Reactive Power

The power system network is becoming more complex nowadays and it is very difficult to maintain the stability of the system. Today's enhancement of technology makes it possible to include new energy storage devices in the electric power system. In addition, with the aid of power electronic devices, it is possible to independently exchange active and reactive power flow with

Electricity metering plays a crucial role for all the commercial transactions on the energy market. Thus, an accurate evaluation of the performance of the electricity metering equipment is required not only in the reference operating conditions but also in the presence of disturbances affecting the power systems. As regards this matter, this paper analyzes the main aspects related to the

This paper describes the dynamic behaviour of a doubly-fed induction machine, operating with wind turbine. The rotor circuit of the machine consists only of a generator-side converter working under abnormal condition at stator side (fault condition and voltage drop take place in transmission lines of the grid system). The induction machine model is based on the stationary reference frame and the control-unit model is based on the line-voltage oriented reference frame. The generator-side controller provides good decoupling between active and reactive power. A powerful MATLAB/SIMULINK was used for the simulation of the wind energy conversion system of a 4 kW wind generator. The simulation results of the generator side converter show that the speed, torque and the ϕ sin (power factor) can be regulated independently to match the reference signals. The effects of assumed abnormal condition in the grid system are discussed with regard to stator current and rotor current of the induction m...

Pojazdy elektryczne są elementem składającym się na inteligentną sieć elektroenergetyczną (Smart Grid), bowiem poza funkcją transportową mogą dostarczać usług energetycznych w zakresie bilansowania mocy. W tym celu można odpowiednio wykorzystywać sterowalne układy ładowania takich pojazdów. Oczywistym wydają się zastosowania w bilansowaniu energii elektrycznej o charakterze czynnym. Tymczasem, w światowej literaturze pojawiły się pierwsze opracowania, pokazujące możliwości wykorzystywania pojazdów elektrycznych do dostarczania mocy biernej, zgodnie z potrzebami systemu dystrybucyjnego. Artykuł przybliża tą problematykę, przedstawiając przegląd stanu wiedzy technicznej oraz zagranicznej literatury związanej z tą nowatorską problematyką.

This paper first proposes a competitive market structure for reactive power procurement and then develops a methodology for incorporating voltage stability problems into the model. The owners of electric transactions should participate in this competitive framework and submit their own firmness bids in ($/MW) to the Independent System/Market Operator (ISO- IMO). ISO clears the market for reactive energy regarding the

This paper introduces a new neural method for harmonic identification and compensation. Based on Adaline networks, the proposed method is called the diphase currents method. The architecture and the learning are formulated based on an original decomposition of the disturbed currents. These currents are converted in the alphabeta- or DQ-spaces to separate each harmonic component in a linear expression. In this harmonic compensation method, the harmonic components may be individually selected and the reactive power may be compensated. The proposed method is robust and has been efficiently compared to other conventional and neural harmonic compensation methods. In order to validate the performance of the diphase currents method, simulation studies are carried out in the presence of plant variations. Experiments are also presented to show the performance of the proposed neural method under many practical industrial conditions.

A new 3-phase buck-boost unity power factor rectifier consisting of a 3-phase bridge buck PFC rectifier and two boost dc-dc converters connected in series is proposed for an industrial application where two independent output voltages need to be controlled. This paper presents the proposed topology and the requirements for this application. The proposed and alternative topologies are briefly compared. Through this comparison, it is shown that the proposed topology offers the best solution in terms of simplicity and functionality. The operation of the new topology is described in detail and then the control strategy including PWM calculations to obtain the best performance is given. The validity of the theory and practicality of the new rectifier system is confirmed through simulation and experimental results obtained from a 5 kW prototype.

Capacitor banks are applied in power systems to provide reactive power. The reactive power results in lower current in lines upstream of the bank improving system voltage and power factor and reducing line losses. Capacitor banks can be configured as ...

This paper focuses on I2R losses under nonsinusoidal conditions, mainly in cables and transformers. For this purpose, a mathematical development that takes in account the presence of harmonic components in the I2R losses calculation will be presented, so that the effects of the harmonic distortion in the power system components and consequently the impact on the power factor can be analyzed. Based on this study, a factor that evaluates the power quality performance in low voltage networks is presented. This factor is directly associated to the economical viability, once that it points when the losses minimization is interesting according to the cost/benefit ratio.