Optimized Dynamic Operation of Fixed-Speed Wind Farms Using Classical and Advanced Controllers

Enhancing voltage stability and LVRT capability of a wind-integrated power system using a fuzzy-based SVC

A Static VAR Compensator Model for Improved Ride-Through Capability of Wind Farms

The static var compensator (SVC) has fast dynamic characteristics that can support effective system voltage following disturbances. Keeping reactive power reserve in an SVC during steady-state operation is always needed to provide reactive power requirements during system dynamics. This paper presents a new SVC control strategy with two stages of regulation slopes and two voltage regulation controls, which are fixed-voltage reference control and variable (floating) voltage reference control. The aim of this control is to limit the reactive power output from the SVC to the desired value during the steady-state voltage range and compensate the reactive power requirement from the upstream networks via the coordination with the under-load tap changer (ULTC). However, when the voltage deviates the steady-state voltage range, the SVC will react to support the system voltage using the SVC reactive power reserve. When a disturbance results in a new operating point, with a steady-state reactive-power output, the variable voltage reference control effectively changes the SVC output slowly and returns it within the steady-state margin.

Static VAR compensator (SVC) based on AC sinusoidal voltage regulators are considered. The approach of SVC design based on AC voltage regulators application is presented. Various SVC schemes based on AC sinusoidal voltage regulators application are considered; description of electromagnetic processes in SVC circuits are carried out. The analysis of the reactive power control in considered SVC circuits is presented. The results of mathematical modeling of SVC circuits are also presented.

In this paper, the practical impedance approach steady-state analysis in the frequency domain for the three-phase self-excited induction generator (SEIG) with squirrel-cage rotor is presented along with its operating performance evaluations. The three-phase SEIG is driven by a variable-speed prime mover(VSPM) in addition to a constant-speed prime mover (CSPM) such as a wind turbine and a micro gas turbine for clean alternative renewable energy in rural areas. The basic steady-state characteristics of the VSPM are considered in the three-phase SEIG approximate equivalent circuit and the operating performance of the three-phase SEIG coupled with a VSPM and/or a CSPM are evaluated and discussed online under the conditions related to the speed changes of the prime mover and the electrical inductive load power variations with simple computation processing procedures. A three-phase SEIG prototype setup with a VSPM is implemented for small-scale clean renewable and alternative energy utilizations. The experimental performance results give good agreement with those obtained from the simulation results. Furthermore, a proportional-integral (PI) closed-loop feedback voltage regulation of the three-phase SEIG driven by the VSPM on the basis of the static var compensator (SVC) composed of the thyristor phase-controlled reactor in parallel with the thyristor switched capacitor and the fixed-excitation capacitor bank is designed and considered for the wind generation as a renewable power conditioner. The simulation analysis and experimental results obtained from the three-phase SEIG with SVC for its voltage regulation prove the practical effectiveness of the additional SVC with the PI-controller-based feedback loop in steady-state operation in terms of high performance with low cost.

Static var compensator (SVC) is used to improve transient voltage stability of the asynchronous wind farm. The issue of voltage stability and transient stability of wind power system are also addressed. A novel control strategy of SVC is proposed instead of the types of traditional feedforward and uniline feedback to control SVC. The proposed method makes control performance better and the compensation efficiency higher. At the same time, balanced compensation strategy of orientation vector conversion is applied instead of traditional model of steady-state phasor to calculate the compensation electrical susceptance. Using this method can overcome the shortcoming of dynamic characteristics and adaptability. At last, the simulation results indicate this control strategy could improve the stability of wind farm effectively and quickly.

Thyristor Controlled Reactor (TCR) based static VAr compensator (SVC) systems can be implemented with several optional topologies which depends on the required functions and associated costs. In this paper, the analysis and implementation of a 12-pulse TCR-based voltage regulation type SVC system is discussed. In literature, this paper represents the most detailed field implementation and discussion of a 12-pulse TCR-based SVC system that is used for voltage regulation purposes. Principles of operation and overall design assessment are described. This system has been installed to mitigate the voltage regulation problem in a village located in Durma area, Saudi Arabia. The entire installation consists of two identical (except for power transformers) SVCs with a rated power of 1.5 MVAr each. A cascaded PI control algorithm is implemented and steady and dynamic states are assessed. Test results from the field are given with a discussion of the overall performance.

This paper deals with the development of a hybrid method of control for voltage regulation in micro hydro power station using self-excited induction generation. The proposed method performs the voltage regulation with the use of capacitor banks plus static VAR compensator. A considerable literature review was undertaken to identify the key control systems for voltage regulation applied to self-excited induction generator. A control algorithm and a project for the variable capacitors are proposed based on the resolution of normative procedures of Electricity Distribution in the National Electric System. Simulation and experimental results are presented to demonstrate the performance of the proposed hybrid method for the voltage regulation of the self-excited induction generator during variations of different types of load. Moreover, experimental results concerning the analysis of reactive power processed by the static VAR compensator during its operation in the hybrid method are obtained. These results are compared with the results obtained through the method that uses only the static VAR compensator, where the hybrid method has advantages in terms of reduction of the size of the static VAR compensator.

The inherent time-varying nature of the wind farm power causes undesired voltage flicker in the power network. In order to mitigate the flicker to enhance the performance of the wind power system with very fast dynamics, the static VAr compensator (SVC) is utilized. However, the SVC operates with some delays which negatively affects its performance. This persuades us to predict the reactive power of the wind farm to compensate for the real-world delay. The predicted reactive power is then utilized in the SVC. Therefore, this paper develops a novel fuzzy one-step-ahead prediction approach for the wind farm reactive power. The proposed fuzzy prediction uses a Takagi-Sugeno (TS) fuzzy representation whose unknown parameters are tuned online based on an extended Kalman filter (EKF). The wind farm is modeled as a time-varying current source which its amplitude and phase change every 0.01 s. A large set of the actual data of a wind farm in Manjil, Iran is gathered and directly utilized in the simulation process. Several flicker indices are calculated to evaluate the proposed prediction method. The obtained results show the performance enhancement and flicker mitigation of the suggested power scheme.

The contribution of wind power in conventional generation is increasing rapidly now-a-days. Hence a better understanding of wind power plants is required. But the wind power plants generally containing induction generators exhibit a rather different behavior than the conventional power plants which use synchronous generators. The purpose of this paper is to analyze and study transient stability of a wind farm based on conventional fixed speed Induction generator when it has been integrated with a weak grid. A comparative analysis of the transient stability improvement of a FSIG wind plant has been done, when it is supported with FACTS like S.V.C and STATCOM of equal ratings. Single case of transient condition i.e. a three phase fault has been studied by simulation. With the increase in demand of power and decrease of fossil fuels, mankind has been forced to search alternative sources for the generation of electricity. Wind power in spite of being stochastic in nature has proved itself as a viable solution to this problem. As the wind turbine technology is developing at a good pace, more and more wind power plants are being integrated with the conventional form of generation. With the increase in the ratio of wind generation to conventional generation, several problems related with integration of wind farms have emerged. These problems are due to distinct properties of the generators used with the conventional form (Thermal & Hydro) of generation and wind based generation (1)-(4). In thermal and hydro power based generation synchronous generators are used while in wind based generation mostly induction generators are used. Induction and synchronous generators do not exhibit similar behavior during power system stresses (transients). Moreover, increase in wind power based generation requires a reliable transmission system for power evacuation to the load centers. As the wind farms are mainly concentrated in far flung and rural areas their interconnection with the grid becomes a problem. This problem is mainly due to the existence weak transmission grids in the rural areas (1)-(4). Earlier when the share of wind power generation as compared with the conventional generation was low, during transient conditions; whenever the power system reached on the verge of instability the wind farm was disconnected from the grid and was reconnected when transients passed away. But as the share of wind power in the conventional generation increased, the practice of disconnecting the wind farms from the rest of the grid led to the drop in frequency of the power system. So now-a- days even if a fault occurs in the power system somewhere near the wind farms, they still remain connected with the grid for a critical time period. This phenomenon is called fault ride through (FRT) in wind farms (5). This paper has studied a transient condition (fault) in a grid connected fixed speed induction generator based wind farm and its fault ride through performance. A comparison of the performance of fact devices like static var compensators (svc) and static synchronous compensators (statcom) in improving the transient stability of wind farms during fault is also done.

This paper presents the design of static VAR compensator (SVC) for 27.5 kV West Siberian Railway system. The SVC is designed to adjust the voltage profile and power grid performance between two supplying stations. The design of SVC power components depends on adjusting the system voltage profile and increasing railway power grid efficiency. The design of such SVC includes the determination of SVC and voltage regulator parameters proper for railway system requirements. This paper illustrates the influences of SVC on voltage levels across the power grid and performance of the voltage regulator during normal and contingences conditions.

In this paper, prototypes of two shunt flexible AC transmission system (FACTS) devices, a thyristor switched reactor (TSR)-based static VAr compensator (SVC) and a thyristor controlled reactor (TCR)-based static VAr compensator- have been developed. The design and testing of both a TSR-based SVC and a TCR-based SVC are accomplished in the Power Systems Research Laboratory of Nigde University. The TSR-based SVC and TCR-based SVC devices are studied in three-bus and single machine infinite bus systems for three-phase static load conditions. The effects of TSR-based SVC and TCR-based SVC devices on load voltages are also analyzed. Experimental results show that significant improvement in reactive power compensation and voltage regulation is achieved by using TSR-based SVC and TCR-based SVC.

Automatic landing system using neural networks and radio-technical subsystems

The conventional energy resources are depleting considerably. It has become confronts to fulfil the remarkable growth in demand of electrical power. The renewable energy resources (RES) include solar, wind, hydro, biomass, etc are eco-friendly and provide clean output. This paper deals with the Battery energy storage system (BESS) based Distributed Static Compensator (DSTATCOM) to control the voltage and frequency of constant speed prime mover driven self excited induction generator (SEIG) for feeding 3-phase 4-wire loads. Further, this paper also presents the comparison of Proportional Integral (PI) controller and Fuzzy Logic (FL) controller for voltage and frequency regulation. The FL controller works faster than PI and improves the performance of SEIG. The drawback of SEIG is poor voltage regulation and it requires an adjustable reactive power source with varying loads to maintain constant terminal voltage. A three phase insulated gate bipolar transistor based current controlled voltage source converter working as a DSTATCOM is used for harmonic mitigation, load leveller, load balancing and neutral current compensator. The proposed system is modelled and simulated in MATLAB/ simpower system.

ABSTRACTThis paper presents the simple voltage regulation scheme using a three-phase static VAr compensator (STATCON) for a stand-alone self-excited induction generator (SEIG) that uses variable-speed wind generation system. Most of the loads are inductive and need an equal amount of leading VArs, which is generated by the STATCON and injected at point of common coupling instantaneously. The one cycle control technique is considered and modified to implement for VAr compensation of SEIG voltage regulation. To emphasis the controller characteristics, a STATCON is designed for a 3-Ø, 0.75 kW, 415 V, 1.8 A Induction Machine and tested in simulation using MATLAB/SIMULINK software.