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Torque-speed curve. Linear and nonlinear torque approximations (the solid line corresponds to the actual curve).
Source publication
A novel open-loop speed control method for induction motors that
provides high output torque and nearly zero steady-state speed error at
any frequency is presented. The control scheme is based on the popular
constant volts per hertz (V/f) method using low-cost open-loop current
sensors. Only stator current measurements are needed to compensate for...
Contexts in source publication
Context 1
... exact value of is not generally known, it certainly is a finite quantity and, for a typical NEMA B design, its value lies between 1.5-3. Hence, the use of (13) provides a huge improvement over the linear approximation. To illustrate the difference between (13) and (14), actual and estimated torque-speed curves using both schemes are presented in Fig. 4. A 20% error on has been intentionally added to the nonlinear prediction. If the correct value of were to be used, there would be no error, and the nonlinear prediction would lie on top of the actual ...
Context 2
... shown in Fig. 4, the error introduced by the linear approximation is reasonably small for torques less than rated value, but the error increases very rapidly for larger torques. On the other hand, the nonlinear approach gives much smaller errors, even using an incorrect estimate of the breakdown torque. The difference becomes even more important at ...
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Citations
... To mitigate the high starting current problem of IMs, the V/Hz control (i.e., scalar control) is widely used as a simple and robust induction machine control approach. It is proved that the V/Hz control with the compensated slip frequency from a nonlinear torque-speed approximation reduces the speed error, leading to starting a current reduction [11]. A new control algorithm for V/Hz control of pulse width amplitude modulation (PWAM) with a multilevel quasi Z source inverter (qZSI) achieves starting of IM without the starting current transient [12]. ...
Induction machines (IMs) are used extensively in irrigation systems due to their high reliability and line-starting capability directly from the power grid without requiring variable speed drives (VFDs). Nonetheless, line-connected IMs draw a substantial starting current from the grid, leading to grid instability, heightened demand charges, and premature failures in irrigation systems due to excessive water pressure. Although VFDs can effectively alleviate the starting current, their associated costs for equipment, installation, and maintenance are higher than line-connected IMs. Consequently, this results in limited adoption in the market. This paper proposes a shunt-connected photovoltaic (PV) inverter with a newly devised synchronous scalar control technique to tackle this issue. This system can be retrofitted into existing line-connected IM setups to reduce the excessive initial current effectively. Once the IM attains its rated operating state, the power source is seamlessly switched from the PV inverter to the power grid within two electrical cycles. This minimizes transient currents while ensuring uninterrupted operation of the irrigation system. The PV inverter can supply continuous active and reactive power, resulting in energy savings throughout the year during irrigation and off-irrigation seasons. Moreover, the proposed PV inverter can be dimensioned as small as 50% of the irrigation system, significantly reducing the peak starting current. Simulation and experimental results closely align, demonstrating the favorable soft-starting performance of the inverter.
... Moving on to the control of IMs, the simplest variable-speed drive used to date is a scalar-based controller known as constant Volts per Hertz (V/f). However, its practical application at low frequencies is problematic due to the influence of the stator resistance and the necessary rotor slip to produce torque [14]. Nevertheless, some researchers have sought to improve this control method, like the authors of [15], who achieved current control assisted by V/f control, achieving the elimination of current peaks at the starting phase. ...
Electric vehicles (EV) have gained importance in recent years due to environmental pollution and the future scarcity of fossil resources. They have been the subject of study for many years, where much work has focused on batteries and the electric motor (EM). There are several types of motors in the market but the most widely used are induction motors, especially squirrel cage motors. Induction motors have also been extensively studied and, nowadays, there are several control methods used—for example, those based on vector control, such as field-oriented control (FOC) and direct torque control (DTC). Further, at a higher level, such as the speed loop, several types of controllers, such as proportional integral (PI) and model predictive control (MPC), have been tested. This paper shows a comparison between a Continuous Control Set MPC (CCS-MPC) and a conventional PI controller within the FOC method, both in simulation and hardware in the loop (HIL) tests, to control the speed of an induction motor for an EV powered by lithium-ion batteries. The comparison is composed of experiments based on the speed and quality of response and the controllers’ stability. The results are shown graphically and numerically analyzed using performance metrics such as the integral of the absolute error (IAE), where the MPC shows a 50% improvement over the PI in the speed tracking performance. The efficiency of the MPC in battery consumption is also demonstrated, with 5.07 min more driving time.
... It was revealed that bad performance of sinusoidal pulse width modulation, particularly at low frequency would be overcome by such modification. Considering the impact of slip regulation a V/F speed control method has been introduced in [16]. Simulation results of the suggested control method were experimentally validated and both results ensured the effectiveness of the control method and well regulation was delivered. ...
Induction motor has been widely applied in many sectors, as it has the advantages of simplicity, toughness and can withstand hard environment conditions. The working of such motor in constant voltage/frequency (V/F) speed control method has been popular since the introduction of the power electronic devices, which consequently make the implementation of this method simpler and effectives. The V/F speed control is dominated choice for many applications, especially open loop control and also for closed loop control when the accuracy is not a crucial issue. This study deals with two cases of controlling open and close of the electronic switches. The first with equal intervals by placing regular pulses at the opening and closing periods, and the second using three-phase pulse width generator, through which the control of different periods is carried out according to the required control. Four models have been simulated in this study including, three-phase induction motor at constant torque (constant load) as well as at variable torque (variable load), modeling of PWM-VSI for three-phase induction motor at constant torque (constant load) as well as at variable torque (variable load). The results have shown that speed profile of the IM can be improved by controlling the invertor using PWM technique. Keywords: Pulse-width modulation Speed Three-phase induction motor Torque Voltage source inverter This is an open access article under the CC BY-SA license.
... The control of the motor usually uses constant volts per hertz (V/f), direct torque control (DTC), field-oriented control (FOC), and other methods. V/f control has matured for a long time [5]. It can generate the required torque by coordinating the amplitude and frequency of the stator voltage, which is the simplest motor control strategy. ...
The traditional single current sensor control strategy of a permanent magnet synchronous motor (PMSM) often adopts the DC bus method, which makes it difficult to eliminate the blind area of current reconstruction. Therefore, a current reconstruction method based on a sliding mode observer is proposed. Based on the current equation of the motor, the method takes the α-axis and β-axis currents as the observation objects and shares the same synovial surface, so that the α-axis current observation value and the β-axis current observation value converge to the actual current value at the same time and the unknown β-axis current information is obtained. The control system first tests the performance of the motor under different working conditions when the parameters are matched, and then tests the current reconstruction ability of the parameter mismatch. The results show that the current observer with a matched parameter can accurately and quickly reconstruct the β-axis current under various operating conditions, and the maximum current error does not exceed 4 mA. When the parameters are mismatched, high-performance control of the motor can still be achieved. The proposed method has excellent robustness.
... In addition, the sluggish dynamic output is obtained by voltage magnitude and frequency regulation. By scalar control, the transient output is not enhanced, and it is additionally affected by IM parameter sensitivity [9,15,16]. ...
... Using the both components of stator current and flux, the electromagnetic torque can be evaluated as T e = 3 2 P I qs Ψ ds − I ds Ψ qs (16) With the exception of stator resistance, the stator flux and electromagnetic torque calculations are independent of the machine parameters. ...
This paper introduces a comprehensive examination of vector-controlled- (VC-) based techniques intended for induction motor (IM) drives. In addition, the evaluation and critique of modern control techniques that improve the performance of IM drives are discussed by considering a systematic literature survey. Detailed research on variable-speed drive control, for instance, VC and scalar control (SCC), was conducted. The SCC-based systems’ speed and V/f control purposes are clarified in closed and open loops of IM drives. The operations, benefits, and drawbacks of the direct and indirect field-oriented control systems are illustrated. Furthermore, the direct torque control (DTC) method for IMs is reviewed. Numerous VC methods established along with microprocessor/digital control, model reference adaptive control (MRAC), sliding mode control (SMC), and intelligent control (in terms of fuzzy logic (FL) and artificial neural networks (ANNs)) are described and examined. Uncertainties in the IM parameter are a considerable problem in VC drives. Therefore, this problem is addressed, and some studies that attempted to provide solutions are listed. Magnetic saturation and core loss impact are mentioned, as they are important issues in IM drives. Toward demonstrating the strengths and limitations of various VC configurations, a few experiments were simulated via MATLAB® and Simulink® that show the influence of machine parameter variation. Efforts are made to supply powerful guidelines for practicing engineers and researchers in AC drives.
... In the closed-loop control method, the torque is also controlled. The block diagram of the closed-loop speed control of the drive system is shown in Fig. 3 [22]. The error between measured and desired speed is processed in the PI controller. ...
Because induction motors are used in most industries, IM control is more essential, Optimization is used approaches are becoming more common for improving Three - Phase induction motor (TIM). In addition, the Volt/Hz (V/f) control is utilized to minimize the harmonics level of other control and modulation approaches. This study is about tuning the PI controller parameters for utilization in TIM. To optimize the speed response performance of the TIM, the Particle Swarm Optimization (PSO) algorithm is used to adjust each parameter of the PI speed controller. Kp and Ki of the PI speed controller parameters are optimized for TIM operation with V/f Control by designing an appropriate PSO algorithm. The PI speed controller's performance on the TIM is measured by measuring changes in speed and torque under-speed response events. In PSO, the PI controller performs well in terms of overshoot, settling time, and steady-state error”.
... In scalar control, the IM drive speed is controlled with decreasing input voltage and frequency below the rated values to maintain a constant flux and torque. However, the scalar control can control the speed of the IM up to base/rated speed only and suffers from poor dynamics, especially at lower speed range [10] and when reference speed is more than slip speed range control. Vector control is generally preferred to overcome problems associated with the V/f control. ...
... Comparison of conventional and proposed SPV-fed IMD.10 International Transactions on Electrical Energy Systems based IM is less than the conventional SPV-fed SSVSI-based IM drive. ...
This article elaborates on a reduced switch count-based inverter for a single-stage solar photovoltaic (SPV) fed induction motor (IM) with sensorless speed control for water pumping applications. The traditional SPV-fed IM for water pumping applications requires a six-switch voltage source inverter (SSVSI) for transforming the DC power from the SPV system into AC power. However, the same performance is achieved using a four-switch voltage source inverter (FSVSI). Here, the entire system requires less number of switches and hence reduces switching losses and cost as compared to the traditional solar water pumping system. Moreover, the sensorless speed control is implemented using a speed estimator to reduce the overall cost further and enhance reliability. The reference voltage ( V d c r ) is achieved using an adapted incremental conductance (AINC), and the control of IM is performed using direct vector control (DVC). The control signals for the proposed system are generated using DSPACE DS-1104 for real-time implementation. The proposed SPV-fed FSVSI-based 1-HP IM operation is performed at different irradiation levels in the MATLAB-Simulink environment and validated experimentally.
... Other proposals develop a slip speed estimator based on an electromagnetic torque estimation in [9], on a gap power estimation in [10], and on a stator flux observer in [11]. Based on the ratio between the rated slip and rated stator current, references [6,12] calculate the slip. ...
... The following section applies Theorem 2 to the IM and describes the proposal details. Figure 3 shows the proposed CL HST-SCS block diagram for IM. It has a similar control scheme to Figure 2 but adjusts the voltage curve V * s0 after applying the proposed cascade N-APBC (10,11) to the IM model, once considering as unknown its nonlinear parameters α, β, γ, and δ, and its known functions a(y), b(y), c(y), and d(y). Hence, the proposal also uses (1) to calculate the slip. ...
... All parameters are assumed to be unknown and constant, which may have a slow variation. Thus, the authors substitute (10) and (11) The obtained error model (A2) has the following associated Lyapunov function: ...
This article proposes a closed-loop (CL) high-starting torque (HST) scalar control scheme (SCS) for induction motors (IM). It endows the recently proposed HST-SCS with high-output torque capability beyond starting after using an outer speed control loop feeding an inner current control loop with adaptive controllers. Presenting a cascade normalized adaptive passivity-based controller (N-APBC) for nonlinear systems encompassing the IM allows obtaining this result. It extends the normalized adaptive controller for the cascade case. As a result, it keeps the HST-SCS simple control scheme without needing variable observers or parameter estimators and employing tuning information only from the motor nameplate and datasheet. Test bench experiments with a 10 HP motor validate the proposal’s effectiveness. Comparative experimental results show that the CL HST-SCS has a required stator phase voltage lower than HST-SCS. The CL HST-SCS applies the adaptive starting voltage curve for a more extended time than HST-SCS, from the start to 1.9s versus 1.2s, respectively. Hence, CL HST-SCS assures HST not only for starting but almost up to 600 rpm, resulting in a smoother transient behavior than HST-SCS under this speed.
... They regulate the mean rotational speed to establish the optimal speed by focusing on the generator torque demand. In [54], simulations for speed control topologies that are related to the Wells turbine are compared, i.e.: (i) uncontrolled, (ii) stator-based velocity/frequency control [55], and (iii) rotor-based velocity/frequency control. As uncontrolled variations in power can harm the grid, it is suggested that the optimal topology should be implemented for the Wells turbine stator. ...
Globally abundant wave energy for power generation attracts ever increasing attention. Because of non-linear dynamics and potential uncertainties in ocean energy conversion systems, generation productivity needs to be increased by applying robust control algorithms. This paper focuses on control strategies for a small ocean energy conversion system based on a direct driven permanent magnet synchronous generator (PMSG). It evaluates the performance of two kinds of control strategies, i.e., traditional field-oriented control (FOC) and robust adaptive control. The proposed adaptive control successfully achieves maximum velocity and stable power production, with reduced speed tracking error and system response time. The adaptive control also guarantees global system stability and its superiority over FOC by using a non-linear back-stepping control technique offering a better optimization solution. The robustness of the ocean energy conversion system is further enhanced by investigating the Lyapunov method and the use of a DC-DC boost converter. To overcome system complexity, turbine-generator based power take-off (PTO) is considered. A Matlab/Simulink study verifies the advantages of a non-linear control strategy for an Oscillating Water Column (OWC) based power generation system.
... The speed control V/F closed-loop type is distinguished by its good accuracy and simplicity of tracking the reference speed [47][48][49]. The proposed PID control strategy is used to emulate a closed-loop controller to maintain the modified six phases IM following the reference speed. ...
... The speed control V/F closed-loop type is distinguished by its good accura simplicity of tracking the reference speed [47][48][49]. The proposed PID control str used to emulate a closed-loop controller to maintain the modified six phases IM ing the reference speed. ...
This paper is interested in implementing and controlling a modified six-phase induction
motor (MSPIM) when fed from a three-phase supply either via an inverter or with a direct grid
connection loaded by a centrifugal pump. The main aims of using the MSPIM are to enhance
motor reliability and reduce torque pulsation. A three-to-six phase transformer has been designed,
implemented, and employed to enable the SPIM to be driven from a three-phase supply. It is
preferable to use the three-to-six phase transformers integrated with three-phase inverter on using
the six-phase inverter to generate lower values of harmonics and lower steady-state error of speed
and reduce the starting current and because also it isolates the primary circuit from the secondary,
and the cost will be lower compared to the design of a special six-phase inverter. Dynamic models
of SPIM, three-to-six phase transformer, and three-phase variable speed drive are derived. Then, a
scalar (V/F) closed-loop control of SPIM is employed, and the results are discussed. Fine-tuning
of PID controllers is used to keep the motor speed tracking the reference value. A low pass filter is
connected to reduce the ripple of voltage and current waveforms. An experimental setup has been
built and implemented to check the possibility of controlling SPIM by a variable speed drive system
fed from a three-to-six phase transformer. It is found that the proposed method can be effectively
used to drive the SPIM from a three-phase supply.
