Discontinuous Modulation Based Active Thermal Control for Enhancing the KVA Limit of Three-Phase Inverters

The kVA limit of a power electronic converter (PEC) is often limited to keep the junction temperature Tj within a safe operating area (SOA). Therefore, controlling Tj with advanced algorithms such as Active Thermal Control (ATC) methods is a promising way to increase the kVA limit of PEC without sacrificing their reliability, which has not been explored enough in the literature. Therefore, this paper presents a novel approach combining the discontinuous pulse width modulation (DPWM) strategy with a system-level current controller. The proposed method enables the grid-connected inverter-based resources (IBR) to increase its kVA limit without increasing the Tj. This method also allows the converters to operate at higher ambient temperature Ta for more efficient power transfer without sacrificing its power handling capacity. Additionally, this paper systematically explains the effect of DPWM on switching losses Psw by establishing an analytical relationship between the bus clamp angle α with respect to Psw. Furthermore, for controlling the Tj, a simple Foster thermal model-based temperature estimation method is described, and its accuracy has been shown. Additionally, the impact of the proposed ATC method on maintaining the Tj of a 3Ph 2L-VSC with respect to the conventional sinusoidal PWM method is also compared.