*Article* **Flywheel Energy Storage and Dump Load to Control the Active Power Excess in a Wind Diesel Power System**

#### **Rafael Sebastián 1,\* and Rafael Peña-Alzola 2**


Received: 9 March 2020; Accepted: 13 April 2020; Published: 18 April 2020

**Abstract:** Wind Diesel Power Systems (WDPS) are isolated microgrids which combine Wind Turbine Generators (WTGs) with Diesel Generators (DGs). The WDPS modelled in this article is composed of a DG, a WTG, consumer load, Dump Load (DL) and a Flywheel Energy Storage System (FESS). In the Wind-Diesel (WD) mode both the DG and WTG supply power to the consumers. The WDPS is simulated in the WD mode in the case that the WTG produced power exceeds the load consumption. This WTG excess power case is simulated in the subcases of DL and FESS turned <sup>o</sup>ff, only-DL and only-FESS. Simulations for the DL and FESS-off case show that the WTG excess power leads to a continuous system frequency increase, so that the tripping of the WTG Circuit Breaker (CB) is required to guarantee the WDPS power supply continuity. Simulations for the only-DL/only-FESS cases show that commanding the DL/FESS to consume controlled power, so that the required DG power to balance the system active power is positive, enables the DE speed governor to regulate the system frequency. Furthermore, the frequency and voltage variations in the DL/FESS cases are moderate and there is no need to trip the WTG-CB, so that the WDPS reliability and power quality are greatly improved. Additionally, the only-FESS case obtains better WDPS relative stability than the only-DL case.

**Keywords:** diesel generator; wind turbine generator; isolated microgrid; flywheel energy storage; dump load; power systems simulation; power systems control
