Keywords: dispersed generation, grid-connected, microturbines, induction generators, diode rectifier-PWM inverters, distributed generation, simulation
A new microturbine-based dispersed generation scheme
Almost all of the commercial microturbine-based dispersed generation systems today are composed of a high-speed permanent-magnet alternator and a diode rectifier-PWM inverter pair. A dispersed generation scheme made up of a microturbine, an induction generator, and a diode rectifier-PWM inverter pair is introduced in this paper. A complete model for the self-excited squirrel-cage induction generator is developed and used to study the steady-state and transient behaviours of the overall system. The power delivered to the grid is controlled by an injected current control loop. The input/output power balance is maintained by regulating the DC-bus voltage using a new method based on the torque control of microturbine. Analysis shows that the Simulink simulation results of induction generator is a viable substitute for permanent magnet alternator in microturbine-based dispersed generation systems due to its low cost, low maintenance, rugged structure, and slack between rotor speed and terminal frequency, which isolates the transients of the grid from the generator system when the DC-bus capacitor size is reduced. Both schemes have been simulated and the simulation results are presented to compare the proposed scheme based on induction generator with the present microturbine-based dispersed generation scheme based on synchronous machine.