Charger baby type combined energy storage device

Abstract

The invention provides a power bank type combined energy storage device, and belongs to the technical field of energy storage. The battery pack comprises a plurality of battery packs, and each battery pack is connected in parallel with the low-voltage bus of the bidirectional DC-DC converter through a bidirectional Boost module; the bidirectional PCS converter is connected with the high-voltage bus of the bidirectional DC-DC converter, and is used for converting the voltage output by the high-voltage bus into three-phase commercial power to be output when the energy storage device is in an external discharging mode, and rectifying the single-phase or three-phase commercial power into the voltage required by the high-voltage bus when the energy storage device is in a charging mode; and the EMS module is used for determining the battery pack with the best state as a balanced power supply for output based on the SOC value of each battery pack. According to the invention, a full parallel topology is adopted among a plurality of battery packs, so that the problem that the whole string of battery packs cannot work normally due to a few battery packs with relatively serious performance degradation in the existing energy storage device can be solved.

Description

Technical Field

[0001] The present invention relates to the technical field of energy storage, and in particular to a power bank type combined energy storage device. Background Art

[0002] Microgrids based on energy storage devices are increasingly widely used in petroleum, geological exploration, field scientific research, and national defense activities. At present, the energy storage modules in energy storage devices are mostly integrated structures. The entire device relies on truck transportation, and it is impossible to reach the work site for power supply in some complex areas. Some energy storage devices collect energy from several energy storage modules (such as battery packs) in series and parallel combination. If necessary, a single module can be removed and carried to the site for power supply. However, the existing combined energy storage device has a complex structure, and the performance degradation of battery packs connected in series is inconsistent after long-term use. It is easy for a few battery packs with severe performance degradation to cause the entire string of battery packs to fail to work normally, resulting in a significant decrease in the output capacity of the energy storage device or even a complete inability to output. At the same time, it also wastes the power and load capacity of the healthy battery packs in the faulty battery string.

[0003] In summary, existing energy storage devices have the problem that the entire battery string cannot work properly due to a small number of battery packs with serious performance degradation. Summary of the invention

[0004] In view of this, it is necessary to provide a power bank type combined energy storage device to solve the technical problem that the existing energy storage device has a small number of battery packs with serious performance degradation, which causes the entire string of battery packs to fail to work normally.

[0005] In order to solve the above problems, on the one hand, the present invention provides a power bank type combined energy storage device, comprising: Bidirectional DC-DC converter; A battery pack, comprising a plurality of battery packs, each battery pack being connected in parallel with a low voltage bus of the bidirectional DC-DC converter via a bidirectional Boost module; A bidirectional PCS converter is connected to the high-voltage bus of the bidirectional DC-DC converter, and is used to convert the voltage output by the high-voltage bus into three-phase mains power for output when the energy storage device is in an external discharge mode, and to rectify the single-phase or three-phase mains power into the voltage required by the high-voltage bus when the energy storage device is in a charging mode; The EMS module is used to determine the battery pack with the best condition as a balanced power source for output based on the SOC value of each battery pack.

[0006] In a possible implementation, the EMS module is further used to adjust the charge and discharge parameters of the battery packs that are returned based on the number of battery packs that are returned and the corresponding SOC values ​​in a static state.

[0007] In a possible implementation, the bidirectional DC-DC converter includes: a plurality of parallel-connected dual-active full-bridge modules; The EMS module is also used to determine the number of dual-active full-bridge modules that need to be connected in the bidirectional DC-DC converter based on the SOC value of each battery pack, and control the corresponding dual-active full-bridge modules to be connected according to the number of dual-active full-bridge modules that need to be connected.

[0008] In a possible implementation, the number of the dual active full-bridge modules is 2 to 8; The EMS module is used to determine the number of dual-active full-bridge modules that need to be connected based on the output power of the energy storage device and the number of the dual-active full-bridge modules when the output power of the energy storage device does not exceed the rated output value.

[0009] In a possible implementation, the multiple dual active full-bridge modules connected are connected via a CAN bus communication; The EMS module is used to determine the target phase difference based on the ratio of 360° to the number of dual active full-bridge modules that need to be connected when the energy storage device is in a discharging state, and to perform staggered phase control on the connected multiple dual active full-bridge modules based on the target phase difference.

[0010] In a possible implementation, the EMS module is also used to control a dual-active full-bridge module as a main module to support the high-voltage bus voltage, and control other dual-active full-bridge modules to output in a constant current form.

[0011] In one possible implementation, the EMS module is also used to re-determine the main module from the remaining dual-active full-bridge modules when the current main module fails, and to reduce the output power of the energy storage device when the number of failed dual-active full-bridge modules exceeds a target number threshold.

[0012] In a possible implementation, the EMS module is also used to control the bidirectional Boost module corresponding to the target battery pack to switch to the Buck output mode of voltage and current dual-loop control when the energy storage device is in a charging state and the SOC value of the target battery pack is within a first preset range; and to control the bidirectional Boost module corresponding to the target battery pack to switch to the Buck output mode of single voltage loop control when the SOC value of the target battery pack is within a second preset range.

[0013] In one possible implementation, the EMS module is also used to perform clustering based on the SOC value and no-load voltage of each battery pack, determine the battery pack with the best condition based on the clustering results, and control the bidirectional Boost module corresponding to the battery pack with the best condition to enter the Boost mode and output according to the droop control.

[0014] In a possible implementation, the bidirectional PCS converter is a three-phase four-bridge-arm topology structure.

[0015] The beneficial effects of adopting the above-mentioned implementation method are: the power bank type combined energy storage device provided by the present invention includes: a bidirectional DC-DC converter; a battery pack, including multiple battery packs, each battery pack is connected in parallel with the low-voltage bus of the bidirectional DC-DC converter through a bidirectional Boost module; a bidirectional PCS converter, connected to the high-voltage bus of the bidirectional DC-DC converter, and is used to convert the voltage output by the high-voltage bus into three-phase AC power for output when the energy storage device is in an external discharge mode, and to rectify the single-phase or three-phase AC power into the voltage required by the high-voltage bus when the energy storage device is in a charging mode; an EMS module is used to determine the battery pack in the best state as a balanced power supply for output based on the SOC value of each battery pack.

[0016] Compared with existing energy storage devices, the power bank-type combined energy storage device provided by the present invention has multiple battery packs connected in parallel rather than in series, and adopts a full parallel topology to maximize the utilization of the battery packs. When the performance of some battery packs is seriously degraded, the EMS module can determine the battery pack in the best state as a balanced power source based on the SOC value of each battery pack for output, so as to avoid the inconsistent performance degradation of the battery packs after long-term use, and the situation that the entire string of battery packs cannot work properly due to a few battery packs with serious performance degradation, thereby solving the problem of a significant decrease in the output capacity of the energy storage device or even a complete inability to output. Therefore, the present invention can solve the technical problem that the existing energy storage device has a problem that the entire string of battery packs cannot work properly due to a few battery packs with serious performance degradation. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0018] Figure 1 A functional block diagram of an embodiment of a power bank type combined energy storage device provided by the present invention; Figure 2 Three views of the shelter provided by the present invention; Figure 3 The internal structure diagram of the shelter provided by the present invention; Figure 4 The electrical topology schematic diagram provided by the present invention. DETAILED DESCRIPTION

[0019] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0020] In the description of the embodiments of the present application, unless otherwise specified, “plurality” means two or more than two.

[0021] The terms "including" and "having" and any variations thereof in the embodiments of the present invention are intended to cover non-exclusive inclusions. For example, a process, method, apparatus, product or equipment comprising a series of steps or modules is not necessarily limited to those steps or modules clearly listed, but may include other steps or modules not clearly listed or inherent to these processes, methods, products or equipment.

[0022] The naming or numbering of the steps in the embodiments of the present invention does not mean that the steps in the method flow must be executed in the time / logical sequence indicated by the naming or numbering. The execution order of the named or numbered process steps can be changed according to the technical purpose to be achieved, as long as the same or similar technical effects can be achieved.

[0023] Reference to an "embodiment" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiment may be included in at least one embodiment of the present invention. The appearance of the phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0024] like Figure 1 As shown, the present invention provides a power bank type combined energy storage device, comprising: Bidirectional DC-DC converter; A battery pack, comprising a plurality of battery packs, each battery pack being connected in parallel with a low voltage bus of the bidirectional DC-DC converter via a bidirectional Boost module; A bidirectional PCS converter is connected to the high-voltage bus of the bidirectional DC-DC converter, and is used to convert the voltage output by the high-voltage bus into three-phase mains power for output when the energy storage device is in an external discharge mode, and to rectify the single-phase or three-phase mains power into the voltage required by the high-voltage bus when the energy storage device is in a charging mode; the bidirectional PCS converter is a three-phase four-bridge arm topology structure; The EMS module is used to determine the battery pack with the best condition as the balanced power supply for output based on the SOC (state of charge) value of each battery pack.

[0025] It is understandable that the entire energy storage device (referred to as the shelter) looks like Figure 2 As shown, it is installed in a standard JY1 type shelter. The shelter has doors only on the front, back and right sides, and no doors, holes or windows on the other sides to prevent rain and dust. The shelter adopts a double-layer structure, and multiple layers of 2mm thick fiberglass cloth are filled between the inner and outer layers for heat insulation and fire prevention. The upper right part of the front is the grid connection port of the intelligent distribution box, and the rest of the parts are tilted shutters. The upper right part of the rear is the output load interface of the intelligent distribution box, and the rest are 3 DC (direct current) speed-regulated DC fans with a diameter of 35cm, a speed regulation voltage of 12~36V, a speed variation range of 500RPM ~2000RPM, and a maximum air volume of not less than 400CFM. There are no openings on the bottom, left side, and upper side of the cabin body. There is an opening with a transparent waterproof polycarbonate cover on the right side, and the interior is the shelter control panel.

[0026] The interior layout of the entire shelter is as follows Figure 3 As shown in the figure, it consists of a battery pack, a bidirectional DC-DC converter, a bidirectional PCS converter (bidirectional energy storage inverter), an intelligent distribution box and an EMS module (energy management module). The battery pack is composed of several battery pack-bidirectional Boost module pairs in parallel. Specifically, each battery pack is connected in parallel at the low-voltage bus of the bidirectional DC-DC converter through a bidirectional Boost module. The bidirectional DC-DC converter is composed of m (2≤m≤8) dual-active full-bridge modules in parallel, and each module outputs ykW (4≤y≤10). The bidirectional PCS converter is a single three-phase four-bridge arm topology that can withstand three-phase unbalanced loads. The intelligent distribution box controls the access of loads and other cabins according to the management strategy. On the one hand, the EMS module monitors the SOC and fault status of the battery pack and manages the charging and discharging process. On the other hand, it manages the energy of the entire cabin through the intelligent distribution box.

[0027] When the cabin is in external discharge mode, the bidirectional Boost module boosts the voltage of each battery pack and stabilizes it at the low-voltage bus voltage UDCL, which is then boosted to the high-voltage bus voltage UDCH by the bidirectional DC-DC converter and finally converted into three-phase AC power for external output by the bidirectional PCS converter.

[0028] When the cabin is in charging mode, the bidirectional PCS converter rectifies the single-phase or three-phase mains power into a high-voltage bus voltage UDCH, and controls the output DC voltage and current in a constant voltage source mode. Then the bidirectional DC-DC converter steps down the voltage and controls the output DC voltage and current in a constant voltage source mode. The EMS controls the bidirectional Boost module to manage the charging of each battery pack in a "constant current-constant voltage-trickle current" mode according to the SOC of each battery cluster.

[0029] When the cabin is in balancing mode, that is, in a static state, if a pulled-out battery pack is put back, the EMS controls the charging and discharging parameters according to the number of battery packs put back and the SOC status of the battery packs.

[0030] When the cabin is connected to the grid with other forms of new energy, the output of the bidirectional PCS converter is controlled in droop mode.

[0031] The hardware core of the present invention is a combination of hardware topology principles. Figure 4 In the figure, CELL1 represents Figure 3 The battery pack 1 in the figure; capacitors C1-1, C1-2, inductor L1-1, MOS tubes MOS1-1, MOS1-2, these devices constitute a complete Boost topology, representing Figure 3 The bidirectional boost module 1 in . And so on. Figure 4 The switch tubes S1-1 to S1-8, the inductor LS-1, and the ideal transformer T1 (both of which are equivalent to the actual transformer) represent a dual-active full-bridge module. Similarly, a total of m dual-active full-bridge modules are connected in parallel to form a bidirectional DC-DC converter. The switch tubes SP1 to SP8 and the bus capacitor CS1 form the three-phase four-bridge main topology of the bidirectional PCS converter. The capacitors SG1 to SG4 are ground filter capacitors, and the inductors SL1 to SL4 and capacitors SC1 to SC4 form the output LC filter circuit.

[0032] The present invention has the following beneficial effects: The present invention solves the problem of hot-plugging of battery packs under normal use, so that a number of battery packs can be arbitrarily extracted and carried for separate use when the energy storage device is normally charged or discharged, thereby expanding the use scenarios of the energy storage device and improving the utilization rate and practicality of the remaining battery packs in the energy storage device.

[0033] In some embodiments, the EMS module is further used to adjust the charge and discharge parameters of the battery packs that are returned based on the number of battery packs that are returned and the corresponding SOC values ​​in a static state.

[0034] In some embodiments, the bidirectional DC-DC converter includes: a plurality of parallel dual active full-bridge modules; The EMS module is also used to determine the number of dual-active full-bridge modules that need to be connected in the bidirectional DC-DC converter based on the SOC value of each battery pack, and control the corresponding dual-active full-bridge modules to be connected according to the number of dual-active full-bridge modules that need to be connected.

[0035] In some embodiments, the number of the dual active full-bridge modules is 2 to 8; The EMS module is used to determine the number of dual-active full-bridge modules that need to be connected based on the output power of the energy storage device and the number of the dual-active full-bridge modules when the output power of the energy storage device does not exceed the rated output value.

[0036] In some embodiments, the multiple dual active full-bridge modules connected are connected via a CAN bus communication; The EMS module is used to determine the target phase difference based on the ratio of 360° to the number of dual active full-bridge modules that need to be connected when the energy storage device is in a discharging state, and to perform staggered phase control on the connected multiple dual active full-bridge modules based on the target phase difference.

[0037] In some embodiments, the EMS module is also used to control a dual active full-bridge module as a main module to support the high-voltage bus voltage, and control other dual active full-bridge modules to output in a constant current form.

[0038] In some embodiments, the EMS module is also used to re-determine the main module from the remaining dual-active full-bridge modules when the current main module fails, and to reduce the output power of the energy storage device when the number of failed dual-active full-bridge modules exceeds a target number threshold.

[0039] In some embodiments, the EMS module is also used to control the bidirectional Boost module corresponding to the target battery pack to switch to the Buck output mode of dual-loop control of voltage and current when the energy storage device is in a charging state and the SOC value of the target battery pack is within a first preset range; and to control the bidirectional Boost module corresponding to the target battery pack to switch to the Buck output mode of single voltage loop control when the SOC value of the target battery pack is within a second preset range.

[0040] In some embodiments, the EMS module is also used to perform clustering based on the SOC value and no-load voltage of each battery pack, determine the battery pack with the best condition based on the clustering result, and control the bidirectional Boost module corresponding to the battery pack with the best condition to enter the Boost mode and output according to the droop control.

[0041] It can be understood that in some embodiments, the core of the software of the present invention is the control strategy of electrical topology and battery charging and discharging in different working modes. Figure 4Please explain.

[0042] When the shelter is in the discharge state: First, it is defined that the battery pack is only allowed to discharge when the SOC is above 20%.

[0043] When the battery pack SOC allows external discharge and is in the discharge state, the bidirectional Boost module is in Boost mode, and the output is controlled in the traditional droop mode. If the SOC of the entire cabin is between 20% and 60%, or more than 30% of the battery packs in the entire cabin have an SOC below 20% (including being extracted), the external output power of the entire cabin is controlled to be reduced to 50% of the rated value.

[0044] At this time, the bidirectional DC-DC converter is in the boost state, and power flows from the low-voltage bus to the high-voltage bus. If there are m (2≤m≤8) dual-active full-bridge modules in the bidirectional DC-DC converter, the EMS controls the number of modules connected according to the cabin output power. If the output power is P and does not exceed the rated output value, then connect The multiple dual active full bridge modules connected communicate with each other through the CAN bus (controller area network bus). Perform staggered phase control to avoid the superposition of switching noise caused by the same phase control of multiple modules. The master-slave control mode is adopted between the modules. The first connected module is the master module, which is responsible for supporting the high-voltage bus voltage. The output side of the subsequent connected modules is controlled in the form of constant current. Once the main module exits due to a fault, the EMS instructs the second connected module to take over as the main module and reduce the output power of the cabin by ykW. For the state of connecting n (n≥3) modules, if 1 ~ n / 3 modules exit, the output power of the cabin will be reduced to 50% of the rated value; if n / 2 or more modules exit, the output power of the cabin will be reduced to 25% of the rated value, and the fault alarm information will be displayed on the screen.

[0045] The bidirectional PCS converter is based on conventional dual-loop SVPWM control. When the fuel cell system and photovoltaic power generation system are connected to the shelter, the bidirectional PCS converter is in V / f control mode by default, that is, it provides voltage and frequency support for the microgrid, and the connected fuel cell system and photovoltaic power generation system perform P / Q control to provide the active and reactive power required by the microgrid. When the energy storage shelter is connected to the mains, the bidirectional PCS converter is in the inverter state by default and automatically tracks the voltage and frequency of the external power grid.

[0046] When the cabin is in charging state: When in the charging state, the bidirectional boost module is in the buck output mode, and the MCU in the module adjusts the control mode of the bidirectional boost module according to the SOC state of the connected battery pack. When the battery pack SOC is below 10%, the buck output mode of the bidirectional boost module is controlled by the voltage-current loop, and the output voltage follows the battery pack voltage; the output current value is 0.1CB, and CB is the rated capacity of the battery pack. If the charging process exceeds 45 minutes and still cannot increase the battery pack SOC to 10%, it is determined that the battery pack is faulty or the battery cell performance is seriously degraded, and the battery pack is removed and an alarm message is displayed on the screen. When the battery pack SOC is between 10% and 85%, the buck output mode of the bidirectional boost module is controlled by the voltage-current loop, and the output voltage follows the battery pack voltage; the maximum output current value is 1CB (CB is the rated capacity of the battery pack). If the charging power of the entire cabin is not enough to support 1CB constant current charging of all battery packs with SOC between 10% and 85%, the charging current of these battery packs is reduced until it is lower than the charging power that the entire cabin can provide. At the same time, if the output voltage of the battery pack is higher than 0.98UB during charging, UB is the voltage when the battery pack is fully charged, the battery pack is considered to be faulty or the performance of the battery cell is seriously degraded, the battery pack is removed and an alarm message is displayed on the screen. When the battery pack SOC is between 85% and 95%, the output mode of the bidirectional Boost module Buck is controlled by a single voltage loop, and the output voltage is controlled at UB±0.02V. When the battery pack SOC is above 95%, the output mode of the bidirectional Boost module Buck is controlled by a voltage-current loop, and the output voltage is constant at UB V. When the output current is lower than 0.05CB, the battery pack is considered to be fully charged and removed, and CB is the rated capacity of the battery pack. When k / 3 (k is the total number of battery packs in the cabin) battery packs in the entire cabin are identified as faulty or seriously degraded, the output power of the cabin is controlled to be reduced to 50% of the rated value, and the information that the battery pack needs to be replaced is displayed on the screen.

[0047] At this time, the bidirectional DC-DC converter is in a step-down state, and power flows from the high-voltage bus to the low-voltage bus. If there are m (2≤m≤8) dual-active full-bridge modules in the bidirectional DC-DC converter, the EMS controls the number of modules connected according to the cabin output power. If the output power is P and does not exceed the rated output value, then connect The multiple dual active full bridge modules connected communicate with each other through the CAN bus. Perform staggered phase control to avoid the superposition of switching noise caused by the same phase control of multiple modules. The master-slave control mode is adopted between the modules. The first connected module is the master module, which is responsible for supporting the low-voltage bus voltage. The output side of the subsequent connected modules is controlled in a constant current form. Once the main module exits due to a fault, the EMS instructs the second connected module to take over as the main module and reduce the charging power of the cabin by ykW. For the state of connecting n (n≥3) modules, if 1 ~ n / 3 modules exit, the charging power of the cabin will be reduced to 60% of the rated value; if n / 2 or more modules exit, the charging power of the cabin will be reduced to 30% of the rated value, and the fault alarm information will be displayed on the screen.

[0048] The bidirectional PCS converter is based on conventional dual-loop SVPWM control. When the fuel cell system and the photovoltaic power generation system are connected to the shelter, the EMS will instruct the bidirectional PCS converter to enter the rectification mode with APFC function through screen control, the photovoltaic power generation system works in V / f mode, and the fuel cell system works in P / Q mode, and they jointly supply power to the energy storage shelter. At this time, the bidirectional PCS converter is in voltage-current loop control, and the EMS controls the charging power of the energy storage shelter according to the output capacity reported by the fuel cell system and the photovoltaic power generation system. When the energy storage shelter is connected to the mains, if the SOC of the shelter battery is lower than 10%, it may even cause the bidirectional DC-DC converter to fail to start, and the bidirectional PCS converter is in the no-load inverter state by default. Then, through screen control, the EMS instructs the bidirectional PCS converter to switch to the no-load rectification mode, and the PCS starts the bidirectional DC-DC converter after charging the high-voltage bus. At this time, both converters are controlled by a single voltage loop, and the output characteristics are constant voltage sources.

[0049] When the cabin is in balancing mode, both the bidirectional DC-DC converter and the bidirectional PCS converter are not working. EMS automatically detects the battery packs that need to be balanced. The algorithm is briefly described as follows. With the SOC of each battery pack as the horizontal axis and the no-load voltage of the battery pack as the vertical axis, the battery packs are divided into three clusters A, B, and C using the K-Means clustering method. Cluster A is a battery pack with low SOC and voltage, such as a battery pack that is plugged back into the charging after use; Cluster B is a battery pack with high SOC and low voltage, which is generally a battery pack with performance degradation but not serious enough to require removal. This is the main object of balancing; Cluster C is a battery pack with high SOC and voltage, which is a healthy battery pack that works normally. For cluster C, find the centroid of the cluster, calculate the distance from each point to its nearest centroid, and calculate the relative distance from each point to its nearest centroid, that is, the ratio of the distance from the point to the centroid to the median of the distance from all points in the cluster to the centroid. Compare the calculation result with the given threshold. If it is less than the given threshold, it is included in the category of cluster D. The purpose of defining the D-cluster battery pack is to select the best battery pack as a balanced power source. Then the EMS controls the bidirectional Boost module corresponding to the D-cluster battery pack to enter the Boost mode, and after the low-voltage bus voltage is stabilized by the droop control output, the bidirectional Boost module corresponding to the B-cluster battery pack is controlled to enter the Buck mode. Based on the voltage-current loop control, the B-cluster battery pack is balanced charged at 0.05CB ~ 0.5CB until its no-load voltage exceeds the minimum value in the C-cluster.

[0050] In some embodiments, a certain type of combined energy storage device (referred to as a shelter) is as follows Figure 1 , Figure 2 and Figure 3 As shown. The cabin adopts the standard JY1 cabin size, with only doors on the front, back and right side, and no doors, holes or windows on the other sides to prevent rain and dust. The cabin adopts a double-layer structure, with multiple layers of 2mm thick fiberglass cloth filled between the inner and outer layers for heat insulation and fire prevention. The upper right part of the front is the grid connection port of the intelligent distribution box, and the rest are tilted shutters. The upper right part of the rear is the output load interface of the intelligent distribution box, and the rest are 3 DC speed-regulated DC fans with a diameter of 35cm, a speed regulation voltage of 12~36V, a speed range of 500RPM~2000RPM, and a maximum air volume of 450CFM. There are no openings on the bottom, left and upper sides of the cabin body, and there is an opening with a transparent waterproof polycarbonate cover on the right side. Inside is the cabin control panel, which uses a 10-inch capacitive operation screen (resolution 1920×1200, maximum 600nit brightness, based on INTEL J1900 processor and Windows 7 operating system, CAN bus communication).

[0051] The rated output power of this cabin is 15kVA for three phases, and the rated output power of each phase is 5kVA. The cabin can be connected to one fuel cell system (three phase) with a maximum output power of 12kVA and one photovoltaic power generation system (single phase), and has one 1~3 level three-phase five-wire output interface each. The battery pack used is composed of two square ternary lithium batteries connected in series. The battery pack has a charging cut-off voltage of 8.4V, a discharging cut-off voltage of 6V, and a rated capacity of 48Ah. Figure 3 As shown, there are 3 columns on the front, with 5 battery packs in each column; the same is true for the back, with a total of 30 battery packs in the entire cabin. Each battery pack is equipped with a bidirectional Boost module, a boost ratio range of 3 ~ 4.5, and a low-voltage bus rated voltage of 24V. The bidirectional DC-DC converter consists of 6 modules in parallel, and each module has an output power of 3kW. The input operating voltage range is 48V~134.4V, the output operating voltage is 360V, and a bidirectional full-bridge LLC topology is adopted to reduce losses and suppress common-mode voltage. The bidirectional PCS converter consists of 3 single-phase full-bridge inverters, each inverter has a rated output of 6kVA, and a power factor of 0.7~1 (lagging); when in the charging state, the output power of the DC bus side of the bidirectional PCS converter is not more than 6kW.

[0052] In some application scenarios, the output power of the energy storage device in the present invention may not be enough. One set of three-phase 12kVA fuel cell power generation system and one set of single-phase 6kVA photovoltaic power generation system can be connected externally to form a combined system with a maximum output power of 31kVA to carry external loads.

[0053] When the shelter is in the discharge state: When the battery pack SOC allows external discharge and is in the discharge state, the bidirectional Boost module is in Boost mode, and the output is controlled in the traditional droop mode. If the SOC of the entire cabin is between 20% and 60%, or more than 30% of the battery packs in the entire cabin have an SOC below 20% (including being extracted), the external output power of the entire cabin is controlled to be reduced to 50% of the rated value.

[0054] At this time, the bidirectional DC-DC converter is in the boost state, and power flows from the low-voltage bus to the high-voltage bus. There are 6 dual-active full-bridge modules in the bidirectional DC-DC converter. The EMS controls the number of modules connected according to the output power of the cabin. If the output power is P and does not exceed the rated output value, then the module is connected. The multiple dual-active full-bridge modules connected communicate with each other through the CAN bus, and are staggered at 60° to avoid the superposition of switching noise caused by the same-phase control of multiple modules. The master-slave control mode is adopted between the modules. The first connected module is the master module, which is responsible for supporting the high-voltage bus voltage. The output side of the subsequent modules is controlled in a constant current form. Once the main module exits due to a fault, the EMS instructs the second connected module to take over as the main module and reduce the output power of the cabin by 3kW. If 1 to 2 modules exit, the output power of the cabin will be reduced by 7.5kW; if at least 3 modules exit, the output power of the cabin will be reduced to 3.75kW, and the fault alarm information will be displayed on the screen.

[0055] The bidirectional PCS converter is based on conventional dual-loop SVPWM control. When the fuel cell system and photovoltaic power generation system are connected to the shelter, the bidirectional PCS converter is in V / f control mode by default, that is, it provides voltage and frequency support for the microgrid, and the connected fuel cell system and photovoltaic power generation system perform P / Q control to provide the active and reactive power required by the microgrid. When the energy storage shelter is connected to the mains, the bidirectional PCS converter is in the inverter state by default and automatically tracks the voltage and frequency of the external power grid.

[0056] When the cabin is in charging state: When in the charging state, the bidirectional boost module is in the buck output mode, and the MCU in the module adjusts the control mode of the bidirectional boost module according to the SOC state of the connected battery pack. When the battery pack SOC is below 10%, the buck output mode of the bidirectional boost module is controlled by the voltage-current loop, and the output voltage follows the battery pack voltage; the output current value is 0.1CB (4.8A). If the charging process exceeds 45 minutes and still cannot increase the battery pack SOC to 10%, it is considered that the battery pack is faulty or the battery cell performance is seriously degraded, and the battery pack is removed and an alarm message is displayed on the screen. When the battery pack SOC is between 10% and 85%, the buck output mode of the bidirectional boost module is controlled by the voltage-current loop, and the output voltage follows the battery pack voltage; the maximum output current value is 1CB (48A). If the charging power of the entire cabin is not enough to support 1CB (48A) constant current charging of all battery packs with SOC between 10% and 85%, the charging current of these battery packs is reduced until it is lower than the charging power that the entire cabin can provide. At the same time, if the output voltage of the battery pack is higher than 0.98UB (8.23V) during charging, the battery pack is considered to be faulty or the performance of the battery cell is seriously degraded, the battery pack is removed and an alarm message is displayed on the screen. When the battery pack SOC is between 85% and 95%, the output mode of the bidirectional Boost module Buck is controlled by a single voltage loop, and the output voltage is controlled at 8.36±0.02V. When the battery pack SOC is above 95%, the output mode of the bidirectional Boost module Buck is controlled by a voltage-current loop, the output voltage is constant at 8.4V, and the battery pack is considered to be full and removed after the output current is lower than 0.05CB (2.4A). When 10 battery packs in the entire cabin are identified as faulty or seriously degraded, the output power of the control cabin is reduced to 7.5kW, and the information that the battery pack needs to be replaced is displayed on the screen.

[0057] At this time, the bidirectional DC-DC converter is in a step-down state, and power flows from the high-voltage bus to the low-voltage bus. There are 6 dual-active full-bridge modules in the bidirectional DC-DC converter. The EMS controls the number of modules connected according to the output power of the cabin. If the output power is P and does not exceed the rated output value, then the module is connected. The multiple dual-active full-bridge modules connected communicate with each other through the CAN bus, and are staggered at 60° to avoid the superposition of switching noise caused by the same phase control of multiple modules. The master-slave control mode is adopted between the modules. The first connected module is the master module, which is responsible for supporting the low-voltage bus voltage. The output side of the subsequent modules is controlled in a constant current form. Once the main module exits due to a fault, the EMS instructs the second connected module to take over as the main module and reduce the charging power of the cabin by 3kW. If 1 to 2 modules exit, the charging power of the cabin will be reduced to 3.6kW (rated charging power 6kW); if 3 or more modules exit, the charging power of the cabin will be reduced to 1.8kW (rated charging power 6kW), and the fault alarm information will be displayed on the screen.

[0058] The bidirectional PCS converter is based on conventional dual-loop SVPWM control. When the fuel cell system and the photovoltaic power generation system are connected to the shelter, the EMS will instruct the bidirectional PCS converter to enter the rectification mode with APFC function through screen control, the photovoltaic power generation system works in V / f mode, and the fuel cell system works in P / Q mode, and they jointly supply power to the energy storage shelter. At this time, the bidirectional PCS converter is in voltage-current loop control, and the EMS controls the charging power of the energy storage shelter according to the output capacity reported by the fuel cell system and the photovoltaic power generation system. When the energy storage shelter is connected to the mains, if the SOC of the shelter battery is lower than 10%, it may even cause the bidirectional DC-DC converter to fail to start, and the bidirectional PCS converter is in the no-load inverter state by default. Then, through screen control, the EMS instructs the bidirectional PCS converter to switch to the no-load rectification mode, and the PCS starts the bidirectional DC-DC converter after charging the high-voltage bus. At this time, both converters are controlled by a single voltage loop, and the output characteristics are constant voltage sources.

[0059] When the cabin is in balancing mode, both the bidirectional DC-DC converter and the bidirectional PCS converter are not working. EMS automatically detects the battery packs that need to be balanced. The algorithm is briefly described as follows. With the SOC of each battery pack as the horizontal axis and the no-load voltage of the battery pack as the vertical axis, the battery packs are divided into three clusters A, B, and C using the K-Means clustering method. Cluster A is a battery pack with low SOC and voltage, such as a battery pack that is plugged back into the charging after use; Cluster B is a battery pack with high SOC and low voltage, which is generally a battery pack with performance degradation but not serious enough to require removal. This is the main object of balancing; Cluster C is a battery pack with high SOC and voltage, which is a healthy battery pack that works normally. For cluster C, find the centroid of the cluster, calculate the distance from each point to its nearest centroid, and calculate the relative distance from each point to its nearest centroid, that is, the ratio of the distance from the point to the centroid to the median of the distance from all points in the cluster to the centroid. Compare the calculation result with the given threshold. If it is less than the given threshold, it is included in the category of cluster D. The purpose of defining the D-cluster battery pack is to select the best battery pack for use as a balanced power source. Then the EMS controls the bidirectional Boost module corresponding to the D-cluster battery pack to enter the Boost mode, and after the low-voltage bus voltage is stabilized by the droop control output, the bidirectional Boost module corresponding to the B-cluster battery pack is controlled to enter the Buck mode. Based on the voltage-current loop control, the B-cluster battery pack is balanced charged at 0.05CB ~ 0.5CB (2.4A ~ 24A) until its no-load voltage exceeds the minimum value in the C-cluster.

[0060] The power bank type combined energy storage device provided by the present invention is introduced in detail above. Specific examples are used in this article to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea; at the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation method and application scope. In summary, the content of this specification should not be understood as a limitation on the present invention.

Claims

1. A power bank type combined energy storage device, characterized in that: include: Bidirectional DC-DC converter; A battery pack, comprising a plurality of battery packs, each battery pack being connected in parallel with a low voltage bus of the bidirectional DC-DC converter via a bidirectional Boost module; A bidirectional PCS converter is connected to the high-voltage bus of the bidirectional DC-DC converter, and is used to convert the voltage output by the high-voltage bus into three-phase mains power for output when the energy storage device is in an external discharge mode, and to rectify the single-phase or three-phase mains power into the voltage required by the high-voltage bus when the energy storage device is in a charging mode; The EMS module is used to determine the battery pack with the best condition as a balanced power source for output based on the SOC value of each battery pack.

2. The power bank type combined energy storage device according to claim 1, characterized in that: The EMS module is also used to adjust the charging and discharging parameters of the battery packs that are returned based on the number of battery packs that are returned and the corresponding SOC values ​​in a static state.

3. The power bank type combined energy storage device according to claim 1, characterized in that: The bidirectional DC-DC converter comprises: a plurality of parallel-connected dual active full-bridge modules; The EMS module is also used to determine the number of dual-active full-bridge modules that need to be connected in the bidirectional DC-DC converter based on the SOC value of each battery pack, and control the corresponding dual-active full-bridge modules to be connected according to the number of dual-active full-bridge modules that need to be connected.

4. The power bank type combined energy storage device according to claim 3, characterized in that: The number of the dual active full-bridge modules is 2 to 8; The EMS module is used to determine the number of dual-active full-bridge modules that need to be connected based on the output power of the energy storage device and the number of the dual-active full-bridge modules when the output power of the energy storage device does not exceed the rated output value.

5. The power bank type combined energy storage device according to claim 4, characterized in that: The multiple dual active full-bridge modules connected are connected via CAN bus communication; The EMS module is used to determine the target phase difference based on the ratio of 360° to the number of dual active full-bridge modules that need to be connected when the energy storage device is in a discharging state, and to perform staggered phase control on the connected multiple dual active full-bridge modules based on the target phase difference.

6. The power bank type combined energy storage device according to claim 1, characterized in that: The EMS module is also used to control a dual active full bridge module as a main module to support the high voltage bus voltage, and control other dual active full bridge modules to output in a constant current form.

7. The power bank type combined energy storage device according to claim 6, characterized in that: The EMS module is also used to re-determine the main module from the remaining dual-active full-bridge modules when the current main module fails, and to reduce the output power of the energy storage device when the number of failed dual-active full-bridge modules exceeds a target number threshold.

8. The power bank type combined energy storage device according to claim 1, characterized in that: The EMS module is also used to control the bidirectional Boost module corresponding to the target battery pack to switch to the Buck output mode of voltage and current dual-loop control when the energy storage device is in a charging state and the SOC value of the target battery pack is within a first preset range; and to control the bidirectional Boost module corresponding to the target battery pack to switch to the Buck output mode of single voltage loop control when the SOC value of the target battery pack is within a second preset range.

9. The power bank type combined energy storage device according to claim 1, characterized in that: The EMS module is also used to cluster based on the SOC value and no-load voltage of each battery pack, determine the battery pack in the best condition based on the clustering result, and control the bidirectional Boost module corresponding to the battery pack in the best condition to enter the Boost mode and output according to the droop control.

10. The power bank type combined energy storage device according to any one of claims 1 to 9, characterized in that: The bidirectional PCS converter has a three-phase four-bridge-arm topology.

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