Variable Speed Control Strategy Research Articles

Analysis, simulation and experimental strategies of 5-phase permanent magnet motor control

This paper presents a study of control strategies for 5-phase permanent magnet synchronous motors (PMSMs) supplied by a five-leg voltage source inverter. Based on the vectorial decomposition of the multi-phase machine, fictitious machines, magnetically decoupled, allow a more adequate control. In this paper, our study focuses on the vector control of a multi-phase machine using a linear proportional-integral-derivative (PID) current regulator in the cases of sinusoidal and trapezoidal back-electromotive force (EMF) waveforms. In order to determine currents' references, two strategies are adopted. First one aims to minimize copper losses under constant torque, while the second one targets to increase torque for a given copper losses. These techniques are tested under a variable speed control strategy based on a proportional-integral (PI) regulator and experimentally validated.

Dynamic performance simulation of combined gas electric and steam power plants for cruise-ferry ships

This work aims at investigating the feasibility of COmbined Gas Electric and Steam (COGES) plants onboard Liquefied Natural Gas (LNG) fueled ships, by means of a novel, flexible tool. Firstly, the nominal operating conditions of 6 commercially available gas turbines (GTs) as well as their dynamic performance are simulated. Secondly, 6 different integrated COGES-reciprocating engine power plants are assembled and compared in terms of cogeneration efficiency within an optimized repowering study for the cruise-ferry ship GNV La Suprema. The optimization accounts for variable ship speed, season and GT control strategy for an overall number of 264 operating conditions considered. Thirdly, the time-dependent performance of the best COGES plant is assessed under actual navigation conditions for La Suprema. Overall, the results show the great potential of combining COGES plants with reciprocating engines for the marine sector. In particular, in the ship speed range centered around the actual cruise speed for La Suprema (i.e. 22 knots), all the COGES plants are able to cover the propulsion and hotel power demands more efficiently than reciprocating engines, with a 1–5 % benefit on cogeneration efficiency. Overall, a 51 % maximum cogeneration efficiency is found to be provided by COGES plants based on LM2500 and TITAN250 gas turbines.

A novel adaptive variable speed control strategy for wound rotor induction motors

A novel adaptive variable speed control strategy for wound rotor induction motors

A novel adaptive variable speed control strategy for wound rotor induction motors

A new approach is proposed for the design of an adaptive variable speed controller for an induction motor. This design approach is based on a new model for induction motors in the (α/β) reference frame. The model state variables are constant in steady state and therefore enable the application of adaptive backstepping control design techniques to find controller equations and adaptation laws that ensure that the rotor speed and flux track their reference values despite significant changes in machine resistances and inductances due to temperature and magnetic saturation. The proposed controller is tested in simulation. Results show robust steady state and transient performances.

Power Train System Control of Electric Loader Based on Positive Flow System

Energy conservation and emission reduction have drawn more and more attention in the world. Loaders are widely used in various earthworks. However, traditional loaders with high energy consumption and poor emission cannot meet the needs of sustainable development. Electric loaders can achieve zero emission by replacing the engine with the electric motor, which is considered to be one of the main trends in future development. However, the existing electric loader only uses the electric motor to simulate the operation of the engine without fully considering the characteristics of the hydraulic system, resulting in the inability to optimize the energy efficiency and control performance of the system. In this paper, an electric motor with excellent speed regulation was employed. A positive flow system based on variable speed for constant displacement pump was studied. The efficiency of the power train system was analyzed. The relationships of the opening area of the main valve core, the system demand flow, and the pilot pressure were studied. A variable speed control strategy based on the pilot pressure control was put forward. In order to verify the feasibility of the proposed system and control strategy, simulation and experiments were carried out. The results showed that the proposed system has better energy saving and maneuverability than the traditional constant flow system.

High-performance MPPT control of DFIG with optimized flux reference in presence of nonlinear magnetic characteristic

In recent years, an expansive research exertion has been devoted to the control for aeorogenerators conforming of a Doubly Fed Induction Generator (DFIG) coupled to a wind turbine. Most preceding controllers based on standard models (whose magnetic induction characteristic is considered linear and iron losses have not been taken into account). Since such a magnetic characteristic is nonlinear in practice, this work develops a variable speed control strategy on the basis of a DFIG model in presence of nonlinear magnetic characteristic and iron losses. The main contribution of this paper is to present a high-performance maximum power point (MPPT) control of DFIG based on rotor flux optimization, designed to reach an optimal operational conditions. Of the foregoing, the control goal is twofold: i) minimization of the stator and rotor currents circulating by controlling the rotor flux for a maximum electromagnetic torque; ii) captured the maximum wind power to insure the attainment of MPPT. The performances of the proposed command has been studied theoretically and validated by simulation studies with Matlab/Simulink.

Off-design behavior investigation of the combined supercritical CO2 and organic Rankine cycle

To provide a higher energy conversion efficiency, an organic Rankine cycle (ORC) is coupled to a supercritical carbon dioxide cycle (sCO2) for energy cascade utilization. However, power cycles often operate during a wide range of loads and the heat sink temperature varies over time. Therefore, the off-design behavior analysis is vital to better define cycle performance and build control systems. In this paper, detailed design and off-design models of the cycle components are developed to evaluate the cycle performance at different operating conditions. The results show that the cycle thermal efficiency can reach up to 44.39% when the inlet pressures of the sCO2 and ORC turbine equal to 20.77 MPa and 754.04 kPa, respectively. The variable-speed control strategy is used to regulate the maximum pressure, the mass flow rates and the component behaviors to achieve operational goals. Based on this method, the combined sCO2-ORC cycle can be matched well with the nuclear reactor during a wide range of power loads (20–110% normalized power load) and heat sink temperatures (10–40 °C). The cycle performance decreases with plant loads, and an opposite trend is observed when the heat sink temperature changes. Compared with the stand-alone recompression sCO2 cycle, the combined sCO2-ORC cycle can gain a thermal efficiency improvement of 1.09–3.36%. But the cycle performance deteriorates significantly when the heat sink temperature is high due to the increase in the compression power consumption. From an economical point of view, the recompression sCO2 cycle can gain a decrement by 2.32% for the levelized cost of electricity by integrating an ORC, and further cost optimization of reactors and turbines can make the cycle more commercially competitive.

A Variable Speed Control Strategy for Impurity Removal Fan of Sugarcane Combine Harvester based on GA-SVR Model

A Variable Speed Control Strategy for Impurity Removal Fan of Sugarcane Combine Harvester based on GA-SVR Model

Analysis of the effects of control strategies and wave climates on the loading and performance of a laboratory scale horizontal axis tidal turbine

To understand the influence of complex hydrodynamic loads on tidal turbines, laboratory testing is necessary as a first approach. Previous laboratory work undertaken gave an indication that the use of speed control strategies may disguise the associated loading range that a turbine may be subjected to when this is operated with a variable speed control strategy. However, the preceding work was undertaken in a highly controlled environment without the influence of turbulent flows. The focus of this paper is directed towards the study of wave-induced loads on tidal turbines when these are controlled using two strategies and the impact that these parameters have on the turbine’s performance when this is operated in a recirculating flume. Laboratory tests were undertaken with a 0.9 m diameter horizontal axis tidal turbine subjected to combined wave and current conditions with both regular and irregular waves. Constant speed and constant torque control strategies have been considered, for which rotor thrust, torque and blade root bending moment have been measured. Results show that similar to previous studies, average loads and power capture values remain unchanged between control strategies and the superposition of waves to the current. However, signal fluctuations are 2 to 3 times higher for torque control than for constant speed control strategy. A phase difference between the periodic signals of the turbine thrust and the incoming waves was also identified, in this case, the phase variation was lower when using torque than speed control. This work thus demonstrates the implication of studying strategies to control a marine converter from early stages of development.

Asymptotic tracking control for wind turbines in variable speed mode

This paper presents a variable speed control strategy for wind turbines in order to capture maximum wind power. Wind turbines are modeled as a two-mass drive-train system with generator torque control. Based on the obtained wind turbine model, variable speed control schemes are developed. Nonlinear tracking controllers are designed to achieve asymptotic tracking for a prescribed rotor speed reference signal so as to yield maximum wind power capture. Due to the difficulty of torsional angle measurement, an observer-based control scheme that uses only rotor speed information is further developed for global asymptotic output tracking. The effectiveness of the proposed control methods is illustrated by simulation results.

Improved variable speed control of series‐connected DC wind turbines for offshore wind power collection to high‐voltage direct current system

DC wind farm (DCWF) with series-connected DC wind turbines (DCWTs) is proved to be a potential solution of offshore wind power collection. The coupling behaviour of series-connected DCWTs is described in detail. Possible wind energy curtailment during the period of wind turbine voltage limitation and its key impact factors are firstly quantitatively derived. A novel variable speed control strategy is proposed under voltage limiting condition of the DCWT to improve its wind energy capture. This control algorithm can be implemented in the local DCWT controller without the communication need. The specific variable speed control strategy of the DCWT is realised in a generalised averaged model. Dynamic simulation cases under different operation conditions have been conducted to evaluate the effectiveness of the proposed control strategy. It is found that the proposed control strategy might be a solution for wind energy curtailment, which will significantly improve the performance of the series-connected DCWTs between the time scale above seconds and below minutes.

Dynamical Modeling of Frequency Controlled Variable Speed Parallel Multistage Centrifugal Pumps

Abstract This paper presents a development of a model of a set of multistage centrifugal electro pumps including two 4 stage stainless steel centrifugal pumps, each coupled to a 4 kW three-phase induction motor, connected to a hydraulic application running under two control strategies including constant speed and variable speed methods. Each pump provides 16 m3/hr flow rate and 58mwater head at BEP (Best Efficiency Point). Dynamicity of the model causes variations in all operational parameters of pumping system in any variation on consuming flow rate. Each electro pump has been driven with a variable frequency drive utilizing frequency control method for adjusting the rotational speed under a PID control regarding to match of pumping system operational point with the consumption point to save the energy. 83% energy saving is achieved by model in variable speed control strategy comparing to constant speed control strategy. MATLAB/SIMULINK software using ode45 solver and variable step size simulates this model.

Optimisation of motorway operations via ramp metering and variable speed limits

This paper presents a modelling and optimisation framework for deriving ramp metering and variable speed control strategies. We formulate the optimal control problems aiming to minimise the travel delay on motorways based upon a macroscopic cell transmission model of traffic. The optimal ramp metering optimisation is formulated as a linear programming (LP) while the variable speed control problem is formulated as a mixed integer LP. The optimisation models are applied to a real scenario over a section of M25 motorway in the UK. This paper also includes various analyses on the sensitivity of the optimal control solutions with respect to different network configurations and model assumptions.

Modelling and control of a multi-phase permanent magnet synchronous generator and efficient hybrid 3L-converters for large direct-drive wind turbines

A novel full-size wind power conversion system based on a multiphase permanent magnet synchronous generator (MPPMSG) and hybrid multi-converter system using 3-level neutral-point-clamp converters (3L-NPC) for high-power direct-drive wind turbines is proposed in this study. Higher efficiency, lower harmonics is achieved by replacing the traditional 2-level converter cells with 3-level cells. Circulating current is eliminated by using hybrid connection for multiphase generator design to replace the commonly used parallel converter structure for 3-phase generator design, the issues for neutral-point voltage imbalance is also eliminated. The mathematical model of MPPMSG and variable-speed control strategy are built and verified in PSCAD/EMTDC. A 3.5 kVA MPPMSG prototype machine and a set of hybrid 3L multi-converter systems are built. The experimental results validate the model and the effectiveness of the control strategies.

Asymptotic Tracking Control of Variable-Speed Wind Turbines

AbstractThis paper presents a variable speed control strategy for wind turbines in order to capture maximum wind power in region 2. Wind turbines are modeled as two-mass drive-train system with generator torque control. Based on the obtained wind turbine models, variable speed control schemes are investigated for region 2. We designed nonlinear tracking controllers to achieve asymptotic tracking control for given rotor speed reference signals so as to yield maximum wind power capture for both state feedback control and output feedback control. The proposed schemes are shown to be able to achieve smooth and asymptotic tracking and illustrated by the given simulation results.

작동 조건 변화에 따른 풍력발전 시스템의 동적 특성 해석

A design methodology for control strategy and control structure gives a direct impact on wind turbine's performance and life cycle. A baseline control law which is a variable rotor speed and variable pitch control strategy is introduced, and a mathematic performance model of a wind turbine dynamics is derived. By using a numeric optimization algorithm, the steady state operating conditions of wind turbines are identified. Because aerodynamic interaction of winds with rotor blades is basically nonlinear, a linearization procedure is applied to analyze wind turbine dynamic variations for whole operating conditions. It turns out the wind turbine dynamics vary much depending on its operating condition.