一种检测单相瞬时无功与谐波电流的新方法

New Method for Detecting Instantaneous Reactive and Harmonic Currents in Single-phase Systems

有源滤波器作为改善电能质量一种有效的手段，它要求快速准确地检测出负载电流中的谐波和无功分量。针对单相系统瞬时谐波与无功检测方法算法复杂的问题，提出了一种新的检测方法，并详细分析了低通滤波器的选取，低通滤波器的阶数越高，截止频率越低，检测算法的稳态精度越高，暂态性能越差。该法能实时准确地检测出负载电流中的基波有功分量，进而实现谐波与无功电流的瞬时补偿。仿真研究表明该法简单可靠，电路实现容易，且不需要锁相环，克服了系统频率漂移的影响，在2-3个周期内实现了补偿电流的准确提取，有效解决了单相系统中谐波和无功电流检测中存在的问题。

In the control strategies for an active power filter （APF）, the determination of harmonic and reactive components of the load current is the most important stage. And no perfect approaches have been brought forward so far for single-phase nonlinear loads such as electric traction loads. In this paper, a new method based on the orthogonality of sine is proposed in order to detect the harmonic and reactive currents in single-phase power systems, and it can detect the fundamental active currents and then compensate harmonic and reactive currents in the load currents accurately. Simulation studies illustrate the proposed method can provide the required signals for APF to perform compensation within a transient period of 2 to 3 cycles and the steady error is negligible, and it can realize real-time detection accurately. It is not necessary to adopt the phase lock loop （PLL） in it, and it overcomes the influence of the frequency fluctuation. It is simple and reliable and its hardware implementation is easy. The selection of low pass filter （LPF） is discussed in detail, it is concluded that the higher the LPF order is, the lower the cut-off frequency is, the better the steady accuracy becomes and the slower the rapidity of dynamic response becomes.