A multi-mode switchable energy storage system and charge-discharge control method

Abstract

The application provides a multi-mode switchable energy storage system and a charging and discharging control method, which comprises an AC input unit, an AC / DC converter, n groups of bidirectional DC / DC units, n groups of battery packs, a load unit and an inductor L. The application can solve the defects of low charging efficiency caused by the low voltage of the power supply compared with the voltage between the series battery packs and the low supply voltage of a single battery pack to a high-voltage pulse load in the traditional series charging mode. Meanwhile, the power supply can not only charge the battery packs in parallel, but also the battery packs can discharge the load in parallel or in series according to the different loads.

Description

Technical Field

[0001] This invention relates to the field of energy storage battery charging and discharging technology, specifically to an energy storage system with multi-mode switching and a charging and discharging control method. Background Technology

[0002] Currently, loads with pulsating power characteristics are increasingly widely used, such as mobile digital devices, navigation lights, electric vehicles, and high-voltage pulse testing devices. Their typical characteristics are high peak power and low average power, which places higher demands on the output capability of the power supply.

[0003] For high-voltage pulse loads, parallel-connected battery packs struggle to provide sufficiently high output voltage. Furthermore, when multiple battery packs discharge in parallel, voltage differences between the packs can lead to backflow from the high-voltage packs to the low-voltage packs, causing damage. Series-connected battery packs, however, avoid circulating current issues and provide a higher output voltage to the high-voltage load through voltage superposition. Therefore, when powering high-voltage pulse loads, multiple battery packs in the battery module need to be connected in series. However, charging multiple series-connected battery packs can result in low charging efficiency if the power supply voltage is significantly lower than the total voltage of the series-connected battery packs. Parallel charging, on the other hand, provides a better match between the power supply voltage and the voltage of a single battery pack, resulting in higher charging efficiency. Current technology cannot simultaneously achieve high-efficiency parallel charging, low-voltage parallel power supply, and high-voltage pulse discharge within the same system. This results in complex circuit topologies, low switching reliability, and limited applicability. Summary of the Invention

[0004] To address the aforementioned deficiencies in existing battery pack charging and discharging circuits, this invention proposes a multi-mode energy storage system and a charging and discharging control method. This system is a high-voltage series discharge system that also features low-voltage parallel charging and discharging capabilities. It can achieve three operating modes through switch-state switching, balancing charging efficiency with high-voltage power supply requirements.

[0005] The technical solution of the present invention is as follows: A multi-mode switching energy storage system includes an AC input unit, an AC / DC converter, n sets of bidirectional DC / DC units, n unit on / off switches, n sets of battery packs, a series control unit, a load unit, and an inductor L, where n is a positive integer greater than or equal to 2. The AC input unit is connected to the AC side of the AC / DC converter via a first switching device. The DC side of the AC / DC converter outputs a positive DC bus and a negative DC bus. Each bidirectional DC / DC unit is connected to a battery pack. The low-voltage side of each bidirectional DC / DC unit is connected to the positive DC bus via a corresponding unit on / off switch. The high-voltage side of the bidirectional DC / DC unit is connected to the corresponding battery pack. Each battery pack, the corresponding bidirectional DC / DC unit, and the series control unit constitute a charging / discharging unit. Each charging / discharging unit is cascaded sequentially, and the first and last cascaded branches are connected in series with the inductor L. The load unit includes a low-voltage DC load, an AC load, and a high-voltage pulse load. The low-voltage DC load is connected in parallel between the positive and negative DC buses via a fourth switching device. The AC load is connected to the AC side of the AC / DC converter via a third switching device. The inductor L is connected to the negative DC bus via a fifth switching device and to the high-voltage pulse load via a second switching device.

[0006] Furthermore, the bidirectional DC / DC unit adopts a Buck-Boost bidirectional converter circuit structure; the low-voltage positive terminal of the bidirectional DC / DC unit is connected to the positive DC bus through the unit on / off switch, the high-voltage positive terminal is connected to the positive terminal of the corresponding battery pack, and the low-voltage negative terminal is connected to the negative terminal of the corresponding battery pack; the unit on / off switch is a charge / discharge switch.

[0007] Furthermore, the series control unit includes a controllable switch and a unidirectional conduction device; the first power terminal of the controllable switch is connected to the positive terminal of the corresponding battery pack, and the second power terminal is connected to the cathode of the unidirectional conduction device and leads out a first electrical port; the anode of the unidirectional conduction device is connected to the negative terminal of the corresponding battery pack and leads out a second electrical port; in each charging and discharging unit, the second electrical port of the later unit is connected to the first electrical port of the earlier unit, and the inductor L is connected in series between the second electrical port of the first unit and the first electrical port of the last unit.

[0008] Furthermore, the controllable switching transistor is an IGBT, with its collector serving as the first power terminal and its emitter serving as the second power terminal; the unidirectional conducting device is a diode.

[0009] Furthermore, within each individual charging / discharging unit, a buffer capacitor is connected in parallel across the two ends of the battery pack; the buffer capacitor is used to filter the battery pack terminal voltage and suppress voltage spikes at the moment the controllable switch is turned off.

[0010] Furthermore, the first to fifth switching devices are all contactors; a DC-side filter capacitor is connected in parallel to the DC output terminal of the AC / DC converter.

[0011] The present invention also provides a charging and discharging control method for the above-mentioned energy storage system. The method has three switchable operating modes: grid parallel charging mode, parallel discharging power supply mode, and series high-voltage pulse discharge mode.

[0012] Furthermore, the grid parallel charging mode is a working mode in which the AC input unit charges n battery packs in parallel. The specific control steps are as follows: close the first switching device, all unit on / off switches and the fifth switching device, and open the second switching device, the third switching device, the fourth switching device and all controllable switches; the AC power is rectified into DC power by the AC / DC converter, and the current flows out from the positive DC bus, and is then shunted to the low-voltage side of the corresponding bidirectional DC / DC unit through the on / off switches of each unit. After being boosted by the bidirectional DC / DC unit, the current is output from the positive terminal of the high-voltage side to charge the corresponding battery pack; the charging current flows out from the negative terminal of each battery pack, and is then converged to the inductor L through the corresponding unidirectional conducting device and the inter-unit connection path, and then returns to the negative DC bus through the fifth switching device, forming a parallel charging circuit for n battery packs, realizing synchronous parallel charging of multiple battery packs.

[0013] Furthermore, the parallel discharge power supply mode is a working mode in which n battery packs discharge in parallel to AC loads and / or low-voltage DC loads. The specific control steps are as follows: disconnect the first switching device, the second switching device, and all controllable switching transistors, and keep all unit on / off switches and the fifth switching device in the closed state; close the third switching device and / or the fourth switching device according to the load power supply requirements; the DC power output from each battery pack is converted by the Buck step-down converter of the corresponding bidirectional DC / DC unit, output from the positive terminal of the low-voltage side, and converges on the positive DC bus side through the unit on / off switch; part of the converged DC current directly supplies power to the low-voltage DC load through the fourth switching device, and the other part is input into the AC / DC converter and inverted into AC power, and then supplies power to the AC load through the third switching device; the discharge current returns to the negative terminal of the corresponding battery pack through the negative DC bus, the fifth switching device, the inductor L, and the unidirectional conduction device of each unit, forming a parallel discharge circuit of n battery packs, realizing synchronous parallel discharge power supply of multiple battery packs.

[0014] Furthermore, the series high-voltage pulse discharge mode is a working mode in which n battery packs discharge in series to a high-voltage pulse load. The specific control steps are as follows: disconnect the first switching device, all unit on / off switches, the fifth switching device, the third switching device, and the fourth switching device; close the second switching device and all controllable switching transistors; the n battery packs are connected in series through the corresponding conducting controllable switching transistors to form a high-voltage series discharge circuit; the discharge current flows out from the positive terminal of the first battery pack, passes through the conducting controllable switching transistors, the subsequent battery packs, the inductor L, the second switching device, and the high-voltage pulse load in sequence, and then returns to the negative terminal of the first battery pack; the unidirectional conductivity of the unidirectional conducting device is used to block the parallel path of the discharge current, so that the n battery packs output high-voltage DC power in a fully series configuration to power the high-voltage pulse load.

[0015] This invention provides an energy storage system capable of both low-voltage parallel charging and discharging, as well as high-voltage series discharging. Based on a low-voltage parallel charging circuit, it achieves parallel discharging and series high-voltage pulse discharging of multiple battery packs through simple switching, effectively solving the shortcomings of low efficiency in traditional series charging and insufficient supply voltage in parallel discharging. Through independent bidirectional DC / DC unit control, it realizes balanced parallel charging and discharging of each battery pack, as well as the series high-voltage output function of the battery packs to the load.

[0016] Compared with traditional series charging and parallel discharging circuits, the present invention has the following advantages: 1. When the power grid charges multiple battery packs in parallel, the matching degree between the power supply voltage and the terminal voltage of a single battery pack is high, resulting in higher charging conversion efficiency; 2. When the battery packs are discharged in series, there is no circulating current problem between the battery packs, which avoids the risk of high-voltage batteries flowing back into low-voltage batteries and damaging them; 3. Multiple batteries connected in series can be discharged to output high voltage through voltage superposition, meeting the instantaneous high voltage power supply requirements of high voltage pulse loads; 4. The same topology is compatible with three working modes, the circuit structure is simple, the switching control is simple, the system reliability is high, and it can adapt to the power supply requirements of multiple scenarios. Attached Figure Description

[0017] Figure 1 This is an overall electrical topology diagram of the multi-mode switching energy storage system described in an embodiment of the present invention; Figure 2 This is a schematic diagram of the internal circuit of the bidirectional DC / DC unit described in an embodiment of the present invention. Figure 3 This is an electrical schematic diagram of a single charging / discharging unit according to an embodiment of the present invention; Figure 4 This is a schematic diagram of the current path of the energy storage system described in this embodiment of the invention when it is in grid parallel charging mode; Figure 5 This is a schematic diagram of the current path of the energy storage system described in the embodiment of the present invention when it is in parallel discharge power supply mode; Figure 6 This is a schematic diagram of the current path of the energy storage system described in the embodiment of the present invention when it is in the series high-voltage pulse discharge mode. Detailed Implementation

[0018] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0019] The multi-mode energy storage system provided in this embodiment can flexibly switch between three working modes: parallel charging of multiple battery packs by the grid, parallel power supply of multiple battery packs to AC / DC loads, and series power supply of multiple battery packs to high-voltage pulse loads. It has both conventional energy storage power supply and high-voltage pulse output capabilities, and is suitable for power supply needs in multiple scenarios.

[0020] I. Overall Hardware Components of the System like Figure 1 As shown, the energy storage system of this invention mainly includes a 380V AC grid (AC input unit), an AC / DC converter, n sets of DC / DC chargers (i.e., bidirectional DC / DC units), n sets of battery packs, contactors KM1~KM5, charge / discharge switches K1~Kn, switching transistors S1~Sn, diodes D1~Dn, high-voltage pulse load, low-voltage DC load, AC load, inductor L, and several capacitors. Here, n is a positive integer greater than or equal to 2, and the number of charge / discharge units can be flexibly configured according to the actual output voltage and energy storage capacity requirements.

[0021] II. Specific Structure of the Core Unit 1. Bidirectional DC / DC unit structure (corresponding to) Figure 2 ) like Figure 2 As shown, each bidirectional DC / DC unit (i.e., DC / DC charger) adopts a Buck-Boost bidirectional conversion circuit structure, which has bidirectional energy transfer capability: it operates in Boost mode during charging and in Buck mode during discharging, which can realize bidirectional voltage conversion and energy interaction between the DC bus and the battery pack.

[0022] The bidirectional DC / DC unit has two ports: a low-voltage side and a high-voltage side. The positive terminal of the low-voltage side is connected to the positive DC bus DC+ of the DC output terminal of the AC / DC converter via a charge / discharge switch. The negative terminal of the high-voltage side is connected to the negative terminal U- of the corresponding battery pack. The positive terminal of the high-voltage side is connected to the positive terminal U+ of the corresponding battery pack.

[0023] In other alternative embodiments, the bidirectional DC / DC unit may also adopt other bidirectional DC / DC topologies such as half-bridge or full-bridge, as long as bidirectional buck-boost conversion can be achieved, all of which fall within the protection scope of this invention.

[0024] 2. Charge / discharge unit single-unit structure (corresponding to) Figure 3 ) Each battery pack, together with its corresponding bidirectional DC / DC unit, series control unit, and buffer capacitor, constitutes a single charge / discharge unit. All charge / discharge units have identical electrical structures. The series control unit consists of a controllable switch and a unidirectional conduction device, used to switch between series and parallel operation of the battery pack.

[0025] like Figure 3 As shown, taking the first charging / discharging unit as an example, its internal connection relationship is as follows: A buffer capacitor is connected in parallel across the two ends of the battery pack. This buffer capacitor can filter the battery pack terminal voltage, smoothing voltage fluctuations; on the other hand, it can absorb the inductance energy of the circuit at the moment the switching transistor is turned off, suppressing voltage spikes and achieving overvoltage protection for the switching transistor. The first power terminal of the controllable switching transistor is connected to the positive terminal of the battery pack; the second power terminal of the controllable switching transistor is connected to the cathode of the diode, and a first electrical port (electrical port 1) is led out from this connection node. The anode of the diode is connected to the negative terminal of the battery pack, and a second electrical port (electrical port 2) is led out from this connection node.

[0026] In this embodiment, the controllable switch can be an IGBT (Insulated Gate Bipolar Transistor) as a fully controllable power device, with its collector corresponding to the first power terminal and its emitter corresponding to the second power terminal. In other optional embodiments, the controllable switch can also be a MOSFET, a high-power thyristor, or other controllable power switching device, and the diode can be a fast recovery diode, a Schottky diode, or other unidirectional conducting device, all of which fall within the protection scope of this invention.

[0027] III. Overall Electrical Connections of the System Multiple charging and discharging units are cascaded and connected to the main circuit of the system in the following manner: except for the first charging and discharging unit, the second electrical ports of the second to nth charging and discharging units are connected to the first electrical ports of the previous charging and discharging units; an inductor L is connected in series between the second electrical port of the first charging and discharging unit and the first electrical port of the nth charging and discharging unit to form a closed unit cascade loop.

[0028] The output terminals of inductor L are divided into two independent branches: the first branch is connected to one end of contactor KM5, and the other end of contactor KM5 is connected to the negative DC bus DC- of the DC output terminal of the AC / DC converter; the second branch is connected to one end of contactor KM2, and the other end of contactor KM2 is connected to one end of the high-voltage pulse load, and the other end of the high-voltage pulse load is connected back to the negative terminal of the battery pack of the first-end charging and discharging unit, forming a complete series discharge circuit.

[0029] The overall configuration of the system load and switches is as follows: The low-voltage DC load is connected in parallel between the positive DC bus DC+ and the negative DC bus DC- at the DC output terminal of the AC / DC converter via contactor KM4, and is directly powered by the low-voltage DC power from the DC bus; the AC load is connected to the AC side of the AC / DC converter via contactor KM3, and is powered by the AC power output from the inverter of the AC / DC converter; contactor KM1 is connected between the 380V AC grid and the AC side of the AC / DC converter to control the on / off state of the grid input; charge / discharge switches K1~Kn are connected one-to-one between the positive terminal of the low-voltage side of each bidirectional DC / DC unit and the positive DC bus DC+, and are used to control the connection and disconnection of each charge / discharge unit and the DC bus; a DC-side filter capacitor is also connected in parallel at the DC output terminal of the AC / DC converter to smooth the DC bus voltage and reduce voltage ripple.

[0030] IV. Specific Implementation Process of Charge and Discharge Control Method The charging and discharging control method of this system controls the on / off states of each contactor, switching transistor, and charging / discharging switch, and can switch between three operating modes (methods). The specific control logic and current path of each mode are as follows: 1. Grid parallel charging mode (corresponding to) Figure 4 ) This mode is the operating mode for parallel charging of n battery packs from a 380V AC mains grid. The direction of current flow is as follows: Figure 4 As indicated by the middle arrow.

[0031] Control logic: Close contactor KM1, close all charge / discharge switches K1~Kn, and close contactor KM5; Open contactors KM2, KM3, and KM4, and open all switching transistors S1~Sn.

[0032] Working process: 380V AC power is input into the AC / DC converter via contactor KM1, rectified into DC power, and then output from the positive DC bus DC+.

[0033] After the current flows out from the positive DC bus DC+, it flows to point A via the charge / discharge switch K1 and is split: the first current flows into the low-voltage side of the bidirectional DC / DC unit 1, which operates in Boost mode, outputting current from the positive terminal of the high-voltage side and charging battery pack 1; the current flows out from the negative terminal of battery pack 1 and reaches point C, where it splits into two paths: one flows to point D via diode D1, and the other flows back to the negative DC bus DC- via the inter-unit connection path, inductor L, and contacts 4 and 3 of contactor KM5. The second current flows to point B via the charge / discharge switch K2, with a portion flowing into the bidirectional DC / DC unit 2. After Boost conversion, it outputs from the positive terminal of the high-voltage side and charges battery pack 2; the current flows out from the negative terminal of battery pack 2 and reaches point D, where it merges with the first current and flows through diode D2.

[0034] Similarly, the nth current flows into the bidirectional DC / DC unit n via the charge / discharge switch Kn, and after being boosted, charges battery pack n. The current flows out from the negative terminal of battery pack n and reaches point E, where it merges with the previous n-1 currents. It then flows sequentially through diode Dn, inductor L, and contacts 2 and 1 of contactor KM5, finally returning to the negative DC bus DC-. Through this circuit, n battery packs simultaneously receive grid power in parallel, achieving synchronous parallel charging of multiple battery packs.

[0035] 2. Parallel discharge power supply mode (corresponding to) Figure 5 ) This mode is a working mode in which n battery packs discharge in parallel to an AC load and / or a low-voltage DC load, and the direction of current flow is as follows: Figure 5 As indicated by the middle arrow.

[0036] Control logic: Disconnect contactors KM1 and KM2 and all switching transistors S1~Sn, while keeping all charging and discharging switches K1~Kn and contactor KM5 closed; selectively close contactors KM3 and / or KM4 according to load demand: close KM3 when supplying power only to AC loads, close KM4 when supplying power only to low-voltage DC loads, and close both KM3 and KM4 when supplying power to both types of loads.

[0037] The following explanation uses the simultaneous supply of power to both AC and low-voltage DC loads as an example: Each battery pack discharges independently, with current flowing from the positive terminal of the battery pack and entering the high-voltage side of the corresponding bidirectional DC / DC unit. The bidirectional DC / DC unit operates in Buck mode, outputting low-voltage DC power from the positive terminal of the low-voltage side. The current output from battery pack 1 is stepped down by bidirectional DC / DC unit 1 and output to point A; the current output from battery pack 2 is stepped down by bidirectional DC / DC unit 2 and output to point B, then flows to point A via charge / discharge switch K2; and so on, the current output from battery pack n is stepped down by bidirectional DC / DC unit n, then converges to point A via charge / discharge switch Kn and the preceding switch path. After the n currents converge at point A, they are divided into two power supply branches: DC power supply branch: The DC current after convergence supplies power to the low-voltage DC load through the DC bus and contactor KM4. The current flows out from the low-voltage DC load and reaches the negative DC bus DC-, and then returns to the negative terminal of the corresponding battery pack through contacts 3 and 4 of contactor KM5, inductor L, and diodes D1~Dn of each unit, forming a parallel DC power supply circuit.

[0038] The combined DC power is input to the positive DC side of the AC / DC converter, inverted to AC power, and output from the AC side, supplying power to the AC load via contactor KM3. Current flows out from the negative DC side of the AC / DC converter, then returns to the negative terminal of the corresponding battery pack via contactor KM5, inductor L, and diodes in each unit, forming a parallel AC power supply circuit. Through this circuit, n battery packs supply power simultaneously in parallel, providing stable energy to AC loads and low-voltage DC loads individually or simultaneously.

[0039] 3. Series high-voltage pulse discharge mode (corresponding to) Figure 6 ) This mode is a series discharge mode for n battery packs to a high-voltage pulse load, with the current flowing in the following direction: Figure 6 As indicated by the middle arrow.

[0040] Control logic: Disconnect contactor KM1, all charge / discharge switches K1~Kn, contactor KM5, contactor KM3, and contactor KM4; close contactor KM2 and all switching transistors S1~Sn.

[0041] Working process: After all the switching transistors S1 to Sn are turned on, the n battery packs are connected in series and superimposed through the turned-on switching transistors. The total output voltage is the sum of the voltages of the n battery packs, forming a high-voltage output capability. The discharge current flows out from the positive terminal of battery pack 1, passing sequentially through the turned-on switching transistor S1, battery pack 2, switching transistor S2... until battery pack n and switching transistor Sn; then the current flows through inductor L and contactor KM2, supplying power to the input high-voltage pulse load, and finally the current returns to the negative terminal of battery pack 1, forming a complete series discharge circuit.

[0042] In this mode, diodes D1~Dn are reverse-biased and cut off, using their unidirectional conductivity to block the parallel path of the battery pack. This ensures that all battery packs output high-voltage DC power in a fully series configuration, meeting the instantaneous high-voltage power supply requirements of high-voltage pulse loads. Inductor L is used to limit the rate of current change during series discharge, suppressing pulse current surges and improving system reliability.

[0043] The above description is only a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention; any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A multi-mode switching energy storage system, characterized in that, It includes an AC input unit, an AC / DC converter, n sets of bidirectional DC / DC units, n unit on / off switches, n battery packs, a series control unit, a load unit, and an inductor L; The AC input unit is connected to the AC side of the AC / DC converter via a first switching device, and the DC side of the AC / DC converter outputs a positive DC bus and a negative DC bus. Each bidirectional DC / DC unit is connected to a corresponding battery pack. The low-voltage side of each bidirectional DC / DC unit is connected to the positive DC bus via a corresponding unit on / off switch, and the high-voltage side of the bidirectional DC / DC unit is connected to the corresponding battery pack. Each battery pack, together with its corresponding bidirectional DC / DC unit and series control unit, constitutes a single charging and discharging unit. Each charging and discharging unit is cascaded in sequence, and the inductor L is connected in series with the first and last cascaded branches. The load unit includes a low-voltage DC load, an AC load, and a high-voltage pulse load; the low-voltage DC load is connected in parallel between the positive and negative DC buses via a fourth switching device, and the AC load is connected to the AC side of the AC / DC converter via a third switching device. The inductor L is connected to the negative DC bus via the fifth switching device and to the high-voltage pulse load via the second switching device.

2. The multi-mode switching energy storage system according to claim 1, characterized in that, The bidirectional DC / DC unit adopts a Buck-Boost bidirectional converter circuit structure; The positive terminal of the low-voltage side of the bidirectional DC / DC unit is connected to the positive DC bus through the unit's on / off switch, the positive terminal of the high-voltage side is connected to the positive terminal of the corresponding battery pack, and the negative terminal of the low-voltage side is connected to the negative terminal of the corresponding battery pack; the unit's on / off switch is a charge / discharge switch.

3. The multi-mode switchable energy storage system according to claim 1, characterized in that, The series control unit includes a controllable switch and a unidirectional conduction device; The first power terminal of the controllable switch is connected to the positive terminal of the corresponding battery pack, and the second power terminal is connected to the cathode of the unidirectional conduction device and leads out the first electrical port; the anode of the unidirectional conduction device is connected to the negative terminal of the corresponding battery pack and leads out the second electrical port. In each charging / discharging unit, the second electrical port of the next unit is connected to the first electrical port of the previous unit, and the inductor L is connected in series between the second electrical port of the first unit and the first electrical port of the last unit.

4. The multi-mode switching energy storage system according to claim 3, characterized in that, The controllable switching transistor is an IGBT, with its collector serving as the first power terminal and its emitter serving as the second power terminal; the unidirectional conducting device is a diode.

5. The multi-mode switchable energy storage system according to claim 1, characterized in that, Within each individual charging / discharging unit, a buffer capacitor is connected in parallel across the two ends of the battery pack. The buffer capacitor is used to filter the voltage at the battery pack terminals and suppress voltage spikes when the controllable switch is turned off.

6. The multi-mode switchable energy storage system according to claim 1, characterized in that, The first to fifth switching devices are all contactors; the DC output terminal of the AC / DC converter is connected in parallel with a DC-side filter capacitor.

7. A charging and discharging control method, applied to a multi-mode switchable energy storage system according to any one of claims 1 to 6, characterized in that, The method has three switchable operating modes: grid parallel charging mode, parallel discharge power supply mode, and series high-voltage pulse discharge mode.

8. The charging and discharging control method according to claim 7, characterized in that, The grid parallel charging mode is a working mode in which the AC input unit charges n battery packs in parallel. The specific control steps are as follows: Close the first switching device, all unit on / off switches and the fifth switching device, and disconnect the second switching device, the third switching device, the fourth switching device and all controllable switching transistors; Alternating current is rectified into direct current by the AC / DC converter. After the current flows out from the positive DC bus, it is shunted to the low-voltage side of the corresponding bidirectional DC / DC unit by the on / off switches of each unit. After being boosted by the bidirectional DC / DC unit, it is output from the positive terminal of the high-voltage side to charge the corresponding battery pack. After the charging current flows out from the negative terminal of each battery pack, it converges to the inductor L through the corresponding unidirectional conducting device and the inter-unit connection path, and then returns to the negative DC bus through the fifth switching device, forming a parallel charging circuit for n battery packs, realizing synchronous parallel charging of multiple battery packs.

9. The charging and discharging control method according to claim 7, characterized in that, The parallel discharge power supply mode is a working mode in which n battery packs discharge in parallel to AC loads and / or low-voltage DC loads. The specific control steps are as follows: Disconnect the first switching device, the second switching device, and all controllable switching transistors, while keeping all unit on / off switches and the fifth switching device in the closed state; close the third switching device and / or the fourth switching device according to the load power supply requirements. The DC power output from each battery pack is converted by the Buck step-down converter of the corresponding bidirectional DC / DC unit, and then output from the positive terminal of the low-voltage side and converged on the positive DC bus side through the unit on / off switch; After the DC current is combined, part of it is directly used to power the low-voltage DC load via the fourth switching device, and the other part is input to the AC / DC converter and converted into AC power, which is then used to power the AC load via the third switching device. The discharge current returns to the negative terminal of the corresponding battery pack through the negative DC bus, the fifth switching device, the inductor L, and the unidirectional conduction device of each unit, forming a parallel discharge circuit of n battery packs, realizing synchronous parallel discharge power supply of multiple battery packs.

10. The charging and discharging control method according to claim 7, characterized in that, The series high-voltage pulse discharge mode is a working mode in which n battery packs discharge in series to a high-voltage pulse load. The specific control steps are as follows: Disconnect the first switching device, all unit on / off switches, the fifth switching device, the third switching device, and the fourth switching device; close the second switching device and all controllable switching transistors. n battery packs are connected in series through corresponding conductive controllable switches to form a high-voltage series discharge circuit; The discharge current flows out from the positive terminal of the first battery pack, passes sequentially through the conducting controllable switch, subsequent battery packs, inductor L, the second switching device, and the high-voltage pulse load, and then returns to the negative terminal of the first battery pack. By utilizing the unidirectional conductivity of a unidirectional conducting device to block the parallel path of the discharge current, n battery packs are connected in series to output high-voltage DC power to supply power to a high-voltage pulse load.

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