Direct Voltage Measurement for Sensorless Control of Single-Stage Current Source Inverter in Motor Drive Applications

Current source inverters (CSIs) offer an alternative to voltage source inverters (VSIs) for electric motor applications. CSIs have some advantageous characteristics, such as the ability to inherently boost voltage, the absence of electrolytic capacitors, and reduced voltage stress on the machine. However, the increased component count and the need for a pre-stage to control the inductor current have limited the adoption of CSIs. For applications that must operate above a base speed, such as more electric aircraft (MEA), single-stage CSI converters are a promising solution. The ability to directly measure the terminal voltages allows for a simple and robust sensorless control approach to be used with this power converter. This approach based on a phase-locked loop (PLL) directly connected to the voltages with a feedforward compensation that depends on voltage drops on Rs and L0 is compared against a back-EMF (BEMF) observer. If a machine with an anisotropic rotor is used and the impedance is small, the feedforward compensation can be neglected leading to the classical PLL. Experimental results on a CSI7 converter driving a permanent magnet synchronous machine (PMSM) report that this kind of sensorless control can be a suitable alternative in motor drive applications.