Energy storage device, control method thereof, and photovoltaic system
By designing multiple series modules and using low-current pre-charging technology in the energy storage device, the problem of damage caused by excessive voltage stress on power electronic devices under high current conditions is solved, effectively protecting the switching devices and improving the safety of the energy storage device.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- HUAWEI DIGITAL POWER TECH CO LTD
- Filing Date
- 2022-05-19
- Publication Date
- 2026-07-10
AI Technical Summary
When power electronic devices such as MOSFETs and IGBTs are switched off under high current conditions, they are easily subjected to large voltage stress, which can lead to device damage and affect battery performance.
Design an energy storage device comprising multiple energy storage modules connected in series. Each module includes a power supply module, an absorption module, first and second switching devices, and a control module. The control module controls the coupling mode of the switching devices and performs a small current pre-charge before the switching devices are turned on. The absorption module absorbs peak voltages to protect the switching devices.
It effectively protects switching devices, prevents breakdown damage, and improves the safety of energy storage devices.
Smart Images
Figure CN114938046B_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of electronic power technology, specifically to an energy storage device and its control method, as well as a photovoltaic system. Background Technology
[0002] Power electronic devices, such as metal-oxide-semiconductor field-effect transistors (MOSFETs) and insulated-gate bipolar transistors (IGBTs), are widely used in power conversion applications, such as frequency converters, ballasts, power adapters, wind and solar power, switch control, battery connection and bypass, and static var generator (SVG) module bypass control.
[0003] Power electronic devices offer fast turn-on speeds, low switching losses, and high energy density, but their withstand voltage and overcurrent capabilities are relatively low. When these devices are used as switching protection devices in batteries, the high-current tripping operation typically involves significant voltage stress. If the voltage stress exceeds the device's specifications, it can damage the device and affect battery performance. Summary of the Invention
[0004] This application provides an energy storage device and its control method, as well as a photovoltaic system, which can improve the safety of the energy storage device.
[0005] In a first aspect, this application provides an energy storage device comprising multiple energy storage modules connected in series. Each energy storage module includes a power supply module, an absorption module, a first switching device, a second switching device, and a control module. Specifically: in each energy storage module, the power supply module and the first switching device are connected in series between the positive and negative terminals of the energy storage module, and the power supply module and the second switching device are connected in parallel between the positive and negative terminals of the energy storage module; the control module controls the first switching device of any one of the multiple energy storage modules to close and the second switching device to open, so that any one energy storage module is coupled in series with other energy storage modules, wherein the other energy storage modules are all energy storage modules other than any one of the multiple energy storage modules; the control module also controls the first switching device of any one energy storage module to open and the second switching device to close, so as to bypass any one energy storage module; the absorption module is used to charge the first or second switching device before its switching transistor is turned on, and to absorb the spike voltage generated when the first or second switching device is turned off after the first or second switching device is turned on.
[0006] In the solution provided in this application, the energy storage device may include multiple energy storage modules coupled in series. Coupling can refer to a conductive connection, including direct connection or connection through switching devices and / or resistors and other conducting devices. The multiple energy storage modules can store or release energy, such as charging and discharging. When the multiple energy storage modules are in a charging or discharging state, the control module can control the coupling method between any one energy storage module and other energy storage modules based on the state of charge or voltage of the power module in any one energy storage module. For example, when the multiple energy storage modules are in a charging state, if the control module determines that the power module is fully charged or damaged, it can control the first switching device of any one of the energy storage modules to open and the second switching device to close, thereby bypassing that energy storage module, i.e., disconnecting it from the multiple energy storage modules; if the control module determines that the power module is in a normal charging state, it can control the first switching device of any one of the energy storage modules to close and the second switching device to open, thereby coupling that energy storage module in series with other energy storage modules, i.e., disconnecting it from the multiple energy storage modules. When the first or second switching device changes from closed to open, a large potential is generated due to the parasitic inductance in the power module, leading to increased voltage stress when the first or second switching device is disconnected, which may damage it. Secondly, since the power module contains electrical energy, a large inrush current and arcing may occur at the moment of connection when the absorption module is installed on the power module bus. In this application, a small current pre-charge is performed before the first or second switching device is turned on, which solves the problem of large inrush current and arcing at the moment of connection when the absorption module is installed on the power module bus. After the first or second switching device is turned on, the absorption module can absorb the voltage spike when the first or second switching device is disconnected, clamping the voltage stress of the first and second switching devices within a safe range, thereby protecting the switching devices from breakdown damage and improving the safety of the energy storage device.
[0007] In one possible implementation, each absorption module includes a first capacitor and a second capacitor coupled to both ends of the power module, wherein the first capacitor is used to regulate the output voltage of the power module, and the second capacitor is used to charge the power module before the first or second switching device is turned on.
[0008] In the solution provided in this application, each absorption module may include a first capacitor and a second capacitor. The first capacitor can regulate the output voltage of the power module, and the second capacitor can be pre-charged before the first or second switching device is turned on. Pre-charging before the first or second switching device operates can play a role in slow start-up, thereby solving the problem of large inrush current and arcing at the moment of connection when the absorption module is installed on the power module bus.
[0009] In one possible implementation, each absorption module includes a third switching device, a fourth switching device, and a resistor, wherein the fourth switching device is connected in series with the resistor; a control module is used to control the fourth switching device to turn on before the third switching device turns on, so as to precharge the first capacitor individually or simultaneously with the first capacitor and the second capacitor under the current limiting of the resistor.
[0010] In the solution provided in this application, the absorption module includes a third switching device, a fourth switching device coupled in series, and a resistor. Before the first or second switching device is turned on, the control module first turns on the fourth switching device for small-current pre-charging. Specifically, when the absorption module includes a first capacitor and a second capacitor, since the first and second capacitors are coupled across the two ends of the power module, there will be a large inrush current and arcing problem at the moment of connection when the absorption module is installed on the power module bus. Therefore, turning on the fourth switching device allows the current to be very small through the resistor, slowly charging the first capacitor or simultaneously charging the first and second capacitors. The small-current pre-charging plays a role in slow start-up and can solve the problem of large inrush current and arcing at the moment of connection.
[0011] In one possible implementation, the two ends of the series circuit of the second capacitor and the resistor are directly or adjacently coupled to an access pin of the first switching device and an access pin of the second switching device.
[0012] In the solution provided in this application, the two ends of the series circuit of the second capacitor and the resistor are directly or closely adjacent to one access pin of the first switching device and one access pin of the second switching device, which can reduce the potential generated by the stray inductance of the loop trace and improve the circuit performance.
[0013] In one possible implementation, a resistor-capacitor (RC) snubber circuit (first capacitor and first resistor) is connected in parallel across the two ends of the series circuit of the first and second switching devices. After the first or second switching device is turned on, the control module controls the third switching device to be turned on so as to absorb the spike voltage generated when the first or second switching device is turned off based on the RC snubber circuit.
[0014] In the solution provided in this application, after a small current pre-charge, the first or second switching device is turned on, and the third switching device is also turned on. When the first or second switching device is turned off, the absorption circuit (RC absorption circuit or RCD absorption circuit) connected in parallel across the first or second switching device can absorb the voltage spikes generated when the switching device is turned off. Simultaneously, the RC absorption circuit connected in parallel across the series circuit of the first and second switching devices can also absorb the voltage spikes generated when the first or second switching device is turned off. This more effectively clamps the voltage stress of the first or second switching device within a safe range, thereby protecting it from breakdown damage and improving the safety of the energy storage device. The second capacitor can absorb the potential generated by stray inductance between various circuits and printed circuit boards (PCBs), improving circuit performance. The turn-on of the third switching device can also bypass the resistor, reducing the resistive load in the absorption module circuit, thereby improving the absorption performance of the voltage spikes generated when the first or second switching device is turned off.
[0015] As one possible implementation, the capacitance of the first capacitor is greater than the capacitance of the second capacitor.
[0016] In the solution provided in this application, the spike voltage generated when the switching device is turned off is larger than the voltage generated by stray inductance in the circuit. Therefore, a capacitor with a larger capacitance value can be selected to absorb the spike voltage generated when the switching device is turned off, and a capacitor with a smaller capacitance value can be selected to absorb the voltage generated by stray inductance in the circuit and between PCB boards. Selecting a capacitor with an appropriate capacitance value can not only reduce the size of the capacitor and make the layout of the components between PCB boards more reasonable, but also reduce costs.
[0017] As one possible implementation, the first capacitor is an electrolytic capacitor or a tantalum capacitor.
[0018] As one possible implementation, the second capacitor is a ceramic capacitor or a film capacitor.
[0019] As one possible implementation, the first switching device, the second switching device, and the third switching device are any one of MOSFET, IGBT, relay, and silicon controlled rectifier (SCR).
[0020] The second aspect provides a control method for a control device, which can be applied to an energy storage device. The energy storage device includes multiple energy storage modules connected in series. Each energy storage module includes a power supply module, an absorption module, a first switching device, a second switching device, and a control module. In each energy storage module, the power supply module and the first switching device are connected in series between the positive and negative terminals of the energy storage module, and the power supply module and the second switching device are connected in parallel between the positive and negative terminals of the energy storage module. The method includes: controlling the first switching device of any one of the multiple energy storage modules to close and the second switching device to open through the control module, so that any one energy storage module is coupled in series with other energy storage modules, wherein the other energy storage modules are energy storage modules other than any one of the multiple energy storage modules; controlling the first switching device of any one energy storage module to open and the second switching device to close through the control module, so as to bypass any one energy storage module; and using the absorption module to perform a small current pre-charge before the first switching device or the second switching device is turned on, and to absorb the peak voltage generated when the first switching device or the second switching device is turned on after the first switching device or the second switching device is turned off.
[0021] In one possible implementation, each absorption module includes a first capacitor and a second capacitor coupled to both ends of the power module, wherein the first capacitor regulates the output voltage of the power module, and the second capacitor is pre-charged before the first or second switching device is turned on.
[0022] In one possible implementation, each absorption module includes a third switching device, a fourth switching device, and a resistor, wherein the fourth switching device is connected in series with the resistor; the control module controls the fourth switching device to turn on before the third switching device turns on, so as to charge the first capacitor individually or simultaneously the first capacitor and the second capacitor under the current limiting of the resistor.
[0023] As one possible implementation, the two ends of the second capacitor and resistor series circuit are directly or adjacently coupled to an access pin of the first switching device and an access pin of the second switching device.
[0024] As one possible implementation, an RC snubber circuit is connected in parallel across the two ends of the series circuit of the first and second switching devices; the method further includes: after the first or second switching device is turned on, the third switching device is turned on by the control module to absorb the spike voltage generated when the first or second switching device is turned off based on the RC snubber circuit.
[0025] As one possible implementation, the capacitance of the first capacitor is greater than the capacitance of the second capacitor.
[0026] As one possible implementation, the first capacitor is an electrolytic capacitor or a tantalum capacitor.
[0027] As one possible implementation, the second capacitor is a ceramic capacitor or a film capacitor.
[0028] As one possible implementation, the first switching device, the second switching device, the third switching device, and the fourth switching device are any one of MOSFET, IGBT, relay, and SCR.
[0029] The third aspect provides a photovoltaic system including a photovoltaic array and an energy storage device provided in the first aspect or any possible implementation of the first aspect connected to the photovoltaic array (e.g., directly or indirectly connected), and the output of the energy storage device can be connected (e.g., directly or indirectly connected) to a power grid.
[0030] As one possible implementation, the photovoltaic system described above may also include an inverter, and the output of the energy storage device can be connected to the power grid (e.g., directly or indirectly) through the inverter.
[0031] As one possible implementation, the photovoltaic system described above may also include a direct current (DC) / DC converter and a DC bus, with the photovoltaic array connected (e.g., directly or indirectly) to the input of the energy storage device via the DC / DC converter and the DC bus. Attached Figure Description
[0032] Figure 1 This is a schematic diagram of an energy storage device.
[0033] Figure 2 This is a schematic diagram of another type of energy storage device;
[0034] Figure 3 This is a schematic diagram illustrating an application scenario of an energy storage device provided in an embodiment of this application;
[0035] Figure 4 This is a schematic diagram of the structure of an energy storage device provided in an embodiment of this application;
[0036] Figure 5 This is a schematic diagram illustrating the working principle of an energy storage device provided in an embodiment of this application;
[0037] Figure 6 This is a schematic diagram of the structure of an energy storage module provided in an embodiment of this application;
[0038] Figure 7 This is a schematic diagram of the structure of a photovoltaic system provided in an embodiment of this application;
[0039] Figure 8 This is a schematic diagram of the structure of a photovoltaic system provided in an embodiment of this application;
[0040] Figure 9 This is a schematic diagram of the structure of a photovoltaic system provided in an embodiment of this application;
[0041] Figure 10 This is a schematic flowchart of a control method for an energy storage device provided in an embodiment of this application. Detailed Implementation
[0042] This application provides an energy storage device and its control method, as well as a photovoltaic system, which can improve the safety of the energy storage device. The technical solutions in the embodiments of this application will be described in detail below with reference to the accompanying drawings. It should be understood that the described embodiments are only some embodiments of this application, and not all embodiments.
[0043] First, to facilitate understanding of the embodiments of this application, the specific technical problems to be solved by this application are further analyzed and proposed. Power electronic devices, such as metal-oxide-semiconductor field-effect transistors (MOSFETs) and insulated-gate bipolar transistors (IGBTs), can be applied in power conversion applications, such as frequency converters, ballasts, power adapters, wind and solar power, switch control, battery connection and bypass, and static var generator (SVG) module bypass control. Power electronic devices have fast turn-on speed, low switching losses, and high energy density, but their withstand voltage and overcurrent capabilities are relatively low. When electronic devices are used as switching protection devices in batteries, they need to be cut off under high current conditions, which is usually accompanied by large voltage stress. If the voltage stress that the device withstands exceeds its specifications, it will cause damage to the device and affect the use of the battery.
[0044] In the description of this application, power electronic devices are used as examples of switching devices for illustration. This will be explained uniformly here and will not be repeated hereafter.
[0045] Currently, there are various technical solutions for realizing energy storage devices. Two examples are listed below.
[0046] Please see Figure 1 , Figure 1 This is a schematic diagram of an energy storage device. (Example) Figure 1As shown, taking a battery as an example of an energy storage device, the diagram includes a power source, a parasitic inductance Ls, a capacitor C, and a switching device S. Capacitor C acts as an absorption circuit, connected in parallel to both the power source and the switching device S. When the switching device S is disconnected, the power source and the parasitic inductance Ls in the circuit generate a large potential, leading to increased voltage stress at the moment the switching device S is disconnected, potentially damaging it. To clamp the voltage stress of the switching device S within a certain range, an absorption circuit (capacitor C) is usually connected in parallel across the switching device S. The main function of capacitor C in the absorption circuit is to absorb the voltage spike at the moment the switching device is disconnected. Due to the characteristic that the voltage across the capacitor does not change abruptly, the voltage stress of the switching device S can be clamped within a safe range, thus protecting the switching device S and preventing breakdown damage. Although capacitor C can absorb the voltage spike when the switching device S is disconnected, its direct parallel connection to the battery can result in a relatively large inrush current and arcing at the moment of connection.
[0047] Please see Figure 2 , Figure 2 This is a schematic diagram of another type of energy storage device. For example... Figure 2 As shown, taking a battery as an example of an energy storage device, the circuit includes a power supply, parasitic inductance Ls, capacitor C, diode D, resistor R, and switching device S. Diode D connected in parallel with resistor R and then in series with capacitor C forms an absorption circuit. This absorption circuit is connected in parallel to both the power supply and the switching device S. When the switching device S is disconnected, the power supply and the parasitic inductance Ls in the circuit generate a large potential, leading to increased voltage stress at the moment the switching device S is disconnected, which may damage it. To clamp the voltage stress of the switching device S within a certain range, an absorption circuit (Resistor-Capacitance-Diode (RCD) circuit) is usually added across the switching device S. The diode D in the absorption circuit primarily clamps the voltage on the bus side of the switching device S, and the capacitor C absorbs the voltage spike at the moment the switching device S is disconnected. Simultaneously, capacitor C discharges through resistor R. Due to the characteristic that the voltage at the capacitor terminals does not change abruptly, the voltage stress of the switching device S can be clamped within a safe range, thereby protecting the switching device S and preventing breakdown damage. Although the absorption circuit can absorb voltage spikes when the switching device S is turned off to some extent, the actual layout of the switching device S and the absorption circuit may result in an excessively large loop. An excessively large absorption loop will weaken the voltage spike absorption effect and fail to achieve the desired protection. Moreover, the capacitance C in the absorption circuit is generally large, and when installed on the battery bus, there will be a relatively large inrush current and arcing at the moment of connection.
[0048] To address the aforementioned problems, this application provides an energy storage device.
[0049] The energy storage device provided in this application embodiment is applicable to various application fields such as new energy smart microgrids, power transmission and distribution, or new energy fields (such as photovoltaic grid connection or wind power grid connection), photovoltaic power generation, or wind power generation, or electric equipment (such as various electric equipment). The specific application can be determined according to the actual application scenario, and no restrictions are imposed here.
[0050] The energy storage device provided in this application embodiment is adaptable to both high-power and low-power energy storage application scenarios, such as photovoltaic power supply scenarios, wind power grid-connected power supply scenarios, electric vehicle power supply scenarios, or other application scenarios. The following description will use a photovoltaic power supply application scenario as an example; further details will not be repeated here. Please refer to [link to relevant documentation]. Figure 3 , Figure 3 This is a schematic diagram illustrating an application scenario of an energy storage device provided in an embodiment of this application. For example... Figure 3 As shown, the photovoltaic system includes a photovoltaic array, an energy storage device, a positive DC bus, and a negative DC bus. The photovoltaic array can be connected to the input of the energy storage device via the positive and negative DC buses, and the output of the energy storage device can be connected to the power grid via the positive and negative DC buses. The photovoltaic array can be composed of multiple photovoltaic strings connected in series and parallel, where each photovoltaic string can include multiple photovoltaic modules (also called solar panels or photovoltaic panels). The energy storage device includes multiple energy storage modules connected in series.
[0051] In a photovoltaic (PV) system, PV modules can charge energy storage devices, which then supply power to the grid. Alternatively, when the PV array's output power is high and the grid's electricity demand is low, excess energy can be stored in the energy storage device. When the PV array's output power is low and the grid's electricity demand is high, the stored energy can be fed back into the grid. During charging, the control module in the energy storage device can adjust its connection with other energy storage modules based on the status of each module's power supply module. For example, if a module's power supply module is fully charged or damaged, it can be disconnected from the series-connected array of energy storage modules. If the module's power supply module is charging normally, it can be connected back into the series-connected array of energy storage modules, thus ensuring the normal charging of the energy storage modules. During discharge, the control module in the energy storage device can adjust its connection with other energy storage modules based on the status of each module's power supply module. For example, if a module's power supply module is in a discharged or damaged state, it can be disconnected from the series of connected modules. Conversely, if the module's power supply module is in a normal discharge state, it can be connected back into the series, ensuring normal discharge. Disconnecting or connecting an energy storage module can be achieved by closing / opening a switching device. However, opening a switching device usually involves significant voltage stress. If the voltage stress exceeds the device's specifications, it can be damaged and malfunction. Therefore, protecting the switching device is crucial. A voltage absorption module can be connected in parallel across the switching device. When the switching device is opened, the absorption module absorbs the voltage spike generated during this process, clamping the voltage stress within a safe range and protecting the device from breakdown damage, thus improving the safety of the energy storage device. The following will combine... Figures 4 to 8 This application provides illustrative examples of the energy storage device, photovoltaic system, and their working principles.
[0052] Please see Figure 4 , Figure 4 This is a schematic diagram of the structure of an energy storage device provided in an embodiment of this application. Figure 4 As shown, the energy storage device 10 may include multiple energy storage modules, such as N energy storage modules (i.e., Figure 4 The energy storage module 10 consists of energy storage modules 101, 102, ..., 10N-1, and 10N, which are connected in series. The energy storage device 10 can be coupled to the DC bus 20.
[0053] It should be noted that coupling refers to conductive connection, including direct connection or connection through switching devices and / or resistors and other conducting devices. This application will provide a unified explanation here, and will not elaborate further hereafter.
[0054] Each of the N energy storage modules may include a power supply module, an absorption module, a first switching device S1, a second switching device S2, and a control module. The power supply module and the first switching device may be connected in series between the positive and negative terminals of the energy storage module, and the power supply module and the second switching device may be connected in parallel between the positive and negative terminals of the energy storage module.
[0055] The control module can be used to control the closing of the first switching device and the opening of the second switching device of any one of the multiple energy storage modules, so that any one energy storage module can be connected in series with other energy storage modules, and the other energy storage modules are the energy storage modules other than any one of the multiple energy storage modules.
[0056] The control module can be used to control the first switching device of any energy storage module to open and the second switching device to close, so as to bypass any energy storage module;
[0057] The absorption module can be used to precharge a small current before the first or second switching device is turned on, and to absorb the spike voltage generated when the first or second switching device is turned off after the first or second switching device is turned on.
[0058] Multiple energy storage modules can store or release energy, such as through charging and discharging. When multiple energy storage modules are in a charging or discharging state, the control module can control the coupling method between any one energy storage module and the others based on the state of charge or voltage of the power module within that module. For example, when multiple energy storage modules are charging, if the control module determines that a power module is fully charged or damaged, it can control the first switching device of any one of the energy storage modules to open and the second switching device to close, thus bypassing that module and disconnecting it from the group of energy storage modules. If the control module determines that a power module is charging normally, it can control the first switching device of any one of the energy storage modules to close and the second switching device to open, thus connecting that module in series with the others and disconnecting it from the group of energy storage modules. When the first or second switching device changes from closed to open, the parasitic inductance in the power module generates a large potential, leading to increased voltage stress when the first or second switching device is disconnected, which may damage the first or second switching device. Secondly, since the power module contains electrical energy, a significant inrush current and arcing can occur at the moment of connection when the absorption module is installed on the power module bus. In this application, a small-current pre-charge is performed before the first or second switching device is turned on, which solves the problem of large inrush current and arcing at the moment of connection when the absorption module is installed on the power module bus. After the first or second switching device is turned on, the absorption module can absorb the voltage spike when the first or second switching device is turned off, clamping the voltage stress of the first and second switching devices within a safe range, thereby protecting the switching devices from breakdown damage and improving the safety of the energy storage device.
[0059] See, for example Figure 5 , Figure 5 This is a schematic diagram illustrating the working principle of an energy storage device provided in an embodiment of this application. Figure 5 As shown, in one possible implementation, the energy storage device 10 is in a charging state, and the photovoltaic array can be connected to the DC bus 20 as the input terminal of the energy storage device 10 to charge the energy storage device 10. The energy storage device 10 contains N energy storage modules. Assuming that the power module of energy storage module 101 is in a fully charged or damaged state; ...; and the power module of energy storage module 10N is in a normal charging state, then for energy storage module 101, the control module can control the first switching device S1 to open and the second switching device S2 to close; ...; for energy storage module 10N, the control module can control the first switching device S1 to close and the second switching device S2 to open. It can be seen that the input current flows through the second switching device S2 of energy storage module 101, ..., until it flows through the power module of energy storage module 10N to charge the power module in each energy storage module.
[0060] In another possible implementation, the energy storage device 10 is in a discharging state, and its output can be connected to the DC bus 20 to supply power to the grid. The energy storage device 10 contains N energy storage modules. Assuming that the power module of energy storage module 101 is in a discharged or damaged state; ...; and the power module of energy storage module 10N is in a normal discharging state, then for energy storage module 101, the control module can control the first switching device S1 to open and the second switching device S2 to close; ...; for energy storage module 10N, the control module can control the first switching device S1 to close and the second switching device S2 to open. It can be seen that the current in the power module of energy storage module 10N flows through each energy storage module, ... until it flows through the second switching device S2 of energy storage module 101. The total output current of the multiple series-connected energy storage modules supplies power to the grid.
[0061] It is understood that the energy storage device 10 may include N energy storage modules connected in series. For example, the power module in the energy storage module may be a single battery, and the energy storage device 10 may be a battery pack or battery cluster containing multiple batteries. The power module in the energy storage module may also be a battery string composed of batteries connected in series, and the energy storage device 10 may be a battery pack containing multiple battery strings. The power module in the energy storage module may also be a DC source or a capacitor, etc.
[0062] In the energy storage device 10, the control module can control the closing of the first switching device and the opening of the second switching device to connect the energy storage module in series with other energy storage modules, and control the opening of the first switching device and the closing of the second switching device to bypass the energy storage module to other energy storage modules, so that the total current flows through multiple energy storage modules. The absorption module can perform a small-current pre-charge before the first or second switching device is turned on, which can solve the problem of large inrush current and arcing at the moment of connection when the absorption module is installed on the power module bus. After the first or second switching device is turned on, the absorption module can absorb the voltage spike when the first or second switching device is turned off, clamping the voltage stress of the first and second switching devices within a safe range, thereby protecting the switching devices from breakdown damage and improving the safety of the energy storage device. The pre-charging refers to the charging action before the first switch is closed. The small current refers to the current through the second switching device being smaller than the current flowing through the second switching device due to the current-limiting resistor R2. By pre-charging the first capacitor C1 with a small current before turning on the first switching device, arcing will not occur due to a large current conduction. Because the first capacitor C1 is a bus capacitor, its capacitance is generally very large, much larger than that of the second capacitor C2. If the first capacitor C1 is directly connected to the two ends of the power supply, it will generate a large instantaneous current, resulting in strong arcing and causing safety hazards such as burning and fire.
[0063] For example, please see Figure 6, Figure 6 This is a schematic diagram of the structure of an energy storage module provided in an embodiment of this application. Figure 6 The energy storage module 101 shown is Figure 4 Any one of the N energy storage modules shown. Figure 4 On the basis of, such as Figure 6 As shown, the energy storage module 101 includes a power supply module, an absorption module, a first switching device S1, a second switching device S2, and a control module. The power supply module and the first switching device S1 can be connected in series between the positive and negative terminals of the energy storage module, and the power supply module and the second switching device S2 can be connected in parallel between the positive and negative terminals of the energy storage module. Each absorption module may include a first capacitor C1 and a second capacitor C2, which are coupled across the two ends of the power supply module. The first capacitor C1 can regulate the output voltage of the power supply module, and the second capacitor C2 can be pre-charged before the first switching device S1 or the second switching device S2 is turned on. Pre-charging before the first switching device S1 or the second switching device S2 is activated can play a role in slow start-up, thereby solving the problem of large inrush current and arcing at the moment of connection when the absorption module is installed on the power supply module bus.
[0064] Furthermore, each absorption module may include a third switching device Q1 and a pre-charging circuit, wherein the pre-charging circuit may include a fourth switching device Q2 and a resistor R2, which are coupled in series. A control module can be used to control the fourth switching device Q2 to conduct before the third switching device Q1 conducts, so as to pre-charge the first capacitor C1 alone or simultaneously the first capacitor C1 and the second capacitor C2 with a small current. Before the first switching device S1 or the second switching device S2 conducts, the control module first conducts the fourth switching device Q2 for small-current pre-charging. Specifically, when the absorption module includes the first capacitor C1 and the second capacitor C2, since the first capacitor C1 and the second capacitor C2 are coupled across the two ends of the power module, when the absorption module is installed on the power module bus, there will be a large inrush current and arcing problem at the moment of connection. Therefore, by conducting the fourth switching device Q2, the current through the resistor R2 is made very small, slowly charging the first capacitor C1 or simultaneously the first capacitor C1 and the second capacitor C2. The small-current pre-charging plays a role in slow start-up, which can solve the problem of large inrush current and arcing at the moment of connection.
[0065] Furthermore, an RC absorption circuit (first capacitor C1 and first resistor R1) is connected in parallel across the two ends of the series circuit of the first switching device S1 and the second switching device S2. After the first switching device S1 or the second switching device S2 is turned on, the control module is used to control the third switching device Q1 to be turned on, so as to absorb the spike voltage generated when the first switching device S1 or the second switching device S2 is turned off based on the RC absorption circuit. Specifically, after a small current pre-charge, the first switching device S1 or the second switching device S2 is turned on, and the control module turns on the third switching device Q1. When the first switching device S1 or the second switching device S2 is turned off, the absorption circuit (RC absorption circuit or RCD absorption circuit, only the RC absorption circuit is shown in the figure, i.e., the third resistor R3 and the third capacitor C3) connected in parallel across the first switching device S1 or the second switching device S2 absorbs the peak voltage generated when the switching device is turned off. At the same time, the RC absorption circuit (first capacitor C1 and first resistor R1) connected in parallel across the series circuit of the first switching device S1 and the second switching device S2 can also absorb the peak voltage generated when the first switching device S1 or the second switching device S2 is turned off. This can more effectively clamp the voltage stress of the first switching device S1 or the second switching device S2 within a safe range, thereby protecting the first switching device S1 or the second switching device S2 from breakdown damage, and thus improving the safety of the energy storage device. The second capacitor C2 can also absorb the potential generated by stray inductance between various circuits and printed circuit boards (PCBs), which can improve circuit performance. The conduction of the third switching device Q1 can also bypass resistor R2, reducing the impedance of the circuit of the third switching device Q1 in the absorption module. When the impedance is very small, it can improve the absorption performance of the peak voltage generated when the first switching device S1 or the second switching device S2 is turned off.
[0066] Optionally, after the first capacitor C1 and the second capacitor C2 are pre-charged with a small current, the control module can control the third switching device Q1 to remain in the on state. That is, when the third switching device Q1 is on, the absorption module is always in a state of protecting the first switching device S1 and the second switching device S2.
[0067] Furthermore, each absorption module may also include a diode D. A first capacitor C1 is series-coupled to a third switching device Q1. A pre-charging circuit is parallel-coupled across the third switching device Q1. The first capacitor C1, through diode D and a first resistor R1, is parallel-coupled to the positive and negative terminals of the power module via the third switching device Q1. Diode D is also parallel-coupled to the first resistor R1. It can be understood that the RC absorption circuit parallel across the series circuit of the first switching device S1 and the second switching device S2 can also be an RCD absorption circuit. Compared to the RC absorption circuit, the RCD absorption circuit can improve the absorption performance of the voltage spikes generated when the first switching device S1 or the second switching device S2 is turned off. During the pre-charging of the first capacitor C1, after it is fully charged, the voltage of the first capacitor C1 is equal to the voltage of the power module, and diode D can be in a non-conducting state. The principle is explained below using the parallel RCD absorption circuit across the series circuit of the first switching device S1 and the second switching device S2 as an example:
[0068] If the current is constant, the parasitic inductance Ls in the power module has no voltage drop. When the first switching device S1 or the second switching device S2 is turned off, there will be a current decrease. As the current decreases, the parasitic inductance Ls generates a voltage drop, resulting in a reverse potential to prevent the current from decreasing. Due to the reverse potential, the voltage at Vbus increases, turning on the diode D. The voltage is transferred to the first capacitor C1, allowing the first capacitor C1 to absorb the voltage spike generated when the first switching device S1 or the second switching device S2 is turned off. According to the law of conservation of energy, this is equivalent to converting the electrical energy on the parasitic inductance Ls to the first capacitor C1. Since the voltage at the capacitor terminals does not change abruptly, the voltage stress on the first switching device S1 or the second switching device S2 can be clamped within a safe range, thereby protecting the first switching device S1 or the second switching device S2 from breakdown damage and improving the safety of the energy storage device. The electrical energy in the first capacitor C1 can be released through the first resistor R1. The voltage drop at Vbus is higher than that at the first capacitor C1, so the diode D conducts. The first capacitor C1 absorbs the electrical energy on the parasitic inductance Ls until the potential at Vbus drops down, at which point the diode D will no longer conduct.
[0069] Furthermore, in the PCB layout, the two ends of the series circuit of the second capacitor C2 and resistor R2 are directly or closely coupled to one input pin of the first switching device S1 and one input pin of the second switching device S2. This reduces the potential generated by the stray inductance of the loop traces and improves circuit performance. It should be noted that the circuit of the absorption module needs to be very small, and the physical positions of the first capacitor C1 and the second capacitor C2 can be very close to the first switching device S1 and the second switching device S2 to improve the absorption performance of the absorption module.
[0070] Due to the presence of the third switching device Q1 and the fourth switching device Q2, the first capacitor C1 and the second capacitor C2 are not directly coupled to the bus side of the power module during installation. This solves the problem of large inrush current and arcing at the moment of connection when the absorption module is installed on the power module bus.
[0071] One possible implementation is that the capacitance of the first capacitor C1 is greater than the capacitance of the second capacitor C2. The capacitance of the first capacitor C1 can satisfy the expression:
[0072]
[0073] Where Ls represents the parasitic inductance in the power module, I1 and I2 represent the current value when the switching device is turned off and the initial current value of the switching device, respectively, and ΔU represents the difference between the voltage value when the switching device is turned off and the initial voltage value of the switching device.
[0074] It's understandable that a larger capacitor provides stronger current compensation for the circuit, but this also increases parasitic inductance. Due to this parasitic inductance, the capacitor's discharge circuit will resonate at a certain frequency. At this resonant point, the capacitor's impedance is low, and the discharge circuit's impedance is at its minimum. However, when the frequency exceeds the resonant point, the discharge circuit's impedance begins to increase, meaning the capacitor's current-providing capability begins to decline. A larger capacitor value results in a lower resonant frequency, and a smaller frequency range where the capacitor can effectively compensate for current. To ensure the capacitor's ability to provide high-frequency current, a larger capacitor is not always better. While large-capacity capacitors can carry a large amount of charge, they also have a larger load, increasing the charging and discharging time and thus reducing the capacitor's high-frequency performance. Furthermore, large capacitors often have greater parasitic inductance, reducing filtering effectiveness and affecting circuit stability. Therefore, capacitor values must be allocated according to need to ensure optimal device performance. In this embodiment, the potential generated by the parasitic inductance of the disconnected switching device is greater than the potential generated by the stray inductance in the circuit. Therefore, a first capacitor C1 with a larger capacitance can be selected to absorb the potential generated by the parasitic inductance of the disconnected switching device, while a second capacitor C2 with a smaller capacitance can be selected to absorb the potential generated by the stray inductance in the circuit and between PCB boards. In this embodiment, selecting a capacitor with an appropriate capacitance not only reduces the size of the capacitor, making the layout of components between PCB boards more reasonable, but also reduces costs.
[0075] For example, the first capacitor C1 can be a large-capacity capacitor such as an electrolytic capacitor or a tantalum capacitor. The second capacitor C2 can be a small-capacity capacitor such as a ceramic capacitor or a film capacitor. It should be noted that the embodiments of this application do not limit the types of the first and second capacitors.
[0076] In one possible implementation, the first, second, third, and fourth switching devices mentioned above can be MOSFETs, IGBTs, gallium nitride field-effect transistors (GaN FETs), transistors, relays, SCRs, or other mechanical switching devices such as relays, or switching devices capable of performing switching functions. It should be noted that this application does not limit the types of the first, second, and third switching devices. Furthermore, the aforementioned switching devices can be made of silicon semiconductor material Si, or third-generation wide-bandgap semiconductor material silicon carbide (SiC), or gallium nitride (GaN), or diamond, or zinc oxide (ZnO), or other materials. The specific type of the switching device can be determined by the actual circuit topology and actual operating requirements of the energy storage device 10, and is not limited here.
[0077] One possible implementation is that if the first switching device, the second switching device, the third switching device, and the fourth switching device are transistor devices, then the control module can couple the gates of the first switching device, the second switching device, the third switching device, and the fourth switching device, respectively.
[0078] Among some feasible implementation methods, the following will provide an example of a photovoltaic system incorporating energy storage devices. Please refer to [link / reference needed]. Figure 7 , Figure 7 This application provides a schematic diagram of the structure of a photovoltaic system. (See diagram below.) Figure 7 As shown, the photovoltaic system 1 may include a photovoltaic array 30 and an energy storage device 10 coupled to the photovoltaic array 30 (e.g., directly or indirectly coupled). The output of the energy storage device 10 may be coupled (e.g., directly or indirectly coupled) to the power grid. The energy storage device 10 includes multiple energy storage modules coupled in series. The control module can adjust the coupling relationship between each energy storage module and other energy storage modules according to the state of the power module of each energy storage module, for example, by switching it out of or into multiple energy storage modules connected in series. Switching out of or into a certain energy storage module can be achieved by closing / opening a switching device. However, when the switching device is opened, it is usually accompanied by a large voltage stress. If the voltage stress on the device exceeds its specification range, it will cause the device to be damaged and unable to work normally. Therefore, the protection of the switching device is particularly important. An absorption module can be connected in parallel across the two ends of the switching device. When the switching device is opened, the absorption module absorbs the peak voltage generated when the switching device is opened, which can clamp the voltage stress of the switching device within a safe range, thereby protecting the switching device from breakdown damage, improving the safety of the energy storage device, and thus improving the safety of the photovoltaic system.
[0079] Please see also Figure 8 , Figure 8This is a schematic diagram of a photovoltaic system provided in this application. In some feasible implementations, such as… Figure 8 As shown above, Figure 7 The photovoltaic system 1 shown may also include an inverter 40, and the output of the energy storage device 10 can be coupled (e.g., directly or indirectly) to the power grid through the inverter 40. During the process of supplying power to the AC power grid, the inverter 40 (e.g., a centralized photovoltaic inverter) can convert the DC voltage provided by the energy storage device 10 into AC voltage and supply power to the AC power grid based on the AC voltage.
[0080] Please see also Figure 9 , Figure 9 This is a schematic diagram of a photovoltaic system provided in this application. In some feasible implementations, such as… Figure 9 As shown above, Figure 8 The photovoltaic system 1 shown may further include a DC / DC converter 50 and a DC bus 20. The photovoltaic array 30 can be coupled to the input terminal of the energy storage device 10 through the DC / DC converter 50 and the DC bus 20, and the output terminal of the energy storage device 10 can be coupled to the power grid through an inverter 40. The DC bus 20 may include a positive DC bus and a negative DC bus (as described above). Figure 3 (The positive and negative DC buses are shown). During the process of supplying power to the AC grid, the DC / DC converter 50 can convert the DC voltage provided by the energy storage device 10 into a target DC voltage and output the target DC voltage to the inverter 40 through the DC bus 20. At this time, the inverter 40 can convert the target DC voltage into AC voltage and supply power to the AC grid based on the AC voltage.
[0081] The control method for energy storage devices will be illustrated below. Please refer to [link / reference]. Figure 10 , Figure 10 This is a flowchart illustrating a control method for an energy storage device according to an embodiment of this application. The method is applied to an energy storage device comprising multiple energy storage modules connected in series. Each energy storage module includes a power supply module, an absorption module, a first switching device, a second switching device, and a control module. In each energy storage module, the power supply module and the first switching device are connected in series between the positive and negative terminals of the energy storage module, and the power supply module and the second switching device are connected in parallel between the positive and negative terminals of the energy storage module.
[0082] like Figure 10 As shown, the charging method includes, but is not limited to, the following steps S1001 and S1003, wherein:
[0083] S1001: The control module controls the first switching device of any one of the multiple energy storage modules to close and the second switching device to open, so that any one energy storage module is coupled in series with other energy storage modules.
[0084] Among them, the other energy storage modules are the energy storage modules other than any one of the above multiple energy storage modules.
[0085] S1002: The control module controls the first switching device of any energy storage module to open and the second switching device to close, so as to bypass any energy storage module.
[0086] S1003: The absorption module performs a small current pre-charge before the first or second switching device is turned on, and absorbs the peak voltage generated when the first or second switching device is turned off after the first or second switching device is turned on.
[0087] One possible implementation is that each absorption module includes a first capacitor and a second capacitor coupled to both ends of the power module, wherein the first capacitor regulates the output voltage of the power module, and the second capacitor is pre-charged before the first or second switching device is turned on.
[0088] One possible implementation is that each absorption module includes a third switching device, a fourth switching device, and a resistor, wherein the fourth switching device is connected in series with the resistor; the fourth switching device is controlled by the control module to turn on before the third switching device turns on, so as to precharge the first capacitor with a small current individually or simultaneously with the first and second capacitors.
[0089] One possible implementation is that the two ends of the series circuit of the second capacitor and resistor are directly or adjacently coupled to an access pin of the first switching device and an access pin of the second switching device.
[0090] One possible implementation is that an RC snubber circuit is connected in parallel across the two ends of the series circuit of the first and second switching devices; the method further includes: after the first or second switching device is turned on, the third switching device is turned on by the control module to absorb the spike voltage generated when the first or second switching device is turned off based on the RC snubber circuit.
[0091] In specific implementations, further operations performed by the control method for the energy storage device provided in this application can be found in the above-mentioned... Figures 4 to 6 The implementation methods of the energy storage device 10, energy storage module 101 and their working principle shown will not be described in detail here.
[0092] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of this application. It should be understood that the above description is only a specific embodiment of this application and is not intended to limit the scope of protection of this application. Any modifications, equivalent substitutions, improvements, etc., made on the basis of the technical solution of this application should be included within the scope of protection of this application.
Claims
1. An energy storage device, characterized in that, It includes multiple energy storage modules connected in series. Each energy storage module includes a power module, an absorption module, a first switching device, a second switching device, and a control module, wherein: In each of the energy storage modules, the power supply module and the first switching device are connected in series between the positive and negative terminals of the energy storage module, and the power supply module and the second switching device are connected in parallel between the positive and negative terminals of the energy storage module. The control module is used to control the first switching device of any one of the plurality of energy storage modules to close and the second switching device to open, so that the energy storage module and other energy storage modules are coupled in series, and the other energy storage modules are energy storage modules other than the energy storage module among the plurality of energy storage modules. The control module is used to control the first switching device of any one of the energy storage modules to open and the second switching device to close, so as to bypass any one of the energy storage modules; The absorption module is used to absorb the spike voltage generated when the first switching device or the second switching device is turned on after the first switching device or the second switching device is turned off. The absorption module is also used to charge the device before the first or second switching device is turned on.
2. The apparatus according to claim 1, characterized in that, Each of the absorption modules includes a first capacitor and a second capacitor coupled to both ends of the power module, wherein the first capacitor is used to regulate the output voltage of the power module, and the second capacitor is used to charge the first switching device or the second switching device before it is turned on.
3. The apparatus according to claim 1 or 2, characterized in that, Each of the absorption modules includes a third switching device, a fourth switching device, and a resistor, wherein the fourth switching device is connected in series with the resistor; The control module is used to control the fourth switching device to turn on before the third switching device turns on, so as to charge the first capacitor individually or simultaneously the first capacitor and the second capacitor under the current limiting of the resistor.
4. The apparatus according to claim 3, characterized in that, The two ends of the series circuit of the second capacitor and the resistor are directly or adjacently coupled to an access pin of the first switching device and an access pin of the second switching device.
5. The apparatus according to claim 3 or 4, characterized in that, A resistor-capacitor RC snubber circuit is also connected in parallel across the two ends of the series circuit of the first and second switching devices. After the first or second switching device is turned on, the control module is used to control the third switching device to turn on, so as to absorb the spike voltage generated when the first or second switching device is turned off based on the RC absorption circuit.
6. The apparatus according to claim 2 or 3, characterized in that, The capacitance of the first capacitor is greater than the capacitance of the second capacitor.
7. The apparatus according to claim 6, characterized in that, The first capacitor is an electrolytic capacitor or a tantalum capacitor.
8. The apparatus according to claim 6 or 7, characterized in that, The second capacitor is a ceramic capacitor or a film capacitor.
9. The apparatus according to any one of claims 1-8, characterized in that, The first switching device, the second switching device, the third switching device, and the fourth switching device are any one of the following: metal-oxide-semiconductor field-effect transistor (MOSFET), insulated-gate bipolar transistor (IGBT), relay, and silicon controlled rectifier (SCR).
10. A control method for an energy storage device, characterized in that, The method is applied to an energy storage device, which includes multiple energy storage modules connected in series. Each energy storage module includes a power supply module, an absorption module, a first switching device, a second switching device, and a control module. In each energy storage module, the power supply module and the first switching device are connected in series between the positive and negative terminals of the energy storage module, and the power supply module and the second switching device are connected in parallel between the positive and negative terminals of the energy storage module. The control module controls the first switching device of any one of the plurality of energy storage modules to close and the second switching device to open, so that any one of the energy storage modules is coupled in series with other energy storage modules, wherein the other energy storage modules are energy storage modules other than any one of the plurality of energy storage modules. The control module controls the first switching device of any one of the energy storage modules to open and the second switching device to close, so as to bypass any one of the energy storage modules; The absorption module absorbs the spike voltage generated when the first or second switching device is turned off after the first or second switching device is turned on. The absorption module charges the device before the first or second switching device is turned on.
11. The method according to claim 10, characterized in that, Each of the absorption modules includes a first capacitor and a second capacitor coupled to both ends of the power module, wherein the first capacitor regulates the output voltage of the power module, and the second capacitor is charged before the first switching device or the second switching device is turned on.
12. The method according to claim 10 or 11, characterized in that, Each of the absorption modules includes a third switching device, a fourth switching device, and a resistor, wherein the fourth switching device is connected in series with the resistor; The control module controls the fourth switching device to turn on before the third switching device turns on, so as to charge the first capacitor individually or simultaneously the first capacitor and the second capacitor under the current limiting of the resistor.
13. The method according to claim 12, characterized in that, The two ends of the series circuit of the second capacitor and the resistor are directly or adjacently coupled to an access pin of the first switching device and an access pin of the second switching device.
14. The method according to claim 12 or 13, characterized in that, The first and second switching devices are connected in series, and a resistor-capacitor RC snubber circuit is also connected in parallel across their ends; the method further includes: After the first or second switching device is turned on, the control module controls the third switching device to turn on, so as to absorb the spike voltage generated when the first or second switching device is turned off based on the RC absorption circuit.
15. The method according to claim 11 or 12, characterized in that, The capacitance of the first capacitor is greater than the capacitance of the second capacitor.
16. The method according to claim 15, characterized in that, The first capacitor is an electrolytic capacitor or a tantalum capacitor.
17. The method according to claim 15 or 16, characterized in that, The second capacitor is a ceramic capacitor or a film capacitor.
18. The method according to any one of claims 10-17, characterized in that, The first switching device, the second switching device, the third switching device, and the fourth switching device are any one of the following: metal-oxide-semiconductor field-effect transistor (MOSFET), insulated-gate bipolar transistor (IGBT), relay, and silicon controlled rectifier (SCR).
19. A photovoltaic system, characterized in that, The device includes a photovoltaic array and an energy storage device as described in claims 1-9 connected to the photovoltaic array, wherein the photovoltaic array is connected to the input terminal of the energy storage device and the output terminal of the energy storage device is connected to the power grid.
20. The photovoltaic system according to claim 19, characterized in that, The photovoltaic system also includes an inverter, and the output of the energy storage device is connected to the power grid through the inverter.
21. The photovoltaic system according to claim 19 or 20, characterized in that, The photovoltaic system also includes a DC / DC converter and a DC bus, and the photovoltaic array is connected to the input terminal of the energy storage device through the DC / DC converter and the DC bus.