Protection challenges in future converter dominated power systems

Converter interfaces, used to connect renewable energy sources, HVDC links and infeeds to the power system, will bring significant changes to the behaviour of power systems in the future, particularly in Great Britain (GB). Existing network protection schemes (both at transmission and distribution levels) may be seriously affected by the changed system behaviour during and after faults. Therefore it is necessary to establish how and when the protection schemes may start to malfunction under future scenarios in a “converter-dominated” environment. In this paper, a Voltage Source Converter (VSC) model, with an appropriate and flexible controller, which is capable of regulating output voltages and currents in response to faults on the supplied AC power system, will be introduced. A set of tests of protection performance in a power system with varying degrees of converter penetration and fault responses are presented, and the results of tests are presented and analysed. In the tests presented, adjustments to the converter controller parameter are made, resulting in a range of converter outputs during faults (e.g. with different reaction delays and current magnitudes). The potential impact that these responses may have on protection performance are outlined, and on-going and future work to fully evaluate the performance of transmission protection under a range of future system scenarios are described