Three-phase asymmetric hybrid dual-active bridge converter and soft switching modulation method thereof

Abstract

The invention discloses a three-phase asymmetric hybrid dual-active bridge converter and a soft switching modulation method thereof. The three-phase asymmetric hybrid dual-active bridge converter comprises a three-phase full-controlled bridge circuit input port, a three-phase hybrid bridge circuit output port and an intermediate-frequency three-phase transformer between the input port and the output port, based on a low-cost three-phase hybrid bridge circuit and a three-phase full-control bridge circuit, low-cost asymmetric bidirectional power transmission of the converter is realized. Based on the proposed converter topology and modulation strategy, converter topology reconstruction and decoupling under the forward power transmission working condition and the reverse power transmission working condition are realized, the control architecture of the converter is simplified, and the complexity of the control system is reduced. By replacing expensive power switches with inexpensive diodes, the invention has significant cost advantages in asymmetric power transfer scenarios.

Description

Technical Field

[0001] This invention belongs to the field of DC power distribution system converters, specifically relating to a three-phase asymmetric hybrid dual active bridge converter and its soft-switching modulation method. Background Technology

[0002] In recent years, with the increasing penetration rate of new energy sources and the widespread application of distributed power systems, traditional AC systems have faced numerous limitations in handling distributed power source access and DC load supply, such as low conversion efficiency and poor power quality. DC distribution systems, due to their high efficiency, ease of control, and natural access to renewable energy, are expected to replace traditional AC systems and become a more promising technological solution.

[0003] In DC power distribution systems that integrate renewable energy sources such as photovoltaics and wind power, the intermittent and fluctuating nature of these sources often leads to asymmetrical power flow. Specifically, the system's demand for reverse power transmission is far less than its demand for forward power transmission, and reverse power transmission occurs only a small proportion of the system's lifespan. Traditional bidirectional DC-DC converters have equal forward and reverse power transmission capabilities, resulting in reverse capacity redundancy and unnecessary construction costs.

[0004] Therefore, while ensuring forward power transmission capacity, the redundancy of reverse power transmission capacity can be reduced by replacing some fully controlled devices with uncontrolled devices, thereby reducing system cost. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a three-phase asymmetric hybrid dual active bridge converter and its soft-switching modulation method, which solves the problems of reverse capacity redundancy and high construction cost of traditional converters in the prior art.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0007] A three-phase asymmetrical hybrid dual active bridge converter includes a three-phase fully controlled bridge circuit input port, a three-phase hybrid bridge circuit output port, and an intermediate frequency three-phase transformer between the input and output ports. The three-phase fully controlled bridge circuit includes three fully controlled power switch arms; the three-phase hybrid bridge circuit includes one fully controlled power switch arm and two uncontrolled diode arms; the intermediate frequency three-phase transformer is of type Dyn, with three taps on both the primary and secondary sides, and a primary-to-secondary turns ratio of [value missing]. The grounding wire of the three-phase transformer is connected to the midpoint of the DC stabilizing capacitor. The leakage inductance of the transformer is... .

[0008] DC voltage at the input port DC voltage at the output port The relationship between them satisfies the following formula:

[0009]

[0010] in, This represents the DC voltage conversion ratio.

[0011] The range satisfies:

[0012] .

[0013] The soft-switching modulation method for a three-phase asymmetric hybrid dual active bridge converter includes control of forward power transfer mode and reverse power transfer mode. In the forward power transfer mode, duty cycle control is used, and the converter transfers power from the input port to the output port. The specific process is as follows:

[0014] The fully controlled power switch bridge arm of the three-phase hybrid bridge circuit is in a locked state, and the switching cycle of the converter is set to... The phase difference of the drive pulses of each arm of the three-phase fully controlled bridge circuit The drive pulses of the upper and lower bridge arm power switches of each bridge arm are complementary, and the drive pulse width of the upper bridge arm power switch is... , Duty cycle;

[0015] In reverse power transfer mode, extended phase-shift control is used. The converter transfers power from the output port to the input port. The specific control process is as follows:

[0016] The C-phase fully controlled power switch arm of the three-phase fully controlled bridge circuit is in a locked state, which in turn causes the uncontrolled diode arm of the three-phase hybrid bridge circuit to be in a combined locked state; the half-switching period of the converter is set to... The duty cycle of the fully controlled bridge arm power switches in three-phase fully controlled bridge circuits and three-phase hybrid bridge circuits. The phase difference between the drive pulse of the upper bridge arm switch in phase A and the drive pulse of the lower bridge arm switch in the three-phase fully controlled bridge circuit is 0.5. The phase difference between the A-phase upper arm switch drive pulse and the A-phase upper arm switch drive pulse of the three-phase hybrid bridge circuit is... ,in, Compared to inward movement, Compared to moving outwards.

[0017] In forward power transfer mode, the converter's power transfer relationship satisfies:

[0018] When DC voltage conversion ratio Satisfy 1 / 2 < When <2 / 3, the transmission power relationship satisfies:

[0019] ;

[0020] When DC voltage conversion ratio Satisfy 2 / 3 < When <1, the transmission power relationship satisfies:

[0021] ;

[0022] when In reverse power transfer mode, the anode voltage of the diode in the uncontrolled diode bridge arm of the three-phase hybrid bridge circuit is always less than the cathode voltage, and the diode is in the off state.

[0023] In reverse power transfer mode, the converter's power transfer relationship satisfies:

[0024] .

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. Based on a low-cost three-phase hybrid bridge circuit and a three-phase fully controlled bridge circuit, a low-cost asymmetric bidirectional power transmission of the converter is realized.

[0027] 2. Based on the proposed converter topology and modulation strategy, converter topology reconstruction and decoupling under forward power transmission and reverse power transmission conditions were realized, simplifying the converter control architecture and reducing the complexity of the control system.

[0028] 3. The circuit topology of this solution has a significant cost advantage in asymmetric bidirectional power transmission scenarios by using inexpensive diodes instead of expensive power switches (MOSFETs or IGBTs). Attached Figure Description

[0029] Figure 1 This is a topology diagram of the three-phase asymmetric hybrid dual active bridge converter of the present invention.

[0030] Figure 2 This is a schematic diagram of the operation of the three-phase asymmetric hybrid dual active bridge converter under forward operating conditions according to the present invention.

[0031] Figure 3 This is a schematic diagram of the working waveform of the three-phase asymmetric hybrid dual active bridge converter under forward operating conditions according to the present invention.

[0032] Figure 4 This is a schematic diagram of the node voltage of the three-phase asymmetric hybrid dual active bridge converter under reverse operating conditions according to the present invention.

[0033] Figure 5 This is a schematic diagram of the operation of the three-phase asymmetric hybrid dual active bridge converter under reverse operating conditions according to the present invention.

[0034] Figure 6 This is a schematic diagram of the working waveform of the three-phase asymmetric hybrid dual active bridge converter under reverse operating conditions according to the present invention.

[0035] Figure 7 The figure shows the simulation results of current and voltage under the forward operating condition of the three-phase asymmetric hybrid dual active bridge converter of the present invention.

[0036] Figure 8 The simulation results of current and voltage under reverse operation of the three-phase asymmetric hybrid dual active bridge converter of the present invention are shown. Detailed Implementation

[0037] The structure and working process of the present invention will be further described below with reference to the accompanying drawings.

[0038] The purpose of this invention is to innovatively propose a new isolated converter topology with low-cost asymmetric bidirectional power transmission capability to address the asymmetric bidirectional power transmission requirements in new energy scenarios. This scheme features an asymmetric three-phase bridge circuit structure. By replacing some fully controlled components of the three-phase bridge circuit at the output port with diodes, asymmetric forward and reverse power transmission capacity is achieved. Furthermore, by adjusting the switching modulation strategy for forward and reverse operation, decoupled operation between the forward and reverse modes is realized. Compared with existing technologies, this invention has the following characteristics:

[0039] It features a low-cost three-phase hybrid bridge circuit and a three-phase fully controlled bridge circuit, enabling asymmetrical bidirectional power transfer between the input and output ports.

[0040] It has a medium-frequency three-phase transformer, which can realize electrical isolation between the input port and the output port and interconnection of DC systems of different voltage levels;

[0041] A topology-reconfiguration-based control strategy is adopted to achieve decoupled operation between forward and reverse operating conditions.

[0042] A three-phase asymmetrical hybrid dual active bridge converter includes a three-phase fully controlled bridge circuit input port, a three-phase hybrid bridge circuit output port, and an intermediate frequency three-phase transformer between the input and output ports. The three-phase fully controlled bridge circuit includes three fully controlled power switch arms; the three-phase hybrid bridge circuit includes one fully controlled power switch arm and two uncontrolled diode arms; the intermediate frequency three-phase transformer is of type Dyn, with three taps on both the primary and secondary sides, and a primary-to-secondary turns ratio of [value missing]. The grounding wire of the three-phase transformer is connected to the midpoint of the DC stabilizing capacitor. The leakage inductance of the transformer is... .

[0043] The soft-switching modulation method for a three-phase asymmetric hybrid dual active bridge converter includes control of forward power transfer mode and reverse power transfer mode. In the forward power transfer mode, duty cycle control is used, and the converter transfers power from the input port to the output port. The specific process is as follows:

[0044] The fully controlled power switch bridge arm of the three-phase hybrid bridge circuit is in a locked state, and the switching cycle of the converter is set to... The phase difference of the drive pulses of each arm of the three-phase fully controlled bridge circuit The drive pulses of the upper and lower bridge arm power switches of each bridge arm are complementary, and the drive pulse width of the upper bridge arm power switch is... , Duty cycle;

[0045] In reverse power transfer mode, extended phase-shift control is used. The converter transfers power from the output port to the input port. The specific control process is as follows:

[0046] The C-phase fully controlled power switch arm of the three-phase fully controlled bridge circuit is in a locked state, which in turn causes the uncontrolled diode arm of the three-phase hybrid bridge circuit to be in a combined locked state; the half-switching period of the converter is set to... The duty cycle of the fully controlled bridge arm power switches in three-phase fully controlled bridge circuits and three-phase hybrid bridge circuits. The phase difference between the drive pulse of the upper bridge arm switch in phase A and the drive pulse of the lower bridge arm switch in the three-phase fully controlled bridge circuit is 0.5. The phase difference between the A-phase upper arm switch drive pulse and the A-phase upper arm switch drive pulse of the three-phase hybrid bridge circuit is... ,in, Compared to inward movement, Compared to moving outwards.

[0047] Specific embodiments, such as Figures 1 to 8 As shown:

[0048] A three-phase asymmetrical hybrid dual active bridge converter includes a three-phase fully controlled bridge circuit input port, a three-phase hybrid bridge circuit output port, and a medium-frequency three-phase transformer between the input and output ports; wherein the three-phase fully controlled bridge circuit includes six fully controlled power switches. The three-phase hybrid bridge circuit includes a fully controlled power switch bridge arm ( ) and two low-cost uncontrolled diode bridge arms ( The intermediate frequency three-phase transformer is of type Dyn, with three taps on both the primary and secondary sides, and a primary-to-secondary turns ratio of [value missing]. The grounding wire of the three-phase transformer is connected to the midpoint of the DC stabilizing capacitor. The leakage inductance of the three-phase transformer is... .

[0049] This converter is a buck converter topology. Specifically, when the input port DC voltage is set to... The DC voltage at the output port is The relationship between the two satisfies:

[0050]

[0051] Furthermore, control the DC voltage conversion ratio The range satisfies:

[0052]

[0053] The topology proposed in this embodiment can achieve bidirectional asymmetric power transfer between the input and output ports at low cost, and realizes converter topology reconfiguration and decoupling under forward and reverse operating conditions, simplifying the converter control architecture. Its specific working principle is as follows. To simplify the calculation process of its power characteristics, it is assumed that the voltage of each port is approximately constant.

[0054] The following analysis examines the operation mode and power characteristics of the three-phase asymmetric hybrid dual active bridge converter under two modes: forward power transfer mode and reverse power transfer mode.

[0055] A. Forward power transfer mode operation and power characteristics

[0056] In forward power transfer mode, the converter transfers power from the input port to the output port. In this mode, the converter latches the power switch. and The converter's operating diagram at this time is as follows: Figure 2 As shown.

[0057] Under forward operating conditions, the converter employs duty cycle control, specifically: the converter's switching cycle is... The drive pulses of the A, B, and C phase arms of the three-phase fully controlled bridge circuit are sequentially phase-differentiated. The drive pulses of the upper and lower bridge arm power switches of each bridge arm are complementary, and the drive pulse widths of power switches S1, S3, and S5 are all... The converter drive pulse waveform, the primary line voltage of the three-phase transformer, and the secondary phase voltage waveform are as follows: Figure 3 As shown.

[0058] Based on the operating waveform of the three-phase asymmetric hybrid dual active bridge converter under forward operating conditions, the power transfer characteristics under forward operating conditions can be derived as shown below.

[0059] When DC voltage conversion ratio Satisfy 1 / 2 < When <2 / 3, the transmission power relationship satisfies:

[0060]

[0061] When DC voltage conversion ratio Satisfy 2 / 3 < When <1, the transmission power relationship satisfies:

[0062]

[0063] B. Reverse power transfer mode operation and power characteristics

[0064] In reverse power transfer mode, the converter transfers power from the output port to the input port. In this mode, the converter latches the power switch. and Due to the control of DC voltage conversion ratio Within the range, when the converter operates in reverse power transfer mode, the fully controlled C-phase bridge arm power switch of the blocked three-phase fully controlled bridge circuit will jointly block the uncontrolled B and C-phase diode bridge arms of the three-phase hybrid bridge arm. A typical converter node voltage diagram under reverse operation is shown below. Figure 4 As shown, when 0.5 < When the voltage is less than 1, the diode cannot conduct because the anode voltage is always less than the cathode voltage. The converter's operating diagram at this time is as follows: Figure 5 As shown.

[0065] Under reverse operating conditions, the converter employs extended phase-shift control, specifically: the converter's half-switching period is... The drive pulses of power switch S1 and power switch S4 in the three-phase fully controlled bridge circuit are out of phase. The drive pulse of power switch S1 is out of phase with the drive pulse of power switch Q1 in the three-phase hybrid bridge circuit. The waveforms of the converter drive pulse, the primary and secondary line voltages of phase A, and the primary line current of phase A are as follows: Figure 6 As shown.

[0066] Based on the operating waveform of the three-phase asymmetric hybrid dual active bridge converter under reverse operating conditions, the power transfer characteristics under reverse operating conditions can be derived as shown below.

[0067] Under reverse operating conditions, the converter's power transfer relationship satisfies:

[0068]

[0069] To verify the feasibility of the proposed three-phase asymmetric hybrid dual active bridge converter, a simulation environment was built using Plesc. Figure 1 The converter model shown can realize asymmetric bidirectional power transmission. The input and output ports are equivalent to DC voltage sources. The circuit parameters are shown in Table 1.

[0070] Application scenario: Asymmetric bidirectional power transmission

[0071] Table 1 Simulation Circuit Parameters

[0072]

[0073] A. Forward operating condition simulation verification

[0074] Under positive operating conditions, the power switch is locked. and The phase difference of the drive pulses of each arm of the three-phase fully controlled bridge circuit The upper bridge arm power switch drive pulse width is During the simulation, the duty cycle is set. =0.5, at this time the power is transferred from the input port to the output port, and the simulated current and voltage results are as follows. Figure 7 As shown, where, , , The input port AC line voltage. , , This refers to the AC line current at the input port. , , The output port AC phase voltage. , , This refers to the AC phase current at the output port.

[0075] B. Reverse operating condition simulation verification

[0076] Under reverse operating conditions, the power switch is locked. and The drive pulses of power switch S1 and power switch S4 in the three-phase fully controlled bridge circuit are out of phase. The drive pulse of power switch S1 is out of phase with the drive pulse of power switch Q1 in the three-phase hybrid bridge circuit. ,set up , At this time, the output port transmits power to the input port, and the simulated current and voltage results are as follows: Figure 8 As shown, where , , The input port AC line voltage. , , This refers to the AC line current at the input port. , , The output port AC phase voltage. , , This refers to the AC phase current at the output port.

[0077] The simulation results demonstrate that the proposed three-phase asymmetric hybrid dual active bridge converter with asymmetric bidirectional power transmission capability can achieve asymmetric power transmission under both forward and reverse operating conditions, and that topology reconfiguration of the converter can be achieved by changing the modulation strategy. This converter is suitable for scenarios with unequal bidirectional power demands and can achieve asymmetric power transmission under both forward and reverse operating conditions at a relatively low cost.

[0078] It should be understood that this solution is not limited to the specific embodiments described above. Devices and structures not described in detail herein should be understood as being implemented in a manner common to the art. Any person skilled in the art can make many possible variations and modifications to this solution, or modify it into equivalent embodiments, without departing from the scope of this solution, using the methods and techniques disclosed above. This does not affect the substantive content of this solution. Therefore, any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of this solution, without departing from its scope, still fall within the protection scope of this solution.

Claims

1. A three-phase asymmetric hybrid dual active bridge converter, characterized in that: The system includes a three-phase fully controlled bridge circuit input port, a three-phase hybrid bridge circuit output port, and a medium-frequency three-phase transformer between the input and output ports. The three-phase fully controlled bridge circuit comprises three fully controlled power switch arms; the three-phase hybrid bridge circuit comprises one fully controlled power switch arm and two uncontrolled diode arms. The medium-frequency three-phase transformer is a Dyn type, with three taps on both the primary and secondary sides, and a primary-to-secondary turns ratio of [value missing]. The grounding wire of the three-phase transformer is connected to the midpoint of the DC stabilizing capacitor. The leakage inductance of the transformer is... .

2. The three-phase asymmetric hybrid dual active bridge converter according to claim 1, characterized in that: DC voltage at the input port DC voltage at the output port The relationship between them satisfies the following formula: in, This represents the DC voltage conversion ratio.

3. The three-phase asymmetric hybrid dual active bridge converter according to claim 2, characterized in that: The range satisfies: 。 4. A soft-switching modulation method for a three-phase asymmetric hybrid dual active bridge converter, characterized in that: This includes control of both forward power transfer mode and reverse power transfer mode. In forward power transfer mode, duty cycle control is used, and the converter transfers power from the input port to the output port. The specific process is as follows: The fully controlled power switch bridge arm of the three-phase hybrid bridge circuit is in a locked state, and the switching cycle of the converter is set to... The phase difference of the drive pulses of each arm of the three-phase fully controlled bridge circuit The drive pulses of the upper and lower bridge arm power switches of each bridge arm are complementary, and the drive pulse width of the upper bridge arm power switch is... , Duty cycle; In reverse power transfer mode, extended phase-shift control is used. The converter transfers power from the output port to the input port. The specific control process is as follows: The C-phase fully controlled power switch arm of the three-phase fully controlled bridge circuit is in a locked state, which in turn causes the uncontrolled diode arm of the three-phase hybrid bridge circuit to be in a combined locked state; the half-switching period of the converter is set to... The duty cycle of the fully controlled bridge arm power switches in three-phase fully controlled bridge circuits and three-phase hybrid bridge circuits. The phase difference between the drive pulse of the upper bridge arm switch in phase A and the drive pulse of the lower bridge arm switch in the three-phase fully controlled bridge circuit is 0.

5. The phase difference between the A-phase upper arm switch drive pulse and the A-phase upper arm switch drive pulse of the three-phase hybrid bridge circuit is... ,in, Compared to inward movement, Compared to moving outwards.

5. The soft-switching modulation method for the three-phase asymmetric hybrid dual active bridge converter according to claim 4, characterized in that: In forward power transfer mode, the converter's power transfer relationship satisfies: When DC voltage conversion ratio Satisfy 1 / 2 < When <2 / 3, the transmission power relationship satisfies: When DC voltage conversion ratio Satisfy 2 / 3 < When <1, the transmission power relationship satisfies: 。 6. The soft-switching modulation method for the three-phase asymmetric hybrid dual active bridge converter according to claim 4, characterized in that: when In reverse power transfer mode, the anode voltage of the diode in the uncontrolled diode bridge arm of the three-phase hybrid bridge circuit is always less than the cathode voltage, and the diode is in the off state.

7. The soft-switching modulation method for the three-phase asymmetric hybrid dual active bridge converter according to claim 6, characterized in that: In reverse power transfer mode, the converter's power transfer relationship satisfies: 。

Images