Abstract
To improve the robustness and performance of the dynamic response of a cage asynchronous motor, a direct torque control (DTC) based on sliding mode control (SMC) is adopted to replace traditional proportional-integral (PI) and hysteresis comparators. The combination of the proposed strategy with sinusoidal pulse width modulation (SPWM) applied to a three-level neutral point clamped (NPC) inverter brings many advantages such as a reduction in harmonics, and precise and rapid tracking of the references. Simulations are performed for a three-level inverter with SM-DTC, a two-level inverter with SM-DTC and the three-level inverter with PI-DTC-SPWM. The results show that the SM-DTC method achieves better performance in terms of reference tracking, while adoption of the three-level inverter topology can effectively reduce the ripples. Applying the SM-DTC to the three-level inverter presents the best solution for achieving efficient and robust control. In addition, the use of a sliding mode speed estimator eliminates the mechanical sensor and this increases the reliability of the system.
Highlights
In recent years, there has been an increasing demand for the use of multi-level converters in power electronics applications
The direct torque control (DTC) method with constant switching frequency based on sinusoidal pulse width modulation (SPWM) has been presented to circumvent the aforementioned drawbacks, as this strategy is based on PI regulators
This paper presents a DTC method based on sliding mode control (SMC) which is one of the robust and nonlinear strategies widely used in the field of electric motor drives
Summary
There has been an increasing demand for the use of multi-level converters in power electronics applications. This paper presents a DTC method based on sliding mode control (SMC) which is one of the robust and nonlinear strategies widely used in the field of electric motor drives This technique is characterized by good dynamic performance since it forces the system trajectory to move along the sliding surface according to a control law whose stability is verified analytically by Lyapunov theory [12]. 3.1 Stator flux and torque control The main task of the variable structure controller, illustrated, is to obtain a fast and reliable control of the torque and the stator flux For this reason, two sliding mode controllers with PI regulators are designed, and the direct and quadrature reference voltages are obtained at the output of the controller to generate the SPWM. Variations in the amplitude and frequency of the reference voltage modify the generated pulse patterns which determine the inverter output
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