Microcontroller Based Novel Dc-to-Ac Grid Connected Inverter Topology

The conventional line commutated ac-to-dc converters/ inverters have square-shaped line current which contains higher-order harmonics. Moreover, it requires a costly and bulky dc inductor or choke. The line current with the high harmonic contents generates EMI and therefore it causes more heating of the core of distribution or power transformers. Alternatively, PWM based inverters using MOSFET/IGBT switches can be used for the above purpose. However, apart from higher switching losses, the power handling capability and reliability of these devices are quite low in comparison to thyristors/ SCR. A thyristor based forced commutated inverters are not suitable for PWM applications due to the problems of commutation circuits. A pure sinusoidal voltage output or waveform with low harmonic contents is most desirable in the conversion from dc to ac. In the present work, a novel two pulse line commutated inverter is been proposed with control signal generated from PIC 16F 877A. It improves the wave shape hence it reduces the total harmonic distortion (THD) of the grid interactive-inverter. The simulation of the circuit is done using SIMULINK. Moreover, the performance of the proposed circuitry is far better than the conventional line-commutated inverter. It reduces THD, number of thyristors and dispenses with the bulky dc inductor/ choke. A prototype model is developed for discontinuous line current mode. The results are also compared with the simulation results in SIMULINK/ MATLAB.