An Enhanced DC-Link Voltage Control Method for High-speed PMSM/G in Flywheel Energy Storage System with Indirect Feedforward of Consumed Power and Speed Compensation

This paper is focused on DC-side capacitor's energy feedback control method for digitally-controlled flywheel energy storage system (FESS). DC-link voltage in FESS under discharge mode is prone to continuously decrease of rotational velocity, change of DC-side load, existence of power dissipated by the machine, etc. Straight feedforward of aforementioned consumed power results in undesired cost for sensing DC-side load and it's difficult to directly observe dissipative power of the motor. Indirect calculation is thus suggested. However, regular digital implementation methodologies of differentiator for indirect feedforward usually amplify the noise of measured signals. Flywheel speed compensation and indirect feedforward of consumed power using tracking-differentiator with inherent filtering property is then devised. Simulation traces validate the superiority of the proposed discharge strategy.