M Aktarujjaman

Grid integration impacts and energy storage systems for wind energy applications — A review

Grid integration of variable wind power is confronted with many challenges. Challenges and issues associated with large scale wind integration into the existing power grid are discussed in this paper. Different wind turbine technologies and their technical features are presented. A review of the state of the art energy storage technologies, their characteristic features and comparison are presented. Finally, application of a hybrid battery-supercapacitor based energy storage systems with a direct drive variable speed wind turbine is investigated and simulation results are presented.

Control Stabilisation of an Islanded System with DFIG Wind Turbine

Distributed generation (DG) is often used to export power to the utility system. Loss of main supply can cause a severe loading mismatch between DG generation and load consumption. Consequently, the voltage and frequency of the islanded system will cross the allowable limit. Due to this fact, it is essential to control the voltage and frequency in the islanding mode of operation. In this paper, control stabilisation of an islanded system with a doubly-fed induction generator (DFIG) wind turbine has been addressed. Wind DG produces variable output and is not capable to produce enough reactive power. Hence, it is imperative to develop better control system for the islanding operation of wind system. Voltage and frequency control strategies of a doubly fed induction generator (DFIG) with energy storage for islanding operation have been developed. The investigation has been carried out through modeling of a doubly fed wind turbine and an energy storage system using SimPowerSystems tools of MATLAB. The simulations have been carried out in stand-alone operation of DFIG during various wind penetration.

Control Dynamics of a doubly fed induction generator under sub- and super-synchronous modes of operation

Depending on wind speed, a doubly fed induction generator (DFIG) based variable speed wind turbine is capable of operating in sub- or super-synchronous mode of operation using a back to back PWM converter. A smooth transition between these two modes of operation is necessary for reliable operations of the wind turbine under fluctuating wind. This paper presents the analysis and modeling of DFIG based variable speed wind turbine and investigates the control dynamics under two modes of operation. A battery energy storage (BESS) with a bidirectional DC-DC converter is added for a smooth transition between the modes. Mathematical analysis and corresponding modeling results show that the power flow in the rotor circuit under two modes can be controlled by changing current and voltage phase sequence through the rotor side converter (RSC) and line side converter (LSC). A coordinated control among RSC, LSC and DC link storage system ensure variable speed and maximum power extraction from the fluctuating wind and reduce the possibility of instability around synchronous speed. Extensive simulations have been conducted to investigate control dynamics under the two modes of operation and during transitions.

Black start with dfig based distributed generation after major emergencies

Grid connected distributed generation (DG) increases reliability and additional benefits for consumers as well as utilities. The stable and reliable operation of a power system is necessary after major emergencies (or blackouts) following a major system event. Distributed generation may be capable of black start and contribute to fast restoration process at medium to low voltage level. A large scale voltage and frequency excursions may occur during the process of black start with distributed generation due to low inertia and intermittency in power generation. Energy storage integrated with DG can absorb initial impact of central generation and ensure smooth load pickup during the restoration of a system. In this paper, the process of black start with a doubly fed induction generator (DFIG) based wind turbine is addressed and energy storage in DC link of DFIG is used for fast restoration after blackout. A control system has been developed for the process of black-start with DFIG. A sequence of actions for black start procedure is presented and tested.

Control stabilisation of multiple distributed generation

Grid connected distributed generation (DG) increases reliability and additional benefits for consumers as well as utilities. Recently, different types of DG are connected into distribution networks. Different control phenomena are applied based on types of DG. The stable and reliable operation of such power system requires sophisticated control. This paper presents a small-signal analysis for investigating dynamic behaviours of the system with multiple DG and also investigating control interactions between different types of DG. Dynamic model of a synchronous generator (SG) based hydro generator and inverter based photovoltaic/ wind distributed resources are considered for case studies to investigate grid connected and islanding mode of operation.

Contribution of DFIG-based wind farm to system frequency control

This paper investigates the impact of doubly fed induction generator (DFIG) based variable speed wind turbine on system frequency control. It is shown that DFIG has the capability to contribute short term frequency support following loss of generation. Simulation studies have been carried out on a reduced model of transmission power grid of Chittagong region in Bangladesh that combines hydro, gas and wind type generations. The dynamic simulations have been performed in professional software package PSS/E. Simulation results presented demonstrates the capability DFIG based wind farm to support system frequency during network contingencies.