Search

Modern variable-speed drives must be able to deal with ride-through faults with dips of 70–90% to ensure the continuity of the process without the energy store station discharge and carry out significant effects to its performance. So, the existent contingencies to such case are tripping-method from grid, robust DC-Link with higher capacitors and additional power electronic hardware. Nevertheless, they comprehend a common drawback for being costly in the industry. Therefore, the Power Loss Ride Through behaviour on variable-speed drives is an important feature which is a worst-case where the system can suffer dips near to 99% on grid. Recently, Modular Multilevel Cascade Converters have been applied in Variable-Speed Drives applications due to their capability to operate at high-power rates and features such as enhanced fault-ride through capability during critical dip voltage (e.g., 99% of amplitude) in grid. Therefore, this paper presents a control strategy based on a transition mechanism between outer control loops on the nested control of a Modular Multilevel Matrix Converter drive with the aim to improve the Power Loss Ride-Through performance through keeping the energy store station uniform and stable. Simulation results obtained using PLECS software are presented to validate the effectiveness of the proposed control strategy.

This paper proposes a new overmodulation algorithm based on SVM in which the overmodulation region is avoided to reduce harmonic distortion and do not incorporate additional unexpected harmonics. Thereby, when the reference signal exceeds the modulation zone, then the algorithm reduces the fundamental signal component and maintains the magnitude of the reference harmonic components, preventing the reference signal scape from the modulation limits. The algorithm is validated by the simulation of a three-phase voltage source converter operating as a shunt active filter in a three-wire network with a highly inductive and non-linear load.

The three-phase to medium frequency single-phase direct conversion with the Modular Multilevel Converter for Solid State Transformers involves control and modulation challenges due to the switching devices limitations. The use of Nearest Level Control (NLC) as a modulation technique to properly synthesize medium frequency voltages at the output is proposed on this paper, paying special attention to the arm inductors effect at medium frequency operation. Using NLC results in low distortion medium voltage and medium frequency single-phase output, achieving good controllability and reaffirming the suitability of the converter for its application in Solid State Transformers.