CAJ | 학술논문

针对LCL型并网逆变器的谐振问题,该文从离散控制的角度分析了谐振机理,得出控制器运算时间带来的滞后影响了系统相频特性,使其不满足奈奎斯特稳定判据而失稳.虚拟电阻法是解决LCL谐振问题的一种有效而稳定的方法,但在工业应用中存在电容电流欠采样导致的混叠问题.选择合理的滤波器可以解决混叠问题,但其带来的相位滞后影响了阻尼效果甚至为系统带来负阻尼,针对这一问题该文提出了带超前补偿的虚拟电阻有源阻尼法.另外,实际系统通常是多台逆变器经LCL并联,系统存在从单机谐振频率到多机谐振频率宽频率范围的谐振,该文基于1.5 MW逆变器试验平台,通过改变并联滤波电容组数进行了谐振频率670~1 230 Hz的阻尼实验.实验结果证明了所提方法的有效性,以及对宽频率范围的适应性.
침대LCL형병망역변기적해진문제,해문종리산공제적각도분석료해진궤리,득출공제기운산시간대래적체후영향료계통상빈특성,사기불만족내규사특은정판거이실은.허의전조법시해결LCL해진문제적일충유효이은정적방법,단재공업응용중존재전용전류흠채양도치적혼첩문제.선택합리적려파기가이해결혼첩문제,단기대래적상위체후영향료조니효과심지위계통대래부조니,침대저일문제해문제출료대초전보상적허의전조유원조니법.령외,실제계통통상시다태역변기경LCL병련,계통존재종단궤해진빈솔도다궤해진빈솔관빈솔범위적해진,해문기우1.5 MW역변기시험평태,통과개변병련려파전용조수진행료해진빈솔670~1 230 Hz적조니실험.실험결과증명료소제방법적유효성,이급대관빈솔범위적괄응성.
For the resonance problem of the grid-connected inverter with LCL filters, this paper analyzes the resonance mechanism from the perspective of discrete-time control for the first time. It shows that the controller's computing delay impacts the system's phase-frequency characteristics, which leads to the break of the Nyquist's stability criterion. The virtual resistor method is an effective and stable way to solve the LCL's resonance problem, but in industrial applications there would be aliasing caused by the under-sampling of the capacitor currents. Choosing an appropriate filter can solve the aliasing problem, but it brings the phase lag which affects the damping effect and even introduces the negative damping to the system. To solve the above-mentioned problem, this paper presents an active damping method with lead compensation. Moreover, as it usually consists of several inverters connected in parallel via LCL, the actual system has a wide resonance frequency range from single-invertor resonance frequency to multi-invertor resonance frequency. In this paper, the damping experiments of the resonance frequency from 670 Hz to 1 230 Hz are carried out, by changing the group number of the parallel filter capacitors based on a 1.5 MW inverter platform. Experimental results demonstrate the effectiveness of the proposed method, as well as the adaptability for a wide range of resonance frequency.