Power conversion circuit control method, system and device and storage medium

Abstract

The invention discloses a power conversion circuit control method, system and device and a storage medium, a first voltage conversion unit is controlled to be started in a fixed frequency phase shift modulation mode, in the initial stage of starting, a fly-wheel diode of a switching tube in a second voltage conversion unit is cut off due to the low voltage at the two ends, a resonant inductor and an excitation inductor of a transformer are connected in series for voltage division, and the resonant inductor and the excitation inductor are connected in series for voltage division; after the freewheeling diode is conducted, the voltage of the output side is boosted until the target starting voltage is reached, each switching tube in the second voltage conversion unit is controlled to be started, starting of the power conversion circuit is completed, the voltage on the direct current bus reaches the target direct current bus voltage in the starting process, and starting of the power conversion circuit is completed. The transmission efficiency of the power conversion circuit is ensured. The resonant inductor and the excitation inductor are subjected to voltage division within the cut-off time of the fly-wheel diode, so that the voltage difference between the two ends of the DC / DC unit is small, the follow current time of the fly-wheel diode is short, the time for bearing the large voltage difference between the two ends of the DC / DC unit is shortened, and the power conversion circuit is normally started.

Description

Technical Field

[0001] The present invention relates to the field of voltage conversion control, and in particular to a power conversion circuit control method, system, device and storage medium. Background Art

[0002] In power conversion circuits, especially bidirectional isolated AC / DC (Alternating Current / Direct Current) conversion circuits, the circuit usually includes an AC / DC unit and a DC / DC (Direct Current / Direct Current) unit. The DC / DC unit includes a first voltage conversion unit and a second voltage conversion unit. The two voltage conversion units are connected through a resonant inductor and a transformer.

[0003] In the prior art, when controlling the startup of a power conversion circuit, the switching transistors in the first and second voltage conversion units of the DC / DC unit are typically turned on synchronously until the DC-side voltage meets the requirements of the DC-side load, or the DC bus voltage meets the requirements of the AC-side load. However, when all the switching transistors in the DC / DC unit are in the switching state, a large voltage difference will exist across the resonant inductor of the DC / DC unit for a long period of time, resulting in a large inrush current in each component of the DC / DC unit. This may trigger the protection mechanism during the startup of the power conversion circuit, causing the entire power conversion circuit to shut down and be unable to restart, affecting the stability of the power conversion circuit. Summary of the Invention

[0004] The object of the present invention is to provide a power conversion circuit control method, system, device and storage medium. Because the resonant inductor divides the voltage with the excitation inductor during the cut-off time of the freewheeling diode, the voltage difference across the DC / DC unit is small, and the freewheeling time of the freewheeling diode is short, the time that the DC / DC unit is subjected to a large voltage difference is shortened, and the power conversion circuit is started normally.

[0005] To solve the above technical problems, the present invention provides a power conversion circuit control method, wherein the power conversion circuit includes an AC / DC unit and a DC / DC unit, wherein the AC / DC unit and the DC / DC unit are connected via a DC bus, and the DC / DC unit includes a first voltage conversion unit and a second voltage conversion unit, wherein the first voltage conversion unit is connected to the second voltage conversion unit via a resonant inductor and a transformer, and the method includes:

[0006] Obtain target DC bus voltage and target starting voltage;

[0007] Controlling each switch tube in the first voltage conversion unit to start with fixed-frequency phase-shift modulation, and controlling each switch tube in the second voltage conversion unit to turn off;

[0008] After the voltage at the output side of the DC / DC unit is increased to the target startup voltage, each switch in the second voltage conversion unit is controlled to start in fixed-frequency phase-shift modulation, so that the power conversion circuit is started;

[0009] The voltage on the DC bus reaches the target DC bus voltage during the startup process.

[0010] Preferably, the first voltage conversion unit is a bus-side conversion unit, and the second voltage conversion unit is a DC-side conversion unit;

[0011] Before controlling each switch tube in the first voltage conversion unit to start in fixed-frequency phase-shift modulation, the method further includes:

[0012] The AC / DC unit is controlled to start up to adjust the voltage on the DC bus to the target DC bus voltage.

[0013] Preferably, the step of determining the target starting voltage includes:

[0014] Obtaining power consumption parameters of a DC load connected to the DC side of the DC / DC unit;

[0015] determining a target output DC voltage on the DC side based on the power consumption parameter;

[0016] The target startup voltage is determined based on the target output DC voltage, and the target startup voltage is lower than the target output DC voltage.

[0017] Preferably, the first voltage conversion unit is a DC side conversion unit, and the second voltage conversion unit is a bus side conversion unit;

[0018] After the voltage at the output side of the DC / DC unit is increased to the target startup voltage, each switch in the second voltage conversion unit is controlled to start in fixed-frequency phase-shift modulation, so that the power conversion circuit is started, including:

[0019] After the voltage on the DC bus is increased to the target starting voltage, each switch tube in the bus-side conversion unit is controlled to start in fixed-frequency phase-shift modulation;

[0020] When the voltage on the DC bus rises to a target DC bus voltage, the AC / DC unit is controlled to start.

[0021] Preferably, after the power conversion circuit is started, the method further includes:

[0022] collecting the AC side voltage of the AC / DC unit and the DC side voltage of the DC / DC unit in real time;

[0023] The target DC bus voltage is updated based on the AC side voltage, the DC side voltage, and the expected gain of the DC / DC unit, so as to adjust the voltage setting value of the DC bus in real time.

[0024] Preferably, updating the target DC bus voltage based on the AC side voltage, the DC side voltage and the expected gain of the DC / DC unit includes:

[0025] determining a limited DC bus voltage based on the AC side voltage;

[0026] Determining a desired DC bus voltage based on a desired gain of the DC / DC unit and the DC side voltage;

[0027] determining a first DC bus voltage threshold and a second DC bus voltage threshold;

[0028] A target DC bus voltage that meets a preset condition is determined from the limited DC bus voltage, the first DC bus voltage threshold, the second DC bus voltage threshold, and the expected DC bus voltage.

[0029] Preferably, after controlling each switch tube in the second voltage conversion unit to start with fixed-frequency phase-shift modulation, the method further includes:

[0030] Obtaining a current DC bus voltage on the DC bus;

[0031] If the current DC bus voltage is not greater than a preset DC bus voltage, each switch tube in the DC / DC unit is controlled to be turned off; the preset DC bus voltage is determined based on the target DC bus voltage and the DC bus voltage ripple.

[0032] To solve the above technical problems, the present invention provides a power conversion circuit control system, wherein the power conversion circuit includes an AC / DC unit and a DC / DC unit, wherein the AC / DC unit and the DC / DC unit are connected via a DC bus, wherein the DC / DC unit includes a first voltage conversion unit and a second voltage conversion unit, wherein the first voltage conversion unit is connected to the second voltage conversion unit via a resonant inductor and a transformer, and wherein the system includes:

[0033] An acquisition unit, used for acquiring a target DC bus voltage and a target starting voltage;

[0034] a first control unit, configured to control each switch in the first voltage conversion unit to start up in fixed-frequency phase-shift modulation, and control each switch in the second voltage conversion unit to turn off;

[0035] a second control unit, configured to control each switch in the second voltage conversion unit to start up in a fixed-frequency phase-shift modulation manner after the voltage at the output side of the DC / DC unit is increased to a target startup voltage, so as to complete startup of the power conversion circuit;

[0036] The voltage on the DC bus reaches the target DC bus voltage during the startup process.

[0037] To solve the above technical problems, the present invention provides a power conversion circuit control device, comprising:

[0038] Memory for storing computer programs;

[0039] The processor is used to implement the steps of the power conversion circuit control method as described above when executing the computer program.

[0040] To solve the above technical problems, the present invention provides a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the steps of the power conversion circuit control method as described above are implemented.

[0041] The present application provides a power conversion circuit control method, system, device and storage medium. The method first controls the first voltage conversion unit to start with fixed-frequency phase-shift modulation. At the initial startup, the freewheeling diode of the switch tube in the second voltage conversion unit is cut off due to the low voltage at both ends. The resonant inductor and the excitation inductance of the transformer are connected in series to divide the voltage. After the freewheeling diode is turned on, the voltage on the output side is raised until it reaches the target startup voltage. The start-up of each switch tube in the second voltage conversion unit is controlled to complete the startup of the power conversion circuit, and the voltage on the DC bus reaches the target DC bus voltage during the startup process, thereby ensuring the transmission efficiency of the power conversion circuit. Because the resonant inductor divides the voltage with the excitation inductance during the freewheeling diode cut-off time, the voltage difference between the two ends of the DC / DC unit is small, and the freewheeling time of the freewheeling diode is short, which shortens the time that the two ends of the DC / DC unit are subjected to a large voltage difference, allowing the power conversion circuit to start normally. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the embodiments of the present invention, the following is a brief introduction to the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0043] Figure 1 A flow chart of a power conversion circuit control method provided in this application;

[0044] Figure 2A block diagram of a system for controlling a power conversion circuit provided in this application;

[0045] Figure 3 A schematic diagram of the structure of a power conversion circuit provided in this application;

[0046] Figure 4 A schematic diagram of the structure of a power conversion circuit control system provided by this application;

[0047] Figure 5 A schematic structural diagram of a power conversion circuit control device provided in this application;

[0048] Figure 6 A schematic diagram of a computer-readable storage medium provided in this application. DETAILED DESCRIPTION

[0049] The core of the present invention is to provide a power conversion circuit control method, system, device and storage medium. Because the resonant inductor divides the voltage with the excitation inductor during the cut-off time of the freewheeling diode, the voltage difference across the DC / DC unit is small, and the freewheeling time of the freewheeling diode is short, which shortens the time that the DC / DC unit is subjected to a large voltage difference across the two ends, allowing the power conversion circuit to start normally.

[0050] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0051] Please refer to Figure 1 , Figure 1 This is a flow chart of a power conversion circuit control method provided by the present application. The power conversion circuit includes an AC / DC unit and a DC / DC unit. The AC / DC unit and the DC / DC unit are connected via a DC bus. The DC / DC unit includes a first voltage conversion unit and a second voltage conversion unit. The first voltage conversion unit is connected to the second voltage conversion unit via a resonant inductor and a transformer. The method includes:

[0052] S11: Obtain target DC bus voltage and target starting voltage;

[0053] S12: Controlling each switch tube in the first voltage conversion unit to start with fixed-frequency phase-shift modulation, and controlling each switch tube in the second voltage conversion unit to turn off;

[0054] In the prior art, when controlling the startup of a power conversion circuit, the first voltage conversion unit and the second voltage conversion unit in the DC / DC unit are usually controlled to start at the same time, and the corresponding switching tubes in the first voltage conversion unit and the second voltage conversion unit are turned on synchronously. Then, the power devices in the DC / DC unit are all in the switching working state. During the startup of the DC / DC unit, the voltage at its output end requires multiple switching control cycles to reach the target output DC voltage. Then, during the multiple switching control cycles, a large voltage difference is maintained at both ends of the DC / DC unit. If the internal devices of the DC / DC unit remain in the working state with a large voltage difference for a long time, there may be a risk of burning. It is also possible that before the power conversion circuit starts, a large inrush current may occur due to the large voltage difference being borne by the devices, triggering a protection mechanism, causing the power conversion circuit to fail to start normally, thereby affecting the normal operation of the power conversion circuit.

[0055] For details, please refer to Figure 2 and Figure 3 , Figure 2 This is a system block diagram for controlling a power conversion circuit provided by the present application. Figure 3 This is a schematic diagram of the structure of a power conversion circuit provided in this application. Figure 2 The DC voltage and current detection module can detect the DC side of the DC / DC unit, that is, Figure 2 The DC voltage Vdc and DC current Idc at the DC in the AC / DC unit can be detected by the AC voltage and current detection module, that is, the AC side of the AC / DC unit. Figure 2 The AC voltage Vac and AC current Iac at the AC in the figure are detected by the bus voltage detection module, which can detect the DC bus voltage. Figure 2 The control device can adjust the control signal Dri1 when controlling the AC / DC unit and / or the control signal Dri2 when controlling the DC / DC unit according to the DC voltage Vdc and the DC current Idc, the AC voltage Vac and the AC current Iac, and the DC bus voltage Vbus, so that the power conversion circuit can perform power transmission.

[0056] Figure 3In the figure, VAC is the voltage on the AC side, Vac is the AC voltage, Iac is the AC current, VDC is the voltage on the DC side, Vdc is the DC voltage, Idc is the DC current, Vbus is the DC bus voltage, Cbus is the DC bus capacitance, L1 is the AC side filter inductor, C1 is the AC side filter capacitor, Q1 to Q4 are the switching tubes in the AC / DC unit, Q5 to Q12 are the switching tubes in the DC / DC unit, T1 is the transformer, C2 is the DC side filter capacitor, Lr, Lm and Cr1 constitute the LLC resonant circuit, Dri1 is the control signal for controlling Q1 to Q4, and Dri2 is the control signal for controlling Q5 to Q12. In the prior art, when controlling the startup of the power conversion circuit, if the power transmission direction of the power conversion circuit is from the AC side to the DC side, then Dri1 is output first to control the startup of the AC / DC unit, so that the DC bus voltage is raised, and then Dri2 is output to control the first voltage conversion unit and the second voltage conversion unit in the DC / DC unit to start synchronously. Specifically, Q5, Q8, Q9 and Q12 are switched synchronously, and Q6, Q7, Q10 and Q11 are switched synchronously. After the startup is triggered, the voltage on the DC side rises from 0V. When Q5, Q8, Q9 and Q12 are turned on and Q6, Q7, Q10 and Q11 are turned off, the voltage difference between the two ends of the DC / DC unit is the DC bus voltage -0V, that is, the DC bus voltage, and the switching to Q5, Q 8. When Q9 and Q12 are turned off and Q6, Q7, Q10, and Q11 are turned on, the voltage difference across the DC / DC unit is the negative DC bus voltage -0V, that is, the negative DC bus voltage. Therefore, the voltage difference across the DC / DC unit is the DC bus voltage during half of the switching control cycle, and the negative DC bus voltage during the other half of the cycle. That is, in the initial stage after startup, the absolute value of the voltage difference across the DC / DC unit is always the DC bus voltage. More specifically, the absolute value of the voltage difference across the resonant inductor Lr is always the DC bus voltage. This will undoubtedly cause the resonant inductor Lr to generate a large current due to the large voltage difference across the two ends, thereby triggering the protection mechanism and interrupting the startup process of the power conversion circuit.If the power transmission direction of the power conversion circuit is from the DC side to the AC side, then the output Dri2 controls the first voltage conversion unit and the second voltage conversion unit in the DC / DC unit to start synchronously, so that the DC bus voltage is raised, and then the output Dri1 controls the AC / DC unit to start. Specifically, when the output Dri2 controls the first voltage conversion unit and the second voltage conversion unit in the DC / DC unit to start synchronously, Q5, Q8, Q9 and Q12 are switched on synchronously, and Q6, Q7, Q10 and Q11 are switched on synchronously. After the start is triggered, the DC bus voltage rises from 0V, Q5, Q8, Q9 and Q12 are turned on, and Q6, Q7, Q10 and Q11 are turned off. The voltage difference between the two ends of the DC / DC unit is the voltage of the DC side -0V, that is, the DC side When Q5, Q8, Q9, and Q12 are turned off and Q6, Q7, Q10, and Q11 are turned on, the voltage difference across the DC / DC unit is -0V, the negative DC voltage. Therefore, the voltage difference across the DC / DC unit is the DC voltage for half of the switching control cycle and the negative DC voltage for the other half. In other words, during the initial stage after startup, the absolute value of the voltage difference across the DC / DC unit is always the DC voltage. More specifically, the absolute value of the voltage difference across the resonant inductor Lr is always the DC voltage. This will undoubtedly cause the resonant inductor Lr to generate a large current due to the large voltage difference across the DC voltage, thereby triggering the protection mechanism and interrupting the startup process of the power conversion circuit. Furthermore, because the DC voltage of the power conversion circuit takes a long time to climb to the target DC output voltage required by the DC side, the voltage across the DC / DC unit remains in a large voltage difference state for a long time during multiple switching control cycles, making it more likely to trigger the protection mechanism. ;

[0057] However, in the present application, when controlling the start-up of the power conversion circuit, regardless of the power transmission direction of the power conversion circuit, the switch tubes in the first voltage conversion unit and the second voltage conversion unit are not turned on synchronously, that is, the switch tube in the first voltage conversion unit is first controlled to start with fixed-frequency phase-shift modulation, and the switch tube in the second voltage conversion unit is turned off, and then the voltage on the output side is raised by the freewheeling diode in the second voltage conversion unit.

[0058] Specifically, after determining the target DC bus voltage and target starting voltage for normal operation of the power conversion circuit, when the power transmission direction of the power conversion circuit is from the AC side to the DC side, the switch tube in the first voltage conversion unit is first controlled to start with fixed-frequency phase-shift modulation, that is, the switch tube in the first voltage conversion unit operates in a fixed-frequency phase-shift switching state, but the switch tube in the second voltage conversion unit remains in the off state. In the initial stage after startup, the first voltage conversion unit inverts the DC bus voltage and transmits it to the transformer. However, when the switch tube in the second voltage conversion unit remains in the off state and the freewheeling diode is not turned on, the circuit connected to the secondary coil of the transformer is in the disconnected state, and the internal components of the first voltage conversion unit form a series circuit. Specifically, the resonant inductor Lr and the excitation inductance of the primary side of the transformer form a voltage divider circuit. The voltage difference across the resonant inductor Lr is reduced to less than the DC bus voltage, that is, the voltage difference across the internal components of the DC / DC unit is reduced, ensuring the normal operation of the internal components of the DC / DC unit; after the voltage across the transformer climbs to the conduction threshold voltage of the freewheeling diode, the freewheeling diode is turned on, and the second voltage conversion circuit puts the secondary coil of the transformer in the on state, then the voltage difference across the DC / DC unit is pulled to the DC bus voltage. It can be seen that through the control method in the present application, during the startup process of the power conversion circuit, within a switching control cycle, the absolute value of the voltage difference across the DC / DC unit is not always the DC bus voltage, but is the DC bus voltage only during the time when the freewheeling diode is turned on. Therefore, in the present application, the freewheeling diode is used to shorten the maintenance time of the state of a large voltage difference across the DC / DC unit, thereby reducing the risk of triggering the protection mechanism due to a large impact current of the internal devices of the DC / DC unit.

[0059] Accordingly, when the power transmission direction of the power conversion circuit is from the DC side to the AC side, the switch tube in the first voltage conversion unit is first controlled to start with fixed-frequency phase-shift modulation, that is, the switch tube in the first voltage conversion unit operates in a fixed-frequency phase-shift switching state, but the switch tube in the second voltage conversion unit remains in the off state. In the initial stage after startup, the first voltage conversion unit inverts the voltage on the DC side and transmits it to the transformer. However, when the switch tube in the second voltage conversion unit remains in the off state and the freewheeling diode is not turned on, the circuit connected to the secondary coil of the transformer is disconnected, and the internal devices of the first voltage conversion unit form a series loop; after the voltage on the DC side of the DC / DC unit climbs to the conduction threshold voltage of the freewheeling diode, the freewheeling diode is turned on, and the second voltage conversion unit causes the secondary coil of the transformer to be in the on state, so that the voltage difference between the two ends of the DC / DC unit is pulled to the voltage on the DC side. It can be seen that through the control method in the present application, during the startup process of the power conversion circuit, within a switching control cycle, the absolute value of the voltage difference across the DC / DC unit is not always the voltage on the DC side, but is the voltage on the DC side only during the time when the freewheeling diode is turned on. Therefore, in the present application, the freewheeling diode is used to shorten the maintenance time of the state of a large voltage difference across the DC / DC unit, thereby reducing the risk of triggering the protection mechanism due to a large impact current of the internal devices of the DC / DC unit.

[0060] S13: After the voltage at the output side of the DC / DC unit is increased to the target startup voltage, each switch in the second voltage conversion unit is controlled to start in fixed-frequency phase-shift modulation, so that the power conversion circuit is started;

[0061] The voltage on the DC bus reaches the target DC bus voltage during the startup process.

[0062] After the freewheeling diodes of the respective switching tubes in the second voltage conversion unit are used for freewheeling, thereby increasing the voltage on the output side to the target startup voltage, the respective switching tubes in the second voltage conversion unit are controlled to start up using fixed-frequency phase-shift modulation, so that the switching tubes in the first voltage conversion unit and the second voltage conversion unit operate synchronously. The voltage difference across the DC / DC unit is the difference between the DC bus voltage and the target startup voltage, or the difference between the DC side voltage and the target startup voltage. That is, the voltage difference across the DC / DC unit is small, thereby ensuring normal startup of the power conversion circuit.

[0063] Based on this, the DC / DC unit is first controlled to perform LLC fixed-frequency phase-shift modulation startup, that is, the switch tube in the first voltage conversion unit is in the fixed-frequency phase-shift switching state, and the switch tube in the second voltage conversion unit is in the off state. After the voltage on the output side is increased to the target startup voltage, the DC / DC unit is controlled to perform DAB fixed-frequency phase-shift modulation startup, that is, the switch tubes in the first voltage conversion unit and the second voltage conversion unit are both in the fixed-frequency phase-shift switching state.

[0064] It should be noted that during the start-up of the power conversion circuit, the DC bus voltage also reaches the target DC bus voltage. When the power transmission direction of the power conversion circuit is different, the output side is the DC bus side or the DC side. Therefore, when the power conversion circuit transmits power from the DC side to the AC side, the target DC bus voltage is the target DC voltage.

[0065] In summary, because the resonant inductor divides the voltage with the excitation inductor during the cut-off time of the freewheeling diode, the voltage difference across the DC / DC unit is small, and the freewheeling time of the freewheeling diode is short, which shortens the time that the DC / DC unit is subjected to a large voltage difference, allowing the power conversion circuit to start normally.

[0066] Based on the above embodiment:

[0067] As a preferred embodiment, the first voltage conversion unit is a bus-side conversion unit, and the second voltage conversion unit is a DC-side conversion unit;

[0068] Before controlling each switch tube in the first voltage conversion unit to start with fixed-frequency phase-shift modulation, the method further includes:

[0069] The AC / DC unit is controlled to start up to adjust the voltage on the DC bus to the target DC bus voltage.

[0070] When the first voltage conversion unit is a bus-side conversion unit and the second voltage conversion unit is a DC-side conversion unit, the output side of the DC / DC unit is the DC side and the input side is the DC bus side. The power conversion circuit converts the input AC power into DC output. To ensure the normal startup of the DC / DC unit, the target DC bus voltage is first determined, and then the AC / DC unit is controlled to start, so that the AC / DC unit rectifies the input AC power into the DC bus voltage. Only after the voltage on the DC bus rises to the target DC bus voltage, the various switching tubes in the first voltage conversion unit are controlled to start with fixed-frequency phase-shift modulation.

[0071] As a preferred embodiment, the step of determining the target starting voltage includes:

[0072] Obtaining power consumption parameters of a DC load connected to the DC side of the DC / DC unit;

[0073] determining a target output DC voltage on the DC side based on power consumption parameters;

[0074] A target startup voltage is determined based on the target output DC voltage, and the target startup voltage is less than the target output DC voltage.

[0075] When the first voltage conversion unit is a bus-side conversion unit and the second voltage conversion unit is a DC-side conversion unit, the DC bus side of the DC / DC unit is the input side and the DC side is the output side. Then, the power conversion circuit converts the input AC power into DC power output to power the DC load connected to the DC side. Therefore, the target output DC voltage of the DC side is determined according to the power consumption parameters of the DC load. For example, the target output DC voltage can be the rated voltage of the DC load, which is not limited in this application.

[0076] After determining the target output DC voltage, a target startup voltage is set based on the target output DC voltage. Specifically, the DC output voltage on the DC side of the DC / DC unit is first raised to the target startup voltage via a freewheeling diode. The second voltage conversion unit is then controlled to start up, and the switching transistor in the second voltage conversion unit is used to further raise the DC output voltage on the DC side of the DC / DC unit to the target output DC voltage. This prevents components in the DC / DC unit from being subjected to a large voltage difference for extended periods of time, while also improving the startup efficiency of the power conversion circuit. The target startup voltage can be, but is not limited to, a voltage value obtained by subtracting 50V from the target output DC voltage.

[0077] As a preferred embodiment, the first voltage conversion unit is a DC side conversion unit, and the second voltage conversion unit is a bus side conversion unit;

[0078] After the voltage at the output side of the DC / DC unit is increased to the target startup voltage, each switch in the second voltage conversion unit is controlled to start in fixed-frequency phase-shift modulation, so that the power conversion circuit is started, including:

[0079] After the voltage on the DC bus is increased to the target starting voltage, each switch tube in the bus-side conversion unit is controlled to start with fixed-frequency phase-shift modulation;

[0080] When the voltage on the DC bus rises to the target DC bus voltage, the AC / DC unit is controlled to start.

[0081] In this embodiment, when the first voltage conversion unit is a DC side conversion unit and the second voltage conversion unit is a bus side conversion unit, the input side of the DC / DC unit is the DC side and the output side is the DC bus side. The power conversion circuit converts the input DC power into AC power output. Therefore, in the power conversion circuit, the first voltage conversion unit is first started, and the DC bus voltage is raised to the target starting voltage through the freewheeling diode in the second voltage conversion unit. Then, the switch tube in the second voltage conversion unit is controlled to start, so as to avoid the components in the DC / DC unit from being kept in a state of a large voltage difference for a long time, while improving the starting efficiency of the DC / DC unit. When the voltage on the DC bus rises to the target DC bus voltage, the AC / DC unit is controlled to start, so that the AC / DC unit converts the DC bus voltage into AC power output to power the AC load.

[0082] It should be noted that when the first voltage conversion unit is a DC side conversion unit and the second voltage conversion unit is a bus side conversion unit, the target starting voltage can be set to a voltage lower than the target DC bus voltage, that is, the target starting voltage can be used but is not limited to the voltage value obtained by -50V of the target DC bus voltage, thereby improving the starting efficiency. After the switching tube in the second voltage conversion unit is started, the DC bus voltage is raised from the target starting voltage to the target DC bus voltage.

[0083] As a preferred embodiment, after the power conversion circuit is started, the method further includes:

[0084] Real-time acquisition of the AC side voltage of the AC / DC unit and the DC side voltage of the DC / DC unit;

[0085] Based on the AC side voltage, the DC side voltage and the desired gain of the DC / DC unit, the target DC bus voltage is updated to adjust the DC bus voltage setting value in real time.

[0086] Considering that after the power conversion circuit is started, if the DC side voltage remains unchanged and the target DC bus voltage also remains unchanged, then the gain of the DC / DC unit will remain unchanged. However, in actual situations, the DC side voltage may change, for example, with changes in the load. If the target DC bus voltage remains unchanged, the gain of the DC / DC unit will also change accordingly. If the gain of the DC / DC unit cannot be maintained at the desired gain, the power transmission efficiency of the power conversion circuit will be reduced, resulting in increased system losses.

[0087] Therefore, the target DC bus voltage in this application is not fixed, but can be adjusted in real time based on the AC side voltage, the DC side voltage and the desired gain, thereby avoiding large changes in the gain of the DC / DC unit and ensuring the power transmission efficiency of the power conversion circuit.

[0088] It should be noted that the gain represents the ratio between the output voltage and the input voltage of the DC / DC unit. When the gain is the desired gain, the power transmission efficiency of the power conversion circuit is maximized.

[0089] As a preferred embodiment, updating the target DC bus voltage based on the AC side voltage, the DC side voltage, and the desired gain of the DC / DC unit includes:

[0090] Determining a limit on the DC bus voltage based on the AC side voltage;

[0091] Determine a desired DC bus voltage based on a desired gain of the DC / DC unit and a DC side voltage;

[0092] determining a first DC bus voltage threshold and a second DC bus voltage threshold;

[0093] A target DC bus voltage that meets a preset condition is determined from the limited DC bus voltage, the first DC bus voltage threshold, the second DC bus voltage threshold, and the expected DC bus voltage.

[0094] When adjusting the target DC bus voltage, the DC bus voltage is first limited based on the AC side voltage. The DC bus voltage is limited to a bus voltage that meets the AC side voltage requirements, which is a voltage that ensures that the equipment connected to the AC side can work normally. Then, the expected DC bus voltage is determined based on the expected gain and the DC side voltage, that is, the DC bus voltage that can currently maximize the power output efficiency of the power conversion circuit is determined. Finally, the bus voltage range is framed based on the first DC bus voltage threshold and the second DC bus voltage threshold, and then the target DC bus voltage is determined. That is, the target DC bus voltage needs to meet the requirements of the equipment connected to the AC side and ensure the power transmission efficiency of the power conversion circuit.

[0095] Specifically, when the power conversion circuit is in forward power transmission, that is, converting AC power into DC power output, the target DC bus voltage is determined as follows:

[0096] ;

[0097] in, is the target DC bus voltage in the positive direction, min() is the minimum value among the values ​​in the brackets, and max() is the maximum value among the values ​​in the brackets. is the effective value of the AC side voltage, m is a real number not less than 0, is the positive limit DC bus voltage, is the positive DC side voltage, n is the transformer ratio, Mnom_c is the expected positive gain, is the desired DC bus voltage in the positive direction, is the first DC bus voltage threshold, is the second DC bus voltage threshold.

[0098] When determining the forward target DC bus voltage, it is determined based on the comparison result of the forward expected DC bus voltage and the forward limited DC bus voltage and the bus voltage range framed by the first forward DC bus voltage threshold and the second forward DC bus voltage threshold. The forward expected DC bus voltage is determined based on the forward DC side voltage and the forward expected gain. Since the forward expected gain is set according to the power conversion efficiency requirement of the power conversion circuit, the forward expected gain is a fixed value, so the expected DC bus voltage can change with the change of the DC side voltage. Therefore, the power transmission efficiency of the DC / DC unit can remain stable and meet the requirements. In addition, the peak value of the AC side voltage is determined in combination with the effective value of the AC side voltage, and then mV is added to the peak value of the AC side voltage to leave a mV margin for the peak value of the AC input voltage to compensate for the loss in the circuit and generate a forward limited DC bus voltage, wherein mV can be 10V, which is not limited in this application.

[0099] When the first voltage conversion unit is a bus-side conversion unit and the second voltage conversion unit is a DC-side conversion unit, the DC bus side of the DC / DC unit is the input side and the DC side is the output side. Therefore, the gain is the ratio between the DC side voltage and the DC bus voltage. To achieve the desired positive gain, after determining the DC side voltage, the DC side voltage can be divided by the desired positive gain to reversely calculate the desired positive DC bus voltage that will achieve the desired positive gain. Furthermore, because the first and second voltage conversion units in the DC / DC unit are isolated by a transformer, the DC side voltage must be multiplied by the transformer's transformation ratio n and then divided by the desired positive gain to accurately determine the desired positive DC bus voltage.

[0100] Based on this, if the forward limited DC bus voltage and the forward expected DC bus voltage are both within the bus voltage range framed by the first forward DC bus voltage threshold and the second forward DC bus voltage threshold, a larger value is selected from the forward limited DC bus voltage and the forward expected DC bus voltage as the forward target DC bus voltage, and the maximum forward target DC bus voltage is the second DC bus voltage threshold and the minimum is the first DC bus voltage threshold, so as to ensure the normal operation of the power conversion circuit while making the power transmission efficiency of the power conversion circuit higher.

[0101] It should also be noted that the forward expected gain can be determined by the intersection of the gain-frequency curves corresponding to different DC loads, and this application does not limit this.

[0102] When the power conversion circuit is in reverse power transmission, that is, converting DC power into AC power output, the target DC bus voltage is determined as follows:

[0103] ;

[0104] in, is the reverse target DC bus voltage, min() is the minimum value among the values ​​in the brackets, and max() is the maximum value among the values ​​in the brackets. is the effective value of the reverse AC side voltage, m is a real number not less than 0, To limit the reverse DC bus voltage, is the DC side voltage, Mnom_f is the desired reverse gain, is the desired reverse DC bus voltage, n is the transformer ratio, is the first DC bus voltage threshold, is the second DC bus voltage threshold.

[0105] When determining the reverse target DC bus voltage, it is determined based on the comparison result of the reverse expected DC bus voltage and the reverse limited DC bus voltage and the bus voltage range framed by the reverse first DC bus voltage threshold and the second DC bus voltage threshold. The reverse expected DC bus voltage is determined based on the reverse DC side voltage and the reverse expected gain. Since the reverse expected gain is set according to the power conversion efficiency requirement of the power conversion circuit, the reverse expected gain is a fixed value, so the reverse expected DC bus voltage can change with the change of the DC side voltage. Therefore, the power transmission efficiency of the DC / DC unit can remain stable and meet the requirements. In addition, the peak value of the AC side voltage is determined in combination with the effective value of the reverse AC side voltage, and then mV is added to the peak value of the AC side voltage to leave a mV margin for the peak value of the AC output voltage to compensate for the loss in the circuit and generate a reverse limited DC bus voltage, wherein mV can be 10V, which is not limited in this application.

[0106] When the second voltage conversion unit is a bus-side conversion unit and the first voltage conversion unit is a DC-side conversion unit, the DC bus side of the DC / DC unit is the output side and the DC side is the input side. In this case, the gain is the ratio between the DC bus voltage and the DC side voltage. To achieve the inverse desired gain, after determining the DC side voltage, the DC side voltage can be multiplied by the inverse desired gain to infer the inverse desired DC bus voltage that achieves the inverse desired gain. Furthermore, because the first and second voltage conversion units in the DC / DC unit are isolated by a transformer, the DC side voltage must be multiplied by the transformer's transformation ratio n and then by the inverse desired gain to accurately determine the inverse desired DC bus voltage.

[0107] Based on this, if the reverse limited DC bus voltage and the reverse expected DC bus voltage are both within the bus voltage range framed by the reverse first DC bus voltage threshold and the second DC bus voltage threshold, a larger value is selected from the reverse limited DC bus voltage and the reverse expected DC bus voltage as the reverse target DC bus voltage, and the maximum reverse target DC bus voltage is the reverse second DC bus voltage threshold, and the minimum is the reverse first DC bus voltage threshold, so as to ensure the normal operation of the power conversion circuit while making the power transmission efficiency of the power conversion circuit higher.

[0108] It should also be noted that the reverse expected gain can be determined by the intersection of the gain-frequency curves corresponding to different AC loads, and this application does not limit this.

[0109] As a preferred embodiment, after controlling each switch tube in the second voltage conversion unit to start with fixed-frequency phase-shift modulation, the method further includes:

[0110] Get the current DC bus voltage on the DC bus;

[0111] If the current DC bus voltage is not greater than the preset DC bus voltage, each switch tube in the DC / DC unit is controlled to be turned off; the preset DC bus voltage is determined based on the target DC bus voltage and the DC bus voltage ripple.

[0112] In addition, not only is it necessary to reduce the maintenance time of the large voltage difference across the DC / DC unit when the power conversion circuit is started, but it is also necessary to promptly control the shutdown of each switch tube in the DC / DC unit when it is detected that the current DC bus voltage is not greater than the preset DC bus voltage minimum value during the operation of the power conversion circuit to avoid the voltage difference across the DC / DC unit from increasing due to the decrease in the current DC bus voltage.

[0113] Specifically, before obtaining the current DC bus voltage on the DC bus between the AC / DC unit and the DC / DC unit, the target DC bus voltage and the DC bus voltage ripple may be determined first, and then the preset DC bus voltage may be determined:

[0114] ;

[0115] in, is the preset DC bus voltage, is the target DC bus voltage, is the DC bus voltage ripple, and a is a real number greater than 1.

[0116] Specifically, when determining the preset DC bus voltage, the target DC bus voltage can be subtracted from the DC bus voltage ripple, and then from a set voltage value. The DC bus voltage ripple refers to the periodic or random fluctuation or deviation of the voltage on the DC bus relative to its nominal value or average value. aV is set based on the load requirements and the hardware parameters of the DC / DC unit, and is a voltage threshold value that will cause a large voltage difference across the DC / DC unit and will cause the power conversion circuit to malfunction. a can be, but is not limited to, 20. Of course, ensuring that the preset DC bus voltage is greater than the voltage value that causes a large voltage difference across the DC / DC unit and will cause the power conversion circuit to malfunction is essential. This allows the power conversion circuit to be actively controlled to shut down before the power conversion circuit abnormally shuts down due to the voltage difference across the DC / DC unit, thereby ensuring the stability of the power conversion circuit.

[0117] When determining the DC bus voltage ripple, it can be determined based on the capacitance value of the DC bus capacitor, the output power of the power conversion circuit, and the switching frequency:

[0118] ;

[0119] Wherein, Po is the output power of the power conversion circuit, fz is the switching frequency, and Cbus is the capacitance value of the DC bus capacitor.

[0120] Of course, the output power of the power conversion circuit can be determined according to the AC output voltage and the AC output current, or according to the DC output voltage and the DC output current.

[0121] Please refer to Figure 4 , Figure 4 This is a schematic diagram of the structure of a power conversion circuit control system provided by the present application. The power conversion circuit includes an AC / DC unit and a DC / DC unit. The AC / DC unit and the DC / DC unit are connected via a DC bus. The DC / DC unit includes a first voltage conversion unit and a second voltage conversion unit. The first voltage conversion unit is connected to the second voltage conversion unit via a resonant inductor and a transformer. The system includes:

[0122] An acquisition unit 41 is configured to acquire a target DC bus voltage and a target starting voltage;

[0123] A first control unit 42 is configured to control each switch in the first voltage conversion unit to start up using fixed-frequency phase-shift modulation, and to control each switch in the second voltage conversion unit to turn off;

[0124] The second control unit 43 is configured to control each switch in the second voltage conversion unit to start up in a fixed-frequency phase-shift modulation manner after the voltage at the output side of the DC / DC unit is increased to the target startup voltage, so as to complete the startup of the power conversion circuit;

[0125] The voltage on the DC bus reaches the target DC bus voltage during the startup process.

[0126] For an introduction to the power conversion circuit control system provided by the present invention, please refer to the above method embodiment, and the present invention will not be described in detail here.

[0127] Please refer to Figure 5 , Figure 5 This is a schematic diagram of the structure of a power conversion circuit control device provided in this application, which includes:

[0128] Memory 51, for storing computer programs;

[0129] The processor 52 is configured to implement the steps of the power conversion circuit control method described above when executing a computer program.

[0130] For an introduction to the power conversion circuit control device provided by the present invention, please refer to the above method embodiment, and the present invention will not be described in detail here.

[0131] Please refer to Figure 6 , Figure 6 This is a schematic diagram of a computer-readable storage medium provided in the present application. The computer-readable storage medium 61 in the present invention stores a computer program 62, which implements the steps of the power conversion circuit control method as described above when executed by the processor 52.

[0132] For an introduction to the computer-readable storage medium provided by the present invention, please refer to the above method embodiment, and the present invention will not go into details here.

[0133] It should also be noted that, in this specification, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of additional identical elements in the process, method, article, or apparatus comprising the element.

[0134] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A power conversion circuit control method, characterized in that: The power conversion circuit includes an AC / DC unit and a DC / DC unit, wherein the AC / DC unit and the DC / DC unit are connected via a DC bus; the DC / DC unit includes a first voltage conversion unit and a second voltage conversion unit, wherein the first voltage conversion unit is connected to the second voltage conversion unit via a resonant inductor and a transformer; and the method includes: Obtain target DC bus voltage and target starting voltage; Controlling each switch tube in the first voltage conversion unit to start with fixed-frequency phase-shift modulation, and controlling each switch tube in the second voltage conversion unit to turn off; After the voltage at the output side of the DC / DC unit is increased to the target startup voltage, each switch in the second voltage conversion unit is controlled to start in fixed-frequency phase-shift modulation, so that the power conversion circuit is started; The voltage on the DC bus reaches the target DC bus voltage during the startup process.

2. The power conversion circuit control method according to claim 1, wherein: The first voltage conversion unit is a bus-side conversion unit, and the second voltage conversion unit is a DC-side conversion unit; Before controlling each switch tube in the first voltage conversion unit to start in fixed-frequency phase-shift modulation, the method further includes: The AC / DC unit is controlled to start up to adjust the voltage on the DC bus to the target DC bus voltage.

3. The power conversion circuit control method according to claim 2, wherein: The step of determining the target startup voltage includes: Obtaining power consumption parameters of a DC load connected to the DC side of the DC / DC unit; determining a target output DC voltage on the DC side based on the power consumption parameter; The target startup voltage is determined based on the target output DC voltage, and the target startup voltage is lower than the target output DC voltage.

4. The power conversion circuit control method according to claim 1, wherein: The first voltage conversion unit is a DC side conversion unit, and the second voltage conversion unit is a bus side conversion unit; After the voltage at the output side of the DC / DC unit is increased to the target startup voltage, each switch in the second voltage conversion unit is controlled to start in fixed-frequency phase-shift modulation, so that the power conversion circuit is started, including: After the voltage on the DC bus is increased to the target starting voltage, each switch tube in the bus-side conversion unit is controlled to start in fixed-frequency phase-shift modulation; When the voltage on the DC bus rises to a target DC bus voltage, the AC / DC unit is controlled to start.

5. The power conversion circuit control method according to claim 1, wherein: After the power conversion circuit is started, the method further includes: collecting the AC side voltage of the AC / DC unit and the DC side voltage of the DC / DC unit in real time; The target DC bus voltage is updated based on the AC side voltage, the DC side voltage, and the expected gain of the DC / DC unit, so as to adjust the voltage setting value of the DC bus in real time.

6. The power conversion circuit control method according to claim 5, wherein: Updating the target DC bus voltage based on the AC side voltage, the DC side voltage, and the expected gain of the DC / DC unit includes: determining a limited DC bus voltage based on the AC side voltage; Determining a desired DC bus voltage based on a desired gain of the DC / DC unit and the DC side voltage; determining a first DC bus voltage threshold and a second DC bus voltage threshold; A target DC bus voltage that meets a preset condition is determined from the limited DC bus voltage, the first DC bus voltage threshold, the second DC bus voltage threshold, and the expected DC bus voltage.

7. The power conversion circuit control method according to any one of claims 1 to 6, wherein: After controlling each switch tube in the second voltage conversion unit to start with fixed-frequency phase-shift modulation, the method further includes: Obtaining a current DC bus voltage on the DC bus; If the current DC bus voltage is not greater than a preset DC bus voltage, each switch tube in the DC / DC unit is controlled to be turned off; the preset DC bus voltage is determined based on the target DC bus voltage and the DC bus voltage ripple.

8. A power conversion circuit control system, characterized in that: The power conversion circuit includes an AC / DC unit and a DC / DC unit, wherein the AC / DC unit and the DC / DC unit are connected via a DC bus; the DC / DC unit includes a first voltage conversion unit and a second voltage conversion unit, wherein the first voltage conversion unit is connected to the second voltage conversion unit via a resonant inductor and a transformer; and the system includes: An acquisition unit, used for acquiring a target DC bus voltage and a target starting voltage; a first control unit, configured to control each switch in the first voltage conversion unit to start up in fixed-frequency phase-shift modulation, and control each switch in the second voltage conversion unit to turn off; a second control unit, configured to control each switch in the second voltage conversion unit to start up in a fixed-frequency phase-shift modulation manner after the voltage at the output side of the DC / DC unit is increased to a target startup voltage, so as to complete startup of the power conversion circuit; The voltage on the DC bus reaches the target DC bus voltage during the startup process.

9. A power conversion circuit control device, characterized in that: include: Memory for storing computer programs; A processor, configured to implement the steps of the power conversion circuit control method according to any one of claims 1 to 7 when executing a computer program.

10. A computer-readable storage medium, characterized in that The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps of the power conversion circuit control method according to any one of claims 1 to 7 are implemented.

Images