COMPARATIVE ANALYSIS of NOVEL PHASE DELAY TIME ADJUSTMENT METHOD and EQUAL PHASE DELAY TIME DEVELOPMENT METHOD on the THD REDUCTION of TPVMI SYSTEM

Multilevel inverters have been developed by various topologies, one of the topologies is cascaded full bridge inverter that generates multilevel output voltage waveform. However, it needs a lot of numbers of switching component and pulse wave generator. It also has high total harmonic distortion (THD) still. It is due to the multilevel inverter has no pure sinusoidal output voltage waveform. A method to reduce the number of pulse wave generator and also to adjust the voltage level on the multilevel inverter is very important to be considered to achieve the lowest THD and fulfil the condition of good power quality. This paper presents a transformerless photovoltaic multilevel inverter (TPVMI). Kaneka G-SA060 amorphous silicon (a-Si) PV module as main direct current (DC) source is modelled by SIMULINK MATLAB. The model results of photovoltaic (PV) module performance are validated using the statistical analysis, they are root mean squared error (RMSE), coefficient of residual mass (CRM), percentage error (e) and Nash-Sutcliffe equation (NSE). A novel phase delay time adjustment method and equal phase delay time development method are proposed on the TPVMI system to achieve the lowest THD. 7-level output voltage waveform of the TPVMI is generated as an output of three cascaded inverters. The inverters are constructed by four switching components (four MOSFETs), but only two types of pulse wave generator to drive the gate terminals of MOSFET. Thus, these methods have advantage to reduce the number of pulse wave generator compared to the existing methods. The results show that the PV module performances (short circuit current and open circuit voltage) are valid to the data sheet of PV module based on the statistical analysis. The THD of 20.76 % generated by the novel adjustment method of phase delay time is lower than the THD of 40.92 % generated by the equal phase delay time development method. It indicates that the novel adjustment method of phase delay time has a better performance compared to the equal phase delay time development method.