Medium Voltage Induction Motor Research Articles

Gradient-Based Predictive Pulse Pattern Control with Active Neutral Point Potential Balancing for Medium-Voltage Induction Motor Drives

Gradient-Based Predictive Pulse Pattern Control with Active Neutral Point Potential Balancing for Medium-Voltage Induction Motor Drives

Stability Issues in V/f Controlled Medium Voltage Induction Motor Drives Considering Magnetizing Inductance Variation

Stability Issues in V/f Controlled Medium Voltage Induction Motor Drives Considering Magnetizing Inductance Variation

Assessment of Multi-Phase Conversion and Modified PWM Strategy for Power Converters of Medium-Voltage Induction Motors Drive

Multi pulse and multilevel converters show great potential for use in medium voltage induction motor drive systems due to cascaded design and high-quality output. However, variable-speed medium voltage drives have demanding requirements in enhancement number of pulses with less number of DC sources and converter topologies with reduced component counts. This paper utilizes the phase displacement technique as well as the three-phase to five-phase conversion technique so that the drive system extracts 30-pulse current from the grid supply, which helps to enhance the power quality at the grid end. In this paper, a 30-pulse AC-DC converter based on a 10-pulse converter is designed and implemented to feed a power 4-level cascaded inverter through three DC sources. Apart from this, a modified carrier-based LSPWM technique is used to enhance the performance of the MLI at a low switching frequency. An indirect field-oriented control (IFOC) method is utilized to address the issues of the drive system during dynamic operations. Performance analysis through theoretical and simulation by using the full-scale model is evaluated in terms of voltage and current quality, speed and torque response, losses, and efficiency. Experimental verification is also carried out on a 7.5kW, 415V laboratory prototype using a digital signal controller for implementation of the control scheme.

Long-Horizon Robust Direct Model Predictive Control for Medium-Voltage Induction Motor Drives With Reduced Computational Complexity

This paper proposes a long-horizon direct model predictive control (MPC) with reference tracking for medium-voltage (MV) drives that achieves favorable steady-state and transient behavior. However, as MPC is a model-based method, it is susceptible to parameter mismatches and variations of the machine. Moreover, even though a long prediction horizon significantly improves the steady-state behavior of the drive, it significantly increases the computational complexity of the direct MPC problem, rendering its real-time implementation a challenging—if not impossible—task. Motivated by these shortcomings of long-horizon direct MPC, this paper also aims to address them by enhancing the robustness of the developed control strategy, while keeping its computational complexity modest. To achieve the former, a prediction model suitable for MV drive systems is adopted that facilitates the effective estimation of the total leakage inductance of the machine. For the latter, the objective function of the MPC problem is formulated such that, even though the drive behavior is computed over a long prediction interval, only a few changes in the candidate switch positions are considered. The effectiveness of the proposed modeling, control, and estimation approaches is validated with hardware-in-the-loop (HIL) tests for an MV drive consisting of a three-level neutral point clamped (NPC) inverter and an induction machine (IM).

Dynamic Model of Medium Voltage Vacuum Circuit Breaker and Induction Motor for Switching Transients Simulation Using Clark Transformation

A derivation of the dynamic model of a medium voltage vacuum circuit breaker and induction motor in space vectors in coordinates αβ0 allow us to model switching transients in various dynamic states of the motor. In the case of the Clark transformation, the corresponding numerical integration technique can be selected including variable time-step integration techniques to avoid numerical instabilities due to the stiffness of the system. Assymetrical operations such as switching cause the power system to become unbalanced and the transformed equations α, β, and 0 are not uncoupled. Therefore, it is necessary to derive a coupling matrix between circuit breaker voltages and currents in the coordinate system αβ0. The subject of our interest is switching overvoltages that arise when turning off small inductive currents by a vacuum circuit breaker. When deriving the model of a vacuum circuit breaker, all its properties encountered during this action are taken into account, i.e., current chop, virtual current chop, dielectric barrier in the circuit breaker and its recovery rate, and the ability of the vacuum circuit breaker to extinguish high frequency currents. Simulation results are compared with the measured results on a medium voltage motor as well as with the simulation results of the mathematical model of the test circuit according to IEC 62271-110 resolved using the nodal method (EMTP algorithm). Models are implemented in the MATLAB/Simulink programming environment.

Study on behaviour of centrifugal pump driven by medium-voltage induction motor during operation control

When studying electric drives, it is necessary to jointly analyze the processes in the electric power and control circuits of the electric motor as the main component determining the overall performance and in the mechanical executive part. The paper deals with the variation of the occurring torques, the currents flowing in the individual phases and the electrical power losses in the operation of a medium voltage electric drive of a pump unit from the point of view of energy efficiency. Emphasis is placed on the joint operation of the pump as a mechanism and the driving electric motor, studying the complete electromechanical system. During the studies, significant attention has been paid to the mathematical description and modeling with subsequent computer simulation of the ongoing electromagnetic and electromechanical processes. Different ways of controlling the motor have been applied - by softstarter and by frequency control. Also values for the duration of the start-up process have been obtained. Relevant conclusions have been drawn.

Design and Analysis of a 54-Pulse Converter and 7-Level Hybrid Inverter for Medium Voltage Induction Motor Drive

Design and Analysis of a 54-Pulse Converter and 7-Level Hybrid Inverter for Medium Voltage Induction Motor Drive

Starting Analysis of Squirrel Cage Induction Motors 1000 kW by Variable Frequency Drive in Power System, Case study: Tabriz Pump station

In petroleum industrial systems, analysis of power systems should be considered to exploit system reliability and prevent change in process performance during starting in equipment such as induction motors and industrial pumps. Medium-voltage induction motors are essential electrical machines in the oil, petrochemical, and process industries; therefore, the study of induction motors is an integral part of the analysis of power system. These motors are directly fed from the power grid and are exploited afterward. The starting current of induction motors is 5 to 7 times greater than the nominal current at the moment of starting until it reaches the nominal torque. This starting current will result in the motors and transformer and voltage drop in users' appliances connected to the electric grid to the extent that it might even cause a shutdown in the grid or not start the motor. It will also directly impact the power quality of the power system. For this reason, the starting voltage drop should not exceed 15% of the terminal voltage. In this paper, the starting of squirrel cage induction motors 1000kW by variable frequency drive in Tabriz pump station has been analysed by the ETAP 19.0.1 software.

The Commercialization of Medium-Voltage Induction Motor Rotor Diagnostics Equipment: Helping Prevent In-Service Failures of Induction Motors and Processes

The R&D process for commercializing diagnostics equipment for detecting rotor faults in MV induction motors is described in this article. This was the result of a five-year collaborative effort among three independent parties: the equipment end user, equipment developer/supplier, and a university research group, where the tasks performed by each party are summarized in <xref ref-type="fig" rid="fig1" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Figure 1</xref> . The steps taken for successful development are given, along with a performance summary of the end product for which the first units have been in field use since 2017.

An 18-Pulse Converter and 4-Level Cascaded Inverter Based Induction Motor Drive

This article presents a topology of an 18-pulse ac–dc and 4-level cascaded converters for a medium-voltage drive application. An isolated transformer-based 18-pulse ac–dc converter is used for enhancing the power quality at the supply end in a medium-voltage induction motor drive. Apart from this, an inverter topology, which is designed by the cascading of a two-level voltage source inverter, is designed for medium-voltage drive applications. This topology requires a smaller number of components in comparison to the hybrid four-level inverter topology, which is presented in the literature. The design of the system is carried out for an 18-pulse ac–dc converter and 4-level inverter feeding an indirect field-oriented control induction motor drive. The effect of switching and conduction losses performance of the presented inverter is analyzed and compared with the profile of the four-level inverter topology presented in the literature. A laboratory prototype of the presented 18-pulse converter and 4-level inverter is also developed to capture the performance in different operating states with a 7.5-kW (10 hp) (reduced scale) induction motor drive. The obtained results justify the practicality of this design and validate the simulated results, which are analyzed on a 298.4-kW induction motor drive. The performances of the drive system are studied based on the industry applications requirements point of view, such as power quality, losses, and dynamic stability.

Modified PWM Technique for a Multi-Pulse Converter Fed Multilevel Inverter Based IM Drive

This article presents a 36-pulse converter and five-level cascaded H-bridge multilevel inverter (CHB-MLI) fed medium voltage induction motor drive (MVIMD) system. The multiwinding transformer (MWT) for a 36-pulse ac–dc converter is designed in such a way that it requires the least number of windings and enhances power quality at the grid end. This is helpful to reduce the size, weight, and cost of the presented MVIMD. The modified carrier level shifted pulsewidth modulation (MC-LSPWM) is used to control five-level CHB-MLI fed induction motor, which adheres the power quality standard IEEE519 at drive end. The main characteristic of used PWM is that it has inherent rotating switching pattern nature, which is helpful to enhance the power quality performance and to decrease the continuous conduction time of the H-bridge. Whereas, this continuous conduction among H-bridges, is not balanced in the level-shifted pulsewidth modulation (LSPWM). Therefore, conduction losses among the H-bridges of CHB-MLI are balanced and reduced by this MC-LSPWM for continuous operation, which is not possible with the conventional LSPWM. The practicality of this MVIMD with an indirect field-oriented control and MC-LSPWM technique, is substantiated via a comparison with the configuration reported in the literature, simulation, and experimentation, respectively. Performance of the drive system is evaluated during different operating conditions, such as starting, steady-state, speed and load perturbations. Further, a detailed comparative analysis of results is presented, which demonstrates that presented MWT configuration has fewer number of windings (only thirty-three windings), less conductor material and minimum losses. Thus, the presented configuration of MVIMD shows excellent performance characteristics with reduced size and weight such as currents total harmonic distortion is 2.5% (grid end), 3.66% (drive end) and efficiency of the drive is 88.101%, when the drive runs at rated conditions.

Harmonic Suppression Scheme for Multipulse Converter Fed Multilevel Inverter-Based IM Drive

The medium-voltage induction motor drives are regularly utilized for crucial application in enormous industries. It is difficult to design a highly efficient drive system with a satisfactory power quality standard not only at the drive end but also at the grid end. To breakthrough this issue, a 36-pulse ac–dc converter fed seven-level binary cascaded H-bridge multilevel inverter (CHB-MLI) based drive system is presented in this work, where a 36-pulse converter is employed to enhance the power quality at the grid end. For this, the phase-shifted technique is implemented on a multiwinding transformer to eliminate the harmonics injected by the nonlinear diode bridge rectifier toward the grid side. Apart from this, the genetic algorithm selective harmonic elimination (GA-SHE) is applied to a seven-level binary CHB-MLI to diminish lower order (fifth and seventh) harmonics at the drive end. Moreover, a GA is adopted to determine the optimized switching angles by the solution of the nonlinear trigonometric equation of SHE. Furthermore, the GA-SHE-based fundamental frequency modulation scheme is favorable to decrease the switching losses and to enhance the drive end converter efficiency. The performance during the dynamics and steady state of the presented drive system with the indirect field-oriented control is analyzed through simulations and experiments on 298.4 kW and 7.5 kW squirrel-cage induction motors, respectively.

Design and Simulation of Modular Multilevel Converter Fed Induction Motor Drive

Traditional modular multilevel converter (MMC) applications in medium voltage induction motor drive are difficult, particularly at low speeds because of the higher magnitude of the voltage ripple of the sub-module capacitor. This paper uses a hybrid MMC, particularly at low frequencies, to achieve a lower peak-to-peak voltage ripple of the sub-module capacitor. The vector control strategy with the closed-loop speed control indicates an accurate and wide-speed range. MATLAB / Simulink is used to simulate and obtain the simulation results of hybrid and traditional MMC with induction motor drive and compare from the standpoint of capacitor voltage ripple. The results are shown the reduction of peak-to-peak voltage ripple of the sub-module capacitor as the hybrid MMC is operated.

Design and Simulation of Modular Multilevel Converter Fed Induction Motor Drive

Traditional modular multilevel converter (MMC) applications in medium voltage induction motor drive are difficult, particularly at low speeds because of the higher magnitude of the voltage ripple of the sub-module capacitor. This paper uses a hybrid MMC, particularly at low frequencies, to achieve a lower peak-to-peak voltage ripple of the sub-module capacitor. The vector control strategy with the closed-loop speed control indicates an accurate and wide-speed range. MATLAB / Simulink is used to simulate and obtain the simulation results of hybrid and traditional MMC with induction motor drive and compare from the standpoint of capacitor voltage ripple. The results are shown the reduction of peak-to-peak voltage ripple of the sub-module capacitor as the hybrid MMC is operated.

A new exact equivalent circuit of the medium voltage three-phase induction motor

This paper proposes a new equivalent circuit for medium voltage and great power induction motors considering the more complete information given by the manufacturer. A methodology for obtaining the parameters of the equivalent circuit is presented, having this circuit the advantage of allowing the electrical calculation of all the power losses and the realization of the power balance. It is an achievement of this work a new way of calculating and representing the additional losses using a resistance located in the rotor circuit. Then, three types of losses are considered as a part of a power balance: the conventional or joule effect variable losses, the constant losses, and the additional losses. The proposed method is straight and non-iterative. It was applied to a case study motor of 6000 V and 2500 kW located at the Maximo Gomez Power Plant in Cuba.

A Sensorless DTC Scheme for 60-Pulse AC-DC Converter Fed 5-Level Six-Leg NPC Inverter Based Medium Voltage Induction Motor Drive

A new approach to improve the power quality of medium voltage induction motor drive (MVIMD) at both utility and drive end is presented. Here, 3-multi-winding transformers (MWT) (T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> , T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> ) are utilized and each MWT converts 3-phase input AC-supply into two isolated 5-phase AC-supplies with unique (18°) phase-shift among them. Moreover, due to unique (±6° and 0°) angle in the primary sides of these MWTs, the line current drawn from the grid has 60-pulses. By applying this technology, the input current harmonics are decreased to well below the requirement of the IEEE 519 standard. This 60-pulse AC-DC converter gives 6-isolated DC-supplies, which are input of a 5-level six-leg neutral point clamped (NPC) inverter feeding an induction motor. A modified direct torque control (DTC) strategy is used in this study for 5-level six-leg NPC inverter fed induction motor drive (IMD). Because of it, this IMD has better performance than the existing IMD. The system performance is evaluated using MATLAB-Simulink software and is then experimentally verified on a prototype developed in the laboratory under all required operation of IMD to validate the performance of the system.

A New Three-Phase to Five-Phase Transformer With Power Quality Improvement in Hybrid-Multilevel Inverter Based VCIMD

This paper proposes a new three-phase to five-phase transformer, with a 30-pulse AC–DC converter for power quality improvement in vector-controlled induction motor drive. Here, three isolated transformers (T1, T2, and T3) are used and each transformer is designed to convert three-phase AC-supply into five-phase AC supply, to achieve ten-pulse AC–DC conversion. A unique configuration and angle among these three transformers is designed in such a way that the resultant input current of this transformer shows 30 pulses in it. A hybrid multilevel inverter is proposed in this paper, which is cascading a three-level neutral point clamped inverter with a two-level voltage source inverter to drive an induction motor (IM). A modified level shifted carrier-based sinusoidal pulsewidth modulation and a 3rd harmonic injection techniques are utilized to modify the modulating signal, to enhance the fundamental magnitude, and to reduce the harmonics than traditional technique. The responses of proposed medium voltage induction motor drive (MVIMD) are evaluated by simulating in MATLAB-Simulink. The proposed MVIMD performance is then verified using a scaled down laboratory prototype under various operating conditions such as steady state, starting, load perturbation, speed control, field weakening, varying load conditions, and over a wide speed range of IM.

A New Method for the Accurate Prediction of On-Load Power Factor in Two-Pole Induction Motors Considering Shaft Eddy Currents

An accurate prediction of medium-voltage induction motor (IM) power factor in rated conditions is important in the design stage to verify the machine compliance with specifications according to international testing standards. Laboratory and industrial experiences suggest that significant errors in full-load power factor calculation can result for two-pole IMs in particular, due to the eddy currents induced in the solid-steel shaft at rated slip. Such eddy currents are responsible for rejecting the main flux into rotor laminated yokes causing an increase in their saturation and, hence, in the required magnetizing current with respect to no-load conditions. This article proposes a method to study the phenomenon through a combination of analytical and simplified Finite Element (FE) calculations as a computationally-efficient alternative to conventional FE simulations. The results of the proposed approach are experimentally assessed by comparison with measurements on a set of built and tested medium-voltage two-pole IMs of different sizes, showing very good accuracy and computational performance.

Suppressing the Capacitor Voltage Fluctuations in Low Frequency Operation of Modular Multilevel Converters

Low frequency operation in the modular multilevel converters (MMCs) is enabled by applying a reference common mode voltage and circulating currents at a frequency much higher than the desired output frequency. The frequency of injected common-mode signals is limited for maintaining a good performance in the circulating current control. Firstly, this paper theoretically analyzes the effect of increasing the frequency of injected common-mode signals by evaluating the error between reference and actual circulating currents. Secondly, we introduce an additional parameter in the reference circulating current to enhance the suppression of MMC's capacitor voltage fluctuations. Intensive computer simulations are developed for a seven-level MMC driving a medium-voltage induction motor drive system to verify the circulating current error analysis and assess the capacitor voltage fluctuations. Finally, the proposed technique for suppressing the capacitor voltage fluctuations is experimentally validated on a 600-V three-level MMC feeding an inductive load. The voltage fluctuations are reduced by more than 50% (63.6%) when the proposed technique is applied with a high common-mode frequency.

Phase-Shifting Transformer Combined with the Novel SHEPWM for Harmonics Reduction in Medium-Voltage Inductive Loads

In this paper, a novel approach is proposed to reduce the impact of harmonics in the high-power medium-voltage squirrel-cage induction motor. An inverter with a minimum switching frequency is required for this load type to reduce the snubber and switching losses. Phase-shifting transformer is selected as an interface between the three-phase supply and the inverter. This is to reduce the impact of low order harmonics and consequently reducing total harmonic distortion (THD). Selective harmonic-elimination pulse width modulation (SHEPWM) is employed as a control technique in the inverter to eliminate specific low-order harmonics. Thereby, many low order harmonics are reduced further. By this way the THD of the system is reduced significantly and consequently the better and cleaner energy is obtained. In this research, PSpice simulation verified by MATLAB is used to estimate the harmonics content of the currents in high-power medium voltage induction motor.