Multi-mode energy storage system with multiple battery interfaces

Abstract

The invention discloses a multi-mode energy storage system with multiple paths of battery interfaces. The multi-mode energy storage system comprises an inverter framework and multiple paths of bidirectional DC / DC units, the multi-path bidirectional DC / DC unit is connected in parallel with a direct current side bus of the inverter framework through a first end, and a second end of the bidirectional DC / DC unit is used for accessing an energy storage module; the single energy storage module is suitable for being connected with at least one bidirectional DC / DC unit so as to form a plurality of connection modes; the control loop is suitable for outputting the duty ratio of the corresponding bidirectional DC / DC unit according to the grid-connected and off-grid state of the inverter architecture and the connection mode of the energy storage module. The architecture has the beneficial effects that the architecture input port has multiple energy storage module connection modes, can adapt to different types of energy storage modules, and has higher flexibility. And 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 the applicability of the system can be effectively improved.

Description

Technical Field

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

[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 energy of the power generation system is excessive.

[0003] The energy storage module mainly uses a storage battery; currently, when designing an energy storage system, often only a single battery interface is designed, 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 leads to a large amount of human, material and time costs in the system design, development and operation and maintenance processes, but also increases the risk of system failures and the complexity of maintenance. Summary of the Invention

[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 defect in the above background art.

[0005] To achieve at least one of the above purposes, the technical solution adopted in the present application is: a multi-mode energy storage system with multiple battery interfaces, including 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 a second end of the bidirectional DC / DC unit is used to connect to an energy storage module; a single energy storage module is adapted to be connected to at least one of the bidirectional DC / DC units, thereby forming multiple connection modes; the control loop is adapted to output a duty cycle corresponding to the bidirectional DC / DC unit according to the grid-connected and off-grid states of the inverter architecture and the connection mode of the energy storage module.

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

[0007] Preferably, when the system is in the single-battery multi-interface mode, the bidirectional DC / DC unit supports a standby working mode and a parallel working mode; in the standby working mode, the energy storage module selects the bidirectional DC / DC unit in the best state as the main circuit unit to work, and the remaining bidirectional DC / DC units are redundant with the bidirectional DC / DC unit in the best state; in the parallel working mode, each of the bidirectional DC / DC units works simultaneously, thereby reducing the workload of a single bidirectional DC / DC unit.

[0008] Preferably, the selection of the standby working mode and the parallel working mode is suitable for adjustment according to the working data collection of the energy storage module, which specifically includes the following processes: collecting the SOC value and the 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 working mode to charge the energy storage module; if the working current of the energy storage module exceeds the rated current, the DC / DC unit selects the parallel working mode for current diversion; if the single-channel DC / DC unit meets the working power requirement of the energy storage module, the DC / DC unit selects the standby working mode to work.

[0009] Preferably, the process of the system judging the single-battery single-interface mode, the single-battery multi-interface mode and the multi-battery multi-interface mode is as follows: control each of the bidirectional DC / DC units to work in time-sharing mode one by one, and at the same time block the wave of the other bidirectional DC / DC units; when each of the bidirectional DC / DC units is working, detect the voltage value and current value of the input port of each bidirectional DC / DC unit; if the current values ​​corresponding to the input ports are all zero, it is judged that the system has no access to the energy storage module; if there is only one input port corresponding to a non-zero current value, it is judged that the system is in the single-battery single-interface mode; if there are multiple input ports corresponding to non-zero current values, and the voltage values ​​of the input ports with non-zero current values ​​are always consistent, it is judged that the system is in the single-battery multi-interface mode; if there are multiple input ports corresponding to non-zero current values, and the voltage values ​​of the input ports with non-zero current values ​​are not always 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 and multi-interface mode, if the voltage values of the multiple input ports are at the same level, it is necessary to judge the types of the corresponding connected energy storage modules. The specific process is as follows: simultaneously control the multiple bidirectional DC / DC units to work with the same duty cycle, or control the energy storage modules corresponding to the multiple input ports to charge and discharge under the same constant current condition; detect the port voltages and currents of the multiple bidirectional DC / DC units. If the change rates of the voltages and currents of the multiple input ports are the same, it is judged that the types of the energy storage modules connected to the multiple input ports are the same; otherwise, it is judged that the types of the energy storage modules connected to the multiple input ports are different.

[0011] Preferably, the control loop includes a voltage outer loop, a maximum value module, a current sharing module, a limiting module, and multiple duty cycle generation modules; after the voltage outer loop compares the collected bus voltage with the bus voltage command value, it calculates the first current reference value through a PI controller, and after assigning a weight coefficient to the obtained first current reference value, it serves as one of the inputs of the maximum value module; the other input of the maximum value module is the second current reference value sent by the ARM. The maximum value module takes the maximum value of the two inputs as the current reference value on the battery side and outputs it to the current sharing module; the current sharing module is adapted to shunt the current reference value according to the connection mode of the system and send it to the limiting module; the limiting module is adapted to limit the shunted value and then send it to the multiple duty cycle generation modules respectively; each duty cycle generation module is adapted to compare the input shunted value with the current sampling value of the corresponding bidirectional DC / DC unit, and 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 given in the voltage outer loop is -∞; at the same time, the ARM calculates the second current reference 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 given in the voltage outer loop is 0; at the same time, the ARM directly sets the second current reference value to -∞.

[0013] Preferably, when the system is in the multi-battery and multi-interface mode and is off-grid, if the number of the bidirectional DC / DC units with the energy storage module connected is n; the bus voltage command value V dc_ref of the voltage outer loop is calculated by the formula: V dc_ref =V dc_nom -r i ×i bati ; at this time, the shunt coefficient k 2_n of the current sharing module is calculated by the formula: ; where, V dc_nomrepresents the initial set value of the 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.

[0014] Preferably, when the system is in the multi-battery multi-interface mode and is connected to the grid, if the number of paths of the bidirectional DC / DC units with the energy storage modules connected is n; at this time, the shunt coefficient k of the current sharing module corresponding to any path of the bidirectional DC / DC units 2_i is calculated as follows: ; ; where α represents the judgment value of the charge and discharge state of the energy storage module, SOC i represents the remaining power value of the energy storage module connected to any path of the bidirectional DC / DC units, V dc represents the collected bus voltage.

[0015] Compared with the prior art, the beneficial effects of this application are as follows: The input port of the architecture of this application has multiple connection methods for energy storage modules and can adapt to different types of energy storage modules, with stronger flexibility. And the system can automatically identify the connection method of the energy storage module according to the voltage value and current value of the input port. The control loop can adapt to different connection methods of energy storage modules, which can effectively improve the applicability of the system. Description of the Drawings

[0016] Figure 1 is the overall architecture schematic diagram of this application.

[0017] Figure 2 is the structural schematic diagram of one example of the bidirectional DC / DC unit in this application.

[0018] Figure 3 is the structural schematic diagram of another example of the bidirectional DC / DC unit in this application.

[0019] Figure 4 is the structural schematic diagram of yet another example of the bidirectional DC / DC unit in this application.

[0020] Figure 5 is the architecture schematic diagram of the system in the single-battery single-interface mode in this application.

[0021] Figure 6 is the architecture schematic diagram of the system in the single-battery multi-interface mode in this application.

[0022] Figure 7Schematic diagram of the architecture of the system in the multi-battery and multi-interface mode in this application.

[0023] Figure 8 Schematic diagram of the workflow for the system to identify the working mode in this application.

[0024] Figure 9 Schematic diagram of the port voltage change when the system works in the dual-battery and dual-interface mode in this application.

[0025] Figure 10 Schematic diagram of the port voltage change when the system works in the single-battery and dual-interface mode in this application.

[0026] Figure 11 Schematic diagram of the process for judging the energy storage module type when the system is in the multi-battery and multi-interface mode in this application.

[0027] Figure 12 Schematic diagram of the control loop of this application. Detailed implementation manners

[0028] Next, in combination with the detailed implementation manners, this application will be further described. It should be noted that in the description of this specification, the descriptions with reference to terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions 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 a suitable manner in any one or more embodiments or examples. In addition, those skilled in the art can combine and combine the different embodiments or examples described in this specification.

[0029] In the description of this application, it should be noted that for the orientation terms, if there are terms such as "center", "horizontal", "longitudinal", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc., indicating the orientation and position relationship is based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing this application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and cannot be understood as limiting the specific protection scope of this application.

[0030] It should be noted that the terms "first", "second", etc. in the description and claims of this application are used to distinguish similar objects and do not necessarily need to describe a specific order or sequence.

[0031] In this application, unless otherwise clearly defined or limited, terms such as "install", "connect", "link", "fix", etc. shall be understood in a broad sense. For example, it can be a connection, a detachable connection, or integrated; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two components or the interaction relationship between two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0032] In this application, unless otherwise clearly defined or limited, the first feature being "on" or "under" the second feature may include the direct contact between the first and second features, or may include the situation where the first and second features are not in direct contact but in contact through other features therebetween. Moreover, the first feature being "above", "over" and "on top of" the second feature includes that the first feature is directly above and obliquely above the second feature, or merely means that the horizontal height of the first feature is higher than that of the second feature. The first feature being "under", "beneath" and "underneath" the second feature includes that the first feature is directly below and obliquely below the second feature, or merely means that the horizontal height of the first feature is lower than that of the second feature.

[0033] The terms "comprise" and "have" and any variations thereof in the description and claims of this application are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that comprises a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these process, method, product or device.

[0034] One preferred embodiment of this application is, as Figure 1 shown, a multi-mode energy storage system with a multi-way battery interface, including an inverter architecture, a multi-way bidirectional DC / DC unit, and a control loop. The multi-way bidirectional DC / DC unit is 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 to at least one bidirectional DC / DC unit, thereby forming multiple connection modes. The control loop can output the duty ratio of the corresponding bidirectional DC / DC unit according to the grid-connected / off-grid state of the inverter architecture and the connection mode of the energy storage module.

[0035] 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 systems. For the convenience of understanding, this application will take the inverter architecture of a photovoltaic power generation system as an example for detailed description. The inverter architecture of a photovoltaic power generation system mainly includes PV modules, a DC / DC unit, and a DC / AC unit; the PV modules are 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, power is supplied to the load through the PV modules or the subsequent connected energy storage module. In the off-grid mode, power is supplied to the load through the power grid. The multi-way bidirectional DC / DC unit of this embodiment can be connected in parallel to the DC bus between the DC / DC unit and the DC / AC unit through the first end.

[0036] It should be known that there are various specific types of energy storage modules, such as storage batteries and supercapacitors, etc.; the specific structures and working principles are well-known to those skilled in the art, so they will not be elaborated in detail here.

[0037] In this embodiment, there are various specific structures of the bidirectional DC / DC unit that can realize the access of the energy storage module. For the convenience of understanding, the following will be described in detail through three specific examples.

[0038] Example 1: As Figure 2 shown, the bidirectional DC / DC unit includes two switch bridge arm circuits and an LLC circuit. The two switch bridge arm circuits serve as the input and output of the bidirectional DC / DC unit respectively, and the two switch bridge arm circuits are connected through the LLC circuit. It should be known that the bidirectional DC / DC unit under this structure can access a low-voltage energy storage module, realize electrical isolation between the low-voltage energy storage module and the high-voltage bus, improve system safety, and can also achieve soft switching based on the LLC resonant cavity to reduce switching losses. The specific structure of the switch bridge arm circuit is well-known to those skilled in the art and will only be briefly described here; the switch bridge arm circuit is mainly formed by full-bridge connection through four switching tubes.

[0039] Example 2: As Figure 3 shown, the bidirectional DC / DC unit can adopt a Buck / Boost circuit. The specific circuit structure is well-known to those skilled in the art, so it will not be elaborated in detail here. It should be known that through the voltage boost adjustment of the Buck / Boost circuit, the bidirectional DC / DC unit under this structure can access a high-voltage energy storage module.

[0040] Example 3: As Figure 4As shown, the structure of the bidirectional DC / DC unit in this example is a combination of Example 1 and Example 2, that is, a composite topology of LLC + dual-switch bridge arm circuit and Buck / Boost circuit. Thus, electrical isolation and wide voltage regulation can be taken into account.

[0041] It should be known that the above three examples can all meet the actual needs of this 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.

[0042] In this embodiment, each bidirectional DC / DC unit can form an input port for connecting the energy storage module; then when connecting the energy storage module, it can be that only one bidirectional DC / DC unit is connected to the energy storage module, or multiple bidirectional DC / DC units are all connected to the energy storage module. Therefore, through different connection methods of the energy storage module, the energy storage system formed by the inverter architecture and the bidirectional DC / DC unit can support multiple working modes. For the convenience of understanding, specific descriptions will be given below.

[0043] Specifically, as Figure 5 shown, when only one bidirectional DC / DC unit is connected to the energy storage module, the system is in the single-battery single-interface mode. It can be understood that since there are n bidirectional DC / DC units, the energy storage module can be selectively connected to the input end of any bidirectional DC / DC unit. In this connection method, only by controlling the duty cycle of the bidirectional DC / DC unit connected to the energy storage module, the charge and discharge control of the energy storage module can be realized. For the bidirectional DC / DC unit without an input signal, it only needs to ensure that all its switching tubes are in the off state, that is, to remain in the non-working state.

[0044] As Figure 6 shown, when multiple bidirectional DC / DC units are connected to the same energy storage module, the system is in the single-battery multi-interface mode. It can be understood that in this mode, the bidirectional DC / DC unit can support the standby working mode and the parallel working mode.

[0045] In the standby working mode, the energy storage module can select the bidirectional DC / DC unit with the best state as the main circuit unit to work, that is, to be responsible for the bidirectional energy flow between the energy storage module and the DC bus, while the remaining bidirectional DC / DC units are in the standby state, and thus are redundant with the bidirectional DC / DC unit with the best state.

[0046] It should be noted that the redundant design in the standby working mode can ensure the reliability of the system. Once the main circuit unit fails to work properly due to overheating or other abnormal conditions, the system can automatically switch to the standby bidirectional DC / DC unit to work, so as to ensure the continuous operation of the energy storage module. When the main circuit unit is working, in order to reduce the energy loss of the system, other bidirectional DC / DC units can reduce unnecessary energy loss through "zero-current standby".

[0047] In the parallel working mode, each bidirectional DC / DC unit works simultaneously. At this time, compared with the connection method of the single-battery single-interface mode, each bidirectional DC / DC unit in this mode can jointly share the total output / input current of the energy storage module, thereby reducing the working load of a single bidirectional DC / DC unit, avoiding device aging or damage caused by local overheating, and thus extending the overall service life of the circuit.

[0048] It can be understood that when the inverter architecture identifies that the system is in the connection state of the single-battery multi-interface mode, it can communicate with the BMS (Battery Management System) of the energy storage module to select which specific working mode to be in under this connection method. Specifically, the SOC (State of Charge) 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 preferably selected 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 preferably selected to avoid overloading of a single circuit; if a single bidirectional DC / DC unit can meet the charge and discharge power requirements of the energy storage module, the standby working mode can be selected. For the energy storage module without an integrated BMS, the specific working mode can be determined by the host computer.

[0049] As Figure 7 shown, when multiple or all bidirectional DC / DC units are independently connected to the energy storage module, 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 partially or all of different types of energy storage modules. When the multi-battery multi-interface mode is adopted, due to the access of multiple energy storage modules, the total capacity of the energy storage module is expanded, and a greater load-carrying capacity can be achieved. At the same time, the characteristic of being compatible with different types of energy storage modules further enhances the flexibility of the system, which means that users can flexibly select a more cost-effective and better-matched battery combination according to actual needs. In addition, the multi-energy storage module configuration also provides a higher redundancy. Even if one of the energy storage modules fails or its performance deteriorates, the remaining energy storage modules can still continue to supply power, thus ensuring the continuous operation of the system.

[0050] In this embodiment, since the system has a variety of different connection modes, the system needs to have port identification capabilities, such as the type and connection mode of the energy storage module connected to the interface, so as 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: control each bidirectional DC / DC unit to work for a period of time one by one, and block the remaining bidirectional DC / DC units at the same time; wherein, the duty cycle of each bidirectional DC / DC unit remains consistent when working to ensure the accuracy of the identification process. When each bidirectional DC / DC unit is working, detect the voltage and current values ​​of the input port of each bidirectional DC / DC unit; taking the example of n bidirectional DC / DC units, the detected input port voltage value is: u bat1 、u bat2 、……、u batn , the input port current value is: i dc1 、i dc2 、……、i dcn . If the current values ​​corresponding to each input port are all zero, it can be determined that there is no energy storage module connected to the system. If there is only one input port with a non-zero current value, it can be determined that the system is in single-battery single-interface mode. If there are multiple input ports with non-zero current values, the system may be in single-battery multi-interface mode or multi-battery multi-interface mode. Next, we can continue to analyze the voltage values ​​of multiple input ports. If the voltage value of the input port with a non-zero current value remains consistent, it can be determined that the system is in single-battery multi-interface mode; if the voltage value of the input port with a non-zero current value does not remain consistent, it can be determined that the system is in multi-battery multi-interface mode.

[0051] In order to facilitate the understanding of the judgment of the single-battery multi-interface mode and the multi-battery multi-interface mode when the current values ​​corresponding to the multiple input ports are non-zero, the following will take two bidirectional DC / DC units, that is, the value of n is 2, as an example to analyze the specific judgment process in detail. Among them, the two bidirectional DC / DC units are marked as bidirectional DC / DC#1 and bidirectional DC / DC#2 respectively.

[0052] Specifically, Figure 9 As shown in the figure, it is a schematic diagram of the port voltage of the system in the dual battery electrical interface mode; the energy storage module corresponding to the bidirectional DC / DC#1 is defined as energy storage module#1, and the energy storage module corresponding to the bidirectional DC / DC#2 is defined as energy storage module#2. As can be seen from the figure, when the bidirectional DC / DC#1 is working and the bidirectional DC / DC#2 is not working, since the energy storage module#1 is in the discharge state, the circuit port voltage u bat1, that is, the working voltage of energy storage module #1 is in a downward state. While energy storage module #2 is in an open circuit state, so the circuit port voltage u bat2 remains basically unchanged. Subsequently, both bidirectional DC / DC units do not work, then the circuit port voltage u bat1 and u bat2 both remain basically unchanged. When bidirectional DC / DC #2 works while bidirectional DC / DC #1 does not work, energy storage module # is in an open circuit state, so the circuit port voltage u bat1 remains basically unchanged; while the discharge of energy storage module #2 causes the circuit port voltage u bat2 to be in a downward state, that is, in this connection mode, the circuit port voltages u bat1 and u bat2 have a large difference in change.

[0053] As Figure 10 shown, it is a schematic diagram of the port voltage when the system is in the single-battery dual-interface mode. The input port voltages u bat1 and u bat2 of the two bidirectional DC / DC units are actually the working voltages of the connected energy storage modules. Therefore, whether bidirectional DC / DC #1 works or bidirectional DC / DC #2 works, the energy storage modules are in a discharging state, that is, the circuit port voltages u bat1 and u bat2 both decrease and remain consistent.

[0054] In this embodiment, when the system identifies the input port, if it is found that it is connected in the multi-battery multi-interface mode and the voltage values of multiple input ports are at the same level within a certain period of time, this may cause the system to misjudge that the types of energy storage modules connected to multiple interfaces are the same; however, this situation may also exist 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 judge whether the energy storage modules connected to each input interface are of the same type. As Figure 11 shown, the specific identification process of the energy storage module type is as follows: Control multiple bidirectional DC / DC units to work with the same duty cycle at the same time, or control the energy storage modules corresponding to multiple input ports to charge and discharge under the same constant current condition. Detect the port voltages and currents of multiple bidirectional DC / DC units. If the change rates of the voltages and currents of multiple input ports are consistent, it can be judged that the types of energy storage modules connected to multiple input ports are the same; on the contrary, if the detection results show that there are obvious differences in the change rates of the voltages and currents of multiple input ports, it means that there are significant differences in the energy characteristics of the energy storage modules connected in multiple paths, and then it can be judged that different types of energy storage modules are connected to multiple input ports.

[0055] In this embodiment, as can be seen from the foregoing content, the system can form multiple working modes according to the access quantity and access mode of the energy storage module. Then, in order to ensure the stable switching operation of multiple working modes, it is necessary to design the control loop of the system. Among them, it is defined that when the current value on the energy storage module side is positive, the energy storage module is in the charging state, and when it is negative, it is in the discharging state; the maximum discharging current of the energy storage module is i discharge , and the maximum charging current is i charge . The control method of the system for the PV unit side is the same as the conventional one, that is, MPPT tracking or load limiting operation is performed. The specific control process is well-known technology to those skilled in the art, so it will not be elaborated in detail here.

[0056] As Figure 12 shown, the control loop for the energy storage module side includes a voltage outer loop, a maximum value module, a current sharing module, a limiting module, and multiple duty ratio generation modules. The voltage outer loop calculates the first current given value i dc by comparing the bus voltage V dc_ref with the bus voltage command value V batref1 through a PI controller. After weighting the obtained first current given value i batref1 with the weighting coefficient k1, it is used as one of the inputs of the maximum value module, and this input can be expressed as k1 + i batref1 . The other input of the maximum value module is the second current given value i batref2 issued by the ARM. The maximum value module takes the maximum value of the two inputs as the current given value i bat * on the battery side and outputs it to the current sharing module. The current sharing module can shunt the current given value i bat * according to the connection mode of the system through the shunt coefficient k2, and then obtain the current given values i bat1_1 * , i bat2_1 * , ……, i batn_1 * corresponding to n bidirectional DC / DC units, and send the shunted current given values to the limiting module. The limiting module can limit the shunted values and send them to multiple duty ratio generation modules respectively. Each duty ratio generation module can compare the input shunted value with the current sampling value i bat of the corresponding bidirectional DC / DC unit, and generate the duty ratios d1, d2, ……, d n of the corresponding bidirectional DC / DC units through a PI controller; thus, the effective control of the charging and discharging of the energy storage module is realized.

[0057] For the convenience of understanding, the following will take two-way bidirectional DC / DC units, namely bidirectional DC / DC #1 and bidirectional DC / DC #2 as examples to describe in detail the specific working processes of the current sharing module and the limiting module in the control loop. As Figure 12 shown, when the maximum value module outputs the current set value i bat * to the current sharing module, since the sum of the shunt coefficients corresponding to all bidirectional DC / DC units is 1, then the shunt coefficient corresponding to bidirectional DC / DC #1 at this time is k2, and the shunt coefficient corresponding to bidirectional DC / DC #2 can be expressed as 1 - k2. Through the current sharing module, the current set values i bat1_1 * and i bat2_1 * corresponding to bidirectional DC / DC #1 and bidirectional DC / DC #2 can be output respectively. The current set values i bat1_1 * and i bat2_1 * can generate new current set values i bat1 * and i bat2 * after passing through the corresponding limiting modules respectively. Then, the port current values i bat1 and i bat2 of the two-way bidirectional DC / DC units are sampled respectively, and the differences from the corresponding current set values i bat1 * and i bat2 * are used as the inputs of the PI controller, and then the duty cycles d1 of bidirectional DC / DC #1 and the duty cycle d2 of bidirectional DC / DC #1 are obtained.

[0058] It should be known that the voltage outer loop is a control loop that determines the current loop set value based on the bus voltage loop, and the energy storage module can control the bus voltage through the bidirectional DC / DC unit. The weight coefficient k1 is mainly used to weaken the role of the voltage outer loop when the system is in the grid-connected mode. The role of the limiting module is to prevent the energy storage module from being damaged by overcurrent; specifically, when the energy storage module discharges, it is necessary to limit the working current of the energy storage module not to exceed the given threshold I limit1 ; when the energy storage module charges, it is necessary to limit the working current of the energy storage module not to exceed the given threshold I limit2 ; thus ensuring that the working current of the energy storage module is always limited within the safe range that the energy storage module can withstand.

[0059] It can be understood that for the parameters k1, k2, I limit1 and I limit2 , they can be configured through the parameter configuration module. Specifically, as Figure 12As shown, when the system detects the connection mode of the input port, in combination with the maximum charge and discharge current of the energy storage module and the grid-connected and off-grid operating modes of the system, it can communicate with the ARM through the parameter configuration module, and then configure the parameters k1, k2, and I in the control loop limit1 and I limit2 to ensure that the energy storage module can charge and discharge safely and effectively under various connection modes. For the convenience of understanding, the following will describe the specific design process of the above parameters in detail.

[0060] Specifically, when the system is in the grid-connected mode, the value of the weight coefficient k1 given in the outer voltage loop is -∞, then the input k1 + i of the maximum value module batref1 can be regarded as approaching -∞; when the system is in the off-grid mode, the weight coefficient given in the outer voltage loop is 0, then the input k1 + i of the maximum value module batref1 is i batref1 . That is to say, when the system is in the grid-connected mode, the outer voltage loop will fail and not participate in the regulation of the control loop; when the system is in the off-grid mode, the outer voltage loop is put into operation, and then the energy storage module controls the bus voltage through the bidirectional DC / DC unit.

[0061] At the same time, the second current reference value i issued by the ARM batref2 is also related to the grid-connected and off-grid modes of the system; when the system is in the grid-connected mode, the ARM can calculate the second current reference value i according to the working power of the energy storage module and the bus voltage batref2 . In the off-grid mode, the ARM directly sets the second current reference value i batref2 to -∞, that is, the second current reference value i in this mode batref2 does not need to be calculated and generated by the ARM.

[0062] Based on the above, it can be seen that when the system is in the off-grid mode, the current reference value i output by the maximum value module bat * is determined by the outer voltage loop; when the system is in the grid-connected mode, the current reference value i output by the maximum value module bat * is determined by the value issued by the ARM.

[0063] The design of the parameters k2, I limit1 and I limit2 is related to the specific connection mode of the energy storage module. The following will describe the three connection modes in detail respectively.

[0064] (1) When the input port is in the single-battery single-interface mode, only one bidirectional DC / DC unit works. If it is found during the recognition process that the input current value i of a certain bidirectional DC / DC unitdci If it 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 shunt coefficient k2 corresponding to this bidirectional DC / DC unit in the current sharing module takes a value of 1, that is, the control loop only controls the duty cycle of this bidirectional DC / DC unit. For other bidirectional DC / DC units, they are in an inoperative state, and the corresponding shunt coefficient k2 takes a value of 0. Correspondingly, at this time, the threshold I in the amplitude limiting module limit1 can take the maximum charging current value i of the energy storage module charge of the energy storage module, and the threshold I limit2 can take the maximum discharge current i discharge of the energy storage module.

[0065] (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 the same as that of the single-battery single-interface. If the parallel working mode is adopted, then n (n>1) bidirectional DC / DC units need to work together. At this time, the n bidirectional DC / DC units need to draw power from the energy storage module at the same time and control the bus voltage. Therefore, the shunt coefficient k2 in the current sharing module takes a value of 1 / n. Since the n bidirectional DC / DC units are connected to the same energy storage module at this time, in the amplitude limiting module, the sum of the current limit values for each path is the maximum charge and discharge current value of the energy storage module; that is, the threshold I in the amplitude limiting module at this time limit1 can take 1 / n×i charge of the energy storage module, and the threshold I limit2 can take 1 / n×i discharge of the energy storage module.

[0066] (3) When the input port is in the multi-battery multi-interface mode, although the input end can be connected to energy storage modules of the same type, the specific charge and discharge conditions of the n (n>1) energy storage modules are not necessarily exactly the same. In addition, the input end may also be connected to energy storage modules of different types. Therefore, the shunt coefficient k2 in the current sharing module can be set according to the charge and discharge conditions of each energy storage module and the grid-connected and off-grid states of the system. It should be noted that in order to prevent a certain energy storage module from completing charging or discharging in advance, resulting in a decrease in system efficiency, it is necessary to make the n energy storage modules basically complete charging or discharging at the same time.

[0067] When the system is in the off-grid state, the current sharing module needs to work in coordination with the voltage outer loop. Therefore, droop control can be used in the voltage outer loop to calculate the voltage outer loop command value V dc_ref ; the specific calculation formula is: V dc_ref =V dc_nom -r i ×i bati . Among them, V dc_nom represents the initial set value of the bus voltage; r iIt represents the droop coefficient corresponding to the i-th energy storage module, where i = {1, 2, ……, n}, and the droop coefficient is r i It is used to achieve the balance of each energy storage module. The specific value is related to the SOC of each energy storage module; i bati It represents the operating current corresponding to the i-th energy storage module. At this time, the shunt coefficient k of the current sharing module 2_n The calculation formula is as follows: (1).

[0068] When the system is in the grid-connected state, the shunt coefficient k of the current sharing module corresponding to any two-way DC / DC unit 2_i The calculation formula is as follows: (2).

[0069] .

[0070] Among them, α represents the judgment value of the charge and discharge state of the energy storage module, and SOC i represents the remaining power value of the energy storage module connected to any two-way DC / DC unit, and V dc represents the collected bus voltage.

[0071] It should be noted that from the above formulas (1) and (2), when the bus voltage command value is greater than the bus voltage, the energy storage module is in the discharge 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 remaining power that the energy storage module can continue to discharge. When the bus voltage command 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 remaining power that the energy storage module can continue to charge.

[0072] The value of the limiting module depends on the maximum charge and discharge current value of the energy storage module connected to the system. If multiple energy storage modules are of the same type, the thresholds I of the limiting modules corresponding to multiple two-way DC / DC units limit1 are all set to i charge , and the threshold I limit2 are all set to i discharge . If the energy storage modules are of different types, the threshold I in the limiting module corresponding to any two-way DC / DC unit limit1 is set to the i of the connected energy storage module charge , and the threshold I limit2 is set to the i of the connected energy storage module discharge .

[0073] The basic principles, main features and advantages of the present application have been described above. Those skilled in the art should understand that the present application is not limited by the above embodiments, and what is described in the above embodiments and the specification is only the principle of the present application. Without departing from the spirit and scope of the present application, various changes and improvements will occur to the present application, and these changes and improvements all fall within the scope of the present application claimed. The scope of protection required by the present application is defined by the appended claims and their equivalents.

Claims

1. A multi-mode energy storage system with a multi-channel battery interface, characterized in that, include: Inverter architecture; Multi-channel bidirectional DC / DC unit; The multiple 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 connect to the energy storage module; a single energy storage module is suitable for connecting to at least one bidirectional DC / DC unit, thereby forming multiple connection modes; as well as Control loop; the control loop is suitable for outputting a duty cycle corresponding to 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.

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

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

4. The multi-mode energy storage system with a multi-channel battery interface according to claim 3, characterized in that, The selection of the standby working mode and the parallel working mode is suitable for adjustment according to the working data collection of the energy storage module, which specifically includes the following process: Collecting the SOC value and operating 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 a parallel working mode to charge the energy storage module; If the operating current of the energy storage module exceeds the rated current, the DC / DC unit selects a parallel working mode for current diversion; If a single channel of the DC / DC unit meets the working power requirement of the energy storage module, the DC / DC unit selects a standby working mode to work.

5. The multi-mode energy storage system with a multi-channel battery interface according to claim 2, characterized in that, The system determines the single-battery single-interface mode, single-battery multi-interface mode, and multi-battery multi-interface mode as follows: Controlling each bidirectional DC / DC unit to work in time-sharing mode one by one, and blocking the other bidirectional DC / DC units at the same time; When each bidirectional DC / DC unit is working, detecting the voltage value and current value of the input port of each bidirectional DC / DC unit; If the current values ​​corresponding to the input ports are all zero, it is determined that the system has no access to the energy storage module; If the current value corresponding to only one input port is non-zero, it is determined that the system is in single-battery single-port mode; If the current values ​​corresponding to multiple input ports are non-zero, and the voltage values ​​of the input ports with non-zero current values ​​are always consistent, it is determined that the system is in the single-battery multi-port mode; If there are multiple input ports with non - zero corresponding current values, and the voltage values of the input ports with non - zero current values do not remain consistent all the time, it is determined that the system is in the multi - battery multi - interface mode.

6. The multi-mode energy storage system with a multi-way battery interface according to claim 5, characterized in that, When the system is in the multi - battery multi - interface mode, if the voltage values of multiple input ports are at the same level, it is necessary to determine the types of the corresponding connected energy storage modules. The specific process is as follows: Simultaneously control multiple bidirectional DC / DC units to work 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 condition; Detect the port voltages and currents of multiple bidirectional DC / DC units. If the change rates of the voltages and currents of multiple input ports are consistent, it is determined that the types of the energy storage modules connected to multiple input ports are the same; Otherwise, it is determined that the types of the energy storage modules connected to multiple input ports are different.

7. The multi-mode energy storage system with a multi-channel battery interface according to any one of claims 2-6, characterized in that The control loop includes: A voltage outer loop; after comparing the collected bus voltage with the bus voltage command value through the voltage outer loop, the first current set value is calculated by a PI controller, and after assigning a weight coefficient to the obtained first current set value, it is used as one of the inputs of the maximum - value module; A maximum - value module; the other input of the maximum - value module is the second current set value sent by the ARM. The maximum - value module takes the maximum value of the two inputs as the current set value on the battery side and outputs it to the current - sharing module; A current - sharing module; the current - sharing module is adapted to shunt the current set value according to the connection mode of the system and send it to the limiting module; A limiting module; the limiting module is adapted to limit the shunted value and then send it to multiple duty - cycle generation modules respectively; and Multiple duty - cycle generation modules; each duty - cycle generation module is adapted to compare the input shunted value with the current sampling value of the corresponding bidirectional DC / DC unit, and generate the duty cycle of the corresponding bidirectional DC / DC unit after passing through a PI controller.

8. The multi-mode energy storage system with a multi-channel battery interface according to claim 7, characterized in that, When the system is in the grid - connected mode, the weight coefficient given in the voltage outer loop is -∞; meanwhile, the ARM calculates the second current set 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 given in the voltage outer loop is 0; meanwhile, the ARM directly sets the second current set value to -∞.

9. The multi-mode energy storage system with a multi-channel battery interface according to claim 7, characterized in that, When the system is in the multi - battery multi - interface mode and is off - grid, if the number of paths of the bidirectional DC / DC units with the energy storage modules connected is n; The bus voltage command value V of the voltage outer loop dc_ref is calculated by the formula: V dc_ref = V dc_nom - r i × i bati ; At this time, the shunt coefficient k of the current sharing module 2_n has the following calculation formula: ; Among them, V dc_nom represents the initial set value of the bus voltage, and r i represents the droop coefficient corresponding to the i-th energy storage module, where i = {1, 2, ……, n}, and i bati represents the operating current corresponding to the i-th energy storage module.

10. The multi-mode energy storage system with a multi-channel battery interface according to claim 7, characterized in that, When the system is in the multi - battery multi - interface mode and is grid - connected, if the number of paths of the bidirectional DC / DC units with the energy storage modules connected is n; At this time, the shunt coefficient k of the current sharing module corresponding to any path of the bidirectional DC / DC unit 2_i is calculated as follows: ； ； Among them, α represents the charge and discharge state judgment value of the energy storage module, and SOC i represents the remaining power value of the energy storage module connected to any path of the bidirectional DC / DC unit, and V dc represents the collected bus voltage.

Images