Thesis Statement For Reactive Power Compensation

It is observed that the power factor is maintained closer to unity when the input voltage is reduced from 230V to 110Vrms. Figure 11 (a) and (b) shows the power factor correction of controller for various load condition such as 20% (60W) and 75% (230W). The power factor for the system is found to be 0.84 for light load condition and 0.99 for full load condition. The THD of input current at full load with predominant third and fifth harmonic components are shown in Figure 12(a) and (b).Third harmonics is found to be 4.8% and fifth harmonic component is 4.9% which are well within IEC 61000-3-2 standard during wide range of load variations. The variation in power factor with load is shown graphically in Figure 13(a). It can be inferred from the graph that improved resettable control operates at high power factor for all load condition whereas the conventional PI control has poor power factor under light load conditions. Figure 13(b) shows the comparison between the efficiency of the converter for varying load conditions with the conventional control method and the resettable integrator control. The converter’s efficiency is maintained at 92% for light load conditions and 96% for fully loaded condition with integrator control technique. Thus the improved resettable integrator controller provides a very simple and reliable solution for power factor correction and

Power electronic converters, especially DC/AC inverters have been extending their range of use in industrial application because they provide better system efficiency, reduced energy consumption and improved quality of power. The output voltage of inverter could be fixed or variable at a fixed or variable frequency and output waveforms are therefore made up of discrete values, producing fast transition rather than smooth ones [2]. The ability to

This paper deals with a Cuk Topology for Power Factor Correction (PFC). Most of the front-end PFC converters are designed using diode bridge and has lower efficiency due to losses with reduced power factor.The current flow, during each intervals of the switching cycle reduces the conduction losses compared to the conventional Cuk PFC Rectifier. The converter also provides protection against inrush current occurring at start-up, decreases input current ripple and reduces Electromagnetic Interference (EMI).It works in the Discontinuous Conduction Mode (DCM) to provide almost unity power factor and low distortions in the input current. To analyse the performance of this converter, a model based on the CUK topology has been designed by using MATLAB/ SIMULINK software and implemented with Proportional-Integral (PI) and Fuzzy logic controller.

However, these algorithms generally demonstrate a slow time response. Time-domain algorithms are based on the instantaneous extraction of harmonic currents/voltages. The common time-domain control strategies are instantaneous reactive power theory (IRPT) [6] and synchronous reference frame theory (SRF) [7]. Calculation of active and reactive powers by transforming three-phase voltages and currents into two phases is the principle of PQ theory, which does not work properly under non-sinusoidal supply conditions [8]. SRF theory is based on conversion of three-phase quantities into their corresponding dc components, and low-pass filters (LPFs) are employed for harmonic filtering which contain a time delay and deteriorate the performance of the controller [9].

So harmonics directly effect the system performance. For performance improvement of an inverter it is desirable to eliminate harmonics. IEEE 519 Standard gives maximum allowable limits for voltage and current distortions [3].

The term ”FACTS” (Flexible AC Transmission Systems) covers several power electronics based systems used for AC power transmission and distribution. The most interesting for transmission

This paper deals with the staging the evaluation of a three- phase Shunt Active Power Filter for Power Quality improvement. Power Quality problems can be take up using Shunt Active Power Filters. A simulation model based on mathematical model of a three-phase shunt active power filter has been developed. The results show an inherent power quality improvement in terms of reduced Total Harmonic distortion (THD) of source current. It also betrays power factor correction (PFC) properties to a large extent as the source current and source voltage are in phase. Keywords- shunt active power filter (SAPFs), Total harmonic distortion (THD), Proportional integral (PI) and Hysteresis current controller (HCC).

Now a days, the measurement of power quality components and electrical protection are becoming more complex and costly also. As

A DC-DC converter is a device used to obtain variable d.c. voltage from a source of constant d.c voltage .Therefore it may be thought of as d.c equivalent of an a.c transformer. Since they behave in an identical manner .Besides the saving in power, the d.c choppers offers greater efficiency, faster response lower maintenance, small size, smooth control and for many applications, lower cost than motor generator sets or gas tubes approaches.

ABSTRACT: -- In this a fuzzy logic control technique has been proposed for power quality improvement by using UPQC The UPQC is controlled to regulate the WF terminal voltage, and to mitigate voltage fluctuations at the point of common coupling (PCC), caused by system load changes and pulsating WF generated power, respectively. In order to reduce the voltage fluctuations that may cause “flicker”, and improve WF terminal voltage regulation, several solutions have been posed. The voltage regulation at WF terminal is conducted using the UPQC series converter, by voltage injection “in phase” with PCC voltage. On the other hand, the shunt converter is used to filter the WF generated power to prevent voltage fluctuations, requiring active and reactive power handling capability. The sharing of active power between converters is managed through the common DC link. A customized internal fuzzy logic control scheme of the UPQC device was developed to regulate the voltage in the WF terminals, and to mitigate voltage fluctuations at grid side. Simulation results show the effectiveness of the proposed compensation strategy for the enhancement of Power Quality.

For emolument of current harmonics (if any), the instantaneous resoluteness of different active and reactive powers is utilized - the active and reactive powers are computed utilizing p-q theory. No restrictions are imposed on the voltage or current wave forms, and it can be applied to three-phase systems with or without a neutral wire for three-phase generic voltage and current wave forms. Thus, it is valid not only in steady state, but withal in transient states.

The topic of this project is hardware-implementation of communication platform for consensus-based control in power systems. Because of the capacity of existing electric power distribution is nearly full, it is a trend to develop grid technology and enhance the intelligent level of power system [1]. Therefore, it is necessary to integrate and coordinate distributed generation (DG) effectively. Development of smart grid is becoming a popular and inevitable trend. The development of distributed generation has changed the traditional mode of power supply and utilization. And intelligent control of electrical devices can minimize the power consumption and reduce the operating cost. It is much economic and energy conservation.

The controller for the SSSC can be isolated, generally, into two main controllers, namely internal and external controllers. The main function of the internal controller is to give the control signal to drive the gate pattern generator of the power converter keeping in mind to generate a fundamental output voltage waveform with the desired magnitude and phase angle in synchronism with the ac power system. The function of the external controller, if exists, is to alter the reference signals which decides the practical operation of the SSSC so as to accomplish the desired system performance. The block diagram of the SSSC controller is represented in Figure 3.13.

Abstract — This paper presents unified power quality conditioner (UPQC) which is an integration of shunt and series Active Power Filters and aims to compensate for voltage sag, voltage and current unbalance and other power quality problems [1],[5],[6]. The UPQC helps to improve power quality at the point of installation on power distribution system or industrial power system. This paper deals with design of UPQC by considering a controller based on PQ theory. Reference signal generation for shunt active filter is done by using PQ theory while for series dual PQ theory is used [2], [3]. Reference signals are then applied to pulse generators. Pulse generation is carried out by using hysteresis band controller for each filter. The validation of proposed scheme is carried out by using Matlab/Simulink.

The control of active power and frequency in a power system is referred to as load frequency control (LFC). Stable operation of interconnected power system requires both constant frequency and constant tile-line power exchange [1]. An area control error (ACE), defined as a linear combination of tie line power and frequency deviations, is taken as the controlled output of LFC. LFC regulates ACE to zero such that frequency and tie-line power errors are forced to zeros. PID controller is widely used in LFC due to its simplicity but is gives long settling time and produces large frequency deviation [2]. In recent years, active disturbance rejection control (ADRC) developed by J. Han [3] and modified by Z. Gao [4, 5] has been proposed for the LFC controller [6-9].