A power converter, control method, and related devices

Abstract

This application discloses a power converter, a control method, and related devices. The power converter includes a controller, a DC / DC circuit, a decoupling capacitor, and a three-phase power conversion circuit. Each phase of the three-phase power conversion circuit includes a four-switch Buck-Boost circuit. The DC side of the three-phase power conversion circuit is connected to a DC source, and the AC side is connected to a load in a star configuration. The first and second terminals of the DC / DC circuit are connected to the positive terminal of the DC source and the neutral point of the load, respectively. The third terminal of the DC / DC circuit is used to connect to the negative terminal of the DC source. The first terminal of the decoupling capacitor is connected to the second output terminal of the DC / DC circuit, and the second terminal of the decoupling capacitor is connected to the negative terminal of the DC source. The controller controls the output voltage of the DC / DC circuit so that the second harmonic power on the decoupling capacitor has the same amplitude but opposite phase to the second harmonic power on the AC side of the power converter, thereby suppressing the second harmonic power of the output power.

Description

Technical Field

[0001] This application relates to the field of power electronics technology, specifically to a power converter, control method, and related devices. Background Technology

[0002] Currently, in the industrial and commercial sectors, voltage conversion generally adopts a two-stage topology, which includes a first-stage DC / DC circuit and a second-stage DC / AC circuit. The hardware structure of the two-stage topology is relatively complex, and the control needs to take into account the control objectives of both stages. The software control is also complex. Moreover, there are losses in the power conversion of each stage in the two-stage topology. Therefore, the efficiency of the two-stage topology is relatively low. Summary of the Invention

[0003] In view of this, this application provides a power converter, control method and related apparatus that can improve power conversion efficiency and suppress double-frequency power in the output power of the power converter.

[0004] This application provides a power converter, including: a controller, a DC / DC circuit, a decoupling capacitor, and a three-phase power conversion circuit. Each phase of the three-phase power conversion circuit includes a four-switch Buck-Boost circuit. The DC side of the three-phase power conversion circuit is used to connect to a DC source, and the AC side of the three-phase power conversion circuit is used to connect to a load, wherein the load is connected in a star configuration.

[0005] The first terminal of the DC / DC circuit is used to connect to the positive terminal of the DC source, the second terminal of the DC / DC circuit is used to connect to the neutral point of the load, and the third terminal of the DC / DC circuit is used to connect to the negative terminal of the DC source; the first terminal of the decoupling capacitor is connected to the second terminal of the DC / DC circuit, and the second terminal of the decoupling capacitor is used to connect to the negative terminal of the DC source.

[0006] The controller is used to control the output voltage of the DC / DC circuit so that the second harmonic power on the decoupling capacitor has the same amplitude but opposite phase to the second harmonic power on the AC side of the power converter.

[0007] One possible implementation is that the controller is configured to control the amplitude of the second harmonic voltage component of the DC / DC circuit based on the amplitude of the second harmonic power on the AC side and a given second harmonic power amplitude.

[0008] One possible implementation is that the controller is configured to obtain a reference value for the amplitude of the second harmonic voltage component of the DC / DC circuit through proportional-integral control based on the amplitude of the second harmonic power on the AC side and a given second harmonic power amplitude.

[0009] One possible implementation is that the given second harmonic power amplitude is zero.

[0010] In one possible implementation, the controller is configured to obtain the phase of the second harmonic voltage component of the DC / DC circuit based on the phase of the second harmonic power on the AC side, wherein the phase of the second harmonic voltage component lags the phase of the second harmonic power on the AC side by 90 degrees.

[0011] In one possible implementation, the controller is further configured to control the DC voltage of the DC / DC circuit to be equal to the bias voltage, and the DC voltage of the DC / DC circuit to be greater than or equal to the phase voltage amplitude on the AC side of the power converter.

[0012] One possible implementation is that the DC / DC circuit is one of a boost circuit, a buck circuit, or a buck-boost circuit.

[0013] This application provides a control method for a power converter, comprising: a DC / DC circuit, a decoupling capacitor, and a three-phase power conversion circuit, wherein each phase of the three-phase power conversion circuit includes a four-switch Buck-Boost circuit; the DC side of the three-phase power conversion circuit is used to connect to a DC source, and the AC side of the three-phase power conversion circuit is used to connect to a load, the load being star-connected; a first terminal of the DC / DC circuit is used to connect to the positive terminal of the DC source, a second terminal of the DC / DC circuit is used to connect to the neutral point of the load, and a third terminal of the DC / DC circuit is used to connect to the negative terminal of the DC source; a first terminal of the decoupling capacitor is connected to the second terminal of the DC / DC circuit, and a second terminal of the decoupling capacitor is connected to the negative terminal of the DC source;

[0014] The control method includes:

[0015] Obtain the amplitude and phase of the second harmonic power on the AC side of the power converter;

[0016] The output voltage of the DC / DC circuit is controlled so that the second harmonic power on the decoupling capacitor has the same amplitude but opposite phase to the second harmonic power on the AC side of the power converter.

[0017] One possible implementation involves controlling the output voltage of the DC / DC circuit, including:

[0018] The amplitude of the second harmonic voltage component of the DC / DC circuit is controlled based on the amplitude of the second harmonic power on the AC side and the given amplitude of the second harmonic power.

[0019] One possible implementation involves controlling the amplitude of the second harmonic voltage component of the DC / DC circuit based on the amplitude of the second harmonic power on the AC side and a given second harmonic power amplitude, including:

[0020] The amplitude reference value of the second harmonic voltage component of the DC / DC circuit is obtained by proportional-integral control based on the amplitude of the second harmonic power on the AC side and the given second harmonic power amplitude.

[0021] One possible implementation is that the given second harmonic power amplitude is zero.

[0022] One possible implementation involves controlling the output voltage of the DC / DC circuit so that the second harmonic power of the decoupling capacitor is out of phase with the second harmonic power on the AC side of the power converter, including:

[0023] The phase of the second harmonic voltage component of the DC / DC circuit is obtained based on the phase of the second harmonic power on the AC side. The phase of the second harmonic voltage component lags the phase of the second harmonic power on the AC side by 90 degrees. The direction of the second harmonic power on the AC side is opposite to the direction of the second harmonic power of the decoupling capacitor, so that the second harmonic power of the decoupling capacitor is opposite to the phase of the second harmonic power on the AC side of the power converter.

[0024] Another possible implementation includes:

[0025] The DC voltage of the DC / DC circuit is controlled to be equal to the bias voltage, and the DC voltage of the DC / DC circuit is greater than or equal to the phase voltage amplitude on the AC side of the power converter.

[0026] This application also provides a control device, including a processor and a memory, wherein the memory is used to store programs, instructions or code, and the processor is used to execute the programs, instructions or code in the memory to perform the control method described above.

[0027] This application also provides a computer-readable storage medium storing a computer program, which is loaded by a processor to execute the control method described above.

[0028] In this embodiment, to suppress the second harmonic power on the DC side, a DC / DC circuit is added to the power converter. The first terminal of the DC / DC circuit is connected to the positive terminal of the DC source, the second terminal is connected to the neutral point of the AC side of the power converter, and the third terminal is connected to the negative terminal of the DC source. The output voltage of the DC / DC circuit is controlled so that the second harmonic power of the decoupling capacitor has the same amplitude but opposite phase to the second harmonic power of the AC side of the power converter. This transfers the second harmonic power fluctuation on the AC side to the decoupling capacitor, thereby preventing the energy storage battery on the DC side from bearing the second harmonic power, thus reducing the temperature rise of the energy storage battery and improving its lifespan. Attached Figure Description

[0029] Figure 1 A schematic diagram of a power converter provided in an embodiment of this application;

[0030] Figure 2 A schematic diagram of a power converter in a three-phase four-wire system provided for embodiments of this application;

[0031] Figure 3 A schematic diagram of a power converter with DC / DC circuitry provided in an embodiment of this application;

[0032] Figure 4 A schematic diagram of a boost circuit provided in an embodiment of this application;

[0033] Figure 5 A schematic diagram of a step-down circuit provided in an embodiment of this application;

[0034] Figure 6 A control principle diagram of a DC / DC circuit provided in the embodiments of this application;

[0035] Figure 7 This application provides a schematic diagram of the voltage range of a decoupling capacitor;

[0036] Figure 8 A flowchart illustrating a control method for a power converter provided in an embodiment of this application;

[0037] Figure 9 This is a schematic diagram of a control device provided in an embodiment of this application. Detailed Implementation

[0038] To reduce hardware complexity, simplify software control, and improve power conversion efficiency, this application provides a power converter. For example, the power converter can be applied in industrial and commercial energy storage fields or DC grid-connected scenarios. The AC side can be connected to a three-phase power grid or a three-phase load, and the DC side can be connected to a DC source, which can be a photovoltaic or energy storage battery, etc.

[0039] To enable those skilled in the art to understand and implement the technical solutions provided in the embodiments of this application, the architecture of the power converter will be described below in conjunction with the accompanying drawings.

[0040] See Figure 1 This figure is a schematic diagram of a power converter provided in an embodiment of this application.

[0041] The power converter includes a three-phase four-switch Buck-Boost circuit. The first terminals of the three-phase four-switch Buck-Boost circuit are connected in parallel to a DC source. The second terminals of each three-phase four-switch Buck-Boost circuit are independent and connected to the three AC phases of the power converter respectively. The input voltage of the DC source is denoted by Uin. The AC side of the power converter is connected to the power grid via a grid-connected switch K2. The power grid is a three-phase grid, consisting of phases A, B, and C, with three-phase voltages ua, ub, and uc, respectively. ua, ub, and uc all represent the phase voltages of the power grid. Specifically, the first terminal of the grid-connected switch K2 is connected to the second terminal of a filter inductor (unlabeled), and the first terminal of the filter inductor is connected to the output terminals of the Buck-Boost circuit, with the three phases corresponding to output terminals a, b, and c respectively.

[0042] The first Buck-Boost circuit includes a first switch S1, a second switch S2, a first inductor L1, a third switch S3, and a fourth switch S4. The first switch S1 and the second switch S2 are connected in series to form the first bridge arm, and the third switch S3 and the fourth switch S4 are connected in series to form the second bridge arm. The first end of the first inductor L1 is connected to the midpoint of the first bridge arm, and the second end of the first inductor L1 is connected to the midpoint of the second bridge arm. The first end of the second bridge arm serves as the output terminal a of the power conversion circuit, and the second end of the second bridge arm is connected to the negative terminal m of the DC source. The two ends of the AC-side capacitor Cfa are connected to the first end of the second bridge arm and the negative terminal m of the DC source, respectively.

[0043] The second Buck-Boost circuit includes a fifth switch S5, a sixth switch S6, a second inductor L2, a seventh switch S7, and an eighth switch S8. Switches S5 and S6 are connected in series to form the third bridge arm, and switches S7 and S8 are connected in series to form the fourth bridge arm. The first terminal of the second inductor L2 is connected to the midpoint of the third bridge arm, and the second terminal of the second inductor L2 is connected to the midpoint of the fourth bridge arm. The first terminal of the fourth bridge arm serves as the output terminal b of the power conversion circuit, and the second terminal of the fourth bridge arm is connected to the negative terminal m of the DC source. The two ends of the AC-side capacitor Cfb are connected to the first terminal of the fourth bridge arm and the negative terminal m of the DC source, respectively.

[0044] The third Buck-Boost circuit includes a ninth switch S9, a tenth switch S10, a third inductor L3, an eleventh switch S11, and a twelfth switch S12. Switches S9 and S10 are connected in series to form the fifth bridge arm, and switches S11 and S12 are connected in series to form the sixth bridge arm. The first terminal of the third inductor L3 is connected to the midpoint of the fifth bridge arm, and the second terminal of the third inductor L3 is connected to the midpoint of the sixth bridge arm. The first terminal of the sixth bridge arm serves as the output terminal c of the power conversion circuit, and the second terminal of the sixth bridge arm is connected to the negative terminal m of the DC source. The two ends of the AC-side capacitor Cfc are connected to the first terminal of the sixth bridge arm and the negative terminal m of the DC source, respectively.

[0045] The three-phase output terminals a, b, and c are connected to the negative terminal m of the DC source via corresponding AC-side capacitors Cfa, Cfb, and Cfc, respectively.

[0046] In off-grid mode, the AC side of the three-phase power converter circuit is suitable for connecting a load Rd, which is connected in a star configuration. Specifically, the three-phase output terminals a, b, and c are connected to the first terminal of the first switch K1 via corresponding filter inductors, and the second terminal of the first switch K1 is connected to the neutral point N via the load Rd. The load Rd represents the load connected when the power converter is off-grid. In grid-connected mode, the AC side of the three-phase power converter circuit is suitable for connecting to the power grid, which is connected in a star configuration. Specifically, the three-phase output terminals a, b, and c are connected to the first terminal of the second switch K2 via corresponding filter inductors, and the second terminal of the second switch K2 is connected to the three-phase power grid.

[0047] In a three-phase three-wire system, the voltage of the three-phase power grid relative to the negative terminal m of the DC source is the DC bias voltage Uoff.

[0048] When the power converter is off-grid, K2 is open and K1 is closed, operating in a three-phase four-wire system.

[0049] When the power converter is connected to the grid, K2 is closed and K1 is open, operating in a three-phase three-wire system.

[0050] See Figure 2 The figure is a schematic diagram of a power converter in a three-phase four-wire system provided in an embodiment of this application.

[0051] In a three-phase four-wire system, the power converter is considered a voltage source carrying a three-phase load. When the three-phase load is unbalanced, the output power of the power converter includes the superposition of DC power and second harmonic power. Second harmonic power is AC power. For example, for an AC power grid with a power frequency of 50Hz, the second harmonic is 100Hz. According to the law of power conservation, the second harmonic power will be provided by the DC source on the DC side. For example, when the DC source is an energy storage battery, the second harmonic power caused by the unbalanced three-phase load will lead to frequent charging and discharging of the energy storage battery, resulting in a temperature rise. If the battery operates in this charging and discharging state for a long time, its lifespan will be reduced. Therefore, it is necessary to suppress the second harmonic power on the DC side. However, under the condition of ensuring a symmetrical three-phase voltage output from the power converter, it is impossible to suppress the unbalanced current.

[0052] In order to suppress the second harmonic power on the DC side, this embodiment adds a DC / DC circuit and a decoupling capacitor. The output voltage of the DC / DC circuit is controlled so that the second harmonic power of the decoupling capacitor has the same amplitude but opposite phase as the second harmonic power on the AC side of the power converter. This transfers the second harmonic power fluctuation on the AC side to the decoupling capacitor, thereby avoiding the energy storage battery on the DC side from bearing the second harmonic power. This reduces the number of charge and discharge cycles of the energy storage battery, reduces the temperature rise of the energy storage battery, and improves the lifespan of the energy storage battery.

[0053] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the embodiments of this application will be further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0054] See Figure 3 The figure is a schematic diagram of a power converter with DC / DC circuitry provided in an embodiment of this application.

[0055] The power converter provided in this application embodiment includes: a controller (not shown in the figure), a DC / DC circuit 100, and a three-phase four-switch Buck-Boost circuit. For details of the three-phase four-switch Buck-Boost circuit, please refer to [link to relevant documentation]. Figure 1 The description will not be repeated here. Figure 3 The following is an introduction using a three-phase four-switch Buck-Boost circuit operating in a three-phase four-wire system as an example. Due to the three-phase four-wire system, there will be a problem of double frequency power when the three-phase load is unbalanced. This problem is caused by the three-phase load imbalance.

[0056] The DC side of the three-phase power conversion circuit is used to connect to a DC source, and the AC side is used to connect to the load, which is connected in a star configuration.

[0057] The first terminal of the DC / DC circuit 100 is connected to the positive terminal p of the DC source, the second terminal of the DC / DC circuit 100 is connected to the neutral point N of the load, and the third terminal of the DC / DC circuit 100 is connected to the negative terminal m of the DC source. It should be understood that the power converter provided in this embodiment further includes a decoupling capacitor Cdq, the first terminal of which is connected to the second terminal of the DC / DC circuit 100, and the second terminal of which is connected to the negative terminal m of the DC source.

[0058] The power converter provided in this application does not specifically limit the topology of the DC / DC circuit. For example, the DC / DC circuit can be a boost circuit, a buck circuit, or a buck-boost circuit. Specifically, the boost circuit can be a Boost circuit, the buck circuit can be a Buck voltage circuit, and the buck-boost circuit can be a BuckBoost circuit, etc. Those skilled in the art can select the topology of the DC / DC circuit according to actual needs.

[0059] The controller is used to control the output of the DC / DC circuit to produce a second-harmonic power with the same amplitude but opposite phase to the second-harmonic power on the AC side of the power converter.

[0060] It should be understood that the AC-side second harmonic power of the power converter can be obtained from the AC-side voltage and current. Both the AC-side voltage and current can be detected in real time.

[0061] In this embodiment, to minimize frequent charging and discharging of the DC source, it is necessary to transfer the AC-side second-harmonic power fluctuations to the decoupling capacitor. To do this, the amplitude and phase of the voltage across the decoupling capacitor are controlled based on the amplitude and phase of the second-harmonic power contained in the detected output power. When the second-harmonic power of the decoupling capacitor has the same amplitude but opposite phase to the second-harmonic power of the AC side of the power converter, the AC-side second-harmonic power fluctuations can be transferred to the decoupling capacitor. This reduces the amount of second-harmonic power the energy storage battery bears, lowers the battery's temperature rise, and extends its lifespan.

[0062] See Figure 4 The figure is a schematic diagram of a boost circuit provided in an embodiment of this application.

[0063] from Figure 4 As can be seen, the boost circuit includes an inductor Ldq, a first power transistor Q1, and a second power transistor Q2. The first end of the inductor Ldq is connected to the positive terminal p of the DC source, the second end of the inductor Ldq is connected to the neutral point N of the load through the second power transistor Q2, and the second end of the inductor Ldq is connected to the negative terminal m of the DC source through the first power transistor Q1.

[0064] The power converter provided in this application embodiment can control the amplitude and phase of the output voltage of the boost circuit by controlling the operation of Q1 and Q2 in the boost circuit.

[0065] See Figure 5 The figure is a schematic diagram of a step-down circuit provided in an embodiment of this application.

[0066] from Figure 5 As can be seen, the step-down circuit includes an inductor Ldq, a third power transistor Q3, and a fourth power transistor Q4. The first terminal of the third power transistor Q3 is connected to the positive terminal p of the DC source, the second terminal of the third power transistor Q3 is connected to the neutral point N of the AC side of the power converter through the inductor Ldq, and the second terminal of the third power transistor Q3 is connected to the negative terminal m of the DC source through the fourth power transistor Q4.

[0067] The power converter provided in this application embodiment can control the amplitude and phase of the output voltage of the boost circuit by controlling the operation of Q3 and Q4 in the boost circuit.

[0068] The control principle of DC / DC circuits in the embodiments of this application is described in detail below with reference to the accompanying drawings.

[0069] See Figure 6 This figure is a control principle diagram of a DC / DC circuit provided in an embodiment of this application.

[0070] For ease of understanding, the DC / DC circuit provided in this application embodiment controls the output power by controlling the output voltage of the DC / DC circuit, that is, controlling the voltage of the decoupling capacitor.

[0071] The voltage U of the decoupling capacitor dp Represented by the following expression.

[0072]

[0073] Where A0 is the DC voltage component of the decoupling capacitor, A2 is the amplitude of the second harmonic voltage component of the decoupling capacitor, and θ dp ω represents the phase of the second harmonic voltage component. ω is the angular frequency, with the power frequency of 50Hz as an example.

[0074] Instantaneous power P of the decoupling capacitor dp It can be represented as follows.

[0075]

[0076] C dp This indicates the capacitance value of the decoupling capacitor.

[0077] The second harmonic power caused by a three-phase unbalanced load can be expressed as:

[0078]

[0079] Where, p o The output power of the power converter. To output DC power, θ represents the amplitude of the second harmonic power on the AC side. 2ω This is the phase angle of the AC side double-frequency power of the power converter.

[0080] u an u bn u cn These represent the three-phase voltages on the AC side, i an i bn i cn These represent the three-phase currents on the AC side.

[0081] The capacitance value of the decoupling capacitor satisfies the following expression.

[0082]

[0083] According to equation (2), in order to transfer the second harmonic power fluctuation on the AC side to the decoupling capacitor, the DC / DC circuit introduces a fourth harmonic power component, which should be as small as possible. According to equation (4), when the output second harmonic power is constant, the larger A0 is, A2 The smaller the value of A0, the smaller the fourth harmonic power of the decoupling capacitor. Therefore, to achieve a power suppression effect closer to the ideal, the value of A0 is generally larger than that of A2. When the value of A0 is much larger than that of A2, for example, at least 10 times the value of A2, such as 20 times, the fourth harmonic power can be approximately ignored. Therefore, controlling A0, A2, and θ... dp This allows the double-frequency power on the AC side to be transferred to the decoupling capacitor.

[0084] The controller is used to determine the amplitude of the second harmonic power on the AC side. The controller controls the amplitude of the second harmonic voltage component in a DC / DC circuit based on a given second harmonic power amplitude. Ideally, the given second harmonic power amplitude could be set to zero, even if both amplitudes are equal, to achieve maximum transfer. Specifically, the controller is configured to adjust the second harmonic power amplitude based on the AC side amplitude. The amplitude reference value A of the second harmonic voltage component of the DC / DC circuit is obtained by proportional-integral (PI) control, given a second harmonic power amplitude of 0. 2-ref The above refers to the control of the amplitude of the second harmonic power of the decoupling capacitor. The following describes the control of the phase of the second harmonic power of the decoupling capacitor.

[0085] Controller, used to determine the phase θ of the second harmonic power on the AC side. 2ω Obtain the phase of the second harmonic voltage component in the DC / DC circuit. The phase of the second harmonic voltage component lags the phase of the second harmonic power on the AC side by 90 degrees. That is, the phase θ of the second harmonic voltage component. dp =θ 2ω -π / 2. This refers to the controller, specifically used to obtain the phase of the second harmonic voltage component of the DC / DC circuit based on the phase of the second harmonic power on the AC side. The phase of the second harmonic voltage component lags the phase of the second harmonic power on the AC side by 90 degrees. The direction of the second harmonic power on the AC side is opposite to the direction of the second harmonic power of the decoupling capacitor, ensuring that the second harmonic power of the decoupling capacitor is out of phase with the second harmonic power on the AC side of the power converter. Opposite power directions mean one power is positive and the other is negative.

[0086] In addition, for voltage control of the decoupling capacitor, a DC voltage needs to be superimposed on the AC voltage component, i.e., the second harmonic voltage component.

[0087] The theoretical basis of the control principle provided in the embodiments of this application is described below.

[0088] See also Figure 3 , Figure 3 The output voltage satisfies the following formula.

[0089]

[0090] As can be seen from formula (1), the output voltage of the power converter is independent of the DC source voltage and only depends on the DC bias voltage V. off and the voltage U of the decoupling capacitor dp Relevant. From another perspective, Figure 3 The topology can theoretically realize the mains voltage of any DC source voltage.

[0091] To ensure that the output voltage is not distorted and the output voltage amplitude does not decrease, V needs to be... off with U dp Equal to, and greater than or equal to, the phase voltage amplitude. Its voltage operating range is as follows Figure 7 As shown by the solid line with a slope of 1 in the figure, to ensure the safety of the hardware circuit, the voltage of the decoupling capacitor has a maximum limit U. dp-max The voltage across the decoupling capacitor must be less than or equal to the maximum limit U. dp-max .

[0092] Based on the conditions that should be met as described above, the expression for the three-phase voltage on the AC side is as follows, which fundamentally ensures that the output phase voltage is not distorted and does not decrease.

[0093]

[0094] v xn Vm is the phase voltage, and Vm is the phase voltage amplitude. This indicates the phase of the phase voltage.

[0095] Specifically, the controller is also used to determine the reference value A of the DC voltage of the DC / DC circuit. 0-ref To control the DC voltage in a DC / DC circuit and ensure the phase voltage output from the AC side is not distorted, the reference value for the DC voltage needs to take into account the amplitude of the AC side phase voltage. This is because the reference value A for the DC voltage... 0-ref The DC bias voltage at the neutral point is determined; therefore, the reference value of the DC voltage is greater than or equal to the phase voltage amplitude on the AC side of the power converter. For example, in a scenario with 220V AC, to ensure that the voltage is not distorted, it is generally greater than or equal to... At the same time, A 0-ref The value should not be too large. While it is necessary to minimize the capacitance of the decoupling capacitor, it is also necessary to avoid increasing the stress and losses of power devices. Therefore, a compromise can be made in practical applications.

[0096] The power converter provided in this application embodiment can control the amplitude and phase of the second harmonic voltage component of the decoupling capacitor according to the amplitude and phase of the second harmonic power on the AC side, so that the amplitude of the second harmonic power on the decoupling capacitor is the same as the amplitude of the second harmonic power on the AC side, but the phase is opposite. This can effectively transfer the second harmonic power fluctuation on the AC side to the decoupling capacitor, thereby avoiding the energy storage battery from bearing the second harmonic power, reducing the temperature rise of the energy storage battery, and improving the life of the energy storage battery.

[0097] Based on the power converter provided in the above embodiments, this application also provides a control method for the power converter, which will be described in detail below with reference to the accompanying drawings.

[0098] See Figure 8 The figure is a flowchart of a control method for a power converter provided in an embodiment of this application.

[0099] The power converter control method provided in this application includes: a DC / DC circuit, a decoupling capacitor, and a three-phase power conversion circuit. Each phase of the three-phase power conversion circuit includes a four-switch Buck-Boost circuit. The DC side of the three-phase power conversion circuit is used to connect to a DC source, and the AC side of the three-phase power conversion circuit is used to connect to a load, which is connected in a star configuration. The first terminal of the DC / DC circuit is used to connect to the positive terminal of the DC source, the second terminal of the DC / DC circuit is used to connect to the neutral point of the load, and the third terminal of the DC / DC circuit is connected to the negative terminal of the DC source. The first terminal of the decoupling capacitor is connected to the second terminal of the DC / DC circuit, and the second terminal of the decoupling capacitor is connected to the negative terminal of the DC source.

[0100] The control method includes:

[0101] S801: Obtain the amplitude and phase of the AC side second harmonic power of the power converter;

[0102] S802: Controls the output voltage of the DC / DC circuit so that the second harmonic power of the decoupling capacitor has the same amplitude but opposite phase as the second harmonic power of the AC side of the power converter.

[0103] The control method provided in this application aims to transfer the second harmonic power fluctuation on the AC side to the decoupling capacitor by controlling the output voltage of the DC / DC circuit. This ensures that the second harmonic power of the decoupling capacitor has the same amplitude but opposite phase to the second harmonic power on the AC side of the power converter, thereby canceling the second harmonic power applied to the DC side by the AC side. This reduces the number of charge and discharge cycles of the energy storage battery, reduces the temperature rise of the energy storage battery, and improves the lifespan of the energy storage battery.

[0104] One possible implementation involves controlling the output voltage of a DC / DC circuit to make the second harmonic power of the decoupling capacitor the same as the amplitude of the second harmonic power on the AC side of the power converter. This includes controlling the amplitude of the second harmonic voltage component of the DC / DC circuit based on the amplitude of the second harmonic power on the AC side and a given second harmonic power amplitude, so that the second harmonic power of the decoupling capacitor is the same as the amplitude of the second harmonic power on the AC side of the power converter.

[0105] One possible implementation involves controlling the amplitude of the second harmonic voltage component of the DC / DC circuit based on the amplitude of the second harmonic power on the AC side and a given second harmonic power amplitude, including: obtaining a reference value for the amplitude of the second harmonic voltage component of the DC / DC circuit through proportional-integral control based on the amplitude of the second harmonic power on the AC side and the given second harmonic power amplitude.

[0106] One possible implementation is given a second harmonic power amplitude of zero.

[0107] One possible implementation involves controlling the output of the DC / DC circuit to have a second harmonic power that is out of phase with the second harmonic power on the AC side of the power converter. This includes: obtaining the phase of the second harmonic voltage component of the DC / DC circuit based on the phase of the second harmonic power on the AC side; the phase of the second harmonic voltage component lags the phase of the second harmonic power on the AC side by 90 degrees; and the direction of the second harmonic power on the AC side is opposite to the direction of the second harmonic power of the decoupling capacitor, so that the second harmonic power of the decoupling capacitor is out of phase with the second harmonic power on the AC side of the power converter.

[0108] One possible implementation also includes: controlling the DC voltage of the DC / DC circuit to be equal to the bias voltage, and the DC voltage of the DC / DC circuit to be greater than or equal to the phase voltage amplitude on the AC side of the power converter.

[0109] In one possible implementation, see Figure 9 The figure is a schematic diagram of a control device provided in an embodiment of this application.

[0110] The control device may include a memory 1011 and a processor 1012. The processor 1012 may be connected to the power converter and can drive the switches in the various power conversion circuits of the power converter. For example... Figure 9 As shown, the memory can be random access memory (RAM), flash memory, read-only memory (ROM), EPROM, non-volatile read-only memory (Electronic Programmable ROM), registers, hard disks, removable disks, etc.

[0111] The memory 1011 can store computer instructions. When the computer instructions stored in the memory 1011 are executed by the processor 1012, the processor 1012 can be used to execute the control method of the power converter. The memory 1011 can also store data, such as preset ranges, preset thresholds, and other information involved in the above embodiments.

[0112] In the above embodiments, implementation can be achieved, in whole or in part, through software, hardware, firmware, or any combination thereof. When implemented in software, it can be implemented, in whole or in part, as a computer program product. A computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or part of the flow or function according to the embodiments of this application is generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wired (e.g., coaxial cable, fiber optic, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) means. The computer-readable storage medium can be any available medium that a computer can access or a data storage device such as a server or data center that integrates one or more available media. The available medium can be a magnetic medium (e.g., floppy disk, hard disk, magnetic tape) or a semiconductor medium (e.g., solid-state disk (SSD)).

[0113] This application also provides a readable storage medium for storing the methods provided in the above embodiments. Examples include random access memory (RAM), flash memory, read-only memory (ROM), EPROM, non-volatile read-only memory (EPROM), registers, hard disks, removable disks, or any other form of storage medium in the art.

[0114] It should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. Regarding the methods disclosed in the embodiments, since they correspond to the product embodiments disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to in the description of the product embodiments.

[0115] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. 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 this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A power converter, characterized in that, include: The system includes a controller, a DC / DC circuit, a decoupling capacitor, and a three-phase power conversion circuit, each phase of which includes a four-switch Buck-Boost circuit. The DC side of the three-phase power conversion circuit is used to connect to a DC source, and the AC side is used to connect to a load, which is connected in a star configuration. The first terminal of the DC / DC circuit is used to connect to the positive terminal of the DC source, the second terminal of the DC / DC circuit is used to connect to the neutral point of the load, and the third terminal of the DC / DC circuit is used to connect to the negative terminal of the DC source; the first terminal of the decoupling capacitor is connected to the second terminal of the DC / DC circuit, and the second terminal of the decoupling capacitor is used to connect to the negative terminal of the DC source. The controller is used to control the output voltage of the DC / DC circuit so that the second harmonic power on the decoupling capacitor has the same amplitude but opposite phase to the second harmonic power on the AC side of the power converter.

2. The power converter according to claim 1, characterized in that, The controller is used to control the amplitude of the second harmonic voltage component of the DC / DC circuit based on the amplitude of the second harmonic power on the AC side and a given second harmonic power amplitude.

3. The power converter according to claim 2, characterized in that, The controller is used to obtain a reference value for the amplitude of the second harmonic voltage component of the DC / DC circuit through proportional-integral control based on the amplitude of the second harmonic power on the AC side and a given second harmonic power amplitude.

4. The power converter according to claim 3, characterized in that, The given second harmonic power amplitude is zero.

5. The power converter according to any one of claims 1-4, characterized in that, The controller is configured to obtain the phase of the second harmonic voltage component of the DC / DC circuit based on the phase of the second harmonic power on the AC side, wherein the phase of the second harmonic voltage component lags the phase of the second harmonic power on the AC side by 90 degrees.

6. The power converter according to any one of claims 1-5, characterized in that, The controller is also configured to control the DC voltage of the DC / DC circuit to be equal to the bias voltage, and the DC voltage of the DC / DC circuit to be greater than or equal to the phase voltage amplitude of the AC side of the power converter.

7. The power converter according to any one of claims 1-6, characterized in that, The DC / DC circuit is one of a boost circuit, a buck circuit, or a buck-boost circuit.

8. A control method for a power converter, characterized in that, include: The system comprises a DC / DC circuit, a decoupling capacitor, and a three-phase power conversion circuit. Each phase of the three-phase power conversion circuit includes a four-switch Buck-Boost circuit. The DC side of the three-phase power conversion circuit is used to connect to a DC source, and the AC side is used to connect to a load, which is connected in a star configuration. The first terminal of the DC / DC circuit is connected to the positive terminal of the DC source, the second terminal is connected to the neutral point of the load, and the third terminal is connected to the negative terminal of the DC source. The first terminal of the decoupling capacitor is connected to the second terminal of the DC / DC circuit, and the second terminal is connected to the negative terminal of the DC source. The control method includes: Obtain the amplitude and phase of the second harmonic power on the AC side of the power converter; The output voltage of the DC / DC circuit is controlled so that the second harmonic power on the decoupling capacitor has the same amplitude but opposite phase to the second harmonic power on the AC side of the power converter.

9. The control method according to claim 8, characterized in that, Controlling the output voltage of the DC / DC circuit includes: The amplitude of the second harmonic voltage component of the DC / DC circuit is controlled based on the amplitude of the second harmonic power on the AC side and the given amplitude of the second harmonic power.

10. The control method according to claim 9, characterized in that, The amplitude of the second harmonic voltage component of the DC / DC circuit is controlled based on the amplitude of the second harmonic power on the AC side and a given second harmonic power amplitude, including: The amplitude reference value of the second harmonic voltage component of the DC / DC circuit is obtained by proportional-integral control based on the amplitude of the second harmonic power on the AC side and the given second harmonic power amplitude.

11. The control method according to claim 10, characterized in that, The given second harmonic power amplitude is zero.

12. The control method according to any one of claims 8-11, characterized in that, Controlling the output voltage of the DC / DC circuit so that the second harmonic power of the decoupling capacitor is out of phase with the second harmonic power of the AC side of the power converter includes: The phase of the second harmonic voltage component of the DC / DC circuit is obtained based on the phase of the second harmonic power on the AC side. The phase of the second harmonic voltage component lags the phase of the second harmonic power on the AC side by 90 degrees. The direction of the second harmonic power on the AC side is opposite to the direction of the second harmonic power of the decoupling capacitor, so that the second harmonic power of the decoupling capacitor is opposite to the phase of the second harmonic power on the AC side of the power converter.

13. The control method according to any one of claims 8-12, characterized in that, Also includes: The DC voltage of the DC / DC circuit is controlled to be equal to the bias voltage, and the DC voltage of the DC / DC circuit is greater than or equal to the phase voltage amplitude on the AC side of the power converter.

14. A control device, characterized in that, It includes a processor and a memory, the memory being used to store programs, instructions, or code, and the processor being used to execute the programs, instructions, or code in the memory to perform the control method as described in any one of claims 8-13.

15. A computer-readable storage medium, characterized in that, The system contains a computer program that is loaded by a processor to execute the control method as described in any one of claims 8-13.

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