An Electromagnetic Var Compensator Suitable for Wind Power Access and Its Control Strategy

Abstract

As the proportion of large-scale wind farms and distributed wind power connected to the power grid increases annually, the effects of their intermittent and random characteristics on the active and reactive power fluctuations of the power grid are becoming increasingly evident, causing frequent voltage fluctuations at the grid-connected point. To solve these problems, this study proposes a new topology of an electromagnetic var compensator (EVC) based on a rotary phase-shifting transformer (RPST). The EVC can work under capacitive and inductive conditions to compensate for inductive and capacitive power, respectively. In accordance with the parallel steady-state mathematical model of the EVC, a double closed-loop control strategy with high precision and considerable robustness is proposed for the EVC on the basis of instantaneous reactive power theory. Finally, simulations show that the topology of the proposed EVC exhibits bidirectional and continuous adjustment capability that can meet the reactive power compensation requirements of power systems with a high percentage of wind power. Compared with the existing reactive power compensation device, the EVC exhibits the advantages of high voltage, large capacity, low cost, strong impact resistance, and good tolerance, imbuing it with great prospects for development.

Comprehensive Compensation Method for Co-phase Power Supply in Electrified Railways Based on V/v Transformer and Single-phase Rotating Var Compensator

“…However, both devices are more expensive than traditional transformers with the same capacity due to the use of power electronic devices. The operation loss is usually 6%~ 8%, and the control strategy is complex, making operation and maintenance difficult [20][21][22]. ESVC has a response time of about 100 milliseconds and uses electromagnetic SRPST as the main equipment, resulting in low cost and operating loss ranging from 2% to 4%.…”

“…The accurate power control strategy of RPFC has been proposed [18], and the flexible loop closing control method for an active distribution network based on RPFC have also been studied [19]. Reference [14] and reference [20] put forward two kinds of electromagnetic rotary var compensator based on RPST, which can realize the continuous and two-way adjustment of reactive power, and is characterized by low cost and strong impact resistance. Most of the current RPST-based studies are carried out in the three-phase system, and the researches on single-phase RPST are not mature, and the studies on RPST as a comprehensive compensation scenario for the co-phase power supply are inadequate.…”

Research on an Adaptive Compound Control Strategy of a Hybrid Compensation System

“…However, in weak grids, the TSC capacitive impedance and the grid-side inductive impedance can form a parallel resonant network for this system [17,18]. Under these circumstances, harmonic currents in the load current near the resonant frequency can excite parallel resonance in the system [19,20], resulting in increased harmonic content and additional distortion of the voltage waveform, negatively impacting power quality and seriously affecting power consumption of other loads [21][22][23].…”