This paper discusses the energization and start-up process of modular three-stage Solid State Transformers (SSTs) based on a cascaded H-bridge (CHB) topology. A key element of the SST is the Auxiliary Power Supply (APS) feeding the auxiliary circuitry. Redundancy and simpler implementation can be achieved by powering the APSs from the cells DC-link capacitors, but at the expense of a more challenging start-up process of the SST. The first steps of this process must be performed before APSs are operative. This can result in undesired transient events (inrush currents, voltage sags in the capacitors voltages, etc.) which could prevent proper start-up of the SST or even jeopardize the power devices or other elements. A simple strategy for the energization and start-up of SSTs using this APSs structure is proposed. The method is valid both for grid-forming and grid-feeding operation of the SST, regardless of the energization port and without the addition of any extra circuitry. Simulation and experimental results are provided.
Grid-connection and startup of solid state transformers (SST) based on modular topologies are studied in this work. A simple solution is implemented to feed the auxiliary electronics (i.e. sensors, control boards, drivers, etc.) of each SST module. It is based on feeding this circuitry from the DC links of the module using Auxiliary Power Supplies (APS). However, this structure leads to a problematic energization of the SST due to the threshold input voltage of the APS. Before the DC link capacitors are charged to this voltage threshold, the APSs are not functional and consequently SST energization and connection to the grid are performed without monitoring. Although startup in this situation is problematic, adequate procedure can prevent unwanted transients. In this paper, a step-by-step simple procedure is proposed for energizing a three-stage SST based on a Cascaded H-Bridge (CHB) modular topology. Simulation results as well as experimental tests are presented.
This paper reports the development of a control system for a three-phase power stage for an induction motor as well as for an RLC load, able to synchronize with a virtual grid. Vector current control strategy has been applied in both cases, although Volts-Hertz control method is also available in the case of driving the motor. The project includes the implementation of a control software in a DSP board as well as the development of a PCB that interfaces the inverter with such a platform. Several experimental results for both applications will be presented.
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