In filter based reactive power measurements, the voltage is phase shifted by \(90^\circ\) relative to the current. This paper presents a technique of measuring reactive power based on differential \(90^\circ\) shifter. According to this method, the sampled voltage and the current signal passes through a pair of FIR filters that shifts \(+\,45^\circ\) and \(-\,45^\circ\). Then, the two outputs are multiplied to measure the reactive power. A pair of FIR filters that are having identical flat magnitude responses and orthogonal phase responses are designed. Multiplier-less FIR structure is adopted for hardware implementation to reduce the chip area cost making the technique implementable in digital power meter. A detailed hardware architecture and its implementation in FPGA is presented. Furthermore, the measurement of reactive power for various frequencies between 50 and 250 Hz is also presented.

在基于滤波器的无功功率测量中，电压相对于电流相移\(90^\circ\)。本文提出了一种基于差分\(90^\circ\)移位器的无功功率测量技术。根据这种方法，采样电压和电流信号通过一对 FIR 滤波器，该滤波器将\(+\,45^\circ\)和\(-\,45^\circ\). 然后，将两个输出相乘以测量无功功率。设计了一对具有相同平坦幅度响应和正交相位响应的 FIR 滤波器。硬件实现采用无乘法器FIR结构，降低芯片面积成本，使该技术可在数字功率计中实现。介绍了详细的硬件架构及其在 FPGA 中的实现。此外，还介绍了 50 到 250 Hz 之间各种频率的无功功率测量。