Control method and device of bidirectional DC / DC converter and energy storage conversion system

Abstract

The invention provides a control method and device of a bidirectional DC / DC converter and an energy storage conversion system. The control method comprises the steps that after direct-current bus voltage is processed through a transfer function of a virtual impedance controller, virtual impedance output is obtained, a current compensation set value is obtained, the virtual impedance controller is used for generating a control quantity related to the direct-current bus voltage and actively adjusting system impedance characteristics, and the current compensation set value is obtained; a control signal is generated according to the virtual impedance output and the current compensation set value, a second switching signal is output by the PWM module in the charging state of the energy storage device according to the control signal, and the second switching signal is used for being output to a base electrode of a second switching device in the bidirectional DC / DC converter. And virtual impedance is generated for the bidirectional DC / DC converter to neutralize or offset negative impedance presented by the bidirectional DC / DC converter, so that the reliability and the stability of power supply are improved.

Description

Technical Field

[0001] This application relates to the field of converter control, and more particularly to a control method, apparatus and energy storage converter system for a bidirectional DC / DC converter. Background Technology

[0002] Energy storage systems (ESS) can store energy during peak periods of renewable energy generation such as wind and solar power, and release energy during peak demand or off-peak periods of power generation, thereby smoothing the power supply and improving the stability and reliability of the power grid.

[0003] Currently, a two-stage energy storage converter system is commonly used to connect the energy storage system to the AC power system. The front stage includes a bidirectional DC-DC converter to realize the charging and discharging function of the energy storage system, and the back stage includes an alternating current-direct current converter to realize grid connection.

[0004] However, the inventors of this application have discovered that when the energy storage system is used as a constant power load (CPL) for energy storage charging, the CPL causes the bidirectional DC / DC converter to exhibit negative impedance characteristics, which leads to a reduction in the reliability and stability of power supply between the CPL and the grid-connected converter. Summary of the Invention

[0005] This application provides a control method, device, and energy storage converter system for a bidirectional DC / DC converter to solve the negative impedance problem that occurs in bidirectional DC / DC converters.

[0006] To solve the above-mentioned technical problems, the embodiments of this application are implemented through the following aspects.

[0007] In a first aspect, embodiments of this application provide a control method for a bidirectional DC / DC converter, including: Obtain virtual impedance output and current compensation settings The virtual impedance output is determined by the DC bus voltage. Transfer function after virtual impedance controller The DC bus voltage is obtained through processing. Located between the connected bidirectional DC / DC converter and the AC / DC grid-connected converter; based on the virtual impedance output and the current compensation setting value. A control signal is generated; based on the control signal, a second switching signal is output by the PWM module during the charging state of the energy storage device. The second switch signal Used to output to the base of the second switching device in the bidirectional DC / DC converter, generating a virtual impedance for the bidirectional DC / DC converter.

[0008] Secondly, embodiments of this application provide a control device, including: a current compensation acquisition module, used to acquire a virtual impedance output and a current compensation setpoint. The virtual impedance output is determined by the DC bus voltage. Transfer function after virtual impedance controller The DC bus voltage is obtained through processing. Located between the connected bidirectional DC / DC converter and the AC / DC grid-connected converter; a control signal generation module is used to output based on the virtual impedance and the current compensation setpoint. A control signal is generated; a virtual impedance generation module is used to output a second switching signal by the PWM module according to the control signal during the charging state of the energy storage device. The second switch signal Used to output to the base of the second switching device in the bidirectional DC / DC converter, generating a virtual impedance for the bidirectional DC / DC converter.

[0009] Secondly, embodiments of this application provide an energy storage converter system, which includes an energy storage device, a bidirectional DC / DC converter, and an AC / DC grid-connected converter. The bidirectional DC / DC converter is connected between the energy storage device and a DC bus, and the AC / DC grid-connected converter is connected between the DC bus and the power grid. The bidirectional DC / DC converter includes a bidirectional Buck-Boost circuit, which includes a first switching device and a second switching device. The bidirectional DC / DC converter is controlled by the control method described in the first aspect.

[0010] Fourthly, embodiments of this application provide an electronic device, including: a memory, a processor, and computer-executable instructions stored in the memory and executable on the processor, wherein the computer-executable instructions, when executed by the processor, implement the steps of the method described in the first aspect. This application provides a control method for a bidirectional DC / DC converter, which controls the DC bus voltage. Transfer function after virtual impedance controller After processing, a virtual impedance output is obtained, and the current compensation setpoint is acquired. Among them, virtual impedance controller This is used to generate control quantities related to the DC bus voltage, actively adjust the system impedance characteristics, and then output based on the virtual impedance and the current compensation setpoint. A control signal is generated, and then, based on this control signal, a second switching signal is output by the PWM module during the charging state of the energy storage device. Second switch signal Used to output to the base of the second switching device in the bidirectional DC / DC converter, generating a virtual impedance for the bidirectional DC / DC converter to neutralize or cancel the negative impedance presented by the bidirectional DC / DC converter, thereby improving the reliability and stability of power supply. Attached Figure Description

[0011] To more clearly illustrate the technical solutions in one or more embodiments of this specification, the accompanying drawings used in the description of the embodiments or prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this specification. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0012] Figure 1 This is a control block diagram of a bidirectional DC / DC converter in related technologies; Figure 2 A flowchart illustrating a control method for a bidirectional DC / DC converter provided in this application embodiment; Figure 3 A control block diagram of a bidirectional DC / DC converter provided in an embodiment of this application; Figure 4 A circuit topology for an energy storage converter system provided in this application embodiment; Figure 5(a) shows the results based on Figure 1 The obtained impedance Bode plot of the energy storage device discharge; Figure 5(b) shows the results based on... Figure 1 The obtained impedance Bode plot of the energy storage device during charging; Figure 6 Based on Figure 1 right Figure 4 An equivalent circuit; Figure 7 Based on Figure 3 right Figure 4 An equivalent circuit; Figure 8(a) shows the results based on Figure 3 The obtained impedance Bode plot of the energy storage device discharge; Figure 8(b) shows the results based on... Figure 3 The obtained impedance Bode plot of the energy storage device during charging; Figure 9(a) shows the sequential charging process of the energy storage device. Figure 1 and Figure 3 The simulation waveforms shown by the control method; Figure 9(b) shows the simulation waveforms when the energy storage device discharges, which successively adopt Figure 1 and Figure 3 The control method; Figure 10 is a schematic structural diagram of a control device for a bidirectional DC / DC converter provided by an application embodiment; Figure 11 is a schematic hardware structure diagram of an electronic device provided by an embodiment of the present application. Specific embodiments

[0013] In order to enable those skilled in the art to better understand the technical solutions in one or more embodiments of this specification, the following will clearly and completely describe the technical solutions in one or more embodiments of this specification in conjunction with the accompanying drawings in one or more embodiments of this specification. Obviously, the described embodiments are only a part of the embodiments of this specification, rather than all the embodiments. Based on one or more embodiments of this specification, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of this document.

[0014] [[ID=二十一]]Refer [[ID=二十二]] Figure 1 [[ID=二十三]]to, which is a control block diagram of a current closed-loop controlled bidirectional DC / DC converter in the related art. [[ID=二十四]] [[ID=二十五]]

[0015] [[ID=二十六]]In [[ID=二十七]] Figure 1 [[ID=二十八]], [[ID=二十九]] [[ID=三十]]is the power reference value of the energy storage device (such as the charge and discharge power command), which can also be understood as the power given value and is the input target of the control; [[ID=三十一]] [[ID=三十二]]is the terminal voltage of the energy storage device (such as the output voltage of the battery module), which is used to achieve power-current conversion; the " / " module is the power-current conversion link, and according to the formula [[ID=三十三]]<A000095>[[ID=三十四]]divides the power reference [[ID=三十五]] [[ID=三十六]]by the terminal voltage [[ID=三十七]] [[ID=三十八]]to obtain the current reference value [[ID=三十九]] [[ID=四十]]of the energy storage device; [[ID=四十一]] [[ID=四十二]]is the actual current of the energy storage device (discharge current or charge current), which is used for the deviation calculation of the closed-loop control; [[ID=四十三]] [[ID=四十四]]is the transfer function of the current controller, which is used to adjust the current deviation and output a control signal; the "energy storage device working state selection" module can switch the working mode of the energy storage according to the control requirements, including the charge state and the discharge state; the Pulse-Width Modulation (PWM) module is a pulse width modulation module that generates a switch drive signal according to the control signal [[ID=四十五]] [[ID=四十六]]、[[ID=四十七]] Switching devices that control energy storage converters (such as bidirectional DC / DC converters). Among them, It can be a proportional-integral (PI) controller.

[0016] Figure 1 The control method corresponding to the control block diagram is to first set the power reference value. Divide by the terminal voltage of the energy storage device To obtain the current reference value Then the current reference value With the actual current of the energy storage device The resulting deviation is compared and processed by the transfer function of the current controller. The PWM module adjusts and generates a control signal, which, combined with the different operating states of the energy storage device (charging or discharging), generates corresponding switching signals. , This is to control the bidirectional DC / DC converter to achieve power tracking for charging and discharging. The operating state of the energy storage device is selected based on control signals and system requirements.

[0017] The inventors of this application discovered in their research that when the aforementioned bidirectional DC / DC converter is applied to an energy storage system as a constant power load (CPL), the CPL causes the bidirectional DC / DC converter to exhibit negative impedance characteristics when the energy storage device is charging. This negative impedance characteristic leads to a decrease in the reliability and stability of power supply between the CPL and the AC / DC grid-connected converter (GCC).

[0018] To solve this technical problem, additional sensors are required in related technologies, which increases costs and failure rates.

[0019] To address the aforementioned issues without requiring additional sensors, one or more embodiments of the control method for a bidirectional DC / DC converter provided in this application are as follows: Reference Figure 2 This illustrates a control method for a bidirectional DC / DC converter provided in an embodiment of this application, which may include the following steps S201 to S203, corresponding to... Figure 3 The present application provides a control block diagram of a bidirectional DC / DC converter according to an embodiment of the present application, which can realize stability enhancement control based on virtual impedance.

[0020] Step S201: Obtain the virtual impedance output and current compensation setting values. The virtual impedance output is determined by the DC bus voltage. Transfer function after virtual impedance controller The processed DC bus voltage It is located between the connected bidirectional DC / DC converter and the AC / DC grid-connected converter.

[0021] Step S202, based on the virtual impedance output and current compensation setting value , generate control signals.

[0022] Step S203: According to the control signal, the PWM module outputs a second switching signal during the charging state of the energy storage device. The second switch signal Used to output to the base of the second switching device in the bidirectional DC / DC converter, generating (or adding) a virtual impedance for the bidirectional DC / DC converter.

[0023] In this embodiment, the virtual impedance controller Used to generate control quantities related to the DC bus voltage, actively adjusting the system impedance characteristics, and controlling the DC bus voltage. After virtual impedance controller After processing, the virtual impedance output is obtained, and the current compensation setting value is also obtained. Based on the virtual impedance output and the current compensation setting value... A control signal is generated, and then, based on this control signal, the PWM module outputs a second switching signal during the charging state of the energy storage device. Second switch signal The base of the second switching device in the bidirectional DC / DC converter is used to generate a virtual impedance for the bidirectional DC / DC converter to neutralize or cancel the negative impedance, thereby solving the negative impedance characteristic of the bidirectional DC / DC converter in the charging state and improving the reliability and stability of power supply in the energy storage converter system.

[0024] In this embodiment, the negative impedance is offset by actively introducing a "virtual impedance" characteristic, thereby avoiding oscillation and enhancing the DC bus voltage. This improves the stability and reliability of the system and enhances the robustness of the system's dynamic response.

[0025] Here, virtual impedance output refers to the signal output by the virtual impedance controller. Figure 3 In this context, the virtual impedance controller outputs the voltage loop multiplied by its control gain. Current compensation setpoint. Used to compensate for virtual impedance output.

[0026] Among them, the current compensation setting value This is a manually set value, and this set value is related to the virtual impedance controller. The gain is related, in one implementation. .in It is the target value of DC voltage. It is the transfer function of a virtual impedance controller (such as a PI controller). The proportionality coefficient.

[0027] Among them, the current compensation setting value The introduction of this technology can adjust the output current of the bidirectional DC / DC converter, reduce the current deviation caused by the DC voltage feedback component, and improve the dynamic response speed of the converter.

[0028] The operating state (charging or discharging) of the energy storage device can be determined by the needs of the energy storage system, and can be selected based on the control signals mentioned above during control.

[0029] In one implementation, step S202 involves determining the virtual impedance output and the current compensation setting value. Generating a control signal may include steps S2021 and S2022.

[0030] Step S2021, the power reference value of the energy storage device Divide by the terminal voltage of the energy storage device Obtain the current reference value of the energy storage device. Among them, the power reference value of the energy storage device It is also the power setpoint, which can be set according to actual needs; the terminal voltage of the energy storage device. It can be the output voltage of the energy storage battery module.

[0031] Step S2022: Obtain virtual impedance output and current compensation setting values. The processed value is compared with the current reference value. Superimposed and then combined with the actual current of the energy storage device The resulting deviation is compared and passed through the transfer function of the current controller. Adjustment is performed to generate a control signal. This includes the current compensation amount and the current reference value. Superposition can refer to finding the difference between two things.

[0032] In the embodiments of this application, the control signal can be based not only on the current compensation set value Generation, also combined with the current reference of the energy storage device Actual current of energy storage device And through the transfer function of the current controller The above control signal is generated through adjustment, which not only meets the requirements of the constant power load CPL, but also solves the negative impedance characteristic of the bidirectional DC / DC converter in the charging state.

[0033] In one embodiment, the control method may further include: outputting a first switching signal by the PWM module during the discharge state. The first switch signal This signal is used to output to the base of the first switching device in the bidirectional DC / DC converter. Since the bidirectional DC / DC converter does not exhibit negative impedance characteristics in the discharge state, under normal circumstances, this first switching signal... It will not cooperate with the first switching device to generate a virtual impedance for the bidirectional DC / DC converter. Of course, in some special cases, if the bidirectional DC / DC converter exhibits negative impedance characteristics during discharge, this first switching signal... It can also be used in conjunction with the first switching device to generate a virtual impedance for neutralizing or offsetting negative impedance in a bidirectional DC / DC converter.

[0034] In one embodiment, the virtual impedance controller can be a proportional-integral (PI) controller, and the current controller can be a PI controller.

[0035] Among them, the transfer function of the virtual impedance controller middle, , .

[0036] in, , The transfer functions of the virtual impedance controller are respectively The proportional coefficient and integral coefficient; , The transfer functions of the current controller are respectively The proportional coefficient and integral coefficient; This is the steady-state value of the DC voltage. The inductance value of the energy storage inductor. This is the capacitance value of the output capacitor. This represents the steady-state value of the inductor current. This refers to the duty cycle during which the second switching device in the bidirectional DC / DC converter is turned on. The steady-state value of the DC voltage can be understood as the rated value, representing the target voltage of the DC bus or the DC side of the AC / DC grid-connected converter during stable operation.

[0037] In the discharge state, the first switching device is turned on and the second switching device is turned off; conversely, in the charging state, the first switching device is turned off and the second switching device is turned on.

[0038] In one embodiment, the method further includes: Obtain the circuit equations of the bidirectional DC / DC converter in small-signal form under discharge conditions; Obtain the duty cycle equation of the bidirectional DC / DC converter under charging conditions; Based on the small-signal circuit equations and the duty cycle equation, determine the remodeled output impedance of the bidirectional DC / DC converter during the charging state. ; Based on the DC bus voltage Virtual impedance introduced by feedback With reshaped output impedance Original impedance The corresponding relationship is used to determine the reshaped output impedance. and original output impedance Relationship; Based on this relationship, the reshaped output impedance Set it to infinity to determine the transfer function of the virtual impedance controller. In and .

[0039] Among them, the reshaped output impedance Setting it to infinity can help improve system stability.

[0040] Among them, a current compensation setting value is introduced. It can adjust the output current of the bidirectional DC / DC converter, reduce the current deviation caused by DC voltage feedback components, and improve the dynamic response speed of the converter. Current setpoint It can be set manually.

[0041] Among them, the current compensation setting value can also be set. Compared with this current reference value The superposition of the actual current of the energy storage device The resulting deviation is compared and passed through the transfer function of the current controller. Adjustment is made to generate control signals.

[0042] This application also provides an energy storage converter system, as described in the embodiments. Figure 4 The energy storage converter system includes an energy storage device, a bidirectional DC / DC converter, and an AC / DC grid-connected converter. The bidirectional DC / DC converter is connected between the energy storage device and the DC bus, and the AC / DC grid-connected converter is connected between the DC bus and the power grid. The bidirectional DC / DC converter includes a bidirectional Buck-Boost circuit, which includes a first switching device and a second switching device. The bidirectional DC / DC converter is controlled by the control method for the bidirectional DC / DC converter as described in the above embodiment.

[0043] The energy storage module is connected to the DC bus via a bidirectional DC / DC converter. The grid-connected AC / DC converter (GCC) acts as the energy hub, providing a power flow path between the grid and the DC bus. The bidirectional DC / DC converter has two operating modes: in step-down mode (Buck), it performs step-down energy storage (energy storage charging); in step-up mode (Boost), it performs step-up discharge (energy storage discharging).

[0044] In the aforementioned bidirectional DC / DC converter, the first switching signal is connected. The first switching device, and the connection to the second switching signal The second switching device is a power switching device (such as a MOSFET or IGBT), which can achieve bidirectional energy conversion through complementary conduction. In the energy storage device charging mode (battery absorbs energy): the first switching device is turned on and the second switching device is turned off. The circuit operates in Buck mode, converting the high-voltage energy from the DC bus into low-voltage energy suitable for the battery. In the energy storage device discharging mode (battery releases energy): the second switching device is turned on and the first switching device is turned off. The circuit operates in Boost mode, converting the low-voltage energy from the battery into high-voltage energy suitable for the DC bus. Inductor It is an energy storage inductor that stores / releases energy when the first or second switching device switches, enabling voltage boost / buck and suppressing current ripple to ensure smooth current flow. Capacitor (DC bus side) and capacitors (On the battery side) are filter capacitors, used to stabilize voltage (suppress fluctuations) and filter harmonics, ensuring stable voltage at the DC bus and battery terminals. During charging: Current. Flowing in from the DC bus, passing through the first switching device and inductor Capacitors flowing to the battery side Ultimately, this charges the energy storage device. During discharge: Current The current flows out from the battery side, through the anti-parallel diode and inductor of the second switching device. It flows to the DC bus to replenish the DC bus with electrical energy.

[0045] exist Figure 4 In the middle, the left side includes the power grid and transformer. The AC power supply on the left undergoes voltage transformation (such as step-down or isolation) through the transformer, providing a suitable AC input for the subsequent AC / DC grid-connected converter. The AC / DC grid-connected converter converts the AC output from the transformer into DC power and then... Filtering stabilizes the DC bus voltage, providing DC input for the subsequent bidirectional DC / DC converter.

[0046] Next, returning to the control method for bidirectional DC / DC converters mentioned above, we will explain the transfer function of the virtual impedance controller. The design method is described, and the control method proposed in this application is verified to be able to solve the negative impedance problem and improve the stability and reliability of the system compared with related technologies.

[0047] Based on the above Figure 4 Taking the circuit diagram of the energy storage converter system shown as an example, when the energy storage device discharges, the bidirectional DC / DC converter operates in Boost mode. Figure 4 The circuit structure and Laplace transform shown can be used to obtain the circuit equation in small-signal form as follows: (1) (2) (3) in, D for Figure 4 The duty cycle of the first or second switching device is [value missing]. This is the steady-state value of the DC voltage. This represents the steady-state value of the inductor current. For output capacitor, This is the input capacitor.

[0048] If we take Figure 1 Control block diagrams Figure 4 By controlling the bidirectional DC / DC converter in the circuit, the following equations and conclusions can be derived: by Figure 1 Control block diagrams Figure 4 By controlling the bidirectional DC / DC converter in the circuit, the duty cycle equation can be obtained as follows: (4) in, It uses a PI controller in the current loop.

[0049] Combining equations (1)-(4), at this time Figure 4 The high-voltage side DC impedance of the bidirectional DC / DC converter system during the discharge of the energy storage device is derived as follows: (5) Similarly, the high-voltage side DC impedance of the bidirectional DC / DC converter system during energy storage device charging can be obtained as follows: (6) To verify the accuracy of the small-signal impedance model, frequency sweep tests were performed using MATLAB / Simulink. Harmonic currents of different frequencies were continuously injected into the intermediate DC link from 1Hz to 2000Hz. According to Thevenin's theorem, the ratio of the response voltage to the harmonic current is the DC impedance at the test point. The theoretical and measured results of the bidirectional DC / DC converter are shown in Figure 5, where lines and circles represent the theoretical and measured impedances, respectively. Figure 5 is the impedance Bode plot, where Figure 5(a) shows the impedance results for energy storage discharge, and Figure 5(b) shows the impedance results for energy storage charging. The theoretical and measured impedances agree well within the switching frequency range, indicating that the impedance model of the bidirectional DC / DC converter is accurate.

[0050] As shown in Figure 5(b), the impedance of the bidirectional DC / DC converter exhibits negative impedance characteristics within the target frequency range during energy storage charging. This negative incremental impedance will lead to a deterioration in the dynamic characteristics of the system and may even cause system voltage oscillations, which is one of the main factors affecting the voltage stability of the DC grid.

[0051] Next, the stability of the bidirectional DC / DC converter in the intermediate DC link is analyzed based on impedance analysis. As shown in Figure 6, the two-stage energy storage converter system can be regarded as an interconnected converter system consisting of a source subsystem and a load subsystem. The source subsystem is equivalent to an impedance. It is connected in series with a voltage source; the load subsystem is equivalent to an impedance. It is connected in parallel with the current source.

[0052] exist Figure 6 In the middle, DC voltage The calculation formula is: (7) in, It is the impedance ratio of the source and load subsystems, which is equivalent to the small loop gain of the system.

[0053] According to the impedance-based stability criterion, in the impedance Bode plot, when and When the amplitude curves intersect and the phase difference at the intersection frequency is greater than 180°, the system is unstable. As shown in Figure 5(b), when the stored energy is discharged, The phase angle is at 90° to A 180° element, i.e., a negative damping element. In the system source impedance... In this respect, the line inductance and supporting capacitance will increase. The amplitude, if its amplitude is greater than ,at the same time When the frequency is in the negative damping band, the system exhibits negative damping near that frequency. If the output voltage of the bidirectional DC / DC converter decreases (increases) slightly, it will cause the current to increase (decrease), further exacerbating the decrease (increase) in the output voltage of the bidirectional DC / DC converter, forming a positive feedback process, leading to DC system oscillation, i.e., DC bus voltage... Unstable.

[0054] Therefore, if we take Figure 1 Control block diagrams Figure 4 The bidirectional DC / DC converter in the circuit is controlled by an impedance Bode plot as shown in Figure 5, which exhibits negative damping. This negative damping will cause the DC bus voltage to... Unstable.

[0055] In the embodiments of this application, using Figure 2 Control block diagrams Figure 4 The bidirectional DC / DC converter is controlled to shape its output impedance, thereby improving the stability of the bidirectional DC / DC converter in the intermediate DC link.

[0056] If we take Figure 2 Control block diagrams Figure 4 By controlling the bidirectional DC / DC converter in the circuit, the following equations and conclusions can be derived: Due to the relevant technologies ( Figure 1 The bidirectional DC / DC converter uses single current loop control. To construct a virtual impedance, a virtual impedance controller is considered. Introduce DC voltage feedback, such as Figure 4 As shown. Taking the charging state of the energy storage device as an example, the duty cycle equation can be obtained as follows: (8) Combining equations (1)-(3) and (8), the output impedance of the bidirectional DC / DC converter when the energy storage device is in the charging state can be obtained. : (9) in, (10) Reshaped output impedance and original output impedance The expressions have the same numerator, from which we can derive the virtual impedance introduced by DC voltage feedback. With the original impedance It is a parallel relationship, such as Figure 7 As shown. Therefore, the introduced parallel virtual impedance is obtained. The expression is (11) Additionally, a current setting value needs to be added. It is used to adjust the output current of the bidirectional DC / DC converter, reduce the current deviation caused by the DC voltage feedback component, and improve the dynamic response speed of the converter.

[0057] Among them, the reshaped output impedance and original output impedance The relationship is represented as follows: (12) Let the denominator of expression (12) be 0. This will increase to infinity, which is beneficial for improving the stability of the system. Therefore, substituting equations (6) and (11) into equation (12), we can obtain... (13) Choosing a PI controller as the virtual impedance controller, simplifying equation (13) yields the following: (14) (15) in, , The transfer functions of the virtual impedance controller are respectively proportionality coefficient and integral coefficient, , The transfer functions of the current controller are respectively The proportional and integral coefficients. Substituting the corresponding parameters into equations (14) and (15) yields the virtual impedance controller. The parameters.

[0058] This completes the design of the virtual impedance controller.

[0059] Based on the control method of the bidirectional DC / DC converter proposed in this application, frequency sweep tests were performed in MATLAB / Simulink. The results are shown in Figure 8. The solid line represents the impedance Bode plot of the aforementioned sensor-controlled system, and the dashed line represents the impedance Bode plot of the virtual impedance control in the embodiment proposed in this application. Figure 8(a) shows the impedance Bode plot of the energy storage device during discharge, while Figure 8(b) shows the impedance Bode plot of the energy storage device during charging. It can be seen that adding virtual impedance in the embodiment of this application does not change the positive impedance characteristic during energy storage discharge, and it raises the phase curve; adding virtual impedance can correct the negative impedance characteristic of energy storage charging to a positive value throughout the entire frequency range. The results show that the control method proposed in the embodiment of this application has the effect of enhancing stability in both energy storage charging and discharging conditions.

[0060] A simulation model was built on the MATLAB / Simulink simulation platform for time-domain verification, and the simulation waveforms shown in Figure 9(a) and Figure 9(b) were obtained. Figure 9(a) shows the simulation waveform during the charging of the energy storage device. Before 0.4s, the bidirectional DC / DC converter uses current closed-loop control (corresponding to...). Figure 1 (Referring to related technologies), it can be seen that when current closed-loop control is used, the DC link of the system becomes unstable, resulting in oscillations. However, when the virtual impedance-based control method proposed in this application is applied starting at 0.4s, the oscillations are suppressed, the DC voltage converges, and eventually stabilizes at the reference value of 1200V. Therefore, the control method for bidirectional DC / DC converters proposed in this application can improve the oscillations during energy storage device charging and enhance system robustness.

[0061] Figure 9(b) shows the simulated waveform of the energy storage device during discharge. Before 0.4s, the bidirectional DC / DC converter adopts current closed-loop control (corresponding to...). Figure 1 (Related technologies); the system remains stable even after the virtual impedance-based control method proposed in this application is applied at 0.4s. Therefore, the control method for bidirectional DC / DC converters proposed in this application improves the oscillations during charging of the energy storage device and enhances the system's robustness without weakening the robustness during discharging.

[0062] This application also provides a control device for a bidirectional DC / DC converter. Figure 10 This diagram illustrates the structure of a control device 100 provided in an embodiment of this application. The device includes: The current compensation acquisition module 110 is used to acquire the virtual impedance output and the current compensation setpoint. The virtual impedance output is determined by the DC bus voltage. Transfer function after virtual impedance controller The DC bus voltage is obtained through processing. Located between the connected bidirectional DC / DC converter and the AC / DC grid-connected converter; The control signal generation module 120 is used to output the virtual impedance and the current compensation set value. Generate control signals; The virtual impedance generation module 130 is used to output a second switching signal from the PWM module according to the control signal during the charging state of the energy storage device. The second switch signal Used to output to the base of the second switching device in the bidirectional DC / DC converter, generating a virtual impedance for the bidirectional DC / DC converter.

[0063] In one alternative implementation, the control signal generation module is configured to output the virtual impedance and the current compensation setpoint. Generate control signals, including: Power reference value of energy storage device Divide by the terminal voltage of the energy storage device Obtain the current reference value of the energy storage device. ; Obtain the virtual impedance output and the current compensation setting value. The processed value and the current reference value Superimposed and then combined with the actual current of the energy storage device The resulting deviation is compared and passed through the transfer function of the current controller. Adjustment, generation of control signals.

[0064] In one optional implementation, the virtual impedance controller is a PI controller, and the current controller... It is a PI controller, and , , in , Virtual impedance controllers The proportional coefficient and integral coefficient; , Current controller The proportional coefficient and integral coefficient; This is the steady-state value of the DC voltage. The inductance value of the energy storage inductor. This is the capacitance value of the output capacitor. This represents the steady-state value of the inductor current. The duty cycle during which the second switching device in the bidirectional DC / DC converter is turned on.

[0065] In an optional embodiment, the control device is further configured to: output a first switching signal from the PWM module during the discharge state. The first switch signal Used to output to the base of the first switching device in the bidirectional DC / DC converter.

[0066] The device 100 provided in this application embodiment can execute the methods described in the preceding method embodiments and achieve the functions and beneficial effects of the methods described in the preceding method embodiments, which will not be repeated here.

[0067] Figure 11The diagram illustrates the hardware structure of an electronic device implementing the embodiments of this application. Referring to the diagram, at the hardware level, the electronic device includes a processor and optionally, an internal bus, a network interface, and a memory. The memory may include RAM, such as high-speed random-access memory (RAM), or non-volatile memory, such as at least one disk storage device. Of course, the electronic device may also include other hardware required for other services.

[0068] The processor, network interface, and memory can be interconnected via an internal bus, which can be an Industry Standard Architecture (ISA) bus, a Peripheral Component Interconnect (PCI) bus, or an Extended Industry Standard Architecture (EISA) bus, etc. This bus can be categorized as an address bus, data bus, control bus, etc. For ease of illustration, only a single bidirectional arrow is used in this diagram, but this does not imply that there is only one bus or one type of bus.

[0069] Memory is used to store programs. Specifically, programs may include program code, which includes computer operation instructions. Memory may include main memory and non-volatile memory, and provides instructions and data to the processor.

[0070] The processor reads the corresponding computer program from non-volatile memory into main memory and then executes it, forming a device at the logical level that locates the target user. The processor executes the program stored in memory and specifically performs the following: Figure 2 The methods disclosed in the embodiments shown achieve the functions and beneficial effects of the methods described in the preceding method embodiments, and will not be repeated here.

[0071] The above is as stated in this application. Figure 2The methods disclosed in the illustrated embodiments can be applied to or implemented by a processor. The processor may be an integrated circuit chip with signal processing capabilities. During implementation, each step of the above methods can be completed by integrated logic circuits in the processor's hardware or by instructions in software form. The processor can be a general-purpose processor, including a Central Processing Unit (CPU), a Network Processor (NP), etc.; it can also be a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field-Programmable Gate Array (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, or discrete hardware components. It can implement or execute the methods, steps, and logic block diagrams disclosed in the embodiments of this application. The general-purpose processor can be a microprocessor or any conventional processor. The steps of the methods disclosed in the embodiments of this application can be directly embodied in the execution of a hardware decoding processor, or executed by a combination of hardware and software modules in the decoding processor. The software module can reside in a mature storage medium in the field, such as random access memory, flash memory, read-only memory, programmable read-only memory, electrically erasable programmable memory, or registers. This storage medium is located in memory, and the processor reads information from the memory and, in conjunction with its hardware, completes the steps of the above method.

[0072] The electronic device can also execute the methods described in the preceding method embodiments and achieve the functions and beneficial effects of the methods described in the preceding method embodiments, which will not be repeated here.

[0073] Of course, in addition to software implementation, the electronic device of this application does not exclude other implementation methods, such as logic devices or a combination of hardware and software, etc. In other words, the execution subject of the following processing flow is not limited to each logic unit, but can also be hardware or logic devices.

[0074] This application also proposes a computer-readable storage medium that stores one or more programs, which, when executed by an electronic device including multiple applications, cause the electronic device to perform... Figure 2 The methods disclosed in the embodiments shown achieve the functions and beneficial effects of the methods described in the preceding method embodiments, and will not be repeated here.

[0075] The computer-readable storage medium mentioned above includes read-only memory (ROM), random access memory (RAM), magnetic disk or optical disk, etc.

[0076] Furthermore, embodiments of this application also provide a computer program product, the computer program product including a computer program stored on a non-transitory computer-readable storage medium, the computer program including program instructions, which, when executed by a computer, implement the following process: Figure 2 The methods disclosed in the embodiments shown achieve the functions and beneficial effects of the methods described in the preceding method embodiments, and will not be repeated here.

[0077] In summary, the above description is merely a preferred embodiment of this application and is not intended to limit the scope of protection of this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

[0078] The systems, devices, modules, or units described in the above embodiments can be implemented by computer chips or entities, or by products with certain functions. A typical implementation device is a computer. Specifically, a computer can be, for example, a personal computer, laptop computer, cellular phone, camera phone, smartphone, personal digital assistant, media player, navigation device, email device, game console, tablet computer, wearable device, or any combination of these devices.

[0079] Computer-readable media includes both permanent and non-permanent, removable and non-removable media that can store information using any method or technology. Information can be computer-readable instructions, data structures, modules of programs, or other data. Examples of computer storage media include, but are not limited to, phase-change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technologies, CD-ROM, digital versatile optical disc (DVD) or other optical storage, magnetic tape, magnetic magnetic disk storage or other magnetic storage devices, or any other non-transferable medium that can be used to store information accessible by a computing device. As defined herein, computer-readable media does not include transient computer-readable media, such as modulated data signals and carrier waves.

[0080] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0081] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to interchangeably. Each embodiment focuses on describing the differences from other embodiments. In particular, the system embodiments are basically similar to the method embodiments, so the description is relatively simple; relevant parts can be referred to the descriptions in the method embodiments.

Claims

1. A control method for a bidirectional DC-to-DC / DC converter, characterized in that, The control method includes: Obtain virtual impedance output and current compensation settings The virtual impedance output is determined by the DC bus voltage. Transfer function after virtual impedance controller The output is the DC bus voltage. Located between the connected bidirectional DC / DC converter and the AC / DC grid-connected converter; Based on the virtual impedance output and the current compensation setting value Generate control signals; According to the control signal, during the charging state of the energy storage device, a second switching signal is output by the pulse width modulation (PWM) module. The second switch signal Used to output to the second switching device in the bidirectional DC / DC converter, generating a virtual impedance for the bidirectional DC / DC converter.

2. The control method according to claim 1, characterized in that, Based on the virtual impedance output and the current compensation setting value Generate control signals, including: Power reference value of energy storage device Divide by the terminal voltage of the energy storage device Obtain the current reference value of the energy storage device. ; Obtain the virtual impedance output and the current compensation setting value. The processed value and the current reference value Superimposed and then combined with the actual current of the energy storage device The resulting deviation is compared and passed through the transfer function of the current controller. Adjustment, generation of control signals.

3. The control method according to claim 2, characterized in that, The virtual impedance controller is a proportional-integral (PI) controller, and the current controller is a PI controller. ， ， in , The transfer functions of the virtual impedance controller are respectively The proportional coefficient and integral coefficient; , The transfer functions of the current controller are respectively The proportional coefficient and integral coefficient; This is the steady-state value of the DC voltage. The inductance value of the energy storage inductor. This is the capacitance value of the output capacitor. This represents the steady-state value of the inductor current. The duty cycle during which the second switching device in the bidirectional DC / DC converter is turned on.

4. The control method according to claim 1, characterized in that, The method further includes: outputting a first switching signal by the PWM module during the discharge state. The first switch signal Used to output to the base of the first switching device in the bidirectional DC / DC converter.

5. A control device for a bidirectional DC / DC converter, characterized in that, The control device includes: The current compensation acquisition module is used to acquire the virtual impedance output and the current compensation setpoint. The virtual impedance output is determined by the DC bus voltage. Transfer function after virtual impedance controller The output is the DC bus voltage. Located between the connected bidirectional DC / DC converter and the AC / DC grid-connected converter; The control signal generation module is used to output the virtual impedance and the current compensation setpoint. Generate control signals; The virtual impedance generation module is used to output a second switching signal from the PWM module according to the control signal during the charging state of the energy storage device. The second switch signal Used to output to the second switching device in the bidirectional DC / DC converter, generating a virtual impedance for the bidirectional DC / DC converter.

6. The control device according to claim 5, characterized in that, In the control signal generation module, the signal is output based on the virtual impedance and the current compensation setpoint. Generate control signals, including: Power reference value of energy storage device Divide by the terminal voltage of the energy storage device Obtain the current reference value of the energy storage device. ; Obtain the virtual impedance output and the current compensation setting value. The processed value and the current reference value Superimposed and then combined with the actual current of the energy storage device The resulting deviation is compared and passed through the transfer function of the current controller. Adjustment, generation of control signals.

7. The control method according to claim 6, characterized in that, The virtual impedance controller is a PI controller, and the current controller... It is a PI controller, and ， ， in , Virtual impedance controllers The proportional coefficient and integral coefficient; , Current controllers The proportional coefficient and integral coefficient; This is the steady-state value of the DC voltage. The inductance value of the energy storage inductor. This is the capacitance value of the output capacitor. This represents the steady-state value of the inductor current. The duty cycle during which the second switching device in the bidirectional DC / DC converter is turned on.

8. The control device according to claim 5, characterized in that, The control device is further configured to: output a first switching signal by the PWM module during the discharge state. The first switch signal Used to output to the base of the first switching device in the bidirectional DC / DC converter.

9. An energy storage converter system, characterized in that, The energy storage converter system includes an energy storage device, a bidirectional DC / DC converter, and an AC / DC grid-connected converter. The bidirectional DC / DC converter is connected between the energy storage device and the DC bus, and the AC / DC grid-connected converter is connected between the DC bus and the power grid. The bidirectional DC / DC converter includes a bidirectional buck-boost circuit, the bidirectional buck-boost circuit includes a first switching device and a second switching device, and the bidirectional DC / DC converter is controlled by the control method as described in any one of claims 1-4.

10. An electronic device, comprising: processor; as well as A memory configured to store computer-executable instructions, which, when executed, use the processor to perform the steps of the control method for the bidirectional DC / DC converter according to any one of claims 1-4.

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