Three-phase multi-level converter and battery SOC balance control method thereof

Abstract

The invention discloses a three-phase multi-level converter and a battery SOC balance control method thereof. A star-shaped cascade H-bridge inverter is introduced into an energy storage system, an SOC sequence of each module battery in each phase is obtained through comparison, a function vector is selected according to the sequence, and the function vector and each module switch function are adjusted, so that an SOC of each battery in each phase gradually tends to be balanced; then an inter-phase SOC is also balanced through a negative sequence signal injection method based on SOC differencevalue feedback; and finally, a five-module eleven-level three-phase star-shaped cascaded H-bridge inverter simulation model is built, and the correctness and feasibility of a proposed algorithm are verified through a simulation result. The three-phase multi-level converter and the battery SOC balance control method thereof are easy to implement and high in reliability.

Description

technical field [0001] The invention relates to a three-phase multilevel converter and a battery SOC balance control method thereof. Background technique [0002] In the battery energy storage system, in order to increase the system capacity, the battery modules are usually directly connected in series and parallel, and then output through a single-stage DC / AC or two-stage DC / DC+DC / AC, but it is easy to generate Problems such as unbalanced charging and discharging currents and circulating currents affect the stability of the entire system, and the use of two-level topology will increase the complexity of control and reduce system reliability. Therefore, some scholars have proposed to adopt star cascaded H-bridge topology, and the battery energy storage unit adopts a distributed configuration and is connected to the DC side of the H-bridge unit. The advantages of this topology are: the number of H-bridges in series can be increased to achieve a high output voltage level, eff...

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Problems solved by technology

Some articles propose to use triangular carrier stacked PWM (SB-SPWM) to achieve the SOC balance of each battery, but under the carrier stacked modulation strategy, the switching frequency is high, the switching loss is large, and the analysis of the output voltage is difficult, and the number of carriers varies with the number of H-bridges. The number grows and grows, not suitable for the environment with more levels

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