面向电流源型PWM整流器直流侧电压的多环路控制策略

A Multiple Loops Control Strategy Based on DC Link Voltage of Current Source PWM Rectifiers

三相电流源型PWM整流器作为低压直流配电系统有源前端时,因网侧LC滤波环节和直流侧电容的存在使系统控制难度增加。首先,在同步旋转坐标系下建立电压定向数学模型,通过控制网侧电流d轴与q轴分量,完成系统有功、无功功率的独立控制;其次,基于相量法提出一种电容电流补偿方法,仅构建电容电压前馈通道,实现间接电流控制策略下功率因数校正;然后,采用电容电压反馈有源阻尼法对网侧LC谐振进行抑制,详细分析反馈增益对系统稳定性的影响;此外,该文通过在内环引入直流侧电感电流反馈以及阻尼因子,进一步改善系统性能;之后,利用频域法与根轨迹法对整个控制环路进行分析,辅助Matlab/SISO设计工具,在离散域中直接优化设计控制器零点位置与环路增益;最后,通过仿真和实验结果验证了所提出方法的可行性和有效性。

When the three-phase current source PWM rectifier is employed as the active front-end in low-voltage DC distribution systems, the difficulty and complexity of the control system increase due to the existence of input LC filter and DC bus capacitor. Firstly, a voltage-oriented mathematical model is established in the synchronous rotating reference frame. A compensation scheme of capacitance current based on phasor method is proposed, which guarantees that only by capacitor-voltage feedforward path the input power factor can be kept at unity. Secondly, as an alternative damping method, the capacitor-voltage feedback is used to suppress the LC resonance, and the influence of the feedback gains on the stability of the system is discussed. Furthermore, the system’s dynamic performance is further improved by adopting DC-side inductor-current feedback and damping factor. The active power and reactive power of the system are controlled independently by d-axis and q-axis components of the grid side current. The control loops are analyzed using the frequency-response method and the root locus analysis, and supported with Matlab/SISOTOOL, the zero position and loop gains of the controllers are straightforward designed in the z-domain. Finally, the simulation and experimental results verify the feasibility and effectiveness of the proposed method.