Three-level charge-discharge control circuit

Abstract

This application discloses a three-level charge-discharge control circuit, relating to the field of energy-saving technology. The three-level charge-discharge control circuit includes: a first energy storage unit, a second energy storage unit, a first switching circuit, a second switching circuit, and an energy control unit. The energy control unit is used to detect the operating status of the first and second energy storage units; based on the operating status of the first and second energy storage units, it controls the operation of the first and second switching circuits to achieve charging, discharging, overcharge protection, and over-discharge protection for the first and / or second energy storage units. This application aims to solve the problems of low energy utilization and poor operational safety in existing variable frequency energy storage systems.

Description

Technical Field

[0001] This application relates to the field of energy-saving technology, and in particular to a three-level charge-discharge control circuit. Background Technology

[0002] Against the backdrop of increasingly urgent demands for cost reduction and efficiency improvement in the construction, industrial, and energy sectors, equipment with potential energy load characteristics, such as elevators, lifting machinery, and oil pumping units, urgently needs energy-saving upgrades. These devices typically rely on mains power, resulting in high energy consumption and an inability to maintain critical operating conditions during grid outages, impacting operational continuity and safety. More importantly, during braking or heavy-load descent, the drive system generates significant amounts of regenerative energy, which current solutions typically dissipate as heat through braking resistors, leading to energy waste and failing to achieve effective recovery and reuse.

[0003] Currently, some improvement schemes attempt to introduce energy storage units for energy feedback, but most are based on traditional two-level inverter architectures, configuring only a single energy storage branch. This makes it difficult to achieve charging and discharging control under the operation of one or more three-level inverters, resulting in low energy utilization. Therefore, there is an urgent need to propose a three-level topology and control strategy to improve system energy efficiency and operational safety.

[0004] The above content is only used to help understand the technical solution of this application and does not represent an admission that the above content is prior art. Summary of the Invention

[0005] The main purpose of this application is to provide a three-level charge-discharge control circuit, which aims to solve the problems of low energy utilization and poor operational safety of existing frequency conversion energy storage systems.

[0006] To achieve the above objectives, this application proposes a three-level charge-discharge control circuit for use in a variable frequency energy storage control system. The variable frequency energy storage control system includes one or more three-level frequency converters, each of which has three DC bus nodes. The three-level charge-discharge control circuit includes:

[0007] First energy storage unit;

[0008] The second energy storage unit, the first end of the second energy storage unit and the second end of the first energy storage unit are connected together with the second DC bus node of the one or more three-level frequency converters;

[0009] The first switching circuit has a first terminal connected to the first terminal of the first energy storage unit, and one or more second terminals of the first switch are respectively connected to the first DC bus nodes of the one or more three-level frequency converters.

[0010] The second switching circuit has a first terminal connected to the second terminal of the second energy storage unit, and one or more second terminals of the second switch are respectively connected to the third DC bus nodes of the one or more three-level frequency converters.

[0011] Energy control unit, used for:

[0012] Detect the operating status of the first energy storage unit and the second energy storage unit;

[0013] Based on the operating status of the first energy storage unit and the second energy storage unit, the operation of the first switching circuit and the second switching circuit is controlled to realize charging, discharging, overcharge protection and over-discharge protection for the first energy storage unit and / or the second energy storage unit.

[0014] In one embodiment, the number of three-level frequency converters is n, the first switching circuit includes a first diode, a first switching transistor, and n second switching transistors; the second switching circuit includes a second diode, a third switching transistor, and n fourth switching transistors; n is a positive integer greater than or equal to 1;

[0015] The negative terminal of the first diode and the first terminal of the first switching transistor are connected to the first terminal of the first energy storage unit. The second terminal of the first switching transistor and the positive terminal of the first diode are connected to the first terminals of n second switching transistors. The second terminals of the n second switching transistors are respectively connected to the first DC bus nodes of the n three-level frequency converters. The controlled terminals of the first switching transistor and the n second switching transistors are all connected to the energy control unit.

[0016] The negative terminal of the second diode and the first terminal of the third switch are connected to the first terminal of the second energy storage unit. The second terminal of the third switch and the positive terminal of the second diode are connected to the first terminals of n fourth switches. The second terminals of the n fourth switches are respectively connected to the third DC bus nodes of the n three-level frequency converters. The controlled terminals of the third switch and the n fourth switches are all connected to the energy control unit.

[0017] In one embodiment, the first energy storage unit includes a first power battery, and the second energy storage unit includes a second power battery;

[0018] The first end of the first power battery is the first end of the first energy storage unit, and the second end of the first power battery is the second end of the first energy storage unit; the second end of the second power battery is the first end of the second energy storage unit, and the first end of the second power battery is the second end of the second energy storage unit.

[0019] Alternatively, the first energy storage unit may include a first energy type battery, and the second energy storage unit may include a second energy type battery;

[0020] The first end of the first energy type battery is the first end of the first energy storage unit, and the second end of the first energy type battery is the second end of the first energy storage unit; the second end of the second energy type battery is the first end of the second energy storage unit, and the first end of the second energy type battery is the second end of the second energy storage unit.

[0021] In one embodiment, if it is detected that the state of charge of the first energy storage unit and the state of charge of the second energy storage unit are both less than a first preset charge threshold, or the voltage value of the first energy storage unit and the voltage value of the second energy storage unit are both less than a first preset voltage threshold, and the charging current value of the first terminal of the first energy storage unit and the charging current value of the second terminal of the second energy storage unit are both greater than a preset charging current value, then the first switch, n second switches, the third switch and n fourth switches are controlled to close to charge the first energy storage unit and the second energy storage unit;

[0022] If the state of charge of the first energy storage unit and the state of charge of the second energy storage unit are both greater than the second preset charge threshold, or the voltage value of the first energy storage unit and the voltage value of the second energy storage unit are both greater than the second preset voltage threshold, and the discharge current value of the first terminal of the first energy storage unit and the discharge current value of the second terminal of the second energy storage unit are both greater than the preset discharge current value, then the first switch, n second switches, the third switch and n fourth switches are controlled to close to discharge the first energy storage unit and the second energy storage unit.

[0023] If at least one of the following is detected: the state of charge of the first energy storage unit is less than the third preset charge threshold, the state of charge of the second energy storage unit is less than the third preset charge threshold, the voltage value of the first energy storage unit is less than the third preset voltage threshold, and the voltage value of the second energy storage unit is less than the third preset voltage threshold, then the first switch is controlled to disconnect from the third switch, or the second switch and the fourth switch connected to the corresponding three-level frequency converter are controlled to disconnect, so as to provide over-discharge protection for the corresponding energy storage unit.

[0024] If at least one of the following is detected: the state of charge of the first energy storage unit is greater than the fourth preset charge threshold; the state of charge of the second energy storage unit is greater than the fourth preset charge threshold; the voltage value of the first energy storage unit is greater than the fourth preset voltage threshold; and the voltage value of the second energy storage unit is greater than the fourth preset voltage threshold, then the second and fourth switching transistors connected to the corresponding three-level frequency converter are controlled to disconnect, and the first switching transistor and the third switching transistor are controlled to close, so as to provide overcharge protection for the corresponding energy storage unit.

[0025] If the energy regeneration equipment corresponding to the three-level frequency converter is under maintenance, the second and fourth switching transistors connected to the corresponding three-level frequency converter will be disconnected.

[0026] In one embodiment, the first energy storage unit includes a third power type battery, a fifth switch, a third energy type battery, and a seventh switch; the second energy storage unit includes a fourth power type battery, a sixth switch, a fourth energy type battery, and an eighth switch.

[0027] In this configuration, the first terminal of the third power battery is connected to the first terminal of the fifth switch transistor; the second terminal of the fifth switch transistor and the first terminal of the third energy battery are connected to the first terminal of the first energy storage unit; the second terminal of the third energy battery is connected to the first terminal of the seventh switch transistor; the second terminal of the seventh switch transistor, the second terminal of the third power battery, the second terminal of the fourth power battery, and the first terminal of the eighth switch transistor are connected to the second terminal of the first energy storage unit; the first terminal of the fourth power battery is connected to the first terminal of the sixth switch transistor; the second terminal of the sixth switch transistor and the first terminal of the fourth energy battery are connected to the second terminal of the second energy storage unit; the second terminal of the fourth energy battery is connected to the second terminal of the eighth switch transistor; and the controlled terminals of the fifth, sixth, seventh, and eighth switch transistors are all connected to the energy control unit.

[0028] In one embodiment, if it is detected that the state of charge of both the third power battery and the fourth power battery is less than a first preset charge threshold, or the voltage values ​​of both the third power battery and the fourth power battery are less than a first preset voltage threshold, and the charging current value at the first terminal of the first energy storage unit and the charging current value at the second terminal of the second energy storage unit are both greater than a preset charging current value, then the first switch, n second switches, the third switch and n fourth switches are controlled to close, and the fifth switch and the sixth switch are controlled to close, so as to charge the third power battery and the fourth power battery;

[0029] If it is detected that the state of charge of the third power battery is not less than the first preset charge threshold, the state of charge of the fourth power battery is not less than the first preset charge threshold, the voltage value of the third power battery is not less than the first preset voltage threshold, and the voltage value of the fourth power battery is not less than the first preset voltage threshold, and at the same time, the state of charge of both the third energy battery and the fourth energy battery is less than the first preset charge threshold, or the voltage values ​​of both the third energy battery and the fourth energy battery are less than the first preset voltage threshold, and the charging current value of the first terminal of the first energy storage unit and the charging current value of the second terminal of the second energy storage unit are both greater than the preset charging current value, then the first switch, n second switches, the third switch and n fourth switches are controlled to close, and the seventh switch and the eighth switch are controlled to close, so as to charge the third energy battery and the fourth energy battery;

[0030] If the state of charge of the third power battery and the fourth power battery is detected to be greater than the second preset charge threshold, or the voltage of the third power battery and the fourth power battery is greater than the second preset voltage threshold, and the discharge current of the first terminal of the first energy storage unit and the discharge current of the second terminal of the second energy storage unit are both greater than the preset discharge current value, then the first switch, n second switches, the third switch and n fourth switches are controlled to close, and the fifth switch and the sixth switch are controlled to close, so as to discharge the third power battery and the fourth power battery;

[0031] If it is detected that the state of charge of the third power battery is not greater than the second preset charge threshold, the state of charge of the fourth power battery is not greater than the second preset charge threshold, the voltage value of the third power battery is not greater than the first preset voltage threshold, and the voltage value of the fourth power battery is not greater than the first preset voltage threshold, and at the same time, the state of charge of both the third energy battery and the fourth energy battery is greater than the second preset charge threshold, or the voltage values ​​of both the third energy battery and the fourth energy battery are greater than the second preset voltage threshold, and the discharge current value of the first terminal of the first energy storage unit and the discharge current value of the second terminal of the second energy storage unit are both greater than the preset discharge current value, then the first switch, n second switches, the third switch and n fourth switches are controlled to close, and the seventh switch and the eighth switch are controlled to close, so as to discharge the third energy battery and the fourth energy battery;

[0032] If at least one of the following is detected: the state of charge of the third power battery is less than the third preset charge threshold, the state of charge of the fourth power battery is less than the third preset charge threshold, the voltage of the third power battery is less than the third preset voltage threshold, and the voltage of the fourth power battery is less than the third preset voltage threshold, then the first switch is controlled to disconnect from the third switch, or the second switch and the fourth switch connected to the three-level inverter are controlled to disconnect, and the fifth switch and the sixth switch are controlled to close, and the seventh switch and the eighth switch are controlled to disconnect, so as to provide over-discharge protection for the third power battery and the fourth power battery;

[0033] If at least one of the following is detected: the state of charge of the third energy type battery is less than the third preset charge threshold, the state of charge of the fourth energy type battery is less than the third preset charge threshold, the voltage value of the third energy type battery is less than the third preset voltage threshold, and the voltage value of the fourth energy type battery is less than the third preset voltage threshold, then the first switch is controlled to disconnect from the third switch, or the second switch and the fourth switch connected to the three-level inverter are controlled to disconnect, and the seventh switch and the eighth switch are controlled to close, and the fifth switch and the sixth switch are controlled to disconnect, so as to provide over-discharge protection for the third energy type battery and the fourth energy type battery;

[0034] If at least one of the following is detected: the state of charge of the third power battery is greater than the fourth preset charge threshold, the state of charge of the fourth power battery is greater than the fourth preset charge threshold, the voltage value of the third power battery is greater than the fourth preset voltage threshold, the voltage value of the fourth power battery is greater than the fourth preset voltage threshold, the state of charge of the third energy battery is greater than the fourth preset charge threshold, the state of charge of the fourth energy battery is greater than the fourth preset charge threshold, the voltage value of the third energy battery is greater than the fourth preset voltage threshold, or the voltage value of the fourth energy battery is greater than the fourth preset voltage threshold, then the second and fourth switches connected to the corresponding three-level inverter are disconnected, and the first and third switches are closed, as well as the fifth and sixth switches and the seventh and eighth switches are closed, to provide overcharge protection for the corresponding battery.

[0035] If the energy regeneration equipment corresponding to the three-level frequency converter is under maintenance, the second and fourth switching transistors connected to the corresponding three-level frequency converter will be disconnected.

[0036] In one embodiment, the first energy storage unit includes a fifth power battery, a first DC / DC converter, a ninth switch, and a fifth energy battery; the second energy storage unit includes a sixth power battery, a second DC / DC converter, a tenth switch, and a sixth energy battery.

[0037] Wherein, the first terminal of the fifth power battery is connected to the first terminal of the first DC / DC converter, the second terminal of the fifth power battery is connected to the second terminal of the first DC / DC converter, the third terminal of the first DC / DC converter and the first terminal of the fifth energy battery are connected to the first terminal of the first energy storage unit, the second terminal of the fifth energy battery is connected to the first terminal of the ninth switch, the second terminal of the ninth switch, the fourth terminal of the first DC / DC converter, the fourth terminal of the second DC / DC converter, the first terminal of the tenth switch are connected to the second terminal of the first energy storage unit, the third terminal of the second DC / DC converter and the first terminal of the sixth energy battery are connected to the second terminal of the second energy storage unit, the second terminal of the sixth energy battery is connected to the second terminal of the tenth switch, the first terminal of the sixth power battery is connected to the first terminal of the second DC / DC converter, the second terminal of the sixth power battery is connected to the second terminal of the second DC / DC converter, and the controlled terminals of the ninth switch, the tenth switch, the first DC / DC converter, and the second DC / DC converter are all connected to the energy control unit.

[0038] In one embodiment, if it is detected that the state of charge of the fifth power battery and the sixth power battery is less than a first preset charge threshold, or the voltage values ​​of the fifth power battery and the sixth power battery are both less than a first preset voltage threshold, and the charging current value of the first terminal of the first energy storage unit and the charging current value of the second terminal of the second energy storage unit are both greater than a preset charging current value, then the first switch, n second switches, the third switch and n fourth switches are controlled to close, and the first DC / DC converter and the second DC / DC converter are controlled to enter the charging state to charge the fifth power battery and the sixth power battery;

[0039] If it is detected that the state of charge of the fifth power battery is not less than the first preset charge threshold, the state of charge of the sixth power battery is not less than the first preset charge threshold, the voltage value of the fifth power battery is not less than the first preset voltage threshold, and the voltage value of the sixth power battery is not less than the first preset voltage threshold, and at the same time, the state of charge of both the fifth energy battery and the sixth energy battery is less than the first preset charge threshold, or the voltage values ​​of both the fifth energy battery and the sixth energy battery are less than the first preset voltage threshold, and the charging current value of the first terminal of the first energy storage unit and the charging current value of the second terminal of the second energy storage unit are both greater than the preset charging current value, then the first switch, n second switches, the third switch and n fourth switches are controlled to close, and the ninth switch and the tenth switch are controlled to close, so as to charge the fifth energy battery and the sixth energy battery;

[0040] If the state of charge of the fifth power battery and the sixth power battery is detected to be greater than the second preset charge threshold, or the voltage of the fifth power battery and the sixth power battery is greater than the second preset voltage threshold, and the discharge current of the first terminal of the first energy storage unit and the discharge current of the second terminal of the second energy storage unit are both greater than the preset discharge current value, then the first switch, n second switches, the third switch and n fourth switches are controlled to close, and the first DC / DC converter and the second DC / DC converter are controlled to enter the discharge state to discharge the fifth power battery and the sixth power battery;

[0041] If at least one of the following is detected: the state of charge of the fifth power battery is not greater than the second preset charge threshold, the state of charge of the sixth power battery is not greater than the second preset charge threshold, the voltage of the fifth power battery is not greater than the first preset voltage threshold, and the voltage of the sixth power battery is not greater than the first preset voltage threshold, and the state of charge of both the fifth energy battery and the sixth energy battery is greater than the second preset charge threshold, or the voltage of both the fifth energy battery and the sixth energy battery is greater than the second preset voltage threshold, and the discharge current of the first terminal of the first energy storage unit and the discharge current of the second terminal of the second energy storage unit are both greater than a preset discharge current value, then the first switch, n second switches, the third switch and n fourth switches are controlled to close, and the ninth switch and the tenth switch are controlled to close, so as to discharge the fifth energy battery and the sixth energy battery;

[0042] If at least one of the following is detected: the state of charge of the fifth power battery is less than the third preset charge threshold, the state of charge of the sixth power battery is less than the third preset charge threshold, the voltage of the fifth power battery is less than the third preset voltage threshold, and the voltage of the sixth power battery is less than the third preset voltage threshold, then the first DC / DC converter and the second DC / DC converter are controlled to enter the charging state, and the ninth switch and the tenth switch are controlled to close, so as to provide over-discharge protection for the fifth power battery and the sixth power battery;

[0043] If at least one of the following is detected: the state of charge of the fifth energy type battery is less than the third preset charge threshold, the state of charge of the sixth energy type battery is less than the third preset charge threshold, the voltage value of the fifth energy type battery is less than the third preset voltage threshold, and the voltage value of the sixth energy type battery is less than the third preset voltage threshold, then the first switch is controlled to disconnect from the third switch, and the ninth switch is controlled to close from the tenth switch, so as to provide over-discharge protection for the fifth energy type battery and the sixth energy type battery;

[0044] If it is detected that the state of charge (SOC) of the fifth power battery is less than the third preset SOC threshold, the SOC of the sixth power battery is less than the third preset SOC threshold, the voltage of the fifth power battery is less than the third preset voltage threshold, and the voltage of the sixth power battery is less than the third preset voltage threshold, and it is also detected that the SOC of the fifth energy battery is less than the third preset SOC threshold, the SOC of the sixth energy battery is less than the third preset SOC threshold, the voltage of the fifth energy battery is less than the third preset voltage threshold, and the voltage of the sixth energy battery is less than the third preset voltage threshold, then the first switch is controlled to disconnect from the third switch, or the second switch and the fourth switch connected to the corresponding three-level inverter are controlled to disconnect; and the first DC / DC converter and the second DC / DC converter are controlled to enter the charging state, and the ninth switch and the tenth switch are controlled to close, so as to provide over-discharge protection for the fifth power battery, the sixth power battery, the fifth energy battery, and the sixth energy battery;

[0045] If at least one of the following is detected: the state of charge (SOC) of the fifth power battery is greater than the fourth preset SOC threshold; the SOC of the sixth power battery is greater than the fourth preset SOC threshold; the voltage of the fifth power battery is greater than the fourth preset voltage threshold; the voltage of the sixth power battery is greater than the fourth preset voltage threshold; the SOC of the fifth energy battery is greater than the fourth preset SOC threshold; the SOC of the sixth energy battery is greater than the fourth preset SOC threshold; the voltage of the fifth energy battery is greater than the fourth preset voltage threshold; and the voltage of the sixth energy battery is greater than the fourth preset voltage threshold, then the second and fourth switches connected to the corresponding three-level inverter are disconnected, and the first and third switches are closed. The first and second DC / DC converters are also controlled to enter a discharge state, and the ninth and tenth switches are closed to provide overcharge protection for the corresponding battery.

[0046] If the energy regeneration equipment corresponding to the three-level frequency converter is under maintenance, the second and fourth switching transistors connected to the corresponding three-level frequency converter will be disconnected.

[0047] In one embodiment, the first energy storage unit includes a seventh power type battery, a third DC / DC converter, a seventh energy type battery, and a fifth DC / DC converter; the second energy storage unit includes an eighth power type battery, a fourth DC / DC converter, an eighth energy type battery, and a sixth DC / DC converter.

[0048] Specifically, the first terminal of the seventh power battery is connected to the first terminal of the third DC / DC converter, and the second terminal of the seventh power battery is connected to the second terminal of the third DC / DC converter. The first terminal of the eighth power battery is connected to the first terminal of the fourth DC / DC converter, and the second terminal of the eighth power battery is connected to the second terminal of the fourth DC / DC converter. The first terminal of the seventh energy battery is connected to the first terminal of the fifth DC / DC converter, and the second terminal of the seventh energy battery is connected to the second terminal of the fifth DC / DC converter. The first terminal of the eighth energy battery is connected to the first terminal of the sixth DC / DC converter, and the second terminal of the eighth energy battery is connected to the first terminal of the sixth DC / DC converter. Two-terminal connections are made: the third terminal of the third DC / DC converter and the third terminal of the fifth DC / DC converter are connected to the first terminal of the first energy storage unit; the third terminal of the fourth DC / DC converter and the third terminal of the sixth DC / DC converter are connected to the second terminal of the second energy storage unit; the fourth terminal of the third DC / DC converter, the fourth terminal of the fourth DC / DC converter, the fourth terminal of the fifth DC / DC converter, and the fourth terminal of the sixth DC / DC converter are connected to the second terminal of the first energy storage unit; and the controlled terminals of the third DC / DC converter, the fourth DC / DC converter, the fifth DC / DC converter, and the sixth DC / DC converter are respectively connected to the energy control unit.

[0049] In one embodiment, if the state of charge of both the seventh power battery and the eighth power battery is less than a first preset charge threshold, or the voltage of both the seventh power battery and the eighth power battery is less than a first preset voltage threshold, and the charging current of the first terminal of the first energy storage unit and the charging current of the second terminal of the second energy storage unit are both greater than a preset charging current value, then the first switch, n second switches, the third switch and n fourth switches are controlled to close, and the third DC / DC converter and the fourth DC / DC converter are controlled to enter the charging state to charge the seventh power battery and the eighth power battery;

[0050] If the state of charge (SOC) of the seventh power battery is not less than the first preset SOC threshold, the SOC of the eighth power battery is not less than the first preset SOC threshold, the voltage of the seventh power battery is not less than the first preset voltage threshold, and the voltage of the eighth power battery is not less than the first preset voltage threshold, while the SOC of both the seventh energy battery and the eighth energy battery is less than the first preset SOC threshold, or the voltage of both the seventh energy battery and the eighth energy battery is less than the first preset voltage threshold, and the charging current of the first terminal of the first energy storage unit and the charging current of the second terminal of the second energy storage unit are both greater than the preset charging current value, then the first switch, n second switches, the third switch, and n fourth switches are controlled to close, and the fifth DC / DC converter and the sixth DC / DC converter are controlled to enter the charging state to charge the seventh energy battery and the eighth energy battery;

[0051] If the state of charge of the seventh power battery and the eighth power battery is detected to be greater than the second preset charge threshold, or the voltage of the seventh power battery and the eighth power battery is greater than the second preset voltage threshold, and the discharge current of the first terminal of the first energy storage unit and the discharge current of the second terminal of the second energy storage unit are both greater than the preset discharge current value, then the first switch, n second switches, the third switch and n fourth switches are controlled to close, and the third DC / DC converter and the fourth DC / DC converter are controlled to enter the discharge state to discharge the seventh power battery and the eighth power battery;

[0052] If the state of charge of the seventh power battery is not greater than the second preset charge threshold, the state of charge of the eighth power battery is not greater than the second preset charge threshold, the voltage of the seventh power battery is not greater than the first preset voltage threshold, and the voltage of the eighth power battery is not greater than the first preset voltage threshold, while the state of charge of both the seventh energy battery and the eighth energy battery is greater than the second preset charge threshold, or the voltage of both the seventh energy battery and the eighth energy battery is greater than the second preset voltage threshold, and the discharge current of the first terminal of the first energy storage unit and the discharge current of the second terminal of the second energy storage unit are both greater than the preset discharge current value, then the first switch, n second switches, the third switch and n fourth switches are controlled to close, and the fifth DC / DC converter and the sixth DC / DC converter are controlled to enter the discharge state to discharge the seventh energy battery and the eighth energy battery;

[0053] If at least one of the following is detected: the state of charge of the seventh power battery is less than the third preset charge threshold; the state of charge of the eighth power battery is less than the third preset charge threshold; the voltage of the seventh power battery is less than the third preset voltage threshold; and the voltage of the eighth power battery is less than the third preset voltage threshold, and the state of charge of both the seventh energy battery and the eighth energy battery is not less than the third preset charge threshold, or the voltage of both the seventh energy battery and the eighth energy battery is not less than the third preset voltage threshold, then the third DC / DC converter and the fourth DC / DC converter are controlled to enter the charging state, and the fifth DC / DC converter and the sixth DC / DC converter are controlled to enter the discharging state, so as to provide over-discharge protection for the seventh power battery and the eighth power battery;

[0054] If at least one of the following is detected: the state of charge of the seventh energy type battery is less than the third preset charge threshold; the state of charge of the eighth energy type battery is less than the third preset charge threshold; the voltage of the seventh energy type battery is less than the third preset voltage threshold; and the voltage of the eighth energy type battery is less than the third preset voltage threshold, and the state of charge of both the seventh power type battery and the eighth power type battery is not less than the third preset charge threshold, or the voltage of both the seventh power type battery and the eighth power type battery is not less than the third preset voltage threshold, then the first switch and the third switch are disconnected, and the fifth DC / DC converter and the sixth DC / DC converter are controlled to enter the charging state to provide over-discharge protection for the seventh energy type battery and the eighth energy type battery;

[0055] If it is detected that the state of charge (SOC) of the seventh power battery is less than the third preset SOC threshold, the SOC of the eighth power battery is less than the third preset SOC threshold, the voltage of the seventh power battery is less than the third preset voltage threshold, and the voltage of the eighth power battery is less than the third preset voltage threshold, and it is also detected that the SOC of the seventh energy battery is less than the third preset SOC threshold, the SOC of the eighth energy battery is less than the third preset SOC threshold, the voltage of the seventh energy battery is less than the third preset voltage threshold, and the voltage of the eighth energy battery is less than the third preset voltage threshold, then the first switch is controlled to disconnect from the third switch, or the second switch and the fourth switch connected to the corresponding three-level inverter are controlled to disconnect; and the third DC / DC converter and the fourth DC / DC converter are controlled to enter the charging state, and the fifth DC / DC converter and the sixth DC / DC converter are controlled to enter the charging state, so as to provide over-discharge protection for the seventh power battery, the eighth power battery, the seventh energy battery, and the eighth energy battery;

[0056] If at least one of the following is detected: the state of charge (SOC) of the seventh power battery is greater than the fourth preset SOC threshold; the SOC of the eighth power battery is greater than the fourth preset SOC threshold; the voltage of the seventh power battery is greater than the fourth preset voltage threshold; the voltage of the eighth power battery is greater than the fourth preset voltage threshold; the SOC of the seventh energy battery is greater than the fourth preset SOC threshold; the SOC of the eighth energy battery is greater than the fourth preset SOC threshold; the voltage of the seventh energy battery is greater than the fourth preset voltage threshold; and the voltage of the eighth energy battery is greater than the fourth preset voltage threshold, then the second and fourth switches connected to the corresponding three-level inverters are disconnected, and the first and third switches are closed. The third and fourth DC / DC converters, as well as the fifth and sixth DC / DC converters, are also controlled to enter a discharge state, thereby providing overcharge protection for the seventh power battery, the eighth power battery, the seventh energy battery, and the eighth energy battery.

[0057] If the energy regeneration equipment corresponding to the three-level frequency converter is under maintenance, the second and fourth switching transistors connected to the corresponding three-level frequency converter will be disconnected.

[0058] This application employs a three-level charge-discharge control circuit, which includes a first energy storage unit, a second energy storage unit, a first switching circuit, a second switching circuit, and an energy control unit. The energy control unit can detect the state of charge, voltage, current, and other operating states of the first and second energy storage units. Based on the detected parameters and considering the power consumption, power supply, or maintenance conditions of one or more three-level frequency converters in the variable frequency energy storage control system, it dynamically adjusts the on / off states of the switching devices in the first and second switching circuits to implement safe charge-discharge strategies such as charging, discharging, overcharge protection, and over-discharge protection for the first and / or second energy storage units. Thus, by using dual energy storage units to store and release energy separately, energy saving is achieved in the three-level topology, resulting in lower switching losses and better harmonic performance. Through the dynamic control of the energy control unit, idle energy storage units can be avoided, maximizing their cycle efficiency and improving energy utilization. Furthermore, when overcharging or over-discharging is detected in the first energy storage unit and / or the second energy storage unit, overcharge or over-discharge protection is implemented through the first and second switching circuits, improving the safety of charging and discharging in the three-level topology. Thus, this application solves the problems of low energy utilization and poor operational safety in existing variable frequency energy storage systems. Attached Figure Description

[0059] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0060] Figure 1 A schematic diagram of the structure of an embodiment of the three-level charge-discharge control circuit of this application;

[0061] Figure 2 This is a schematic diagram of another embodiment of the three-level charge-discharge control circuit of this application;

[0062] Figure 3 A first structural schematic diagram of the first and second energy storage units is provided for an embodiment of the three-level charge-discharge control circuit of this application;

[0063] Figure 4 A second structural schematic diagram of the first and second energy storage units is provided for an embodiment of the three-level charge-discharge control circuit of this application;

[0064] Figure 5 A third structural schematic diagram of the first and second energy storage units is provided for an embodiment of the three-level charge-discharge control circuit of this application;

[0065] Figure 6 A fourth structural schematic diagram of the first and second energy storage units is provided for an embodiment of the three-level charge-discharge control circuit of this application;

[0066] Figure 7 A fifth structural schematic diagram of the first and second energy storage units is provided for an embodiment of the three-level charge-discharge control circuit of this application.

[0067] Explanation of icon numbers:

[0068]

[0069] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0070] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0071] It should be noted that all directional indicators (such as up, down, left, right, front, back, etc.) in the embodiments of this application are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicator will also change accordingly.

[0072] Furthermore, the use of terms such as "first" and "second" in this application is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. Additionally, the technical solutions of the various embodiments can be combined with each other, but only on the basis of being achievable by those skilled in the art. When the combination of technical solutions is contradictory or impossible to implement, such a combination of technical solutions should be considered non-existent and not within the scope of protection claimed in this application.

[0073] Currently, some improvement solutions attempt to introduce energy storage units for energy feedback, but most are based on the traditional two-level inverter architecture, with only a single energy storage branch configured, making it difficult to achieve charging and discharging control under the operation of one or more three-level inverters, resulting in low energy utilization.

[0074] This application proposes a three-level charge-discharge control circuit.

[0075] Please see Figure 1In one embodiment of this application, the three-level charge-discharge control circuit is applied to a variable frequency energy storage control system. The variable frequency energy storage control system includes one or more three-level frequency converters, each of which has three DC bus nodes. The three-level charge-discharge control circuit includes:

[0076] First energy storage unit;

[0077] The second energy storage unit, the first end of the second energy storage unit, the second end of the first energy storage unit, and the second DC bus node N of one or more three-level frequency converters are connected together;

[0078] The first switching circuit has its first terminal connected to the first terminal of the first energy storage unit, and one or more second terminals of the first switch are respectively connected to the first DC bus node P of one or more three-level frequency converters.

[0079] The second switching circuit has its first terminal connected to the second terminal of the second energy storage unit, and one or more second terminals of the second switch are respectively connected to the third DC bus node Q of one or more three-level frequency converters.

[0080] Energy control unit, used for:

[0081] Detect the operating status of the first energy storage unit and the second energy storage unit;

[0082] Based on the operating status of the first energy storage unit and the second energy storage unit, the operation of the first switching circuit and the second switching circuit is controlled to realize charging, discharging, overcharge protection and over-discharge protection for the first energy storage unit and / or the second energy storage unit.

[0083] It should be noted that when there is only one three-level frequency converter, the first terminal and the second terminal of the second energy storage unit are connected to the second DC bus node N of the three-level frequency converter. The second terminal of the first switching circuit is connected to the first DC bus node P of the three-level frequency converter, and the second terminal of the second switching circuit is connected to the third DC bus node Q of the three-level frequency converter. When there are multiple three-level frequency converters, the first terminal and the second terminal of the second energy storage unit are connected to the second DC bus node N of multiple three-level frequency converters. The multiple second terminals of the first switching circuit are connected one-to-one to the first DC bus node P of the multiple three-level frequency converters, and the multiple second terminals of the second switching circuit are connected one-to-one to the third DC bus node Q of the multiple three-level frequency converters.

[0084] It should be noted that the first energy storage unit may include a power-type battery and / or an energy-type battery, and the second energy storage unit may also include a power-type battery and / or an energy-type battery. The power-type battery is a battery with a charge / discharge rate greater than a first preset rate, supporting rapid, short-term, high-rate charge / discharge functionality, and can be implemented using supercapacitors, high-rate power batteries, etc. The energy-type battery is a battery with a charge / discharge rate less than or equal to the first preset rate, supporting low-rate, long-term charge / discharge functionality, and can be implemented using lithium batteries, storage batteries, sodium batteries, etc. The first and second switching circuits may include switching devices such as switching transistors and devices supporting unidirectional conduction such as diodes, enabling independent and controllable connections between one end of each energy storage unit and each three-level frequency converter, supporting on-demand injection or recovery of energy from the three-level frequency converter. The energy control unit may include microcontrollers, current sensors and other control devices. It can detect the state of charge, voltage, current and other operating states of the first and second energy storage units. Based on the parameters obtained from the above detection, and in combination with the power consumption, power supply or maintenance conditions of one or more three-level frequency converters, it can dynamically adjust the on and off states of the switching devices of the first and second switching circuits, and execute safe charging and discharging strategies such as charging, discharging, overcharge protection, over-discharge protection and maintenance protection.

[0085] Please see Figure 1 One or more three-level frequency converters are connected to the first and second energy storage units via a DC bus. The DC bus is a three-wire system with P, N, and Q. The first and second energy storage units have the same voltage level and capacity configuration parameters. The first energy storage unit is charged and discharged through the PN DC circuit, and the second energy storage unit is charged and discharged through the NQ DC circuit, realizing energy recovery and reuse. The energy control unit can detect the electrical energy (including voltage, current, and power) on the three-wire P, N, and Q circuits. It communicates with the energy storage units via bus communication (including CAN, RS484, NET, daisy chain, etc.) to obtain the battery operation information inside the energy storage units. It communicates with the switching transistors of the first and second switching circuits through several contacts and directly controls the opening / closing of the switching transistors according to the control logic. In this way, the energy control unit can control the charging and discharging process of the PN DC circuit and the NQ DC circuit through the first and second switching circuits respectively, realizing the energy recovery and reuse function of n three-level regenerative energy devices.

[0086] In this embodiment, due to the inherent lower switching losses and superior harmonic performance of the three-level topology, the dual energy storage units can capture regenerative energy during the positive and negative half-cycles respectively, reducing energy waste on the DC bus. Furthermore, the energy control unit controls the charging and discharging of both energy storage units based on their state, preventing idle units, maximizing their cycle efficiency, and improving energy utilization. Moreover, the three-level structure inherently possesses bus voltage clamping capability, reducing the risk of voltage spikes. Additionally, when the energy control unit detects overcharging or over-discharging in the first and / or second energy storage units, it controls the PN DC circuit and the NQ DC circuit to disconnect, improving charging and discharging safety. Thus, this embodiment solves the problems of low energy utilization and poor operational safety in existing variable frequency energy storage systems.

[0087] Please see Figure 2 In one embodiment of this application, the number of three-level frequency converters is n. The first switching circuit includes a first diode D1, a first switching transistor S1, and n second switching transistors S2; the second switching circuit includes a second diode D2, a third switching transistor S3, and n fourth switching transistors S4; n is a positive integer greater than or equal to 1.

[0088] The cathode of the first diode D1 and the first terminal of the first switch S1 are connected to the first terminal of the first energy storage unit. The second terminal of the first switch S1 and the anode of the first diode D1 are connected to the first terminals of n second switches S2. The second terminals of the n second switches S2 are respectively connected to the first DC bus nodes P of the n three-level frequency converters. The controlled terminals of the first switch S1 and the n second switches S2 are all connected to the energy control unit.

[0089] The negative terminal of the second diode D2 and the first terminal of the third switch S3 are connected to the first terminal of the second energy storage unit. The second terminal of the third switch S3 and the positive terminal of the second diode D2 are connected to the first terminals of n fourth switches S4. The second terminals of the n fourth switches S4 are respectively connected to the third DC bus nodes Q of the n three-level frequency converters. The controlled terminals of the third switch S3 and the n fourth switches S4 are all connected to the energy control unit.

[0090] In this embodiment, the first switch S1 and the third switch S3 can control the overall on / off state of the PN DC circuit and the NQ DC circuit, respectively. The n second switches S2 and the n fourth switches S4 correspond to each three-level frequency converter, which can realize independent and on-demand energy scheduling. The setting of the first diode D1 and the second diode D2 can provide reverse protection and improve circuit safety.

[0091] It should be noted that, under the default state, the first switch S1, n second switches S2, the third switch S3, and n fourth switches S4 are closed.

[0092] Please see Figure 3 and Figure 4 In one embodiment of this application, the first energy storage unit includes a first power battery C1, and the second energy storage unit includes a second power battery C2;

[0093] The first terminal of the first power battery C1 is the first terminal of the first energy storage unit, and the second terminal of the first power battery C1 is the second terminal of the first energy storage unit; the second terminal of the second power battery C2 is the first terminal of the second energy storage unit, and the first terminal of the second power battery C2 is the second terminal of the second energy storage unit.

[0094] Alternatively, the first energy storage unit includes a first energy type battery B1, and the second energy storage unit includes a second energy type battery B2;

[0095] The first end of the first energy type battery B1 is the first end of the first energy storage unit, and the second end of the first energy type battery B1 is the second end of the first energy storage unit; the second end of the second energy type battery B2 is the first end of the second energy storage unit, and the first end of the second energy type battery B2 is the second end of the second energy storage unit.

[0096] It should be noted that power-type batteries are those with a charge / discharge rate greater than the preset charge / discharge rate, while energy-type batteries are those with a charge / discharge rate less than or equal to the preset charge / discharge rate. The preset charge / discharge rate can be set according to the specific charging and discharging requirements of the energy storage inverter system, and is not limited here.

[0097] Please see Figure 2 In one embodiment of this application, if the state of charge of both the first energy storage unit and the second energy storage unit is detected to be less than a first preset charge threshold, or the voltage values ​​of both the first and second energy storage units are less than a first preset voltage threshold, it indicates that the energy levels of the first and second energy storage units are low. Simultaneously, if the charging current value at the first terminal of the first energy storage unit... The charging current value at the second terminal of the second energy storage unit If all values ​​are greater than the preset charging current value (e.g., greater than 0, which can be set according to the detection accuracy), it indicates that one or more three-level frequency converters are in a power-feeding state. At this time, the first switch S1, n second switches S2, the third switch S3 and n fourth switches S4 are kept closed to charge the first energy storage unit and the second energy storage unit.

[0098] If the state of charge (SOC) of both the first and second energy storage units is greater than a second preset SOC threshold, or if the voltage values ​​of both the first and second energy storage units are greater than a second preset voltage threshold, then it indicates that the first and second energy storage units have sufficient charge. Simultaneously, if the discharge current value at the first terminal of the first energy storage unit... The discharge current value at the second terminal of the second energy storage unit If all values ​​are greater than the preset discharge current value (e.g., greater than 0, which can be set according to the detection accuracy), it indicates that one or more three-level frequency converters are in power-on state. At this time, the first switch S1, n second switches S2, the third switch S3 and n fourth switches S4 are kept closed to discharge the first energy storage unit and the second energy storage unit.

[0099] If at least one of the following is detected: the state of charge of the first energy storage unit is less than the third preset charge threshold; the state of charge of the second energy storage unit is less than the third preset charge threshold; the voltage value of the first energy storage unit is less than the third preset voltage threshold; or the voltage value of the second energy storage unit is less than the third preset voltage threshold, it indicates that the corresponding energy storage unit is in an over-discharge state. In this case, the first switch S1 and the third switch S3 are disconnected, or the second switch S2 and the fourth switch S4 connected to the corresponding three-level frequency converter are disconnected to provide over-discharge protection for the corresponding energy storage unit. The third preset charge threshold is less than the first preset charge threshold, and the third preset voltage threshold is less than the first preset voltage threshold. At this time, only charging of the energy storage unit is possible, not discharging.

[0100] If at least one of the following is detected: the state of charge of the first energy storage unit is greater than the fourth preset charge threshold; the state of charge of the second energy storage unit is greater than the fourth preset charge threshold; the voltage value of the first energy storage unit is greater than the fourth preset voltage threshold; or the voltage value of the second energy storage unit is greater than the fourth preset voltage threshold, it indicates that the corresponding energy storage unit is in an overcharge state. In this case, the second switch S2 and the fourth switch S4 connected to the corresponding three-level inverter are disconnected, and the first switch S1 and the third switch S3 are closed to provide overcharge protection for the corresponding energy storage unit. The fourth preset charge threshold is greater than the second preset charge threshold, and the fourth preset voltage threshold is greater than the second preset voltage threshold. At this time, only discharging of the energy storage unit is possible, not charging.

[0101] If the energy regeneration equipment corresponding to the three-level frequency converter is under maintenance, the second switch S2 and the fourth switch S4 connected to the corresponding three-level frequency converter will be disconnected.

[0102] Thus, this embodiment uses a power-type battery to support rapid, short-time, high-rate charge and discharge functions; or it uses an energy-type battery to support low-rate, long-time charge and discharge functions.

[0103] Please see Figure 5 In one embodiment of this application, the first energy storage unit includes a third power type battery C3, a fifth switch S5, a third energy type battery B3, and a seventh switch S7; the second energy storage unit includes a fourth power type battery C4, a sixth switch S6, a fourth energy type battery B4, and an eighth switch S8.

[0104] Specifically, the first end of the third power battery C3 is connected to the first end of the fifth switch S5; the second end of the fifth switch S5 and the first end of the third energy battery B3 are connected to the first end of the first energy storage unit; the second end of the third energy battery B3 is connected to the first end of the seventh switch S7; the second end of the seventh switch S7, the second end of the third power battery C3, the second end of the fourth power battery C4, and the first end of the eighth switch S8 are connected to the second end of the first energy storage unit; the first end of the fourth power battery C4 is connected to the first end of the sixth switch S6; the second end of the sixth switch S6 and the first end of the fourth energy battery B4 are connected to the second end of the second energy storage unit; the second end of the fourth energy battery B4 is connected to the second end of the eighth switch S8; and the controlled ends of the fifth switch S5, the sixth switch S6, the seventh switch S7, and the eighth switch S8 are all connected to the energy control unit.

[0105] In this embodiment, if the state of charge of both the third power battery C3 and the fourth power battery C4 is less than the first preset charge threshold, or the voltage values ​​of both the third power battery C3 and the fourth power battery C4 are less than the first preset voltage threshold, it indicates that the power of the third power battery C3 and the fourth power battery C4 is low. Simultaneously, if the charging current value at the first terminal of the second energy storage unit and the charging current value at the second terminal of the second energy storage unit are both greater than the preset charging current value, it indicates that one or more three-level frequency converters are in a power-feeding state. At this time, the first switch S1, n second switches S2, the third switch S3, and n fourth switches S4 are kept closed, and the fifth switch S5 and the sixth switch S6 are closed to charge the third power battery C3 and the fourth power battery C4.

[0106] If at least one of the following is detected: the state of charge of the third power battery C3 is not less than the first preset charge threshold; the state of charge of the fourth power battery C4 is not less than the first preset charge threshold; the voltage of the third power battery C3 is not less than the first preset voltage threshold; and the voltage of the fourth power battery C4 is not less than the first preset voltage threshold, while the state of charge of the third energy battery B3 and the fourth energy battery B4 is both less than the first preset charge threshold, or the voltage of the third energy battery B3 and the fourth energy battery B4 is both less than the first preset voltage threshold, then it indicates that the third power battery C3 and / or the fourth power battery C4 have sufficient charge, and the first energy battery B1 and the second energy battery B2 have low charge. Simultaneously, if the charging current value at the first terminal of the first energy storage unit and the charging current value at the second terminal of the second energy storage unit are both greater than the preset charging current value, it indicates that one or more three-level frequency converters are in a power-feeding state. At this time, the first switch S1, n second switches S2, the third switch S3, and n fourth switches S4 are kept closed, and the seventh switch S7 and the eighth switch S8 are closed to charge the third energy type battery B3 and the fourth energy type battery B4. In this way, priority is given to charging the power type battery.

[0107] If the state of charge of both the third power battery C3 and the fourth power battery C4 is greater than the second preset charge threshold, or the voltage values ​​of both the third power battery C3 and the fourth power battery C4 are greater than the second preset voltage threshold, it indicates that the two power batteries have sufficient power. Simultaneously, if the discharge current value at the first terminal of the first energy storage unit and the discharge current value at the second terminal of the second energy storage unit are both greater than the preset discharge current value, it indicates that one or more three-level frequency converters are in a power-consuming state. At this time, the first switch S1, n second switches S2, the third switch S3, and n fourth switches S4 are kept closed, and the fifth switch S5 and the sixth switch S6 are closed to discharge the third power battery C3 and the fourth power battery C4.

[0108] If at least one of the following is detected: the state of charge of the third power battery C3 is not greater than the second preset charge threshold; the state of charge of the fourth power battery C4 is not greater than the second preset charge threshold; the voltage of the third power battery C3 is not greater than the first preset voltage threshold; and the voltage of the fourth power battery C4 is not greater than the first preset voltage threshold, and at the same time the state of charge of the third energy battery B3 and the fourth energy battery B4 is greater than the second preset charge threshold, or the voltage of the third energy battery B3 and the fourth energy battery B4 is greater than the second preset voltage threshold, it indicates that the power of the third power battery C3 and / or the fourth power battery C4 is low, and the power of the third energy battery B3 and the fourth energy battery B4 is sufficient. Simultaneously, if the discharge current value at the first terminal of the first energy storage unit and the discharge current value at the second terminal of the second energy storage unit are both greater than the preset discharge current value, it indicates that one or more three-level frequency converters are in a power-consuming state. At this time, the first switch S1, n second switches S2, the third switch S3, and n fourth switches S4 are kept closed, and the seventh switch S7 and the eighth switch S8 are closed to discharge the third energy type battery B3 and the fourth energy type battery B4. In this way, priority is given to discharging the power type battery.

[0109] If at least one of the following is detected: the state of charge (SOC) of the third power battery C3 is less than the third preset SOC threshold; the SOC of the fourth power battery C4 is less than the third preset SOC threshold; the voltage of the third power battery C3 is less than the third preset voltage threshold; and the voltage of the fourth power battery C4 is less than the third preset voltage threshold, it indicates that the corresponding power battery is in an over-discharge state. In this case, the first switch S1 is disconnected from the third switch S3, and the fifth switch S5 is closed from the sixth switch S6, while the seventh switch S7 is disconnected from the eighth switch S8; or the second switch S2 and the fourth switch S4 connected to the corresponding three-level inverter are disconnected, and the fifth switch S5 is closed from the sixth switch S6, while the seventh switch S7 is disconnected from the eighth switch S8, to provide over-discharge protection for the third power battery C3 and the fourth power battery C4. Thus, if one or more three-level inverters are in a power supply state (i.e., generating state), the over-discharged third power battery C3 and the fourth power battery C4 will be charged preferentially.

[0110] If at least one of the following is detected: the state of charge (SOC) of the third energy type battery B3 is less than the third preset SOC threshold; the SOC of the fourth energy type battery B4 is less than the third preset SOC threshold; the voltage of the third energy type battery B3 is less than the third preset voltage threshold; and the voltage of the fourth energy type battery B4 is less than the third preset voltage threshold, it indicates that the corresponding energy type battery is in an over-discharge state. In this case, the first switch S1 is disconnected from the third switch S3, and the seventh switch S7 and the eighth switch S8 are closed, while the fifth switch S5 and the sixth switch S6 are disconnected. Alternatively, the second switch S2 and the fourth switch S4 connected to the corresponding three-level inverter are disconnected, and the seventh switch S7 and the eighth switch S8 are closed, while the fifth switch S5 and the sixth switch S6 are disconnected, to provide over-discharge protection for the third energy type battery B3 and the fourth energy type battery B4. Thus, if one or more three-level inverters are in a power-feeding state, the over-discharged third energy type battery B3 and the fourth energy type battery B4 will be charged preferentially.

[0111] If at least one of the following is detected: the state of charge (SOC) of the third power battery C3 is greater than the fourth preset SOC threshold; the SOC of the fourth power battery C4 is greater than the fourth preset SOC threshold; the voltage of the third power battery C3 is greater than the fourth preset voltage threshold; the voltage of the fourth power battery C4 is greater than the fourth preset voltage threshold; the SOC of the third energy battery B3 is greater than the fourth preset SOC threshold; the SOC of the fourth energy battery B4 is greater than the fourth preset SOC threshold; the voltage of the third energy battery B3 is greater than the fourth preset voltage threshold; or the voltage of the fourth energy battery B4 is greater than the fourth preset voltage threshold, it indicates that the corresponding power battery / energy battery is overcharged. In this case, the second switch S2 and the fourth switch S4 connected to the corresponding three-level inverter are disconnected, and the first switch S1 and the third switch S3 are closed. Furthermore, the fifth switch S5 and the sixth switch S6 are closed, and the seventh switch S7 and the eighth switch S8 are closed to provide overcharge protection for the corresponding battery. At this time, only discharging of the battery is possible, not charging.

[0112] If the energy regeneration equipment corresponding to the three-level frequency converter is under maintenance, the second switch S2 and the fourth switch S4 connected to the corresponding three-level frequency converter will be disconnected.

[0113] Thus, this embodiment uses a combination of power-type batteries and energy-type batteries. By controlling the charging and discharging of the power-type batteries or the energy-type batteries according to the strategy through the switching transistor, it achieves the complementarity of rapid high-rate and low-rate long-term energy charging and discharging, which makes up for the impact of the instantaneous high current and high power of the DC bus on energy recovery, and also realizes the continuous storage and reuse of regenerated energy.

[0114] Please see Figure 6In one embodiment of this application, the first energy storage unit includes a fifth power type battery C5, a first DC / DC converter DC / DC1, a ninth switch S9, and a fifth energy type battery B5; the second energy storage unit includes a sixth power type battery C6, a second DC / DC converter DC / DC2, a tenth switch S10, and a sixth energy type battery B6.

[0115] Specifically, the first terminal of the fifth power battery C5 is connected to the first terminal of the first DC / DC converter DC / DC1, the second terminal of the fifth power battery C5 is connected to the second terminal of the first DC / DC converter DC / DC1, the third terminal of the first DC / DC converter DC / DC1 and the first terminal of the fifth energy battery B5 are connected to the first terminal of the first energy storage unit, the second terminal of the fifth energy battery B5 is connected to the first terminal of the ninth switch S9, the second terminal of the ninth switch S9, the fourth terminal of the first DC / DC converter DC / DC1, the fourth terminal of the second DC / DC converter DC / DC2, and the first terminal of the tenth switch S10 are connected to the second terminal of the first energy storage unit. The third terminal of the second DC / DC converter DC / DC2, the first terminal of the sixth energy type battery B6, and the second terminal of the second energy storage unit are connected. The second terminal of the sixth energy type battery B6 is connected to the second terminal of the tenth switch S10. The first terminal of the sixth power type battery C6 is connected to the first terminal of the second DC / DC converter DC / DC2. The second terminal of the sixth power type battery C6 is connected to the second terminal of the second DC / DC converter DC / DC2. The controlled terminals of the ninth switch S9, the tenth switch S10, the first DC / DC converter DC / DC1, and the second DC / DC converter DC / DC2 are all connected to the energy control unit.

[0116] In this embodiment, by controlling the switching frequencies of the first DC / DC1 converter and the second DC / DC2 converter, the voltage difference between the three lines of the DC bus can be kept consistent, that is, the voltage difference between P and N, ΔVPN = VP. The pressure difference between VN, Q, and N is ΔVQN = VQ VN difference | △VPN △VQN| is within the midpoint balance threshold; where VP, VQ, and VN are the voltages of the P-line, Q-line, and N-line of the DC bus closest to the battery side, respectively.

[0117] In this embodiment, if the state of charge of both the fifth power battery C5 and the sixth power battery C6 is less than the first preset charge threshold, or the voltage values ​​of both the fifth power battery C5 and the sixth power battery C6 are less than the first preset voltage threshold, it indicates that the power of the fifth power battery C5 and the sixth power battery C6 is low. Simultaneously, if the charging current value at the first terminal of the first energy storage unit and the charging current value at the second terminal of the second energy storage unit are both greater than the preset charging current value, it indicates that one or more three-level frequency converters are in a power-feeding state. At this time, the first switch S1, n second switches S2, the third switch S3, and n fourth switches S4 are kept closed, and the first DC / DC converter DC / DC1 and the second DC / DC converter DC / DC2 are controlled to enter a charging state to charge the fifth power battery C5 and the sixth power battery C6. It should be noted that the DC / DC converter enters the charging state by controlling the battery-side voltage of the DC / DC converter to be lower than the DC bus-side voltage. At this time, the DC / DC converter can step down the DC bus-side voltage and output it to charge the power battery.

[0118] If at least one of the following is detected: the state of charge (SOC) of the fifth power battery C5 is not less than the first preset SOC threshold; the SOC of the sixth power battery C6 is not less than the first preset SOC threshold; the voltage of the fifth power battery C5 is not less than the first preset voltage threshold; and the voltage of the sixth power battery C6 is not less than the first preset voltage threshold, while the SOC of both the fifth energy battery B5 and the sixth energy battery B6 is less than the first preset SOC threshold, or the voltage of both the fifth energy battery B5 and the sixth energy battery B6 is less than the first preset voltage threshold, then it indicates that the fifth power battery C5 and / or the sixth power battery C6 have sufficient charge, and the fifth energy battery B5 and the sixth energy battery B6 have low charge. Simultaneously, if the charging current value at the first terminal of the first energy storage unit and the charging current value at the second terminal of the second energy storage unit are both greater than the preset charging current value, then the first switch S1, n second switches S2, the third switch S3, and n fourth switches S4 are kept closed, and the ninth switch S9 and the tenth switch S10 are closed to charge the fifth energy type battery B5 and the sixth energy type battery B6. This ensures that power type batteries are charged preferentially.

[0119] If the state of charge (SOC) of both the fifth power battery C5 and the sixth power battery C6 is greater than the second preset SOC threshold, or the voltage values ​​of both batteries are greater than the second preset voltage threshold, it indicates that both batteries have sufficient charge. Simultaneously, if the discharge current at the first terminal of the first energy storage unit and the discharge current at the second terminal of the second energy storage unit are both greater than preset discharge current values, then the first switch S1, n second switches S2, the third switch S3, and n fourth switches S4 are kept closed, and the first DC / DC converter DC / DC1 and the second DC / DC converter DC / DC2 are controlled to enter a discharge state to discharge the fifth power battery C5 and the sixth power battery C6. It should be noted that the DC / DC converter entering a discharge state specifically means controlling the battery-side voltage of the DC / DC converter to be greater than the DC bus voltage. At this time, the DC / DC converter can step down the battery-side voltage and output it to the DC bus.

[0120] If at least one of the following is detected: the state of charge of the fifth power battery C5 is not greater than the second preset charge threshold; the state of charge of the sixth power battery C6 is not greater than the second preset charge threshold; the voltage value of the fifth power battery C5 is not greater than the first preset voltage threshold; and the voltage value of the sixth power battery C6 is not greater than the first preset voltage threshold, and at the same time, the state of charge of both the fifth energy battery B5 and the sixth energy battery B6 is greater than the second preset charge threshold, or the voltage values ​​of both the fifth energy battery B5 and the sixth energy battery B6 are greater than the second preset voltage threshold, it indicates that the power of the fifth power battery C5 and / or the sixth power battery C6 is low, and the power of the fifth energy battery B5 and the sixth energy battery B6 is sufficient. Simultaneously, if the discharge current value at the first terminal of the first energy storage unit and the discharge current value at the second terminal of the second energy storage unit are both greater than the preset discharge current value, it indicates that one or more three-level frequency converters are in a power-consuming state. At this time, the first switch S1, n second switches S2, the third switch S3, and n fourth switches S4 are kept closed, and the ninth switch S9 and the tenth switch S10 are closed to discharge the fifth energy type battery B5 and the sixth energy type battery B6. In this way, priority is given to discharging the power type batteries.

[0121] If at least one of the following is detected: the state of charge (SOC) of the fifth power battery C5 is less than the third preset SOC threshold; the SOC of the sixth power battery C6 is less than the third preset SOC threshold; the voltage of the fifth power battery C5 is less than the third preset voltage threshold; and the voltage of the sixth power battery C6 is less than the third preset voltage threshold, it indicates that the corresponding power battery is in an over-discharge state. In this case, the first DC / DC converter (DC / DC1) and the second DC / DC converter (DC / DC2) are controlled to enter a charging state, and the ninth switch (S9) and the tenth switch (S10) are controlled to close, thus providing over-discharge protection for the fifth power battery C5 and the sixth power battery C6. At this time, the energy battery can charge the power battery. It should be noted that if both the fifth energy battery B5 and / or the sixth energy battery B6 are simultaneously detected to be in an over-discharge state, a dual over-discharge control process is executed, and the energy battery does not charge the power battery in this case.

[0122] If at least one of the following is detected: the state of charge (SOC) of the fifth energy type battery B5 is less than the third preset SOC threshold; the SOC of the sixth energy type battery B6 is less than the third preset SOC threshold; the voltage of the fifth energy type battery B5 is less than the third preset voltage threshold; and the voltage of the sixth energy type battery B6 is less than the third preset voltage threshold, then the first switch S1 and the third switch S3 are disconnected; and the ninth switch S9 and the tenth switch S10 are closed to provide over-discharge protection for the fifth energy type battery B5 and the sixth energy type battery B6. At this time, if one or more three-level inverters are in a power-feeding state, the over-discharged energy type batteries are charged first. It should be noted that if the fifth power type battery C5 and / or the sixth power type battery C6 are simultaneously detected to be in an over-discharge state, a dual over-discharge control process is executed.

[0123] If at least one of the following is detected: the state of charge of the fifth power battery C5 is less than the third preset charge threshold; the state of charge of the sixth power battery C6 is less than the third preset charge threshold; the voltage of the fifth power battery C5 is less than the third preset voltage threshold; and the voltage of the sixth power battery C6 is less than the third preset voltage threshold, and if at least one of the following is detected: the state of charge of the fifth energy battery B5 is less than the third preset charge threshold; the state of charge of the sixth energy battery B6 is less than the third preset charge threshold; the voltage of the fifth energy battery B5 is less than the third preset voltage threshold; and the voltage of the sixth energy battery B6 is less than the third preset voltage threshold, then the dual over-discharge control process is executed. In the dual over-discharge control process, the first switch S1 and the third switch S3 are disconnected, or the second switch S2 and the fourth switch S4 connected to the corresponding three-level frequency converter are disconnected; and the first DC / DC converter DC / DC1 and the second DC / DC converter DC / DC2 are controlled to enter the charging state, and the ninth switch S9 and the tenth switch S10 are controlled to close, so as to provide over-discharge protection for the fifth power battery C5, the sixth power battery C6, the fifth energy battery B5 and the sixth energy battery B6.

[0124] If at least one of the following is detected: the state of charge (SOC) of the fifth power battery C5 is greater than the fourth preset SOC threshold; the SOC of the sixth power battery C6 is greater than the fourth preset SOC threshold; the voltage of the fifth power battery C5 is greater than the fourth preset voltage threshold; the voltage of the sixth power battery C6 is greater than the fourth preset voltage threshold; the SOC of the fifth energy battery B5 is greater than the fourth preset SOC threshold; the SOC of the sixth energy battery B6 is greater than the fourth preset SOC threshold; the voltage of the fifth energy battery B5 is greater than the fourth preset voltage threshold; or the voltage of the sixth energy battery B6 is greater than the fourth preset voltage threshold, it indicates that the corresponding power battery / energy battery is in an overcharged state. In this case, the second switch S2 and the fourth switch S4 connected to the corresponding three-level inverter are disconnected, and the first switch S1 and the third switch S3 are closed. The first DC / DC converter DC / DC1 and the second DC / DC converter DC / DC2 are also controlled to enter a discharge state, and the ninth switch S9 and the tenth switch S10 are closed to provide overcharge protection for the corresponding battery.

[0125] If the energy regeneration equipment corresponding to the three-level frequency converter is under maintenance, the second switch S2 and the fourth switch S4 connected to the corresponding three-level frequency converter will be disconnected.

[0126] Thus, in this embodiment, the switching transistor on the power battery is replaced with a DC / DC converter. The boost / buck conversion of the DC / DC converter is used to balance the voltage on the power battery side and the DC bus voltage, thereby achieving the midpoint balance of the three-wire system simultaneously.

[0127] Please see Figure 7 In one embodiment of this application, the first energy storage unit includes a seventh power type battery C7, a third DC / DC converter DC / DC3, a seventh energy type battery B7, and a fifth DC / DC converter DC / DC5; the second energy storage unit includes an eighth power type battery C8, a fourth DC / DC converter DC / DC4, an eighth energy type battery B8, and a sixth DC / DC converter DC / DC6.

[0128] Among them, the first terminal of the seventh power battery C7 is connected to the first terminal of the third DC / DC converter DC / DC3, and the second terminal of the seventh power battery C7 is connected to the second terminal of the third DC / DC converter DC / DC3. The first terminal of the eighth power battery C8 is connected to the first terminal of the fourth DC / DC converter DC / DC4, and the second terminal of the eighth power battery C8 is connected to the second terminal of the fourth DC / DC converter DC / DC4. The first terminal of the seventh energy battery B7 is connected to the first terminal of the fifth DC / DC converter DC / DC5, and the second terminal of the seventh energy battery B7 is connected to the second terminal of the fifth DC / DC converter DC / DC5. The first terminal of the eighth energy battery B8 is connected to the first terminal of the sixth DC / DC converter DC / DC6, and the second terminal of the eighth energy battery B8 is connected to the second terminal of the sixth DC / DC converter DC / DC6. The third terminal of the third DC / DC converter DC / DC3 and the third terminal of the fifth DC / DC converter DC / DC5 are connected to the first terminal of the first energy storage unit. The third terminal of the fourth DC / DC converter DC / DC4 and the third terminal of the sixth DC / DC converter DC / DC6 are connected to the second terminal of the second energy storage unit. The fourth terminal of the third DC / DC converter DC / DC3, the fourth DC / DC converter DC / DC4, the fifth DC / DC converter DC / DC5, and the sixth DC / DC converter DC / DC6 are connected to the second terminal of the first energy storage unit. The controlled terminals of the third DC / DC converter DC / DC3, the fourth DC / DC converter DC / DC4, the fifth DC / DC converter DC / DC5, and the sixth DC / DC converter DC / DC6 are respectively connected to the energy control unit.

[0129] In this embodiment, by controlling the switching frequencies of the third DC / DC1 converter, the fourth DC / DC4 converter, the fifth DC / DC5 converter, and the sixth DC / DC6 converter, the voltage difference between the three DC bus lines can be kept consistent, i.e., the voltage difference between P and N, ΔVPN = VP. The pressure difference between VN and S and N is ΔVQN = VQ VN difference | △VPN △VQN| is within the midpoint equilibrium threshold.

[0130] In this embodiment, if the state of charge of both the seventh power battery C7 and the eighth power battery C8 is less than the first preset charge threshold, or the voltage values ​​of both the seventh power battery C7 and the eighth power battery C8 are less than the first preset voltage threshold, it indicates that the power of the seventh power battery C7 and the eighth power battery C8 is low. Simultaneously, if the charging current value at the first terminal of the first energy storage unit and the charging current value at the second terminal of the second energy storage unit are both greater than the preset charging current value, then the first switch S1, n second switches S2, the third switch S3, and n fourth switches S4 are kept closed, and the third DC / DC converter DC / DC3 and the fourth DC / DC converter DC / DC4 are controlled to enter the charging state to charge the seventh power battery C7 and the eighth power battery C8.

[0131] If the state of charge (SOC) of the seventh power battery C7 is not less than the first preset charge threshold, the SOC of the eighth power battery C8 is not less than the first preset charge threshold, the voltage of the seventh power battery C7 is not less than the first preset voltage threshold, and the voltage of the eighth power battery C8 is not less than the first preset voltage threshold, while the SOC of the seventh energy battery B7 and the eighth energy battery B8 are both less than the first preset charge threshold, or the voltage of the seventh energy battery B7 and the eighth energy battery B8 are both less than the first preset voltage threshold, then it indicates that the seventh power battery C7 and / or the eighth power battery C8 have sufficient charge, and the seventh energy battery B7 and the eighth energy battery B8 have low charge. Simultaneously, if the charging current value at the first terminal of the first energy storage unit and the charging current value at the second terminal of the second energy storage unit are both greater than the preset charging current value, then the first switch S1, n second switches S2, the third switch S3, and n fourth switches S4 are kept closed, and the fifth DC / DC converter DC / DC5 and the sixth DC / DC converter DC / DC6 are controlled to enter the charging state to charge the seventh energy type battery B7 and the eighth energy type battery B8. In this way, priority is given to charging the power type batteries.

[0132] If the state of charge of both the seventh power battery C7 and the eighth power battery C8 is greater than the second preset charge threshold, or the voltage values ​​of both the seventh power battery C7 and the eighth power battery C8 are greater than the second preset voltage threshold, it indicates that the two power batteries are sufficiently charged. Simultaneously, if the discharge current value at the first terminal of the first energy storage unit and the discharge current value at the second terminal of the second energy storage unit are both greater than the preset discharge current value, then the first switch S1, n second switches S2, the third switch S3, and n fourth switches S4 are kept closed, and the third DC / DC converter DC / DC3 and the fourth DC / DC converter DC / DC4 are controlled to enter the discharge state to discharge the seventh power battery C7 and the eighth power battery C8.

[0133] If at least one of the following is detected: the state of charge of the seventh power battery C7 is not greater than the second preset charge threshold; the state of charge of the eighth power battery C8 is not greater than the second preset charge threshold; the voltage value of the seventh power battery C7 is not greater than the first preset voltage threshold; and the voltage value of the eighth power battery C8 is not greater than the first preset voltage threshold, and at the same time the state of charge of the seventh energy battery B7 and the eighth energy battery B8 is greater than the second preset charge threshold, or the voltage values ​​of the seventh energy battery B7 and the eighth energy battery B8 are both greater than the second preset voltage threshold, it indicates that the charge of the seventh power battery C7 and / or the eighth power battery C8 is low, and the charge of the seventh energy battery B7 and the eighth energy battery B8 is sufficient. Simultaneously, if the discharge current value at the first terminal of the first energy storage unit and the discharge current value at the second terminal of the second energy storage unit are both greater than the preset discharge current value, then the first switch S1, n second switches S2, the third switch S3, and n fourth switches S4 are kept closed, and the fifth DC / DC converter DC / DC5 and the sixth DC / DC converter DC / DC6 are controlled to enter the discharge state to discharge the seventh energy type battery B7 and the eighth energy type battery B8. In this way, priority is given to discharging the power type batteries.

[0134] If at least one of the following is detected: the state of charge (SOC) of the seventh power battery C7 is less than the third preset charge threshold; the SOC of the eighth power battery C8 is less than the third preset charge threshold; the voltage of the seventh power battery C7 is less than the third preset voltage threshold; and the voltage of the eighth power battery C8 is less than the third preset voltage threshold, and the SOC of both the seventh energy battery B7 and the eighth energy battery B8 is not less than the third preset charge threshold, or the voltage of both the seventh energy battery B7 and the eighth energy battery B8 is not less than the third preset voltage threshold, it indicates that only the corresponding power battery is in an over-discharge state. In this case, the third DC / DC converter (DC / DC3) and the fourth DC / DC converter (DC / DC4) are controlled to enter a charging state, and the fifth DC / DC converter (DC / DC5) and the sixth DC / DC converter (DC / DC6) are controlled to enter a discharging state to provide over-discharge protection for the seventh power battery C7 and the eighth power battery C8. At this time, the energy battery can charge the power battery.

[0135] If at least one of the following is detected: the state of charge (SOC) of the seventh energy type battery B7 is less than the third preset SOC threshold; the SOC of the eighth energy type battery B8 is less than the third preset SOC threshold; the voltage of the seventh energy type battery B7 is less than the third preset voltage threshold; and the voltage of the eighth energy type battery B8 is less than the third preset voltage threshold, and the SOC of both the seventh power type battery C7 and the eighth power type battery C8 is not less than the third preset SOC threshold, or the voltage of both the seventh power type battery C7 and the eighth power type battery C8 is not less than the third preset voltage threshold, it indicates that only the corresponding energy type battery is in an over-discharge state. In this case, the first switch S1 and the third switch S3 are disconnected, and the fifth DC / DC converter DC / DC5 and the sixth DC / DC converter DC / DC6 are put into a charging state to provide over-discharge protection for the seventh energy type battery B7 and the eighth energy type battery B8. At this time, the power type battery can charge the energy type battery. If one or more three-level inverters are in a power-feeding state, the over-discharged energy type battery will be charged first.

[0136] If at least one of the following is detected: the state of charge (SOC) of the seventh power battery C7 is less than the third preset charge threshold; the SOC of the eighth power battery C8 is less than the third preset charge threshold; the voltage of the seventh power battery C7 is less than the third preset voltage threshold; and the voltage of the eighth power battery C8 is less than the third preset voltage threshold, and if the SOC of the seventh energy battery B7 is less than the third preset charge threshold; the SOC of the eighth energy battery B8 is less than the third preset charge threshold; the voltage of the seventh energy battery B7 is less than the third preset voltage threshold; and the voltage of the eighth energy battery B8 is less than the third preset voltage threshold, then... If at least one of the preset voltage thresholds is selected, the first switch S1 and the third switch S3 are disconnected, or the second switch S2 and the fourth switch S4 connected to the corresponding three-level frequency converter are disconnected; and the third DC / DC converter DC / DC3 and the fourth DC / DC converter DC / DC4 are controlled to enter the charging state, and the fifth DC / DC converter DC / DC5 and the sixth DC / DC converter DC / DC6 are controlled to enter the charging state, so as to provide over-discharge protection for the seventh power battery C7, the eighth power battery C8, the seventh energy battery B7 and the eighth energy battery B8.

[0137] If at least one of the following is detected: the state of charge (SOC) of the seventh power battery C7 is greater than the fourth preset charge threshold; the SOC of the eighth power battery C8 is greater than the fourth preset charge threshold; the voltage of the seventh power battery C7 is greater than the fourth preset voltage threshold; the voltage of the eighth power battery C8 is greater than the fourth preset voltage threshold; the SOC of the seventh energy battery B7 is greater than the fourth preset charge threshold; the SOC of the eighth energy battery B8 is greater than the fourth preset charge threshold; the voltage of the seventh energy battery B7 is greater than the fourth preset voltage threshold; and the voltage of the eighth energy battery B8 is greater than the fourth preset voltage threshold, it indicates that this... If the corresponding power type battery / energy type battery is in an overcharged state, the second switch S2 and the fourth switch S4 connected to the corresponding three-level frequency converter are disconnected, and the first switch S1 and the third switch S3 are closed. The third DC / DC converter DC / DC3 and the fourth DC / DC converter DC / DC4 are controlled to enter the discharge state, and the fifth DC / DC converter DC / DC5 and the sixth DC / DC converter DC / DC6 are controlled to enter the discharge state, so as to provide overcharge protection for the seventh power type battery C7, the eighth power type battery C8, the seventh energy type battery B7 and the eighth energy type battery B8.

[0138] If the energy regeneration equipment corresponding to the three-level frequency converter is under maintenance, the second switch S2 and the fourth switch S4 connected to the corresponding three-level frequency converter will be disconnected.

[0139] Thus, in this embodiment, the switching transistors on the energy-type battery are replaced with DC / DC converters. The boost / buck conversion of the DC / DC converter is used to balance the voltage on the energy-type battery side and the DC bus voltage. This allows for dynamic adjustment of the charging and discharging rhythms of power-type and energy-type energy storage, and achieves midpoint balance in a three-wire system.

[0140] The above description is merely an exemplary embodiment of this application and does not limit the patent scope of this application. Any equivalent structural transformations made based on the technical concept of this application and the contents of the specification and drawings of this application, or direct / indirect applications in other related technical fields, are included within the patent protection scope of this application.

Claims

1. A three-level charge-discharge control circuit applied to a variable frequency energy storage control system, characterized in that, The variable frequency energy storage control system comprises one or more three-level frequency converters, each of the three-level frequency converters has three DC bus nodes, the three-level charge-discharge control circuit comprises: a first energy storage unit; a second energy storage unit, a first end of the second energy storage unit and a second end of the first energy storage unit are commonly connected with a second DC bus node of the one or more three-level frequency converters; a first switch circuit, a first end of the first switch circuit is connected with the first end of the first energy storage unit, one or more second ends of the first switch circuit are respectively connected with the first DC bus nodes of the one or more three-level frequency converters in one-to-one correspondence; a second switch circuit, a first end of the second switch circuit is connected with the second end of the second energy storage unit, one or more second ends of the second switch circuit are respectively connected with the third DC bus nodes of the one or more three-level frequency converters in one-to-one correspondence; an energy control unit, configured to: detect operating states of the first energy storage unit and the second energy storage unit; control operations of the first switch circuit and the second switch circuit according to the operating states of the first energy storage unit and the second energy storage unit, so as to realize charging, discharging, overcharging protection and over-discharging protection of the first energy storage unit and / or the second energy storage unit.

2. The three-level charge pump control circuit of claim 1, wherein, The number of the three-level frequency converters is n, the first switch circuit comprises a first diode, a first switch tube and n second switch tubes, the second switch circuit comprises a second diode, a third switch tube and n fourth switch tubes, and n is a positive integer greater than or equal to 1; a negative electrode of the first diode, a first end of the first switch tube and the first end of the first energy storage unit are connected, a second end of the first switch tube, a positive electrode of the first diode and first ends of the n second switch tubes are commonly connected, second ends of the n second switch tubes are respectively connected with the first DC bus nodes of the n three-level frequency converters in one-to-one correspondence, and controlled ends of the first switch tube and the n second switch tubes are connected with the energy control unit; a negative electrode of the second diode, a first end of the third switch tube and the first end of the second energy storage unit are connected, a second end of the third switch tube, a positive electrode of the second diode and first ends of the n fourth switch tubes are commonly connected, second ends of the n fourth switch tubes are respectively connected with the third DC bus nodes of the n three-level frequency converters in one-to-one correspondence, and controlled ends of the third switch tube and the n fourth switch tubes are connected with the energy control unit.

3. The three-level charge-pump control circuit of claim 1, wherein, The first energy storage unit comprises a first power type battery, and the second energy storage unit comprises a second power type battery; a first end of the first power type battery is the first end of the first energy storage unit, and a second end of the first power type battery is the second end of the first energy storage unit; a second end of the second power type battery is the first end of the second energy storage unit, and a first end of the second power type battery is the second end of the second energy storage unit; Alternatively, the first energy storage unit comprises a first energy type battery, and the second energy storage unit comprises a second energy type battery. The first end of the first energy type battery is the first end of the first energy storage unit, and the second end of the first energy type battery is the second end of the first energy storage unit; the second end of the second energy type battery is the first end of the second energy storage unit, and the first end of the second energy type battery is the second end of the second energy storage unit.

4. The three-level charge-pump control circuit of claim 2, wherein, If it is detected that the state of charge of the first energy storage unit and the state of charge of the second energy storage unit are both less than a first preset state of charge threshold, or the voltage value of the first energy storage unit and the voltage value of the second energy storage unit are both less than a first preset voltage threshold, and the charging current value of the first end of the first energy storage unit and the charging current value of the second end of the second energy storage unit are both greater than a preset charging current value, the first switch tube, n second switch tubes, a third switch tube and n fourth switch tubes are controlled to be closed to charge the first energy storage unit and the second energy storage unit. If it is detected that the state of charge of the first energy storage unit and the state of charge of the second energy storage unit are both greater than a second preset state of charge threshold, or the voltage value of the first energy storage unit and the voltage value of the second energy storage unit are both greater than a second preset voltage threshold, and the discharging current value of the first end of the first energy storage unit and the discharging current value of the second end of the second energy storage unit are both greater than a preset discharging current value, the first switch tube, n second switch tubes, a third switch tube and n fourth switch tubes are controlled to be closed to discharge the first energy storage unit and the second energy storage unit. If at least one of the following conditions is detected: the state of charge of the first energy storage unit is less than a third preset state of charge threshold, the state of charge of the second energy storage unit is less than a third preset state of charge threshold, the voltage value of the first energy storage unit is less than a third preset voltage threshold, and the voltage value of the second energy storage unit is less than a third preset voltage threshold, the first switch tube and the third switch tube are controlled to be opened, or the second switch tube and the fourth switch tube connected to the three-level frequency converter for use are controlled to be opened to perform over-discharge protection on the corresponding energy storage unit. If at least one of the following conditions is detected: the state of charge of the first energy storage unit is greater than a fourth preset state of charge threshold, the state of charge of the second energy storage unit is greater than the fourth preset state of charge threshold, the voltage value of the first energy storage unit is greater than a fourth preset voltage threshold, and the voltage value of the second energy storage unit is greater than the fourth preset voltage threshold, the second switch tube and the fourth switch tube connected to the three-level frequency converter for power generation are controlled to be opened, and the first switch tube and the third switch tube are controlled to be closed to perform over-charge protection on the corresponding energy storage unit. If the energy regeneration device corresponding to the three-level frequency converter is in a maintenance state, the second switch tube and the fourth switch tube connected to the corresponding three-level frequency converter are controlled to be opened.

5. The three-level charge-pump control circuit of claim 2, wherein, The first energy storage unit includes a third power type battery, a fifth switch tube, a third energy type battery and a seventh switch tube; the second energy storage unit includes a fourth power type battery, a sixth switch tube, a fourth energy type battery and an eighth switch tube; The first end of the third power type battery is connected with the first end of the fifth switch tube, the second end of the fifth switch tube, the first end of the third energy type battery and the first end of the first energy storage unit, the second end of the third energy type battery is connected with the first end of the seventh switch tube, the second end of the seventh switch tube, the second end of the third power type battery, the second end of the fourth power type battery, the first end of the eighth switch tube and the second end of the first energy storage unit are connected, the first end of the fourth power type battery is connected with the first end of the sixth switch tube, the second end of the sixth switch tube, the first end of the fourth energy type battery and the second end of the second energy storage unit are connected, the second end of the fourth energy type battery is connected with the second end of the eighth switch tube, and the controlled end of the fifth switch tube, the controlled end of the sixth switch tube, the controlled end of the seventh switch tube and the controlled end of the eighth switch tube are connected with the energy control unit.

6. The three-level charge-pump control circuit of claim 5, wherein, If it is detected that the state of charge of the third power type battery and the fourth power type battery is less than a first preset charge threshold, or the voltage value of the third power type battery and the fourth power type battery is less than a first preset voltage threshold, and the charging current value of the first end of the first energy storage unit and the charging current value of the second end of the second energy storage unit are greater than a preset charging current value, the first switch tube, n second switch tubes, a third switch tube and n fourth switch tubes are controlled to be closed, and the fifth switch tube and the sixth switch tube are controlled to be closed to charge the third power type battery and the fourth power type battery. If it is detected that at least one of the state of charge of the third power type battery is not less than the first preset charge threshold, the state of charge of the fourth power type battery is not less than the first preset charge threshold, the voltage value of the third power type battery is not less than the first preset voltage threshold, and the voltage value of the fourth power type battery is not less than the first preset voltage threshold, and the state of charge of the third energy type battery and the fourth energy type battery is less than the first preset charge threshold, or the voltage value of the third energy type battery and the fourth energy type battery is less than the first preset voltage threshold, and the charging current value of the first end of the first energy storage unit and the charging current value of the second end of the second energy storage unit are greater than a preset charging current value, the first switch tube, n second switch tubes, a third switch tube and n fourth switch tubes are controlled to be closed, and the seventh switch tube and the eighth switch tube are controlled to be closed to charge the third energy type battery and the fourth energy type battery. If it is detected that the state of charge of the third power type battery and the fourth power type battery are both greater than a second preset state of charge threshold, or the voltage values of the third power type battery and the fourth power type battery are both greater than a second preset voltage threshold, and the discharge current values of the first end of the first energy storage unit and the second end of the second energy storage unit are both greater than a preset discharge current value, the first switch tube, n second switch tubes, a third switch tube, and n fourth switch tubes are controlled to be closed, and the fifth switch tube and the sixth switch tube are controlled to be closed to discharge the third power type battery and the fourth power type battery. If it is detected that at least one of the state of charge of the third power type battery is not greater than the second preset state of charge threshold, the state of charge of the fourth power type battery is not greater than the second preset state of charge threshold, the voltage value of the third power type battery is not greater than the first preset voltage threshold, and the voltage value of the fourth power type battery is not greater than the first preset voltage threshold, and the state of charge of the third energy type battery and the fourth energy type battery are both greater than the second preset state of charge threshold, or the voltage values of the third energy type battery and the fourth energy type battery are both greater than the second preset voltage threshold, and the discharge current values of the first end of the first energy storage unit and the second end of the second energy storage unit are both greater than a preset discharge current value, the first switch tube, n second switch tubes, a third switch tube, and n fourth switch tubes are controlled to be closed, and the seventh switch tube and the eighth switch tube are controlled to be closed to discharge the third energy type battery and the fourth energy type battery. If it is detected that at least one of the state of charge of the third power type battery is less than a third preset state of charge threshold, the state of charge of the fourth power type battery is less than the third preset state of charge threshold, the voltage value of the third power type battery is less than a third preset voltage threshold, and the voltage value of the fourth power type battery is less than the third preset voltage threshold, the first switch tube and the third switch tube are controlled to be disconnected, or the second switch tube and the fourth switch tube connected to the three-level frequency converter for use are controlled to be disconnected, and the fifth switch tube and the sixth switch tube are controlled to be closed, and the seventh switch tube and the eighth switch tube are controlled to be disconnected to perform over-discharge protection on the third power type battery and the fourth power type battery. If at least one of the following conditions is detected: the state of charge of the third energy type battery is less than a third preset state of charge threshold, the state of charge of the fourth energy type battery is less than the third preset state of charge threshold, the voltage value of the third energy type battery is less than a third preset voltage threshold, and the voltage value of the fourth energy type battery is less than the third preset voltage threshold, the first switch tube and the third switch tube are controlled to be disconnected, or the second switch tube and the fourth switch tube connected to the three-level frequency converter for power consumption are controlled to be disconnected, and the seventh switch tube and the eighth switch tube are controlled to be closed, and the fifth switch tube and the sixth switch tube are controlled to be disconnected, so as to perform over-discharge protection on the third energy type battery and the fourth energy type battery. If at least one of the following conditions is detected: the state of charge of the third power type battery is greater than a fourth preset state of charge threshold, the state of charge of the fourth power type battery is greater than the fourth preset state of charge threshold, the voltage value of the third power type battery is greater than a fourth preset voltage threshold, the voltage value of the fourth power type battery is greater than the fourth preset voltage threshold, the state of charge of the third energy type battery is greater than a fourth preset state of charge threshold, the state of charge of the fourth energy type battery is greater than the fourth preset state of charge threshold, the voltage value of the third energy type battery is greater than a fourth preset voltage threshold, and the voltage value of the fourth energy type battery is greater than the fourth preset voltage threshold, the second switch tube and the fourth switch tube connected to the three-level frequency converter for power generation are controlled to be disconnected, the first switch tube and the third switch tube are controlled to be closed, and the fifth switch tube and the sixth switch tube are controlled to be closed, and the seventh switch tube and the eighth switch tube are controlled to be closed, so as to perform over-charge protection on the corresponding battery. If the energy regeneration device corresponding to the three-level frequency converter is in a maintenance state, the second switch tube and the fourth switch tube connected to the corresponding three-level frequency converter are controlled to be disconnected.

7. The three-level charge-pump control circuit of claim 2, wherein, The first energy storage unit includes a fifth power type battery, a first DC / DC converter, a ninth switch tube, and a fifth energy type battery; and the second energy storage unit includes a sixth power type battery, a second DC / DC converter, a tenth switch tube, and a sixth energy type battery. The first end of the fifth power battery is connected with the first end of the first DC / DC converter, the second end of the fifth power battery is connected with the second end of the first DC / DC converter, the third end of the first DC / DC converter and the first end of the fifth energy battery are connected with the first end of the first energy storage unit, the second end of the fifth energy battery is connected with the first end of the ninth switch tube, the second end of the ninth switch tube, the fourth end of the first DC / DC converter, the fourth end of the second DC / DC converter, the first end of the tenth switch tube are connected with the second end of the first energy storage unit, the third end of the second DC / DC converter and the first end of the sixth energy battery are connected with the second end of the second energy storage unit, the second end of the sixth energy battery is connected with the second end of the tenth switch tube, the first end of the sixth power battery is connected with the first end of the second DC / DC converter, the second end of the sixth power battery is connected with the second end of the second DC / DC converter, the controlled end of the ninth switch tube, the controlled end of the tenth switch tube, the controlled end of the first DC / DC converter and the controlled end of the second DC / DC converter are connected with the energy control unit.

8. The three-level charge pump control circuit of claim 7, wherein, If it is detected that the state of charge of the fifth power battery and the state of charge of the sixth power battery are both less than a first preset state of charge threshold, or the voltage value of the fifth power battery and the voltage value of the sixth power battery are both less than a first preset voltage threshold, and the charging current value of the first end of the first energy storage unit and the charging current value of the second end of the second energy storage unit are both greater than a preset charging current value, the first switch tube, n second switch tubes, a third switch tube and n fourth switch tubes are controlled to be closed, and the first DC / DC converter and the second DC / DC converter are controlled to enter a charging state, so as to charge the fifth power battery and the sixth power battery; If it is detected that at least one of the state of charge of the fifth power battery is not less than the first preset state of charge threshold, the state of charge of the sixth power battery is not less than the first preset state of charge threshold, the voltage value of the fifth power battery is not less than the first preset voltage threshold, and the voltage value of the sixth power battery is not less than the first preset voltage threshold, and the state of charge of the fifth energy battery and the state of charge of the sixth energy battery are both less than the first preset state of charge threshold, or the voltage value of the fifth energy battery and the voltage value of the sixth energy battery are both less than the first preset voltage threshold, and the charging current value of the first end of the first energy storage unit and the charging current value of the second end of the second energy storage unit are both greater than a preset charging current value, the first switch tube, n second switch tubes, a third switch tube and n fourth switch tubes are controlled to be closed, and the ninth switch tube and the tenth switch tube are controlled to be closed, so as to charge the fifth energy battery and the sixth energy battery; If it is detected that the state of charge of the fifth power battery and the sixth power battery are both greater than a second preset state of charge threshold, or the voltage values of the fifth power battery and the sixth power battery are both greater than a second preset voltage threshold, and the discharge current values of the first end of the first energy storage unit and the second end of the second energy storage unit are both greater than a preset discharge current value, the first switch tube, the n second switch tubes, the third switch tube and the n fourth switch tubes are controlled to be closed, and the first DC / DC converter and the second DC / DC converter are controlled to enter a discharge state, so as to discharge the fifth power battery and the sixth power battery. If at least one of the following conditions is detected: the state of charge of the fifth power battery is not greater than the second preset state of charge threshold, the state of charge of the sixth power battery is not greater than the second preset state of charge threshold, the voltage value of the fifth power battery is not greater than the first preset voltage threshold, and the voltage value of the sixth power battery is not greater than the first preset voltage threshold, and the state of charge of the fifth energy battery and the sixth energy battery are both greater than the second preset state of charge threshold, or the voltage values of the fifth energy battery and the sixth energy battery are both greater than the second preset voltage threshold, and the discharge current values of the first end of the first energy storage unit and the second end of the second energy storage unit are both greater than a preset discharge current value, the first switch tube, the n second switch tubes, the third switch tube and the n fourth switch tubes are controlled to be closed, and the ninth switch tube and the tenth switch tube are controlled to be closed, so as to discharge the fifth energy battery and the sixth energy battery. If at least one of the following conditions is detected: the state of charge of the fifth power battery is less than a third preset state of charge threshold, the state of charge of the sixth power battery is less than the third preset state of charge threshold, the voltage value of the fifth power battery is less than a third preset voltage threshold, and the voltage value of the sixth power battery is less than the third preset voltage threshold, the first DC / DC converter and the second DC / DC converter are controlled to enter a charging state, and the ninth switch tube and the tenth switch tube are controlled to be closed, so as to perform over-discharge protection on the fifth power battery and the sixth power battery. If at least one of the following conditions is detected: the state of charge of the fifth energy battery is less than a third preset state of charge threshold, the state of charge of the sixth energy battery is less than the third preset state of charge threshold, the voltage value of the fifth energy battery is less than a third preset voltage threshold, and the voltage value of the sixth energy battery is less than the third preset voltage threshold, the first switch tube and the third switch tube are controlled to be opened, and the ninth switch tube and the tenth switch tube are controlled to be closed, so as to perform over-discharge protection on the fifth energy battery and the sixth energy battery. If at least one of the following conditions is detected: the state of charge of the fifth power battery is less than a third preset charge threshold, the state of charge of the sixth power battery is less than the third preset charge threshold, the voltage value of the fifth power battery is less than a third preset voltage threshold, and the voltage value of the sixth power battery is less than the third preset voltage threshold, and at least one of the following conditions is detected: the state of charge of the fifth energy battery is less than a third preset charge threshold, the state of charge of the sixth energy battery is less than the third preset charge threshold, the voltage value of the fifth energy battery is less than a third preset voltage threshold, and the voltage value of the sixth energy battery is less than the third preset voltage threshold, the first switch tube and the third switch tube are controlled to be disconnected, or the second switch tube and the fourth switch tube connected to the three-level frequency converter for power consumption are controlled to be disconnected; and the first DC / DC converter and the second DC / DC converter are controlled to enter a charging state, and the ninth switch tube and the tenth switch tube are controlled to be closed to perform over-discharge protection on the fifth power battery, the sixth power battery, the fifth energy battery, and the sixth energy battery. If at least one of the following conditions is detected: the state of charge of the fifth power battery is greater than a fourth preset charge threshold, the state of charge of the sixth power battery is greater than the fourth preset charge threshold, the voltage value of the fifth power battery is greater than a fourth preset voltage threshold, the voltage value of the sixth power battery is greater than the fourth preset voltage threshold, the state of charge of the fifth energy battery is greater than a fourth preset charge threshold, the state of charge of the sixth energy battery is greater than the fourth preset charge threshold, the voltage value of the fifth energy battery is greater than a fourth preset voltage threshold, and the voltage value of the sixth energy battery is greater than the fourth preset voltage threshold, the second switch tube and the fourth switch tube connected to the three-level frequency converter for power generation are controlled to be disconnected, the first switch tube and the third switch tube are controlled to be closed, the first DC / DC converter and the second DC / DC converter are controlled to enter a discharging state, and the ninth switch tube and the tenth switch tube are controlled to be closed to perform over-charge protection on the corresponding batteries. If the energy regeneration device corresponding to the three-level frequency converter is in a maintenance state, the second switch tube and the fourth switch tube connected to the corresponding three-level frequency converter are controlled to be disconnected.

9. The three-level charge-pump control circuit of claim 2, wherein, The first energy storage unit includes a seventh power battery, a third DC / DC converter, a seventh energy battery, and a fifth DC / DC converter; and the second energy storage unit includes an eighth power battery, a fourth DC / DC converter, an eighth energy battery, and a sixth DC / DC converter. The first end of the seventh power type battery is connected with the first end of the third DC / DC converter, the second end of the seventh power type battery is connected with the second end of the third DC / DC converter, the first end of the eighth power type battery is connected with the first end of the fourth DC / DC converter, the second end of the eighth power type battery is connected with the second end of the fourth DC / DC converter, the first end of the seventh energy type battery is connected with the first end of the fifth DC / DC converter, the second end of the seventh energy type battery is connected with the second end of the fifth DC / DC converter, the first end of the eighth energy type battery is connected with the first end of the sixth DC / DC converter, the second end of the eighth energy type battery is connected with the second end of the sixth DC / DC converter, the third end of the third DC / DC converter and the third end of the fifth DC / DC converter are connected with the first end of the first energy storage unit, the third end of the fourth DC / DC converter and the third end of the sixth DC / DC converter are connected with the second end of the second energy storage unit, the fourth end of the third DC / DC converter, the fourth end of the fourth DC / DC converter, the fourth end of the fifth DC / DC converter and the fourth end of the sixth DC / DC converter are connected with the second end of the first energy storage unit, and the controlled end of the third DC / DC converter, the controlled end of the fourth DC / DC converter, the controlled end of the fifth DC / DC converter and the controlled end of the sixth DC / DC converter are connected with the energy control unit respectively.

10. The three-level charge-pump control circuit of claim 9, wherein, If it is detected that the state of charge of the seventh power type battery and the eighth power type battery are both less than a first preset state of charge threshold, or the voltage values of the seventh power type battery and the eighth power type battery are both less than a first preset voltage threshold, and the charging current values of the first end of the first energy storage unit and the second end of the second energy storage unit are both greater than a preset charging current value, the first switch tube, n second switch tubes, a third switch tube and n fourth switch tubes are controlled to be closed, and the third DC / DC converter and the fourth DC / DC converter are controlled to enter a charging state, so as to charge the seventh power type battery and the eighth power type battery; If it is detected that the state of charge of the seventh power battery is not less than the first preset state of charge threshold, the state of charge of the eighth power battery is not less than the first preset state of charge threshold, the voltage value of the seventh power battery is not less than the first preset voltage threshold, the voltage value of the eighth power battery is not less than the first preset voltage threshold, and the state of charge of the seventh energy battery and the eighth energy battery is less than the first preset state of charge threshold, or the voltage value of the seventh energy battery and the eighth energy battery is less than the first preset voltage threshold, and the charging current value of the first end of the first energy storage unit and the charging current value of the second end of the second energy storage unit are greater than the preset charging current value, the first switch tube, the n second switch tubes, the third switch tube and the n fourth switch tubes are controlled to be closed, and the fifth DC / DC converter and the sixth DC / DC converter are controlled to enter the charging state to charge the seventh energy battery and the eighth energy battery. If it is detected that the state of charge of the seventh power battery and the eighth power battery is greater than the second preset state of charge threshold, or the voltage value of the seventh power battery and the eighth power battery is greater than the second preset voltage threshold, and the discharge current value of the first end of the first energy storage unit and the discharge current value of the second end of the second energy storage unit are greater than the preset discharge current value, the first switch tube, the n second switch tubes, the third switch tube and the n fourth switch tubes are controlled to be closed, and the third DC / DC converter and the fourth DC / DC converter are controlled to enter the discharging state to discharge the seventh power battery and the eighth power battery. If it is detected that the state of charge of the seventh power battery is not greater than the second preset state of charge threshold, the state of charge of the eighth power battery is not greater than the second preset state of charge threshold, the voltage value of the seventh power battery is not greater than the first preset voltage threshold, the voltage value of the eighth power battery is not greater than the first preset voltage threshold, and the state of charge of the seventh energy battery and the eighth energy battery is greater than the second preset state of charge threshold, or the voltage value of the seventh energy battery and the eighth energy battery is greater than the second preset voltage threshold, and the discharge current value of the first end of the first energy storage unit and the discharge current value of the second end of the second energy storage unit are greater than the preset discharge current value, the first switch tube, the n second switch tubes, the third switch tube and the n fourth switch tubes are controlled to be closed, and the fifth DC / DC converter and the sixth DC / DC converter are controlled to enter the discharging state to discharge the seventh energy battery and the eighth energy battery. If at least one of the following conditions is detected: the state of charge of the seventh power battery is less than a third preset state of charge threshold, the state of charge of the eighth power battery is less than the third preset state of charge threshold, the voltage of the seventh power battery is less than a third preset voltage threshold, and the voltage of the eighth power battery is less than the third preset voltage threshold, and the state of charge of the seventh energy battery and the eighth energy battery is not less than the third preset state of charge threshold, or the voltage of the seventh power battery and the eighth power battery is not less than the third preset voltage threshold, the third DC / DC converter and the fourth DC / DC converter are controlled to enter a charging state, and the fifth DC / DC converter and the sixth DC / DC converter are controlled to enter a discharging state, so as to perform over-discharge protection on the seventh power battery and the eighth power battery; If at least one of the following conditions is detected: the state of charge of the seventh energy battery is less than a third preset state of charge threshold, the state of charge of the eighth energy battery is less than the third preset state of charge threshold, the voltage of the seventh energy battery is less than a third preset voltage threshold, and the voltage of the eighth energy battery is less than the third preset voltage threshold, and the state of charge of the seventh power battery and the eighth power battery is not less than the third preset state of charge threshold, or the voltage of the seventh power battery and the eighth power battery is not less than the third preset voltage threshold, the first switch tube and the third switch tube are controlled to be turned off, and the fifth DC / DC converter and the sixth DC / DC converter are controlled to enter a charging state, so as to perform over-discharge protection on the seventh energy battery and the eighth energy battery; If at least one of the following conditions is detected: the state of charge of the seventh power battery is less than a third preset state of charge threshold, the state of charge of the eighth power battery is less than the third preset state of charge threshold, the voltage of the seventh power battery is less than a third preset voltage threshold, and the voltage of the eighth power battery is less than the third preset voltage threshold, and at least one of the following conditions is detected: the state of charge of the seventh energy battery is less than a third preset state of charge threshold, the state of charge of the eighth energy battery is less than the third preset state of charge threshold, the voltage of the seventh energy battery is less than a third preset voltage threshold, and the voltage of the eighth energy battery is less than the third preset voltage threshold, the first switch tube and the third switch tube are controlled to be turned off, or the second switch tube and the fourth switch tube connected to the three-level frequency converter for use are controlled to be turned off; and the third DC / DC converter and the fourth DC / DC converter are controlled to enter a charging state, and the fifth DC / DC converter and the sixth DC / DC converter are controlled to enter a charging state, so as to perform over-discharge protection on the seventh power battery, the eighth power battery, the seventh energy battery, and the eighth energy battery; If at least one of the following conditions is detected: the state of charge of the seventh power battery is greater than a fourth preset charge threshold, the state of charge of the eighth power battery is greater than the fourth preset charge threshold, the voltage value of the seventh power battery is greater than a fourth preset voltage threshold, the voltage value of the eighth power battery is greater than the fourth preset voltage threshold, the state of charge of the seventh energy battery is greater than a fourth preset charge threshold, the state of charge of the eighth energy battery is greater than the fourth preset charge threshold, the voltage value of the seventh energy battery is greater than a fourth preset voltage threshold, and the voltage value of the eighth energy battery is greater than the fourth preset voltage threshold, the second switch tube and the fourth switch tube connected to the three-level frequency converter corresponding to the power generation are controlled to be disconnected, the first switch tube and the third switch tube are controlled to be closed, the third DC / DC converter and the fourth DC / DC converter are controlled to enter a discharging state, and the fifth DC / DC converter and the sixth DC / DC converter are controlled to enter a discharging state, so as to perform overcharge protection on the seventh power battery, the eighth power battery, the seventh energy battery and the eighth energy battery. If the energy regeneration device corresponding to the three-level frequency converter is in a maintenance state, the second switch tube and the fourth switch tube connected to the corresponding three-level frequency converter are controlled to be disconnected.

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