Negative Sequence Voltage Compensating for Unbalanced Standalone Brushless Doubly-Fed Induction Generator

Abstract

During the unbalance operation of a standalone brushless doubly-fed induction generator (BDFIG), the negative sequence component causes significant unbalanced effect on the voltage and current of the power winding (PW). In this paper, anew control strategy is proposed to minimize the voltage unbalance effect of a standalone BDFIG under unbalanced loads. The proposed control strategy consists of two parts. The first part represents the conventional direct voltage control (DVC) strategy to control the frequency and magnitude of the positivesequence PW voltage. The second part is the proposed strategy to minimize the negative sequence component in the output voltage of PW with a negative sequence compensator in the machine side converter (MSC). The dual second-order generalized integrator (DSOGI) is used to extract negative-sequence component of the PW voltage. Proportional integral controllers are used to obtain reference of the control winding (CW) current which compensate the negative sequence component of the PW voltage. The proportional-integral-resonant (PIR) controller is applied to regulate the CW current in positive reference frame. A prototype 30 kVA BDFIG test platform is developed in the laboratory to verify the proposed strategy.

Modeling and Coordinated Control Design for Brushless Doubly-Fed Induction Generator-Based Wind Turbine to Withstand Grid Voltage Unbalance

“…The derived CW voltage equations, namely (20) and (21), are the object model using to design CW(MSC) current controller thereafter. It should be noted that ( 20) and ( 21) include all of the cross-coupling terms and disturbances on d-axis and q-axis whereas the existing proposed models in literature [15]- [17] neglected all or most of the cross-coupling terms and disturbances.…”

“…It should be noted that ( 20) and ( 21) include all of the cross-coupling terms and disturbances on d-axis and q-axis whereas the existing proposed models in literature [15]- [17] neglected all or most of the cross-coupling terms and disturbances. Therefore, the derived model expressed as (20) and (21) in this paper gives a much more accurate analytical model for BDFIG (MSC) current control under grid voltage unbalance.…”

“…In order to achieve proposed coordinated control objectives, both the MSC and GSC have to be controlled so that their positive and negative sequence currents can follow their respective reference values. According to (14), (20) and (32) and (33), current control design would use a simple single loop controller composed of a positive sequence current controller in the positive synchronous reference frame and a negative sequence current controller in the negative synchronous reference frame. cq-can be determined.…”

“…cq-can be determined. Then, according to (14) and (20), by using decoupling control and feedback control, the current controller can be designed as…”

Recent Advances of Control Technologies for Brushless Doubly-Fed Generators

“…22(a), both the obtained CW current compensation components and the basic CW current reference are in the same rotating frame, so that the fundamental and compensation components of CW voltage can be calculated at the same time. The control schemes proposed in [75] and [76] can be classified into the control method shown in Fig. 22(a).…”