New generation system concept: Motor-assisted gas turbine with pulse width modulation interleaving motor drive

This paper introduces a new concept of power generation system called the motor-assisted gas turbine (MAGT). In the MAGT, a dual-shaft gas turbine and a motor drive are included. The conventional dual-shaft gas turbine has two shafts with different rotational speeds: a power turbine shaft and a compressor shaft. The power turbine shaft is connected to a generator and is rotated at a certain speed with respect to the grid frequency. The new idea of the MAGT is that a motor drive assists the torque of the compressor shaft. The MAGT can be used as an energy storage device, like a flywheel, by using the converter to operate the compressor at variable speeds. This paper also describes a new motor drive that reduces harmonics current in the DC-link of the frequency converter.

1 Introduction

The more renewable energy sources are used for electric power generation, the more power fluctuations will occur in electric power grids due to their variable nature. To avoid those fluctuations, thermal power plants with fast-ramping capability are also required in addition to energy storage systems. Among thermal power plants, the gas turbine (GT) generator is one of the best candidates due to its fast-ramping capability and low CO₂ emissions, especially when used in a combined cycle.