A new smart grid system is widely used for energy supply system because it is simple, available, low cost, high efficiency and environmentally friendly. Conventionally, inverter techniques are utilised to convert input DC into output AC with the same frequency and phase. This process suffers the same problem which is a higher harmonic distortion, phase synchronisation, lower quality of waveform and long distance, among others. In this paper, three phase synchronous inverters (PSI) were used to direct synchronous PWM control, LCL filter, three phase RLC load, three phase Yg-Delta transformer, 5 km feeder with 2 MW load. PWM was used to generate the pulse signal for synchronisation. However, LCL filters were used to remove the noise in inverter output and transformer output side of the design. A balanced three phase load (10 kVAR) and also the input DC voltage 500 V were considered in this design. Three phase transformer (100kVA/260V/25kV) was used to increase the inverter output voltage and current with the fundamental frequency (50 Hz). The system conversion efficiency was 99.96% and phase synchronous error for each phase was approximately 4.5 degrees.
In recent years, the utility grid system is more essential for the power
transmission and distribution system because it cannot produce harmful
gases or no discharge waste in the environment. PWM based phase
synchronous invert systems are generally utilised in the high efficiency
energy supply, long distance and higher power quality. The inverter output
voltage depends on the coupling transformer, input sources and invert
controllers. An inverter using a three leg IGBT has been designed for utility
grid and simulated by using MATLAB2014a. In this paper, both sides of
the LCL filters are used for removing the DC ripple current, reducing the
noise and synchronous the output phase between inverter and the utility
grid. The PWM controller has created pulse signal to control the inverter,
electronic switches and precisely synchronise with grid line frequency. In
this system, the input DC voltage 500V, switching frequency 1.65 kHz, grid
frequency 50Hz, 20 km feeder (resistance, inductance and capacitance per
unit length, which are 0.1153, 1.05e-3 and 11.33e-09 ohms/km) with 30MW
three phase load (active and inductive reactive power which are 30e6 W
and 2e6 var) and also a balanced utility grid load of star configuration (00,
1200, and 2400 degree) are considered in the design. On the other hand,
three phase transformer consists of three signal phase transformers, normal
power 100e3, magnetization resistance and inductance which are 500 pu and
416.67pu are considered in this design. The system conversion efficiency
is 99.94% and 99.96%, while the total THD are 0.06% on inverter side
and 0.04% on grid side.