基于提升小波变换的光伏谐振检测方法

Photovoltaic Resonance Detection Method Based on Lifting Wavelet Transform

光伏发电并网系统中多台并网逆变器之间、逆变器与电网之间的交互耦合会引起系统串、并联谐波谐振,严重地影响了电网电能质量,因此光伏发电并网产生的谐振问题亟待研究。针对这一问题,首先建立光伏发电并网系统谐振模型,分析了光伏并网运行时产生的谐振问题。谐振不同于谐波之处在于谐波表现为电流和电压波形产生周期性畸变,而谐振导致的电流和电压畸变是非周期性的。分析了提升小波变换在谐振检测上的应用原理,在此基础上提出基于提升小波变换算法的谐振检测技术,并利用FFT进一步筛选谐振可能所在的频带,得到光伏发电并网谐振的起止时刻以及频带范围。最后通过仿真验证该方法能够有效地检测光伏发电并网系统的谐振问题。

In grid-connected PV power generation system, the interaction coupling between multiple parallel inverters, the inverter and the grid will cause series and parallel harmonic resonance of the system. It has seriously affected the power quality of the grid. Therefore, the resonance problem of the grid-connected PV power generation was urgent to be studied. To solve this problem, firstly, the resonant model of grid-connected PV power generation system was established. The resonance problem of grid-connected PV power generation was analyzed. The resonance performance was different from the harmonic performance. The harmonic caused the current and the voltage wave form to produce the periodic distortion, but the resonance caused the current and the voltage to produce the non-periodic distortion. The application principle of lift wavelet transform （LWT） in resonance detection was also analyzed. On the basis of this, put forward a detection technique of resonance based on LWT. Use FVI＂ to further filter the frequency band in which resonance might be located. The start and stop time and frequency band of grid-connected PV power generation was obtained. Finally, the simulation results showed that the method proposed could effectively detect the resonance problem of grid-connected PV power generation system.