三电平双向直流变换器的模型预测电压控制研究

Research on Model Predictive Control of Voltage of Three-level Bi-directional DC-DC Converter

三电平双向直流变换器以其传输效率高和输出波形畸变率小等优点在储能系统等低压大电流场合得到了广泛应用。但由于其输出电平数量的增多,调制复杂度增加,可能在应用中出现中点不平衡问题。针对以上问题,提出模型预测电压控制MPC(model predictive control)方法,实施直流母线电压和输出侧分压电容均压的多目标优化控制。该方法通过预测模型的构建和目标函数的寻优两个步骤实现对三电平双向直流变换器的控制,在提高直流母线电压调节的精度和响应速度的同时抑制中性点电压波动。最后,将所提控制策略应用于储能系统并通过Matlab/Simulink进行仿真,结果验证了该算法在直流电压跟踪和中点电压平衡控制中的有效性。

Owing to its advantages such as a high transmission efficiency and small output waveform distortion,the three-level bi-directional DC-DC converter has been widely applied to energy storage systems and other low-voltage and high-current scenarios.However,due to the increase in the number of output levels and the growing modulation complexity,the problem of neutral-point voltage imbalance may occur in its applications.To solve this problem,a model predictive control(MPC)method is proposed to implement the multi-objective optimization control of the voltage of DC bus and that of the voltage-dividing capacitor on the output side.This method realizes the control of the three-level bi-directional DC-DC converter in two steps,i.e.,the construction of a prediction model and the optimization of the objective function.As a result,the accuracy and response speed of DC bus voltage regulation are improved while restraining the neutral-point voltage fluctuations.Finally,the proposed strategy is applied to an energy-storage system,and simulations are carried out using Matlab/Simulink.Results validate the effectiveness of the proposed algorithm in the tracking of DC bus voltage and the control of neutral-point voltage balance.