Converter control methods, devices, equipment and media

Abstract

This application discloses a converter control method, device, equipment, and medium, belonging to the field of smart grid technology. An energy storage converter is applied to a three-phase four-wire three-level system. The energy storage converter includes a DC section, an inverter, and an AC section connected in sequence. The AC section is used to connect to the AC grid, and a grid-connected / off-grid switching device is provided on the side of the AC section closest to the AC grid. The DC section includes an energy storage battery and a DC-side filter capacitor connected in sequence. The AC section includes an inverter-side filter inductor, an AC-side filter capacitor, a grid-side filter inductor, and an AC load. The method includes: upon receiving a control command, in response to the control command, determining the operating mode of the energy storage converter. The operating mode is determined based on the operating mode of the energy storage converter, the battery state of the energy storage battery, and the grid-connected power accuracy requirements. The operating mode includes a grid-connected mode and an offline mode. If the operating mode is determined to be the target mode, the DC current control loop of the energy storage converter is disabled, and the grid-connected current reference value of the AC grid is used as the alternative command value of the inner loop controller of the energy storage converter to control the energy storage converter. In this method, the energy storage converter can operate stably according to control commands, smoothly switch off-grid, and accurately control the AC power connected to the grid.

Description

Technical Field

[0001] This application belongs to the field of smart grid technology, and in particular relates to a converter control method, device, equipment and medium. Background Technology

[0002] As a key device connecting energy storage systems to the power grid, the performance of energy storage inverters is crucial to the stability and reliability of the power system. Grid-connected and off-grid energy storage inverters not only need to achieve efficient energy conversion but also need to have the ability to smoothly switch between grid-connected and off-grid modes to adapt to the needs of different operating environments.

[0003] For both grid-connected power control accuracy and the operating status of energy storage batteries during grid-connected operation, grid-connected power accuracy helps achieve efficient and stable operation of the power system, while battery status monitoring and control maintenance helps extend the service life and operational reliability of energy storage converters. However, existing control methods rarely consider both design parameters comprehensively, and generally do not pay much attention to overcharge protection of energy storage batteries.

[0004] Therefore, there is an urgent need to propose a control method for switching between grid-connected and off-grid energy storage converters that comprehensively considers grid-connected power control and integrated battery protection. The energy storage converter can operate stably under different grid command requirements, smoothly switch between grid-connected and off-grid, and accurately control AC grid-connected power. Summary of the Invention

[0005] This application aims to address at least one of the technical problems existing in the prior art. To this end, this application proposes a converter control method, device, equipment, and medium, which enables the energy storage converter to accurately control AC power connected to the grid while operating stably and smoothly switching between grid and off-grid operation according to control commands.

[0006] In a first aspect, this application provides a converter control method applied to a three-phase four-wire three-level energy storage converter. The energy storage converter includes a DC section, an inverter, and an AC section connected in sequence. The AC section is used to connect to the AC power grid, and the AC section is provided with a grid-connected / off-grid switching device on the side close to the AC power grid.

[0007] The DC section includes an energy storage battery and a DC-side filter capacitor connected in sequence, and the AC section includes an inverter-side filter inductor, an AC-side filter capacitor, a grid-side filter inductor, and an AC load.

[0008] The method includes:

[0009] Upon receiving a control command, in response to the control command, the operating mode of the energy storage converter is determined. The operating mode is determined based on the operating mode of the energy storage converter, the battery status of the energy storage battery, and the grid-connected power accuracy requirements. The operating mode includes grid-connected mode and offline mode.

[0010] When the operating mode is determined to be the target mode, the DC current control loop of the energy storage converter is disabled, and the grid-connected current reference value of the AC power grid is used as the alternative command value of the inner loop controller of the energy storage converter to control the energy storage converter.

[0011] According to one embodiment of this application, when the battery state is in the first state, the target mode is the grid-connected current control charging mode;

[0012] When the battery state is in the second state, the target mode is the grid-connected current controlled discharge mode;

[0013] The SOC state of the energy storage battery corresponding to the first state is lower than that of the second state.

[0014] According to one embodiment of this application, when the battery state is the first state and the operating mode is grid-connected mode, after determining the operating mode of the energy storage converter, the method further includes:

[0015] When the operating mode is determined to be constant current charging mode, the DC current reference value i is... bat_ref With DC current feedback value i bat_fb The DC current outer loop controller G of the energy storage converter is then compared and sent to it. ipcs (s), calculate the inner loop alternative instruction value i pcs_CC ;

[0016] Based on the inner ring alternative instruction value i pcs_CC In the inner ring, through the grid-side filter inductor L f2 Current i on L2 Control the grid-connected current;

[0017] When the operating mode is determined to be a pause discharge mode, the DC voltage reference lower limit value V is set. bat_ref_L With DC voltage feedback value v bus_fb The signal is then sent to the DC voltage outer loop controller G after comparison. vinv (s), after limiting processing, the corresponding alternative instruction value i is obtained. inv_CV ;

[0018] Based on the corresponding alternative instruction value i inv_CV It takes over the discharge state of the energy storage battery and suspends the discharge.

[0019] According to one embodiment of this application, when the battery state is the second state, after determining the operating mode of the energy storage converter, the method further includes:

[0020] When the operating mode is determined to be constant voltage charging mode, the upper limit of the DC voltage reference value V is set. bat_ref_H With DC voltage feedback value v bus_fb The DC voltage outer loop controller G of the energy storage converter is then compared and sent to it. vinv (s), after limiting processing, the corresponding alternative instruction value i is obtained. inv_CV ;

[0021] Based on the corresponding alternative instruction value i inv_CV It takes over the charging state of the energy storage battery and filters it through the grid-side filter inductor L in the inner loop. f2 Current i on L2 To achieve regulation and control of grid-connected current;

[0022] When the operating mode is determined to be constant current discharge mode, the DC current reference value i is... bat_ref With DC current feedback value i bat_fb The data is then compared and sent to the DC current outer loop controller G. ipcs (s), calculate the inner loop alternative instruction value i pcs_CC The inner loop is filtered by the grid-side inductor L. f2 Current i on L2 To achieve regulation and control of grid-connected current.

[0023] According to one embodiment of this application, when the operating mode is the offline mode and the battery state is the second state, after determining the operating mode of the energy storage converter, the method further includes:

[0024] When the operating mode is determined to be load voltage control mode, the AC load voltage reference value V is used. Load_ref With feedback value v Load_fb The signal is then sent to the load voltage controller G after comparison. vLoad (s), through the filter capacitor voltage v C Active damping is achieved to obtain the reference modulation signal v under off-grid mode operation. m_inv2 This is to control the load voltage of the AC load.

[0025] According to one embodiment of this application, when the operating mode is the offline mode and the battery state is the first state, after determining the operating mode of the energy storage converter, the method further includes:

[0026] When the operating mode is determined to be the load voltage control mode, the energy storage battery is controlled to stop discharging, and the energy storage converter is controlled to stop working.

[0027] According to one embodiment of this application, upon receiving a control command, before determining the operating mode of the energy storage converter in response to the control command, the method further includes:

[0028] When it is determined that the energy storage converter is switching from grid-connected mode to off-grid mode, the current of the grid-side filter inductor is controlled to 0 by the off-grid mode controller, and the voltage of the AC-side filter capacitor is controlled to track the grid voltage of the AC grid. The grid-connected isolating switch in the grid-connected / off-grid switching device is disconnected, and the energy storage converter is in islanded mode.

[0029] When it is determined that the energy storage converter is switching from off-grid mode to grid-connected mode, the voltage of the AC side filter capacitor is controlled to track the grid voltage of the AC grid through the grid-connected mode controller, and the grid-connected disconnect switch is closed. The energy storage converter is in grid-side filter inductor current control mode.

[0030] Secondly, this application provides a converter control device applied to a three-phase four-wire three-level energy storage converter. The energy storage converter includes a DC section, an inverter, and an AC section connected in sequence. The AC section is used to connect to the AC power grid, and the AC section is provided with a grid-connected / off-grid switching device on the side close to the AC power grid.

[0031] The DC section includes an energy storage battery and a DC-side filter capacitor connected in sequence, and the AC section includes an inverter-side filter inductor, an AC-side filter capacitor, a grid-side filter inductor, and an AC load.

[0032] The device includes:

[0033] The first processing module is used to determine the operating mode of the energy storage converter in response to the control command received. The operating mode is determined based on the operating mode of the energy storage converter, the battery status of the energy storage battery and the grid-connected power accuracy requirements. The operating mode includes grid-connected mode and offline mode.

[0034] The second processing module is used to disable the DC current control loop of the energy storage converter when the working mode is determined to be the target mode, and to use the grid-connected current reference value of the AC power grid as the alternative command value of the inner loop controller of the energy storage converter to control the energy storage converter.

[0035] Thirdly, this application provides an electronic device including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the converter control method as described in the first aspect above.

[0036] Fourthly, this application provides a non-transitory computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the converter control method as described in the first aspect above.

[0037] Fifthly, this application provides a chip including a processor and a communication interface, the communication interface being coupled to the processor, the processor being used to run programs or instructions to implement the converter control method as described in the first aspect.

[0038] In a sixth aspect, this application provides a computer program product, including a computer program that, when executed by a processor, implements the converter control method as described in the first aspect above.

[0039] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application.

[0040] The converter control method, apparatus, equipment, and medium provided in this application have the following advantages over the prior art:

[0041] (1) The working mode is generated by the operating mode, battery status and grid-connected power accuracy requirements to flexibly adapt to different operating conditions. The DC current control loop is disabled, and the active adjustment of DC current is changed to the adjustment of AC grid-connected power. This avoids the interference of battery status on grid-connected power accuracy and ensures that the energy storage converter can work stably according to the actual needs based on the control command. On the basis of smooth grid-connected and off-grid switching, the AC grid-connected power is accurately controlled. It is not only applicable to grid-connected and off-grid energy storage converters, but the grid-connected mode controller and the off-grid mode controller can also be used separately for grid-connected and off-grid energy storage converters.

[0042] (2) On the basis of achieving smooth switching between grid-connected and islanded working modes of energy storage converter, the method also takes into account the precise control of grid-connected power and the charging and discharging protection of energy storage battery, which has high operational reliability and effectively extends the service life of energy storage battery. At the same time, the control strategy of this application is simple and has low complexity, and is easy to implement in digital control. When the battery management system fails, this method can provide certain support for the reliable operation of DC side energy storage battery. Attached Figure Description

[0043] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0044] Figure 1 This is a schematic diagram of the on-grid and off-grid energy storage converter structure provided in the embodiments of this application;

[0045] Figure 2This is a topology diagram of a three-phase four-wire T-type three-level energy storage converter provided in the embodiments of this application;

[0046] Figure 3 This is a schematic flowchart of the converter control method provided in the embodiments of this application;

[0047] Figure 4 This is a schematic diagram of the grid-connected energy storage converter provided in the embodiments of this application in grid-connected mode;

[0048] Figure 5 This is a schematic diagram of the state of the grid-connected and off-grid energy storage converter in off-grid mode provided in the embodiments of this application;

[0049] Figure 6 This is a DC-side waveform diagram of the dynamic switching process from grid-connected current control discharge mode to grid-connected current control charging mode when the grid-connected power control accuracy is provided in the embodiments of this application.

[0050] Figure 7 This is an AC side waveform diagram of the dynamic switching process from grid-connected current control discharge mode to grid-connected current control charging mode when the grid-connected power control accuracy is provided in the embodiments of this application.

[0051] Figure 8 This is a waveform diagram of the DC side during the dynamic switching process from constant current discharge mode to constant current charging mode when controlling the DC side energy storage battery current size according to the embodiments of this application.

[0052] Figure 9 This is an AC side waveform diagram during the dynamic switching process from constant current discharge mode to constant current charging mode when controlling the DC side energy storage battery current, as provided in the embodiments of this application.

[0053] Figure 10 This is the DC-side steady-state operating waveform of the energy storage converter connected to the grid when the energy storage battery has a high SOC, as provided in the embodiments of this application.

[0054] Figure 11 This is the steady-state operating waveform of the AC side of the energy storage converter connected to the grid when the energy storage battery has a high SOC, as provided in the embodiments of this application.

[0055] Figure 12 This is the DC-side steady-state operating waveform of the energy storage converter when the SOC of the energy storage battery is low, as provided in the embodiments of this application.

[0056] Figure 13 This is the steady-state operating waveform of the AC side of the energy storage converter connected to the grid when the SOC of the energy storage battery is low, as provided in the embodiments of this application.

[0057] Figure 14 This is a schematic diagram of the structure of the electronic device provided in the embodiments of this application. Detailed Implementation

[0058] The technical solutions of the embodiments of this application will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application are within the scope of protection of this application.

[0059] The terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and not to describe a specific order or sequence. It should be understood that such use of data can be interchanged where appropriate so that embodiments of this application can be implemented in orders other than those illustrated or described herein, and the objects distinguished by "first," "second," etc., are generally of the same class and the number of objects is not limited; for example, a first object can be one or more. Furthermore, in the specification and claims, "and / or" indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.

[0060] The converter control method, converter control device, electronic device, and readable storage medium provided in this application will be described in detail below with reference to the accompanying drawings and through specific embodiments and application scenarios.

[0061] The converter control method can be applied to the terminal, and can be executed by the hardware or software in the terminal.

[0062] The terminal includes, but is not limited to, portable communication devices such as mobile phones or tablets with touch-sensitive surfaces (e.g., touchscreen displays and / or touchpads). It should also be understood that, in some embodiments, the terminal may not be a portable communication device, but rather a desktop computer with touch-sensitive surfaces (e.g., touchscreen displays and / or touchpads).

[0063] The following embodiments describe a terminal including a display and a touch-sensitive surface. However, it should be understood that the terminal may include one or more other physical user interface devices such as a physical keyboard, mouse, and joystick.

[0064] The converter control method provided in this application embodiment can be executed by an electronic device or a functional module or entity in an electronic device that can implement the converter control method. The electronic devices mentioned in this application embodiment include, but are not limited to, mobile phones, tablets, computers, cameras, and wearable devices. The converter control method provided in this application embodiment will be described below using an electronic device as the execution subject.

[0065] like Figure 1As shown, this method is applied to a three-phase four-wire three-level energy storage converter. The energy storage converter includes a DC section, an inverter, and an AC section connected in sequence. The AC section is used to connect to the AC power grid, and the AC section is equipped with a grid-connected / off-grid switching device on the side closest to the AC power grid.

[0066] The DC section includes an energy storage battery and a DC-side filter capacitor connected in sequence, and the AC section includes an inverter-side filter inductor, an AC-side filter capacitor, a grid-side filter inductor, and an AC load.

[0067] DC-side filter capacitors include C bus1 C bus2 Inverter-side filter inductor L f1 Including L f1a L f1b L f1c Neutral inductance L f1n AC side filter capacitor C f Including C fa C fb C fc Grid-side filter inductor L f2 Including L f2a L f2b L f2c The AC loads include Load_fa, Load_fb, and Load_fc.

[0068] exist Figure 1 In the diagram, the energy storage converter is of the grid-connected / off-grid type, including the main circuit and the control circuit. The gray box below shows the block diagram of the control strategy proposed in this application. Figure 2 As shown, the core part of the energy storage converter in the main circuit is a three-phase four-wire T-type three-level structure.

[0069] Figure 2 The main parameters are shown in Table 1 below:

[0070] Table 1 Main Parameters

[0071] AC side load output voltage <![CDATA[V Load_ref ]]> 230V(RMS) The switching frequency of the three-phase inverter <![CDATA[f s ]]> 15kHz Output frequency <![CDATA[f o ]]> 50Hz Inverter-side filter inductor <![CDATA[L f1 ]]> 62.7μH Grid-side filter inductor <![CDATA[L f2 ]]> 18.5μH Neutral inductor <![CDATA[L fn ]]> 43.4μH Filter capacitor <![CDATA[C f ]]> 100μF DC-side split capacitor <![CDATA[C bus1 ,C bus2 ]]> 6900μF Energy storage battery operating voltage range / 790V~864V DC side voltage reference upper limit <![CDATA[V bat_ref_H ]]> 864V DC side voltage reference lower limit <![CDATA[V bat_ref_L ]]> 790V

[0072] like Figure 3 As shown, the converter control method includes:

[0073] Step 310: Upon receiving a control command, in response to the control command, determine the operating mode of the energy storage converter. The operating mode is determined based on the operating mode of the energy storage converter, the battery status of the energy storage battery, and the grid-connected power accuracy requirements. The operating mode includes grid-connected mode and offline mode.

[0074] Step 320: When the operating mode is determined to be the target mode, the DC current control loop of the energy storage converter is disabled, and the grid-connected current reference value of the AC power grid is used as the alternative command value of the inner loop controller of the energy storage converter to control the energy storage converter.

[0075] The battery status can be characterized as SOC status, and the inverter is a three-phase four-wire T-type three-level energy storage converter.

[0076] When grid-connected power accuracy requirements are high, the operating mode is the target mode.

[0077] In some embodiments, before determining the operating mode of the energy storage converter in response to a control command received, the method further includes:

[0078] When it is determined that the energy storage converter is switching from grid-connected mode to off-grid mode, the current of the grid-side filter inductor is controlled to 0 by the off-grid mode controller, and the voltage of the AC-side filter capacitor is controlled to track the grid voltage of the AC grid. The grid-connected isolating switch in the grid-connected / off-grid switching device is disconnected, and the energy storage converter is in islanded mode.

[0079] When it is determined that the energy storage converter is switching from off-grid mode to grid-connected mode, the voltage of the AC side filter capacitor is controlled to track the grid voltage of the AC grid through the grid-connected mode controller, and the grid-connected disconnect switch is closed. The energy storage converter is in grid-side filter inductor current control mode.

[0080] When the energy storage converter is required to actively switch from grid-connected mode to offline mode, the grid-side filter inductor L is first switched via the off-grid mode controller. f2 Current i on L2 The control value is set to 0, and then the AC side filter capacitor voltage V is controlled. c Tracking grid voltage v g Finally, the control and off-grid switching device disconnects the grid-connected isolating switch and switches to islanded operation mode.

[0081] When the energy storage converter is required to actively switch from off-grid mode to grid-connected mode, the AC side filter capacitor voltage V is first controlled by the grid-connected mode controller. c Tracking grid voltage v g Then, close the grid-connected isolating switch; finally, control the grid-connected / off-grid switching device to switch to the grid-side filter inductor L. f2 Current control mode.

[0082] After the off-grid switching device performs the switching, the controller receives the control command from the upper layer and performs the control corresponding to the working mode.

[0083] In actual implementation, the DC current feedback value i is obtained through multi-channel sampling. bat_fb DC bus voltage v bus_fb AC side filter capacitor voltage v C Current i C The current i of the grid-side filter inductor L2_fb AC load voltage feedback value v Load_fb The sampled values ​​are sent to the controller designed in this method to realize various modes and functions of the on-grid and off-grid energy storage converter.

[0084] Adjust the position of control switch S1 or S2 according to different requirements for grid-connected power control accuracy and DC current reference value control;

[0085] The sampled values ​​are sent to the outer loop controller of the corresponding mode to calculate the corresponding command value. In particular, in the grid-connected mode, the switch S3 can be adjusted to the corresponding position according to the different charging and discharging states.

[0086] The energy storage converter is switched to a specific grid-connected or off-grid mode by the AC side switch control strategy. The grid-connected mode sends the command value to the corresponding inner loop controller, while the off-grid mode directly outputs the single-loop calculated value to obtain the modulation signal.

[0087] In some embodiments, when the battery state is in the first state, the target mode is the grid-connected current control charging mode.

[0088] When the battery state is in the second state, the target mode is the grid-connected current controlled discharge mode;

[0089] The SOC state of the energy storage battery corresponding to the first state is lower than that of the second state.

[0090] According to the converter control method provided in the embodiments of this application, the operating mode is generated by the operating mode, battery status and grid-connected power accuracy requirements to flexibly adapt to different operating conditions. The DC current control loop is disabled, and the active adjustment of DC current is changed to the adjustment of AC grid-connected power. This avoids the interference of battery status on grid-connected power accuracy, ensures that the energy storage converter can work stably according to the actual needs based on the control command, and accurately control the AC grid-connected power on the basis of smooth grid-connected and off-grid switching. It is not only applicable to grid-connected and off-grid energy storage converters, but the grid-connected mode controller and the off-grid mode controller can also be used independently for grid-connected and off-grid energy storage converters respectively.

[0091] In some embodiments, when the battery state is the first state and the operating mode is grid-connected mode, after determining the operating mode of the energy storage converter, the method further includes:

[0092] When the operating mode is determined to be constant current charging mode, the DC current reference value I is...bat_ref With DC current feedback value i bat_fb The DC current outer loop controller G of the energy storage converter is then compared and sent to it. ipcs (s), calculate the inner loop alternative instruction value i pcs_CV ;

[0093] Based on the inner ring alternative instruction value i pcs_CV In the inner ring, through the grid-side filter inductor L f2 Current i on L2 Control the grid-connected current;

[0094] When the operating mode is determined to be a pause discharge mode, the DC voltage reference lower limit value V is set. bat_ref_L With DC voltage feedback value v bus_fb The signal is then sent to the DC voltage outer loop controller G after comparison. vinv (s), after limiting processing, the corresponding alternative instruction value i is obtained. inv_CV ;

[0095] Based on the corresponding alternative instruction value i inv_CV It takes over the discharge state of the energy storage battery and suspends the discharge.

[0096] In some embodiments, when the battery state is the second state, after determining the operating mode of the energy storage converter, the method further includes:

[0097] When the operating mode is determined to be constant voltage charging mode, the upper limit of the DC voltage reference value V is set. bat_ref_H With DC voltage feedback value v bus_fb The DC voltage outer loop controller G of the energy storage converter is then compared and sent to it. vinv (s), after limiting processing, the corresponding alternative instruction value i is obtained. inv_CV ;

[0098] Based on the corresponding alternative instruction value i inv_CV It takes over the charging state of the energy storage battery and filters it through the grid-side filter inductor L in the inner loop. f2 Current i on L2 To achieve regulation and control of grid-connected current;

[0099] When the operating mode is determined to be constant current discharge mode, the DC current reference value i is... bat_ref With DC current feedback value i bat_fb The data is then compared and sent to the DC current outer loop controller G. ipcs (s), calculate the inner loop alternative instruction value i pcs_CC The inner loop is connected to the grid-side filter inductor L. f2 Current i on L2 To achieve regulation and control of grid-connected current.

[0100] In some embodiments, when the operating mode is the offline mode and the battery state is the second state, after determining the operating mode of the energy storage converter, the method further includes:

[0101] When the operating mode is determined to be load voltage control mode, the AC load voltage reference value V is used. Load_ref With feedback value v Load_fb The signal is then sent to the load voltage controller G after comparison. vLoad (s), through the filter capacitor voltage v C Active damping is achieved to obtain the reference modulation signal v under off-grid mode operation. m_inv2 This is to control the load voltage of the AC load.

[0102] Among them, H v1 This is the capacitor voltage feedback coefficient.

[0103] In some embodiments, when the operating mode is the offline mode and the battery state is a first state, after determining the operating mode of the energy storage converter, the method further includes:

[0104] When the operating mode is determined to be the load voltage control mode, the energy storage battery is controlled to stop discharging, and the energy storage converter is controlled to stop working.

[0105] In this embodiment, a three-phase four-wire three-level topology is used as the basic carrier of the grid-connected and off-grid energy storage converter. The working mode of the energy storage converter can be smoothly switched according to different requirements such as the AC side grid-connected power accuracy and the DC side energy storage battery current, so that the energy storage converter can work stably in any working mode.

[0106] In this embodiment, the energy storage converter can operate in any of the following modes: grid-connected mode with six operating modes and offline mode with two islanded operating modes, depending on the current state and demand. It can also improve the accuracy of grid-connected power control while achieving smooth switching between grid connection and off-grid operation, and enhance the health monitoring and protection of the energy storage battery.

[0107] Instead of implementing protection functions through the internal structure management and design of the battery, the battery health monitoring is achieved indirectly through external control strategies, which helps to simplify battery design.

[0108] The first state indicates that the SOC state of the energy storage battery is low, for example, the energy storage battery's charge is less than 20%.

[0109] The second state indicates that the energy storage battery has a high state of charge (SOC), for example, the energy storage battery has a charge level greater than 80%.

[0110] like Figure 4 He Ru Figure 5 As shown, the switchable operating modes of the grid-connected mode specifically include:

[0111] Constant current charging mode. When the energy storage battery's SOC is low, the DC current reference value i is used for charging. bat_ref With DC current feedback value i bat_fb The data is then compared and sent to the DC current outer loop controller G. ipcs (s), calculate the inner loop alternative instruction value i pcs_CC The inner loop is connected to the grid-side filter inductor L. f2 Current i on L2 To achieve regulation and control of grid-connected current.

[0112] Constant voltage charging mode. When the energy storage battery has a high SOC, the DC voltage is charged by referencing the upper limit value V. bat_ref_H With DC voltage feedback value v bus_fb The signal is then sent to the DC voltage outer loop controller G after comparison. vinv (s), after limiting processing, the corresponding alternative instruction value i is obtained. inv_CV This is to manage the battery's charging status and protect it using trickle charging. The inner loop uses a grid-side filter inductor L. f2 Current i on L2 To achieve regulation and control of grid-connected current.

[0113] Grid-connected current control charging mode. When there are strict requirements for grid-connected power accuracy and the energy storage battery's SOC is low, switching to this mode disables the DC current control loop and directly sets the grid-connected current reference value i. g_ref As an alternative instruction value for the inner loop controller.

[0114] Constant current discharge mode. When the energy storage battery has a high SOC, the DC current reference value i is used. bat_ref With DC current feedback value i bat_fb The data is then compared and sent to the DC current outer loop controller G. ipcs (s), calculate the inner loop alternative instruction value i pcs_CC The inner loop is connected to the grid-side filter inductor L. f2 Current i on L2 To achieve regulation and control of grid-connected current.

[0115] Discharge pause mode. When the energy storage battery's SOC is low, it cannot continue discharging and will discharge via a DC voltage reference lower limit V. bat_ref_L With DC voltage feedback value v bus_fb The signal is then sent to the DC voltage outer loop controller G after comparison. vinv (s), after limiting processing, the corresponding alternative instruction value i is obtained. inv_CV This is used to take over the battery's discharge state to protect the battery and stop the discharge.

[0116] Grid-connected current control discharge mode. When there are strict requirements for grid-connected power accuracy and the energy storage battery has a high SOC, switching to this mode disables the DC current control loop and directly sets the grid-connected current reference value i. g_ref As an alternative instruction value for the inner loop controller.

[0117] Depending on the different requirements for grid-connected power accuracy or the charging current of the energy storage battery, the system can smoothly switch between grid-connected current control charging mode and constant current charging mode by controlling switch S1.

[0118] Depending on the different requirements for grid-connected power accuracy or the magnitude of energy storage battery discharge current, the system can smoothly switch between grid-connected current control discharge mode and constant current discharge mode by controlling switch S2.

[0119] When the energy storage converter is connected to the grid for charging, if grid-connected power accuracy is required, the grid-connected current reference value i is used. g_ref And the alternative command value i calculated by the outer loop of the constant voltage charging mode control inv_CV The larger of these values ​​is used as the inner loop current i. L2 The reference value for control; if the focus is on battery charging current, the alternative command value i is calculated by the outer loop of the constant current charging mode and constant voltage charging mode control. pcs_CC and i inv_CV The larger value in the middle is used as the inner loop current i L2 Reference values ​​for control.

[0120] When the energy storage converter is discharging while connected to the grid, if grid power accuracy is required, the grid current reference value i is used. g_ref And the alternative command value i calculated by the outer loop of the constant voltage discharge mode control inv_CV The smaller value among them is taken as the inner loop current i L2 The reference value for control; if the focus is on battery charging current, the alternative command value i is calculated by the outer loop of the constant current discharge mode and constant voltage discharge mode control. pcs_CC and i inv_CV The smaller value in the middle is used as the inner loop current i L2 Reference values ​​for control.

[0121] In the inner-loop control of the grid-connected mode, the current i calculated by the outer loop is... L2 Reference value i L2_ref The feedback value i obtained from sampling L2_fb The two are compared, and the error value of the comparison is sent to the inner loop current controller G. iL2 (s) and through the filter capacitor current i C Achieving active damping (H i1 (where the capacitor current feedback coefficient is used) to obtain the reference modulation signal v under grid-connected mode operation. m_inv1 .

[0122] The switchable working modes in offline mode specifically include:

[0123] Load voltage control mode. When the energy storage battery has a high SOC, the AC load voltage reference value V is used. Load_ref With feedback value v Load_fb The signal is then sent to the load voltage controller G after comparison. vLoad (s), through the filter capacitor voltage v C Active damping is achieved to obtain the reference modulation signal v under off-grid mode operation. m_inv2 This enables precise control of the load voltage.

[0124] Discharge Stop Mode. When the SOC of the energy storage battery is low, the battery stops discharging, and the energy storage converter stops working, which is an abnormal operating state.

[0125] like Figure 6 and Figure 7 As shown, when grid-connected power control accuracy is required, the waveform of the energy storage converter during the dynamic switching process from grid-connected current control discharge mode to grid-connected current control charging mode is displayed.

[0126] Figure 6 This refers to the state of charge (SOC) of the energy storage battery under dynamic conditions, and the DC-side current i. bat DC bus voltage v bus The working waveform.

[0127] Figure 7 It corresponds to the grid-side filter inductor L. f2 Current i L2x and output voltage v ox The waveform.

[0128] The charge / discharge switching process is continuous and smooth, L f2 The inductor current waveform has good quality, and the current amplitude can be stabilized at the reference value of 200A, thus achieving precise control of grid-connected power.

[0129] like Figure 8 and Figure 9 As shown, the control method of this application embodiment shows the working waveform of the energy storage converter during the dynamic switching process from constant current discharge mode to constant current charging mode when it is required to control the current of the DC side energy storage battery.

[0130] Figure 8 This refers to the state of charge (SOC) of the energy storage battery under dynamic conditions, and the DC-side current i. bat DC bus voltage v bus The working waveform.

[0131] Figure 9 It corresponds to the grid-side filter inductor L. f2 Current i L2x and output voltage vox The waveform.

[0132] It can be observed that the charging and discharging switching process is continuous and smooth, the L2 inductor current waveform has good quality, and the DC side current control is stable.

[0133] like Figure 10 and Figure 11 The figure shows the grid-connected steady-state operating waveform of the energy storage converter when the DC-side energy storage battery SOC is high, in order to verify the extended protection function.

[0134] Figure 10 The state of charge (SOC) and DC-side current (i) of the energy storage battery after reaching steady state are... bat DC bus voltage v bus The working waveform.

[0135] Figure 11 It corresponds to the grid-side filter inductor L. f2 Current i L2x and output voltage v ox The waveform.

[0136] The energy storage battery's SOC (%) is set to be relatively high, and the controller's grid-connected current reference value is -110A, indicating a tendency for the AC side to charge the energy storage converter. The effectiveness of the constant voltage control loop is determined by measuring the DC-side battery charging current and battery voltage. If the DC-side charging current is very small, not the set reference value, and the battery voltage is stable at the upper reference limit, then the effectiveness of this control method is proven. When the battery SOC is high, the DC-side voltage control loop provides extended protection for the battery through trickle charging.

[0137] like Figure 12 and Figure 13 The figure shows the grid-connected steady-state operating waveform of the energy storage converter when the DC-side energy storage battery SOC is low, in order to verify the over-discharge protection function.

[0138] Figure 12 The state of charge (SOC) and DC-side current (i) of the energy storage battery after reaching steady state are... bat DC bus voltage v bus The working waveform.

[0139] Figure 13 It corresponds to the grid-side filter inductor L. f2 Current i L2x and output voltage v ox The waveform.

[0140] The energy storage battery's SOC (%) is set to a low level, and the controller's grid-connected current reference value is 110A, indicating a tendency for the energy storage converter to discharge to the grid. The effectiveness of the constant voltage control loop is determined by measuring the DC-side battery discharge current and battery voltage. If the DC-side discharge current is very small, not the set reference value, and the battery voltage remains stable at the lower reference limit, the effectiveness of this control method is proven. When the battery SOC is low, the DC-side voltage control loop provides over-discharge protection, pausing the discharge process.

[0141] In this embodiment, in addition to achieving smooth switching between grid-connected and islanded operating modes of the energy storage converter, it also comprehensively considers the precise control of grid-connected power and the charging and discharging protection of the energy storage battery, which has high operational reliability and effectively extends the service life of the energy storage battery. At the same time, the control strategy of this application is simple and has low complexity, making it easy to implement in digital control. When the battery management system (BMS) fails, this method can provide certain support for the reliable operation of the DC-side energy storage battery.

[0142] The converter control method provided in this application can be executed by a converter control device. This application uses the example of a converter control device executing the converter control method to illustrate the converter control device provided in this application.

[0143] This application embodiment also provides a converter control device applied to a three-phase four-wire three-level energy storage converter. The energy storage converter includes a DC section, an inverter, and an AC section connected in sequence. The AC section is used to connect to the AC power grid, and the AC section is provided with a grid-connected / off-grid switching device on the side close to the AC power grid.

[0144] The DC section includes an energy storage battery and a DC-side filter capacitor connected in sequence, and the AC section includes an inverter-side filter inductor, an AC-side filter capacitor, a grid-side filter inductor, and an AC load.

[0145] The converter control device includes:

[0146] The first processing module is used to determine the operating mode of the energy storage converter in response to the control command received. The operating mode is determined based on the operating mode of the energy storage converter, the battery status of the energy storage battery and the grid-connected power accuracy requirements. The operating mode includes grid-connected mode and offline mode.

[0147] The second processing module is used to disable the DC current control loop of the energy storage converter when the working mode is determined to be the target mode, and to use the grid-connected current reference value of the AC power grid as the alternative command value of the inner loop controller of the energy storage converter to control the energy storage converter.

[0148] According to the converter control device provided in the embodiments of this application, the operating mode is generated by the operating mode, battery status and grid-connected power accuracy requirements to flexibly adapt to different operating conditions. The DC current control loop is disabled, and the active adjustment of DC current is changed to the adjustment of AC grid-connected power. This avoids the interference of battery status on grid-connected power accuracy, ensures that the energy storage converter can work stably according to the actual needs according to the control command, and accurately control the AC grid-connected power on the basis of smooth grid-connected and off-grid switching. It is not only applicable to grid-connected and off-grid energy storage converters, but the grid-connected mode controller and the off-grid mode controller can also be used independently for grid-connected and off-grid energy storage converters respectively.

[0149] The converter control device in this application embodiment can be an electronic device or a component within an electronic device, such as an integrated circuit or a chip. The electronic device can be a terminal or other devices besides a terminal. For example, the electronic device can be a mobile phone, tablet computer, laptop computer, PDA, in-vehicle electronic device, mobile internet device (MID), augmented reality (AR) / virtual reality (VR) device, robot, wearable device, ultra-mobile personal computer (UMPC), netbook, or personal digital assistant (PDA), etc. It can also be a server, network attached storage (NAS), personal computer (PC), television (TV), ATM, or self-service machine, etc. This application embodiment does not specifically limit the scope of the device.

[0150] The converter control device in this application embodiment can be a device with an operating system. This operating system can be Android, iOS, or other possible operating systems; this application embodiment does not specifically limit the specific operating system used.

[0151] The converter control device provided in this application embodiment can realize the various processes implemented in the converter control method embodiment as described above. To avoid repetition, it will not be described again here.

[0152] In some embodiments, such as Figure 14As shown, this application embodiment also provides an electronic device 1400, including a processor 1401, a memory 1402, and a computer program stored in the memory 1402 and executable on the processor 1401. When the program is executed by the processor 1401, it implements the various processes of the above-described converter control method embodiment and can achieve the same technical effect. To avoid repetition, it will not be described again here.

[0153] It should be noted that the electronic devices in the embodiments of this application include the mobile electronic devices and non-mobile electronic devices described above.

[0154] This application also provides a non-transitory computer-readable storage medium storing a computer program. When the computer program is executed by a processor, it implements the various processes of the above-described converter control method embodiments and achieves the same technical effect. To avoid repetition, it will not be described again here.

[0155] The processor is the processor in the electronic device described in the above embodiments. The readable storage medium includes computer-readable storage media, such as computer read-only memory (ROM), random access memory (RAM), magnetic disk, or optical disk.

[0156] This application also provides a computer program product, including a computer program that, when executed by a processor, implements the above-described converter control method.

[0157] The processor is the processor in the electronic device described in the above embodiments. The readable storage medium includes computer-readable storage media, such as computer read-only memory (ROM), random access memory (RAM), magnetic disk, or optical disk.

[0158] This application embodiment also provides a chip, which includes a processor and a communication interface. The communication interface and the processor are coupled. The processor is used to run programs or instructions to implement the various processes of the above-described converter control method embodiments and can achieve the same technical effect. To avoid repetition, it will not be described again here.

[0159] It should be understood that the chip mentioned in the embodiments of this application may also be referred to as a system-on-a-chip, system chip, chip system, or system-on-a-chip, etc.

[0160] It should be noted that, in this document, 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 limitations, 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 that element. Furthermore, it should be noted that the scope of the methods and apparatuses in the embodiments of this application is not limited to performing functions in the order shown or discussed, but may also include performing functions substantially simultaneously or in the reverse order, depending on the functions involved. For example, the described methods may be performed in a different order than described, and various steps may be added, omitted, or combined. Additionally, features described with reference to certain examples may be combined in other examples.

[0161] Through the above description of the embodiments, those skilled in the art can clearly understand that the methods of the above embodiments can be implemented by means of software plus necessary general-purpose hardware platforms. Of course, they can also be implemented by hardware, but in many cases the former is a better implementation method. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, can be embodied in the form of a computer software product. This computer software product is stored in a storage medium (such as ROM / RAM, magnetic disk, optical disk) and includes several instructions to cause a terminal (which may be a mobile phone, computer, server, or network device, etc.) to execute the converter control methods of the various embodiments of this application.

[0162] In the description of this application, "first feature" and "second feature" may include one or more of the features.

[0163] In the description of this application, "multiple" means two or more.

[0164] The embodiments of this application have been described above with reference to the accompanying drawings. However, this application is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of this application without departing from the spirit and scope of the claims, and all of these forms are within the protection scope of this application.

[0165] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0166] Although embodiments of this application have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the claims and their equivalents.

Claims

1. A converter control method, characterized in that, An energy storage converter is applied to a three-phase four-wire three-level system. The energy storage converter includes a DC section, an inverter, and an AC section connected in sequence. The AC section is used to connect to the AC power grid. The AC section is equipped with a grid-connected / off-grid switching device on the side closest to the AC power grid. The DC section includes an energy storage battery and a DC-side filter capacitor connected in sequence, and the AC section includes an inverter-side filter inductor, an AC-side filter capacitor, a grid-side filter inductor, and an AC load. The method includes: Upon receiving a control command, in response to the control command, the operating mode of the energy storage converter is determined. The operating mode is determined based on the operating mode of the energy storage converter, the battery status of the energy storage battery, and the grid-connected power accuracy requirements. The operating mode includes grid-connected mode and offline mode. When the operating mode is determined to be the target mode, the DC current control loop of the energy storage converter is disabled, and the grid-connected current reference value of the AC power grid is used as the alternative command value of the inner loop controller of the energy storage converter to control the energy storage converter. When the battery is in the first state, the target mode is the grid-connected current control charging mode; When the battery state is in the second state, the target mode is the grid-connected current controlled discharge mode; The SOC state of the energy storage battery corresponding to the first state is lower than that of the second state; When the battery state is the first state and the operating mode is grid-connected mode, after determining the operating mode of the energy storage converter, the method further includes: When the operating mode is determined to be constant current charging mode, the DC current reference value is... i bat_ref With DC current feedback value i bat_fb The compared data is then sent to the DC current outer loop controller of the energy storage converter. G ipcs ( s ), calculate the inner loop alternative command value i pcs_CC ; Based on the inner ring alternative instruction value i pcs_CC In the inner ring, through the grid-side filter inductor L f2 Current on i L2 Control the grid-connected current; If the operating mode is determined to be a pause discharge mode, the DC voltage reference lower limit value will be set. V bat_ref_L With DC voltage feedback value v bus_fb The signal is then sent to the DC voltage outer loop controller after comparison. G vinv ( s After amplitude limiting, the corresponding alternative instruction values ​​are obtained. i inv_CV ; Based on the corresponding alternative instruction values i inv_CV It takes over the discharge state of the energy storage battery and suspends the discharge.

2. The converter control method according to claim 1, characterized in that, When the battery state is the second state, after determining the operating mode of the energy storage converter, the method further includes: If the operating mode is determined to be constant voltage charging mode, the upper limit of the DC voltage reference value will be set. V bat_ref_H With DC voltage feedback value v bus_fb The compared values ​​are then sent to the DC voltage outer loop controller of the energy storage converter. G vinv ( s After amplitude limiting, the corresponding alternative instruction values ​​are obtained. i inv_CV ; Based on the corresponding alternative instruction values i inv_CV It takes over the charging status of the energy storage battery and filters it through the grid-side filter inductor in the inner loop. L f2 Current on i L2 To achieve regulation and control of grid-connected current; When the operating mode is determined to be constant current discharge mode, the DC current reference value is... i bat_ref With DC current feedback value i bat_fb The data is then compared and sent to the DC current outer loop controller. G ipcs ( s ), calculate the inner loop alternative command value i pcs_CC The inner ring is filtered by the grid-side inductor. L f2 Current on i L2 To achieve regulation and control of grid-connected current.

3. The converter control method according to claim 1, characterized in that, When the operating mode is the offline mode and the battery state is the second state, after determining the operating mode of the energy storage converter, the method further includes: When the operating mode is determined to be load voltage control mode, the AC load voltage reference value is used. V Load_ref With feedback value v Load_fb The signal is then sent to the load voltage controller after comparison. G vLoad ( s ), through the filter capacitor voltage v C Active damping is implemented to obtain the reference modulation signal for off-grid operation. v m_inv2 This is to control the load voltage of the AC load.

4. The converter control method according to claim 1, characterized in that, When the operating mode is the offline mode and the battery state is the first state, after determining the operating mode of the energy storage converter, the method further includes: When the operating mode is determined to be the load voltage control mode, the energy storage battery is controlled to stop discharging, and the energy storage converter is controlled to stop working.

5. The converter control method according to claim 1, characterized in that, Upon receiving a control command, before determining the operating mode of the energy storage converter in response to the control command, the method further includes: When it is determined that the energy storage converter is switching from grid-connected mode to off-grid mode, the current of the grid-side filter inductor is controlled to 0 by the off-grid mode controller, and the voltage of the AC-side filter capacitor is controlled to track the grid voltage of the AC grid. The grid-connected isolating switch in the grid-connected / off-grid switching device is disconnected, and the energy storage converter is in islanded mode. When it is determined that the energy storage converter is switching from off-grid mode to grid-connected mode, the voltage of the AC side filter capacitor is controlled to track the grid voltage of the AC grid through the grid-connected mode controller, and the grid-connected disconnect switch is closed. The energy storage converter is in grid-side filter inductor current control mode.

6. A converter control device, characterized in that, An energy storage converter is applied to a three-phase four-wire three-level system. The energy storage converter includes a DC section, an inverter, and an AC section connected in sequence. The AC section is used to connect to the AC power grid. The AC section is equipped with a grid-connected / off-grid switching device on the side closest to the AC power grid. The DC section includes an energy storage battery and a DC-side filter capacitor connected in sequence, and the AC section includes an inverter-side filter inductor, an AC-side filter capacitor, a grid-side filter inductor, and an AC load. The device comprises: The first processing module is used to determine the operating mode of the energy storage converter in response to the control command received. The operating mode is determined based on the operating mode of the energy storage converter, the battery status of the energy storage battery and the grid-connected power accuracy requirements. The operating mode includes grid-connected mode and offline mode. The second processing module is used to disable the DC current control loop of the energy storage converter when the working mode is determined to be the target mode, and to use the grid-connected current reference value of the AC grid as the alternative command value of the inner loop controller of the energy storage converter to control the energy storage converter. When the battery is in the first state, the target mode is the grid-connected current control charging mode; When the battery state is in the second state, the target mode is the grid-connected current controlled discharge mode; The SOC state of the energy storage battery corresponding to the first state is lower than that of the second state; When the battery state is the first state and the operating mode is grid-connected mode, after determining the operating mode of the energy storage converter, the method further includes: When the operating mode is determined to be constant current charging mode, the DC current reference value is... i bat_ref With DC current feedback value i bat_fb The compared data is then sent to the DC current outer loop controller of the energy storage converter. G ipcs ( s ), calculate the inner loop alternative command value i pcs_CC ; Based on the inner ring alternative instruction value i pcs_CC In the inner ring, through the grid-side filter inductor L f2 Current on i L2 Control the grid-connected current; If the operating mode is determined to be a pause discharge mode, the DC voltage reference lower limit value will be set. V bat_ref_L With DC voltage feedback value v bus_fb The signal is then sent to the DC voltage outer loop controller after comparison. G vinv ( s After amplitude limiting, the corresponding alternative instruction values ​​are obtained. i inv_CV ; Based on the corresponding alternative instruction values i inv_CV It takes over the discharge state of the energy storage battery and suspends the discharge.

7. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the converter control method as described in any one of claims 1-5.

8. A non-transitory computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the converter control method as described in any one of claims 1-5.

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