M. Ahsanul Alam

Dynamic performance improvement of an isolated wind turbine induction generator

A dynamic model of a variable speed stand alone wind generation system is developed. The transient performance of the system under variable wind gust and other disturbance conditions has been studied. It has been observed that a stand alone generator is very vulnerable to transient disturbances in the system. A variable susceptance excitation control system, installed at the generator terminal, has been shown to improve the dynamic performance of the system following transient disturbances. Additional pole-placement based PI and PID controllers in the excitation control circuit are shown to control the violently oscillating and even growing transients very effectively. The robustness of the proposed controller has been tested for various disturbances and also for a range of operation.

Supercapacitor based energy storage system for effective fault ride through of wind generation system

This paper investigates the potential of supercapacitor based energy storage system for enhancing fault ride through capability of wind driven induction generator. A dynamic model of wind generation system including Static Compensator (STATCOM) is developed. The power control capability of the STATCOM is extended by incorporating supercapacitor based energy storage system. A vector control technique based on the decoupling of real and reactive power is implemented. Simulation results show that fixed speed induction generator achieves significant grid fault withstand capability when aided by supercapacitor based energy storage system. Induction generator regains prefault status immediately after the fault is cleared.

Fast low voltage ride-through of wind generation systems using supercapacitor based energy storage systems

Dynamic model of a wind generation system with a supercapacitor based energy storage system is developed. The supercapacitor system has been interfaced with the wind generation system through a STATCOM. Decoupled P-Q control of STATCOM is implemented by introducing suitable transformation on its injected current. The controller parameters are obtained through a search based optimization technique. The effectiveness of the STATCOM supercapacitor energy storage was examined for very low voltage situations. Simulation studies demonstrated that the STATCOM supercapacitor control can achieve significant withstand capability for reasonable low voltage duration. System transients are adequately suppressed and normal conditions are quickly restored.

Voltage stability control of a wind generation system

Voltage instability is the main cause of concern for the large scale integration of wind power into the power grid. For the induction generator based wind generation system, the fixed capacitor located at the generator terminal can not normally cater for the reactive power demand during the transient disturbances like wind gusts and faults on the system. This paper presents two schemes for enhancing voltage stability of grid connected wind generator system. These are: variable susceptance control thru SVC and reactive power compensation through static compensator system (STATCOM). Simulation results show that both schemes are well capable of providing voltage stability and damping transient arising from reasonable level of disturbances. The STATCOM, however, demonstrates superior performance because of its fast response capability as well as its ability to provide compensation independent of system voltage support.

Variable susceptance excitation control for dynamic performance improvement of a stand-alone wind turbine induction generator system

Isolated wind farms employ simple squirrel cage induction generators driven by variable speed wind turbines. Lacking control capability, such generation can contribute very little to network support. Wind turbines mostly do not take part in voltage and frequency control and if a disturbance occurs, the turbines may be disconnected and reconnected when normal operation has been resumed. From operation viewpoint, this is definitely not acceptable. A primary reason for the rigidity of operation is the lack of excitation adaptation under variable wind conditions. This article proposes incorporation of a variable capacitance controller at the generator terminal which will automatically adjust the needed excitation. Further improvement of transient profile of the stand-alone wind turbine generator has been proposed through inclusion of additional stabilising control. Simulation studies show that the proposed excitation controller with additional PID circuit provides very good transient profile following reasonable input torque variations.

Dynamic Performance Enhancement of Agrid-Connected Wind Generation System

Abstract The recent trend of large wind power penetration to grid systems can be potentially troublesome in terms of dynamic performance of the system. In the absence of adequate control actions, the generators may have to be removed from the grid sometimes even for not so large changes in the wind system. This paper analyses the dynamic performance of a variable-speed wind turbine-driven cage generator connected to the grid system. It has been observed that a variable susceptance excitation controller at the generator terminals can control unusually large voltage as well as frequency swings arising from wind-gust conditions and system faults. Additional Proportional and Integral (PI) and Proportional, Integral and Derivative (PID) controls of thyristor angles in the susceptance control circuit were tested for dynamic performance improvement of the wind turbine-driven induction generator system. The variable susceptance excitation scheme with auxiliary PID control was observed to provide very good transient performance.