Leakage Current Mitigation of Photovoltaic System Using Optimized Predictive Control for Improved Efficiency

This paper proposes an optimized predictive control strategy to mitigate the potential leakage current of grid-tied photovoltaic (PV) systems to improve the lifespans of PV modules. In this work, the PV system is controlled with an optimized predictive control algorithm that selects the switching voltage vectors intelligently to reduce the number of computational burdens. Thus, it improves the dynamic performance of the overall system. This is achieved through a specific cost function that minimizes the change in common-mode voltage generated by the parasitic capacitance of PV modules. The proposed controller does not require any additional modulation schemes. Normalization techniques and weighting factors are incorporated to obtain improved results. The steady state and dynamic performance of the proposed control scheme is validated in this work through simulations and a 600 W experimental laboratory prototype.

Optimization of TSPWM for Common-Mode Voltage Reduction in Vehicular Electric Drive System

Common-mode voltage can be reduced effectively by optimized modulation methods without increasing additional costs. However, the existing methods cannot satisfy the requirements of the vehicular electric-drive application. This paper optimizes the tri-state voltage modulation method to reduce the common-mode voltage for vehicular electric drive system applications. Firstly, the discontinuous switching issue during sector transition is analyzed. Under the limit of two switching times in one period, multiple alignments combination is proposed to address that issue. Secondly, the zero-voltage time intervals in different modulation ranges are explored. This paper proposes an unsymmetric translation method to reconstruct the voltage vector, and then the minimum zero-voltage time interval is controlled to enough value for safe switching. Finally, the proposed methods have been validated through experiments on a vehicular electric drive system. The results show that the common-mode voltage can be reduced effectively in the whole range with the optimized tri-state voltage modulation method.

Investigation of SVPWM Based Sliding Mode Control Application on Dual-Star Induction Motor and Dual Open-End Winding Induction Motor

The present paper deals with a comparative study of the Sliding Mode Control (SMC) technique application on three-phase Dual Star Induction Motor (DSIM) topology and the Dual Open-End Winding Induction Motor (DOEWIM). Where, in these two topologies the Space Vector Pulse Width Modulation (SVPWM) has been used for the control of the two two-level inverters and the four two-level inverters, which have been used to power the two motors under application respectively. The main objective of this study is to demonstrate the higher performances of the DOEWIM under the application of SMC combined with SVPWWM, which aims to overcome the main drawbacks faced when using the conventional topology DSIM in industrial applications. Especially in terms of decreasing the harmonics content in the stator current, reducing the overall ripples of the developed electromagnetic torque, the elimination of the common mode voltage and increasing the robustness against the load torque variation and speed reverse. The obtained simulation results show clearly the main advantages of using the topology of DOEWIM compared to the DSIM topology which present a very promising application especially in heavy industrial requiring high power motors.

A Carrier-Based Discontinuous PWM Strategy of NPC Three-Level Inverter for Common-Mode Voltage and Switching Loss Reduction

For the conventional carrier-based pulse width modulation (CBPWM) strategies of neutral point clamped (NPC) three-level inverters, the higher common-mode voltage (CMV) is a major drawback. However, with CMV suppression strategies, the switching loss is relatively high. In order to solve the above issue, a carrier-based discontinuous PWM (DPWM) strategy for NPC three-level inverter is proposed in this paper. Firstly, the reference voltage is modified by the twice injection of zero-sequence voltage. Switching states of the three-phase are clamped alternatively to reduce both the CMV and the switching loss. Secondly, the carriers are also modified by the phase opposite disposition of the upper and lower carriers. The extra switching at the border of two adjacent regions in the space vector diagram is reduced. Meanwhile, a neutral-point voltage (NPV) control method is also presented. The duty cycle of the switching state that affects the NPV is adjusted to obtain the balance control of the NPV. Still, the switching sequence in each carrier period remains the same. Finally, the feasibility and effectiveness of the proposed DPWM strategy are tested on a rapid control prototype platform based on RT-Lab.