Grid Integration of PV System Using Synchronverter

All the power generators need to synchronize themselves with the grid before connection. The conventional method for frequency and phase matching is by using phase locked loops (PLL). But PLL being a nonlinear, complex device suffers several disadvantages. Solar photovoltaic (SPV) system converts solar energy directly into electrical energy. The output of SPV system depends on irradiance and temperature, due to which output power varies throughout the day. This continuous variation in power makes it difficult for the PLL to match the frequency with the grid. As the PV systems are static and hence lack inertia when there is an increased demand in load side. This may create problem of frequency instability when the penetration of renewable generating system is high. Hence, some external storage devices, such as batteries, are used to minimize these power fluctuations. The external storage devices add the installation as well as recurring cost of the generating system. Synchronverter is a 3 phase voltage source inverter (VSI), along with DC source, which mimics the behavior of Synchronous generator. A grid connected solar PV system using synchronverter, along with perturb and observe MPPT algorithm is designed and simulated in MATLAB software. The results show that the system is able to synchronize itself with grid without using PLL, both in standalone and grid connected mode. Also characteristics of synchronous generator such as frequency droop and voltage droop are exactly followed by our system. All the existing control strategies in power grid, which were earlier used to control synchronous generators, can be used to control the proposed SPV generator.