Constant Torque Operation Research Articles

A modified CPS-PWM for capacitor voltage reduction of MMC based variable speed drive

<span>In recent years, modular multilevel converters (MMC) have become one of the most popular multilevel converter topologies. Despite its growing popularity, MMC is still less widespread in variable speed drives (VSDs) applications. The reason for this is that the voltage ripple of the MMC submodules (SM) increases during the low-speed constant torque operation. In this paper, carrier phase shift-pulse width modulation (CPS-PWM) is modified to reduce the average voltage of SM and thus accommodate more ripples without exceeding the maximum SM voltage. The proposed method does not involve the injection of circulating current components, thereby resulting in less power loss. In addition to that, the necessity for increasing the SM capacitor rating during low-speed operation is not required. Extensive simulation has been conducted under various speed commands to validate the effectiveness of this method.</span>

Investigation and Calculation of Electric Scooter Electromechanical Characteristics

The design of an electric scooter is presented. The advisability of using an inverted motor with an external rotor, which is part of the wheel, is shown. Permanent magnets producing a large number of pole pairs are installed on the rotor inner surface facing the air gap. With such design, low scooter motion speeds can be obtained without the need of using mechanical gearboxes. The choice of the rotor main dimensions based on the specific tangential force is considered. The stator consists of a core body with a winding, usually a three-phase one. In scooter motors, it is advisable to use a concentrated winding with a fractional q, which is wound around the tooth to form a separate coil on it, belonging to one of the phases. In such winding, the end turns do not intersect; its end-winding parts are much shorter than they are in distributed windings. The stator winding is powered by an inverter controlled synchronously with the rotor rotation. The considered electromechanical converter is nothing but a conventional synchronous machine. Constant torque operation is not typical for the scooter motor. When the user changes the scooter operation mode, for example, in changing over to another track section, all processes develop similarly to those that take place in conventional DC motors. To confirm this, the calculation of the motor is given, and its parameters are determined. An algorithm for calculating the scooter mechanical and performance characteristics has been developed.

Sensor-less vector control of induction motor at low-speed operation using modular multilevel converter

ABSTRACTModular Multilevel Converter (MMC) is widely known as one of the most promising topologies for high power medium voltage application. However, MMC is still limited when it comes to Variable Speed Drive (VSD) applications. The reasons behind this is the large fluctuations in the submodules capacitor voltages during low-speed constant torque operation. Thus, the feasibility of sensor-less vector control of MMC based variable speed drive is considered as a difficult task. This paper proposes a novel speed observer for MMC-based VSD suitable for low-speed operation. Speed estimation is carried out by using the stator currents and the input voltages. A discrete model where the rotor parameters do not change during a short sampling time is considered. An extensive simulation is carried out for verifying the closed loop operation of the proposed speed sensor -less MMC-based VSD.

Dynamic control of electronic differential in the field weakening region

ABSTRACTA simple and dynamic electronic differential control method for an outer rotor motor driven electric vehicle based on fuzzy gain scheduling of PI gains method is proposed for constant torque and power region operation using brushless direct current (BLDC) machine. The proposed method is quite insensitive to torque fluctuations and transient speed oscillations due to surface mounted permanent magnet (SMPM) BLDC machines constraints in the field weakening region. To improve the dynamics and stability of the electronic differential system and eliminate the skidding of the wheels and reduce the heating of electric machine in the wide speed range operation, a robust control method is developed. Moreover, PI controller gains are updated continuously by fuzzy gain scheduling approach which has phase advance angle, steering angle and measured speed as controller input parameters in order to eliminate the errors caused from the variable road conditions and torque oscillations in the field weakening region. The proposed method is implemented with 2 × 1.5 kW BLDC motor drive controlled by a TMS320F28335 digital signal processor (DSP). The experimental results show that the proposed method exhibits greater stability under various load, road and vehicle speed conditions.

Advanced Angle Field Weakening Control Strategy of Permanent Magnet Synchronous Motor

The conventional field weakening algorithm is more dependent on parameters and computational complexity. Therefore, the concept of advanced angle β is introduced, and the conversion of constant torque operation mode to field weakening operation mode is realized by increasing β . In this paper, the conventional field weakening control and advanced angle field weakening are modeled and simulated showing results that the advanced angle field weakening control can make the motor switch smoothly between the constant torque operation mode and the field weakening mode. The dependence of the parameters of the motor is small and the algorithm is simpler. At the same time, the theory of field weakening control of permanent magnet synchronous motor is fused in the vehicle control and the controller is developed. The external characteristic curve of the motor is calibrated by setting up the back-to-back motor test bench. The function of the controller is verified by hardware-in-the-loop experiment. After vehicle verification, it is confirmed that the data can normally enter the field weakening zone to meet the torque response and high-efficiency range. Under the new European driving cycle (NEDC) operating conditions, the efficiency of the whole controller can reach 81.97%.

Sensorless air-gap field orientation controlled induction motor drive with constant torque and constant power operation mode

Sensorless air-gap field orientation controlled induction motor drive with constant torque and constant power operation mode

Time-Division Multiplexing Wireless Power Transfer for Separately Excited DC Motor Drives

This paper proposes and implements the concept of time-division multiplexing (TDM) wireless power transfer (WPT) for separately excited dc motor drives. Essentially, the proposed WPT system has only one transmitter that can transfer power to multiple receivers simultaneously while the power transfer to individual receivers can be independently controlled. Thus, the armature and field currents of the separately excited dc motor can be independently controlled, hence achieving the desired constant torque operation and constant power operation. The key is to make use of the TDM scheme to simultaneously transfer powers to both the armature and field windings. Meanwhile, the burst firing control method is incorporated to independently regulate the power flows to the armature and field windings at the resonant frequency, hence retaining the maximum power transfer efficiency. Both finite element analysis and experimentation are given to verify the validity of the proposed system.

A Novel Optimal Current Trajectory Control Strategy of IPMSM Considering the Cross Saturation Effects

Abstract: The nonlinearity and uncertain variation of machine parameters are always caused by cross coupling and magnetic saturation effects, which are easily neglected in the conventional control strategy. In this paper, a current trajectory control strategy (CTCS) is proposed to take the cross coupling and magnetic saturation effects into account under voltage and current constraints. It can be considered as a calculating method considering parameter variation and separating among each iteration step which treats the calculated result of the former step as the initial value of the next step. At first, the torque command is translated into the current reference. Then, the increments between the target value and real value of the torque and the voltage are respectively calculated, which are subsequently converted into the current modification vector in did, diq framework for further analysis. In order to take the influence caused by cross coupling and magnetic saturation effects on the CTCS into consideration, self and mutual inductances are analyzed by finite element analysis (FEA). The results of the simulation and experiment show that the rapid response and robustness on reference speed variation could be achieved by employing the proposed CTCS, and the seamless switching between the constant torque and flux-weakening operation can also be realized.

Simulation and Performance of AC Drives Using SVPWM Technique

Drives are mainly categorized into constant-speed and variable-speed drives. AC machines have been used in constant-speed applications, where as DC machines were preferred for variable speed drives. Due to the advancement in power semiconductor devices and microprocessors, AC machines are widely used in variable speed drives. This paper focuses on the simulation and performance evaluation for an ac drive system with Induction motor and PMSM Motor. The focus was based on the simulation of the power circuits using MATLAB/SIMULINK software. The performance of inverter was studied by SVPWM technique. Space Vector Pulse Width Modulation (SVPWM) is a digital technique, which increases the output voltage capability and increases DC bus utilization voltage. The performance of an ac drive system was simulated and evaluated for variable speed operation from no load to rated speed under constant torque operation. The advantages and disadvantages of Induction motor and PMSM are analyzed and presented in this paper.

A Novel Torque Controller with Direct Flux Control for Permanent Magnet Synchronous Motor

Permanent-magnet synchronous motors (PMSMs) are expected to generate a desired torque with high dynamic performance in most traction drive applications. The limitation of current and dc link voltage of a given inverter impact the maximum torque generating capability and the maximum speed with rated torque capability. The paper designs a torque controller directly from a coupling system model for PMSM by using a triple-step nonlinear method, in which the air gap flux control is considered explicitly. From the application point of view, the robustness analysis is discussed for the proposed controller. Finally, the proposed control scheme is carefully verified by simulations. The simulation results show that the proposed nonlinear triple-step controller has a comparative control performance with a widely used controller, and also show that the transition from the constant-torque operation region to the constant-power operation region is straightforward and effective during flux-weakening control.

The Research on Full-speed Field Weakening Control Method of Electric Vehicle Interior Permanent Magnet Synchronous Motor

The motor drive system represents a key technology for development of the electrical vehicles, and the permanent magnet synchronous motor becomes the mainstream of the new energy vehicle drive motor for the superior performances in power density, low-speed torque density, efficiency and reliability. The paper studies the field weakening control strategy for the interior permanent magnet synchronous motor (IPMSM) and provides a field weakening control strategy for the IPMSM at the full-speed range. By studying the mathematical IPMSM model and the methods of conventional vector control and analyzing the operating conditions of the IPMSM at the full-speed range, the paper divides the operating conditions into constant torque operation region I, constant torque operation region II, constant power field weakening operation region and high-speed field weakening operation region to confirm the control strategy algorithm in each region and the transition conditions between regions and provide the current control strategy that the d-axis current and q-axis current are confirmed by the reference torque and the feedback speed. Modeling of the field weakening control strategies in each region is made through the Matlab/Simulink, and simulation of the operating conditions with a steady-state load and a dynamic load is done to verify that the field weakening control strategy in each region is feasible. A co-simulation is made by combining the Matlab/Simulink-based control model, the RecurDyn-based virtual prototype and the RT-LAB to verify the feasible field weakening control strategy.

Interior PM Motor Torque Control and Performance Analysis Considering Saturation and Cross Magnetization Effects for Electric Traction

In this paper, a detailed analysis over a reference electric vehicle’s drive cycle of an interior Permanent Magnet Synchronous Motor (IPMSM) is implemented, in terms of motor performance, efficiency and field weakening capability. Initially, the electromagnetic field characteristics of a geometrically optimized IPMSM are investigated for various modes of operation by using a 2-D Finite Element (FE) model. In a next step, a robust hybrid torque control model, combining direct Maximum Torque per Ampere (MTPA) control, for constant torque operation and Voltage Constraint Tracking (VCT), for Field Weakening (FW) operation is developed. For proper IPMSM control, the proposed model considers motor magnetic saturation and cross coupling effects between direct (d) and quadrature (q) axes, including the inductance variation with both d and q axes current. Finally, the effectiveness of the control model has been validated through New European Drive Cycle (NEDC) operation for the investigated vehicle.

Microcontroller based Stator Winding Resistance Determination of Induction Motor Drive on Temperature Variations

In this paper an experiment has been conducted to determine the online stator winding resistance of an induction motor, in industries as well as domestic purpose induction motors is largely utilized, as it has both applications of variable and constant torque operation nature. The major requirement of an electric drive system is its independent control of torque and speed; this is achieved in DC motor Drive but has more disadvantages. With the help of fast acting switching devices it is possible to independently control an induction motor. To control an induction motor drive various methods are available, direct torque control of induction motor is one of the best method of control compared to other, the only disadvantage is the torque ripple. Stator resistance is one of the parameter for the cause; hence its determination is essential. An experiment is conducted at various loads on an induction motor and then the temperature in the stator winding is noted at different instants using microcontroller, from the tabulated readings stator winding resistance is calculated and compared with the direct measurement by Volt-Ampere method. Further it is suggested that by implementing the actual online value of stator resistance of an induction motor dive torque ripple can be minimized .

Comparison of Induction Motor and Line-Start IPM Synchronous Motor Performance in a Variable-Speed Drive

This paper presents an in-depth comparative analysis of the variable speed drive (VSD) performance between an IEC frame size 90 four-pole three-phase induction motor (IM) and the equal line-start interior permanent magnet synchronous motor (LSIPMSM). Employing measurement data from no-load tests, load tests, and temperature-rise tests of the aforementioned motors and different cage materials as well, the motors' no-load and load characteristics are first examined in detail and then the drives' characteristics are analyzed in open-loop volts per hertz ( <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i> / <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</i> ) control by using the same voltage-source inverter and the aforementioned IM or LSIPMSM in both constant torque and constant power operation. It has been established that particularly the motors' current and power factor characteristics have distinct impact on the consequent VSD performance in terms of loss and efficiency. Furthermore, it has been shown that the lower loss of the LSIPMSM enables a significant increase of the VSD's constant power range.

Coreless Dual-rotor Disc Hysteresis Motor, Modeling, and Performance Prediction

Due to their robust structure, low and constant starting current, constant torque, and smooth and noiseless operation, small- and medium-sized power rating hysteresis motors are commonly employed in high-speed applications. However, hysteresis motors, in general, have a comparatively low power factor, efficiency, and torque density. In this article, a new structure, the coreless dual-rotor disc hysteresis motor, is introduced. Electromagnetic field analysis of the machine is performed, and its steady-state equivalent circuit is deduced. An algorithm employed in a computer simulation predicts the operating characteristics of the new machine. In comparison with common hysteresis machines, the superiority of the coreless dual-rotor disc hysteresis motor in regards to efficiency and power factor is revealed. Moreover, a sensitivity analysis is accomplished, and impacts of some structural parameters on the performance of the machine are illustrated. Simulation and a few experimental results for a prototype machine are given, and these validate the equivalent circuit and proposed model of the coreless dual-rotor disc hysteresis motor.

Comparison of the mariner Schilling rudder and the mariner rudder for VLCCs in strong winds

A simulation model of a very large crude carrier (VLCC) with either a mariner type Schilling rudder or a mariner rudder was developed from captive and free-running model tests. Kijima’s regression formula was used to predict the hydrodynamic hull forces on the VLCC. To simulate full-scale maneuvering at cruising speed, the constant torque operation of the main engine was assumed. Considering the higher normal lift force and maneuverability of the mariner type Schilling rudder as compared to the mariner rudder, the size of mariner type Schilling rudder is kept smaller as compared to mariner rudder. To compare the efficiency of the two types of rudder system, maneuvering simulations at constant engine torque and course-keeping simulations at various gusting wind speeds and encounter angles were carried out. Based on the simulation results, the two rudder types were compared from the viewpoint of maneuvering and fuel efficiency in windy conditions.

Optimization of Single-Phase Induction Motors— Part I: Maximum Energy Efficiency Control

This work investigates the problem of efficiency optimization in capacitor-run single-phase induction motors. The double-revolving-field concept is employed in the theoretical analysis and a relation between the main and auxiliary stator currents is derived that accomplishes optimal efficiency under constant torque operation. A triac-based drive with an optimal efficiency voltage controller is proposed. The controller is easily implemented since an experimental procedure is used for adjusting its parameters. Moreover, the proposed control scheme satisfies all of the prerequisites of simplicity, reliability, and cost-effectiveness that are imposed by the utilization of a single-phase motor. Several experimental results are presented to validate the effectiveness of the proposed efficiency optimization control method.

Variable flux control of permanent magnet synchronous motor drives for constant torque operation

In this paper, a small signal model of permanent magnet synchronous machines is developed which includes both components of torque, i.e., magnet torque and reluctance torque. The effects of flux variations on the torque are analyzed by the use of the developed model. The off-line torque compensation method proposed for induction machines is then adapted to permanent magnet motor drives to achieve a constant torque, variable flux operation of the drives. A sensitivity analysis is performed to show that the off-line method is influenced considerably by machine parameter variations. Therefore the concept of forced compensation is introduced and an on-line torque compensation controller is proposed. Simulation results are presented to show the effectiveness of the proposed controller. An experimental vector controlled permanent magnet motor drive including the on-line torque compensation controller is implemented based on a TMS320C31 DSP to evaluate the method. The experimental results also confirm a desirable variable flux control of the motor drive under constant torque operation.

Flux and torque control of switched reluctance machines

The theory and implementation of a flux-linkage controller applied to a switched reluctance machine drive are described. Analysis of the simplified discrete time load model shows that a simple flux-linkage controller can produce a ‘dead-beat’ system response. Comparison of the response from a discrete time PID current controller, hysteresis current controller and the new flux-linkage controller, show that the flux controller has a much improved response. The experimental controller is used to control an IGBT converter, driving a commercial 7.5 kW switched reluctance motor. A method of constant torque operation is introduced. This takes account of limitations imposed by the finite DC-link voltage and rotor speed when calculating the reference values. The method is based on ‘flux ramps’, where the ramps are chosen to give constant shaft torque, and remain within the capabilities of the power converter. Correct selection of the flux ramps allows constant torque operation to be achieved over a wide speed and torque range. Measured results for the experimental drive demonstrate the low torque ripple achieved for motoring and generating operation over a range of speed and torque values.

Analysis and design of microprocessor-based vector-controlled induction motor drives

The design and implementation of controllers for induction motor drives under vector control is considered. The control of induction motor drives is considered in both constant torque and constant horsepower operation regions. A systematic mathematical formulation is presented for designing motor controllers. These include conventional proportional-integral controllers and more advanced frequency-domain optimal controllers. A 32-b microprocessor-based experimental control system is implemented for verifying the proposed control strategies. The theoretical results are validated by the experimental work.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>