A Novel Strategy for Ramp Rate Control of Wind Farms

Interconnection of wind power plants to the grid has inherent adverse effects on power system stability due to the intermittent nature of availability. The injected power comprises of ramps with fast rising and falling that are detrimental to small power systems owing to their smaller inertia. This paper proposes a power electronic based ramp controller that can successfully arrest fast ramps having rates outside set limits unique to the power system they operate in. The system consists of a battery energy storage, a bidirectional DC-DC converter, three-phase Voltage Source Inverter (VSI) and a power-frequency three-phase transformer. Both converters are operated with current control Pulse Width Modulation (PWM) for fast response. The system is simulated with real time data obtained from an existing wind farm in Mannar, Sri Lanka, and the results show successful arresting of fast ramps with minimum of battery storage. Design details, hardware system, control philosophy, control algorithm, operation and simulation are presented. Simulation results are presented and discussed.