Study of a power line conditioner aiming at compensation for unidentified harmonics in distribution systems

作者提出了一种新的电力线调节器组成的两个小额定值串联有源滤波器和并联无源滤波器。电力线调节器是一种通用的滤波系统，它将安装在电力系统的公共耦合点，馈电谐波敏感负载和未识别的谐波产生负载。两个有源滤波器中的一个使用电压源PWM逆变器与电源串联，而另一个与并联无源滤波器串联。本文设计的无源滤波器由11阶和13阶调谐LC滤波器和一个高通滤波器组成，其目的是减小接入点的电压畸变，消除接入点上游进入系统的谐波电流。换句话说，电力线调节器能够补偿电源电流和母线电压的谐波，从而使连接在公共母线上的谐波产生负载和谐波敏感负载之间不发生谐波干扰。讨论了它的滤波特性，重点是电压和电流失真。一个假设的20 kVA的配电系统，它馈给谐波敏感的负载，并确定和身份不明的谐波产生负载的构造，以验证电力线调节器的功能和性能。结果，获得了良好的滤波特性，从而导致电力线调节器的实际使用。指出谐波检测与计算电路的精度对公共母线电压的谐波抑制有很大影响。

The authors propose a new power line conditioner consisting of two small rating series active filters and a shunt passive filter. The power line conditioner aims at a general filtering system which will be installed at the point of common coupling in a power system feeding harmonic-sensitive loads and unindentified harmonic-producing loads. One of the two active filters using voltage-source PWM inverters is connected in series with the supply, while another is in series with the shunt passive filter. The specially desgned passive filter in this research consits of 11th and 13th tuned LC filters and a high pass filter.The prupose of the power line conditioner is to reduce voltage distortion at the connection point, and is to eliminate harmonic curents escaping into the system upstream of the connection point. In other words, the power line conditioner is capable of compensating for harmonics of supply currents and bus voltages, so that no harmonic interference occurs between harmonic-producing loard and harmonic-sensiteive loads which are connected on the common bus.A control scheme of the two series active filters which play and important role is described. Its filtering characteristics are discussed with the focus on voltate and current distortion. An hypothetical distribution system of 20kVA which feeds a harmonic-sensitive load, and identified and unidentified harmonic-producing loads is constructed to verify the functionality and performance of the power line conditioner. As a result, good filtering characteristics are obtained, thus leading to practical use of the power line conditioner. It is pointed out that the accuracy of the harmonic sensing and calculating circuit greatly affects harmonic reduction of the common bus voltage.