电容中点式三相四线制SAPF混合无源非线性控制策略

电容中点式三相四线制并联型有源滤波器(SAPF)相比于三相三线制SAPF,附加了零序电流通路,因而可在电网平衡/不平衡时补偿非线性负荷产生的各次谐波、零序及无功电流。利用SAPF的无源性对其进行非线性的无源控制(PBC)可取得较常规的线性和非线性控制器更好的补偿效果,且在电网不平衡时无需检测和处理谐波电流的正负序分量。文中提出了一种电容中点式三相四线制SAPF的混合无源控制策略。首先,根据被控对象SAPF在dq0坐标系下的EulerLagrange数学模型分析其无源性,并计算得到了能使被控量收敛至期望值的SAPF内环电流无源控制规律;然后,采用阻尼注入法对其进行简化,得到能使内环补偿电流完全解耦的新的无源控制规律,提高系统的动态性能;接着,根据直流侧总电压和差压与补偿电流存在紧密联系,设计了基于2阶低通滤波器控制的SAPF外环电压控制器;最后,通过Simulink软件仿真和实验验证了将文中混合PBC用于SAPF控制的可行性和优越性,相比于传统的比例—积分控制,所提出的控制方法有更快的响应速度和更好的补偿效果。

Nonlinear Control Strategy of Three-phase Four-wire Shunt Active Power Filter with Mid-point Capacitor Based on Hybrid Passive Theory

The three-phase four-wire shunt active power filter(SAPF)with mid-point capacitor can be used to compensate for all harmonics, zero sequence and reactive current of the nonlinear load no matter whether the power system is balanced or unbalanced because of the additional path for zero sequence current compared to three-phase three-wire SAPF. Control of SAPF via the nonlinear passive controller by using its passivity can yield a better compensating effect than the conventional linear and nonlinear controller. And there is no need of detection and treatment of the positive and negative sequence components of all harmonics when the power system is unbalanced. A hybrid passivity-based control(PBC)strategy of mid-point capacitor three-phase four-wire SAPF is proposed. Firstly, according to the Euler-Lagrange mathematical model of the controlled object in the dq0 coordinate system, the passivity of the SAPF is analyzed, and the passive control law of the inner-loop current of SAPF able to make the controlled quantity converge to the expected value is obtained. Secondly, the damping injection method is used to simplify the design of the system, and the new passive control law capable of completely decoupling the compensation current of the inner-loop is obtained as an improvement on the dynamic performance of the system. Thirdly, the outer-loop voltage controller of SAPF based on the 2-order low-pass filter is designed according to the close relation between the total and differential voltage at the DC side and compensating current. Finally, the feasibility and superiority of applying hybrid PBC to SAPF is verified by Simulink software simulation and experiment. Compared with the traditional PI control, the control method proposed in this paper has a faster response speed and better compensation effect.