A multi-mode energy storage system with a multi-path battery interface

Abstract

The application discloses a multi-mode energy storage system of a multi-path battery interface, comprising an inverter architecture and a multi-path bidirectional DC / DC unit; the multi-path bidirectional DC / DC unit is connected in parallel to a direct current side bus of the inverter architecture through a first end, and a second end of the bidirectional DC / DC unit is used for accessing an energy storage module; a single energy storage module is adapted to be connected with at least one bidirectional DC / DC unit, thereby forming multiple connection modes; and a control loop is adapted to output a duty cycle of a corresponding bidirectional DC / DC unit according to an on-grid or off-grid state of the inverter architecture and a connection mode of the energy storage module. The application has the beneficial effects that: the input port of the application has multiple energy storage module connection modes, and can adapt to different types of energy storage modules, and has stronger flexibility. Moreover, the system can automatically identify the connection mode of the energy storage module according to the voltage value and the current value of the input port. The control loop can adapt to different energy storage module connection modes, and can effectively improve the applicability of the system.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of new energy power generation, in particular to a multi-mode energy storage system with multiple battery interfaces. BACKGROUND

[0002] The energy storage system mainly includes a power generation system and an energy storage module; the energy storage system can directly supply power to a load through the power generation system, or supply power to the load through the energy storage module, and can also charge the energy storage module when the power generation system has excess energy.

[0003] The energy storage module mainly uses a storage battery; currently, the energy storage system is often designed with only a single battery interface, so that the energy storage system can only be adapted to a specific type of battery. That is, the prior art lacks a unified and efficient adaptation mechanism for different types of battery interfaces, which not only requires a large amount of manpower, material resources and time cost in the system design, development and operation process, but also increases the risk of system failure and the complexity of maintenance. SUMMARY

[0004] One of the purposes of the present application is to provide a multi-mode energy storage system with multiple battery interfaces that can solve at least one of the defects in the background art.

[0005] To achieve the above at least one purpose, the technical solution adopted by the present application is: a multi-mode energy storage system with multiple battery interfaces, comprising an inverter architecture, multiple bidirectional DC / DC units and a control loop; the multiple bidirectional DC / DC units are connected in parallel to the DC side bus of the inverter architecture through a first end, and the second end of the bidirectional DC / DC unit is used to access an energy storage module; a single energy storage module is adapted to be connected to at least one bidirectional DC / DC unit, thereby forming multiple connection modes; the control loop is adapted to output the duty cycle of the bidirectional DC / DC unit according to the on-grid and off-grid state of the inverter architecture and the connection mode of the energy storage module.

[0006] Preferably, when only one bidirectional DC / DC unit is connected to the energy storage module, the system is in a single battery single interface mode; when multiple bidirectional DC / DC units are connected to the same energy storage module, the system is in a single battery multiple interface mode; when multiple or all bidirectional DC / DC units are independently connected to the energy storage module, the system is in a multiple battery multiple interface mode.

[0007] Preferably, when the system is in the single-battery multi-interface mode, the bidirectional DC / DC units support a backup operation mode and a parallel operation mode; in the backup operation mode, the energy storage module selects the bidirectional DC / DC unit with the optimal state as the main circuit unit for operation, and the rest of the bidirectional DC / DC units are redundant to the bidirectional DC / DC unit with the optimal state; in the parallel operation mode, each bidirectional DC / DC unit operates simultaneously, thereby reducing the working load of a single bidirectional DC / DC unit.

[0008] Preferably, for the selection of the backup operation mode and the parallel operation mode, adjustment is made according to the working data collection of the energy storage module, specifically including the following processes: collecting the SOC value and working current of the energy storage module; if the SOC value of the energy storage module is lower than a set threshold, the DC / DC unit selects the parallel operation mode for charging the energy storage module; if the working current of the energy storage module exceeds the rated current, the DC / DC unit selects the parallel operation mode for shunting; if a single DC / DC unit meets the working power demand of the energy storage module, the DC / DC unit selects the backup operation mode for operation.

[0009] Preferably, the system performs the single-battery single-interface mode, single-battery multi-interface mode and multi-battery multi-interface mode judgment process as follows: control each bidirectional DC / DC unit to work in time division, while blocking the rest of the bidirectional DC / DC units; when each bidirectional DC / DC unit works, detect the voltage value and current value of the input port of each bidirectional DC / DC unit; if the current value corresponding to each input port is zero, it is judged that the system has no access of the energy storage module; if only one input port corresponding to the current value is non-zero, it is judged that the system is in the single-battery single-interface mode; if there are multiple input ports corresponding to the current value, and the voltage values of the input ports with non-zero current values remain consistent, it is judged that the system is in the single-battery multi-interface mode; if there are multiple input ports corresponding to the current value, and the voltage values of the input ports with non-zero current values do not remain consistent, it is judged that the system is in the multi-battery multi-interface mode.

[0010] Preferably, when the system is in the multi-battery multi-interface mode, if the voltage values of the multiple input ports are at the same level, the type of the corresponding accessed energy storage module needs to be determined, specifically including the following process: simultaneously controlling the multiple bidirectional DC / DC units to work at the same duty cycle, or controlling the corresponding energy storage modules of the multiple input ports to work under the same constant current condition; detecting the port voltage and current of the multiple bidirectional DC / DC units, if the voltage and current change rates of the multiple input ports are consistent, it is determined that the types of the energy storage modules accessed by the multiple input ports are the same; otherwise, it is determined that the types of the energy storage modules accessed by the multiple input ports are different.

[0011] Preferably, the control loop includes a voltage outer loop, a maximum value module, a current sharing module, an amplitude limiting module, and multiple duty cycle generation modules; the voltage outer loop compares the bus voltage with the bus voltage instruction value, calculates a first current given value through a PI controller, and takes the first current given value as one input of the maximum value module after assigning a weight coefficient to the first current given value; the other input of the maximum value module is a second current given value issued by the ARM, and the maximum value module takes the maximum value of the two inputs as the current given value of the battery side and outputs it to the current sharing module; the current sharing module is adapted to distribute the current given value according to the connection mode of the system and send it to the amplitude limiting module; the amplitude limiting module is adapted to limit the distributed value and send it to multiple duty cycle generation modules respectively; each duty cycle generation module is adapted to compare the input distributed value with the current sampling value of the corresponding bidirectional DC / DC unit, generate the duty cycle of the corresponding bidirectional DC / DC unit through a PI controller.

[0012] Preferably, when the system is in the grid-connected mode, the weight coefficient assigned to the voltage outer loop is -∞; at the same time, the ARM calculates the second current given value according to the working power of the energy storage module and the bus voltage; when the system is in the off-grid mode, the weight coefficient assigned to the voltage outer loop is 0; at the same time, the ARM directly sets the second current given value to -∞.

[0013] Preferably, when the system is in the multi-battery multi-interface mode and off-grid, if the number of the bidirectional DC / DC units accessed by the energy storage module is n; the calculation formula of the bus voltage instruction value V dc_ref of the voltage outer loop is: V dc_ref =V dc_nom -r i ×i bati ; at this time, the calculation formula of the distribution coefficient k 2_n of the current sharing module is: ;

[0014] wherein, Vdc_nom This represents the initial setting value of the bus voltage, r. i This represents the droop coefficient corresponding to the i-th energy storage module, where i = {1, 2, ..., n}. bati This represents the operating current corresponding to the i-th energy storage module.

[0015] Preferably, when the system is in a multi-battery, multi-interface mode and connected to the grid, if the number of bidirectional DC / DC units connected to the energy storage module is n; then the current sharing module corresponds to the current shunting coefficient k of any bidirectional DC / DC unit. 2_i The calculation formula is as follows:

[0016] ;

[0017] ;

[0018] Where α represents the charge / discharge state judgment value of the energy storage module, and SOC i V represents the remaining power value of the energy storage module connected to any of the bidirectional DC / DC units. dc This indicates the collected bus voltage.

[0019] Compared with the prior art, the beneficial effects of this application are as follows:

[0020] The architecture of this application features input ports with multiple energy storage module connection methods and can adapt to different types of energy storage modules, offering greater flexibility. Furthermore, the system can automatically identify the connection method of the energy storage module based on the voltage and current values ​​of the input ports. The control loop can adapt to different energy storage module connection methods, effectively improving the system's applicability. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the overall architecture of this application.

[0022] Figure 2 This is a schematic diagram of one example of a bidirectional DC / DC unit in this application.

[0023] Figure 3 This is a schematic diagram of another example of a bidirectional DC / DC unit in this application.

[0024] Figure 4 This is a schematic diagram illustrating another example of the bidirectional DC / DC unit in this application.

[0025] Figure 5 This is a schematic diagram of the system architecture in the single-battery, single-interface mode of this application.

[0026] Figure 6The architecture schematic diagram of the system in the single battery and multiple interface mode in the present application.

[0027] Figure 7 The architecture schematic diagram of the system in the multiple battery and multiple interface mode in the present application.

[0028] Figure 8 The workflow schematic diagram of the system in the present application for working mode recognition.

[0029] Figure 9 The port voltage change schematic diagram of the system in the present application in the double battery and double interface mode.

[0030] Figure 10 The port voltage change schematic diagram of the system in the present application in the single battery and double interface mode.

[0031] Figure 11 The energy storage module type judgment flow schematic diagram of the system in the present application in the multiple battery and multiple interface mode.

[0032] Figure 12 The control loop schematic diagram of the present application. DETAILED DESCRIPTION

[0033] Hereinafter, the present application will be further described in conjunction with specific embodiments, and it should be noted that in the description of the present application, the description of the terms “one embodiment”, “some embodiments”, “an example”, “a specific example”, 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 the present specification, the illustrative description of the above terms should not be understood as necessarily referring to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in the present specification.

[0034] In the description of the present application, it should be noted that for orientation words, such as the terms “center”, “transverse”, “longitudinal”, “length”, “width”, “thickness”, “up”, “down”, “front”, “back”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inside”, “outside”, “clockwise”, “counterclockwise”, etc. The orientation and positional relationship shown in the drawing is based on the orientation or positional relationship shown in the drawing, and is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and cannot be understood as limiting the specific protection scope of the present application.

[0035] It should be noted that the terms "first", "second" and the like in the description and in the claims of the present application are used for distinguishing between similar objects and do not necessarily have a chronological or sequential order.

[0036] In the present application, unless specifically defined otherwise, the terms "mounting", "connected", "connection", "fixed", and the like, should be construed as broadly as possible, for example, can be a connection, or can be detachable connection, or can be integrated; can be mechanical connection, or can be electrical connection; can be directly connected, or can be indirectly connected through an intermediate medium; can be internal communication of two elements or interaction relationship between two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0037] In the present application, unless specifically defined otherwise, the first feature "on" or "under" the second feature can include that the first and second features are in direct contact, or can include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, the first feature "on", "above" and "over" the second feature includes that the first feature is directly above and obliquely above the second feature, or only indicates that the horizontal height of the first feature is higher than that of the second feature. The first feature "under", "below" and "under" the second feature includes that the first feature is directly below and obliquely below the second feature, or only indicates that the horizontal height of the first feature is less than that of the second feature.

[0038] In the present application, the terms "including", "having" and any other similar terms in the description and claims are intended to cover the inclusions not exclusively, for example, a process, method, system, product or device including a series of steps or units does not have to be limited to those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0039] As shown in one of the preferred embodiments of the present application, Figure 1 As shown in one of the preferred embodiments of the present application, a multi-mode energy storage system with multi-path battery interface includes an inverter architecture, multi-path bidirectional DC / DC units and a control loop. The multi-path bidirectional DC / DC units are connected in parallel to the DC side bus of the inverter architecture through the first end, and the second end of the bidirectional DC / DC unit is used to access the energy storage module. A single energy storage module can be connected with at least one bidirectional DC / DC unit, thereby forming multiple connection modes. The control loop can output the duty cycle of the corresponding bidirectional DC / DC unit according to the grid-connected or off-grid state of the inverter architecture and the connection mode of the energy storage module.

[0040] It can be understood that the inverter architecture can be an inverter architecture based on a photovoltaic power generation system, or an inverter architecture based on a wind power generation system or other new energy power generation system. For the convenience of understanding, the present application will be described in detail taking the inverter architecture of the photovoltaic power generation system as an example. The inverter architecture of the photovoltaic power generation system mainly includes a PV assembly, a DC / DC unit and a DC / AC unit; the PV assembly is connected to the input end of the DC / DC unit through the output end, the output end of the DC / DC unit is connected to the DC side of the DC / AC unit through a DC bus, and the AC side of the DC / AC unit is connected to the power grid and the load. In the grid-connected mode, the PV assembly or the subsequent connected energy storage module supplies power to the load, and in the off-grid mode, the power grid supplies power to the load. The multi-way bidirectional DC / DC unit of the present embodiment can be connected in parallel to the DC bus between the DC / DC unit and the DC / AC unit through the first end.

[0041] It should be understood that there are many specific types of energy storage modules, such as batteries and supercapacitors; the specific structure and working principle are known to those skilled in the art, and therefore will not be described in detail here.

[0042] In the present embodiment, there are many specific structures of the bidirectional DC / DC unit capable of connecting the energy storage module, in order to facilitate understanding, the following will be described in detail through three specific examples.

[0043] Example one: as shown in Figure 2 , the bidirectional DC / DC unit includes two switch bridge arm circuits and an LLC circuit, the two switch bridge arm circuits are respectively used as the input and output of the bidirectional DC / DC unit, and the two switch bridge arm circuits are connected through the LLC circuit. It should be noted that the bidirectional DC / DC unit under this structure can connect the low-voltage energy storage module, realize the electrical isolation between the low-voltage energy storage module and the high-voltage bus, improve the system safety, and also realize soft switching based on the LLC resonant cavity to reduce the switching loss. The specific structure of the switch bridge arm circuit is known to those skilled in the art, and only a simple description is made here; the switch bridge arm circuit is mainly connected in full-bridge through four switch tubes.

[0044] Example two: as shown in Figure 3 , the bidirectional DC / DC unit can adopt a Buck / Boost circuit, and the specific circuit structure is known to those skilled in the art, so it will not be described in detail here. It should be noted that through the voltage lifting adjustment of the Buck / Boost circuit, the bidirectional DC / DC unit under this structure can connect the high-voltage energy storage module.

[0045] Example three: as shown in Figure 4As shown, the structure of the bidirectional DC / DC unit of the present example is a combination of example one and example two, i.e. the composite topology of LLC + double-switch bridge arm circuit and Buck / Boost circuit. Thus, both electrical isolation and wide voltage regulation can be taken into account.

[0046] It should be understood that the above three examples can all meet the actual needs of the present application, and those skilled in the art can select the structure of the bidirectional DC / DC unit according to the performance of the energy storage module.

[0047] In the present embodiment, each bidirectional DC / DC unit can form an input port for connecting the energy storage module. Therefore, when connecting the energy storage module, only one bidirectional DC / DC unit can be connected with the energy storage module, or multiple bidirectional DC / DC units can be connected with the energy storage module. Therefore, through different connection modes of the energy storage module, the inverter architecture and the energy storage system formed by the bidirectional DC / DC unit can support multiple working modes. For the convenience of understanding, specific descriptions will be given below.

[0048] Specifically, as shown in Figure 5 When only one bidirectional DC / DC unit is connected with the energy storage module, the system is in a single battery single interface mode. It can be understood that since the bidirectional DC / DC unit is provided with n paths, the energy storage module can be selectively connected to the input end of any bidirectional DC / DC unit. In this connection mode, only the duty cycle of the bidirectional DC / DC unit connected with the energy storage module needs to be controlled to realize the charge and discharge control of the energy storage module. For the bidirectional DC / DC unit without input signal, only the switch tube needs to be ensured to be in the off state, i.e. in the non-working state.

[0049] As shown in Figure 6 When multiple bidirectional DC / DC units are connected with the same energy storage module, the system is in a single battery multiple interface mode. It can be understood that in this mode, the bidirectional DC / DC unit can support standby working mode and parallel working mode.

[0050] In standby working mode, the energy storage module can select the bidirectional DC / DC unit in the optimal state as the main circuit unit to work, i.e. responsible for the bidirectional energy flow between the energy storage module and the DC bus, while the remaining bidirectional DC / DC units are in standby state, thereby being redundant with the bidirectional DC / DC unit in the optimal state.

[0051] It should be understood that the redundant design in the standby working mode can ensure the reliability of the system. Once the main circuit unit cannot work normally due to excessive temperature or other abnormal conditions, the system can automatically switch to the standby bidirectional DC / DC unit to work, so as to ensure the continuous work of the energy storage module. When the main circuit unit works, in order to reduce the energy loss of the system, the other bidirectional DC / DC units can reduce unnecessary energy loss through "zero current standby".

[0052] In the parallel working mode, each bidirectional DC / DC unit works simultaneously. Compared with the single battery single interface mode, in this mode, each bidirectional DC / DC unit can share the total output / input current of the energy storage module, thereby reducing the working load of the single bidirectional DC / DC unit, avoiding device aging or damage caused by local overheating, and prolonging the overall service life of the circuit.

[0053] It can be understood that when the inverter architecture identifies that the system is in the single battery multi-interface mode, it can communicate with the BMS (battery management system) of the energy storage module to select the specific working mode in this connection mode. Specifically, the SOC (remaining capacity value) and working current of the energy storage module are collected; when the SOC of the energy storage module is low, the parallel working mode is preferred for fast charging; if the charge and discharge current of the energy storage module exceeds the rated current range of the bidirectional DC / DC unit, the parallel working mode is preferred to avoid single circuit overload; if a single bidirectional DC / DC unit can meet the charge and discharge power demand of the energy storage module, the standby working mode can be selected. For the energy storage module without integrated BMS, the specific working mode can be determined by the upper computer.

[0054] As shown in Figure 7 When multiple or all bidirectional DC / DC units are independently connected with energy storage modules, the system is in the multi-battery multi-interface mode. It can be understood that the energy storage modules connected by multiple or all bidirectional DC / DC units can be of the same type, or some or all of different types. When the multi-battery multi-interface mode is adopted, the total capacity of the energy storage modules is expanded due to the connection of multiple energy storage modules, which can realize greater load capacity. At the same time, the compatibility of the characteristics of different types of energy storage modules further enhances the flexibility of the system, which means that users can flexibly select the battery combination with higher cost-effectiveness and performance adaptation according to actual needs. In addition, the multi-energy storage module configuration also provides higher redundancy, so that even if one of the energy storage modules fails or its performance decreases, the remaining energy storage modules can still continue to supply power, thereby ensuring the continuous operation of the system.

[0055] In this embodiment, since the system has multiple different connection methods, it needs to have port identification capabilities, such as the type and connection method of the energy storage module connected to the interface, in order to accurately identify and adapt to various connection configurations, thereby adjusting the working mode of the control loop to achieve flexible control of the charging and discharging of the energy storage module. Figure 8 As shown, the system's identification and judgment process for single-battery single-interface mode, single-battery multi-interface mode, and multi-battery multi-interface mode is as follows: Each bidirectional DC / DC unit is controlled to operate for a period of time in a time-sharing manner, while the remaining bidirectional DC / DC units are blocked; the duty cycle of each bidirectional DC / DC unit remains consistent during operation to ensure the accuracy of the identification process. When each bidirectional DC / DC unit is operating, the voltage and current values ​​at the input ports of each bidirectional DC / DC unit are detected; taking n bidirectional DC / DC units as an example, the detected input port voltage value is: u bat1 u bat2 ... u batn The input port current value is: i dc1 i dc2 ... dcn If the current value corresponding to each input port is zero, it can be determined that no energy storage module is connected to the system. If only one input port has a non-zero current value, it can be determined that the system is in single-battery single-interface mode. If multiple input ports have non-zero current values, the system may be in single-battery multi-interface mode or multi-battery multi-interface mode. The voltage values ​​of the multiple input ports can then be analyzed. If the voltage values ​​of the input ports with non-zero current values ​​remain consistent, it can be determined that the system is in single-battery multi-interface mode; if the voltage values ​​of the input ports with non-zero current values ​​do not remain consistent, it can be determined that the system is in multi-battery multi-interface mode.

[0056] To facilitate understanding of the single-cell multi-interface mode and multi-cell multi-interface mode judgment when the current value corresponding to multiple input ports is non-zero, the following analysis will use a two-channel bidirectional DC / DC unit, i.e., n is 2, as an example to explain the specific judgment process in detail. The two bidirectional DC / DC units are labeled as bidirectional DC / DC#1 and bidirectional DC / DC#2, respectively.

[0057] Specifically, such as Figure 9 The diagram shows the port voltage of the system in dual-battery interface mode. The energy storage module corresponding to bidirectional DC / DC#1 is defined as energy storage module #1, and the energy storage module corresponding to bidirectional DC / DC#2 is defined as energy storage module #2. As shown in the diagram, when bidirectional DC / DC#1 is working while bidirectional DC / DC#2 is not working, the circuit port voltage u is lower because energy storage module #1 is in a discharging state. bat1This means that the operating voltage of energy storage module #1 is decreasing. Meanwhile, energy storage module #2 is in an open-circuit state, therefore the circuit port voltage u... bat2 It remains essentially unchanged. Subsequently, both bidirectional DC / DC units cease operation, and the circuit port voltage u... bat1 and u bat2 All remain essentially unchanged. When bidirectional DC / DC#2 is working while bidirectional DC / DC#1 is not working, the energy storage module # is in an open circuit state, therefore the circuit port voltage u bat1 The voltage remained essentially unchanged; however, the discharge of energy storage module #2 caused the circuit port voltage to... bat2 It is in a decreasing state, that is, in this connection mode, the circuit port voltage u bat1 and u bat2 The changes vary considerably.

[0058] like Figure 10 The diagram shows the port voltages of the system in single-battery dual-interface mode. The input port voltages of the two bidirectional DC / DC units are shown in the figure. bat1 and u bat2 In reality, both voltages represent the operating voltage of the connected energy storage module. Therefore, regardless of whether bidirectional DC / DC#1 or bidirectional DC / DC#2 is operating, the energy storage module is in a discharging state, i.e., the circuit port voltage u... bat1 and u bat2 All decreased and remained consistent.

[0059] In this embodiment, when the system identifies the input ports, if it finds that they are connected in a multi-battery, multi-interface mode, and the voltage values ​​of multiple input ports are at the same level within a certain time period, this may lead the system to misjudge that the energy storage modules connected to the multiple interfaces are of the same type. However, this situation may also occur when different types of energy storage modules are connected. Therefore, in order to ensure the stable operation of the system and the effective performance of the energy storage modules, it is necessary to further determine whether the energy storage modules connected to each input interface are of the same type. Figure 11 As shown, the specific identification process for energy storage module types is as follows: Simultaneously control multiple bidirectional DC / DC units to operate with the same duty cycle, or control the energy storage modules corresponding to multiple input ports to charge and discharge under the same constant current conditions. Detect the port voltage and current of the multiple bidirectional DC / DC units. If the voltage and current change rates of the multiple input ports are consistent, it can be determined that the energy storage modules connected to the multiple input ports are of the same type. Conversely, if the detection results show significant differences in the voltage and current change rates of the multiple input ports, it indicates that the connected energy storage modules have significantly different energy characteristics, thus it can be determined that different types of energy storage modules are connected to the multiple input ports.

[0060] In this embodiment, as described above, the system can form multiple operating modes based on the number and method of connection of energy storage modules. Therefore, to ensure stable switching between these modes, the system's control loop needs to be designed. Specifically, a positive current value on the energy storage module side indicates it is in a charging state, while a negative current value indicates it is in a discharging state. The maximum discharge current of the energy storage module is i. discharge The maximum charging current is i charge The control method for the PV unit side of the system is consistent with the conventional method, namely, MPPT tracking or load-limited operation. The specific control process is well known to those skilled in the art, so it will not be described in detail here.

[0061] like Figure 12 As shown, the control loop on the energy storage module side includes a voltage outer loop, a maximum value acquisition module, a current sharing module, a limiting module, and multiple duty cycle generation modules. The voltage outer loop acquires the bus voltage V. dc With bus voltage command value V dc_ref After comparison, the PI controller calculates the first current setpoint i. batref1 For the obtained first current given value i batref1 After being assigned a weight coefficient k1, it serves as one of the inputs to the maximum value module. This input can be represented as k1+i batref1 The other input to the maximum value module is the second current setpoint i issued by the ARM. batref2 The maximum value module takes the maximum value of the two inputs as the current setpoint i on the battery side. bat * It then outputs the current to the current sharing module. The current sharing module can adjust the current setpoint i according to the system's connection mode. bat * The current is shunted by the shunting coefficient k2, thereby obtaining the current setpoint i for the corresponding n-channel bidirectional DC / DC unit. bat1_1 * i bat2_1 * ... batn_1 * The shunt current setpoint is then sent to the limiting module. The limiting module can limit the shunt value and send it to multiple duty cycle generation modules. Each duty cycle generation module can then compare the input shunt value with the current sampling value i from the corresponding bidirectional DC / DC unit. bat The comparison is performed, and the duty cycles d1, d2, ..., d of the corresponding bidirectional DC / DC units are generated after passing through the PI controller. n This enables effective control over the charging and discharging of the energy storage module.

[0062] To facilitate understanding, the following will use two bidirectional DC / DC units, namely bidirectional DC / DC#1 and bidirectional DC / DC#2, as examples to describe in detail the specific working process of the current sharing module and the amplitude limiting module in the control loop. Figure 12 As shown, when the maximum value module outputs the given current i bat * After the current sharing module is applied, since the sum of the shunt coefficients of all corresponding bidirectional DC / DC units is 1, the shunt coefficient corresponding to bidirectional DC / DC#1 is k2. Therefore, the shunt coefficient corresponding to bidirectional DC / DC#2 can be represented by 1-k2. The current sharing module can output the current setpoint i corresponding to bidirectional DC / DC#1 and bidirectional DC / DC#2 respectively. bat1_1 * and i bat2_1 * Current setpoint i bat1_1 * and i bat2_1 * After passing through the corresponding limiting modules, a new current setpoint i can be generated. bat1 * and i bat2 * Then, the port current values ​​i of the two bidirectional DC / DC units are sampled respectively. bat1 and i bat2 With the corresponding current setpoint i bat1 * and i bat2 * The difference is used as the input to the PI controller, and then the duty cycle d1 and duty cycle d2 of the bidirectional DC / DC#1 are obtained.

[0063] It should be understood that the outer voltage loop is a control loop that determines the current loop setpoint based on the bus voltage loop. The energy storage module can control the bus voltage through a bidirectional DC / DC unit. The weighting coefficient k1 is mainly used to weaken the effect of the outer voltage loop when the system is in grid-connected mode. The limiting module is used to prevent overcurrent damage to the energy storage module; specifically, when the energy storage module is discharging, it is necessary to limit the operating current of the energy storage module to not exceed a given threshold I. limit1 When the energy storage module is charging, the operating current of the energy storage module needs to be limited to not exceed a given threshold I. limit2 This ensures that the operating current of the energy storage module is always limited to the safe range that the energy storage module can withstand.

[0064] It is understandable that for parameters k1, k2, and I... limit1 and I limit2 This can be configured through parameter configuration modules. Specifically, for example... Figure 12As shown, when the system detects the connection mode of the input port, combined with the maximum charging and discharging current of the energy storage module and the system's grid-connected / off-grid operating mode, it can communicate with the ARM through the parameter configuration module, thereby controlling the parameters k1, k2, and I in the control loop. limit1 and I limit2 Configuration is performed to ensure that the energy storage module can charge and discharge safely and effectively under various connection modes. For ease of understanding, the specific design process for the above parameters will be described in detail below.

[0065] Specifically, when the system is in grid-connected mode, the weighting coefficient k1 assigned to the outer voltage loop takes the value of -∞, and then the input k1+i of the maximum value module... batref1 This can be viewed as tending towards -∞; when the system is in off-grid mode, the weighting coefficient assigned to the outer voltage loop is 0, and then k1+i serves as the input k1+i to the maximum value module. batref1 That is, i batref1 This means that when the system is in grid-connected mode, the outer voltage loop will fail and will not participate in the regulation of the control loop; when the system is in off-grid mode, the outer voltage loop will be activated, and the energy storage module will control the bus voltage through the bidirectional DC / DC unit.

[0066] At the same time, the second current setpoint i issued by the ARM batref2 It is also related to the grid connection / off-grid mode of the system; when the system is in grid connection mode, the ARM can calculate the second current setpoint i based on the operating power of the energy storage module and the bus voltage. batref2 In off-grid mode, the ARM directly sets the second current setpoint i. batref2 The value is -∞, which means the second current setpoint i in this mode. batref2 It does not require ARM computation to generate.

[0067] Based on the above, it can be seen that when the system is in off-grid mode, the maximum value module outputs the current setpoint i. bat * The current setpoint i is determined by the voltage outer loop; when the system is in grid-connected mode, the maximum value module outputs the current setpoint i. bat * The value is determined by the value issued by the ARM.

[0068] For parameters k2, I limit1 and I limit2 The design is related to the specific connection mode of the energy storage module. The following will describe the three connection modes in detail.

[0069] (1) When the input port is in single-battery single-interface mode, only one bidirectional DC / DC unit operates. If the input current value i of a certain bidirectional DC / DC unit is detected during the identification process...dci If the value is not always zero, it indicates that the energy storage module is connected to the input port of the bidirectional DC / DC unit. At this time, the value of the shunt coefficient k2 of the current sharing module corresponding to the bidirectional DC / DC unit is 1, that is, the control loop only controls the duty ratio of the bidirectional DC / DC unit. For other bidirectional DC / DC units in the non-working state, the value of the corresponding shunt coefficient k2 is 0. Correspondingly, at this time, the threshold I limit1 of the limiting module can take the maximum charging current value i charge of the energy storage module. limit2 The threshold I discharge may take the maximum discharging current i limit1 of the energy storage module.

[0070] (2) When the input port is in the single battery multi-interface mode, if the standby working mode is adopted, the control process of the control loop is consistent with that of the single battery single interface. If the parallel working mode is adopted, n (n>1) bidirectional DC / DC units need to work together at this time. The n bidirectional DC / DC units need to take power from the energy storage module at the same time and control the bus voltage, so the value of the shunt coefficient k2 in the current sharing module is 1 / n. Since the n bidirectional DC / DC units access the same energy storage module at this time, the sum of the current limiting values of each path in the limiting module is the maximum charging and discharging current value of the energy storage module; that is, the threshold I limit1 of the limiting module at this time can take 1 / n×i charge , and the threshold I limit2 may take 1 / n×i discharge .

[0071] (3) When the input port is in the multi-battery multi-interface mode, although the input end can be connected to the same type of energy storage module, the specific charging and discharging conditions of n (n>1) energy storage modules are not necessarily completely consistent, in addition, the input end may also be connected to different types of energy storage modules, so the shunt coefficient k2 in the current sharing module can be set according to the charging and discharging conditions of each energy storage module and the on-grid or off-grid state of the system. It needs to be noted that in order to avoid the system efficiency being reduced due to the fact that some energy storage modules complete charging or discharging in advance, it is necessary to make the n energy storage modules basically maintain simultaneous charging or discharging.

[0072] When the system is in the off-grid state, the current sharing module needs to work cooperatively with the voltage outer loop, so the droop control can be adopted in the voltage outer loop to calculate the voltage outer loop instruction value V dc_ref ; the specific calculation formula is: V dc_ref =V dc_nom -r i ×i bati . Wherein, V dc_nom represents the initial setting value of the bus voltage; r irepresents the droop coefficient corresponding to the i-th energy storage module, i={1, 2, …, n}, the droop coefficient r i The specific value for realizing the equalization of each energy storage module is related to the SOC of each energy storage module; i bati represents the working current corresponding to the i-th energy storage module. At this time, the shunt coefficient k 2_n of the current sharing module is calculated as follows:

[0073] (1).

[0074] When the system is in the grid-connected state, the shunt coefficient k 2_i of the current sharing module corresponding to any road bidirectional DC / DC unit is calculated as follows:

[0075] (2).

[0076] .

[0077] wherein, a represents the state judgment value of the energy storage module charging and discharging, SOC i represents the residual capacity value of the energy storage module connected by any road bidirectional DC / DC unit, V dc represents the collected bus voltage.

[0078] It should be known that, according to the above formulas (1) and (2), when the bus voltage instruction value is greater than the bus voltage, the energy storage module is in the discharging state, at this time, the parameters in the current sharing module will be determined by the SOC of each energy storage module, that is, the amount of electricity that the energy storage module can continue to discharge determines. When the bus voltage instruction value is less than the bus voltage, the energy storage module is in the charging state, at this time, the parameters in the current sharing module will be determined by (1-SOC) of each energy storage module, that is, the amount of electricity that the energy storage module can continue to charge determines.

[0079] The value of the limiting module depends on the maximum charging and discharging current value of the connected energy storage module. If the multiple energy storage modules are of the same type, the threshold I limit1 of each limiting module corresponding to the multiple bidirectional DC / DC units is valued as i charge , and the threshold I limit2 is valued as i discharge . If the energy storage modules are of different types, the threshold I limit1 in the limiting module corresponding to any road bidirectional DC / DC unit is valued as i charge of the connected energy storage module, and the threshold I limit2 is valued as i discharge .

[0080] The foregoing describes the basic principles, main features and advantages of the present application. Those skilled in the art should understand that the present application is not limited to the above-described embodiments, and the above-described embodiments and descriptions in the specification are only the principles of the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the claimed present application. The scope of protection claimed by the present application is defined by the appended claims and their equivalents.

Claims

1. A multi-mode energy storage system with a multi-path battery interface, characterized by, Comprising: an inverter architecture; a plurality of bidirectional DC / DC units; a plurality of said bidirectional DC / DC units are connected in parallel to a DC bus of said inverter architecture through a first end, and a second end of said bidirectional DC / DC units is used to access an energy storage module; a single said energy storage module is adapted to be connected to at least one said bidirectional DC / DC unit, thereby forming a plurality of connection modes; and a control loop; said control loop is adapted to output a duty cycle corresponding to said bidirectional DC / DC unit according to an off-grid state of said inverter architecture and a connection mode of said energy storage module; said control loop comprises: a voltage outer loop; said voltage outer loop compares a bus voltage with a bus voltage command value, and then calculates a first current given value through a PI controller, and then assigns a weight coefficient to the obtained first current given value as one of the inputs of a maximum value module; a maximum value module; another input of said maximum value module is a second current given value issued by an ARM, and said maximum value module outputs the maximum value of the two inputs as a current given value of a battery side and sends it to a current sharing module; a current sharing module; said current sharing module is adapted to distribute the current given value according to the connection mode of the system and send it to an amplitude limiting module; an amplitude limiting module; said amplitude limiting module is adapted to limit the amplitude of the distributed value and send it to a plurality of duty cycle generation modules; and a plurality of duty cycle generation modules; each said duty cycle generation module is adapted to compare the input distributed value with a current sampling value of a corresponding said bidirectional DC / DC unit, and then generate a duty cycle of the corresponding said bidirectional DC / DC unit through a PI controller.

2. The multi-mode energy storage system of claim 1, wherein, When only one said bidirectional DC / DC unit is connected with said energy storage module, the system is in a single battery single interface mode; When a plurality of said bidirectional DC / DC units are connected with the same said energy storage module, the system is in a single battery multiple interface mode; When a plurality of or all said bidirectional DC / DC units are independently connected with said energy storage module, the system is in a multiple battery multiple interface mode.

3. The multi-mode energy storage system of claim 2, wherein, When the system is in a single battery multiple interface mode, said bidirectional DC / DC unit supports a standby operation mode and a parallel operation mode; In the standby operation mode, said energy storage module selects said bidirectional DC / DC unit with the optimal state as a main circuit unit to work, and the remaining said bidirectional DC / DC units are redundant to said bidirectional DC / DC unit with the optimal state; In the parallel operation mode, each said bidirectional DC / DC unit works simultaneously, thereby reducing the working load of a single said bidirectional DC / DC unit.

4. The multi-mode energy storage system of claim 3, wherein, For the selection of the standby operation mode and the parallel operation mode, it is adapted to adjust according to the working data collection of said energy storage module, which specifically includes the following processes: collecting the SOC value and working current of said energy storage module; if the SOC value of said energy storage module is lower than a set threshold, said DC / DC unit selects the parallel operation mode to charge said energy storage module; if the working current of said energy storage module exceeds the rated current, said DC / DC unit selects the parallel operation mode to distribute. If the single DC / DC unit meets the working power demand of the energy storage module, the DC / DC unit selects a standby working mode to work.

5. The multi-mode energy storage system of claim 2, wherein, The system performs the single battery single interface mode, single battery multiple interface mode and multiple battery multiple interface mode judgment process as follows: Each of the bidirectional DC / DC units is controlled to work in time-sharing mode, and the remaining bidirectional DC / DC units are blocked; When each of the bidirectional DC / DC units works, the voltage value and current value of the input port of each of the bidirectional DC / DC units are detected; If the current values corresponding to each of the input ports are all zero, it is judged that the system has no access to the energy storage module; If only one of the input ports has a non-zero current value, it is judged that the system is in single battery single interface mode; If multiple input ports have non-zero current values, and the voltage values of the input ports with non-zero current values remain consistent, it is judged that the system is in single battery multiple interface mode; If multiple input ports have non-zero current values, and the voltage values of the input ports with non-zero current values do not remain consistent, it is judged that the system is in multiple battery multiple interface mode.

6. The multi-mode energy storage system of claim 5, wherein, When the system is in multiple battery multiple interface mode, if the voltage values of multiple input ports are at the same level, the type of the corresponding accessed energy storage module needs to be judged, which includes the following process: Simultaneously control multiple bidirectional DC / DC units to work at the same duty cycle, or control the corresponding energy storage modules of multiple input ports to work under the same constant current condition; Detect the port voltage and current of multiple bidirectional DC / DC units, if the voltage and current change rates of multiple input ports are consistent, it is judged that the types of the energy storage modules accessed by multiple input ports are the same; Otherwise, it is judged that the types of the energy storage modules accessed by multiple input ports are different.

7. The multi-mode energy storage system of any one of claims 2-6, wherein, When the system is in grid-connected mode, the weight coefficient given in the voltage outer loop is -∞; at the same time, the ARM calculates the second current given value according to the working power of the energy storage module and the bus voltage; When the system is in off-grid mode, the weight coefficient given in the voltage outer loop is 0; at the same time, the ARM directly sets the second current given value to -∞.

8. The multi-mode energy storage system of any one of claims 2-6, wherein, When the system is in multiple battery multiple interface mode and off-grid, if the number of bidirectional DC / DC units accessed by the energy storage module is n; The bus voltage command value V of the voltage outer loop dc_ref The calculation formula is: V dc_ref =V dc_nom -r i ×i bati ; At this time, the shunt coefficient k of the current sharing module 2_n The calculation formula is: ; wherein V dc_nom represents the initial setting value of bus voltage, r i represents the droop coefficient corresponding to the i-th energy storage module, i={1, 2, …, n}, i bati represents the working current corresponding to the i-th energy storage module.

9. The multi-mode energy storage system of any one of claims 2-6, wherein, When the system is in multiple battery multiple interface mode and grid-connected, if the number of bidirectional DC / DC units accessed by the energy storage module is n; At this time, the current sharing module corresponds to the shunt coefficient k of any road bidirectional DC / DC unit 2_i The calculation formula is as follows: ； ； Wherein, a represents the energy storage module charge and discharge state judgment value, SOC i represents the remaining capacity value of the energy storage module connected by the bidirectional DC / DC unit, V dc represents the collected bus voltage.

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