Control of inverter-based distributed generation in low-inertia power systems

Driven by the need to reduce greenhouse gas emissions, improve air quality and address climate change, the penetration of renewables into the electrical network has risen over the years. Unlike traditional synchronous generators, most renewables are connected to the power network through power converters. Control strategies have been designed to allow their integration into the network and adapt them to the well-known and well-established control and stability rules of the traditional synchronous generators. Due to the different types of power converters, their flexibility and the high number of manufacturers, the controllers designed for each power converter can be very different to each other.

Although integration of converters by adapting them to the rules of the synchronous machines has been effective so far in maintaining the stability of the system, renewable generation could threaten the network stability and security of supply as its proportion increases. Besides, since the penetration of renewables is expected to keep increasing, it could lead to a power system with few or even no synchronous generators. This project will study the stability and will attempt to find new control design rules for power converters in electrical networks with power electronics mainly/only. The project is, therefore, aligned with EPSRC's Energy Networks research area within the Energy theme.

The work will begin by reviewing previous stability analyses conducted on power converter controllers. Then, a somewhat simplified electrical network with different proportions of power provided through power converters will be simulated with various control strategies. The interaction of power converters with each other when controlled with different strategies will be analytically studied. From the simulations and theoretical analyses, some control design rules will be enumerated that could improve the overall stability if applied to all power converters. A down-scaled experimental prototype converter could be built in a power-hardware-in-the-loop arrangement to verify simulation results.