Indirect current control of BTB-VSC with cage-rotor induction generator operating in grid connected and isolated mode

Abstract

The paper proposes current control scheme for back-to-back voltage source converter (BTB-VSC) to regulate small capacity turbines run cage-rotor induction generator (CRIG) for small capacity power generation. The CRIG is connected to a local grid and supported by a BTB-VSC which regulates bidirectional power flow through a d.c. link. The CRIG is capable to feed partial load connected at the local grid in grid connected mode. In case of isolation, the connected load on local grid is scheduled to match the power rating of CRIG. Frequency at CRIG terminal is regulated by supplying/drawing real power to/from the local grid, whereas voltage is regulated by dynamically compensating reactive power demanded by the load. The scheme thus enforces the drawl of only the rated real power component of current from the CRIG terminals. The proposed scheme is current controlled and thus have better response, simple, easily implementable and requires lesser hardware. Implementation of the proposed scheme done through simulation in Matlab/Power System Blockset and the effectiveness of the system is gauged through simulation results.