Sensorless control with startup procedure and grid fault detection for three-phase VSI with LCL filter

The use of voltage source inverters in the power grid has many advantages, but cost is always an issue. To reduce the cost, a simple but fast sensorless control method is proposed to eliminate the need for external sensors such as grid voltage measurements. By utilizing information from the sensorless control, line faults such as sag and swell can be quickly detected. An important, but often overlooked topic is startup procedure of sensorless inverters. By simultaneous pre-charge the inverter and estimate grid voltages, the method also works during startup. Experimental results are presented using a fully functional sensorless control laboratory setup.