Cascaded energy storage device and control method based on llc soft-switching resonant circuit

Abstract

The invention relates to energy storage technology, in particular to a cascaded energy storage device based on an LLC soft-switching resonant circuit and a control method, including n battery packs, n one-to-three LLC soft-switching resonant converters, and H-bridge cascaded Three-phase inverter and three-phase AC filter; each battery pack is connected to the input end of a pair of three LLC soft-switching resonant converters, and the three output ends of each pair of three LLC soft-switching resonant converters are respectively connected to The DC input terminal of an H bridge of each phase of an H bridge cascaded three-phase inverter, the AC output terminals of n H bridges of each phase of the three-phase inverter are connected in series in sequence, and connected to the Public power grid; n is a positive integer. The device utilizes the one-to-three LLC resonant conversion circuit structure and the phase symmetric distribution of the DC ripple of the three-phase H-bridge to realize ripple cancellation at the output end of the energy storage battery, avoiding the current ripple directly injected into the battery, reducing The battery heats up, prolonging battery life.

Description

technical field [0001] The invention belongs to the technical field of energy storage, and in particular relates to a cascaded energy storage device and a control method based on an LLC soft-switching resonant circuit. Background technique [0002] At present, the relatively mature energy storage system in the market uses lithium iron phosphate batteries and lead-acid batteries to form energy storage components, and its DC terminal is connected to the AC grid through a DC-AC converter. In order to meet the capacity and power requirements, batteries used in energy storage systems are usually composed of dozens or hundreds of battery cells connected in series and parallel to form a battery pack. Due to the individual differences between the cells, there are inconsistent states of the cells during operation, and if the performance of individual cells decreases, it will lead to a decrease in the performance of the entire battery pack, that is, the so-called short board will appe...

AI Technical Summary

Problems solved by technology

Although the current H-bridge cascade topology can significantly reduce the overall capacity drop and low capacity utilization caused by the short board effect of the battery pack in use, there are still the following problems:

However, these control methods can only alleviate, but cannot completely solve the impact of ripple current on the battery

[0006] (3) In the common H-bridge cascaded energy storage system, due to the difference in parameters such as energy storage battery capacity, the voltage on the DC side of each H-bridge is different. After the phase-shifted carrier modulation method, it will lead to more harmonics on the AC output side. Poor power quality problem

Moreover, the conventional control method for H-bridge cascaded energy storage systems is to control the DC voltage balance of each H-bridge or the power balance of the battery, which is not suitable for the actual operation requirements of the battery charge state management of the battery energy storage system. Limited improvement in plate effect

[0007] Generally speaking, the existing energy storage power generation system structure has the problems of low battery efficiency and low power quality caused by the short board effect. Through the improvement of the structure and control method of the cascaded converter, this contradiction can be solved. Some relief, but there is still the problem that the current ripple has a great influence on the battery capacity, and the system control method is complicated

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