Development of Photovoltaic Interactive Inverter Using Immittance Converter in High-Frequency Link

新开发的光伏公用互动逆变器额定功率为3kW。在逆变器中，采用了一种新设计的Transformer集成T-LCL型导抗变换器，工作频率为19 kHz。在60Hz时，不加反馈控制，可得到畸变率为3%的正弦电流，且受电网电压幅值和波形畸变的影响很小。当电网电压阶跃变化时，正弦电流的波形和幅值不变，暂态振荡在0.1毫秒内消失。光伏互动逆变器的整体效率超过90%。对5种谐振导抗变换器的频率特性、电压电流传输特性、效率特性等基本特性进行了分析。当负载阻抗等于特性阻抗时，所有类型的导抗转换器具有最大效率。在LCL型导抗变换器中，当电抗器的Q值为100时，最大效率为98%。实验中，LCL型导抗变换器的最大效率达到98.6%，混合型导抗变换器的最大效率达到99.4%。谐振频率与电源频率的偏差允许在± 5%以内。非接触能量传输系统供电载波中的受电端是导抗变换器的一种有效应用。在该系统中，接收端的高频恒流通过导抗变换器变换为恒压，再经整流，得到直流恒压。导抗变换器的输出的整流技术对于光伏公用交互式逆变器是常见的。

Newly developed photovoltaic utility interactive inverter is 3kW rated power. In the inverter, there is a transformer integrated T-LCL type immittance converter newly designed in insulated high frequency link which worked at 19kHz. At 60Hz, a sinusoidal current of 3% distortion factor is obtained without the feed back control, and is little affected by the amplitude and the wave form distortion of the utility voltage. Waveform and amplitude of the sinusoidal current don't change, when the utility voltage changes stepwise, and the transient oscillation disappears in 0.1 millisecond. The overall efficiency of the photovoltaic interactive inverter is over 90%.Basic characteristics such as frequency characteristics, voltage-current transfer characteristics, efficiency characteristics were clarified on resonant immittance converter of 5 types. The immittance converter of all types has maximum efficiency when the load impedance is equal to the characteristic impedance. The maximum efficiency is 98%, if the Q of the reactor is 100 in the LCL type immittance converter. In experiments, the 98.6% maximum efficiency has been obtained using the LCL type immittance converter, and 99.4% maximum efficiency has been obtained using the hybrid type immittance converter. It became clear that the deviation of the resonant frequency and source frequency could be permitted ± 5%.The power receiving end in the carrier supplied power by a Non-Contact Energy Transfer System is one of the useful application of the immittance converter. In the system, the high frequency constant current at the receiving end is converted into a constant voltage by the immittance converter, then it is rectified, and a DC constant voltage is obtained. The rectifying technology of the output of the immittance converter is common to the photovoltaic utility interactive inverter.