基于Lagrange插值频率估计的数字电能计量算法

传统电能计量系统中电网电压/电流波形信号的采集由电子式电能表完成,电能表内部设计了频率跟踪电路,在电网频率出现波动的情况下能同步采样,电能计量误差小。在数字电能计量系统中电网波形的采集由电子式互感器或合并单元的A/D采样模块完成,由于电子式互感器或合并单元采集后到的电网波形信号需要组帧传输给后续不同的数字化设备使用,其采用固定的采样频率,所以,在电网频率出现波动的情况下,不能实时跟踪电网频率而改变采样频率实现同步采样,电能计量误差大,因此,为减小在频率波动条件下的电能计量误差,提出一种数字电能计量新算法,该方法利用三次拉格朗日(Lagrange)插值算法提取出电网基波频率,并利用离散傅里叶变换(DFT)算法的栅栏效应进行波形成分提取,实现电能计算,该方法实现简单,通过实验仿真验证了其电能计量误差小,具有实用价值。

Digital power metering algorithm based on Lagrange interpolation frequency estimation

In traditional electric energy metering system,the signal acquisition of the power grid voltage and current waveform is finished by electronic energy meter,the meter designs frequency tracking circuit,and the synchronous sampling can be achieved under the condition of the power grid waveform frequency fluctuation,and electricity measurement error is small.In digital power metering system,the sampling of power grid waveform is done by A/D module which has a fixed sampling frequency of electronic transformer or merging unit,and it can't achieve the real-time tracking grid frequency synchronous sampling,and electricity measurement error is bigger under the condition of frequency fluctuation,therefore,in order to reduce the error of electricity energy metering,this paper proposes a new algorithm of digital power metering,the method extracts the fundamental frequency of the power grid by using the Lagrange interpolation algorithm,and extracts the waveform component by using the fence effect of discrete Fourier transform algorithm,which realizes the energy calculation.This method is simple,and the experimental simulation verifies its electricity measurement error is small,and has a practical value.