The electromechanical water supply system of a multi-storey building based on a switched reluctance motor is considered. A simulation model of the hydraulic network and criteria for evaluating the ...quasi-steady modes effectiveness of pumping equipment are given. A study of a centrifugal pump operational and energy characteristics has been carried out when adjusting its rotational speed to determine the frequencies at which the compliance of the pump pressure and flow with the hydraulic network requirements is ensured. Simulation models of control systems have been developed that provide the switched reluctance motor speeds at levels corresponding to specified flow rates of the hydraulic system pumping equipment, by means the phase voltage pulse-width regulation or the phase current limitation level adjustment. Comprehensive studies and comparative analysis of the switched reluctance centrifugal pump drive control principles were carried out according to the criteria for evaluating energy efficiency when regulating the rotational speed and changing the switching angles. As a result of this study, it was found that both pumping unit drive control principles provide its necessary productivity and are close in efficiency - a slightly higher efficiency can be achieved using the phase voltage pulse-width regulation of the switched reluctance motor with a changing the switching angles. References 10, figures 8.
Kalina cycle is a promising heat-to-power technology in low-grade heat recovery applications. Most previous research concerning the Kalina cycle systems focused on the analysis and optimization based ...on static models with less consideration given to dynamic performance. It is important to explore the dynamic behaviour of the Kalina cycle system for operation safety due to the fluctuation of low-grade heat sources and the external load. In this paper, a dynamic model of a Kalina cycle system driven by a low-grade heat source is established to analyse the dynamic behaviour of the system. The valve-pump coordination control strategy and the pump control strategy are proposed and compared with the valve control strategy, with the turbine rotational speed as the controlled variable. Result reveals that the valve-pump coordination control strategy reduces the transient time and overshoot by 56.3% and 67.9%, respectively. The dynamic behaviours of the Kalina cycle system under valve-pump coordination control strategy subjecting to disturbance are then studied, including heat source temperature disturbance, heat source mass flow rate disturbance, and system load disturbance. The results show that for these disturbances, the transient times of the turbine rotational speed are 11.8 s, 12.1 s and 11.7 s while the overshoots of that are 1.30%, 1.67% and 1.33%, respectively.
•A dynamic model of the Kalina cycle system with a control system is present.•The valve-pump coordination control strategy is proposed to improve performance.•The coordination control reduces transient time by 56.3% and overshoot by 67.9%.•Disturbance of heat source temperature, flow rate and system load are considered.•Dynamic behaviours of the Kalina system subjecting to disturbance are analysed.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Wind energy conversion systems (WECSs) can extract maximum power by controlling the wind turbine rotational speed. This study presents a novel sensorless maximum power extraction control for ...small-scale WECS using a permanent magnet synchronous generator (PMSG), to improve the maximum power extraction. The proposed method uses the output voltage and current of a rectifier to determine the duty cycle of the boost converter, without requiring the wind speed information and turbine characteristics. The step size of the duty cycle is changed adaptively, based on the difference between the rectifier output power and the previous duty cycle to obtain fast convergence, until the maximum power point is attained. The performance of the proposed sensorless maximum power extraction control is evaluated both by simulation, using PowerSIM and laboratory experiments, for variable wind speed conditions. The proposed maximum power extraction controller has a simple structure, low cost, and a good response to wind speed variations. The proposed method can extract a higher maximum power and has a higher efficiency of 93.87%, than the conventional perturb and observe method.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
A repetitive control system (RCS) provides good control performance for periodic signals, but it may not satisfactorily reject aperiodic disturbances. Our solution is an equivalent-input-disturbance ...(EID)-based RCS in which aperiodic disturbances are estimated by an EID estimator and rejected by incorporation of the estimate into the repetitive control law. A stability criterion and a design algorithm have been developed, and the validity of the method has been demonstrated through simulations and experiments on a rotational speed control system. A comparison of the disturbance rejection performance of this method, proportional-integral-differential control, conventional repetitive control, and H ∞ repetitive control demonstrates the superiority of this method.
•Control scheme for hydrokinetic systems based on variation of resistive load.•Ideal resistive load to power extraction maximization.•Assessment of control system under variable water stream ...speeds.•Influence of ideal tip speed ratio on the energy production.•Impact of characteristic rotor curve shape on HECS dynamic.
A stand-alone hydrokinetic energy conversion system (HECS), comprising a permanent magnet synchronous generator (PMSG), coupled to a horizontal axis hydrokinetic turbine through a mechanical transmission. The rotor performance is given by a characteristic curve of power as function of the rotation, given in non-dimensional quantities. The transmission is assumed to be of single stage with known mechanical efficiency. Park’s transform is applied to obtain the PMSG model, which is connected to resistive and inductive loads. A new method for the rotor angular speed control underwater speed variations, consisting on changing a resistive load connected to the generator, is presented. We present an analytic expression for the value of the resistive load, which keeps the HECS in the optimal operational condition. In addition, the numerical model in used to perform an investigation on the influence of the rotor power curves on the generation system stability and conversion efficiency. The generation system is submitted to variations of terminal load and water speed in order to assess its response in several situations of practical interest. It is shown that rotors which sharp characteristic curves are most likely subjected to severe stopping in the case of stream speed variation or demand variation oscillation, when compared to rotors with more smooth power curves.
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The electromechanical systems under analysis include electric drives, working machines that perform specific tasks in the technological process, and working mechanisms that transmit mechanical power ...between the electric drive and the working machine. The vast majority of electric motors included in drive systems require rotational speed control. This task is most often performed with the use of closed-loop control structures based on speed controllers. A step or overly rapid change in the speed reference causes a temporary lock of the speed controller due to the applied limitations at its output. Particularly, unfavorable effects of such a lock can be observed in drive systems in which there is a long elastic coupling (transmission shaft) between the electric motor and the working machine. As a consequence, shaft torsion and accompanying twisting moments of considerable amplitudes appear. This article proposes an uncomplicated active torque limiter structure, which enables the uninterrupted operation of the speed controller thanks to the automatic adaptation of the rate of the speed reference change to any moment of inertia of the rotor and attached rotating masses. The results of the investigations confirm the effectiveness of the proposed structure.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Combined with the actual working condition of explosion-proof mixers used in underground coal mine, different from the traditional throttling method to control the speed of the material tank, by ...analyzing the working principle of the closed type pump, the strategy of adjusting the control pressure of the closed type pump to control the rotational speed of the material tank of the mixer is proposed, which is associated with the driving gear position of the vehicle so as to ensure that the material tank is in a low rotational speed state when the vehicle is running; only when the vehicle is in a neutral gear position, the high speed rotating mixing and unloading can be realized. Through the field tests, the results show that the rotational speed of the material tank installed with the speed control system can maintain a constant speed state, and will not change with the change of the throttle.
A robust disturbance rejection method for uncertain systems is presented in this study. It effectively rejects both matched and unmatched disturbances and guarantees robust stability of the system ...when there exist modelling uncertainties. First, the authors show the configuration of the system that is based on the idea of the equivalent input disturbance (EID). An EID estimator is designed to compensate disturbances without requiring their prior knowledge. Then, a robust stability condition and the method of the controller design are presented using a linear-matrix-inequality. Finally, the validity of the authors method and its superiority over a conventional control method and the sliding-mode control method are demonstrated through the simulations of a numerical example and experiments of a rotational-speed control system.
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Hydro-viscous clutch has already become an inevitable choice for special vehicle transmission in the present and future. As a nonlinear system with a large hysteresis loop, its speed control ...performance is affected by input rotational speed, lubricating oil temperature, lubrication pressure, and other factors. The traditional control method cannot adjust the temperature and rotational speed, which will lead to problems of narrow speed range, poor rotational speed stability, and large dynamic load impact. In order to solve the above problems, this paper studies the control method of an integrated multi-parameter hydro-viscous speed control system (HSCS) in a controlled environment. Through the mechanism analysis of the law of HSCS, the influence law of speed and temperature during the system operation is found. The temperature closed loop based on model predictive control (MPC) is introduced to control the rotational speed, and then the traditional PID control results are compensated according to the speed closed loop. Next, a novel double closed loop control method of temperature and rotational speed for HSCS is formed. Finally, the simulating verification is carried out. Compared with the traditional control method, the design method in this paper can adjust the control parameters according to the temperature of the lubricating oil and the input rotational speed and effectively expand the domain of HSCS and the speed control stability. The effective transmission ratio is extended to 0.2~0.8, and the hydro-viscous torque and speed fluctuation under the engine rotational speed fluctuation are reduced by more than 30%. The novel control method of HSCS designed in this paper can effectively improve the influence of input rotational speed and lubricating oil temperature on the speed control performance of HSCS and can be widely used in nonlinear HSCS such as hydro-viscous clutch.
The power take-off system plays a vital role in the wave energy generating unit. Here, for studying the operation characteristics and methods of the hydraulic power take-off system, its basic model ...is built relying on the operating principles of every component. Meanwhile, a proportional–integral–derivative (PID) controller is also designed to regulate the rotational speed of the motor. Then, a test platform for the hydraulic power take-off system is constructed to verify the correctness of the model. Fortunately, based on model analyses, some useful results are found. Firstly, the PID controller has a visible effect on stabilizing the rotational speed. In addition, a group of optimal control parameters are obtained. Secondly, the influences of the displaced volume on the operation characteristics of the hydraulic power take-off system are found. Meanwhile, the optimal displaced volume is also presented by weighing the efficiency and stability. Finally, the operation modes and regions of the hydraulic power take-off system are obtained, and its rationality is also proved by a simulated running of the system. More importantly, these results can provide a reference to the design and operation of the hydraulic power take-off system.
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NUK, OILJ, SAZU, UKNU, UL, UM, UPUK
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