Abstract
This paper presents an original method of power loss validation in medium-voltage SiC MOSFET (metal–oxide–semiconductor field-effect transistor) modules of a three-phase inverter. The base of this method is a correct description of the on-state performance of the diodes and the transistors in a PWM (pulse width modulation)-controlled inverter phase leg. Combined electro-thermal calculations are applied to precisely estimate the losses in the power devices and then, to find the suitable circuit parameters of a test circuit to emulate these conditions. A simple square-wave-controlled half-bridge with an inductive load enables the electrical and thermal stresses comparable to these in the inverter, and moreover, provided equations that confirmed the possibility of balancing the load between the diodes and the transistors. The circuit with 3.3 kV SiC MOSFETs was tested to verify the impact of selected parameters on power losses with the main focus on duty ratio. The same module was applied, in addition to an inductive load (3 × 112 μH) and two sets of DC-link capacitors (750 μF), to validate a phase leg of a 220 kVA inverter. In spite of a significantly apparent power, the active power delivered from the DC supply settled around 1 kW, which was enough to emulate 390 W of losses in two transistors and diodes.
Highlights
Nowadays, research works on medium-voltage power conversion with silicon carbide (SiC) power devices can be divided into two substantial parts
Electro-thermal calculations for the selected operating point of a three-phase inverter according to the method presented in Figure 2, using Equations (1)–(8) to find power losses in transistor PT an diode PD
SiC MOSFET modules, a new method of power losses validation was presented in this paper
Summary
Research works on medium-voltage power conversion with silicon carbide (SiC) power devices can be divided into two substantial parts. Even for the resistive load power at a fraction of the high rated power of a medium-voltage converter, this ends in tens of kWs to dissipate in laboratory conditions All these works were carefully studied to find a suitable solution for a very challenging process of medium-voltage SiC inverters design and testing. A novel method using simple measurements in the half-bridge circuit and precise electro-thermal calculations is proposed to emulate the power losses of the module applied in a three-phase inverter. This method and their experimental validation can be counted as a main contribution of this paper. A showcase of the proposed method by means of power loss estimation and validation for selected the operating point of a three-phase inverter is shown in Section 5, while Section 6 concludes the paper
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