Armin Miremad’s research while affiliated with University of Tehran and other places

In this article, we introduce a model predictive control with optimal switching sequence (OSS-MPC) for a multilevel static synchronous compensator (STATCOM). The studied STATCOM is based on a hybrid multilevel inverter named HC-FNPC formed by the cascaded connection of H-bridge cells with a full-bridge neutral point clamped cell (FNPC). In this article, the optimal switching sequences are derived for HC-FNPC STATCOM by considering the impact of each switching sequence on the voltage of capacitors. Then, the control objectives of hybrid multilevel STATCOM, i.e., ac current control and capacitors’ voltages balancing, are formulated in terms of OSS-MPC for the first time. In contrast to the conventional MPC, this method provides a fixed-switching frequency. Also, by a combination of optimal switching sequences in MPC, the regulation of capacitors’ voltages with unequal values is realized. The control system's performance is verified on a nine-level (9L) 2.4 Mvar/11 kV HC-FNPC STATCOM in MATLAB/Simulink. Also, the experimental results are provided on a 9L 1.25 kvar/220 V scaled-down hardware prototype.

This study presents a STATic synchronous COMpensator (STATCOM) based on hybrid cascaded H‐bridge and full‐bridge neutral point clamped (HC‐FNPC) inverter. The advantages of HC‐FNPC over symmetric and asymmetric cascaded H‐bridge (HB) in STATCOM application are verified in terms of number of power components and voltage balancing capability. A control strategy is proposed to achieve control aims, i.e. reactive current compensation and balancing the voltages of capacitors. HC‐FNPC‐based STATCOM consists of two types of cells, i.e. full‐bridge neutral point clamped (FNPC) and HB cells with one and two capacitors in their DC side, respectively. A hierarchical balancing scheme is proposed to regulate the voltage of capacitors in mixed cells. In the first control layer, the voltage vector of cells is adjusted so that the active power is uniformly distributed among the cells. In the second control layer, the switching redundancies of FNPC are used to provide voltage balancing. The introduced balancing scheme not only provides voltage balance among capacitors, but also distributes the reactive power equally among the cells and increases the reliability in this way. The performance of the proposed control is validated through simulation in MATLAB/SIMULINK environment and experimental results based on a single‐phase nine‐level HC‐FNPC‐based STATCOM laboratory prototype.

This paper develops model predictive control with a finite control set (FCS‐MPC) for a static synchronous compensator (STATCOM) based on hybrid cascaded H‐bridge and neutral point clamped (HC‐HNPC) multilevel inverter. By applying FCS‐MPC to basic multilevel structures such as the cascaded H‐bridge (CHB), the dynamic performance is improved; but, as the number of output voltage levels increases, the method suffers from a high computation burden as a result of a significant number of switching states. In HC‐HNPC based STATCOM, the number of power switches and switching states is reduced compared to CHB STATCOM for an equal number of output voltage levels. As a result, while keeping the number of output voltage levels the same as CHB, the FCS‐MPC computational burden decreases, and the control objectives are achieved easier. Furthermore, HC‐HNPC STATCOM as a hybrid multilevel STATCOM contains different types of cells with different capacitors voltage. Utilizing the introduced FCS‐MPC, each capacitor voltage is kept balanced without using a complex balancing system. For a detailed investigation, a single‐phase 9‐level HC‐HNPC is employed in this research. The FCS‐MPC control is developed for 9‐level HC‐HNPC STATCOM and the mathematical equations are extracted. Finally, the control performance is verified by simulation and validated with experimental results.