Two-stage converter and control method
By adjusting the power variation of the DC/DC converter circuit according to the DC bus electrical parameters and controlling the operation of the switching transistors of the AC/DC converter circuit, the problem of DC bus voltage fluctuation in the two-stage converter is solved, and a low-cost, high-energy-density converter design is realized.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-01-13
- Publication Date
- 2026-04-07
AI Technical Summary
In two-stage converters, sudden power command changes cause DC bus voltage fluctuations. Existing technologies require increasing the DC bus capacitance to suppress these fluctuations, resulting in high costs and low energy density.
The controller determines the power change of the DC/DC converter circuit based on the DC bus electrical parameters, controls the operation of the AC/DC converter circuit switching transistors, and adopts a new power command feedforward value to suppress DC bus voltage fluctuations and avoid increasing the DC bus capacitance value.
This technology enables the suppression of voltage fluctuations without increasing the DC bus capacitance, thereby reducing converter costs and increasing energy density.
Smart Images
Figure CN121813825A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of power electronics technology, specifically to a two-stage converter and its control method. Background Technology
[0002] A two-stage converter can include a single-stage AC / DC conversion circuit and a single-stage DC / DC conversion circuit. The AC / DC conversion circuit controls the DC bus voltage and can employ a control strategy of an outer voltage loop and an inner current loop. The DC / DC conversion circuit controls the charging and discharging power of the battery clusters and can employ a control strategy of an outer power loop and an inner current loop.
[0003] In scenarios such as charge / discharge conversion testing, the power command of a two-stage converter may abruptly change. Since the power command is first sent to the AC / DC conversion circuit and then to the DC / DC conversion circuit, if the power command in the DC / DC conversion circuit has not yet changed when the AC / DC conversion circuit feeds the power command forward to the current loop, it will cause voltage fluctuations on the DC bus and abnormalities in the DC voltage control loop. To suppress DC bus voltage fluctuations, the capacitance of the DC bus capacitor needs to be increased, which makes the converter cost high and its energy density low. Summary of the Invention
[0004] In view of this, this application provides a two-stage converter and control method, which can determine the change in power of the DC / DC conversion circuit by the derivative of the DC bus current, and then make the AC / DC circuit adopt a new power command feedforward value, suppressing the voltage fluctuation of the DC bus without increasing the capacitance of the DC bus. The converter has low cost and high energy density.
[0005] To solve the above problems, the technical solution provided in this application is as follows: In a first aspect of this application, a two-stage converter is provided, comprising: a controller, an AC / DC conversion circuit, and N DC / DC conversion circuits, where N is an integer greater than or equal to 1; The first terminal of the AC / DC converter circuit is used to connect to the AC power grid. The second terminal of the AC / DC converter circuit and the first terminals of the N DC / DC converter circuits are all connected to the DC bus. The second terminal of each DC / DC converter circuit is used to connect to the corresponding battery cluster. The controller is configured to determine the power changes of the DC / DC converter circuit based on the electrical parameters of the DC bus; when the current power command differs from the previous power command, if the power of the DC / DC converter circuit does not change, the controller controls the operation of the switching transistors in the AC / DC converter circuit according to the previous power command; if the power of the DC / DC converter circuit changes, the controller controls the operation of the switching transistors in the AC / DC converter circuit according to the current power command to suppress voltage fluctuations on the DC bus.
[0006] One possible implementation involves the controller being configured to determine power changes in the DC / DC converter circuit based on electrical parameters of the DC bus, including: The controller is configured to determine a change in the power of the DC / DC converter circuit based on either the absolute value of the rate of change of the DC bus current being greater than a current threshold or the absolute value of the rate of change of the DC bus voltage being greater than a voltage threshold.
[0007] In one possible implementation, the controller is also configured to control the operation of the switching transistors in the AC / DC conversion circuit according to a reverse current command in the event of a DC / DC conversion circuit failure, so as to suppress voltage fluctuations on the DC bus. The reverse current command is obtained from the previous power command and the DC bus voltage through a negative proportional-integral regulator.
[0008] In one possible implementation, the controller is also configured to control the operation of the switching transistors in the AC / DC conversion circuit according to voltage compensation commands. The value of the voltage compensation command is the difference between the current command voltage corresponding to the current power command and the previous command voltage corresponding to the previous power command.
[0009] In one possible implementation, the converter further includes a DC bus capacitor connected between the DC positive bus and the DC negative bus; The controller is configured to obtain the current command voltage based on the current power command, the power response time of the DC / DC converter circuit, and the DC bus capacitance; and to obtain the previous command voltage based on the previous power command, the power response time of the DC / DC converter circuit, and the DC bus capacitance.
[0010] In a second aspect of this application, a control method for a two-stage converter is provided. The two-stage converter includes: a controller, an AC / DC conversion circuit, and N DC / DC conversion circuits, where N is an integer greater than or equal to 1. The first terminal of the AC / DC conversion circuit is used to connect to the AC power grid, and the second terminal of the AC / DC conversion circuit and the first terminals of the N DC / DC conversion circuits are all connected to a DC bus. The second terminal of each DC / DC conversion circuit is used to connect to the corresponding battery cluster. The control method includes: determining the power change of the DC / DC converter circuit based on the electrical parameters of the DC bus; when the current power command differs from the previous power command, if the power of the DC / DC converter circuit does not change, controlling the switching transistors in the AC / DC converter circuit according to the previous power command; and if the power of the DC / DC converter circuit changes, controlling the switching transistors in the AC / DC converter circuit according to the current power command to suppress voltage fluctuations on the DC bus.
[0011] One possible implementation involves determining the power change of the DC / DC converter circuit based on the electrical parameters of the DC bus by: determining the power change of the DC / DC converter circuit based on the absolute value of the rate of change of the DC bus current being greater than a current threshold, or based on the absolute value of the rate of change of the DC bus voltage being greater than a voltage threshold.
[0012] In one possible implementation, the control method further includes: when the DC / DC converter circuit fails, controlling the operation of the switching transistor in the AC / DC converter circuit according to the reverse current command to suppress voltage fluctuations on the DC bus; The reverse current command is obtained from the previous power command and the DC bus voltage through a negative proportional-integral regulator.
[0013] In one possible implementation, the control method further includes controlling the operation of the switching transistors in the AC / DC conversion circuit according to a voltage compensation command; The value of the voltage compensation command is the difference between the current command voltage corresponding to the current power command and the previous command voltage corresponding to the previous power command.
[0014] In one possible implementation, the converter further includes a DC bus capacitor connected between the DC positive bus and the DC negative bus; The control method includes: obtaining the current command voltage based on the current power command, the power response time of the DC / DC converter circuit, and the DC bus capacitance; and obtaining the previous command voltage based on the previous power command, the power response time of the DC / DC converter circuit, and the DC bus capacitance.
[0015] The two-stage converter provided in this application has a controller configured to, when the current power command differs from the previous power command and the power of the DC / DC converter circuit remains unchanged, control the switching transistors in the AC / DC converter circuit according to the previous power command; when the power of the DC / DC converter circuit changes, control the switching transistors in the AC / DC converter circuit according to the current power command. Since the AC / DC converter circuit only uses the current power command to control the switching transistors after determining that the power of the DC / DC converter circuit has changed, voltage changes on the DC bus can be promptly absorbed by the DC / DC converter circuit, achieving the effect of suppressing DC bus voltage fluctuations and ensuring the safe and stable operation of the converter. Because the converter provided in this application can suppress DC bus voltage fluctuations without increasing the capacitance of the DC bus capacitor, the converter has low cost and high energy density. Attached Figure Description
[0016] Figure 1 A schematic diagram of a two-stage converter provided in an embodiment of this application; Figure 2 A control block diagram of an AC / DC conversion circuit provided in an embodiment of this application; Figure 3 A control block diagram of another AC / DC conversion circuit provided in the embodiments of this application; Figure 4 A control block diagram of another AC / DC conversion circuit provided in the embodiments of this application; Figure 5 This is a schematic diagram of a converter control method provided in an embodiment of this application. Detailed Implementation
[0017] 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.
[0018] See Figure 1 The figure is a schematic diagram of a two-stage converter provided in an embodiment of this application.
[0019] The two-stage converter provided in this application includes a controller 10, an AC / DC conversion circuit 20, and N DC / DC conversion circuits. The N DC / DC conversion circuits include a first DC / DC conversion circuit 301, a second DC / DC conversion circuit 302, and so on up to the Nth DC / DC conversion circuit 30N, where N is an integer greater than or equal to 1. The N DC / DC conversion circuits can achieve independent control of the battery clusters, reducing the generation of circulating currents between battery clusters.
[0020] The first terminal of AC / DC converter 20 is used to connect to a three-phase AC power grid. The second terminal of AC / DC converter 20 and the first terminals of N DC / DC converter circuits are all connected to a DC bus. The second terminal of each DC / DC converter circuit is used to connect to the corresponding battery cluster. For example, the second terminal of the first DC / DC converter 301 is used to connect to the first battery cluster BT1, the second terminal of the second DC / DC converter 302 is used to connect to the second battery cluster BT2, and so on up to the second terminal of the Nth DC / DC converter 30N being used to connect to the Nth battery cluster BTN.
[0021] Under steady-state operation, the two-stage converter can exchange energy between the grid and the battery pack at a constant power. When the converter is in charging mode, the AC / DC conversion circuit 20 uses the electrical energy in the grid to charge the DC bus, and the DC / DC conversion circuit uses the electrical energy in the DC bus to charge the battery pack. When the converter is in discharging mode, the DC / DC conversion circuit uses the electrical energy in the battery pack to discharge to the DC bus, and the AC / DC conversion circuit 20 uses the electrical energy in the DC bus to discharge to the grid.
[0022] The controller 10 is configured to determine the power change of the DC / DC converter circuit based on the electrical parameters of the DC bus; when the current power command is different from the previous power command, if the power of the DC / DC converter circuit does not change, the controller controls the switching transistors in the AC / DC converter circuit 20 to operate according to the previous power command; if the power of the DC / DC converter circuit changes, the controller controls the switching transistors in the AC / DC converter circuit 20 to operate according to the current power command, so as to suppress voltage fluctuations of the DC bus.
[0023] This application does not specifically limit the type of switching transistor in the AC / DC conversion circuit. The switching transistor can be a fully controllable switching transistor. For example, a fully controllable switching transistor may include an insulated gate bipolar transistor (IGBT) or a power metal-oxide-semiconductor field-effect transistor (Power MOSFET).
[0024] The control logic of controller 10 will be described in detail below with reference to the accompanying drawings.
[0025] See Figure 2 The figure is a control block diagram of an AC / DC conversion circuit provided in an embodiment of this application.
[0026] Figure 2 In this context, Pref1 represents the current power command, and Pref2 represents the previous power command.
[0027] With the power command issued by the Energy Management System (EMS) remaining unchanged, there is a relationship between the current power command Pref1 and the previous power command Pref2: Pref1 = Pref2. The AC / DC converter circuit keeps the DC bus voltage Udc constant. The control outer loop of the AC / DC converter circuit is the voltage loop. The difference between the DC bus voltage setpoint Udcr1 and the DC bus voltage Udc is processed by the voltage proportional-integral (PI) regulator 201 to output the current command Idr. The ratio of the previous power command Pref2 to the DC bus voltage Udc is the power command feedforward value Idr1.
[0028] The sum of the current command Idr and the power command feedforward value Idr1, and the difference between this sum and the DC bus current Id, are processed by the current PI regulator 202 to output the target value U of the d-axis component of the AC side voltage. d The target value U of the q-axis component of the AC side voltage q The target value U of the d-axis component of the AC side voltage is 0. d The target value U of the q-axis component of the AC side voltage q Based on the phase angle θ of the converter grid connection point voltage, the α-axis component U of the AC side voltage is obtained through inverse Park transform. α and the β-axis component U of the AC side voltage β The α-axis component U of the AC side voltage α and the β-axis component U of the AC side voltage β Based on the Clark transform, a PWM signal is generated through Space Vector Pulse Width Modulation (SVPWM), and the operation of the controllable switching transistor in the AC / DC conversion circuit is controlled according to the PWM signal.
[0029] The formula for calculating the Clark transform is: ; The formula for calculating the Park transform is: .
[0030] In the formula, A, B, and C are phase A, phase B, and phase C of the AC power grid, respectively.
[0031] Under conditions such as charge-discharge conversion tests, the power command received by the converter may change abruptly, causing the converter to no longer operate in a steady state. Since the converter's power command is first sent to the AC / DC conversion circuit and then, after a time interval, to the DC / DC conversion circuit, and the DC / DC conversion circuit also requires time to respond, if the power command feedforward value Idr1 of the AC / DC conversion circuit changes before the power of the DC / DC conversion circuit has changed, the voltage change on the DC bus cannot be absorbed by the DC / DC conversion circuit in time. This will cause a sudden change in the DC bus voltage Udc, and in severe cases, even overvoltage or undervoltage on the DC bus, leading to converter failure and shutdown.
[0032] Therefore, in the two-stage converter provided in this application embodiment, when the current power command Pref1 is different from the previous power command Pref2, and the power of the DC / DC converter circuit has not changed, even though the AC / DC converter circuit has received the current power command Pref1, the controller still causes the AC / DC converter circuit to use the ratio of the previous power command Pref2 to the DC bus voltage Udc as the power command feedforward value Idr1, thereby controlling the operation of the switching transistors in the AC / DC converter circuit, so that the DC bus voltage Udc remains unchanged under the previous power command Pref2. When the power of the DC / DC converter circuit changes, it means that the voltage change on the DC bus can be absorbed by the DC / DC converter circuit. At this time, the controller causes the AC / DC converter circuit to use the ratio of the current power command Pref1 to the DC bus voltage Udc as the power command feedforward value Idr1 again, thereby achieving the effect of suppressing the fluctuation of the DC bus voltage Udc.
[0033] The two-stage converter provided in this application embodiment has a controller configured to, when the current power command differs from the previous power command, control the switching transistors in the AC / DC conversion circuit according to the previous power command if the power of the DC / DC conversion circuit remains unchanged; and control the switching transistors in the AC / DC conversion circuit according to the current power command if the power of the DC / DC conversion circuit changes. Since the AC / DC conversion circuit only uses the current power command to control the switching transistors after determining that the power of the DC / DC conversion circuit has changed, voltage changes on the DC bus can be promptly absorbed by the DC / DC conversion circuit, achieving the effect of suppressing voltage fluctuations on the DC bus and ensuring the safe and stable operation of the converter.
[0034] This application does not specifically limit the basis for the controller to determine the power change of the DC / DC converter circuit based on the electrical parameters of the DC bus. In one possible implementation, the controller is used to determine the power change of the DC / DC converter circuit based on the absolute value of the current change rate of the DC bus being greater than a current threshold, or based on the absolute value of the voltage change rate of the DC bus being greater than a voltage threshold.
[0035] Specifically, when the DC / DC converter circuit receives the current power command, it executes a new charging / discharging power. When the charging / discharging power of the battery pack changes, the current in the DC bus also changes. At this time, the absolute value of the rate of change of the DC bus current increases. Therefore, when the absolute value of the rate of change of the DC bus current exceeds the current threshold, it can be determined that the power of the DC / DC converter circuit has changed. Similarly, when the charging / discharging power of the battery pack changes, the voltage in the DC bus also changes. Therefore, when the absolute value of the rate of change of the DC bus voltage exceeds the voltage threshold, it can also be determined that the power of the DC / DC converter circuit has changed.
[0036] This application does not specifically limit the values of the current threshold and voltage threshold, which can be selected according to the actual operating conditions of the converter.
[0037] For converters, in the event of a DC / DC converter circuit failure and shutdown, the AC / DC circuit must immediately stop operating upon receiving the fault command from the DC / DC converter circuit. However, there is a time interval between the DC / DC converter circuit shutdown, the issuance of the fault command, and the AC / DC converter circuit receiving the fault command. During this time interval, the AC / DC converter circuit continues to execute the previous power command Pref2, and the voltage change on the DC bus cannot be absorbed by the DC / DC converter circuit in time. This can cause sudden changes in the DC bus voltage Udc, and in severe cases, even overvoltage or undervoltage on the DC bus, resulting in damage to the DC bus capacitors.
[0038] To suppress DC bus voltage fluctuations in the event of a DC / DC converter circuit failure, see [link to relevant documentation]. Figure 1 In the converter provided in this application embodiment, the controller 10 is further configured to control the switching transistor of the AC / DC conversion circuit according to the reverse current command when the DC / DC conversion circuit fails, so as to suppress the voltage fluctuation of the DC bus.
[0039] The control logic of controller 10 will be described in detail below with reference to the accompanying drawings.
[0040] See Figure 3 This figure is a control block diagram of another AC / DC conversion circuit provided in an embodiment of this application.
[0041] Figure 3 and Figure 2 The difference lies in that, in the event of a DC / DC converter circuit failure, the controller is also used to control the operation of the switching transistors in the AC / DC converter circuit according to the reverse current command Idr2. This embodiment of the application is illustrated using the converter being in charging mode, i.e., Pref2 being a positive value. The reverse current command Idr2 is obtained through the negative PI regulator 203 based on the previous power command Pref2 and the DC bus voltage Udc. The reverse current command Idr2 output by the negative PI regulator 203 can be expressed as: Idr2 = (Pref2 / Udc) (-k) p1 + k i1 / s).
[0042] This application does not specifically limit the proportionality coefficient k in the above formula. p1 and integral coefficient k i1 The value of , the proportionality coefficient k p1 and integral coefficient k i1 All values should be positive; you can choose based on the actual situation.
[0043] Specifically, due to the proportionality coefficient k p1 If the value is positive, then in the negative PI controller 203, the proportional coefficient k p1 Inverting the values yields the negative proportionality coefficient -k p1 As time increases, the integral part gradually increases from 0, meaning the reverse current command Idr2 gradually increases from a negative value. When the reverse current command Idr2 is negative, since its direction is opposite to the power command feedforward value Idr1, controlling the switching transistors of the AC / DC converter circuit according to the reverse current command Idr2 can suppress the power command feedforward value Idr1 corresponding to the previous power command Pref2, thereby suppressing voltage fluctuations on the DC bus.
[0044] Those skilled in the art will understand that, in order to suppress voltage fluctuations on the DC bus, the controller is also used to deactivate the reverse current command Idr2 when it increases to approximately zero.
[0045] When the converter is in discharge mode and the DC / DC conversion circuit fails, the controller's control logic is similar to that in the charging mode in the above embodiments, and will not be repeated here.
[0046] Those skilled in the art will understand that in the two-stage converter provided in this application embodiment, the controller's control logic essentially involves introducing reverse power braking control to the other stage power conversion circuit in the event of a fault in the first-stage power conversion circuit. This suppresses the previous power command in the other stage power conversion circuit, thereby achieving the effect of suppressing voltage fluctuations on the DC bus. Therefore, in the two-stage converter provided in this application embodiment, the controller can also be configured to control the operation of the switching transistors in the DC / DC conversion circuit according to the reverse current command in the event of a fault in the AC / DC conversion circuit. This control logic is similar to that in the above embodiments and will not be described again here.
[0047] In order to achieve adaptive control of the DC bus voltage, the controller in the converter provided in this application embodiment is further configured to control the operation of the switching transistors in the AC / DC conversion circuit according to the voltage compensation command.
[0048] See Figure 4 This figure is a control block diagram of another AC / DC conversion circuit provided in an embodiment of this application.
[0049] Figure 4 and Figure 3 The difference is that, Figure 4 It also includes a voltage compensation command Udcr2, the value of which is the current command voltage Udcr1 corresponding to the current power command Pref1. The difference between the voltage Udcr1 of the previous power command Pref2 and the voltage of the previous command.
[0050] In one possible implementation, the converter provided in this application embodiment further includes a DC bus capacitor C connected between the DC positive bus and the DC negative bus.
[0051] The controller is configured to obtain the current command voltage Udcr1 based on the current power command Pref1, the power response time T of the DC / DC converter circuit, and the DC bus capacitance C. There is Pref1 T= U 2 dcr1 / 2; Based on the previous power command Pref2, the power response time T of the DC / DC converter circuit, and the DC bus capacitance C, the previous command voltage Udcr1 is obtained, and Pref2 is obtained. T=C U 2 dcr1 / 2.
[0052] When the current power command Pref1 differs from the previous power command Pref2, the DC bus capacitor C needs to absorb or release energy. Taking the converter in charging mode and the charging power of the DC / DC converter increasing as an example, the energy that the DC bus capacitor C needs to release is ΔP = Pref1 - Pref2 = C. (U) 2 dcr1 - U 2 dcr1 ) / 2. To maintain a constant voltage across the DC bus capacitor C, the controller controls the switching transistors in the AC / DC converter circuit according to the voltage compensation command Udcr2, where Udcr2 = Udcr1. -Udcr1. Specifically, Figure 4 In the process, the DC bus voltage setpoint Udcr1 is summed with the voltage compensation command Udcr2, and the difference between the summation and the DC bus voltage Udc is used by the voltage PI regulator 201 to output the current command Idr.
[0053] When the DC / DC converter is in charging mode and the charging power of the DC / DC converter decreases, or when the converter is in discharging mode, the control logic is similar to the above embodiments and will not be repeated here.
[0054] Because the response time of the DC / DC converter circuit is much shorter than the response time of the AC / DC control of changes in the DC bus voltage, the voltage compensation command value Udcr2 is issued when the power of the DC / DC converter circuit changes, with minimal impact on the converter. That is, if the current power command Pref1 is the same as the previous power command Pref2, the energy ΔP that the DC bus capacitor C needs to absorb or release is 0, meaning the voltage compensation command value Udcr2 is also 0.
[0055] In one possible implementation, the controller can determine that the power of the DC / DC converter circuit changes based on whether the absolute value of the rate of change of the DC bus current is greater than a current threshold or whether the absolute value of the rate of change of the DC bus voltage is greater than a voltage threshold.
[0056] The converter provided in this application embodiment has a controller configured to control the operation of the switching transistors in the AC / DC conversion circuit according to the voltage compensation command. Within the response time of the DC / DC conversion circuit, the controller can increase or decrease the DC bus voltage value according to the current power command and the previous power command, suppressing DC bus voltage fluctuations. It can avoid overcharging or over-discharging of the DC bus capacitor without increasing the DC bus capacitor value, maintain the stability of the DC bus voltage, improve the energy density of the converter, and reduce the hardware cost of the converter.
[0057] Based on the two-stage converter provided in the above embodiments, this application also provides a control method for a two-stage converter. The control method for the two-stage converter provided in this application is applied to the two-stage converter provided in the above embodiments. The two-stage converter includes: a controller, an AC / DC conversion circuit, and N DC / DC conversion circuits, where N is an integer greater than or equal to 1. The first terminal of the AC / DC conversion circuit is used to connect to the AC power grid, and the second terminal of the AC / DC conversion circuit and the first terminals of the N DC / DC conversion circuits are all connected to a DC bus. The second terminal of each DC / DC conversion circuit is used to connect to the corresponding battery cluster.
[0058] See Figure 5 The figure is a schematic diagram of a converter control method provided in an embodiment of this application.
[0059] The method includes: S501: Determines the power change of the DC / DC converter circuit based on the electrical parameters of the DC bus; when the current power command differs from the previous power command, if the power of the DC / DC converter circuit does not change, controls the operation of the switching transistors in the AC / DC converter circuit according to the previous power command; when the power of the DC / DC converter circuit changes, controls the operation of the switching transistors in the AC / DC converter circuit according to the current power command to suppress voltage fluctuations on the DC bus.
[0060] For example, the controller obtains the current power command and the previous power command, and determines the power change of the DC / DC converter circuit based on the electrical parameters of the DC bus. When the current power command and the previous power command are different, if the power of the DC / DC converter circuit does not change, the controller controls the operation of the switching transistors in the AC / DC converter circuit according to the previous power command. When the power of the DC / DC converter circuit changes, the controller controls the operation of the switching transistors in the AC / DC converter circuit according to the current power command to suppress voltage fluctuations on the DC bus.
[0061] The control method provided in this application, when the current power command differs from the previous power command, controls the switching transistors in the AC / DC converter circuit to operate according to the previous power command when the power of the DC / DC converter circuit remains unchanged; and controls the switching transistors in the AC / DC converter circuit to operate according to the current power command when the power of the DC / DC converter circuit changes. Since the AC / DC converter circuit only uses the current power command to control the switching transistors after determining that the power of the DC / DC converter circuit has changed, voltage changes on the DC bus can be promptly absorbed by the DC / DC converter circuit, achieving the effect of suppressing voltage fluctuations on the DC bus and ensuring the safe and stable operation of the converter.
[0062] One possible implementation of the control method includes determining that the power of the DC / DC converter circuit changes based on the absolute value of the rate of change of the DC bus current being greater than a current threshold, or based on the absolute value of the rate of change of the DC bus voltage being greater than a voltage threshold.
[0063] In one possible implementation, the control method further includes: when the DC / DC converter circuit fails, controlling the operation of the switching transistor in the AC / DC converter circuit according to the reverse current command to suppress voltage fluctuations on the DC bus; The reverse current command is obtained from the previous power command and the DC bus voltage through a negative proportional-integral regulator.
[0064] In one possible implementation, the control method further includes controlling the operation of the switching transistors in the AC / DC conversion circuit according to a voltage compensation command; The value of the voltage compensation command is the difference between the current command voltage corresponding to the current power command and the previous command voltage corresponding to the previous power command.
[0065] In one possible implementation, the converter further includes a DC bus capacitor connected between the DC positive bus and the DC negative bus; The control method includes: obtaining the current command voltage based on the current power command, the power response time of the DC / DC converter circuit, and the DC bus capacitance; and obtaining the previous command voltage based on the previous power command, the power response time of the DC / DC converter circuit, and the DC bus capacitance.
[0066] The controller provided in this application embodiment may include software to implement the control method described above. Alternatively, the controller provided in this application embodiment may include hardware to implement the control method described above. Or, the controller provided in this application embodiment may include both software and hardware, using a combination of software and hardware to execute the control method described above.
[0067] 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. The same or similar parts between the various embodiments can be referred to each other.
[0068] 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 two-stage converter, characterized in that, include: The system consists of a controller, an AC / DC converter circuit, and N DC / DC converter circuits, where N is an integer greater than or equal to 1. The first terminal of the AC / DC converter circuit is used to connect to the AC power grid. The second terminal of the AC / DC converter circuit and the first terminals of the N DC / DC converter circuits are all connected to the DC bus. The second terminal of each DC / DC converter circuit is used to connect to the corresponding battery cluster. The controller is configured to determine the power change of the DC / DC converter circuit based on the electrical parameters of the DC bus; when the current power command differs from the previous power command, if the power of the DC / DC converter circuit does not change, the controller controls the operation of the switching transistors in the AC / DC converter circuit according to the previous power command; if the power of the DC / DC converter circuit changes, the controller controls the operation of the switching transistors in the AC / DC converter circuit according to the current power command to suppress voltage fluctuations of the DC bus.
2. The converter according to claim 1, characterized in that, The controller is configured to determine changes in the power of the DC / DC converter circuit based on the electrical parameters of the DC bus, including: The controller is configured to determine that the power of the DC / DC converter circuit changes based on the absolute value of the rate of change of the current of the DC bus being greater than a current threshold, or based on the absolute value of the rate of change of the voltage of the DC bus being greater than a voltage threshold.
3. The converter according to claim 1 or 2, characterized in that, The controller is also configured to control the operation of the switching transistors in the AC / DC conversion circuit according to a reverse current command when the DC / DC conversion circuit fails, so as to suppress voltage fluctuations on the DC bus. The reverse current command is obtained by a negative proportional-integral regulator based on the previous power command and the voltage of the DC bus.
4. The converter according to any one of claims 1 to 3, characterized in that, The controller is also configured to control the operation of the switching transistors in the AC / DC conversion circuit according to voltage compensation commands; The value of the voltage compensation command is the difference between the current command voltage corresponding to the current power command and the previous command voltage corresponding to the previous power command.
5. The converter according to claim 4, characterized in that, Also includes: DC bus capacitor connected between the DC positive bus and the DC negative bus; The controller is configured to obtain the current command voltage based on the current power command, the power response time of the DC / DC converter circuit, and the DC bus capacitor; and to obtain the previous command voltage based on the previous power command, the power response time of the DC / DC converter circuit, and the DC bus capacitor.
6. A control method for a two-stage converter, characterized in that, The two-stage converter includes: a controller, an AC / DC conversion circuit, and N DC / DC conversion circuits, where N is an integer greater than or equal to 1; the first terminal of the AC / DC conversion circuit is used to connect to the AC power grid, the second terminal of the AC / DC conversion circuit and the first terminals of the N DC / DC conversion circuits are all connected to the DC bus, and the second terminal of each DC / DC conversion circuit is used to connect to the corresponding battery cluster. The control method includes: determining the power change of the DC / DC converter circuit based on the electrical parameters of the DC bus; when the current power command differs from the previous power command, if the power of the DC / DC converter circuit does not change, controlling the switching transistors in the AC / DC converter circuit to operate according to the previous power command; and when the power of the DC / DC converter circuit changes, controlling the switching transistors in the AC / DC converter circuit to operate according to the current power command to suppress voltage fluctuations of the DC bus.
7. The control method according to claim 6, characterized in that, The step of determining the power change of the DC / DC converter circuit based on the electrical parameters of the DC bus includes: determining the power change of the DC / DC converter circuit based on the absolute value of the current change rate of the DC bus being greater than a current threshold, or based on the absolute value of the voltage change rate of the DC bus being greater than a voltage threshold.
8. The control method according to claim 6 or 7, characterized in that, Also includes: When the DC / DC conversion circuit fails, the switching transistors in the AC / DC conversion circuit are controlled to operate according to the reverse current command in order to suppress voltage fluctuations of the DC bus. The reverse current command is obtained by a negative proportional-integral regulator based on the previous power command and the voltage of the DC bus.
9. The control method according to any one of claims 6 to 8, characterized in that, It also includes controlling the operation of the switching transistors in the AC / DC conversion circuit according to voltage compensation commands; The value of the voltage compensation command is the difference between the current command voltage corresponding to the current power command and the previous command voltage corresponding to the previous power command.
10. The control method according to claim 9, characterized in that, The converter also includes a DC bus capacitor connected between the DC positive bus and the DC negative bus; The control method includes: obtaining the current command voltage based on the current power command, the power response time of the DC / DC converter circuit, and the DC bus capacitor; and obtaining the previous command voltage based on the previous power command, the power response time of the DC / DC converter circuit, and the DC bus capacitor.