基于CIC抽取滤波器的电力系统谐波分析算法及DSP实现

【作者】 张波；

【导师】 曹建；

【作者基本信息】 中南大学 ， 电路与系统， 2009， 硕士

【摘要】 随着电力电子技术和国民经济的发展,电网中的谐波污染越来越严重,同时,用户对电能质量也提出了更高的要求。电力谐波问题正在引起越来越多人的关注。而对谐波的监督和抑制,有赖于对电力谐波准确可靠的分析和计量。本文首先在介绍快速傅立叶变换算法的同时,深入分析了快速傅立叶变换应用于谐波分析时存在的频谱泄漏现象和栅栏效应问题。然后,通过对非同步采样的分析和目前存在的算法的研究,提出了基于CIC(Cascaded Integrator Comb,级联积分梳状)抽取滤波器的谐波分析算法。该算法在前端AD过采样的情况下,先对过采样序列进行整周期截断,再对截断后的序列进行CIC抽取滤波,实现了对过采样序列进行降采样处理,又不引起频域混叠。降采样后的数据经过FFT运算单元,从而计算出各次谐波的幅值、频率、相位等参数的值。在算法研究过程中,提出了对过采样序列分段匹配的整周期截断方法,对抽取前后序列点数不确定的信号抽取提出了动态选择抽取因子的有效方法。算法的硬件实现上采用了DSP+MCU的主从式双CPU设计,主机MCU选用STC89C54RD+,作为系统主机,主要实现三个功能:1)控制并与从机DSP通信。2)人机接口的控制,包括液晶显示和键盘输入。3)与PC进行命令和数据的通信。从机DSP选用TI公司的芯片TMS320VC5402,主要实现对电流电压信号的采集、信号的CIC抽取滤波处理以及FFT运算等功能。采集的模拟电路部分设计了多通道电流和电压信号的检测调理电路以及高速模数转换电路。在硬件系统的基础上,在软件设计上,着力遵循模块化设计原则,设计了系统各个模块的软件流程和软件功能,对涉及算法核心的部分,如整周期截断方法、抽取因子的计算等做了详细研究,设计软件流程图并给出了相关部分软件代码。通过对本文提出的算法和部分硬件设计进行仿真验证和数据分析,证明了基于CIC抽取滤波器的谐波分析算法是有效可行的,且具有较高的分析精度。更多还原

【Abstract】 With the development of science and technology and economies, the harmonic pollution of power system is getting more and more serious, while more and more qualified electrical power is required. In order to minitor and contol the harmonic pollution, precise harmonic analysis and measurement are seriously needed.In the paper, firstly, while producing the FFT(Fast Fourier Transform) algorithm, the problems spectrum leakage and fence effect caused by it when applied to harmonic analysis are deeply analysed. Secondly, by research in asynchronous sampling and existing harmonic analysis algorithms, a CIC(Cascaded Integrator Comb) decimation filter based harmonic algorithm is propsed. In the case of ADC over-sampling, the signal is truncated to a single cycle, then CIC decimation filtered. Therefore, the sampling frequency is reduced without aliasing. After FFT unit, the amplitude, frequency, and phase of harmonics are obtained. In the process of studying the proposed algorithm, two good methods are presented. One is integral cycles truncation method using segment matching. The other is the method that decimating factor is calculated dynamically when it is not an integer.In the hardware design of the proposed algorithm, a dual-CPU structure DSP+MCU is applied, with MCU as host and DSP as slave. STC89C54RD+, selected for MCU as the host CPU in the system, is mainly used for three functions: 1) Control and communicate with DSP slave. 2) Human-Computer Interface, including LCD display and keyboard input. 3) Communicate with the PC, so that commands and data can flow between MCU and PC. TI’s DSP chip TMS320VC5402 is applied, the functions of which mainly inlude collecting voltage and current data of power system signals, processing the data with the proposed algorithm and related calculations. In the analog circuit for data collection, detection and ajusting circuits and high speed A/D circuits for multiple channels voltage and current signals are designed. The software of the system, well following the modulation principle, in which software flows and fuctions of the main modules are designed, and among which, modules related with the core algorithm, such as the integral cycles trunction method and the method of the calculation of decimation factor, are specially studied, and software flow chart and part of the code are listed.Through software verification and data analysis of circuits and the proposed algorithm, the CIC decimation filter based harmonic analysis algorithm is proved to be effective and of good analysis precision.更多还原