数字移相法测量无功功率的一种改进方法

An Improved Method for Reactive Power Measurement based on Digital Phase Shift

无功功率测量在电力系统中具有非常重要的作用。针对传统数字移相法测量无功功率存在的不足,提出了一种改进方法,该方法首先构造一个FIR数字滤波器,同时根据当前频率计算将电压移相1/4周期需要平移的采样点数以及需要补偿的角度,然后通过构造的滤波器对经过采样点平移的电压进行移相,使电压准确移相90毅,接着将移相后的电压采样值和电流采样点值进行点积计算瞬时功率,最后通过求该瞬时功率的周期平均值计算无功功率。本方法中FIR数字滤波器的参数预先做成表格,实际补偿时可通过查表获取相关参数,因而算法的实时性高,易于程序实现。实际应用结果表明,改进方法测量无功功率的效果明显优于传统数字移相法,且不受输入信号频率变化的影响。

The reactive power measurement plays an important role in an electric power system.According to disadvantages of the traditional digital phase shift method in reactive power measurement,an improved method has been proposed,comprising the following steps:first,construct an FIR digital filter,and according to the current frequency,calculate the number of sampling point to be moved horizontally and the angle to be compensated as required during phase shift of voltage for 1/4 cycle;then,for the voltage of which sampling points have been moved horizontally,use the filter constructed for accurate 90° phase shift;afterwards,obtain the dot product of sampled voltage and current after phase shift,to calculate instantaneous power;finally,calculate the average cycle of the instantaneous power to obtain reactive power.In the method,since parameters of the FIR digital filter are tabled in advance,related parameters can be inquired in the table during actual compensation,so the algorithm is advantaged by high real-time performance and easy program implementation.Actual application results indicate that the improved method for reactive power measurement has an obviously better effect than the traditional digital phase shift method,and will not be affected by frequency changes of input signals.