Converter control method, device, equipment and medium

Abstract

The invention discloses a converter control method, device and equipment and a medium, and belongs to the technical field of intelligent power grids. The method is applied to a three-phase four-wire three-level energy storage converter, the energy storage converter comprises a direct current part, an inverter and an alternating current part which are connected in sequence, the alternating current part is used for being connected with an alternating current power grid, and a grid-connected and off-grid switching device is arranged on the side, close to the alternating current power grid, of the alternating current part; the direct current part comprises an energy storage battery and a direct current side filter capacitor which are connected in sequence; the alternating current part comprises an inverter side filter inductor, an alternating current side filter capacitor, a network side filter inductor and an alternating current load; the method comprises the steps that under the condition that a control instruction is received, in response to the control instruction, the working mode of the energy storage converter is determined, the working mode is determined based on the operation mode of the energy storage converter, the battery state of an energy storage battery and the grid-connected power precision requirement, and the operation mode comprises a grid-connected mode and an offline mode; and under the condition that the working mode is determined to be a target mode, a direct current control loop of the energy storage converter is disabled, and a grid-connected current reference value of an alternating current power grid is used as an alternative instruction value of an inner loop controller of the energy storage converter to control the energy storage converter. According to the method, the energy storage converter can stably work according to a control instruction, and on the basis of smooth grid-connected and off-grid switching, the alternating current side grid-connected power is accurately controlled.

Description

Technical Field

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

[0002] As a key device connecting the energy storage system and the power grid, the performance of the energy storage inverter is of great significance to the stability and reliability of the power system. The on-grid and off-grid energy storage inverter not only needs to achieve efficient energy conversion, but also needs to have the ability to smoothly switch between the on-grid mode and the off-grid mode to meet the needs of different operating environments.

[0003] The grid-connected power control accuracy and the working state of the energy storage battery during grid-connected operation, the grid-connected power accuracy helps to achieve efficient and stable operation of the power system, and the battery status monitoring and control operation and maintenance help to extend the service life and operational reliability of the energy storage converter. However, the existing control methods rarely take the two design indicators into consideration, and basically do not pay too much attention to the overcharge protection of the energy storage battery.

[0004] Therefore, it is urgent to propose a grid-connected and off-grid switching control method for energy storage inverters that comprehensively considers grid-connected power control and integrated battery protection. The energy storage inverter can accurately control the AC grid-connected power on the basis of stable operation and smooth grid-connected and off-grid switching under different power grid instruction requirements. Summary of the invention

[0005] The present application aims to solve at least one of the technical problems existing in the prior art. To this end, the present application proposes a converter control method, device, equipment and medium, and the energy storage converter can accurately control the AC grid-connected power based on the stable operation and smooth grid-off switching according to the control instructions.

[0006] In a first aspect, the present application provides a converter control method, which is applied to a three-phase four-wire three-level energy storage converter, wherein the energy storage converter comprises a DC part, an inverter and an AC part connected in sequence, wherein the AC part is used to connect to an AC power grid, and the AC part is provided with an on-grid and off-grid switching device on a side close to the AC power grid;

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

[0008] The method comprises:

[0009] In the case of receiving a control instruction, in response to the control instruction, determining the working mode of the energy storage converter, wherein the working 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 requirement, and the operating mode includes a grid-connected mode and an offline mode;

[0010] When it is determined that the working mode is 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 an alternative instruction value of the inner loop controller of the energy storage converter to control the energy storage converter.

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

[0012] When the battery state is in the second state, the target mode is a 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 an embodiment of the present application, when the battery state is the first state and the operation mode is the grid-connected mode, after determining the working mode of the energy storage converter, the method further includes:

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

[0016] Based on the inner loop candidate instruction value i pcs_CC , through the grid-side filter inductor L in the inner loop f2 The current i L2 Control the grid-connected current;

[0017] When the working mode is determined to be the suspended discharge mode, the DC voltage reference lower limit value V bat_ref_L With DC voltage feedback value v bus_fb After comparison, it is sent to the DC voltage outer loop controller G vinv (s), after the limiting process, the corresponding alternative instruction value i is obtained inv_CV ;

[0018] Based on the corresponding alternative instruction value i inv_CV , take over the discharge state of the energy storage battery and suspend discharge.

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

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

[0021] Based on the corresponding candidate instruction value i inv_CV Take over the charging status of the energy storage battery and pass the grid-side filter inductor L in the inner loop f2 The current i L2 Realize the regulation and control of grid-connected current;

[0022] When the working mode is determined to be the constant current discharge mode, the DC current reference value i bat_ref and DC current feedback value i bat_fb After comparison, it is sent to the DC current outer loop controller G ipcs (s), calculate the inner loop alternative instruction value i pcs_CC , the inner loop passes through the grid-side filter inductor L f2 The current i L2 Realize the regulation and control of grid-connected current.

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

[0024] When the working mode is determined to be the load voltage control mode, the AC load voltage reference value V Load_ref With feedback value v Load_fb After comparison, it is sent to the load voltage controller G vLoad (s), the voltage through the filter capacitor v C Active damping is realized to obtain the reference modulation signal v in off-grid mode operation m_inv2 , to control the load voltage of the AC load.

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

[0026] When it is determined that the working mode is 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 an embodiment of the present application, in the case of receiving a control instruction, before determining the working mode of the energy storage converter in response to the control instruction, the method further includes:

[0028] When it is determined that the energy storage converter is switched from the grid-connected mode to the off-grid mode, the current of the grid-side filter inductor is controlled to be 0 through 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, and the grid-connected isolation switch in the grid-connected and off-grid switching device is cut off, and the energy storage converter is in the island mode;

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

[0030] In a second aspect, the present application provides a converter control device, which is applied to a three-phase four-wire three-level energy storage converter, wherein the energy storage converter comprises a DC part, an inverter and an AC part connected in sequence, wherein the AC part is used to connect to an AC power grid, and the AC part is provided with an on-grid and off-grid switching device on a side close to the AC power grid;

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

[0032] The device comprises:

[0033] A first processing module is used for determining, in response to a control instruction, a working mode of the energy storage converter when a control instruction is received, wherein the working mode is determined based on an operation mode of the energy storage converter, a battery state of an energy storage battery, and a grid-connected power accuracy requirement, and the operation mode includes a grid-connected mode and an offline mode;

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

[0035] In a third aspect, the present application provides an electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, the converter control method as described in the first aspect above is implemented.

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

[0037] In a fifth aspect, the present application provides a chip, comprising a processor and a communication interface, wherein the communication interface is coupled to the processor, and the processor is used to run a program or instruction to implement the converter control method as described in the first aspect.

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

[0039] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application.

[0040] The present application provides a converter control method, device, equipment and medium, which have the following beneficial effects compared with the prior art:

[0041] (1) The working mode generated by the operating mode, battery status and grid-connected power accuracy requirements can flexibly adapt to different operating conditions, disable the DC current control loop, and actively adjust the DC current to convert it into AC grid-connected power. Avoid the interference of battery status on the grid-connected power accuracy, ensure that the energy storage inverter can work stably according to the control instructions to meet actual needs, and accurately control the AC grid-connected power on the basis of smooth grid-connected and off-grid switching. It is not only suitable for grid-connected and off-grid energy storage inverters, but the grid-connected mode controller and the off-grid mode controller can also act on the grid-connected and off-grid energy storage inverters respectively.

[0042] (2) On the basis of realizing smooth switching of different working modes of grid-connected and islanded energy storage inverters, the precise control of grid-connected power and the charging and discharging protection of energy storage batteries are comprehensively considered, which has high operating reliability and effectively extends the service life of energy storage batteries. At the same time, the control strategy of this application is simple, with low complexity, and is easy to implement in digital control. When a battery management system fails, this method can provide certain support for the reliable operation of the DC side energy storage battery. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0044] Figure 1 This is the structural intention of the grid-connected and off-grid energy storage converter provided in the embodiment of the present application;

[0045] Figure 2It is a topological structure diagram of a three-phase four-wire T-type three-level energy storage converter provided in an embodiment of the present application;

[0046] Figure 3 is a flow chart of a converter control method provided in an embodiment of the present application;

[0047] Figure 4 It is a schematic diagram of the state of the grid-connected and off-grid energy storage converter provided in the embodiment of the present application in the grid-connected mode;

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

[0049] Figure 6 It is a DC side waveform diagram during the dynamic switching process from the grid-connected current control discharge mode to the grid-connected current control charging mode when the grid-connected power control accuracy is provided in the embodiment of the present application;

[0050] Figure 7 It is an AC side waveform diagram during the dynamic switching process from the grid-connected current control discharge mode to the grid-connected current control charging mode when the grid-connected power control accuracy is provided in the embodiment of the present application;

[0051] Figure 8 It is a DC side waveform diagram during the dynamic switching process from the constant current discharge mode to the constant current charging mode when controlling the current size of the DC side energy storage battery provided in the embodiment of the present application;

[0052] Fig. 9 It is an AC side waveform diagram during the dynamic switching process from a constant current discharge mode to a constant current charging mode when controlling the current size of a DC side energy storage battery provided in an embodiment of the present application;

[0053] Fig.10 It is a steady-state working waveform of the DC side of the energy storage converter connected to the grid when the SOC of the energy storage battery provided in the embodiment of the present application is high;

[0054] Fig.11 It is the AC side steady-state working waveform of the energy storage converter connected to the grid when the energy storage battery SOC provided in the embodiment of the present application is high;

[0055] Fig.12 It is a steady-state working waveform of the DC side of the energy storage converter connected to the grid when the SOC of the energy storage battery provided in the embodiment of the present application is low;

[0056] Fig.13 It is the AC side steady-state working waveform of the energy storage converter connected to the grid when the energy storage battery SOC provided in the embodiment of the present application is low;

[0057] Fig.14 It is a schematic diagram of the structure of an electronic device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0058] The following will be combined with the drawings in the embodiments of the present application to clearly describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments in the present application belong to the scope of protection of this application.

[0059] The terms "first", "second", etc. in the specification and claims of the present application are used to distinguish similar objects, and are not used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable under appropriate circumstances, so that the embodiments of the present application can be implemented in an order other than those illustrated or described here, and the objects distinguished by "first", "second", etc. are generally of one type, and the number of objects is not limited. For example, the first object can be one or more. In addition, "and / or" in the specification and claims represents at least one of the connected objects, and the character " / " generally indicates that the objects associated with each other are in an "or" relationship.

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

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

[0062] The terminal includes, but is not limited to, a portable communication device such as a mobile phone or tablet computer with a touch-sensitive surface (e.g., a touch screen display and / or a touch pad). It should also be understood that in some embodiments, the terminal may not be a portable communication device, but a desktop computer with a touch-sensitive surface (e.g., a touch screen display and / or a touch pad).

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

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

[0065] like Figure 1As shown, the method is applied to a three-phase four-wire three-level energy storage converter, the energy storage converter comprises a DC part, an inverter and an AC part connected in sequence, the AC part is used to connect to an AC power grid, and the AC part is provided with an on-grid and off-grid switching device on a side close to the AC power grid;

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

[0067] The DC side filter capacitors include C bus1 , C bus2 , inverter side filter inductor L f1 Including L f1a , L f1b , L f1c , neutral line 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 load includes Load_fa, Load_fb, and Load_fc.

[0068] exist Figure 1 In the figure, the energy storage converter is a grid-connected and off-grid type, including a main circuit and a control circuit. The gray box below is a control strategy structure diagram proposed in this application, such as 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 as follows in Table 1:

[0070] Table 1 Main parameters

[0071] AC side load output voltage <![CDATA[V Load_ref ]]> 230V(RMS) Switching frequency of 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 inductance <![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 instruction, determining the working mode of the energy storage converter in response to the control instruction, wherein the working 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 requirement, and the operating mode includes a grid-connected mode and an offline mode;

[0074] Step 320: When it is determined that the working mode is 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 an alternative instruction value of the inner loop controller of the energy storage converter to control the energy storage converter.

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

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

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

[0078] When it is determined that the energy storage converter is switched from the grid-connected mode to the off-grid mode, the current of the grid-side filter inductor is controlled to be 0 through 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, and the grid-connected isolation switch in the grid-connected and off-grid switching device is cut off, and the energy storage converter is in the island mode;

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

[0080] When the energy storage converter is required to actively switch from the grid-connected mode to the offline mode, the grid-side filter inductor L is first switched to the offline mode through the off-grid mode controller. f2 The current i L2 Controlled to 0, and then control the AC side filter capacitor voltage v c Tracking grid voltage v g , and finally control the on-grid and off-grid switching device to cut off the grid disconnector and switch to island 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 disconnector; Finally, control the grid-connected and off-grid switching device to switch to the grid-side filter inductor L f2 Current control mode.

[0082] After the on-grid and off-grid switching device is switched, the controller receives the control instruction 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 , grid-side filter inductor current i L2_fb , AC load voltage feedback value v Load_fb , and send the sampled values ​​to the controller designed by this method to realize various modes and functions of the grid-connected and off-grid energy storage converter.

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

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

[0086] The AC side switch control strategy switches the energy storage converter to a specific on-grid or off-grid mode. The on-grid mode sends the command value to the corresponding inner loop controller, and the off-grid mode directly outputs the single-loop calculation value to obtain a modulation signal.

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

[0088] When the battery state is in the second state, the target mode is a 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 inverter control method provided in the embodiment of the present application, the working mode is generated by the operating mode, battery status and grid-connected power accuracy requirements to flexibly adapt to different operating conditions, disable the DC current control loop, and actively adjust the DC current to convert it into AC grid-connected power. The interference of the battery status on the grid-connected power accuracy is avoided, and the energy storage inverter can be ensured to work stably to meet actual needs according to the control instructions. On the basis of smooth on-grid and off-grid switching, the AC grid-connected power is accurately controlled. It is not only suitable for on-grid and off-grid energy storage inverters, but the grid-connected mode controller and the off-grid mode controller can also act on the grid-connected and off-grid energy storage inverters respectively.

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

[0092] When the working mode is determined to be the constant current charging mode, the DC current reference value Ibat_ref and DC current feedback value i bat_fb After comparison, the DC current is sent to the DC current outer loop controller G of the energy storage converter. ipcs (s), calculate the inner loop alternative instruction value i pcs_CV ;

[0093] Based on the inner loop candidate instruction value i pcs_CV , through the grid-side filter inductor L in the inner loop f2 The current i L2 Control the grid-connected current;

[0094] When the working mode is determined to be the suspended discharge mode, the DC voltage reference lower limit value V bat_ref_L With DC voltage feedback value v bus_fb After comparison, it is sent to the DC voltage outer loop controller G vinv (s), after the limiting process, the corresponding alternative instruction value i is obtained inv_CV ;

[0095] Based on the corresponding alternative instruction value i inv_CV , take over the discharge state of the energy storage battery and suspend discharge.

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

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

[0098] Based on the corresponding candidate instruction value i inv_CV Take over the charging status of the energy storage battery and pass the grid-side filter inductor L in the inner loop f2 The current i L2 Realize the regulation and control of grid-connected current;

[0099] When the working mode is determined to be the constant current discharge mode, the DC current reference value i bat_ref and DC current feedback value i bat_fb After comparison, it is sent to the DC current outer loop controller G ipcs (s), calculate the inner loop alternative instruction value i pcs_CC The inner loop passes through the grid-side filter inductor L f2 The current i L2 Realize the 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 working mode of the energy storage converter, the method further includes:

[0101] When the working mode is determined to be the load voltage control mode, the AC load voltage reference value V Load_ref With feedback value v Load_fb After comparison, it is sent to the load voltage controller G vLoad (s), the voltage through the filter capacitor v C Active damping is realized to obtain the reference modulation signal v in off-grid mode operation m_inv2 , to control the load voltage of the AC load.

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

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

[0104] When it is determined that the working mode is 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 inverter. The working mode of the energy storage inverter can be smoothly switched and controlled according to different requirements such as the AC side grid-connected power accuracy and the DC side energy storage battery current size, so that the energy storage inverter can stably work in any working mode.

[0106] In this embodiment, the energy storage inverter can operate in any of the grid-connected modes including 6 working modes and the offline modes including 2 island working modes according to the current state and demand, and can improve the grid-connected power control accuracy on the basis of realizing smooth switching between grid and off-grid, and can also strengthen the health monitoring and protection of the energy storage battery.

[0107] The protection function is not achieved through internal battery structure management and design, but battery health monitoring is indirectly completed 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 power of the energy storage battery is less than 20%.

[0109] The second state indicates that the SOC state of the energy storage battery is higher, for example, the power of the energy storage battery is greater than 80%.

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

[0111] Constant current charging mode. When the SOC state of the energy storage battery is low, the DC current reference value i bat_ref and DC current feedback value i bat_fb After comparison, it is sent to the DC current outer loop controller G ipcs (s), calculate the inner loop alternative instruction value i pcs_CC The inner loop passes through the grid-side filter inductor L f2 The current i L2 Realize the regulation and control of grid-connected current.

[0112] Constant voltage charging mode. When the SOC state of the energy storage battery is high, the DC voltage reference upper limit V bat_ref_H With DC voltage feedback value v bus_fb After comparison, it is sent to the DC voltage outer loop controller G vinv (s), after the limit processing, the corresponding alternative instruction value i is obtained inv_CV , to take over the battery charging status to protect the battery and trickle charge. The inner loop passes through the grid-side filter inductor L f2 The current i L2 Realize the regulation and control of grid-connected current.

[0113] Grid-connected current control charging mode. When there are strict requirements on the grid-connected power accuracy and the SOC state of the energy storage battery is low, switch to this mode, the DC current control loop is disabled, and the grid-connected current reference value i is directly used. g_ref As an alternative command value for the inner loop controller.

[0114] Constant current discharge mode. When the SOC state of the energy storage battery is high, the DC current reference value i bat_ref and DC current feedback value i bat_fb After comparison, it is sent to the DC current outer loop controller G ipcs (s), calculate the inner loop alternative instruction value i pcs_CC The inner loop passes through the grid-side filter inductor L f2 The current i L2 Realize the regulation and control of grid-connected current.

[0115] Suspend discharge mode. When the SOC state of the energy storage battery is low, it cannot continue to discharge. The DC voltage reference lower limit V bat_ref_L With DC voltage feedback value v bus_fb After comparison, it is sent to the DC voltage outer loop controller G vinv (s), after the limit processing, the corresponding alternative instruction value i is obtained inv_CV , thereby taking over the battery discharge status to protect the battery and suspend discharge.

[0116] Grid-connected current control discharge mode. When there are strict requirements on the grid-connected power accuracy and the SOC state of the energy storage battery is high, switch to this mode, the DC current control loop is disabled, and the grid-connected current reference value i is directly g_ref As an alternative command value for the inner loop controller.

[0117] According to different requirements on grid-connected power accuracy or energy storage battery charging current, the switch S1 can be controlled to smoothly switch between the grid-connected current control charging mode and the constant current charging mode.

[0118] According to different requirements on grid-connected power accuracy or energy storage battery discharge current, the switch S2 can be controlled to smoothly switch between the grid-connected current control discharge mode and the constant current discharge mode.

[0119] When the energy storage converter is connected to the grid for charging, if the grid power accuracy is required, the grid current reference value i g_ref and the alternative command value i calculated by the constant voltage charging mode control outer loop inv_CV The larger value is taken as the inner loop current i L2 If the emphasis is on battery charging current, the alternative command value i is calculated by the constant current charging mode and constant voltage charging mode control outer loop. pcs_CC and i inv_CV The larger value of the inner loop current i L2 Control reference value.

[0120] When the energy storage converter is connected to the grid and discharges, if the grid power accuracy is required, the grid current reference value i g_ref and the alternative command value i calculated by the constant voltage discharge mode control outer loop inv_CV The smaller value is taken as the inner loop current i L2 If the emphasis is on battery charging current, the alternative command value i is calculated by the constant current discharge mode and constant voltage discharge mode control outer loop. pcs_CC and i inv_CV The smaller value is taken as the inner loop current i L2 Control reference value.

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

[0122] The switchable working modes of offline mode include:

[0123] Load voltage control mode. When the SOC state of the energy storage battery is high, the AC load voltage reference value V Load_ref With feedback value v Load_fb After comparison, it is sent to the load voltage controller G vLoad (s), the voltage through the filter capacitor v C Active damping is achieved to obtain the reference modulation signal v in off-grid mode operation m_inv2 , achieving precise control of the load voltage.

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

[0125] like Figure 6 and Figure 7 As shown, when the grid-connected power control accuracy is required, the energy storage converter dynamically switches from the grid-connected current control discharge mode to the grid-connected current control charging mode.

[0126] Figure 6 is the SOC of the energy storage battery under dynamic process, and the DC side current i bat , DC bus voltage v bus Working waveform.

[0127] Figure 7 is the corresponding grid-side filter inductor L f2 Current i L2x and the output voltage v ox waveform.

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

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

[0130] Figure 8 is the SOC of the energy storage battery under dynamic process, and the DC side current i bat , DC bus voltage v bus Working waveform.

[0131] Fig. 9 is the corresponding grid-side filter inductor L f2 Current i L2x and the output voltage vox waveform.

[0132] It can be found that the charge and discharge switching process is continuous and smooth, the L2 inductor current waveform quality is good, and the DC side current control is stable.

[0133] like Fig.10 and Fig.11 As shown, in order to verify the extended protection function, the grid-connected steady-state working waveform of the energy storage converter is shown when the SOC of the DC side energy storage battery is high.

[0134] Fig.10 After reaching steady state, the energy storage battery SOC and DC side current i bat , DC bus voltage v bus Working waveform.

[0135] Fig.11 is the corresponding grid-side filter inductor L f2 Current i L2x and the output voltage v ox waveform.

[0136] The energy storage battery SOC (%) is set to a higher state, and the controller grid-connected current reference value is -110A, that is, the AC side has a tendency to charge the energy storage converter. The constant voltage control loop is judged to be effective by measuring the DC side energy storage battery charging current and battery voltage. If the DC side charging current value is very small, not the set reference value, and the energy storage battery voltage is stable at the reference upper limit value, the effectiveness of this control method can be proved. When the battery SOC is high, the DC side voltage control loop plays an extended protection role for the battery, and trickle charging.

[0137] like Fig.12 and Fig.13 As shown, in order to verify the over-discharge protection function, the grid-connected steady-state working waveform of the energy storage converter is shown when the SOC of the DC side energy storage battery is low.

[0138] Fig.12 After reaching steady state, the energy storage battery SOC and DC side current i bat , DC bus voltage v bus Working waveform.

[0139] Fig.13 is the corresponding grid-side filter inductor L f2 Current i L2x and the output voltage v ox waveform.

[0140] The energy storage battery SOC (%) is set to a low state, and the controller grid-connected current reference value is 110A, that is, the energy storage converter has a tendency to discharge to the grid. The constant voltage control loop is judged to be effective by measuring the DC side energy storage battery discharge current and battery voltage. If the DC side discharge current value is very small, not the set reference value, and the energy storage battery voltage is stable at the reference lower limit value, the effectiveness of this control method can be proved. When the battery SOC is low, the DC side voltage control loop protects the battery from over-discharge and suspends discharge.

[0141] In this embodiment, on the basis of realizing smooth switching of different working modes of grid-connected and islanded energy storage converters, precise control of grid-connected power and charging and discharging protection of energy storage batteries are comprehensively considered, which has high operating reliability and effectively extends the service life of energy storage batteries. At the same time, the control strategy of the present application is simple, with low complexity, and is easy to implement in digital control. When a battery management system (BMS) fails, the method can provide certain support for the reliable operation of DC-side energy storage batteries.

[0142] The converter control method provided in the embodiment of the present application may be executed by a converter control device. In the embodiment of the present application, the converter control device provided in the embodiment of the present application is described by taking the converter control device executing the converter control method as an example.

[0143] The embodiment of the present application also provides a converter control device, which is applied to a three-phase four-wire three-level energy storage converter, wherein the energy storage converter comprises a DC part, an inverter and an AC part connected in sequence, wherein the AC part is used to connect to an AC power grid, and the AC part is provided with an on-grid and off-grid switching device on a side close to the AC power grid;

[0144] The DC part includes an energy storage battery and a DC side filter capacitor connected in sequence, and the AC part 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 comprises:

[0146] A first processing module is used for determining, in response to a control instruction, a working mode of the energy storage converter when a control instruction is received, wherein the working mode is determined based on an operation mode of the energy storage converter, a battery state of an energy storage battery, and a grid-connected power accuracy requirement, and the operation mode includes a grid-connected mode and an offline mode;

[0147] The second processing module is used to disable the DC current control loop of the energy storage converter when it is determined that the working mode is the target mode, and use the grid-connected current reference value of the AC power grid as an alternative instruction 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 embodiment of the present application, the working mode is generated by the operating mode, battery status and grid-connected power accuracy requirements to flexibly adapt to different operating conditions, disable the DC current control loop, and actively adjust the DC current to convert it into AC grid-connected power. This avoids the interference of the battery status on the grid-connected power accuracy, ensures that the energy storage converter can work stably to meet actual needs according to the control instructions, and accurately controls the AC grid-connected power on the basis of smooth on-grid and off-grid switching. It is not only suitable for on-grid and off-grid energy storage converters, but the grid-connected mode controller and the off-grid mode controller can also act on the grid-connected and off-grid energy storage converters respectively.

[0149] The converter control device in the embodiment of the present application can be an electronic device, or a component in the electronic device, such as an integrated circuit or a chip. The electronic device can be a terminal, or other devices other than the terminal. Exemplarily, the electronic device can be a mobile phone, a tablet computer, a laptop computer, a PDA, a vehicle-mounted electronic device, a mobile Internet device (Mobile Internet Device, MID), an augmented reality (Augmented Reality, AR) / virtual reality (Virtual Reality, VR) device, a robot, a wearable device, a super mobile personal computer (Ultra-Mobile Personal Computer, UMPC), a netbook or a personal digital assistant (Personal Digital Assistant, PDA), etc., and can also be a server, a network attached storage (Network Attached Storage, NAS), a personal computer (Personal Computer, PC), a television (Television, TV), a teller machine or a self-service machine, etc., which is not specifically limited in the embodiment of the present application.

[0150] The converter control device in the embodiment of the present application may be a device having an operating system. The operating system may be an Android operating system, an iOS operating system, or other possible operating systems, which are not specifically limited in the embodiment of the present application.

[0151] The converter control device provided in the embodiment of the present application can implement various processes implemented by the converter control method embodiment in the above-mentioned embodiment, and will not be described again here to avoid repetition.

[0152] In some embodiments, Fig.14As shown, an embodiment of the present application 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, each process of the above-mentioned converter control method embodiment is implemented, and the same technical effect can be achieved. To avoid repetition, it will not be repeated here.

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

[0154] An embodiment of the present application also provides a non-transitory computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the various processes of the above-mentioned converter control method embodiment are implemented, and the same technical effect can be achieved. To avoid repetition, it will not be repeated here.

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

[0156] An embodiment of the present application also provides a computer program product, including a computer program, which implements the above-mentioned converter control method when executed by a processor.

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

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

[0159] It should be understood that the chip mentioned in the embodiments of the present application can also be called a system-level chip, a system chip, a chip system or a system-on-chip chip, etc.

[0160] It should be noted that, in this article, the terms "comprise", "include" or any other variant thereof are intended to cover non-exclusive inclusion, so that the process, method, article or device including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise one..." do not exclude the presence of other identical elements in the process, method, article or device including the element. In addition, it should be pointed out that the scope of the methods and devices in the embodiments of the present application is not limited to performing functions in the order shown or discussed, and may also include performing functions in a substantially simultaneous manner or in reverse order according to the functions involved, for example, the described method may be performed in an order different from that described, and various steps may also be added, omitted, or combined. In addition, the features described with reference to certain examples may be combined in other examples.

[0161] Through the description of the above implementation methods, those skilled in the art can clearly understand that the above-mentioned embodiment methods can be implemented by means of software plus a necessary general hardware platform, and of course by hardware, but in many cases the former is a better implementation method. Based on such an understanding, the technical solution of the present application, or the part that contributes to the prior art, can be embodied in the form of a computer software product, which is stored in a storage medium (such as ROM / RAM, a disk, or an optical disk), and includes a number of instructions for a terminal (which can be a mobile phone, a computer, a server, or a network device, etc.) to execute the converter control method of each embodiment of the present application.

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

[0163] In the description of the present application, “plurality” means two or more.

[0164] The embodiments of the present application are described above in conjunction with the accompanying drawings, but the present application is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the guidance of the present application, ordinary technicians in this field can also make many forms without departing from the purpose of the present application and the scope of protection of the claims, all of which are within the protection of the present application.

[0165] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

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

Claims

1. A converter control method, characterized in that: An energy storage converter applied to a three-phase four-wire three-level system, the energy storage converter comprising a DC part, an inverter and an AC part connected in sequence, the AC part being used to connect to an AC power grid, and the AC part being provided with an on-grid and off-grid switching device on a side close to the AC power grid; The DC part includes an energy storage battery and a DC side filter capacitor connected in sequence, and the AC part includes an inverter side filter inductor, an AC side filter capacitor, a grid side filter inductor and an AC load; The method comprises: In the case of receiving a control instruction, in response to the control instruction, determining the working mode of the energy storage converter, wherein the working 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 requirement, and the operating mode includes a grid-connected mode and an offline mode; When it is determined that the working mode is 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 an alternative instruction value of the inner loop controller of the energy storage converter to control the energy storage converter.

2. The converter control method according to claim 1, characterized in that: When the battery state is in the first state, the target mode is a grid-connected current control charging mode; When the battery state is in the second state, the target mode is a 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.

3. The converter control method according to claim 2, characterized in that: When the battery state is the first state and the operation mode is the grid-connected mode, after determining the working mode of the energy storage converter, the method further includes: When the working mode is determined to be the constant current charging mode, the DC current reference value i bat_ref and DC current feedback value i bat_fb After comparison, the DC current is sent to the DC current outer loop controller G of the energy storage converter. ipcs (s), calculate the inner loop alternative instruction value i pcs_CC ; Based on the inner loop candidate instruction value i pcs_CC , through the grid-side filter inductor L in the inner loop f2 The current i L2 Control the grid-connected current; When the working mode is determined to be the suspended discharge mode, the DC voltage reference lower limit value V bat_ref_L With DC voltage feedback value v bus_fb After comparison, it is sent to the DC voltage outer loop controller G vinv (s), after the limiting process, the corresponding alternative instruction value i is obtained inv_CV ; Based on the corresponding alternative instruction value i inv_CV , take over the discharge state of the energy storage battery and suspend discharge.

4. The converter control method according to claim 2, characterized in that: When the battery state is the second state, after determining the working mode of the energy storage converter, the method further includes: When the working mode is determined to be the constant voltage charging mode, the DC voltage reference upper limit value V bat_ref_H With DC voltage feedback value v bus_fb After comparison, the DC voltage is sent to the DC voltage outer loop controller G of the energy storage converter. vinv (s), after the limiting process, the corresponding alternative instruction value i is obtained inv_CV ; Based on the corresponding candidate instruction value i inv_CV Take over the charging status of the energy storage battery and pass the grid-side filter inductor L in the inner loop f2 The current i L2 Realize the regulation and control of grid-connected current; When the working mode is determined to be the constant current discharge mode, the DC current reference value i bat_ref and DC current feedback value i bat_fb After comparison, it is sent to the DC current outer loop controller G ipcs (s), calculate the inner loop alternative instruction value i pcs_CC , the inner loop passes through the grid-side filter inductor L f2 The current i L2 Realize the regulation and control of grid-connected current.

5. The converter control method according to claim 2, characterized in that: When the operating mode is the offline mode and the battery state is the second state, after determining the working mode of the energy storage converter, the method further includes: When the working mode is determined to be the load voltage control mode, the AC load voltage reference value V Load_ref With feedback value v Load_fb After comparison, it is sent to the load voltage controller G vLoad (s), the voltage through the filter capacitor v C Active damping is achieved to obtain the reference modulation signal v in off-grid mode operation m_inv2 , to control the load voltage of the AC load.

6. The converter control method according to claim 2, characterized in that: When the operating mode is the offline mode and the battery state is the first state, after determining the working mode of the energy storage converter, the method further includes: When it is determined that the working mode is the load voltage control mode, the energy storage battery is controlled to stop discharging, and the energy storage converter is controlled to stop working.

7. The converter control method according to claim 1, characterized in that: In the case of receiving a control instruction, before determining the working mode of the energy storage converter in response to the control instruction, the method further includes: When it is determined that the energy storage converter is switched from the grid-connected mode to the off-grid mode, the current of the grid-side filter inductor is controlled to be 0 through 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, and the grid-connected isolation switch in the grid-connected and off-grid switching device is cut off, and the energy storage converter is in the island mode; When it is determined that the energy storage inverter switches from the off-grid mode to the grid-connected mode, the AC side filter capacitor voltage is controlled to track the grid voltage of the AC power grid through the grid-connected mode controller, and the grid-connected isolation switch is closed. The energy storage inverter is in the grid-side filter inductor current control mode.

8. A converter control device, characterized in that: An energy storage converter applied to a three-phase four-wire three-level system, the energy storage converter comprising a DC part, an inverter and an AC part connected in sequence, the AC part being used to connect to an AC power grid, and the AC part being provided with an on-grid and off-grid switching device on a side close to the AC power grid; The DC part includes an energy storage battery and a DC side filter capacitor connected in sequence, and the AC part includes an inverter side filter inductor, an AC side filter capacitor, a grid side filter inductor and an AC load; The device comprises: A first processing module is used for determining, in response to a control instruction, a working mode of the energy storage converter when a control instruction is received, wherein the working mode is determined based on an operation mode of the energy storage converter, a battery state of an energy storage battery, and a grid-connected power accuracy requirement, and the operation mode includes a grid-connected mode and an offline mode; The second processing module is used to disable the DC current control loop of the energy storage converter when it is determined that the working mode is the target mode, and use the grid-connected current reference value of the AC power grid as an alternative instruction value of the inner loop controller of the energy storage converter to control the energy storage converter.

9. 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, the converter control method according to any one of claims 1 to 7 is implemented.

10. A non-transitory computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the converter control method according to any one of claims 1 to 7 is implemented.

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