不平衡电网下主动支撑型三相PWM变流器控制方法

Control Method for Active Support Three-phase PWM Converter in Unbalanced Power Grid

三相脉冲宽度调制(pulse width modulation,PWM)变流器在高性能电力终端上得到广泛应用,但受限于三相阻抗不匹配造成的电网不平衡问题,现有PWM变流器无法兼顾直流电压波动和网侧电流品质两大控制目标。为此,提出一种不平衡电网下主动支撑型PWM变流器控制方法。首先对不平衡电网下PWM变流器进行数学建模,论证在不增设辅助电路情况下直流母线电压波动和网侧电流品质间的控制矛盾性问题。在此基础上,通过在直流侧增设功率调节电路,实现交、直流侧的解耦控制,并进一步对所提方法的线性运行区域进行分析,给出了电网不平衡度与最小电容配置关系。最后,基于35kW测试样机进行测试与分析,论证了所提方法在不平衡电网下的适用性和优越性。

Three-phase pulse width modulation(PwM)converters are widely used in high-performance power terminals,but limited to the power grid imbalance caused by three-phase impedance mismatch,therefore,the existing PWM converters cannot take into account the two control objectives of DC voltage fluctuation and the grid-side current quality.For this purpose,a control method of active support type PWM converter under unbalanced power grid was proposed.Firstly,the mathematical model of PWM converter in unbalanced power grid was established to demonstrate the control contradiction between DC bus voltage fluctuation and grid side current quality without additional auxiliary circuits.On this basis,the decoupling control of AC and DC sides was realized by adding a power regulation circuit on the DC side.The linear operation region of the proposed method was further analyzed,and the relationship between power grid imbalance and minimum capacitance configuration was given.Finally,based on test and analysis of the 35 kW test prototype,the applicability and superiority of the proposed method in unbalanced power grid are demonstrated.