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A 3-phase 3-wire thyristor controlled reactor topology is presented comprising of two banks, involving thyristor switched and controlled coupled reactors (TSCCR), one bank of which is “Δ” connected and the other being “Y” connected. Each TSCCR comprises of a reactor with two well coupled identical sections, two main thyristor back-to-back switches and an auxiliary thyristor switch such that the two sections can be either connected in parallel or in series. The ratio of the effective reactor values between the “Δ” bank phase and that of the “Y” bank, as well as the condition when and which switch shall be used for phase control, are selected from an optimization process. Such an arrangement prevents the triplen harmonics from entering into the supply system and some major characteristic harmonics are also eliminated from the source current. Thus, without using any additional filters or phase shifting transformer or oversized reactors, this scheme enables reactive power control with a low current total harmonic distortion over a wide range of kVAr control. Simplicity in construction and operational requirements of the proposed topology makes it a viable and cost effective solution. Its modeling, analysis, and performance assessment are presented, supported by simulation and experimental results. [ABSTRACT FROM PUBLISHER]

A three-phase three-wire thyristor controlled reactor (TCR) topology is presented comprising of two reactor banks, involving simultaneous firing angle control of both banks having maximum kVAr in the ratio of 60:40. The first reactor bank is “Δ” connected and has phase switching whereas the second reactor bank is either “Δ” or equivalent “Y” connected with line switching. Such an arrangement prevents the triplen harmonics from entering into the supply system and some major characteristic harmonics can also be eliminated from the TCR line current due to the selection of the ratings of the two reactor banks. Thus, without using any additional filters or phase shifting transformer, this scheme enables reactive power control with a low current total harmonic distortion (THD) over a reasonable range of control, meeting requisite harmonics standards. Simplicity in construction and operational requirements of the proposed topology makes it a viable and cost effective solution. Its modeling, analysis, and performance assessment are presented. Simulation and experimental results support the theoretical proposition. [ABSTRACT FROM AUTHOR]

The conventional “Delta” connected thyristor-controlled reactor (TCR) bank used for static var compensation and other applications is proposed to be split into two identical “Delta” banks each having kvar capacity half of the total TCR capacity. The study presented shows that such combination of two identical “Delta” connected reactor banks, one with phase switching by thyristors and the other with line switching thyristor arrangement can effectively reduce the harmonic generation of the TCR. Since both the three-phase banks are connected in delta, the zero sequence triplen harmonics generated due to phase control of thyristors remain trapped inside the delta, thus reducing the harmonic injection into the power system. Further, some other major characteristic harmonics are also minimized in the TCR line current. Thus, the proposed TCR yields a low current THD which meets the requisite harmonics standards and it can therefore be used as an economic solution for reactive power control over a reasonable range in high power grid without using any external harmonic filter or special phase shifting transformer. This paper describes in detail the modeling, analysis, and performance assessment of the proposed scheme. Simulation results are furnished to evaluate the output characteristics of the scheme under varying operating conditions. Finally, experimental results are presented, which proves the theoretical proposition. [ABSTRACT FROM PUBLISHER]

A new thyristor-controlled reactor scheme is presented in this paper, in which the total bank is split into one Δ- and one Y-connected reactor bank with the addition of a low-rating zig-zag autotransformer, instead of the conventional scheme using a Δ-connected reactor bank with a harmonic current filter. This arrangement prevents the triplen harmonics generated by the Y bank from entering into the supply system and at the same time, the combination results in cancellation of some major characteristic harmonics from the source current. Thus, without using any additional filters or phase-shifting two-winding transformer, this scheme facilitates reactive power control over a wide range and also meets the requisite harmonics standards. The scheme is simple and provides a cost-effective solution to the VAr compensation problem. Simulation and experimental results are provided to validate the proposed concept. [ABSTRACT FROM PUBLISHER]

This paper presents the effectiveness of a microgrid (MG) in a distribution system. The combined heat and power (CHP) system is used to enhance the overall efficiency of the power system. Microturbines are used for CHP operation in this paper. The various methods of control of the MG are discussed. A simple low-cost model is proposed for MG based on frequency droop control for active power generation. The proposed model can be used in plug-and-play mode of operation of the MG. The model of MG is developed, and its performance is simulated in MATLAB platform. Performance of the model is studied under grid-connected and islanded conditions. [ABSTRACT FROM AUTHOR]

A battery Energy storage system (BESS) based voltage and frequency controller (VFC), for an Autonomous Asynchronous Generator (ASG) driven by an uncontrolled pico hydro turbine used in constant power mode, is presented in this paper. Excitation of the asynchronous generator with capacitor bank enables it to generate rated voltage at no load. The additional reactive power demand of the ASG on load and that for the load itself is provided by the VFC. The proposed controller has the capability of harmonic reduction, load balancing and load leveling along with voltage and frequency control. The VFC has been realized using an IGBT based current controlled voltage source converter (CC-VSC) having a battery at its DC link. A simple and effective linear control scheme using SPWM control has been used to control the CC-VSC. This control scheme is easier to implement on hardware than the other reported schemes, as it involves only linear PI controllers. The effectiveness of the proposed controller for an autonomous generator is demonstrated by simulation on MATLAB platform. [ABSTRACT FROM AUTHOR]

This paper presents the application of distribution static compensator (DSTATCOM) for mitigating the frequently occurring problems of voltage dips in autonomous systems. Consumer loads are experiencing proliferation of induction motors. The starting of induction motors draws large current causing voltage sag (dip). Autonomous Power system is comparatively less stiff than the grid connected system. Large starting current, causing objectionable voltage drop, is critical for an autonomous system. DSTATCOM has been effectively used to redeem this power quality problem. An asynchronous generator with a motor load having a DSTATCOM connected in shunt is simulated on a MATLAB platform using Simulink and Power System Block set. The simulation establishes the capability of DSTATCOM to mitigate the voltage dip problem for an autonomous system. [ABSTRACT FROM AUTHOR]

Large inductive loads require larger rating of DSTATCOM to generate the required reactive power of the load. Larger the rating of the DSTATCOM higher is the cost. Most distribution system has a base reactive power requirement. The reactive power demand at any instant varies around the base value. A window operation of the DSTATCOM is proposed in this paper. The base reactive power is provided by the TSCs and the DSTATCOM operates within a window (comprising of both inductive and capacitive reactive power) beyond the base reactive power provided by the TSCs. Thus the range of the reactive power compensation of the system is enhanced without the system being limited by the steps in which the TSCs operate. Within the window range, the DSTATCOM provides a continuous and smooth variation in the reactive power generation and can track the change in the VAr requirement very fast. To obtain optimal performance of the combined system, the TSCs are switched through a Fuzzy Logic controller. In this paper, window operation of the DSTATCOM along with Fuzzy Logic Controller operated TSCs is demonstrated for an autonomous asynchronous generator. The entire system has been simulated on MATLAB platform. [ABSTRACT FROM AUTHOR]