Field Weakening Strategy Extended to Six-Step Operation for Dual Closed-Loop Current Control of Induction Motors

Le résumé fourni par la source

Six-step operation of induction motors (IMs) has many advantages such as reduced switching loss and fully utilized inverter output voltage. However, the system’s degree of freedom will be reduced to one in a six-step operation, which makes it difficult to maintain instantaneous current control capability. In this article, a field weakening strategy is proposed which can ensure high dynamic performance in a six-step operation. This strategy aims at clamping the voltage vector reference on the circumcircle of the vector hexagon and maintaining the q-axis current as constant as possible. The full expressions of adjusted voltage and current references in the six-step operation are derived based on the transfer function of the current controller. Afterward, a unified control system is proposed. In this system, the adjusted current references and differences are sent to the current controller as the state information in the next period, which means that the system achieves the dual closed-loop current control in a six-step operation without switching between different control methods. Rigorous simulations and experiments are performed to verify that the proposed unified control system achieves excellent control performance in six-step operation.

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