Effective active power control of a high penetration wind diesel system with a Ni–Cd battery energy storage

High penetration (HP) Wind Diesel Hybrid Systems (WDHS) have three modes of operation: Diesel Only (DO), Wind Diesel (WD) and Wind Only (WO). The HP-WDHS presented in this article consists of a Wind Turbine Generator (WTG), a Diesel Generator (DG), the consumer Load, a Ni–Cd Battery based Energy Storage System (BESS), a discrete Dump Load (DL) and a Distributed Control System (DCS). The DG includes a friction clutch which allows the Diesel Engine (DE) to be engaged (DO and WD modes)/disengaged (WO mode) to the Synchronous Machine (SM). The DCS consists of a sensor node which measures the SM speed and active power, calculates the reference active power PREF necessary to balance the active power in the WDHS and communicates this PREF value through a message to the BESS and DL actuator nodes. In the WD mode both the DG and WTG supply active power to the system and the DE speed governor regulates the system frequency. However in an HP-WDHS the power produced by the WTG (PT) can be greater than the one consumed by the load (PL). This situation means a negative power in the DG (power inversion) with its speed governor unable to regulate frequency. To avoid this situation, the DCS must order coordinated power consumption to the BESS and DL in order to keep the DG produced power positive. In this article it is shown by simulation how the DCS manages both a temporary power inversion and a permanent one with the mandatory transition from WD to WO mode. The presented graphs for frequency, voltage, active powers of the system elements and battery voltage/current show the effectiveness of the designed control.