Small-scale wind turbines provide a viable alternative energy source for small farms, busi- ness and rural areas. The goal of such small-scale turbines is to provide electricity at the lowest cost possible. It is thus imperative that turbines capture the maximum volume of energy at the lowest cost and highest possible efficiency, while having a high reliability. Assuming a suitable turbine location and good blade design, two of the biggest factors in ensuring this goal include the choice of generators as well as the control of the turbinesystem. While the permanent magnet synchronousgenerator (PMSG) is a popular choice for small-scale wind turbines, its use of permanent magnet material increases the cost of the system. One of the alternatives to the PMSG that has received renewed interest dur- ing the last few years is the reluctancesynchronousgenerator. This thesis focuses on the development and control of an assistedreluctancesynchronousgenerator (ARSG) windturbinesystem. The ARSG is an effort to help solve, at least partially, some of the dis- advantages of the standard reluctancesynchronousgenerator (RSG), e.g. the low power factor. A simple rotor design is proposed, with a cursory comparison given between dif- ferent rotor slot shapes. The mathematical model of the ARSG is derived, which serves as the basis of the development and implementation of a non-linear current controller. A maximum torque per ampere (MTPA) strategy based on the finite element (FE) analysis of the machine is developed and implemented practically. To ensure that the turbine is operated at optimal efficiency, a standard tip speed ratio (TSR) controller is designed and implemented. This controller can operate at under and above rated wind speeds. The results of the practical tests show the feasibility of the use of the DC-bus link connection as well as the performance of the control systems.
to their calculated values, except that the generated electrical power is slightly smaller than the mechanical power input into the system. This is due to the internal power losses in the system. Based on the analysis above, the control objectives for the low windspeed range were achieved and the optimal power is captured and transformed by the PMSG. (2) From 1.3-2.6s: starting from 1.3s, the windspeed increases from to , which is the rated windspeed of the system. As shown in Figures 3.10 through 3.15, with the increase of the windspeed, stator currents, electromagnetic torque, and generated electrical power gradually increase to their rated values which are shown in Table 3.1. The comparison between the actual values and the rated values of the system parameters are shown in Figure 3.17. From these figures, the simulation results correspond well to the rated values. Again, the reason that the actual electrical power generated by the PMSG is slightly lower than the mechanical power input is due to the internal power losses. Thus, conclusions can be made that the control objective was achieved under the rated condition of the system.
In this thesis, several aspects of modelling and control of Fuzzy Based interior permanent magnet synchronousgenerator based grid connected variablespeedwindturbine is presented. Both the vector and direct control strategies are addressed for IPM synchronousgenerator based variablespeedwind turbines are investigated. The impacts and issue associated with grid integration of wind farm are also studied. The proposed direct control scheme possesses several advantages compared with indirect vector control scheme, such as: 1) lesser parameter dependence; 2) torque andflux control without rotor position and PI controller which reduce the associated delay in the controllers; and 3) sensorless operation without mechanical sensor. The results show that the direct based fuzzy controller can operate under varying wind speeds. However, direct control scheme has the problem of higher torque ripple that can introduce speed ripples and dynamic vibration in the power train. The methods to minimize the torque/ speed ripples need to be addressed by fuzzy bassed control technique. The simulation and experimental results for the sensorless speed estimator are presented, and the results show that the estimator can estimate the generatorspeed quite well with a very small error.
ratio presented in Figures 9(b) and 9(c) remains close to the optimal value before 50-second , but standard devia- tion becomes large after 50-second. Both the torque con- troller and the blade pitch angle controller with the PID neural network have better control effect, and LPV com- pensation control has shown better control performances as compared to the classical PID compensation control, which can be obtained with a reasonable control effort. Secondly on the Figures 9(d) and 9(g), the responses of output power, blade pitch angle, generatorspeed, genera- tor torque with the compensation control methods to the step change in windspeed are shown. A sudden change in windspeed, the output responses can obtain the optimal values before 50-second and stably remain close to the rated values after 50-second. The results comparison of windturbine with LPV compensation and classical PID compensation reflect that the LPV compensation control has more expected control performance. Therefore, it is clear that classic approach to Multi-variable controller de- sign are assumed to be constant. This is the reason why the wind turbines cannot follow the optimal work per- formance during the changes in windspeed. The proposed method can handle better changes in windspeed resulting in faster control of wind turbines, because this method can not only improve the sensitivity of the system by the PID neural network controller when the windspeed is below the rated value, but also assure reducing the system vibra- tion caused by fast dynamic resulted from the action of the turbulent windspeed.
Abstract - This work presents modified frequency orientation control FOC of variable-speed direct-driven permanent magnet synchronousgenerator (PMSG) in wind energy conversion system (WECS). The objective is to optimize the power capture from the wind utilizing frequency orientation control FOC scheme without windspeed sensors. The model is developed with time framed meteorology forecast. the Mean windspeed forecast are substituted as starting windspeed (sensed value). The Simulation results are presented for various changes in windspeed at 480m above sea level using matlab powsys. The ability of the system to operate at the optimum coefficient of performance without the need for a speed sensor is subsequently analyzed, Mmaku in Awgu local government council of Enugu Nigeria is use as our test case.
Electrical energy has also a key role in robotics application [14, 15]. To meet the increasingly electrical demand, different approaches has been proposed, from developing several generation units and integrating renewables into the grid to active participations of the costumer sides in the power flow balancing [16, 17]. Recently, Permanent Magnet AssistedSynchronousReluctance Motor (PMa-SynRM) has attracted attentions in transportation industry. This is due to good characteristics of interior permanent magnet synchronous motoes and that such motors lack any shortcomings. Good characteristic of IPM-SMs is their high efficiency performance, output power, and gain due to magnetic and reluctancetorque . Main disadvantages of IPM-SMs are high current of q axis at high speed operations in flux-weakening region  and uncontrolled generator operation as a result of which the inverter exits the circuit . The above problems are due to uncontrolled linkage flux generated by magnets. These fluxes can be resolved by employing PMa-SynRM. In PMa- SynRM structure, number and value of magnets and linkage flux of magnets are very low compared to IPM and dominant torque is the reluctancetorque . Compared to conventional reluctancesynchronous motors, PMa-SynRM has better torque and power factor. Radiation on photovoltaic system is researched in [21, 22] and optimum tilt angle of photovoltaic systems is investigated. It is showed that experimental and theoretical tilt angles are different in that dust effects photovoltaic systems. Also, it is proved that produced energy by experimentally yearly optimum tilt angle is 3% more than theoretical tilt angle.
WPGSs with large capacity are required to support the operation of the power networks via providing similar control functionalities as conventional synchronous generators (SG), such as voltage control, frequency control and stability improve- ment [23, 24]. Control of the DFIG to make its behavior like an SG was proposed in [24–26], in which control blocks normally employed in the SG like automatic voltage regulator (AVR) and power system stabilizer (PSS) are applied to the DFIG, and a new control scheme called as flux magnitude-angle controller (FMAC) is ob- tained. In the FMAC, magnitude and angle to the rotor flux are employed as control variables for terminal voltage and active power, respectively. Compared with the SG, the DFIG has better controllability to achieve independent control of the ter- minal voltage and active power (or the provision of damping) because it has two independent control inputs, while the SG involves a compromise between the con- flicting requirements of voltage control and the provision of damping as both AVR and PSS use the magnitude of the field voltage as the control variables (Note that the angle of voltage field cannot change as it is aligned with the rotor). However, all additional controllers are designed based on classical linear control theory, and their parameters are optimized based on one operation point. Based on the idea of the FMAC and solving the parameter tuning, a damping controller is designed based on a simple PI controller and tuned using bacterial foraging technique to enhance the damping of the oscillatory modes .
This paper deals with a variable-speedsystem consisting of synchronousgenerator, diode rectifier and thyristor inverter. The advantages of the synchronousgenerator and a diode rectifier are the high efficiency of the rectifier and the low price. There are two disadvantages that can be important in windturbinegenerator systems. Motor start of the turbine is not possible without auxiliary equipment and the torquecontrol is normally not faster. The aim of this report is to describe an efficient variable- speedsystem and to model the generator and converter losses .
The aim of this paper is to analyze the potential of switched reluctancegenerator (SRG) in wind energy application. The machine comprises of switched reluctancegenerator, power converter and controller. In this paper the main ele- ments that form the generatorsystem is discussed. It also highlights the common type of converter and structure used for SRG in wind energy application and types of control strategy available. Using power converter for switching the generator can operate over a wide speed range. Its applications in high speed area such as starter/generator for air- craft and gas turbine has been established, however the low/medium speed operation is still at an early stage of re- search. In order to subject the machine to various parameters, offline modeling is being investigated to produce the best optimum design.
Windturbinesystem is a high order, strongly coupled, non- linear, multivariable system. Pitch-adjusting variable-speedwind turbines are the dominating type of installed wind turbines. As shown in Fig-1, variablespeedwind turbines offer improved energy capture as the range of speed of the wind under which the maximum power is generated is increased. In modern power control techniques, power is kept at a rated value by controlling pitch angle β. This angle is defined as the angle between the pitch rope and its rotating shaft. Rotor speed must be controlled either by regulating the generatortorque or manipulating the blade pitch angles.
DOI: 10.4236/jpee.2018.61005 63 Journal of Power and Energy Engineering The other parameters values are initially set to zero. Figure 9 and Figure 10 show that the mechanical power had been maximized as result of the approach- ing of power coefficient from its maximum value ( C p = 0.479 ) . ESC in the out- er loop is based on the generatorspeed regulation via the electrical power feed- back. The ESC searches for the optimal generator’s speed to maximize power without accurate knowledge of power map. In the inner loop, PI controller re- gulates the generatorspeed in closed loop to attain the optimal speed that is suggested by ESC. As in Figure 6, the speed of the generator was approximately around the optimal speed 157.5 rad/s, meanwhile the speed of turbine rotor in Figure 11 is around 2.1 rad/s since the gearbox ratio equals to 75. Figure 12 shows that the electrical power attains its maximum power capture in some pe- riods of time (2 MW in 6 - 8 s, 14 - 19 s), meanwhile the electromagnetic torque in Figure 13 approaches to its rated value (14,700 Nm in same periods) accord- ing to the decreasing or increasing in windspeed measurements. Finally, Figure 14 shows the three phase stator currents of SCIG.
Abstract: The interest in wind energy system is growing worldwide to reduce dependency on fossil fuel and to minimize the adverse impact of climate change. Currently, doubly fed induction generator (DFIG) based variablespeedwindturbinetechnology with gearbox is dominating the world market share. However, the problems associated with induction generator based wind turbines are reactive power consumption, mechanical stress and poor power quality. Moreover, the gearbox requires regular maintenance as it suffers from faults and malfunctions. Therefore, it is important to adopt technologies that can enhance efficiency, reliability and reduce system cost of wind based power generation system. The performance of a variablespeedwindturbine can be enhanced significantly by using a low speed permanent magnet synchronousgenerator (PMSG) without a gearbox. The main features of PMSG based wind turbines are; gearless operation, higher efficiency, enhanced reliability, smaller size, reduced cost and low losses.
This power production process faces many challenges like the structure of turbine for better efficiency and cost, control of turbine of generator for maximum power, mode of operation and some power quality problems etc. The turbines operation is possible in both the fixed speed and variablespeed mode but mostly manufactures are opting for variablespeed turbines by opting either turbine side control mechanism or machine side control operation. Wind power system can be used for either stand-alone or grid- connected operation according to requirement. Different types of generator topologies can be used for the power generation from turbine. The power electronic converters are very much effective or efficient enough for connecting these sources of energy and utility grid. They behave as an interface between these two.
In this paper, an independent wind energy conversion system was studied with the control strategies used to pro- vide power specifically to the areas far from the grid. In this research, three strategies are designed and used in order to stabilize the output. This system contains a directed rectifier which is responsible for maximum power point tracking. Additionally, a common DC bus and a fully controlled inverter were designed. An LC filter was also used in the system in order to eliminate switching harmonics to a considerable extent and provide a reliable noiseless source for load supply. Since the power demand and the produced power of the turbine are variable and indistinguishable in each moment, a depletion load is also placed in the system. In this study, it was observed that the designed strategies prove the output stability in different sections and under different conditions with resona- tors and non-linear PI and PID controllers. The designed strategies were also supported by the simulation results. Keywords: windturbine, permanent-magnet synchronousgenerator (PMSG), output stability of the turbine, resis- tive depletion load, voltage damping, Reduction of switching harmonics.
method to control the torque on top of blades of the windturbine at high wind speeds. As the incursion of the wind energy into the electrical power grid is widely improved, the persuade of the windturbine systems on the frequency and voltage stability becomes extra momentous. Existing pitch angle control includes Proportional Integral(PI) controller, Proportional-Integral-Derivative (PID) controller, PI with gain scheduling ,fuzzy logic controller and sliding mode control. By combining existing methods it will give better results in controlling output power and rotor speeds. this controller is intended to control Pitch angle, it doesn’t require much knowledge of system representation. Inputs to Fuzzy controller are error in PMSG output power and speed of rotor thus Fuzzy controller gives reference angle to compensate non-linear nature of the windturbine. This technique is carried out on a 5MW PMSG windturbinesystem at wind speeds of 13m/s in MATLAB.
In recent years, numerous topologies of power conditioning systems, varying in cost and complexity, have been developed for integrating PMSG windturbine systems into the electric grid. In modern PMSG windturbine generators system designs, the power conditioning systems is typically built using a full-scale power converter made up of a two-stage power conversion hardware topology that meets all the constraints of high quality electric power, flexibility and reliability imposed for applications of modern distributed energy resources , . This power conditioning systems design is composed of a back-to-back converter that enables to control simultaneously and independently the active and reactive power flows exchanged with the electric grid, as described in Fig. 1.
Variablespeedcontrol of windturbinegenerator systems have been developed to get maximum output power at every windspeed variation, also called Maximum Power Points Tracking (MPPT). Generally, MPPT controlsystem consists of MPPT algorithm to track the controller reference and generatorspeed controller. In this paper, MPPT controlsystem is proposed for low speedwindturbinegenerator systems (WTGs) with MPPT algorithms based on optimum tip speed ratio (TSR) and generatorspeed controller based on field oriented control using type-2 fuzzy system (T2FS). The WTGs are designed using horizontal axis wind turbines to drive permanent magnet synchronous generators (PMSG). The simulation show that the MPPT system based optimum TSR has been able to control the generator output power around the maximum point at all wind speeds.
A schematic diagram of an SRG based windturbinesystem is shown in Figure 2. The controlsystem is based on the control of two separate power converters. The SRG converter regulates the windturbine to allow maximum power extraction for varying wind profiles. The second converter or grid side inverter regulates the DC link voltage to allow energy from the SRG to be delivered to the system.
Recent trend indicates that wind energy will play a major role to meet the future energy target worldwide to reduce reliance on fossil fuel and to minimize the adverse impact of climate change. Wind energy is the fastest growing generation technology among the renewable energy sources. Over the last decade, the global wind energy capacity has increased rapidly and wind is an important competitor to the traditional sources of energy. In 2013, more than 35 GW of wind power capacity was added to the global wind generation capacity which became 318 GW as shown in Fig.1.1 . Since 2008, annual growth rates of cumulative wind power capacity have averaged 21.4%, and global capacity has increased eightfold over the past decade , . Recently, capital costs of wind generation technologies have declined primarily due to the competition and advanced technology development including taller towers, longer blades, and smaller generators in low windspeed areas—have increased capacity factors . The technological development contributed to reduce the costs of wind turbines and made it competitive relative to fossil fuel based generation. Onshore wind-generated power is now more cost competitive on a per kWh basis with new coal/gas fired power plants, in several markets (including Australia, Brazil, Chile, Mexico, New Zealand, South Africa, Turkey, much of the EU, and some locations in India and the United States) , . As a result of this trend, high level of wind energy (>30%) will be integrated into the power grid and major challenges and issues will appear, which are needed to be addressed for efficient and reliable operation of the existing power system.
Some of the turbines, including a controlling blade pitch angle control amount power can be transferred. Generator can be a synchronous or Asynchronous. Induction generators are being increasingly utilized in a WECS since they are relatively inexpensive, rigid, and require low maintenance. However, the impact of ever-changing windspeed on power quality, coupled with the need of excitation current for induction generator (IG), make the mechanical power control and voltage regulation indispensable to the wind- driven induction generatorsystem. By far, the most effective