Study on Re-Energization Capability of a Hybrid Windfarm under a
Microgrid-based Restoration Strategy
Abstract
Under a microgrid based (bottom-up) restoration strategy, considering a
disaster related outage, the local generation is required to energize
and supply the unaffected part of the network. Considering 100%
renewable generation, only hydro based generation systems, if well
equipped, can be able to blackstart and re-energize the network. Wind
Energy Conversion Systems (WECSs) have been restricted to the latter
stages of restoration due to their source intermittency and
non-dispatchability and in order for them to participate in the initial
restoration stages, voltage and frequency support auxiliary devices are
required. This paper investigates the capability of a hybrid windfarm to
participate in the initial stages of restoration similar to a
conventional blackstart unit: Re-energization of the various network
components and pick up of load. The auxiliary equipment in this case is
a dump load to absorb excess power produced by the windfarm and a
synchronous condenser to provide a stable voltage reference required for
normal operation of the WECS. Firstly, the nominal range of operation is
determined with an additional pitch control mode linking the dump load
power to individual WECSs introduced for frequency control. Flicker and
harmonics are investigated in determination of the hosting capacity.
Studies are undertaken to investigate energization of transformers,
underground cables, overhead lines and other non-blackstart units
(including other WECSs). Consideration is given to Type 1 and Type 3
WECSs to investigate the capability of a non-inverter and inverter based
WECS. MATLAB/Simulink has been used as the simulation platform due to
its modelling flexibility.