/pdf/analysis-of-dynamic-behaviour-of-electric-power-systems-with-1mcqkubobm.pdf

Analysis of Dynamic Behaviour of Electric Power Systems with Large Amount of Wind Power

This paper presents a new operational strategy for a small scale wind farm which is composed of both fixed and variable speed wind turbine generator systems (WTGS). Fixed speed wind generators suffer greatly from meeting the requirements of new wind farm grid code, because they are largely dependent on reactive power. Integration of flexible ac transmission systems (FACTS) devices is a solution to overcome that problem, though it definitely increases the overall cost. Therefore, in this paper, we focuses on a new wind farm topology, where series or parallel connected fixed speed WTGSs are installed with variable speed wind turbine (VSWT) driven permanent magnet synchronous generators (PMSG). VSWT-PMSG uses a fully controlled frequency converter for grid interfacing and it has abilities to control its reactive power as well as to provide maximum power to the grid. Suitable control strategy is developed in this paper for the multilevel frequency converter of VSWT-PMSG. A real grid code defined in the power system is considered to analyze the low voltage ride through (LVRT) characteristic of both fixed and variable speed WTGSs. Moreover, dynamic performance of the system is also evaluated using real wind speed data. Simulation results clearly show that the proposed topology can be a cost effective solution to augment the LVRT requirement as well as to minimize voltage fluctuation of both fixed and variable speed WTGSs.

A Variable Speed Wind Turbine Control Strategy to Meet Wind Farm Grid Code Requirements

Fast acting static synchronous compensator (STATCOM), a representative of FACTS family, is a promising technology being extensively used as the state-of-the-art dynamic shunt compensator for reactive power control in transmission and distribution system. Over the last couple of decades, researchers and engineers have made path-breaking research on this technology and by virtue of which, many STATCOM controllers based on the self-commutating solid-state voltage-source converter (VSC) have been developed and commercially put in operation to control system dynamics under stressed conditions. Because of its many attributes, STATCOM has emerged as a qualitatively superior controller relative to the line commutating static VAR compensator (SVC). This controller is called with different terminologies as STATic COMpensator advanced static VAR compensator, advanced static VAR generator or static VAR generator, STATic CONdenser, synchronous solid-state VAR compensator, VSC-based SVC or self-commutated SVC or static synchronous compensator (SSC or S2C). The development of STATCOM controller employing various solid-state converter topologies, magnetics configurations, control algorithms, switching techniques and so on, has been well reported in literature with its versatile applications in power system. A review on the state-of-the-art STATCOM technology and further research potential are presented classifying more than 300 research publications.

Static synchronous compensators (STATCOM): a review

Voltage stability is a key issue to achieve the uninterrupted operation of wind farms equipped with doubly fed induction generators (DFIGs) during grid faults. This paper investigates the application of a static synchronous compensator (STATCOM) to assist with the uninterrupted operation of a wind turbine driving a DFIG, which is connected to a power network, during grid faults. The control schemes of the DFIG rotor- and grid-side converters and the STATCOM are suitably designed and coordinated. The system is implemented in real-time on a real time digital simulator. Results show that the STATCOM improves the transient voltage stability and therefore helps the wind turbine generator system to remain in service during grid faults.

/pdf/real-time-implementation-of-a-statcom-on-a-wind-farm-35bj5uzint.pdf

Real-Time Implementation of a STATCOM on a Wind Farm Equipped with Doubly Fed Induction Generators

Connections of embedded wind generation (EWG) in the rural distribution system are susceptible to voltage rise. Current operating policy, based on the passive operation of the distribution network, limits the capacity of connected generation based on extreme conditions of minimum load and maximum generation. It is demonstrated that an active distribution network will allow considerably greater penetration of EWG. Three alternative control strategies are evaluated to increase the penetration level of EWG: EWG generation curtailment during low demand; reactive power management using a reactive compensator; and area-based OLTC co-ordinated voltage control. The application of these schemes is illustrated on a rurally connected 11 kV wind farm in a realistic 265-node generic distribution system model. Advanced optimal power flow is used to quantify the benefits of alternative control schemes for various EWG penetration levels. The impact of these schemes on network losses is also assessed.

Maximising penetration of wind generation in existing distribution networks

Effective reactive power control in distribution networks can have an important influence on the level of embedded generation that is acceptable and on the costs of its connection. A comprehensive study was undertaken to investigate how STATCOMs could be used with fixed-speed wind turbines, which use induction generators, to improve both the steady-state and dynamic impact of a wind farm on the network. An optimal power flow model based on loss minimisation was developed and used to show that operation of a wind farm at unity power factor is unlikely to allow maximum penetration of wind energy into a weak distribution circuit. The results of the electromagnetic simulations showed that the use of a STATCOM improves the steady-state stability limits of the network. They also showed that the use of a STATCOM with an appropriately designed control strategy can prevent damaging overvoltages that may occur under islanding conditions. The results also demonstrated that a STATCOM can be used to mitigate voltage fluctuations at blade passing frequency, which may occur if the rotors of a number of wind turbines fall into synchronism.

M.L. Lisboa

Papers

Application of STATCOMs to wind farms