Design and Control of a Linear Electric Machine Based Gravity Energy Storage System

In this paper the design of a 130 kW linear electric machine for use in dry gravity storage system is presented. The linear electric machine makes use of a hybrid permanent magnet vernier machine with consequent poles. The linear machine is optimally designed for a 100 m high shaft for primary response application, raising and lowering a piston of 50 tons. A speed and current control system is designed for the speed control of the piston and to determine the response time from command to full power of the piston system. The results show that the proposed hybrid permanent magnet vernier machine is well suited for primary response application. A response time of 2 seconds is found for the system, which makes it ideal for grid frequency stability.