The Universality Analysis of Virtual Voltage Injection Method for Different Observers in Speed Sensorless IM Drives

There are three main reasons that result in unstable problem of speed sensorless induction motor drives (SSIMD): unobservable rotor speed at low speed range, unstable poles' placement of the vector control system at low speed range, and poor robustness at low speed range. If and only if these three problems are solved simultaneously, the unstable problem of SSIMD can be solved completely. There are many solutions (observers) being proposed to solve these three problems. However, these observers cannot solve three problems simultaneously. In addition, each solution does not have universality and cannot fit for different observers. There is no generic method that can be applicable to different observers and can solve three problems simultaneously by now. In this article, the universality of virtual voltage injection method is analyzed. It can be proved that virtual voltage injection is a generic, effective, and simple method that can solve three problems simultaneously and can be applicable to different observers. Finally, the feasibility is verified by experiments.