Control method of power conversion circuit, power conversion equipment and power supply system

Abstract

The invention provides a control method of a power conversion circuit, power conversion equipment and a power supply system. The power conversion circuit comprises a primary side bridge circuit, a transformer, a resonant inductor and a secondary side bridge circuit, and correspondingly, the control method comprises the following steps: acquiring a real-time DC voltage on a second end of the primary side bridge circuit, and a real-time AC voltage and a real-time AC current on a second end of the secondary side bridge circuit; calculating the real-time transmission power of the power conversion circuit according to the real-time AC voltage and the real-time AC current; according to the real-time transmission power, the preset power transmission direction, the real-time direct-current voltage and the real-time alternating-current voltage, a target inner phase shift angle of the primary-side bridge circuit and a target outer phase shift angle between the primary-side bridge circuit and the secondary-side bridge circuit are obtained through decoupling; and controlling the power conversion circuit to transmit power in a preset power transmission direction according to the target inner phase shift angle and the target outer phase shift angle. According to the method, the power conversion circuit can realize bidirectional operation.

Description

Technical Field

[0001] The present application relates to the field of power electronics technology, and in particular to a control method for a power conversion circuit, a power conversion device, and a power supply system. Background Art

[0002] In the field of new energy, micro inverters are increasingly used. Currently, most micro inverters on the market are two-level topology solutions, and usually only support unidirectional operation. Energy can only be transferred from the DC side to the grid side. Therefore, when the micro inverter is used with an energy storage battery, it is impossible to charge the energy storage battery. Summary of the invention

[0003] In view of the deficiencies in the prior art, the present application provides a control method for a power conversion circuit, a power conversion device and a power supply system, which can realize bidirectional operation of the power conversion circuit.

[0004] The first aspect of the present application provides a control method for a power conversion circuit. The power conversion circuit includes a primary bridge circuit, a transformer, a resonant inductor, and a secondary bridge circuit. The first end of the primary bridge circuit is connected to the primary side of the transformer, the first end of the secondary bridge circuit is connected to the secondary side of the transformer through the resonant inductor, the second end of the primary bridge circuit is used to connect a DC power supply or a DC load, and the second end of the secondary bridge circuit is used to connect an AC power supply or an AC load. Correspondingly, the control method includes: obtaining a real-time DC voltage on the second end of the primary bridge circuit, a real-time AC voltage and a real-time AC current on the second end of the secondary bridge circuit; calculating the real-time transmission power of the power conversion circuit according to the real-time AC voltage and the real-time AC current; decoupling the target inner phase shift angle of the primary bridge circuit and the target outer phase shift angle between the primary bridge circuit and the secondary bridge circuit according to the real-time transmission power, the preset power transmission direction, the real-time DC voltage, and the real-time AC voltage; and controlling the power conversion circuit to transmit power according to the preset power transmission direction according to the target inner phase shift angle and the target outer phase shift angle.

[0005] In one embodiment, a target inner phase shift angle of a primary bridge circuit and a target outer phase shift angle between the primary bridge circuit and the secondary bridge circuit are decoupled according to real-time transmission power, a preset power transmission direction, a real-time DC voltage, and a real-time AC voltage, including: determining the polarity of the real-time transmission power according to the preset power transmission direction; obtaining a transmission power model of the power conversion circuit; the transmission power model is used to indicate the correlation between the real-time transmission power and the real-time DC voltage, the real-time AC voltage, the target inner phase shift angle, and the target outer phase shift angle; according to the real-time DC voltage, the real-time AC voltage, and the real-time transmission power with polarity, the target inner phase shift angle and the target outer phase shift angle are obtained by decoupling the transmission power model.

[0006] In one embodiment, the polarity of the real-time transmission power is determined according to a preset power transmission direction, including: when the preset power transmission direction is from the primary bridge circuit to the secondary bridge circuit, the real-time transmission power is a first polarity; accordingly, the target external shift phase angle is a first polarity; when the preset power transmission direction is from the secondary bridge circuit to the primary bridge circuit, the real-time transmission power is a second polarity; accordingly, the target external shift phase angle is a second polarity, and the second polarity is opposite to the first polarity.

[0007] In one embodiment, the transmission power model is used to indicate that the real-time transmission power is positively correlated with the real-time DC voltage, the real-time transmission power is positively correlated with the real-time AC voltage, the real-time transmission power is positively correlated with the cosine value of half the target inner phase shift angle, and the real-time transmission power is positively correlated with the sine value of the target outer phase shift angle.

[0008] In one embodiment, the primary bridge circuit includes a first bridge arm and a second bridge arm connected in parallel, the midpoints of the first bridge arm and the second bridge arm constitute the first end of the primary bridge circuit, and the two ends of the first bridge arm and the second bridge arm constitute the second end of the primary bridge circuit; the secondary bridge circuit includes a third bridge arm and a fourth bridge arm connected in parallel, the midpoints of the third bridge arm and the fourth bridge arm constitute the first end of the secondary bridge circuit, and the two ends of the third bridge arm and the fourth bridge arm constitute the second end of the secondary bridge circuit; wherein the first bridge arm, the second bridge arm and the third bridge arm all include a switch tube, and the fourth bridge arm includes a capacitor. Accordingly, the transmission power model is also used to indicate that the real-time transmission power is positively correlated with the turns ratio of the transformer, and the real-time transmission power is negatively correlated with the equivalent impedance of the resonant circuit, wherein the resonant circuit at least includes a resonant inductor.

[0009] In one embodiment, the primary bridge circuit includes a first bridge arm and a second bridge arm connected in parallel, the midpoint of the first bridge arm and the second bridge arm constitutes the first end of the primary bridge circuit, and the two ends of the first bridge arm and the second bridge arm constitute the second end of the primary bridge circuit; the secondary bridge circuit includes a third bridge arm and a fourth bridge arm connected in parallel, the midpoint of the third bridge arm and the fourth bridge arm constitutes the first end of the secondary bridge circuit, and the two ends of the third bridge arm and the fourth bridge arm constitute the second end of the secondary bridge circuit; wherein the first bridge arm, the second bridge arm and the third bridge arm all include switching tubes, and the fourth bridge arm includes a capacitor. Correspondingly, the power conversion circuit is controlled to transmit power in a preset power transmission direction according to the target inner phase shift angle and the target outer phase shift angle, including: controlling the phase difference between the first bridge arm and the second bridge arm in the primary bridge circuit to be equal to the target inner phase shift angle; when the target outer phase shift angle is a first polarity, controlling the voltage waveform on the first end of the primary bridge circuit to lead the voltage waveform on the first end of the secondary bridge circuit by the target outer phase shift angle; or, when the target outer phase shift angle is a second polarity, controlling the voltage waveform on the first end of the primary bridge circuit to lag the voltage waveform on the first end of the secondary bridge circuit by the target outer phase shift angle.

[0010] In one embodiment, the first bridge arm includes a first switch tube and a second switch tube connected in series, the second bridge arm includes a third switch tube and a fourth switch tube connected in series, the third bridge arm includes a fifth switch tube, a sixth switch tube, a seventh switch tube and an eighth switch tube connected in series in sequence, and the fourth bridge arm includes a first capacitor and a second capacitor connected in series. Accordingly, controlling the power conversion circuit to transmit power in a preset power transmission direction according to the target inner phase shift angle and the target outer phase shift angle includes: controlling the first switch tube and the second switch tube to be complementary turned on, the third switch tube and the fourth switch tube to be complementary turned on, and the conduction phase difference between the first switch tube and the third switch tube is equal to the target inner phase shift angle; when the real-time AC voltage is in the positive half cycle, controlling the fifth switch tube and the seventh switch tube to be complementary turned on, and the sixth switch tube and the eighth switch tube to be constantly turned on; when the real-time AC voltage is in the negative half cycle, controlling the fifth switch tube and the seventh switch tube to be constantly turned on, and the sixth switch tube and the eighth switch tube to be complementary turned on.

[0011] In one embodiment, the target inner phase shift angle is within the range of (0, π), and the target outer phase shift angle is within the range of (-π, π).

[0012] The second aspect of the present application provides a power conversion device. The power conversion device includes a power conversion circuit and a controller, the power conversion circuit includes a primary bridge circuit, a transformer, a resonant inductor and a secondary bridge circuit, the first end of the primary bridge circuit is connected to the primary side of the transformer, the first end of the secondary bridge circuit is connected to the secondary side of the transformer through the resonant inductor, the second end of the primary bridge circuit is used to connect a DC power supply or a DC load, and the second end of the secondary bridge circuit is used to connect an AC power supply or an AC load. The controller is connected to the power conversion circuit, and the controller is used to decouple the target inner phase shift angle of the primary bridge circuit and the target outer phase shift angle between the primary bridge circuit and the secondary bridge circuit according to the real-time transmission power and the preset power transmission direction of the power conversion circuit, the real-time DC voltage on the second end of the primary bridge circuit, and the real-time AC voltage on the second end of the secondary bridge circuit, and control the power conversion circuit to transmit power according to the preset power transmission direction according to the target inner phase shift angle and the target outer phase shift angle.

[0013] In one embodiment, when the preset power transmission direction is from the primary bridge circuit to the secondary bridge circuit, the target external phase shift angle is a first polarity; when the preset power transmission direction is from the secondary bridge circuit to the primary bridge circuit, the target external phase shift angle is a second polarity; when the preset power transmission direction changes, the polarity of the target external phase shift angle switches between the first polarity and the second polarity, and the first polarity is opposite to the second polarity.

[0014] In one embodiment, the transmission power model is used to indicate that the real-time transmission power is positively correlated with the real-time DC voltage, the real-time transmission power is positively correlated with the real-time AC voltage, the real-time transmission power is positively correlated with the cosine value of half the target inner phase shift angle, and the real-time transmission power is positively correlated with the sine value of the target outer phase shift angle.

[0015] The third aspect of the present application provides a power supply system, which includes: a DC power supply and the power conversion device described in the second aspect or any one of the embodiments of the second aspect, the DC power supply is connected to the second end of the primary bridge circuit, the second end of the secondary bridge circuit is connected to the common coupling point, the DC power supply includes at least one of an energy storage device and a photovoltaic power generation device, and the common coupling point is used to connect at least one of a power grid and an AC load.

[0016] Compared with the prior art, this application has at least the following advantages: The present application utilizes the real-time transmission power, preset power transmission direction, real-time DC voltage and real-time AC voltage of the power conversion circuit to decouple the target inner phase shift angle and the target outer phase shift angle, and then can control the power conversion circuit to transmit power in the preset power transmission direction according to the target inner phase shift angle and the target outer phase shift angle. Through such a design, the power conversion circuit can have both forward operation function and reverse operation function, and can realize forward and reverse switching. When the DC power supply adopts an energy storage device, the power conversion circuit can charge and discharge the energy storage device, thereby effectively broadening the application field and scope of the power conversion circuit.

[0017] Moreover, the power conversion circuit in the present application is a single-stage structure, and there is no need to design different control methods for different operating directions of the power conversion circuit. Therefore, the control method, power conversion equipment and power supply system of the power conversion circuit in the present application are simple and easy to implement, with low control complexity and high control efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a structural schematic diagram of a power supply system provided in an embodiment of the present application.

[0019] Figure 2 It is a topological diagram of the power conversion circuit provided in an embodiment of the present application.

[0020] Figure 3 It is a circuit diagram of a power conversion circuit provided in an embodiment of the present application.

[0021] Figure 4 yes Figure 2 The working waveform diagram of the power conversion circuit shown is when it is running in the forward direction and the real-time AC voltage is in the positive half cycle.

[0022] Figure 5 It is a flow chart of a control method of a power conversion circuit provided in an embodiment of the present application.

[0023] Figure 6 yes Figure 5 A detailed flow chart of step S3 in the method.

[0024] Figure 7 yes Figure 3 The simulated waveforms of real-time AC voltage, real-time AC current and real-time transmission power of the power conversion circuit shown in the forward operation.

[0025] Figure 8 yes Figure 3 The simulated waveforms of the real-time AC voltage, real-time AC current and real-time transmission power of the power conversion circuit shown in FIG. 1 are shown in FIG.

[0026] Fig. 9 yes Figure 3 The shown power conversion circuit is a simulation waveform diagram of real-time AC voltage, real-time AC current and real-time transmission power during forward and reverse switching.

[0027] Main component symbols 100-power supply system, 10-DC power supply, 11-energy storage equipment, 12-photovoltaic power generation equipment, 20-power conversion equipment, 21-power conversion circuit, 211-primary bridge circuit, 2111-first bridge arm, 2112-second bridge arm, 212-transformer, 213-resonant inductor, 214-secondary bridge circuit, 2141-third bridge arm, 2142-fourth bridge arm, 22-controller, 30- point of common coupling, 40- grid, 50- AC load. DETAILED DESCRIPTION

[0028] In order to enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only embodiments of a part of the present application, not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work should fall within the scope of protection of the present application. In the absence of conflict, the following different embodiments and features in the embodiments can be combined with each other.

[0029] In the field of new energy, micro inverters are increasingly used. Currently, most micro inverters on the market are two-level topology solutions, and usually only support unidirectional operation. Energy can only be transferred from the DC side to the grid side. Therefore, when the micro inverter is used with an energy storage battery, it is impossible to charge the energy storage battery. Obviously, such micro inverters have great limitations.

[0030] Therefore, the embodiments of the present application propose a control method for a power conversion circuit, a power conversion device, and a power supply system, which can realize bidirectional operation of the power conversion circuit and broaden the application scope of the power conversion circuit.

[0031] Specifically, see Figure 1 , shows a topological diagram of the power supply system 100 according to an embodiment of the present application.

[0032] like Figure 1 As shown, the power supply system 100 includes a DC power supply 10 and a power conversion device 20. For the convenience of description, the DC power supply 10 is an energy storage device 11 and a photovoltaic power generation device 12. At this time, the power supply system 100 can also be called a photovoltaic storage and charging system.

[0033] It should be understood that in other scenarios, only the photovoltaic power generation device 12 or the energy storage device 11 may be used as the DC power source 10, or other devices that can provide DC power may be used as the DC power source 10. In the scenario where only the photovoltaic power generation device 12 is used as the DC power source 10, the power supply system 100 may also be called a photovoltaic system, and in the scenario where only the energy storage device 11 is used as the DC power source 10, the power supply system 100 may also be called an energy storage system or a storage and charging system.

[0034] The power conversion device 20 includes a power conversion circuit 21. The power conversion circuit 21 is a micro inverter capable of bidirectional operation. One end of the power conversion circuit 21 is connected to the energy storage device 11 and the photovoltaic power generation device 12. The energy storage device 11 includes a chargeable and dischargeable energy storage battery. The other end of the power conversion circuit 21 is connected to a common coupling point 30 (abbreviated as PCC). The common coupling point 30 can be used to connect the power grid 40 and the AC load 50.

[0035] In the embodiments of this application, please refer to Figure 2 The power conversion circuit 21 is a single-stage isolation topology with a simple structure and few components. Specifically, the power conversion circuit 21 includes a primary bridge circuit 211, a transformer 212, a resonant inductor 213, and a secondary bridge circuit 214. Both the primary bridge circuit 211 and the secondary bridge circuit 214 can adopt a full-bridge structure or a half-bridge structure. Therefore, the power conversion circuit 21 can also be called a dual active bridge (DAB) conversion circuit.

[0036] In the embodiments of the present application, for the convenience of description, Figure 3 The primary bridge circuit 211 shown is a full-bridge structure, and the secondary bridge circuit 214 is a half-bridge structure for exemplary description.

[0037] like Figure 3As shown, the primary bridge circuit 211 includes a first bridge arm 2111 and a second bridge arm 2112 connected in parallel, the first bridge arm 2111 includes a first switch tube Q1 and a second switch tube Q2 connected in series, and the second bridge arm 2112 includes a third switch tube Q3 and a fourth switch tube Q4 connected in series. The midpoint of the first bridge arm 2111 and the midpoint of the second bridge arm 2112 together constitute the first end of the primary bridge circuit 211, and the first end of the primary bridge circuit 211 is connected to the primary side of the transformer 212. The two ends of the first bridge arm 2111 and the two ends of the second bridge arm 2112 constitute the second end of the primary bridge circuit 211, and the second end of the primary bridge circuit 211 is used to connect the DC power supply 10 or the DC load.

[0038] The secondary bridge circuit 214 includes a third bridge arm 2141 and a fourth bridge arm 2142 connected in parallel. The third bridge arm 2141 includes a fifth switch tube Q5, a sixth switch tube Q6, a seventh switch tube Q7 and an eighth switch tube Q8 connected in series in sequence, wherein the fifth switch tube Q5 and the sixth switch tube Q6 are connected back to back, and the seventh switch tube Q7 and the eighth switch tube Q8 are connected back to back. The fourth bridge arm 2142 includes a first capacitor C1 and a second capacitor C2 connected in series. The midpoint of the third bridge arm 2141 and the midpoint of the fourth bridge arm 2142 together constitute the first end of the secondary bridge circuit 214. The first end of the secondary bridge circuit 214 is connected through the resonant inductor 212 ( Figure 3 The second end of the secondary bridge circuit 214 is connected to the secondary side of the transformer 212. The two ends of the third bridge arm 2141 and the two ends of the fourth bridge arm 2142 constitute the second end of the secondary bridge circuit 214. The second end of the secondary bridge circuit 214 is used to connect to the common coupling point, thereby connecting to the AC power supply or the AC load 50. A filtering circuit may be provided between the second end of the secondary bridge circuit 214 and the common coupling point, for example Figure 3 The filter inductor Lf in.

[0039] The first switch tube Q1 to the eighth switch tube Q8 can use corresponding similar switch devices according to actual needs. For the convenience of description, Figure 3 In the example, the first switch tube Q1 to the eighth switch tube Q8 are all MOSFETs. The on-off state of the first switch tube Q1 to the eighth switch tube Q8 can affect the current flow direction and power transmission of the power conversion circuit 21.

[0040] The turns ratio between the secondary side and the primary side of the transformer 212 is n:1. In short, the turns ratio of the transformer 212 is n, where n>1.

[0041] Based on such a design, when the power supply system 100 is working, the energy storage device 11 can be used as a DC power supply 10, and the power conversion circuit 21 can transmit the power provided by the energy storage device 11 to the AC load 50 and / or the power grid 40. Among them, when the power conversion circuit 21 feeds power to the power grid 40, the power grid 40 can be regarded as the AC load 50 at this time. At this time, the power transmission direction of the power conversion circuit 21 is from the primary bridge circuit 211 to the secondary bridge circuit 214, and this process can also be called the forward operation process of the power conversion circuit 21.

[0042] Conversely, the energy storage device 11 can also be used as a DC load, the power grid 40 can be used as an AC power source, and the power conversion circuit 21 can transmit the power provided by the power grid 40 to the energy storage device 11 to charge the energy storage device 11. At this time, the power transmission direction of the power conversion circuit 21 is from the secondary bridge circuit 214 to the primary bridge circuit 211, and this process can also be called the reverse operation process of the power conversion circuit 21.

[0043] In other embodiments, the process of transmitting power from the primary bridge circuit 211 to the secondary bridge circuit 214 may be referred to as a reverse operation process, and the process of transmitting power from the secondary bridge circuit 214 to the primary bridge circuit 211 may be referred to as a forward operation process, which is not specifically limited herein.

[0044] It should be understood that the polarity of the power transmitted by the power conversion circuit 21 in the forward operation state is opposite to the polarity of the power transmitted in the reverse operation state, for example, the polarity of the transmitted power in the forward operation is positive, and the polarity of the transmitted power in the reverse operation is negative.

[0045] In the above process, the primary bridge circuit 211 constitutes a DC / AC conversion circuit. Figure 4 As shown, the first switch tube Q1 and the second switch tube Q2 are turned on at high frequency complementarily, and the third switch tube Q3 and the fourth switch tube Q4 are turned on at high frequency complementarily, and there is a conduction phase difference between the first switch tube Q1 and the third switch tube Q3. The conduction phase difference is also the phase difference between the first bridge arm 2111 and the second bridge arm 2112 of the primary bridge circuit 211, which can be referred to as the internal phase shift angle of the primary bridge circuit 211. . , D1 is the internal phase shift angle The corresponding duty cycle can be referred to as the inward-shifted phase ratio or the inward-shifted phase duty cycle.

[0046] The secondary bridge circuit 214 constitutes an AC / AC conversion circuit. Figure 4 As shown, the fifth switch tube Q5 and the seventh switch tube Q7 are turned on at high frequency and complementarily, and the sixth switch tube Q6 and the eighth switch tube Q8 are constantly turned on. Alternatively, the fifth switch tube Q5 and the seventh switch tube Q7 are constantly turned on, and the sixth switch tube Q6 and the eighth switch tube Q8 are turned on at high frequency and complementarily.

[0047] The transformer 212 plays an isolation and coupling role, and can transfer energy between the primary bridge circuit 211 and the secondary bridge circuit 214 through a magnetic field. The resonant inductor Lk, the first capacitor C1 and the second capacitor C2 constitute a resonant circuit, and the resonant circuit can be used as an energy storage and transmission unit. It should be understood that in some embodiments, the resonant inductor Lk can also be used as the resonant circuit. Alternatively, in other embodiments, the resonant circuit can also include the leakage inductance of the transformer 212.

[0048] Among them, Figure 3 and Figure 4 As shown, the primary side of the transformer 212 can generate a corresponding primary voltage Vp, which is also the voltage on the first end of the primary bridge circuit 211, or the voltage between the midpoint of the first bridge arm 2111 and the midpoint of the second bridge arm 2112 of the primary bridge circuit 211. For the convenience of description, this voltage can be referred to as the bridge arm midpoint voltage of the primary bridge circuit 211.

[0049] The secondary side of the transformer 212 can generate a corresponding secondary side voltage Vs, which is also the voltage on the first end of the secondary side bridge circuit 214, or the voltage between the midpoint of the third bridge arm 2141 and the midpoint of the fourth bridge arm 2142 of the secondary side bridge circuit 214. For the convenience of description, this voltage can be referred to as the bridge arm midpoint voltage of the secondary side bridge circuit 214.

[0050] The waveforms of Vp and Vs are both square waves, and there is a phase difference between them. This phase difference can be referred to as the external phase angle between the primary bridge circuit 211 and the secondary bridge circuit 214. . D2 is the duty cycle corresponding to the outward shift phase angle, which can be referred to as the outward shift phase ratio or the outward shift phase duty cycle.

[0051] The operating direction (or power transmission direction) of the power conversion circuit 21 is related to the external shift phase angle For example, when the power conversion circuit 21 is running forward, Vp is ahead of Vs, so the external phase angle is positive. When the power conversion circuit 21 is running reversely, Vp lags behind Vs, so the external phase angle is negative.

[0052] It should be understood that the bridge arm midpoint voltages Vp and Vs can be decomposed into fundamental wave components and higher harmonic components, where the fundamental wave is the main component. Figure 4 As shown, the fundamental wave of Vp and the fundamental wave of Vs are both sinusoidal waves, and there is a corresponding phase difference between the peak values ​​of the two, which is also equal to the external phase angle A resonant current ixeq flows through the resonant inductor Lk, and the waveform of the resonant current ixeq is a sine wave.

[0053] like Figure 1 As shown, the power conversion device 20 also includes a controller 22. The controller 22 may be a microcontroller unit (MCU), a digital signal processor (DSP) or other control elements or circuits. The controller 22 is connected to the power conversion circuit 21. Specifically, when the power conversion circuit 21 adopts Figure 2 In the circuit shown in FIG. 1 , the controller 22 is connected to the control terminals of the switches in the primary bridge circuit 211 and the secondary bridge circuit 214 to Figure 3 As an example, the controller 22 is specifically connected with Figure 3 The control ends of the first switch tube Q1 to the eighth switch tube Q8 are connected.

[0054] The controller 22 can be used to execute the control method of the power conversion circuit provided in the embodiment of the present application to control the power conversion circuit 21 so that the power conversion circuit 21 is in a forward operation state, or in a reverse operation state, or performs forward and reverse switching.

[0055] Next, based on Figure 2 The structural topology of the power conversion circuit 21 shown in the figure describes in detail the control method of the power conversion circuit in the embodiment of the present application.

[0056] See also Figure 5 , the control method of the power conversion circuit includes: Step S1 : acquiring a real-time DC voltage on the second end of the primary bridge circuit 211 , and a real-time AC voltage and a real-time AC current on the second end of the secondary bridge circuit 214 .

[0057] Among them, the controller 22 can perform voltage sampling on the second end of the primary bridge circuit 211 through the voltage sampling circuit to obtain the real-time DC voltage Vdc, perform voltage sampling on the second end of the secondary bridge circuit 214 through the voltage sampling circuit to obtain the real-time AC voltage Vac, and perform current sampling on the second end of the secondary bridge circuit 214 through the current sampling circuit to obtain the real-time AC current Iac.

[0058] Step S2: Calculate the real-time transmission power of the power conversion circuit 21 according to the real-time AC voltage and the real-time AC current.

[0059] Specifically, the controller 22 may multiply the real-time AC voltage and the real-time AC current to obtain the real-time transmission power.

[0060] Step S3: Decouple and obtain the target internal phase shift angle of the primary bridge circuit 211 according to the real-time transmission power, the preset power transmission direction, the real-time DC voltage and the real-time AC voltage. , and the target external shift phase angle between the primary bridge circuit 211 and the secondary bridge circuit 214 .

[0061] It can be understood that, as mentioned above, the power conversion circuit 21 can realize power transmission between the primary bridge circuit 211 and the secondary bridge circuit 214 by switching on and off the first switch tube Q1 to the eighth switch tube Q8. Therefore, the magnitude of the real-time transmission power and the power transmission direction, the inner phase shift angle of the primary bridge circuit 211, and the outer phase shift angle between the primary bridge circuit 211 and the secondary bridge circuit 214 are related. At the same time, one of the real-time DC voltage on the second end of the primary bridge circuit 211 and the real-time AC voltage on the second end of the secondary bridge circuit 214 is used as the input of the power conversion circuit 21, and the other is used as the output of the power conversion circuit 21. Therefore, the magnitude of the real-time transmission power is also related to the real-time DC voltage and the real-time AC voltage. Therefore, in step S3, the controller 22 can solve the target inner phase shift angle according to the real-time transmission power, the preset power transmission direction, the real-time DC voltage and the real-time AC voltage. and target outward shift phase angle .

[0062] In one embodiment, see Figure 6 , the process of step S3 may include: Step S31: determining the polarity of the real-time transmission power according to the preset power transmission direction.

[0063] Specifically, when the power conversion circuit 21 needs to run forward, the preset power transmission direction can be set from the primary bridge circuit 211 to the secondary bridge circuit 214. At this time, the controller 22 can determine the polarity of the real-time transmission power as the first polarity according to the preset power transmission direction.

[0064] In the case where the power conversion circuit 21 needs to run in reverse, the preset power transmission direction can be set to be from the secondary bridge circuit 214 to the primary bridge circuit 211. At this time, the controller 22 can determine that the polarity of the real-time transmission power is the second polarity according to the preset power transmission direction. The second polarity is opposite to the first polarity. For example, the first polarity can be positive polarity (+), and the second polarity can be negative polarity (-).

[0065] When the power conversion circuit 21 needs to change the operating direction, the preset power transmission direction changes. At this time, the controller 22 can determine the polarity of the real-time transmission power to switch between the first polarity and the second polarity according to the change of the preset power transmission direction.

[0066] For example, when the power conversion circuit 21 needs to switch from forward operation to reverse operation, the preset power transmission direction can be from the primary bridge circuit 211 to the secondary bridge circuit 214, and then switched from the secondary bridge circuit 214 to the primary bridge circuit 211. At this time, the controller 22 can determine that the polarity of the real-time transmission power is switched from the first polarity to the second polarity according to the preset power transmission direction.

[0067] For another example, when the power conversion circuit 21 needs to switch from reverse operation to forward operation, the preset power transmission direction can be from the secondary bridge circuit 214 to the primary bridge circuit 211, or from the primary bridge circuit 211 to the secondary bridge circuit 214. At this time, the controller 22 can determine that the polarity of the real-time transmission power is switched from the second polarity to the first polarity according to the preset power transmission direction.

[0068] Step S32, obtaining a transmission power model of the power conversion circuit 21; the transmission power model is used to indicate the correlation between the real-time transmission power and the real-time DC voltage, the real-time AC voltage, the target inner phase shift angle, and the target outer phase shift angle.

[0069] The controller 22 may analyze the operating characteristics of the power conversion circuit 21 according to the fundamental wave analysis method to establish a transmission power model of the power conversion circuit 21. The transmission power model may be pre-stored in a memory, and the controller 22 may obtain it from the memory. It should be understood that the transmission power models of power conversion circuits 21 of different topologies may be different.

[0070] In some embodiments, the transmission power model can be used to indicate that the real-time transmission power is positively correlated with the real-time DC voltage, the real-time transmission power is positively correlated with the real-time AC voltage, and the real-time transmission power is positively correlated with the target internal phase shift angle. The real-time transmission power is positively correlated with the target external shift phase angle. In addition, the transmission power model is also used to indicate that the real-time transmission power is positively correlated with the turns ratio of the transformer 212, and the real-time transmission power is negatively correlated with the equivalent impedance of the resonant circuit.

[0071] by Figure 3 Taking the circuit shown in FIG. 2 as an example, the transmission power model of the power conversion circuit 21 can be expressed as the following expression: (1) Wherein, P represents the real-time transmission power, n represents the turns ratio of the transformer 212, Vdc represents the real-time DC voltage, Vac represents the real-time AC voltage, represents the equivalent impedance of the resonant circuit, represents the target internal phase shift angle, Indicates the target outward shift phase angle.

[0072] Step S33: according to the real-time DC voltage, the real-time AC voltage and the real-time transmission power with polarity, a target inner phase shift angle and a target outer phase shift angle are obtained by decoupling the transmission power model.

[0073] Specifically, the controller 22 may substitute the real-time DC voltage Vdc, the real-time AC voltage Vac and the real-time transmission power with polarity (ie, +P or -P) into the transmission power model to obtain the target internal phase shift angle. and target outward shift phase angle .

[0074] In the embodiment of the present application, the target internal phase shift angle obtained by decoupling is Within the preset inner phase shift angle range of (0, π), the target inner phase shift angle The corresponding inner phase shift duty cycle is in the range of (0, 0.5). The target outer phase shift angle obtained by decoupling Within the preset external phase angle range of (-π, π), the target external phase angle The corresponding outer phase shift duty cycle is in the range of (-0.5, 0.5).

[0075] Among them, the polarity of the real-time transmission power can determine The polarity of the target determines the external phase angle The first polarity is positive, the second polarity is negative, and the transmission power model is formula (1) for example. According to formula (1), if the real-time transmission power is positive, then The corresponding polarity is positive. Solved If the real-time transmission power is negative, then The corresponding polarity is negative. Solved If the polarity of the real-time transmission power changes, then The polarity of changes accordingly. Solved The polarity also changes accordingly.

[0076] Step S4: controlling the power conversion circuit 21 to transmit power in a preset power transmission direction according to the target inner phase shift angle and the target outer phase shift angle.

[0077] Specifically, the controller 22 can be configured to and target outward shift phase angle Generate a corresponding control signal to the control end of the switch tube in the power conversion circuit 21. Under the control of the control signal, the switch tube in the power conversion circuit 21 is turned on and off accordingly, thereby generating corresponding bridge arm midpoint voltages Vp, Vs and resonant current ixeq, so that power can be transmitted in the preset power transmission direction.

[0078] Further, Figure 3 Take the circuit shown as an example. The control signal of the first switch tube Q1 is represented by S1, the control signal of the second switch tube Q2 is represented by S2, the control signal of the third switch tube Q3 is represented by S3, ... the control signal of the eighth switch tube Q1 is represented by S8. The control signal can be a pulse width modulation PWM control signal.

[0079] Among them, S1 and S2 are complementary, S3 and S4 are complementary, and if Figure 4 As shown, the phase difference between S1 and S3 is equal to the target internal phase shift angle Therefore, under the control of the control signals S1-S4, the first switch tube Q1 and the second switch tube Q2 are complementarily turned on, the third switch tube Q3 and the fourth switch tube Q4 are complementarily turned on, and the conduction phase difference between the first switch tube Q1 and the third switch tube Q3 is equal to the target internal phase shift angle .

[0080] When the real-time AC voltage is in the positive half cycle, S5 and S7 are complementary, and S6 and S8 are kept at a high level. When the real-time AC voltage is in the negative half cycle, S6 and S8 are complementary, and S5 and S7 are kept at a high level. Therefore, under the control of the control signals S5~S8, when the real-time AC voltage is in the positive half cycle, the fifth switch tube Q5 and the seventh switch tube Q7 are controlled to be complementary and turned on, and the sixth switch tube Q6 and the eighth switch tube Q8 are constantly turned on; when the real-time AC voltage is in the negative half cycle, the fifth switch tube Q5 and the seventh switch tube Q7 are controlled to be constantly turned on, and the sixth switch tube Q6 and the eighth switch tube Q8 are controlled to be complementary and turned on.

[0081] Among them, when the target moves outward, the phase angle When the polarity is the first polarity, the power conversion circuit 21 uses the second end of the primary bridge circuit 211 as the input end and the second end of the secondary bridge circuit 214 as the output end, and the power is transmitted from the primary bridge circuit 211 to the secondary bridge circuit 214. Figure 4 As shown, the waveform of the voltage Vp at the first end of the primary bridge circuit 211 is at the target external phase shift angle Leading the waveform of the voltage Vs at the first terminal of the secondary bridge circuit 214 .

[0082] When the target outward phase angle When the power conversion circuit 21 is in the second polarity, the second end of the secondary bridge circuit 214 is used as the input end, and the second end of the primary bridge circuit 211 is used as the output end, and the power is transmitted from the secondary bridge circuit 214 to the primary bridge circuit 211. Accordingly, the waveform of the voltage Vp on the first end of the primary bridge circuit 211 is at the target external phase shift angle The waveform of the voltage Vs at the first end of the secondary bridge circuit 214 lags behind.

[0083] In addition, in order to verify the control effect of the control method of the embodiment of the present application, the embodiment of the present application also carried out a simulation experiment.

[0084] Figure 7 It shows that when the preset power transmission direction is set from the primary bridge circuit 211 to the secondary bridge circuit 214, the controller 22 controls the Figure 3 The simulation waveform of the circuit shown. Figure 8 It shows that when the preset power transmission direction is set from the secondary bridge circuit 214 to the primary bridge circuit 211, the controller 22 controls the Figure 3 The simulation waveform of the circuit shown. Fig. 9 It shows that when the preset power transmission direction is switched from the primary bridge circuit 211 to the secondary bridge circuit 214 to the secondary bridge circuit 214 to the primary bridge circuit 211, the controller 22 controls the power supply 210 through the method of the embodiment of the present application. Figure 3 The simulation waveform of the circuit shown in the figure. It should be understood that Figures 7 to 9 The data of the horizontal and vertical axes shown are only examples and do not constitute any special limitation on the embodiments of the present application.

[0085] from Figure 7 It can be seen that the power conversion circuit 21 can be stably in the forward operation state and transmit power in real time. .from Figure 8 It can be seen that the power conversion circuit 21 can be stably in the reverse operation state and transmit power in real time. .from Fig. 9 It can be seen that the power conversion circuit 21 performs forward and reverse switching at 40ms, switching from the original forward running state to the reverse running state, transmitting power in real time. Changes from greater than 0 to less than 0. It can be seen that the method of the embodiment of the present application can accurately control the operation direction and switching of the operation direction of the power conversion circuit 21, so that the operation state of the power conversion circuit 21 meets expectations.

[0086] Therefore, in summary, the control method, power conversion device and power supply system of the power conversion circuit of the embodiment of the present application utilize the real-time transmission power, preset power transmission direction, real-time DC voltage and real-time AC voltage of the power conversion circuit to decouple the target inner phase shift angle and the target outer phase shift angle, and then control the power conversion circuit to transmit power in the preset power transmission direction according to the target inner phase shift angle and the target outer phase shift angle. Through such a design, the power conversion circuit of the embodiment of the present application can be compatible with forward operation and reverse operation, as well as forward and reverse switching. Based on this, when the DC power supply adopts an energy storage device, the power conversion circuit can operate in both directions to charge and discharge the energy storage device, thereby effectively broadening the application field and scope of the power conversion circuit.

[0087] Moreover, the power conversion circuit in the embodiment of the present application is a single-stage structure, and there is no need to design different control methods for different operating directions. Therefore, the control method, power conversion equipment and power supply system of the power conversion circuit in the embodiment of the present application are simple and easy to implement, with low control complexity and high control efficiency.

[0088] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present application and are not intended to limit it. Although the present application has been described in detail with reference to the preferred embodiments, a person of ordinary skill in the art should understand that the technical solution of the present application may be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present application.

Claims

1. A control method for a power conversion circuit, characterized in that: The power conversion circuit includes a primary bridge circuit, a transformer, a resonant inductor and a secondary bridge circuit, wherein the first end of the primary bridge circuit is connected to the primary side of the transformer, the first end of the secondary bridge circuit is connected to the secondary side of the transformer via the resonant inductor, the second end of the primary bridge circuit is used to connect to a DC power supply or a DC load, and the second end of the secondary bridge circuit is used to connect to an AC power supply or an AC load; the control method includes: Acquire a real-time DC voltage on the second end of the primary bridge circuit, and a real-time AC voltage and a real-time AC current on the second end of the secondary bridge circuit; Calculate the real-time transmission power of the power conversion circuit according to the real-time AC voltage and the real-time AC current; Decoupling to obtain a target inner phase shift angle of the primary bridge circuit and a target outer phase shift angle between the primary bridge circuit and the secondary bridge circuit according to the real-time transmission power, the preset power transmission direction, the real-time DC voltage and the real-time AC voltage; The power conversion circuit is controlled to transmit power in the preset power transmission direction according to the target inner phase shift angle and the target outer phase shift angle.

2. The control method according to claim 1, characterized in that: The decoupling to obtain a target inner phase shift angle of the primary bridge circuit and a target outer phase shift angle between the primary bridge circuit and the secondary bridge circuit according to the real-time transmission power, the preset power transmission direction, the real-time DC voltage and the real-time AC voltage includes: Determining the polarity of the real-time transmission power according to the preset power transmission direction; Acquire a transmission power model of the power conversion circuit; the transmission power model is used to indicate the correlation between the real-time transmission power and the real-time DC voltage, the real-time AC voltage, the target inner phase shift angle, and the target outer phase shift angle; According to the real-time DC voltage, the real-time AC voltage and the real-time transmission power with polarity, the target inner phase shift angle and the target outer phase shift angle are obtained by decoupling the transmission power model.

3. The control method according to claim 2, characterized in that: The determining the polarity of the real-time transmission power according to the preset power transmission direction includes: When the preset power transmission direction is from the primary bridge circuit to the secondary bridge circuit, the real-time transmission power is of the first polarity; accordingly, the target external shift phase angle is of the first polarity; When the preset power transmission direction is from the secondary bridge circuit to the primary bridge circuit, the real-time transmission power is of the second polarity; accordingly, the target external shift phase angle is of the second polarity, which is opposite to the first polarity.

4. The control method according to claim 2, characterized in that: The transmission power model is used to indicate that the real-time transmission power is positively correlated with the real-time DC voltage, the real-time transmission power is positively correlated with the real-time AC voltage, the real-time transmission power is positively correlated with the cosine value of half the target inner phase shift angle, and the real-time transmission power is positively correlated with the sine value of the target outer phase shift angle.

5. The control method according to claim 3, characterized in that: The primary bridge circuit comprises a first bridge arm and a second bridge arm connected in parallel, wherein the midpoint of the first bridge arm and the second bridge arm constitutes the first end of the primary bridge circuit, and the two ends of the first bridge arm and the second bridge arm constitute the second end of the primary bridge circuit; the secondary bridge circuit comprises a third bridge arm and a fourth bridge arm connected in parallel, wherein the midpoint of the third bridge arm and the fourth bridge arm constitutes the first end of the secondary bridge circuit, and the two ends of the third bridge arm and the fourth bridge arm constitute the second end of the secondary bridge circuit; wherein the first bridge arm, the second bridge arm and the third bridge arm all comprise a switch tube, and the fourth bridge arm comprises a capacitor; The transmission power model is also used to indicate that the real-time transmission power is positively correlated with the turns ratio of the transformer, and the real-time transmission power is negatively correlated with the equivalent impedance of the resonant circuit, wherein the resonant circuit at least includes the resonant inductor.

6. The control method according to claim 1, characterized in that: The primary bridge circuit comprises a first bridge arm and a second bridge arm connected in parallel, wherein the midpoint of the first bridge arm and the second bridge arm constitutes the first end of the primary bridge circuit, and the two ends of the first bridge arm and the second bridge arm constitute the second end of the primary bridge circuit; the secondary bridge circuit comprises a third bridge arm and a fourth bridge arm connected in parallel, wherein the midpoint of the third bridge arm and the fourth bridge arm constitutes the first end of the secondary bridge circuit, and the two ends of the third bridge arm and the fourth bridge arm constitute the second end of the secondary bridge circuit; wherein the first bridge arm, the second bridge arm and the third bridge arm all comprise a switch tube, and the fourth bridge arm comprises a capacitor; The controlling the power conversion circuit to transmit power in the preset power transmission direction according to the target inner phase shift angle and the target outer phase shift angle comprises: Controlling the phase difference between the first bridge arm and the second bridge arm in the primary bridge circuit to be equal to the target internal phase shift angle; When the target external phase shift angle is of the first polarity, the voltage waveform at the first end of the primary bridge circuit is controlled to lead the voltage waveform at the first end of the secondary bridge circuit by the target external phase shift angle; or When the target external phase shift angle is of the second polarity, the voltage waveform at the first end of the primary bridge circuit is controlled to lag behind the voltage waveform at the first end of the secondary bridge circuit by the target external phase shift angle.

7. The control method according to claim 6, characterized in that: The first bridge arm includes a first switch tube and a second switch tube connected in series, the second bridge arm includes a third switch tube and a fourth switch tube connected in series, the third bridge arm includes a fifth switch tube, a sixth switch tube, a seventh switch tube and an eighth switch tube connected in series in sequence, and the fourth bridge arm includes a first capacitor and a second capacitor connected in series; The controlling the power conversion circuit to transmit power in the preset power transmission direction according to the target inner phase shift angle and the target outer phase shift angle comprises: Controlling the first switch tube and the second switch tube to be complementary turned on, the third switch tube and the fourth switch tube to be complementary turned on, and the conduction phase difference between the first switch tube and the third switch tube is equal to the target internal phase shift angle; When the real-time AC voltage is in a positive half cycle, the fifth switch tube and the seventh switch tube are controlled to be complementary turned on, and the sixth switch tube and the eighth switch tube are constantly turned on; When the real-time AC voltage is in a negative half cycle, the fifth switch tube and the seventh switch tube are controlled to be constantly turned on, and the sixth switch tube and the eighth switch tube are controlled to be complementarily turned on.

8. The control method according to claim 1 or 2, characterized in that: The target inner phase shift angle is within the range of (0, π), and the target outer phase shift angle is within the range of (-π, π).

9. A power conversion device, characterized in that: The power conversion device comprises a power conversion circuit and a controller, wherein the power conversion circuit comprises a primary bridge circuit, a transformer, a resonant inductor and a secondary bridge circuit, wherein a first end of the primary bridge circuit is connected to a primary side of the transformer, a first end of the secondary bridge circuit is connected to a secondary side of the transformer via a resonant inductor, a second end of the primary bridge circuit is used to connect to a DC power supply or a DC load, and a second end of the secondary bridge circuit is used to connect to an AC power supply or an AC load; The controller is connected to the power conversion circuit, and is used to decouple the target inner phase shift angle of the primary bridge circuit and the target outer phase shift angle between the primary bridge circuit and the secondary bridge circuit according to the real-time transmission power and preset power transmission direction of the power conversion circuit, the real-time DC voltage on the second end of the primary bridge circuit, and the real-time AC voltage on the second end of the secondary bridge circuit, and control the power conversion circuit to transmit power in the preset power transmission direction according to the target inner phase shift angle and the target outer phase shift angle.

10. The power conversion device according to claim 9, characterized in that When the preset power transmission direction is from the primary bridge circuit to the secondary bridge circuit, the target external shift phase angle is a first polarity; When the preset power transmission direction is from the secondary bridge circuit to the primary bridge circuit, the target external shift phase angle is a second polarity; When the preset power transmission direction changes, the polarity of the target external phase shift angle switches between the first polarity and the second polarity, and the first polarity is opposite to the second polarity.

11. The power conversion device according to claim 9, characterized in that The transmission power model is used to indicate that the real-time transmission power is positively correlated with the real-time DC voltage, the real-time transmission power is positively correlated with the real-time AC voltage, the real-time transmission power is positively correlated with the cosine value of half the target inner phase shift angle, and the real-time transmission power is positively correlated with the sine value of the target outer phase shift angle.

12. A power supply system, characterized in that: The power supply system comprises: a DC power supply and a power conversion device as described in any one of claims 9 to 11, the DC power supply is connected to the second end of the primary bridge circuit, the second end of the secondary bridge circuit is connected to a common coupling point, the DC power supply comprises at least one of an energy storage device and a photovoltaic power generation device, and the common coupling point is used to connect at least one of a power grid and an AC load.

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