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- Input output linearization and PI controllers for AC-AC matrix converter based dynamic voltage restorers with flywheel energy storage: a comparisonPublication . Gamboa, Paulo; Silva, J. Fernando; Pinto, Sonia; Margato, ElmanoThis paper presents the theoretical development and performance of novel Input-Output Linearization (IOL) AC voltage controllers applied to Dynamic Voltage Restorers (DVR) with Flywheel Energy Storage (FES). IOL performance is compared to decoupled proportional integral (PI) controllers, both relying on a backward Euler predictive current controlled AC-AC matrix converter. The critical load AC decoupled voltage control using IOL or PI is detailed as well as the backward Euler predictive current control. The matrix input and output current tracking control uses a backward Euler predictive current control minimizing a weighted cost functional. The stable backward Euler matrix vector estimation enables the AC-AC matrix to perform as a current tracking converter. Experimental results are obtained using a laboratory level DVR fitted with FES device made from a vertical axis rotating seamless steel hollow cylinder (flywheel) storing kinetic energy. The flywheel is coupled to a Permanent Magnet Synchronous Machine (PMSM) motor/generator, which is driven by the AC-AC matrix converter. The DVR was tested to mitigate voltage sags in isolated neutral critical loads, using IOL and PI controllers. The DVR is able to compensate the critical load voltage without noticeable delays, voltage undershoots or overshoots, overcoming the input/output coupling problem of matrix converters. IOL controller proves to be faster and more aggressive than the PI controller, which is softer introducing less voltage distortion.
- A Novel Multilevel T-Type Indirect Matrix Converter for Three-phase Open-end AC LoadsPublication . Bento, Alexandre; Luís, Ricardo; Pinto, Sonia; Silva, J. FernandoIn this work a novel topology featuring an Indirect Matrix Converter (IMC) supplying a three-phase openend load is proposed to allow multiple levels of voltage while reducing common mode voltages (CMV) at load terminals. The topology features a T-Type three phase inverter connected to the grid neutral terminal, allowing phase to phase or phase to neutral voltages to be supplied to the load. A comparison with the already known IMC open-end load scheme, based on two voltage source inverters (VSI), is performed achieving promising results in terms of Common Mode Voltage reduction at the load terminals, while achieving current waveforms with lower distortion. The improvement of CMV waveforms is useful for motor drives, reducing drive bearing currents and increasing overall lifespan.