基于Z源逆变器的光伏并网功率调节系统

PHOTOVOLTAIC GRID-CONNECTED POWER CONDITIONER BASED ON Z-SOURCE INVERTER

将具有升压特性的Z源逆变器应用到光伏并网功率调节系统中,减少了传统用于升压控制的DC/DC变换环节。在控制技术方面,针对Z源电容电压升压比和直通占空比的非线性问题,提出一种线性控制方法来实现对Z源电容电压的控制,以满足系统直流侧的稳定要求。此外,将经最大功率控制器调节后得到的光伏有功电流分量嵌入到谐波检测回路,产生了包含有光伏并网电流和用于补偿的无功、谐波、基波负序电流的参考指令信号。通过仿真和实验验证,该系统在很好地实现光伏并网发电的同时,不仅可在三相电网电压对称、不对称或畸变的情况下,对电网电流电能质量问题进行治理,还可对三相不对称电路进行无功、谐波及基波负序电流的有效补偿。

A Z-source inverter with boost capability was applied in photovoltaic （PV） grid-connected power condi- tioner, instead of traditional DC/DC booster. In the aspect of control technology, regarding the non-linear problems between boost ratio of Z-source capacitor＇ s voltage and shoot-through ratio, a linear control method was put forward to solve it for the purpose of keeping DC link constant. In addition, the PV active power from maximum power point tracking （MPPT） controller is embedded into the harmonics detecting loop so as to produce reference currents which contain PV active power for grid-connection and reactive power, harmonic and fundamental negative se- quence currents for compensation, The verifications through simulation and experiment demonstrate that the pro- posed system can implement, at same time PV grid-connected generation. Meanwhile it can improve the power quality of grid currents when in three-phase grid of balance or unbalance or distortion. Furthermore, reactive pow- er, harmonic currents and fundamental negative sequence currents can be compensated effectively even in three- phase unbalanced circuit.