Chattering-free classical variable structure direct torque controlled IPM synchronous motor drive by using PI controller within boundary layer

In this paper, a novel robust direct torque controlled interior permanent magnet synchronous motor drive is presented which is based on variable structure approach and space vector modulation technique. Basically, it has similar structure as classical SVM-DTC scheme where the linear controllers are replaced with sliding mode type of controllers. In this case, the chattering effect has been addressed by using PI controllers within the specified boundary layers of switching surfaces. Such a combination of sliding mode controller and PI controller has been employed for controlling over stator flux, electromagnetic torque and rotor speed in the proposed direct torque control scheme. In fact, the SMC is in charge of transient response control and PI controller prevails in the steady state. As a result, the lack of robustness in linear controllers is compensated by SMC while the chattering effects and steady state errors of such sliding mode controllers are suppressed by smooth control obtained through PI controllers. The drive performance improvements are also investigated through the presented comparative simulation studies.