Permanent-Magnet Synchronous Generator

One of the solutions to reduce fuel consumption of diesel generators (DG) is to adapt the rotational speed to mechanical torque of the crankshaft. When load power decreases, a reduction in both mechanical torque and rotational speed of the diesel engine will maintain the combustion efficiency near the levels of the nominal regime. Accordingly, the generator itself should oper- ate at a variable speed which normally requires power electronics conver- ters. In this paper, we are exploring a new generator concept that uses a stator rotating in opposite direction to the rotor such as the relative velocity between the two components remains constant when diesel engine slows down. The stator itself is driven by a compensator synchronous motor (CM) such as the relative velocity of the rotor is constant, eliminating as such sophisticated power electronics. The model developed for the syn- chronous machine with a rotating stator is based on Park’s transformation. This new concept was modelled using MATLAB software. Experimental analysis has been conducted using a 500-kW diesel GENSET equipped with a permanent magnet synchronous generator (PMSG). The numerical and experimental results are in good agreement and demonstrate that fuel con- sumption is reduced with a rotating-mode stator for PMSG during low electrical loads.

popularity in the past decades due to the increasing energy crisis of which PV and Wind energy systems are the common ones. Microwinds are wind energy systems having rated power less than 5 kW. In micro wind turbine applications, permanent magnet synchronous generator (PMSG) is widely used. A novel algorithm for the estimation of rotor angle of the PMSG, based on flux estimators was implemented. The comparison involves the investigation of active and reactive power given to the grid through an ordinary diode rectifier and an active rectifier. The study demonstrates that active rectifier control shows superior performance in various aspects. Using active rectifier maximum power from the wind turbine can be extracted. Excessive power loss and braking torque can be avoided by the smooth start up operation of the PMSG.

Since wind speed is highly unpredictable in nature and the output of wind energy conversion system (WECS) varies continuously with time. Thus, to achieve high efficiency, variable-speed wind energy conversion systems (VSWECS) like doubly-fed induction generator (DFIG) and permanent magnet synchronous generator (PMSG) based systems are preferred over fixed-speed WECS like squirrel cage induction generator based systems and maximum power point tracking (MPPT) algorithms are incorporated for maximizing energy harvest. However, choosing an appropriate MPPT algorithm for a particular case requires sufficient proficiency with each because each algorithm has its own merits and demerits. For this reason, a review of those algorithms is essential. The article is divided into four sections including the introductory section. These sections are as follows: the basic idea of maximum power tracking is given in Section 2. The classification of various MPPT algorithms is made in Section 3, and Section 4 provides the conclusion.

Small scale stand alone wind generators are a significant different source of electrical energy. Unluckily, most of these systems do not capture more power at every wind speed. Particularly, at low wind speeds which are provide low power. To address this problem, this paper has been proposed a permanent magnet synchronous generator (PMSG) and Z- source inverter. This generator is connected to the power network by means of a Z-source inverter. Permanent-magnet synchronous generators are having some amazing characteristics such as with a reduction of burden and level, advanced performance, minimized size of gear box and no need of external power in permanent magnet excitation. The PMSG defeat the all other generators, marvelous performances without absorb the grid power.This paper presents a Z-source inverter that can be proposed as an option power conversion concept for variable speed wind turbines. It consist both buck and boost capabilities as they permit the inverter to perform the shoot through state. It utilizes a special Z-source network (L-C network) to DC-link in between inverter and the DC source. By controlling the shoot-through duty cycle of IGBTs in inverter system, we can diminish the line harmonics, develop power factor, and enlarge output voltage range.

This script depicts the power quality intensification of Wind Energy Transfer System (WETS) using Permanent Magnet Synchronous Generator (PMSG) and Cascaded Multi Cell Trans-Z-Source Inverter (CMCTZSI). The PMSG knocks the induction generator and earlier generators, because of their stimulating performances without taking the frame power. The Trans-Z-Source Inverter with one transformer and one capacitor is connected newly. To increase the boosting ratio gratuity a cascaded im- pression is proposed with adopting multi-winding transformer which provides an option for this manuscript to use coupled inductor as an alternative of multi-winding transformer and remains the matching voltage gain as cascaded multi cell trans-Z- source inverter. Accordingly the parallel capacitances are also balancing the voltage gain. The parallel correlation of the method is essentially to trim down the voltage stresses and to improve the input current gain of the inverter. By using MALAB Si- mulation, harmonics can be reduced up to 1.32% and also DC side can be boosted up our required level 200 - 1000 V achievable. The new hardware setup results demon- strate to facilitate the multi cell Trans Z-source inverter. This can be generated high-voltage gain [50 V - 1000 V] and also be credible. Moreover, the level of cur- rents, voltages and Harmonics on the machinery is low.

Simulations are carried out, in order to prove the wind turbine model and the effectiveness of the proposed con- trol strategy. The block simulated is represented by Figure 7. It include, the different parts of the Wind Energy Conversion System [1] [11] such as the wind turbine model that has as input the electromagnetic torque T em and the mechanic rotational speed Ω as output. The permanent magnet synchronous generator model which has three inputs; the two voltage components u q and u d and the electric rotational speed of the wind turbine

Since wind speed is highly unpredictable in nature and the output of wind energy conversion system (WECS) varies continuously with time. Thus, to achieve high efficiency, variable-speed wind energy conversion systems (VSWECS) like doubly-fed induction generator (DFIG) and permanent magnet synchronous generator (PMSG) based systems are preferred over fixed-speed WECS like squirrel cage induction generator based systems and maximum power point tracking (MPPT) algorithms are incorporated for maximizing energy harvest. However, choosing an appropriate MPPT algorithm for a particular case requires sufficient proficiency with each because each algorithm has its own merits and demerits. For this reason, a review of those algorithms is essential. The article is divided into four sections including the introductory section. These sections are as follows: the basic idea of maximum power tracking is given in Section 2. The classification of various MPPT algorithms is made in Section 3, and Section 4 provides the conclusion.

Recently, the global energy consumption has seen an enormous increase due to the massive industrial development, which tends to increase in size. China is one of the world’s countries which represent a remarkable case of this increased consumption of energy. The risks of scarcity of fossil fuels and their effects on climate change once again highlight the importance of renewable energies, particularly the wind turbine which has been identified as one of the most promising. The evolution of the wind turbine has grown in recent years, which has been given enormous attention as a privileged technology that represents an interesting alternative especially for the production of electrical energy. In this paper, we focus on the variable speed wind energy conversion system (WECS) due to its many advantages, such as a reduced torque oscillations and mechanical stress and a better exploitation of available wind energy compared to the fixed speed WECS. In this paper, we aim to study the interconnection characteristics of a permanent magnet synchronous generator based wind turbine from a wind turbine emulator based on the principle of control of a DC machine. The main objective is to develop a MPPT control method in order to adapt the speed of the turbine with respect to the wind speed, in order to maximize the converted power, this will improve their integration to the electrical networks.

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 variable speed wind turbine technology 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 variable speed wind turbine can be enhanced significantly by using a low speed permanent magnet synchronous generator (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.

Apart from the background knowledge, wind turbine type, as well as the wind energy development introduced in the first chapter, this thesis also focus on analysing the control strategy of wind turbine maximum power point tracking (MPPT). In order to model wind power generation, the mathematic models corresponding to wind turbine devices, i.e., turbine rotor, drive train, and electrical machine, are introduced in Chapter 2. MPPT allows wind turbine to deliver maximum power to the grid at different wind speeds, and hence improves the power generation efficiency. The conventional way to carry out MPPT control is by the classic vector control, where the electrical machine stator current is transformed into d and q axis current. By setting the d-axis to nil this enables the full capability of q-axis stator current which determines machine torque. This technique has been widely used due to its simplicity and reliability. The MPPT of permanent magnet synchronous generator based wind turbine is given in Chapter 3.

In order to analyze the performances of directly-driven permanent magnet synchronous generator wind turbine (PMSG) connecting to the grid, photovoltaic array and microtubine, dynamic models of them are established. The validity of the established models and proposed control strategies are demonstrated by simulation system under the software package PSCAD/EMTDC.

and output powers. Direct drive wind energy conversion systems based on multipole permanent magnet synchronous generator (PMSG) have some advantages such as no gearbox, high power density, high precision and easy to control. Three different schemes for generator are given in order to obtain an optimum rating of a PMSG and its power converter. In our research project, a direct drive wind energy conversion system is developed. The traditional way to test the converter is using resistance loads. An efficient experimental method can collect the energy which is wasting on the loads. A large circulating current flows in the converter, but only a small part of the current caused by the losses of the converter flows into the grid. The method can save a lot of energy when the converter is tested and the experiment can be done in the micro grid. The method can test the main stage, drive circuit, protect circuit and some parts of control circuit. The method has some advantages, such as low power losses and easy to control. Modeling and control scheme of the efficient experimental method are introduced in this paper, as well as the control scheme of the grid side converter.

Figure 1 represents the wind energy conversion system used for the verification of the algorithm. A three-phase boost rectifier is used to simplify the control process and thus allows easy verification of the algorithm [6][8]. As for the generator, a Permanent Magnet Synchronous Generator (PMSG) is used due to its high efficiency, small size and no slip rings are necessary [3]. In Figure 1, ωgen is the generator angular speed; dcycle is the duty ratio, Vdc and Idc are the average voltage and current of the boost converter respectively. The MPPT control in this system is therefore obtained by changing the duty cycle of the switch of the boost converter. The use of the boost converter in Fig. 1 also allows Power Factor Correction (PFC) to be achieved at the output terminals of the PMSG.

Abstract The paper presents the modeling and performance analysis of a standalone wind system in MATLAB/SIMULINK environment. Stand-alone systems using renewable energy sources, such as wind energy with storage battery banks are commonly used to supply remote houses. The model of wind turbine is developed using basic circuit equations governing the operation of the wind turbine. Permanent Magnet Synchronous Generator (PMSG), which is based on variable-speed operation, has been used in this paper. Since the speed of wind turbine is variable, the generator is controlled by power electronic devices. A rectifier is used to rectify the output voltage of PMSG and DC/DC buck converter is used to decrease this rectified voltage to that of battery and connected DC load. The buck converter is controlled to extract the maximum power output of wind system. Firstly the mathematical modeling of a wind turbine is done and its different characteristics have been obtained for different parameters. Secondly a standalone model of wind system is modeled and analyzed. This paper is useful to model, simulate and study the effect of change in wind speed of a standalone wind system.

Wind turbines capture the power from the wind by means of aerodynamically designed blades and convert it to rotating mechanical power. The generator converts the mechanical power into electrical energy, which is fed into a grid through power electronic converter. The connection of wind turbines to the grid is possible even at the extra high voltage system since the transmittable power of an electricity system usually increases with increasing the voltage level. It is desirable to operate wind energy system at its Maximum PowerPoint (MPP) in operating region for economic reasons. The amount of mechanical energy that can be extracted from wind is not only depending on wind speed, but also depending on the wind turbine rotational speed. The wind turbine rotational speed can be adjusted as the wind speed changes to tracking the maximum power point in the operating region. A unique limitation of energy conversion systems such as wind and solar is their inability to track peak power production efficiently at varying wind speeds and solar insulation respectively.

In the power generation industry, the electromechanical conversion of energy plays a vital role. Therefore, improving the efficiency of the generators is extremely significant in order to fulfill the energy demands around the world. Usually in a system where the energy is converted a high amount of energy is lost in conversion in terms of mechanical transmission, power loss in the wires etc. Studies show that using a permanent magnet design inside a generator or motor can improve the efficiency of the system. With more research on this type of technology a good design can be generated solving one of the main problems faced by the power generation industry. Permanent magnets have been in the market for a very long time now but recently due to advancement in power electronics controlling the operation of the motors a good increase in permanent magnets based designs is observed [1]. For wind turbine application the main things to consider are high torque and efficiency on low speeds. Because the wind does not move the rotor at a high speed it just moves the rotor at low speed therefore the torque must be high [2]. Permanent Magnet Generators were introduced in the wind turbines in the early 2000s. Ever since then the market for these types of generators is on a boom. In the past 4 years starting from 2011 until now the use of permanent magnet generators has increased radically.Statistics show the increase to be from 17% to about 40% which means the future is bright for this type of technology. The main reason for the increase is that using PMGs increases the efficiency along with flexibility and reliability [3].

Recent trends indicates a significant increase in large wind farms with PMSG based gearless direct drive wind turbine technology due to their advantages over induction generator based wind turbine with gearbox. These turbine generators will be connected to the grid through a full scale power electronic converters and expected to have capabilities of voltage/frequency regulation, reactive power support and fault ride through to maintain stable operation and to keep them connected to the grid under various disturbances. Therefore, it is necessary to design and develop reliable and efficient control strategies for PMSG based direct drive variable speed wind turbines to meet the grid code requirement. As the wind penetration into the grid is increasing, an efficient and reliable controller for the wind turbine is very important. This research will investigate the control strategies for a direct drive variable speed wind turbine with interior permanent magnet (IPM) synchronous generator. The main aims of this research include; analysis and modelling, improved controller design and implementation and application of supercapacitor energy storage to ensure dynamic voltage stability and reliable system operation.

The PMSG is considered, in many study articles, a fine choice to be used in WECS, due to its self-excitation possessions, which allows operation at good power factor and efficiency. PMSG won't need energy supply for excitation, as it is given by the permanent magnets. The stator of a PMSG is wound and the rotor has a permanent magnet pole system. The salient pole of PMSG working at low speeds, so the gearbox (Fig.2.1) can be detached. This is a huge benefit of PMSG-based WECS as the gearbox is a sensitive tool in wind power systems. The similar thing can be get by with direct driven multi pole PMSG with more diameter. The solidity of a wind rotor is the ratio of the projected blade area to the area of the wind intercepted. The tip speed ratio (TSR) of a wind turbine is defined as the ratio of the speed of the tip of the blade to the speed of free wind. Power coefficient of a wind turbine is the instantaneous efficiency of conversion of wind energy into mechanical energy of the shaft.

The wind speed is set to 12 m/s for first 3s and it is set to 25 m/s up to 7s the again 12 m/s up to 10s. In this the base speed is set to 12m/s. From Fig (9) the generator speed crosses more than 1.5 p.u which is 2550 rpm. In Fig (10) it is shown that the generator speed is controlled to 1.2p.u at the excess wind speed (25 m/s). And parameters like generator torque and output voltage are also controlled. Fig (11) shows the control of DC link voltage is shown. The disturbance occurs at .25s of the simulation period. But the system is providing a constant voltage over the entire simulation period because of the control of the rectifier as explained in section [V].

Permanent Magnet Synchronous Motors (PMSM) are attracting growing attention for a wide variety of industrial applications, from simple applications like pumps or fans to high performance drive like a machine-tool servos. This is due to their main characteristic: high power density, high torque to inertia ratio and high efficiency.