3. Results
A mini-grid with a genset feeding a network with 20 houses in a single phase connection where only two of the three outputs of the genset are used is presented in [3] and is used in this paper to evaluate the impact of the frequency x temperature droop control in the loading of the generator and grid frequency. The genset is rated at 95kW on a three phase basis, however in practice it means that only about 2/3 of the generator power is available. The droop parameter of the genset are sp = 29.4 kW/Hz and fnl = 62.3 Hz.
A residential load profile for a house without EWH based on [10] was scaled to have a daily energy consumption of 20 kWh and used as reference for all 20 houses to determine the 24 h load profile of the mini-grid. Fig. 3 (a) presents the single house load profile used and the power consumption profile of the EWH with Td = 120 °F. The Wd schedule considered was the one presented in Fig. 1 (b). Two cases are considered, first the EWH operates with constant Td, base case, and the second one using the frequency x temperature droop strategy (Tdroop) with m = 20 °F/Hz and fc = 61 Hz. Fig. 3 (b) presents the genset load for each hour of the day. The load variation is reduced with the droop approach. The peak load from this day decreases from 56 kW to 52 kW, while in the lower load region, the load increases from 8.3 kW to 9.5 kW. This small difference in the low load region is due to the fact that varying Td for controlling the power is sensitive to the water profile that during that period was low. Fig. 4 presents the frequency variation regarding the change in the genset load (a) and the variation on Td due to the frequency droop implemented.