This study proposes an improved direct power control (DPC) strategy based on sliding mode control (SMC) with dual closed loop for the Vienna-type rectifier to improve transient response during both start-up and load step-change periods and to guarantee stability in steady state. The inner power closed-loop utilises SMC-DPC controller to directly regulate the required rectifier's control voltage without transforming to synchronous rotating coordinate reference frame or tracking phase angle of the grid voltage, which simplifies the control system. In addition, the outer loop employs a novel sliding mode controller to improve the dynamic performance of the dc output voltage and the instantaneous power. Finally, the dynamic and steady-state performances of the grid current, dc output voltage, active/reactive power are experimentally investigated and compared with the conventional proportional-integral-DPC scheme, both the simulation and the experimental results demonstrated the dynamic performance and stability of the proposed control scheme.
Vienna rectifiers are unidirectional three-level boost rectifiers used in extensive industrial applications. Much effort has been devoted to study the control strategies for Vienna rectifier. This paper introduces the manipulation principles and operation steps of model predictive control strategy based on optimal switching sequence principle. In order to address several issues of the conventional methods, an improved model predictive control strategy has been proposed to regulate the ac currents and neutral point voltage deviation. The proposed strategy has been validated by experiments. The consequences show that the proposed strategy can achieve accurate prediction especially during neutral point voltage unbalance by dealing with constraints and provide excellent performance in dynamic property and stability.
Active power filter (APF) is the most popular device in regulating power quality issues. Currently, most literatures ignored the impact of grid impedance and assumed the load voltage is ideal, which had not described the system accurately. In addition, the controllers applied PI control; thus it is hard to improve the compensation quality. This paper establishes a precise model which consists of APF, load, and grid impedance. The Bode diagram of traditional simplified model is obviously different with complete model, which means the descriptions of the system based on the traditional simplified model are inaccurate and incomplete. And then design exact feedback linearization and quasi-sliding mode control (FBL-QSMC) is based on precise model in inner current loop. The system performances in different parameters are analyzed and dynamic performance of proposed algorithm is compared with traditional PI control algorithm. At last, simulations are taken in three cases to verify the performance of proposed control algorithm. The results proved that the proposed feedback linearization and quasi-sliding mode control algorithm has fast response and robustness; the compensation performance is superior to PI control obviously, which also means the complete modeling and proposed control algorithm are correct.
This paper presents a simplified SVM for Viennatype rectifier which is based on the space vector modular of a three-level converter into a two-level converter, the dwelling time calculation and switching sequence selection are easily done like conventional two-level rectifier, which is discussed in detail in this paper. Meanwhile, based on inherent correlation between carrier-based PWM and SVM for three-level converter, the equivalent carrier-based PWM for Vienna-type rectifier is derived by injecting the optimum zero-sequence vector. In addition, the neutral point voltage unbalance problem is solved successfully by utilizing the proposed equivalent SVM algorithm. Simulation models in Matlab/Simulink and a DSP-controlled 10kW Vienna-type rectifier are used to verify the proposed method is feasible and efficient for Vienna-type rectifier.
Predictive direct power control (PDPC) and sliding mode control (SMC) have been proposed as effective schemes for three-phase rectifiers. However, the conventional PDPC still has sampling power errors caused by control delay. Furthermore, the existing SMC can not well work with PDPC to provide fast error convergence and strong robustness during both start-up and load step change periods. To solve the problems above, this paper proposes an improved hybrid SMC-PDPC control scheme for Vienna rectifier, which uses lagrangian liner interpolation to predict the next sampling power value with eliminating inner-loop power errors. Additionally, this paper presents a novel SMC based on squared voltage in the outer loop. Experimental results based on 10 kW prototype circuit are presented to confirm the effectiveness of the proposed scheme.
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