Unified Power Quality Conditioner for Grid Integration of Wind Generators

A Unified Power Quality Conditioner (UPQC) is relatively a new member of the custom power device family. It is a comprehensive custom power device, with integrated shunt and series active filters. The cost of the device, which is higher than other custom power/FACTS devices, because of twin inverter structure and control complexity, will have to be justified by exploring new areas of application where the cost of saving power quality events outweighs the initial cost of installation. Distributed generation (such as wind generation) is one field where the UPQC can find its potential application. There has been a considerable increase in the power generation from wind farms. This has created the necessity for wind farms connectivity with the grid during power system faults, voltage sags and frequency variations. The application of active filters/custom power devices in the field of wind generation to provide reactive power compensation, additional fault ride through capability and to maintain Power Quality (PQ) at the point of common coupling is gaining popularity. Wind generation like other forms of distributed generation often relies on power electronics technology for flexible interconnection to the power grid. The application of power electronics in wind generation has resulted in improved power quality and increased energy capture. The rapid development in power electronics, which has resulted in high kVA rating of the devices and low price per kVA, encourages the application of such devices at distribution level. This work focuses on development of a laboratory prototype of a UPQC, and investigation of its application for the flexible grid integration of fixed and variable speed wind generators through dynamic simulation studies. A DSP based fully digital controller and interfacing hardware has been developed for a 24 kVA (12 kVA-shunt compensator and 12 kVA-series compensator) laboratory prototype of UPQC. The modular control approach facilitates the operation of the device either as individual series or shunt compensator or as a UPQC. Different laboratory tests have been carried out to demonstrate the effectiveness of developed control schemes.A simulation-based analysis is carried out to investigate the suitability of application of a UPQC to achieve Irish grid code compliance of a 2 MW Fixed Speed Induction Generator (FSIG). The rating requirement of the UPQC for the wind generation application has been investigated. A general principle is proposed to choose the practical and economical rating of the UPQC for this type of application. A concept of UPQC integrated Wind Generator (UPQC-WG) has been proposed. The UPQC-WG is a doubly fed induction machine with converters integrated in the stator and rotor circuits and is capable of adjustable speed operation. The operation of UPQC-WG under sub and super-synchronous speed range has been demonstrated. The Irish grid code compliance of the same has been demonstrated with a detailed dynamic simulation

An improved fault control strategy for virtual synchronous generator with the coordination of STATCOM during unbalanced fault

The virtual synchronous generator (VSG) is a good solution for stabilizing the power system with high penetration of renewable energy. However, in case of serious unbalanced voltage disturbance/fault, the conventional VSG may lose voltage, inertia, and damping support characteristics to the grid and even can cause disconnection of renewable energy. This paper proposes an improved fault control strategy for VSG with the coordination of STATCOM. The proposed method can provide sufficient voltage support while keeping continuous system inertia and damping support under severe unbalanced fault. In the paper, an improved VSG and STATCOM control topology based on positive and negative sequence current control are first proposed so as to keep the damping and inertia support to grid during the grid fault. Secondly, the voltage support control method for the VSG with improved topology during unbalanced fault is introduced, which can achieve multiple control objectives, in terms of voltage support, current limitation, and active power output simultaneously. Then a coordination control scheme of improved VSG and STATCOM is developed so as to optimize the maximum control objectives in all possible scenarios, especially in the case of severe unbalanced fault. Finally, the effectiveness of the method is verified by using the MATLAB/SIMULINK simulation platform

Power quality services provided by virtually synchronous FACTS

The variable and unpredictable behavior of renewable energies impacts the performance of power systems negatively, threatening their stability and hindering their efficient operation. Flexible ac transmission systems (FACTS) devices are able to emulate the connection of parallel and series impedances in the transmission system, which improves the regulation of power systems with a high share of renewables, avoiding congestions, enhancing their response in front of contingencies and, in summary, increasing their utilization and reliability. Proper control of voltage and current under distorted and unbalanced transient grid conditions is one of the most critical issues in the control of FACTS devices to emulate such apparent impedances. This paper describes how the synchronous power controller (SPC) can be used to implement virtually synchronous FACTS. It presents the SPC functionalities, emphasizing in particular the importance of virtual admittance emulation by FACTS devices in order to control transient unbalanced currents during faults and attenuate harmonics. Finally, the results demonstrate the effectiveness of SPC-based FACTS devices in improving power quality of electrical networks. This is a result of their contribution to voltage balancing at point of connection during asymmetrical faults and the improvement of grid voltage quality by controlling harmonics flow.Postprint (published version

Energy and voltage management methods for multilevel converters for bulk power system power quality improvement

Electric arc furnaces (EAFs) are prevalent in the steel industry to melt iron and scrap steel. EAFs frequently cause large amplitude fluctuations of active and reactive power and are the source of significant power quality disturbances. Also EAFs comprise a major portion of industrial loading on the bulk power system. Typically, a static VAR compensator (SVC) or Static Synchronous compensator (STATCOM) are use to provide the reactive power support in order to alleviate the fluctuations in voltage at PCC. Static Synchronous Compensators (STATCOMs) provide a power electronic-based means of embedded control for reactive power support. Integrating an energy storage system (ESS) such as large capacitors with the STATCOM will improve the device performance to have active power controllability as well as the reactive power. A cascaded multilevel STATCOM has been utilized in order to compensate for all the fluctuations caused by an EAF both in the RMS of the voltage at PCC and also the active power generation. Designing a sophisticated controller, it is possible to get the STATCOM track the variations of active power in load. Therefore, the generator does not need to produce the random active power demanded by the load --Abstract, page iv

Study and Analysis of Power System Stability Based on FACT Controller System

Energy framework soundness is identified with standards rotational movement and the swing condition administering electromechanical unique conduct. In the exceptional instance of two limited machines, the basis of equivalent territory security can be utilized to ascertain the basic clearing point in the force framework, It is important to look after synchronization, in any case the degree of administration for customers won't be accomplished. This term steadiness signifies "looking after synchronization." This paper is an audit of three kinds of consistent state. The main sort of adjustment, consistent state steadiness clarifies the most extreme consistent state quality and force point chart. The transient solidness clarifies the wavering condition and the idleness steady while dynamic soundness manages the transient security time frame. There are a few different ways to improve framework soundness a portion of the techniques are clarified. Versatile AC Transmission Frameworks (FACTS) Flexible AC Transmission System (FACTS) regulators have been utilized frequently to comprehend the different issues of a non-variable force structure. Versatile AC Transmission Frames or FACTS are devices that permit versatile and dynamic control of intensity outlines. Improving casing respectability has been explored with FACTS regulators. This examination focuses to the upsides of utilizing FACTS apparatuses with the explanation behind improving electric force tire activity. There has been discussion of an execution check for different FACTS regulators