Search

This article presents a new collaborative control method based on expert decision, proposed for the combined system of an ac grid with a low THD thyristorized static var compensator (SVC), interconnected to a dc microgrid through a distribution static compensator (D-STATCOM) that also works as a bidirectional power converter. The combination of large rating SVC and a low rating D-STATCOM functions as a hybrid compensator for the ac distribution grid. In the combined mode of operation, the D-STATCOM mitigates voltage fluctuations and compensates initial var demands, while the SVC caters to the base var requirements. The D-STATCOM has also been used for integration of a dc microgrid to the utility grid, permitting exchange of power between the grids and thereby reducing voltage fluctuations of both the systems. The proposed collaborative control method based on expert decision can extract the full advantages of the respective subsystems as per demand of the operating condition. This combined system complies with the relevant harmonic standards and can effectively correct system power factor, stabilize bus voltage, and mitigate voltage flicker under fluctuating load conditions. Theoretical analyses with simulation results as well as experimental results show that the proposed system can meet the requirement of continuous dynamic reactive power compensation and voltage stabilization with low cost, high reliability, and large capacity. [ABSTRACT FROM AUTHOR]

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]

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]