交流电参数的卷积窗加权测量及其单片机实现

Convolution window weighted measurement for AC parameters and its MCU implementation

分析了交流电电压、电流以及功率等均值参数的采样法测量理论,给出了不引入测量误差的条件。分析了非同步采样导致交流电参数测量误差的原因以及采用窗函数加权抑制测量误差的机理。重点给出了非同步频偏很小时抑制误差最有效的矩形互卷积窗及误差公式。针对实际中模数转换(ADC)电路的输入信号中存在直流分量,导出了适用于单片机直接实现交流电参数测量的卷积窗加权算法的系列公式。通过仿真实验测试了单片机执行卷积窗加权算法的机器周期数与时长。结果表明采用STM32单片机仅需利用采样周期的很小一部分时间即可完成2阶卷积窗加权算法交流电参数测量中1个采样点的计算,算法具有很高的时效性。

The theory of a sampling method for measuring the average parameters of AC voltage, current and power is analyzed, and a condition without introducing measurement error is given. The reasons for measurement error of AC parameters caused by non-synchronous sampling and the mechanism of window function weighted method to suppress measurement error are analyzed. Rectangular convolution windows, which are most effective in suppressing errors in the case of very small non-synchronous frequency deviation, and measurement error formulae are presented. Considering the DC component in the input signal of ADC circuit in practice, a series of formulae corresponding to the convolution window weighted algorithm for AC parameter measurement are derived. These are suitable for direct implementation by an MCU. The number of machine cycles and the length of time for the MCU to execute the convolution window weighted algorithm are tested by simulation. The results show that the convolution window weighted algorithm is time efficient. The calculation of one sampling point in the AC parameter measurement of 2-order convolution window weighted algorithm can be completed using a STM32 MCU in only a small part of the sampling period.