Distribution network characterization for ancillary service provision : frequency response through voltage control

The rising share of distributed generation (DG) in the power system results in reduced inertia and larger frequency deviations following power imbalance. Balancing efforts of transmission system will require increasing coordination of distribution networks. This paper analyses impact of different characteristics of Low Voltage (LV) networks on its power consumption when varying voltage at point of common coupling in order to support frequency containment of transmission system. Frequency support is delivered by adapting the LV grid voltage to shape power consumption of voltage-dependant loads. It enables the use of voltage as a trigger for active power control of 1 voltage-dependant loads without the need for additional communication and frequency measurement. The Smart Transformer allows a fast control of voltage amplitude, and consequently, power consumption of LV grid without affecting medium voltage grid. Different network characteristics were analysed to determine networks most suitable for providing frequency support through voltage control

Dynamically robust coordinated set point tracking of distributed DERs at point of common coupling

Low-inertia operation of small-scale power systems, such as a microgrid or a portion of a long feeder, requires careful coordination of the controller performance of the constituting devices. This challenge is exacerbated in microgrids serving the functionalities of a conventional synchronous-based generation unit while comprised of smaller DERs operating mainly interfaced through power electronics converters. This paper builds on the idea of set point modulation and proposes a two-level control strategy that aims to achieve superior performance at the point of common coupling (PCC) of microgrids by combining a local control level with a distributed and coordinated level. Several case studies on both AC and DC systems, the CIGRE low-voltage benchmark system as the AC system and a test DC microgrid, validate the performance of the proposed approach. The real-world applicability of the approach is established via a high-fidelity power hardware-in-the-loop (PHIL) experimental setup and an application case study on grid frequency regulation. The proposed approach enables a microgrid to participate in ancillary service provisions where speed and quality of regulation are critical