Reactive Current Control Strategy Research Articles

Reactive Current Control Strategy of CHB-DSTATCOM Based on Unit Vector

For a single-phase distribution network static synchronous compensator (DSTATCOM) based on cascaded H-bridge (CHB) converter, the design of dq control-based system is difficult due to the coupling effect and current fiction. To address this issue, first, the mathematical model of dq control is derived, then the unit vector (UV) control based on αβ frame is proposed. In this paper, the compensation current reference is obtained through the instantaneous power theory and unit vector method. Proposed control structure eliminates the effects of the decoupling control and the complex current fiction. In addition, the DC-voltage balance is achieved. Finally, the effectiveness of the proposed control strategy is verified by the simulation and experiments.

Reactive Current Constraints and Coordinated Control of DFIG’s RSC and GSC During Asymmetric Grid Condition

Doubly fed induction generator (DFIG) based wind turbines have been found to be very sensitive to asymmetrical grid fault, wherein the harmful oscillations in the electromagnetic torque has being made a big concern. What makes things harder is that latest grid codes require grid-connected wind turbines to possess the ability of positive- and negative-sequence reactive current supporting. Hence, it becomes a guide mechanism to meet the grid codes and to ensure the operation safety of the wind turbines. Even though a tradeoff could be made between them, it is still quite difficult to coordinate the current dispatch of the DFIG’s rotor- and grid-side converters (RSC and GSC), since there are totally eight currents needing to be carefully designed, i.e., the positive- and negative-sequence active and reactive currents in each converter. To address this issue, this article analyzes the reactive current constraints in detail, based on which a coordinated reactive current control strategy is put forward for the DFIG-based wind turbines during asymmetrical grid condition. Simulation studies demonstrate the effectiveness of the proposed strategy.

Transient Reconfiguration and Coordinated Control for Power Converters to Enhance the LVRT of a DFIG Wind Turbine With an Energy Storage Device

This paper proposes a novel transient reconfiguration solution and coordinating control strategy for power converters to enhance the fault ride through and transient voltage support capabilities of a doubly-fed induction generator with an energy storage device (DFIG-ESD). During a grid fault, the connection of the grid-side converter is reconfigured such that it is connected to the rotor circuit in parallel with the rotor-side converter to provide an additional route for the rotor current, while the ESD is responsible for dc-link voltage regulation. A coordinated demagnetizing and reactive current control strategy is designed for the reconfigured DFIG during transient conditions. Specifically, the demagnetizing current is used to counteract the dc and negative-sequence stator flux components so that the transient electromotive force will be reduced. Simultaneously, the reactive current is added to meet the reactive power support requirement. The enhanced low-voltage ride through (LVRT) and transient voltage support capabilities obtained from the proposed design are demonstrated on the DFIG-ESD wind conversion system under different severe fault scenarios (asymmetrical and symmetrical fault). Additionally, The enhanced transient voltage support capability of the proposed design is further demonstrated by comparing with different control strategies.

Research on Practical Control Circuit of SVG in Single-Phase Low Voltage Field

For the use of Static Var Generator (SVG) in dynamic reactive power compensation of low voltage field, this paper proposes a reactive current control strategy suitable for single-phase bridge voltage source SVG and gives the main control circuit of this control method. The experimental results verify the effectiveness and practicality of this control strategy and the circuit design.

Fuzzy Controller Based 3Phase 4Wire Shunt Active Filter for Mitigation of Current Harmonics with Combined p-q and Id-Iq Control Strategies

As more and more variable frequency drives (VFDs), electronic ballasts, battery chargers, and static Var compensators are installed in facilities, the problems related to harmonics are expected to get worse. As a result Active power filter (APF) gains much more attention due to excellent harmonic compensation. But still the performance of the active filter seems to be in contradictions with different control strategies. This paper presents detailed analysis to compare and elevate the performance of two control strategies for ex-tracting reference currents of shunt active filters under balanced, un-balanced and non-sinusoidal conditions by using Fuzzy controller. The well known methods, instantaneous real active and reactive power method (p-q) and active and reactive current method (id-iq) are two control methods which are extensively used in active filters. Extensive Simulations are carried out with fuzzy controller for both p-q and Id-Iq methods for different voltage conditions and adequate results were presented. Simulation results validate the superior per-formance of active and reactive current control strategy (id-iq) with fuzzy controller over active and reactive power control strategy (p-q) with fuzzy controller.