Control design and experimental verification of the brushless doubly‐fed machine for stand‐alone power generation applications

Abstract

In this study, a control scheme for the stand-alone generation system based on brushless doubly-fed machine (BDFM) is presented. The output voltage amplitude and frequency are kept constant under variable rotor speed and load by regulating the amplitude and frequency of the control winding (CW) current of BDFM appropriately. The control scheme utilises a CW current vector controller as the inner loop, and a power winding voltage amplitude controller and a frequency controller as the outer loop. The proposed control scheme has been implemented on a prototype BDFM designed for the variable-speed stand-alone ship shaft generation application. Moreover, the satisfactory dynamic performance and low total harmonic distortion of the output voltage in the proposed stand-alone generation system is verified by experiments with two kinds of typical loads: three-phase induction motor load and three-phase RL inductive load.

Flux-Angle-Difference Feedback Control for the Brushless Doubly Fed Machine

“…The brushless doubly fed machine (BDFM) retains the advantage of a low-cost inverter, but does not need a brush gear and slip ring, achieving low maintenance costs and a high reliability. The BDFM has the attractive feature of becoming the next generation of wind generators, so research on the BDFM has great practical significance [4][5][6]. However, the BDFM is a system with multi variable, strong coupling and complex nonlinearity, which raises difficulties for BDFM's high performance controlling.…”

Internal Model Current Control of Brushless Doubly Fed Induction Machines

“…When R i is designed as R i >> R t , the current is instantaneously controlled within the control bandwidth, and the current controller is robust to the variation of R t [28]. In this paper, the active damping controller F R (s) is expressed as: Therefore, the proposed current controller is designed based on Equations (18) and (19). According to Figure 2, the CW stator voltage is written as:…”

“…Finally, the overall diagram of the current controller is given in Figure 3, where it consists of the internal model current controller in Equation (18), the active damping controller in Equation (19), and the feedback term composed by the PW voltage. Considering that the expected rotor speeds and power both are achieved by adjusting the CW stator current, and these outer loop control methods can refer to the existing references as discussed in Section 1, thus only the inner current controller is addressed and verified in this paper.…”

“…In the inner current sub-system of the BDFIM, complex cross-coupling terms, the back electromotive force (EMF) disturbance and parametric errors increase the difficulty of the controller design and decrease the control performance [17][18][19], while the previous current control methods of the BDFIM have not addressed the problems caused by parametric errors. In addition, effects of complex coupling terms are usually eliminated or suppressed by combining the conventional PI controller and the feedforward control.…”

“…Different feedforward compensation terms generate diverse total resistances and total leakage inductances of the current sub-system, which directly affect the current controller design and the control performance. In [17] the feedforward component consists of the CW flux, the PW flux, and the CW current; In [18], the PW flux, the derivative of the PW flux, the PW current and the CW current make up the feedforward component; while the feedforward terms are calculated by the PW current, CW current and their derivatives in [19]. However, these feedforward terms are very complex, and the compensation performance is guaranteed by precise motor parameters and calculations especially when the derivatives of the current are included.…”