Design and development of a phase synchronous inverter for microgrid system based on electrostatic generator

Abstract

The demand for energy sources of the world is exponentially increasing, which is in turn giving rise to a threatening insufficiency of fossil fuels and gases to be used as energy sources. Beyond this traditional and momentary solution to the energy crisis, the renewable energy-driven electrostatic generators provide the scope of a long-term solution. However, the electrostatic generator (ESG) with renewable energy should convert to supply AC for microgrid, but an inversion of the high voltage static DC has suffered many problems, such as inferior quality of waveform, stabilization of the input voltage, high switching loss due to phase synchronize and power quality as well as high unexpected voltage. Furthermore, an electrostatic generator produces high voltage DC and low current which is milliamperes (mA). Therefore, to overcome those issues, a new zero-crossing based voltage source phase synchronous inverter (PSI) circuit has been proposed in the microgrid system, which especially makes the AC waveform, free from higher harmonic distortion, low switching loss, and increased efficiency. A zero-crossing pulse width signal is generated to precisely synchronize with a microgrid line frequency that is done by switching and logic networks. A zero-crossing circuit is utilized to detect the phase with frequency, to make a zero-crossing signal and synchronize the phase angle between inverter and microgrid system. In this study, the unique inverter switching parameters are optimized, such as input source voltage of 10k𝑉𝐷𝐶, the duty cycle of 95%, switching frequency 2kHz and a microgrid load of 1000Ω, whereas the other parameters are considered. In addition, an LCL lowpass filter is used to couple between inverter and microgrid system, to convert square wave to pure sinusoidal wave and to reduce the higher harmonic distortion. Both the new proposed design and existing design are simulated by MatLab16.a/Simulink, Or CAD Capture 16.6, Proteus 8 professional and Keysight BenchVue. From this analysis, without the filtering condition and with the filtering condition of total harmonic distortion (THD) is 47.9% to 2.1%, which is approximately a 45% reduction in the higher harmonic distortion. The phase analysis showed that the error of an inverter side phase angle and microgrid side phase angle are 26.34° and 2.54°, respectively. The theoretical, simulated and experimental results have shown that the newly designed inverter has performed better in terms of the overall system conversion efficiency of 96.6%, the phase angle of 2.54, and THD of about 2.1%. The proposed PSI is appropriate for microgrid applications that could contribute to the economic improvement of the country and globally as a whole.