, variable frequency single-phase shift control is used: ; .

[0011] Secondly, a control system for a three-phase dual active bridge converter is also provided, used to control the on / off state of the primary and secondary switches of the three-phase dual active bridge converter, to achieve power transmission and ensure that all switches meet zero-voltage turn-on requirements, including: Acquisition Unit: Used for real-time acquisition of the input voltage of the three-phase dual active bridge converter. and output voltage And based on the transformer turns ratio in the three-phase dual active bridge converter n Calculate the voltage ratio M ,and ; Calculation unit: used to calculate based on preset transmission power P and input voltage Calculate the reference current ; Acquisition unit: used to acquire the equivalent junction capacitance of the switching transistor. C Equivalent leakage inductance of transformer L Calculate the minimum current required for soft switching. ,in, ; Selection unit: used to select the voltage ratio. M The control mode and shift ratio corresponding to the interval. and switching frequency f The calculation formula for the transmission power was used to verify the transmission power. P Whether the corresponding inequalities are satisfied to ensure that all the aforementioned switching transistors achieve zero-voltage turn-on; the voltage transformation ratio M The interval includes: 0≤ M <2 and M ≥2.

[0012] Beneficial effects: 1. Unlike the traditional quasi-ZVS condition that relies solely on current direction for judgment, this application accurately calculates the current threshold required to achieve zero-voltage turn-on based on the actual parasitic capacitance parameters of MOSFETs or IGBTs and the energy conservation condition. This threshold is then used as the soft-switching target current in each mode, ensuring that the switching transistor can reliably achieve zero-voltage turn-on in practical applications and avoiding hard-switching problems caused by incomplete charging and discharging of parasitic capacitance. 2. Full-range actual soft-switching guarantee: Through a segmented hybrid control strategy, frequency conversion control is used when the voltage ratio is far from the critical point, and fixed-frequency SPS control is used near the critical point. Furthermore, the actual soft-switching current constraint is embedded into the power conditions in each mode to ensure that all switching transistors operate within the full voltage ratio range. M It can meet the actual zero-voltage turn-on condition based on parasitic capacitance from 0 to ∞ and across the entire load range, significantly reducing switching losses and improving converter efficiency; 3. Wide voltage adaptability: covering voltage range from M <0.5 to M With a wide voltage ratio range of ≥2, and through a smooth switching strategy at the critical point, the problem of single frequency converter control in... M The calculation fails near points 0.5, 1, 2, etc., and is applicable to situations where the input and output voltages vary over a wide range. 4. Efficiency Improvement: Within the transmission power range achievable by SPS modulation, increasing the frequency conversion control significantly improves efficiency; 5. Simple calculation and easy digital implementation: All formulas are explicit analytical expressions, requiring no iteration or table lookup, and can be easily calculated in real time in digital controllers (such as DSP and FPGA), with fast dynamic response; 6. Clear design guidance: Explicit inequalities for power conditions under each mode are provided. These inequalities have embedded actual soft-switching current constraints, providing a theoretical basis for converter parameter design (such as inductance, capacitance, and switching frequency) and ensuring that the soft-switching range matches the power level. Attached Figure Description

[0013] Figure 1 This is an embodiment diagram of a control method for a three-phase dual active bridge converter; Figure 2 ZVS first critical line curve diagram for a control method of a three-phase dual active bridge converter; Figure 3 ZVS second critical line curve diagram for a control method of a three-phase dual active bridge converter; Figure 4 The following is an example diagram of a control system for a three-phase dual active bridge converter; Figure 5 This is a schematic diagram of an embodiment of a three-phase dual active bridge converter.

[0014] Explanation of reference numerals in the attached figures: 1. A control system for a three-phase dual active bridge converter; 11. Acquisition unit; 12. Calculation unit; 13. Acquisition unit; 14. Selection unit. Detailed Implementation

[0015] Terminology Explanation: Three-phase dual active bridge (DAB) converters are a typical isolated bidirectional DC-DC converter topology. Due to their advantages such as electrical isolation, bidirectional energy flow, high power density, and ease of soft switching, they are widely used in electric vehicle charging and discharging systems, energy storage systems, solid-state transformers, and distributed generation grid-connection interfaces. Compared to single-phase DAB converters, three-phase DAB converters offer higher power density, smaller filter size, and lower current ripple, making them suitable for medium to high power applications.

[0016] ZVS: Zero Voltage Switching; is a soft-switching technology in the field of power electronics. Its core is to enable power switching devices (such as MOSFETs and IGBTs) to complete the turn-on operation when the voltage across them is zero or close to zero, thereby eliminating turn-on losses, improving efficiency and reducing EMI interference.

[0017] Transmission power: is the active power transmitted from the input side to the output side.

[0018] To address the technical problem of discrepancies between the soft-switching effect and theoretical performance, this invention provides a control method and a control system for a three-phase dual active bridge converter. Firstly, such as Figure 1 As shown, a control method for a three-phase dual active bridge converter is provided, used to control the on / off state of the primary and secondary switches of the three-phase dual active bridge converter, to achieve power transfer and ensure that all switches meet zero-voltage turn-on, including: S1: Real-time acquisition of the input voltage of the three-phase dual active bridge converter and output voltage And based on the transformer turns ratio in the three-phase dual active bridge converter n Calculate the voltage ratio M ,and M is a scale used to measure whether the voltages on both sides of a three-phase dual active bridge converter are matched. M When =1, the voltage is perfectly matched. At this time, the current stress and return power in the circuit are minimized, the efficiency is maximized, and all switching transistors can achieve ZVS.

[0019] S2: Based on the preset transmission power P and input voltage Calculate the reference current ; It is an intermediate variable, the power control reference current, which represents the expected value of the average DC current on the input side of the three-phase dual active bridge converter. It determines the magnitude and direction of the power.

[0020] S3: Obtain the equivalent junction capacitance of the switching transistor. C Equivalent leakage inductance of transformer L Calculate the minimum current required for soft switching. ,in, ; S4: Select the voltage ratio. M The control mode and shift ratio corresponding to the interval. and switching frequency f The calculation formula for the transmission power was used to verify the transmission power. P Whether the corresponding inequalities are satisfied to ensure that all the aforementioned switching transistors achieve zero-voltage turn-on; the voltage transformation ratio M The interval includes: 0≤ M ≤0.5, 0.5< M ≤0.521367, 0.521367< M <1、 M =1、1< M <1.84849、1.84849≤ M <2 and M ≥2. The switching transistors in this technical solution include: MOSFET and IGBT. The equivalent junction capacitance of the switching transistor is... C This information can be obtained from the switch datasheet or through measurement. The traditional control method is single-phase shift (SPS) modulation, which involves fixing the switching frequency and adjusting the phase shift between the primary and secondary bridge arms. Power is controlled by adjusting the phase shift angle (i.e., the internal phase shift angle). Single-phase modulation control is simple and easy to implement, but its soft-switching range is significantly affected by the voltage turns ratio. Power requirements and the minimum current required for soft switching are met by simultaneously adjusting the phase shift angle and frequency. The requirements. Compared to... The primary side three-phase high-frequency square wave serves as the phase reference; the secondary side three-phase square wave, as a whole, lags / leads the primary side by a uniform phase shift angle. φ Both the primary and secondary bridges of the three phases are fixed at 50% duty cycle; the duty cycle is not adjusted, only the following changes are made. φ The size changes the transmission power. A common setting for three-phase dual active bridges is 0 ≤ φ ≤2π, above 90 degrees Celsius, power actually decreases, and circulating current increases dramatically, resulting in greater losses; therefore, this method is not used in engineering. For example... Figure 5The diagram shown is an embodiment of a three-phase dual active bridge converter.

[0021] Preferred, such as Figure 2 As shown, Mode 0: When the voltage transformation ratio M In the state of 0≤ M When the value is ≤0.5, variable frequency single-phase shift control is used: where, ; ; The phase shift angle must satisfy: .

[0022] Preferred, such as Figure 2 As shown, Mode 1: When the voltage transformation ratio M At 0.5 < M When the value is ≤0.521367, a fixed-frequency single-phase-shift control is used: the switching frequency is fixed at [value missing]. f =80000Hz, where, ; Power requirements: .

[0023] Preferred, such as Figure 2 As shown, Mode 2: When the voltage ratio M At 0.521367 M When the value is less than 1, variable frequency single-phase shift control is used: where, ; ; The phase shift angle must satisfy: .

[0024] Preferred, such as Figure 2 As shown, Mode 3: When the voltage ratio M When =1, fixed-frequency single-phase-shift control is used: the switching frequency is fixed at... f =80000Hz, where, ; Power requirements: .

[0025] Preferred, such as Figure 2 As shown, Mode 4: When the voltage ratio M In 1< M When the value is less than 1.84849, variable frequency single-phase shift control is used: where, ; ; The phase shift angle must satisfy: .

[0026] Preferred, such as Figure 2 As shown, Mode 5: When the voltage ratio M At 1.84849≤ M When the frequency is less than 2, a fixed-frequency single-phase-shift control is used: the switching frequency is fixed at [frequency value]. f =80000Hz, where, ; Power requirements: .

[0027] Preferred, such as Figure 2 As shown, Mode 6: When the voltage ratio M In M When ≥2, variable frequency single-phase shift control is adopted: where, ; ; The phase shift angle must satisfy: .

[0028] like Figure 2 As shown, in the variable frequency control mode, the switching frequency is adjusted in real time according to the load and voltage changes, while in the fixed frequency control mode, the switching frequency is fixed at a preset value (such as 80000Hz). The two modes are smoothly switched at the critical voltage ratio point to ensure that the system operates stably within the full voltage ratio range.

[0029] Unlike traditional quasi-ZVS methods that only determine current direction, the technical solution in this application is based on the actual parasitic capacitance parameters of the MOSFET or IGBT, and utilizes the energy conservation condition. Let's analyze this (where V represents the voltage applied across the parasitic capacitance of the MOSFET or IGBT at this point). Considering only SPS modulation, since only one MOSFET or IGBT on each bridge arm switches during each switching state, and the voltage of the MOSFET or IGBT to be turned on at the turn-off moment is V, the charge on the parasitic capacitance of the MOSFET or IGBT needs to be transferred through an inductor to achieve soft turn-on. The voltage of one MOSFET or IGBT decreases from V to 0, while the voltage of the other MOSFET or IGBT increases from 0 to V. Therefore, the energy stored in the inductor needs to be greater than or equal to the energy required by the two parasitic capacitances, as shown by the formula... have to ; have to ,Pick .

[0030] When using input voltage or output voltage At that time, or .

[0031] According to voltage ratio Different intervals (0≤ M ≤0.5, 0.521< M <1、1< M <1.848, M≥2), using different soft-switching target currents as control targets, the shift ratio is derived. and switching frequency f The explicit analytical formula achieves full-range coverage. When the voltage ratio approaches the critical point (0.5 < 0.5), the formula is applied. M ≤0.521、 M =1, 1.848≤ M <2) When the frequency converter control calculation fails or the shift ratio exceeds the effective range, switch to fixed-frequency SPS control, and provide the analytical expression for the shift ratio and the actual soft-switching power constraint conditions in this mode to achieve seamless connection between the two control modes. For each control mode, a lower (or upper) power inequality to ensure the actual soft switching is established is given. These inequalities have taken into account the equivalent junction capacitance. C Leakage L Switching frequency f and voltage ratio M This is taken into consideration, providing a quantitative basis for converter parameter design and operating condition boundary determination. The expression for the critical voltage ratio for switching between frequency conversion and fixed-frequency modes is determined through theoretical calculations: ; This provides a clear mathematical basis for switching control strategies, avoiding trial and error in engineering.

[0032] like Figure 3 As shown, the yellow area represents the increased soft-switching range compared to SPS modulation.

[0033] Secondly, such as Figure 4 As shown, a control system 1 for a three-phase dual active bridge converter is also provided, used to control the on / off state of the primary and secondary switches of the three-phase dual active bridge converter, to achieve power transmission and ensure that all switches meet zero-voltage turn-on, including: Acquisition Unit 11: Used for real-time acquisition of the input voltage of the three-phase dual active bridge converter. and output voltage And based on the transformer turns ratio in the three-phase dual active bridge converter n Calculate the voltage ratio M ,and ; Calculation unit 12: used to calculate based on preset transmission power P and input voltage Calculate the reference current ; Acquisition unit 13: Used to acquire the equivalent junction capacitance of the switching transistor. C Equivalent leakage inductance of transformer L Calculate the minimum current required for soft switching. ,in,

[0034] Selection unit 14: Used to select the voltage ratio. M The control mode and shift ratio corresponding to the interval. and switching frequency f The calculation formula for the transmission power was used to verify the transmission power. P Whether the corresponding inequalities are satisfied to ensure that all the aforementioned switching transistors achieve zero-voltage turn-on; the voltage transformation ratio M The interval includes: 0≤ M ≤0.5, 0.5< M ≤0.521367, 0.521367< M <1、 M =1、1< M <1.84849、 1.84849≤ M <2 and M ≥2.

[0035] Beneficial effects: 1. Unlike the traditional quasi-ZVS condition that relies solely on current direction for judgment, this application accurately calculates the current threshold required to achieve zero-voltage turn-on based on the actual parasitic capacitance parameters of the MOSFET and the energy conservation condition, and uses this as the soft-switching target current in each mode to ensure that the switching transistor can reliably achieve zero-voltage turn-on in practical applications, avoiding hard-switching problems caused by incomplete charging and discharging of parasitic capacitance. 2. Full-range actual soft-switching guarantee: Through a segmented hybrid control strategy, frequency conversion control is used when the voltage ratio is far from the critical point, and fixed-frequency SPS control is used near the critical point. Furthermore, the actual soft-switching current constraint is embedded into the power conditions in each mode to ensure that all switching transistors operate within the full voltage ratio range. M It can meet the actual zero-voltage turn-on condition based on parasitic capacitance from 0 to ∞ and across the entire load range, significantly reducing switching losses and improving converter efficiency; 3. Wide voltage adaptability: covering voltage range from M <0.5 to M With a wide voltage ratio range of ≥2, and through a smooth switching strategy at the critical point, the problem of single frequency converter control in... MThe calculation fails near points 0.5, 1, 2, etc., and is applicable to situations where the input and output voltages vary over a wide range. 4. Efficiency Improvement: Within the transmission power range achievable by SPS modulation, increasing the frequency conversion control significantly improves efficiency; 5. Simple calculation and easy digital implementation: All formulas are explicit analytical expressions, requiring no iteration or table lookup, and can be easily calculated in real time in digital controllers (such as DSP and FPGA), with fast dynamic response; 6. Clear design guidance: Explicit inequalities for power conditions under each mode are provided. These inequalities have embedded actual soft-switching current constraints, providing a theoretical basis for converter parameter design (such as inductance, capacitance, and switching frequency) and ensuring that the soft-switching range matches the power level.

[0036] Finally, it should be noted that any modification or equivalent substitution of some or all of the technical features based on the device structure and the technical solutions of the embodiments of the present invention, without departing from the corresponding technical solutions of the present invention, shall fall within the patent scope of the device structure and the embodiments of the present invention.

Claims

1. A control method for a three-phase dual active bridge converter, used to control the on / off state of the primary and secondary switching transistors of the three-phase dual active bridge converter, to achieve power transmission and ensure that all said switching transistors meet zero-voltage turn-on, characterized in that, comprising: Real-time acquisition of input voltage of three-phase dual active bridge converter and output voltage And calculate the voltage ratio M based on the transformer turns ratio n in the three-phase dual active bridge converter, and ; According to the preset transmission power and input voltage Calculate the reference current ; Obtain the equivalent junction capacitance of the switching transistor. Equivalent leakage inductance of transformer Calculate the minimum current required for soft switching. ;in, ; select the control mode, phase-shift ratio corresponding to the interval where the voltage conversion ratio M is located and switching frequency calculation formulas, and verify whether the transmission power satisfies the corresponding inequality, so as to ensure that all the switching tubes meet the zero-voltage turn-on condition; the control modes include: when the voltage conversion ratio M is in the interval of 0≤M≤0.5, 0.521367<M<1, 1<M<1.84849, and M≥2, variable-frequency single-phase-shift control is adopted; when M is in the interval of 0.5<M≤0.521367, M=1, and 1.84849≤M<2, fixed-frequency single-phase-shift control is adopted; From the reference current Voltage ratio M and minimum current Calculate the shift ratio ; Compared to the shift Output voltage Equivalent leakage inductance and reference current Calculate the switching frequency during the variable frequency single-phase shift control. .

2. The control method for a three-phase dual active bridge converter according to claim 1, characterized in that, when the voltage conversion ratio M is in the interval of 0≤M≤0.5, variable-frequency single-phase-shift control is adopted: 。 3. The control method for a three-phase dual active bridge converter according to claim 1, characterized in that, when the voltage conversion ratio M is in the interval of 0.5<M≤0.521367, fixed-frequency single-phase-shift control is adopted: the switching frequency is fixed at f=80000Hz, 。 4. The control method for a three-phase dual active bridge converter according to claim 1, characterized in that, when the voltage conversion ratio M is in the interval of 0.521367<M<1, variable-frequency single-phase-shift control is adopted: 。 5. The control method for a three-phase dual active bridge converter according to claim 1, characterized in that, when the voltage conversion ratio M=1, fixed-frequency single-phase-shift control is adopted: the switching frequency is fixed at f=80000Hz, 。 6. The control method for a three-phase dual active bridge converter according to claim 1, characterized in that, when the voltage conversion ratio M is in the interval of 1<M<1.84849, variable-frequency single-phase-shift control is adopted: 。 7. The control method for a three-phase dual active bridge converter according to claim 1, characterized in that, when the voltage conversion ratio M is in the interval of 1.84849≤M<2, fixed-frequency single-phase-shift control is adopted: the switching frequency is fixed at f=80000Hz, 。 8. The control method for a three-phase dual active bridge converter according to claim 1, characterized in that, when the voltage conversion ratio M is in the interval of M≥2, variable-frequency single-phase-shift control is adopted: ； 。 9. A control system for a three-phase dual active bridge converter, used to control the on / off state of the primary and secondary switches of the three-phase dual active bridge converter, to achieve power transmission and ensure that all said switches meet zero-voltage turn-on, characterized in that, comprising: Acquisition Unit: Used for real-time acquisition of the input voltage of the three-phase dual active bridge converter. and output voltage And based on the transformer turns ratio in the three-phase dual active bridge converter Calculate the voltage transformation ratio M, and ; Calculation unit: used to calculate based on preset transmission power and input voltage Calculate the reference current ; Acquisition unit: used to acquire the equivalent junction capacitance of the switching transistor. Equivalent leakage inductance of transformer Calculate the minimum current required for soft switching. ;in, ; selection unit, configured to select the control mode, phase shift ratio corresponding to the interval where the voltage conversion ratio M is located and switching frequency calculation formulas, and verify whether the transmission power satisfies the corresponding inequality, so as to ensure that all the switching tubes satisfy zero-voltage turn-on; the control mode includes: when the voltage conversion ratio M is in the interval of 0≤M≤0.5, 0.521367<M<1, 1<M<1.84849, and M≥2, variable-frequency single-phase-shift control is adopted; when M is in the interval of 0.5<M≤0.521367, M=1, and 1.84849≤M<2, fixed-frequency single-phase-shift control is adopted; From the reference current Voltage ratio M and minimum current Calculate the shift ratio ; Compared to the shift Output voltage Equivalent leakage inductance and reference current Calculate the switching frequency during the variable frequency single-phase shift control. .

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