Abstract: A grid connection control method of an energy storage apparatus, an energy storage control unit, an energy storage system, and a storage medium are provided and relate to the field of energy storage technologies, where the method includes: sequentially controlling energy storage units of energy storage sub-modules to be connected to corresponding voltage-sharing capacitors in a state in which a main energy transmission circuit is disconnected from a direct-current bus, so as to make the energy storage units pre-charge the corresponding voltage-sharing capacitors; and controlling the main energy transmission circuit to be connected to the direct-current bus under a condition that the voltage-sharing capacitor of each energy storage sub-module meets a voltage-sharing capacitor pre-charge completion condition.

Abstract: Provided are an energy storage system and a control system and a control method of the energy storage system. The energy storage system includes a converter valve and an energy storage valve, the energy storage valve is connected to a direct-current side of the converter valve, and the control system includes: a coordination control subsystem, a converter valve control subsystem, and an energy storage valve control subsystem; the coordination control subsystem is used for sending an instruction to control the converter valve control subsystem and the energy storage valve control subsystem to work; the converter valve control subsystem is used for controlling, according to the instruction of the coordination control subsystem, the converter valve to work; and the energy storage valve control subsystem is used for controlling, according to the instruction of the coordination control subsystem, the energy storage valve to work.

Abstract: A starting method of an energy storage system is provided. The energy storage system includes at least one energy storage submodule. The energy storage submodule includes a power module and a battery module. The starting method includes: acquiring a first instruction; and controlling the battery module to charge the power module according to the first instruction. Through the starting method, the battery module of the energy storage submodule can be controlled to charge the power module when a power grid is in a completely black state so that the power module can be charged to have the power-on capability, thereby realizing the self-starting of the energy storage submodule and helping to increase the restoration speed of the power grid.

Abstract: A control method of an energy storage system. The energy storage system includes N energy storage modules connected in series, and N is a positive integer greater than 1. The control method includes: acquiring a first parameter of each energy storage module among the N energy storage modules, the first parameter being a parameter related to the power; and conducting balance control on the energy storage system according to the first parameter of each energy storage module.

Abstract: A control method of an energy storage system. The energy storage system includes a plurality of energy storage modules connected in series. The control method includes: acquiring a difference value between a first state parameter of a first energy storage module and a first state parameter of a second energy storage module among N available energy storage modules in the energy storage system, N being a positive integer greater than 1; and conducting balance control on the energy storage system according to the difference value of the first state parameters.

Abstract: Provided are a method for suppressing direct current oscillation in a power transmission system and the power transmission system. The power transmission system comprises a sending terminal VSC, a receiving terminal VSC and a direct current energy storage apparatus, wherein the direct current energy storage apparatus is connected in parallel between the sending terminal VSC and the receiving terminal VSC, and the direct current energy storage apparatus comprises a plurality of energy storage submodules. The method comprises acquiring a direct current power oscillation amount of the power transmission system; and controlling, according to the direct current power oscillation amount, the number of the direct current energy storage apparatuses connected to the energy storage submodules of the power transmission system.

Abstract: Provided are a control method for an energy storage system and the energy storage system. The energy storage system includes N energy storage sub-modules, where N is a positive integer greater than 1. The control method for the energy storage system includes: acquiring an SOC and a charge-discharge limiting current of each of the N energy storage sub-modules; and controlling working states of the N energy storage sub-modules according to the SOC and the charge-discharge limiting current of each of the energy storage sub-modules, where the working states include a switched-on state and a switched-off state. According to the technical solution provided by embodiments of this application, the problem of SOC imbalance among the energy storage sub-modules can be solved, so that the utilization rate of the energy storage system is improved.