Power Electronic Devices in Modern Power Systems

There are two main trends in present development of power systems. First is a wide utilization of renewable power resources. The second is decentralization of power generation. Hence, small power sources, very often RES sources, called dissipated power generators are developed. They are usually in range of megawatts starting form kilowatts. They operate automatically and are remotely controlled. In fact the sources are electronic devices. Microprocessor control units are used to control power production and perform remote control and power electronic converters are used to control power flow. So, many different kinds of power electronic devices are required. Another political and social trend is local balancing of power production and power consumption. It means that all power consumed in some are should be generated in the area. Hence small power systems are developed called microgrids. Microgrids consist of power sources, loads, control units and lines, like normal public grid. But the microgrid is limited to the small area, i.e. village, town, and automatically controlled. Again power electronic devices and control units decide about the microgrid performances. Development of required devices, both power electronic and controllers, are possible only with close cooperation of research units, like Warsaw University of Technology, and production firms, like APS Energia. APS Energia offers many power electronic converters and complete power plant and control and supervisory remote controllers for power industry. Some are especially developed for dissipated generation. The University's researchers design some devices and their principles of operation. APS Energia produces the devices. The main, presented in the paper are inverter with MPP tracking for PV systems, inverters for supplying AC loads from DC power systems, PEM fuel cell power generation units, battery chargers, high power inverters and rectifiers with sinusoidal input current, synchronization systems and remote control and monitoring devices. There are some examples of applications in the paper.