Sensorless Control of Standalone Brushless Doubly Fed Induction Generator Feeding Unbalanced Loads in a Ship Shaft Power Generation System

Abstract

The standalone brushless doubly-fed induction generator (BDFIG) has demonstrated excellent energy saving performance in ship shaft power generation applications. As a standalone system, it exhibits unbalanced terminal voltages and poor performance under unbalanced loads. However, the existing control scheme of grid-connected BDFIGs cannot be directly applied to stabilize the amplitude and frequency of terminal voltage when the rotor speed and electrical load vary. This paper presents a new sensorless control scheme for the standalone BDFIG under unbalanced load conditions in the ship shaft power generation system. A second-order generalized integrator based quadrature signal generator is introduced to realize the rotor speed observer for the standalone BDFIG feeding unbalanced loads. The compensation method of negative-sequence power winding voltage is proposed to eliminate the negative-sequence component of the unbalanced power winding voltage. Comprehensive experiments are carried out on a prototype BDFIG with and without the compensation of negative-sequence power winding voltage. The good performance of the proposed sensorless control scheme is verified by the experimental test results.

An Improved Rotor Speed Observer for Standalone Brushless Doubly-Fed Induction Generator Under Unbalanced and Nonlinear Loads

“…With consideration of both the response speed and the stability of the SOGI, generally, ξSOGI is set to 0.707 [23]. From (20) and (21), the settling time of SOGI can be given by…”

“…However, the impact of unbalanced and nonlinear loads on the RSO has not been analyzed, and the parameter design has not been developed. In [20], a similar improved RSO has been applied to sensorless control of the standalone BDFIG with unbalanced loads, but it has not been verified under nonlinear loads.…”

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

“…The design methodology and simulation and experimental results are analyzed and presented in this paper. Although the propose strategy is similar to the other two typical strategies proposed in [16] and [17] in the two aspects of control targets and implementation principles, the three strategies differ in key measures of implementation, numbers of sampled feedback quantities, and numbers of P, PI and PIR controllers. The strategy proposed in this paper can be regarded as the simplest one among the three strategies due to the use of the fewest P, PI and PIR controllers.…”

“…The effects of unbalanced load in a ship shaft power generation system have been presented in [16] and [17]. In [16], the control scheme composes of two parts, where the first part is the PW voltage controller used to maintain the constant frequency and magnitude of the PW voltage, and second part is the PW voltage compensator employed to compensate the unbalance effect in the PW voltage. The PW voltage compensator works separately from the first part and provides the additional three-phase CW voltage for compensating unbalanced PW voltage.…”

Bidirectional Harmonic Current Control of Brushless Doubly Fed Motor Drive System Based on a Fractional Unidirectional Converter Under a Weak Grid

“…1. Most control methods for BDFM assume that the system operates under a normal [6], [7] or unbalanced grid [8], [9]. In [6], the unidirectional converter was applied and a simple closed-loop scalar control strategy was introduced based on the torque-angle characteristic.…”