Feasibility Study on Variable Renewable Energy Output Fluctuation Compensation by Use of Power Control of Variable Speed Waterworks Pumps

Abstract

Okinawa has many islands, and the installation of photovoltaics (PVs) is accelerating. This paper focuses on the compensation of power fluctuation in PVs by the use of variable speed control of waterworks pumps for weak island grids. A simple model of a waterworks pump system is proposed to calculate power consumption, water flow and pressure from the power converter input frequency, and the efficacy of the model is verified by field tests. The model is based on hydraulics, and its constants fit the test results. Ramp response tests and PV power fluctuation compensation tests are conducted to evaluate the transient characteristics of power consumption control. The ramp response test results show that power consumption differs from its command value by a few seconds because of the pressure surge caused by the pipes. The latter tests show that control of power consumption compensates for most of the PV power fluctuation under the test conditions.