Matrix converters can provide unprecedented power densities in bidirectional AC/AC conversion. For the wide majority of applications matrix converters are used as step-down converters as its input capacitors are coupled via low impedances to voltage sources. However, several applications such as electrical generators or solid-state transformers could benefit from step-up capabilities where the matrix converter may operate as a grid forming converter. Still, matrix converters in boost mode operation behave as non-minimum phase systems creating additional control challenges. To address these challenges this paper proposes the use of a boost matrix converter configuration with a 3rd order output filter, where input currents and output voltages are tracked with a predictive controller combined with a proportional integral controller to compensate the power losses of the converter.

The increase of renewable energy penetration to the grid is leading to a massive increase in grid connected power converters. Most of these converters use passive filters to mitigate the harmonic content produced by their switching behaviour to comply with international standards. The design of these filters is known to be an arduous task typically involving experienced designers. This work proposes a grid connected filter design methodology which is formulated as a multi-objective optimization problem in a way that a genetic algorithm can be used to attain a desired filter response, while minimizing the energy stored in the filter. The proposed method is applied for the design of the input filter of a grid tied matrix converter. A pareto front is obtained and a filter solution is selected for which simulations are preformed to evaluate the resultant THD.

High-Voltage Direct-Current (HVDC) is an attractive solution to conventional ac transmission systems, to transmit bulk electric power over long distances. Multilevel bipolar back-to-back dual inverters convey advantages to HVDC systems, at the cost of increased difficulties to control the AC currents and DC link voltage. This paper presents a control approach for a bipolar HVDC transmission system based on a dual two-level inverter topology with a multilevel structure. For both multilevel inverter AC sides a model predictive control strategy is designed to control active and reactive power, establishing AC grid currents in the sending and receiving ends. The multilevel converter also guarantees the balancing of the DC bus capacitor voltages. To test the performance and effectiveness of this proposed control strategy, several simulation studies are presented and discussed.

Solid State Transformers (SSTs) are a new type of transformer that uses power electronics and high-frequency transformer to allow better controllability and enable bidirectional power flow, while providing a high-power density and also a variety of different power quality services. This paper improves the dynamic performance of a three-stage medium to low voltage SST by proposing non-linear controllers, based on Lyapunov’s direct method and Sliding Mode theory, for each of the three stages of power conversion. Simulation results under three different scenarios are analyzed: 1) Voltage sag mitigation; 2) Parameters change; 3) Reverse power flow. Comparisons to standard linear controllers are included.

A leakage tolerant commutation method is proposed that enables the use of matrix converters in Solid State Transformers with three-phase high/medium frequency isolation transformers. Typical commutation methods for matrix converters such as two and four step commutation methods are not suitable in the presence of leakage inductances since they do not allow the recirculation of the leakage energy, this means that when using such methods it is necessary to use snubbers and clamping circuits to mitigate potential overvoltages on the transformer. The proposed commutation method does not require any additional circuitry and is suitable for multiphase converters. A systematic description of the process is provided along with simulation results that validate the proposed commutation method.

A novel structure of matrix-converter-based Smart Transformer (MC-ST) is proposed for hybrid microgrid applications. The conventional ST structure in hybrid microgrid normally consists of two different kinds of modules: cascaded H-bridges (CHBs) and dual active bridges (DABs). For reliability and simplicity, the modularity concept is employed in the proposed structure to obtain only one kind of module. Utilizing the feature of matrix converters as the universal converters, the proposed ST can transfer AC input to AC output as well as to DC output using the same module and same modulation method. Moreover, in order to implement the proposed ST, feedback control of low voltage AC (LVAC) and low voltage DC (LVDC) is implemented. Simulation results show that the proposed MC-ST is feasible and has a potential application in the future hybrid microgrid.

In this work a novel topology featuring an Indirect Matrix Converter (IMC) supplying a three-phase open-end 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.

Wideband-gap semiconductor devices are rapidly gaining ground in power converters in a wide variety of applications, given their ability to block higher voltages, compared to typical devices, with lower on-state voltages. The characterization of losses for Gallium Nitride (GaN) or Silicon Carbide (SiC) semiconductor devices, in particular for inverter operation, is not straightforward, specially taking into consideration that the typical losses values provided by manufacturers are obtained in direct current (DC) for a given current and voltage. This paper measures the average dissipated power in inverter operation for different input voltages and different output currents of two promising devices, SiC MOSFET and GaN HEMT, chosen from two leading manufacturers. The losses measurement is obtained indirectly by the direct measurement of the devices temperature.

This paper presents a novel control approach for a Dual Active Bridge (DAB) converter interconnecting a telecom isolated DC microgrid (IDCM) to a 380 V DC grid. A DAB converter is the ideal solution for this interconnection because it provides galvanic isolation, allows reversible power flow, and can operate with inherent soft switching, leading to high efficiency performance. The novel controller is based on Lyapunov's stability theory and adds integral terms to stabilize the IDCM nominal voltage. The new controller ensures the IDCM fast and stable transient response upon the connection of constant power loads (CPLs). In order to highlight the advantages of the new controller, comparisons using MATLAB/Simulink simulations are made with cascaded voltage/current linear controllers, their limitations being shown. Results point out that the novel controller is able to deal with the negative incremental resistance of CPLs, without the need of bulky stabilizing DC capacitors.

In this paper, a Multi-Terminal Matrix Converter (MT-MC) is proposed for a Battery Energy Storage System (BESS). The proposed MT-MC enables the connection of multiple batteries allowing their independent control. A nonlinear Predictive Optimal Controller is proposed to manage independently the charge/discharge process of the batteries and guarantee the connection to the grid with nearly unitary power factor. The validation of the proposed system is performed through simulation in MATLAB/Simulink. Simulation results show the high performance of MT-MC for two batteries at different operation scenarios allowing charging of one battery while the other is discharging, still guaranteeing current THD lower than 5% in the connection to the grid.