Modern Direct Torque and Flux Control methods of an induction machine supplied by three-level inverter

Abstract

Abstract. This paper describes two modern direct torque and flux control methods of an induction machine supplied by a three-level inverter. Additionally, it presents a comparison of the methods both in static and dynamic states. The methods, in a specific way, make use of an increased number of active vectors of the three-level inverter in order to improve control quality and reduce switching frequency. The two methods modify the DTC method by using its advantages and eliminating, at the same time its drawbacks.In static states the comparison was based on the results of investigations performed for two different load values and three set values of angular speed, whereas in dynamic states the comparison was focused on the behavior of the machine at startup.The results of the investigations have shown that both methods give very good performance. They are characterized by both sinusoidal shape of flux and low current deformations even at low angular speeds i.e. less than 10% of the nominal value. The presented methods also allow to generate nominal flux for set zero angular speed in order to achieve excitation of the induction machine. The switching frequencies for both methods are very similar in almost the whole range of control but the methods have shown some differences in control quality, particularly for higher torque values.

Review of recent advancements of direct torque control in induction motor drives – a decade of progress

“…To overcome this, techniques to synthesise intermediate voltage vectors in two‐level inverter [47, 48, 69] and DTC using special converters are introduced. Special converters like matrix converters [44, 94–96, 109–111] and multilevel inverters [49–52, 97, 98, 112–119] provided more voltage vectors for better control options. This allowed to design modified switching table, increased torque hysteresis levels [47, 69] and selecting optimised voltage vector to provide maximum torque rate under dynamic conditions [48] for better controllability and reliability.…”

Bulletin of the Polish Academy of Sciences: Technical Sciences

“…The induction motor control using dc/ac converters has become an interesting area as it pertains to the Field Oriented Control (FOC) and Direct Torque Control (DTC) [1]. Hence, different direct torque and flux control strategies are proposed for induction motors supplied by a three-level inverter [2,3]. A DTC strategy is proposed for a three-phase induction motor fed by a three-phase direct matrix converter, while the motor's behavior can be estimated at the next sampling interval using the predictive control strategy and different matrix converter modes [4].…”

“…Many different controllers such as proportional-integrator controllers [2,[7][8][9], fuzzy logic controllers [10], sliding mode controllers [11], deadbeat controllers [12] have been extensively employed to calculate the components of reference voltage vector. In addition to the use of rotary coordinate transformation, which degrades the quick dynamic response of this method as compared to the conventional DTC, the control effort is calculated through complicated and parameter dependence relations.…”

A state-space approach for control of NPC type 3-level sine wave inverter used in FOC PMSM drive

“…For a specified value of the torque ripple, the weight and overall dimension of LC filter can be reduced if 3-level inverter is used instead of 2-level [7]. Neutral Point Clamped (NPC) 3-level voltage source inverter is a widely used topology of multilevel inverters [8][9][10].…”