The operation of permanent magnet DC motors powered by a commonsource of solar cells

In a photovoltaic water-pumping system, the solar cell array is usually designed to power a single motor-load pump. Several water-pumping systems of the same or different types that are in close proximity to each other can be powered by separate solar cell arrays (sources) for each one, or, alternatively, by a common solar cell source for all the water pumping systems. The authors introduce a procedure for comparing the performances of these two setups. One system includes a permanent magnet DC motor and a volumetric pump, and the other a permanent magnet DC motor and a centrifugal pump. The comparison was also done for the same systems when a maximum-power point tracker (MPPT) was included for both the separate and the common solar cell source. It is shown, for example, that in systems not including MPPTs the total performance of the two motor-pumps in the common source system is improved as compared to the performance of the two motor-pumps when they are powered separately by individual sources     

An improved efficiency of fuzzy sliding mode control of permanent magnet synchronous motor for wind turbine generator pumping system

This paper presents an analysis by which the dynamic performances of a permanent magnet synchronous motor (PMSM) motor is controlled through a hysteresis current loop and an outer speed loop with different controllers. The dynamics of the wind turbine pumping drive system with (PI) and a fuzzy sliding mode (FSM) speed controllers are presented. In order to optimize the overall system efficiency, a maximum power point tracker is also used. Simulation is carried out by formatting the mathematical model for wind turbine generator, motor and pump load. The results for such complicated and nonlinear system, with fuzzy sliding mode speed controller show improvement in transient response of the PMSM drive over conventional PI. The effectiveness of the FSM controller is also demonstrated.     

Analysis and development of a low-cost permanent magnet brushless DC motor drive for PV-array fed water pumping system

This paper deals with the analysis and development of a permanent magnet brushless DC (PMBLDC) motor drive coupled to a pump load powered by solar photovoltaic (PV) array for water pumping system. A simple low-cost prototype controller has been designed and developed without current and position sensors which reduces drastically the overall cost of the drive system. This controller is used to test the dynamic behavior of the PMBLDC motor drive system. The mathematical model of the system is developed with a view to carry out a comparison between experimental and simulated response of the drive system. A simple filter circuit incorporated in between PV-array and an inverter to reduce ripples and to improve the performance of the PV-array. The necessary computer algorithm is developed to analyze the performance under different conditions of varying solar insolation for a pump load.     

High efficiency, long-life actuator for PV water pumping applications

A typical diagram-configuration photovoltaic (PV) water pumping system consists of a d.c. permanent magnet motor driving a diaphragm pump via a cam. The typical efficiency is low and the lifespan short. The use of a linear d.c. motor or actuator as the drive is suggested. A higher efficiency and life expectancy could be achieved. The aims of this project were to measure the pump, evaluate possible electromagnetic configurations with a finite-element analysis (FEA) package and to evaluate different electromechanical options. The results obtained for these criteria will be discussed concluding with a choice of the best topology.     

Optimum matching parameters of an MPPT unit used for a PVG‐powered water pumping system for maximum power transfer

Photovoltaic generator (PVG)‐powered water pumping has the potential to bring potable water to millions of people in developing countries. However, due to the high initial cost of PVG units, sophisticated load matching is required between the water pumping system and PVG, in order to be able to extract maximum available power from an available PVG unit at all solar radiation levels. This requires an intermediate circuitry between the PVG unit and the motor driving the water pump, which is usually termed as maximum power point trackers (MPPT). This present paper therefore investigates the optimum matching parameters of a power conditioning circuit, which is composed of a double step‐up dc–dc converter (DSUC). This MPTT circuit is used for interfacing a permanent magnet (PM) motor‐driven water pumping system to a PVG for extracting maximum available power from PVG, hence maximizing the energy utilization efficiency and price–performance ratio of the whole system. It is shown that two key parameters of the DSUC, which are the duty cycle and chopping frequency, are dominating the performance of the whole system, and they are interrelated and load dependent. Therefore, optimum values of these parameters need to be determined. An example system is provided in which a complete modelling is presented in time domain and through numerical experiments it is demonstrated how the optimum values of these two key matching parameters can be determined for a given system. The MPPT circuit used in this investigation is suitable for optimum matching of all types of loads to PVG units, provided that an optimum frequency–duty cycle pair is determined for the choppers in DSUC for every 5% bands of solar radiation between 20 and 100%. Copyright © 2005 John Wiley & Sons, Ltd.     

基于空间矢量PWM法的光伏水泵变频控制系统

介绍一种基于空间矢量PWM控制的光伏水泵变频控制系统。该空间矢量PWM算法具有对光伏阵列母线电压的动态补偿功能，保证在光伏阵列工作电压大范围变化条件下，变频驱动电机满足恒磁通调速控制。同时结合光伏水泵系统的工作特点，提出了一种简单实用的光伏阵列最大功率点跟踪控制方式，稳定可靠地实现了系统的最大功率点跟踪控制。     

Starting and Steady-State Characteristics of DC Motors Powered by Solar Cell Generators

The performance of dc motors (series, separately-excited, and shunt motors) powered by a solar cell generator and loaded by two different types of loads, one a constant load and one a ventilator load, were analyzed with respect to the transient (starting) and steady state operation. Direct current motors are employed in photovoltaic water pumping systems; therefore, the understanding of the system operation and the matching of the system components (solar cells, dc motor type, and load type) are important factors of the system design. Since the solar cell generator in a nonlinear and time-dependent power supply with an output that varies with the insolation (hourly and daily), the performance characteristics of the dc motor are different when supplied by a solar cell generator than when supplied by a conventional constant voltage source. The transient solution was obtained by using an available computer program - SUPER SCEPTRE. The separately - excited (or permanent magnet) motor with a ventilator load was found to be the most suitable for the solar cell generator. The series motor is quite acceptable, but the shunt motor gives poor performance. In all cases the ventilator load is more compatible with the solar cell generator than with the constant load.     

CVT光伏泵水系统瞬态工作点特性分析

采用定电压跟踪器（CVT）的光伏水泵系统在不同地区已成功地投入实际应用。实地运行数据表明，CVT不能适应太阳电池阵列伏安特性的变化，使系统瞬态工作点偏离阵列输出最大功率点，导致系统功率损失。该文报道了2.5kWp，光伏水泵系统的基本构成和典型实地运行数据，并对系统瞬态工作点特性进行了分析讨论。     

Determination of magnetic field constant of DC permanent magnet motor powered by photovoltaic for maximum mechanical energy output

The DC permanent magnet motor coupled with centrifugal pump has the better matching when directly powered by photovoltaic (PV) array. The important parameter of DC permanent magnet (DC PM) motor is magnetic field constant. The method for the determination of optimum magnetic field constant of DC PM motor, when powered by PV, has been obtained, and its analysis has been carried out for different magnetic field constants. It has been found that the maximum output is available at the output-energy-weighted average value of magnetic field constant. The parameter, magnetic field constant, should be properly selected during the design of DC PM motor in order to extract the maximum power from PV array.     

Maximum power point traking controller for PV systems using neural networks

This paper presents a development and implementation of a PC-based maximum power point tracker (MPPT) for PV system using neural networks (NN). The system consists of a PV module via a MPPT supplying a dc motor that drives an air fan. The control algorithm is developed to use the artificial NN for detecting the optimal operating point under different operating conditions, then the control action gives the driving signals to the MPPT. A PC is used for data acquisition, running the control algorithm, data storage, as well as data display and analysis. The system has been implemented and tested under various operating conditions.The experimental results showed that the PV system with MPPT always tracks the peak power point of the PV module under various operating conditions. The MPPT transmits about 97% of the actual maximum power generated by the PV module. The MPPT not only increases the power from the PV module to the load, but also maintains longer operating periods for the PV system. The air velocity and the air mass flow rate of the mechanical load are increased considerably, due to the increase of the PV system power. It is also found that, the increase in the output energy due to using the MPPT is about 45.2% for a clear sunny day.     

Dynamic simulation of a solar pumping system

Dynamic simulation packages are powerful tools for the investigation of highly non-linear systems. In this paper the simulation program PSI is used to investigate the characteristics of a solar pumping system consisting of PV array, dc motor and pump. Analysis and results for the method are included the paper.     

Performance analysis of a directly coupled photovoltaic water-pumping system

The application of a stand-alone directly coupled photovoltaic (PV) electromechanical system for water pumping has increased in remote areas of developing countries. In this work, the performance of a PV-powered dc permanent-magnet (PM) motor coupled with a centrifugal pump has been analyzed at different solar intensities and corresponding cell temperature. The results obtained by experiments are compared with the calculated values, and it is observed that this system has a good match between the PV array and the electromechanical system characteristics. Through manual tracking (i.e., changing the orientation of PV array, three times a day to face the sun) the output obtained is 20% more compared to the fixed tilted PV array. It has been observed that the torque-speed curve at low solar intensities for a PV electromechanical system should be steeper than at higher solar intensities, and the load torque-speed curve should be as steep as possible in the operating region with low starting torque. The performance analysis will be helpful to select the suitable PV electromechanical system for water-pumping applications.     

A simple photo-voltaic tracking system

This paper describes a simple photo-voltaic (PV) tracking system which has been designed and manufactured using a pyramidal stand as a base. A rotating unit consisting of two pairs of modules fixed at an angle of 170° between them was installed at the upper edge of the stand. The four modules and a DC motor were connected to a bridge circuit making the system sensitive to solar tracking. The PV tracker has a DC–DC (24/2 V) converter, DC–AC (24/220 V) inverter and a battery. The modules are able to provide a maximum power of 100 W, which feeds the converter, inverter and DC motor. Wind resistance of the tracker is quite low. The total area of the four modules is 1.26 m². The inclination angle between the modules and the horizontal plane is adjustable (34°±11°) and the tracking angle is 120°. The system can track solar motion with an error of ±10°. The designed PV tracking system, with modules fixed at an angle of 170° to feed the load as well as the DC motor, exhibited it to be an efficient energy-conversion system. The fabricated system offers low wind resistance. The cost analysis data revealed that the proposed design was very economical and cost effective.     

Steady-state performance of DC motors supplied from photovoltaicgenerators with step-up converter

A simple step-up converter circuit consisting of a single power transistor and an inductor is used as an interface between a PV (photovoltaic) generator and a shunt DC motor driving a centrifugal water pump. The step-up converter allows maximum power output from the PV generator to the motor at all insolation levels. Steady-state performance of the motor is vastly improved as its input voltage and current are stabilized by the regenerative action of the converter. The PV generator operates at maximum power regardless of insolation variations. The converter duty ratio can be set at a fixed optimal value which is valid for all insolation levels. This remarkable property makes this device economically attractive since it is easy to build and does not require any insolation-dependent control as compared to other peak-power tracking devices     

A novel on-line MPP search algorithm for PV arrays

A novel maximum power point (MPP) search algorithm for photovoltaic (PV) array power systems is introduced. The proposed algorithm determines the maximum power point of a PV array for any temperature and solar irradiation level using an online procedure. The method needs only the online values of the PV array output voltage and current, which can be obtained easily by using just current and voltage transducers. The algorithm requires neither the measurement of temperature and solar irradiation level nor a PV array model that is mostly used in look-up table based algorithms. Satisfactory results were obtained with the proposed algorithm in a laboratory prototype implementation scheme consisting of a PV array computer emulation model, a chopper controlled permanent magnet DC motor, and a DT2827 data acquisition board with the ATLAB software drivers for interfacing     

A fuzzy global efficiency optimization of a photovoltaic water pumping system

This paper presents an on-line fuzzy optimization of the global efficiency of a photovoltaic water pumping system driven by a separately excited DC motor (DCM), a permanent magnet synchronous motor (PMSM), or an induction motor (IM), coupled to a centrifugal pump.The fuzzy optimization procedure stated above, which aims to the maximization of the global efficiency, will lead consequently to maximize the drive speed and the water discharge rate of the coupled centrifugal pump. The proposed solution is based on a judicious fuzzy adjustment of a chopper ratio which adapts on-line the load impedance to the photovoltaic generator (PVG). Simulation results show the effectiveness of the drive system for both transient and steady state operations. Hence it is suitable to use this fuzzy logic procedure as a standard optimization algorithm for such photovoltaic water pumping drives.     

A control scheme with performance prediction for a PV fed water pumping system

This paper focuses on modeling and performance predetermination of a photovoltaic (PV) system with a boost converter fed permanent magnet direct current (PMDC) motor-centrifugal pump load, taking the converter losses into account. Sizing is done based on the maximum power generated by the PV array at the average irradiation. Hence optimum sizing of the PV array for the given irradiation at the geographical location of interest is obtained using the predetermined values. The analysis presented here involves systems employing maximum power point tracking (MPPT) as they are more efficient than directly coupled systems. However, the voltage and power of the motor might rise above rated values for irradiations greater than the average when employing MPPT, hence a control scheme has been proposed to protect the PMDC motor from being damaged during these conditions. This control scheme appropriately chooses the optimum operating point of the system, ensuring long-term sustained operation. The numerical simulation of the system is performed in Matlab/Simulink and is validated with experimental results obtained from a 180 V, 0.5 hp PMDC motor coupled to a centrifugal pump. The operation of the system with the proposed control scheme is verified by varying the irradiation levels and the relevant results are presented.     

Maximum power point tracker of wind energy conversion system

In this paper, a simple control strategy for an optimal extraction of output power from grid connected variable speed wind energy conversion system (WECS) is presented. The system consists of a variable speed wind turbine coupled to a permanent magnet synchronous generator (PMSG) through a gear box, a diode bridge rectifier, a dc-to-dc boost converter and a current controlled voltage source inverter. The maximum power point tracker (MPPT) extracts maximum power from the wind turbine from cut-in to rated wind velocity by sensing only dc link power. The MPPT step and search algorithm in addition to the DC–DC and DC–AC converters PWM controllers are simulated using MATLAB-SIMULINK software. The obtained simulation results show that the objectives of extracting maximum power from the wind and delivering it correctly to the grid are reached.     

Sizing and modelling of photovoltaic water pumping system

With the decline in price of the photovoltaics (PVs) their use as a power source for water pumping is the most attractive solution instead of using diesel generators or electric motors driven by a grid system. In this paper, a method to design a PV pumping system is presented and discussed, which is then used to calculate the required size of the PV for an existing farm. Furthermore, the amount of carbon dioxide emissions saved by the use of PV water pumping system instead of using diesel-fuelled generators or electrical motor connected to the grid network is calculated. In addition, an experimental set-up is developed for the PV water pumping system using both DC and AC motors with batteries. The experimental tests are used to validate the developed MATLAB model. This research work demonstrates that using the PV water pumping system is not only improving the living conditions in rural areas but it is also protecting the environment and can be a cost-effective application in remote locations.     

基于永磁同步电机逆系统解耦模糊滑模控制

基于逆系统理论和模糊滑模控制方法对永磁同步电动机调速系统进行了解耦控制研究,提出了一种新型的模糊推理滑模控制策略。根据永磁同步电动机调速系统的动态数学模型,证明了其逆系统的存在性,给出了永磁同步电动机逆系统解耦的模糊滑模控制器设计方法,系统仿真结果表明,该控制策略在不加剧滑动模态抖动的前提下,有效增强了系统的抗负载扰动能力,改善了永磁同步电动机系统的控制性能。