Power Electronics Europe April/May Issue 2022

28 WIND POWER INVERTER DESIGN www.power.com/scale-iflex-lt Issue 2 2022 Power Electronics Europe www.power-mag.com Optimizing the Switching Stage in Wind Power Applications Efficient power conversion is an important part of maximizing the cost-effectiveness of the switching stage in a wind-powered generator. Much effort has been expended in maximizing switching efficiency with excellent results. In this article, we will look at optimizing the utilization of the switches to increase the amount of power that can be processed by a given system. This, in addition to the benefits obtained by optimized switch driving, can show an increase in power throughput for a given system by >20 %. Thorsten Schmidt, Product Marketing Engineer, Power Integrations, Ense, Germany A rapid expansion in wind-powered energy generation has already begun (Figure 1). A typical 10 MW windmill will require up to 40 dual IGBT drivers in the two inverter stages alone. Maximizing DC rail voltage (DC-link) in an inverter Typical wind-power inverter stages employ multiple groups of parallel-mounted IGBT modules (Figure 2), which offer more cost- effective and space-efficient implementation than single, large IGBT units. The factor that controls the maximum DC-link voltage (and therefore power) that can be processed by a given inverter stage is the maximum operating voltage that can be tolerated by each IGBT. The DC-link voltage must be set below the maximum rated IGBT blocking voltage to account for voltage overshoot during shutdown. By more accurately controlling the amount of voltage overshoot, it is possible to reduce the required voltage margin, raise the nominal DC-link voltage and process more power from each IGBT module. Controlled turn-off of the gate driver – ABOVE Figure 1: Anticipated worldwide growth in wind power suggests a >10X expansion of wind power use by 2050 (IRENA 2019d) RIGHT Figure 2: Simplified view of a four- quadrant wind inverter showing multiple parallel switches and their associated gate drivers. Each dual IGBT module processes the same DC-link voltage and (ideally) equally shares current with the other parallel modules