Control system of an AC/DC single-phase stage included in a single-phase distributed generation system

With the high consumption of electrical energy and its associated polluting effects, mainly caused by the use of fossil resources such as oil, gas or coal, the problem of finding alternative solutions has become a serious one to solve. On the other hand, fossil fuel resources are dwindling, while global demand for electrical energy continues to rise as a result of major industrial development. This has led to a rise in the price of fossil fuels, particularly oil, on the international market. Fossil fuel scarcity, cost and atmospheric pollution are the major limitations and constraints to meeting the growing consumption of electrical energy. Renewable energies (such as solar radiation, wind, etc.) have been gaining in interest in recent years, and have naturally come to the fore, thanks to their environmental-friendliness, growing efficiency and lower costs.

In the past, the reinforcement of power generation was achieved by integrating new, centralized, high-power generation units into the grid. Nowadays, the trend is towards the use of a large number of power generators, close to the point of consumption, with lower power levels and based on renewable energies . This new trend in power generation is known by various names, such as distributed power generation, dispersed power generation, decentralized generation or distributed generation.

Recent research shows the technical difficulty of controlling distributed energy generations, since several elements interact with each other for this type of application, such as energy sources, power converters, energy storage systems, loads and the grid. Since the majority of renewable energy sources generate non-sinusoidal voltages, it is necessary to use an electrical energy conversion stage (DC/DC or AC/DC) to obtain a DC voltage and a DC/AC converter to convert it into a sinusoidal voltage with controlled amplitude and frequency. The voltage generated can be connected directly to the grid or used for isolated operation. In this article, we will focus on the development of a DC/AC stage control included in a single-phase distributed generation system operating in isolated mode. The main aim is to correct system losses and disturbances so that the output voltage delivered is a sinusoidal voltage of fixed amplitude and frequency, whatever the variation in the load it feeds. To this end, the structure and modeling of the DC/AC stage of a single-phase distributed generation operating in isolated mode are presented first. The sizing of an LC filter used to extract the fundamental...