Inverter topologies with power modules add efficiency
Efficiency, increasingly important in power electronics, can be improved with neutral point clamped technologies (NPC). Many applications are driven by the initiatives for reduced energy consumption. This can be applied in inverter applications in the solar market, for uninterruptible power supplies (UPS) and for motor drives, which have new targets for improved efficiency.
There are alternatives for 3~ inverters with 700 V dc-link voltage, according to Vincotech. NPC topology offers advantages such as reduced switching losses, smaller output current ripple, and total +/- supply voltage is split. Only half of the voltage has to be switched, and this also cuts the switching losses in the transistor by half.
It is possible to use 600 V components instead of 1200 V types. Also, 600 V technology has much faster components than those available in 1,200 V. This will lead to further reduction of the switching losses. NPC topology will have lower ripple in the output current and half of the output voltage transient. This will reduce the effort for filtering and isolation in the filter inductor. The dc voltage is divided into a positive and negative voltage, which supports the serial connection of dc capacitors without need for leakage current compensation.
Comparing two 3-level topologies and a standard 3-phase bridge shows how neutral point clamped technologies, which are more cost effective, can achieve an efficiency of 98.04% compared to 96.65% of the standard 3-phase bridge.
More NPC inverter topology information is available.
Vincotech is an independent operating unit within Mitsubishi Electric Corporation.