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In order to effectively suppress surplus torque, realizing high precision loading, this paper applies proportional resonant (PR) control to the load torque control of electric load simulator (ELS), and analyzes and optimizes the stability and dynamic performance of ELS. The mathematical model of ELS is built in z-domain first in this paper, to establish foundation for designing and analyzing PR controller. The stability of the ELS with PR controller is analyzed through Nyquist diagrams, and optimized by reasonably designing the phase compensation angle of PR controller. The dynamic performance is analyzed through pole–zero plots, and the resonant gain of PR controller is designed based on the pole–zero plots to optimize the dynamic performance. Experimental results on ELS are provided, and the proposed method is compared with other typical methods, validating the effectiveness of the proposed method. [ABSTRACT FROM PUBLISHER]

Electric load simulator (ELS) is a resonant system and has a large coefficient caused by the stiffness of shaft. Its dynamic performance is always limited and stability is hard to be guaranteed. Besides, its external disturbance is the active motion of an actuator, and output is the load torque, which are both different from conventional servo systems. Therefore, the speed controller of ELS needs to be specially designed. In this paper, a speed controller for ELS is proposed to improve the dynamic performance and stability of ELS. The proposed controller consists of three control terms: a proportional (P) control term, a speed reference feedforward term, and a load torque compensation term. The tracking performance and surplus torque suppression performance of ELS with the proposed controller are analyzed in this paper. Stability analysis in discrete domain is carried out to guarantee the stability for digital applications. Robustness is also analyzed and an extended state observer is designed to compensate uncertainties and estimate speed. Furthermore, the proposed speed controller is compared with other three control methods. Experimental results on ELS are provided and validate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

In this paper, a new cascade active-front-end converter based on dual-boost/buck converters is proposed for an intelligent universal transformer (IUT), which allows adjusting the power factor to control both the active and reactive powers between medium and low voltage levels. Compared to the traditional cascade H-bridge converter, it has much enhanced system reliability owing to no shoot-through problems and lower switching loss with the help of using power MOSFETs. In addition, a unified control scheme is proposed for active–reactive power control and individual voltage balancing control, which is modular and easy to implement. In the end, a laboratory three-unit cascade active-front-end converter based on the half-bridge dual-boost/buck converter is constructed and tested. The experimental results verified the feasibility and effectiveness of the proposed active-front-end converter and the unified control scheme for IUT. [ABSTRACT FROM PUBLISHER]