Discontinuous Modulation-Based Active Thermal Control for Enhancing the KVA Limit of Grid-Connected Inverter-Based Resources

The kVA limit of a power electronic converter (PEC) is often limited to keep the junction temperature (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$T_{j}$</tex-math></inline-formula>) within a safe operating area (SOA). Hence, controlling <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$T_{j}$</tex-math></inline-formula> with advanced algorithms such as active thermal control (ATC) methods seems to be a promising way to increase the kVA limit of PEC. In this regard, this article presents a novel closed-loop control approach, combining the discontinuous pulse width modulation (DPWM) strategy with a system-level current controller. The proposed method enables grid-connected inverter-based resources (IBR) to increase their kVA limit without violating the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$T_{j}$</tex-math></inline-formula> limit. This method further allows the converters to operate at a higher ambient temperature (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$T_{\rm amb}$</tex-math></inline-formula>) without sacrificing their power handling capacity. An analytical relationship between the bus clamp angle (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\alpha$</tex-math></inline-formula>) with respect to the switching loss (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$P_{\rm sw}$</tex-math></inline-formula>) for DPWM has been explained, which is then used as a control variable for the ATC. For the thermal model, a simple Foster thermal model-based temperature estimation method is described, and its accuracy has been depicted.