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In view of the weak moment of inertia for power system with high penetration of renewable energy and limited transient voltage support of power electronics, a synchronous motor‐generator pair (MGP) is proposed as a possible solution for renewable energy integration to improve grid stability. In order to realize the large‐scale renewable energy integration, parallel inverters drive MGP is an ideal control scheme. Firstly, the working principle and mathematical model of MGP are introduced. Then based on a comparative analysis of control of parallel inverters and torque control of synchronous motors, the decoupling vector control method of MGP is proposed. Considering the linear relation between q‐axis current and the active power in the rotor flux‐oriented mode, the strategy of parallel drive for MGP with vector control is established. Different control loop for off‐grid and grid‐connected operation is designed, and effectiveness of this control strategy is verified by simulation. Finally, a 5 kW MGP experimental platform with dual inverters is built, the parameters are selected to test stability of the system, and power distribution and efficiency are studied. The results indicate that the parallel operation of MGP is stable under dynamic conditions, the strategy can realize the independent control of each inverter.

This study describes the research to improve the performance of motor generator for integrated starter generator (ISG) mounted on ecofriendly vehicles. The ISG must be able to start the engine by high torque at the starting mode and generate electric power at the generating mode. In particular, the existing automotive generator is a field winding alternator of CLAW POLE structure, so wound field synchronous machine (WFSM) was used in early ISG. However, it is difficult to control the starting of WFSM with instantaneous high starting torque required at the start and high field current is applied to field windings to generate the magnetic flux. But high field current generates high heat shortening the life of the device. Therefore, consequent pole wound field synchronous machine (CPWFSM) as a novel structure is proposed in this article. It is possible to generate instantaneous high torque easily at starting because of permanent magnet (PM). In the generating mode, CPWFSM can generate power in a wide operation speed that is proposed by taking advantage of WFSM. CPWFSM consists of consequent pole and field winding in the rotor. So it generates high torque with high responsiveness at starting compared with WFSM and it has the advantage of generating output power using low field current at various speed areas because of PM. Simulation of CPWFSM and WFSM is performed by finite-element method (FEM) of ANSYS Electromagnetic Suite (EM 19.0) software, and the experimental results are compared by the dynamo experiment.

The increasing penetration of renewable energy leads to the decrease of inertia and damping for replacing conventional power plants. The motor–generator pair (MGP) is proposed to improve inertial response and frequency regulation capability for the renewable energy. First, the mathematical model of the MGP and the control method of DC‐link voltage are given. Then, the inertial characteristics of the MGP are analysed, and a mass block is designed by analysing the key factor affecting the moment of inertia. The transient processes in two machines are discussed by comparing the variations of the voltage and current vectors. It turns out that the electromagnetic–mechanical coupling is the key to realise the primary frequency regulation without frequency acquisition. The photovoltaic (PV) is chosen to illustrate the mechanism of achieving a better primary frequency response with DC‐link voltage control methods based on the de‐loading and additional frequency deviation strategies. A grid‐scale simulation model is built to verify the effectiveness of the proposed scheme. Furthermore, six groups of experiments are designed and performed on an experimental bench. The simulation and experimental results demonstrate that the inertial response and primary frequency response of PV can be improved effectively by adopting MGP for grid connection.

Power-hardware-in-the-loop (PHIL) is a vital technique for realistic testing of prototype systems. While the application of power electronics-based amplifiers to enable PHIL capability has been widely reported, the use of motor-generator (MG) sets as the PHIL interfaces has not been fully investigated. This article presents the realization of the first MW-scale PHIL setup using an MG set as the power amplifier, which offers a promising solution for testing novel systems for the integration of distributed energy resources. Uniquely, this article presents a methodology that introduces augmented frequency and phase control loops that can be integrated to commercially-available MG set's existing frequency controller for precise frequency and phase tracking. Internal model control is used for the controllers design and tuning. The developed control algorithm is tested in a MW-scale MG set that couples a Great Britain (GB) transmission network model simulated in a real time simulator to an 11 kV distribution network. Experimental results are presented, which demonstrate that the proposed control methodology is highly effective in maintaining the synchronization between the simulated and physical systems, thereby capable of enabling the MG set as a PHIL interface.

This article considers the control problem for a motor/generator set, where a prime mover drives a generator and the electrical power produced drives a motor. Both the generator and the motor are assumed to be doubly fed induction machines with direct ac connection between their stators. The rotors are controlled by three-phase converters, so that operation is possible with motor and generator speeds that are different from each other, and not synchronized with the electrical frequency of the stator voltages. The strong couplings between the two machines motivate the design of an integrated controller. This article proposes a general framework for such a design based on a joint model of the two machines. A specific method is also developed for the control of the stator voltages and the motor velocity. In its simplest form, the proposed algorithm does not rely on current sensors. A current command option is also developed that ensures closer tracking and limiting of the rotor currents. The algorithm is relatively simple and all its parameters can be computed based on the estimates of the machine parameters. Practical implementation and testing can be performed rapidly. Experiments performed on a small-scale laboratory testbed show very good tracking performance of a speed reference profile.

One of the areas for improving military tracked and wheeled vehicles is considered, nmely the use a hybrid power plant. A problem is determining the effectiveness of using a hybrid power plant in military vehicles. An analysis of foreign samples the military tracked and wheeled vehicles with an integrated hybrid power plant and their technical characteristics is carried out. A selection of traction electrical equipment for the construction a hybrid power plant for a tank and an armored personnel carrier was made. The technical characteristics of traction electric motors are considered: SUMO HD HV3500-9P company DANA (Canada), EMRAX 348 company Enstroj (Slovenia); traction Li-ion battery company WB Electronic (Poland), SUMO HP HV900-3P motor generator (LSG130 generator) DANA company (Canada). A study was done on the composing а components of the hybrid power plant in engine and transmission compartment and the hull of the T-72 tank, BMT-72 heavy infantry fighting vehicle and BTR-4MV1 armored personnel carrier. The study was conducted by modeling and comparative analysis. The simulation was carried out in a computer-aided design system Creo Parametric 2.0. As a result of the study, the technical characteristics of the BMT-72 and BTR-4MV1 products were determined with the introduction of a hybrid power plant on them. It was found that the use of a hybrid power plant on the BMT-72 product did not lead to improvement in speed characteristics and increase the power reserve, in addition to ensuring movement on traction batteries up to21 kmon a dry dirt road. The use of a hybrid power plant on armored personnel carrier BTR-4MV1 improves its maneuverability when applying a power transmission scheme from a traction motor to each wheel separately, provides movement on traction batteries up to53 kmon a dry dirt road. The total power reserve will be no less than the base product, since the capacity of the fuel system did not decrease. The estimated maximum speed of an armored personnel carrier with a hybrid power plant corresponds to the maximum speed of the base product and is110 km/h. The introduction a hybrid power plant on military tracked vehicles weighing 40-50 tons is not advisable due to insufficient electric power, large overall dimensions a traction batteries and large mass of the product. A promising direction is the introduction a hybrid power plant on military wheeled vehicles weighing up to 30 tons. To implement a hybrid power plant on armored personnel carrier according to the scheme of transferring power from the traction electric motor to the wheel, it is necessary to develop a gearbox design with two gears.

Renewable energy units are required to have reliable fault ride-through capability to prevent large-scale disconnection of renewable energy plants due to grid faults. Since synchronous generators have better voltage and current resistance capabilities, one of the advantages of renewable energy connected to the grid through the motor-generator Pair (MGP) system is the isolation of grid faults, which is totally different from existing fault ride-through methods. First, the structure and mathematical model of the MGP system are introduced in this paper. Then, a novel control method for the MGP system based on DC link voltage feedback is given, which is very important for fault ride-through in the control power balance on both sides of the DC bus. The isolation mechanism, damping and reactive power support functions of the MGP system on grid faults are analyzed by means of the rotor motion equation and phasor diagram of synchronous machine. A 5-kW MGP simulation and experimental platforms are built to verify the isolation and protection effects of the MGP system on a renewable energy generation system during the transient processes of grid voltage sag, overvoltage and multiple voltage sags. The results demonstrate that the MGP system can isolate grid faults on the generator side, while the oscillation amplitude on the motor side is much smaller, and the generator can provide strong reactive power support to the grid during three grid faults.

Advantages of planetary gear powertrain (PGT) for electric vehicles (EVs) are the high degree of efficiency, various reduction ratio, stress distribution by the planet gear and compaction in designing driving system. However there is noise in running at high rotational speed, so the transient torsional vibration suppression of the PGT for EVs become extremely essential and urgent. This study presents a 4 + N degree of freedom (DOF) nonlinear torsional system that essentially describes a PGT of EVs example, and further study on influence of novel TSB modification on transient vibration of planetary gear powertrain for an electric vehicle. In particular, the vibration of the PGT during the speed-up process, as excited by dynamic torque of motor generator (MG), time-varying mesh stiffness of front and back gear teeth, and also teeth backlashes, are investigated using a nonlinear torsional transient model. Then a full PGT model during the speed-up process is proposed and numerically solved to obtain the transient vibration acceleration. Dynamic response results of the PGT are also successfully compared and analyzed under different teeth backlashes. Finally, an improved genetic algorithm is applied to construct optimal relationship between the transient vibration and the TSB modification, and further the optimum three-dimensional TSB modification of sun-gear is finally obtained. The simulation and experiment results indicated that the proposed novel TSB modification method effectively suppressed the PGT transient vibration and vehicle jerk, at the same time, improved the ride comfort during the high-speed driving mode.

Electrifying the ground vehicles is a promising approach to alleviating the energy and climate issues. The adoption of an electric vehicle (EV) and a hybrid EV (HEV) has introduced significant impacts on various aspects of vehicle design, especially on the chassis systems. When vehicles tend to be lighter, smarter, and autonomous, more electroactuators with a wide-bandwidth control and an energy-regeneration capability are deployed instead of traditional hydraulic ones to improve the vehicle dynamic and energy performance. In this article, an overview of the chassis electrification technologies regarding different configurations of electric/hybrid powertrains, active suspension, and steering systems, along with a comprehensive review of key research fields on the design and control of the discussed systems, is presented. For related technologies, the comparative discussions and design considerations serve as a reference for practical research and development. Although the electric solutions in different subsystems show great potential to further benefit the essential chassis functions, a fully electrified chassis still has a long way to go considering the technical maturity and the cost–performance tradeoff. This article also highlights the technical gaps and supplies future directions for the chassis electrification.

Aiming at the stability problems caused by low inertia, weak damping and low short circuit capacity of photovoltaic (PV) systems, this paper puts forward the motorgenerator pair (MGP) as a new way for grid-connection. Firstly, the control method and structure of PV connected to the grid via MGP are described. Then, the moments of inertia of PV with or without MGP under the same capacity are compared. The second- order small signal model of MGP is built to analyze the damping characteristics of MGP. And the short-circuit ratio is used to analyze the effect of MGP on the grid strength. Finally, the simulation model is built by PSCAD/EMTDC to verify the improvement effect of MGP on low inertia, weak damping and abundant harmonics of PV systems.

Characterization of motor parameters is a requisite for electric motor-based applications. Extraction of the torque–speed characteristics involves intricate and expensive instrumentation. In research areas of vehicular technology and power generation, such estimation plays a vital role. An effortless technique to evaluate these parameters without the use of complex systems can prove quite advantageous especially when electric vehicle design is concerned. This paper presents a simple and low-cost technique to evaluate direct current motor characteristics on a dynamic application platform. The proposed system uses a motor generator coupling technique to extract motor parameters essential when observing load information of motors in electric vehicles. The system consists of two motors coupled through a shaft, a power circuit unit, sensors and a data acquisition system. The load is electronically applied to the system so that the motor can be tested at various loading conditions. The results obtained are in congruence with data available in commercial datasheets and leads to the conclusion that the proposed method is reliable, cost effective, and can also be used to analyze motor characteristics at a varied range. This system can be effectively used in the development of test bed designs for electric vehicles as well as study the loading conditions of a driving motor on dynamic road conditions.

Energy storage is an emerging technology that can enable the transition toward renewable-energy-based distributed generation, reducing peak power demand and the time difference between production and use. The energy storage could be implemented both at grid level (concentrated) or at user level (distributed). Chemical batteries represent the de facto standard of storage systems for performance and maturity; however, batteries feature a quite large environmental footprint and use precious raw materials. Mechanical storage technologies could represent a viable alternative to chemical batteries, because of their reduced impacts on the environment and on raw materials. This article presents the design of a motor/generator for a flywheel energy storage at household level. Three reference machines were compared by means of finite element analysis: a traditional iron-core surface permanent-magnet (SPM) synchronous machine, a synchronous reluctance machine (SynchRel), and an ironless SPM synchronous machine. Simulation shows that the ironless machine is good candidate for distributed energy storage, because of its high efficiency, high discharge duration, and low losses. A prototype ironless machine was designed and manufactured. Experiments confirm the simulation results.

The renewable energy grid-connection has a negative influence on the transient stability of the power grid for the lack of voltage support and damping control capability. This paper aims to study the functions of the novel MGP system on improving the stability of renewable energy power grid with its advantages of synchronous machines. First of all, the structure and motion equation of grid-connected renewable energy via MGP is given. Then the mechanism of improving voltage stability is analyzed through the phase diagram of two synchronous machines. It turns out that the output reactive power of the generator can respond to voltage disturbance spontaneously. Afterwards, the function of excitation voltage on damping frequency disturbance is studied. In order to test the real characteristics of MGP, the grid voltage drop and load increase are conducted on the experimental platform, respectively. According to the results, grid-connected PV via MGP can perform well on providing reactive power support spontaneously and the effects of damping the frequency oscillation can be improved through the optimization of excitation voltage.

В роботі досліджуються можливості використання кінетичних акумуляторів енергії для вирівнювання графіка добового навантаження енергосистеми. Було розроблено модель кінетичного накопичувача енергії в середовищі «MathLab». In work study the possibility of using kinetic energy accumulators to equalize the schedule of daily load of the power system; development of a model of kinetic energy storage in the environment "MathLab". В работе исследуются возможности использования кинетических аккумуляторов энергии для выравнивания графика суточной нагрузки энергосистемы; разработка модели кинетического накопителя энергии в среде «MathLab».

Flywheel-based energy storage systems are gaining prominence in present-day energy-deficit situation. For energy storage system, the bearings and motor cum generator, for charging and discharging energy to and from the flywheel, form the vital components which have to be given due consideration. The low coefficient of friction of high-temperature superconductor bearings used in flywheel-based energy storage systems decides the energy loss factor. Yttrium Barium copper oxide (YBCO) which is one of the popular high-temperature superconductors is widely being used in high-temperature superconductor bearings. The planar type of bearings can be materialised by building the stator of the bearing with YBCO bulk high-temperature superconductor discs mounted in a circular array and rotor part can be realised by Nd–Fe–B permanent magnet ring which is to be embedded with the flywheel. The levitation force is proportional to the mean magnetization of high-temperature superconductor and the horizontal gradient of the vertical component of the magnetic field density in the superconductor. The magnetization is proportional to the product of critical current density and the grain diameter of the bulk superconductor. The high-temperature superconductor bearings outweigh the magnetic bearings because their passive nature, by virtue, does not require any external active stability balancing devices. The paper discusses of development, fabrication and load testing of prototype planar type of high-temperature superconductor bearings. For charging and discharging energy to and from the flywheel energy storage system, Halbach array-type motor cum generator is a promising candidate. The motor, with an outside rotor design, is a dipole Halbach array, establishing a uniform flux within the stator area. A uniform flux is needed for operating the motor on a superconductor bearing, where slight movement of the stator inside the air gap is inevitable. The salient construction features of the prototype Halbach array motor generator will be discussed.

With the increasing penetration renewable energy, some changes are transforming the power system dynamic characteristics, resulting in new stability issues. One of the issues is the lack of inertia and damping. One is sub-synchronous oscillation (SSO) caused by inter-harmonics associated with inverter-based renewable power generators (IPRG). A novel technology is proposed to transmit stable and high-quality power for power system with high penetration of renewable energy. Thus, the object of this paper is synchronous motor-generator pair (MGP) system, a new gird-connection device, which is proposed to solve above problems. First, the two mass block shaft model of MGP is established, which verifies the small signal stability of this system, and it has high damping that can be controlled flexibly. Then, the harmonic response of MGP is analysed through the internal electromagnetic relationship. Result shows that comparing with the input power from renewable energy sources to M side, the harmonic content of output power on G side is greatly reduced, especially the even harmonic. These characteristics are verified by experiments. So transmitted by MGP, the power quality and stability are greatly improved.

Background: Recently, environment friendly technologies are being introduced as global warming is rapidly progressing. One of the effective way to reduce the problem, Electric Turbo Compounding System has been researched globally. With this system, about 30% exhaust gas can be recycled as a power source. Therefore, this system is effective for engine systems with purposes such as downsizing and increasing efficiency of the system. Objective & Method: Surface mounted Permanent Magnet Motor is applied to this system due to its high efficiency, power density, small size, and low weight. However, during high speed operation, a retaining sleeve is essential in rotor such as Inconel 718 to satisfy a mechanical safety factor of the rotor. In this paper, through basic theory, the sleeve thickness is predicted according to the permanent magnet dimension and minimum sleeve thickness is determined satisfying mechanical safety factor by mechanical analysis. Furthermore, by electromagnetic analysis output characteristics according to the permanent magnet dimension having same constraints such as volume, current density, current and flux distribution are compared. Result & Conclusion: Based on the results of the electromagnetic analysis and mechanical analysis, the appropriate ratio of electric and magnetic loading is determined with equivalent constraint condition. Consequently, only model 2 satisfies the requirement at rated and maximum speed within the current limit.

In this article, the industrial application of three-phase H-bridge inverter fed PMBLDC drive system with its regenerative braking and motoring modes of operation produce electric energy ha...

This paper presents the results of a case study carried out in a warehouse, and, in particular, the technical data obtained from field visits and a proposal for energy saving. The proposal entails incorporating a cogeneration system based on a motor generator (400 kWe ISO) to produce electrical energy, and an absorption cooling system (75 TR) that uses residual heat to generate air-conditioning. The absorption chiller consumed 54% less energy than the conventional air-conditioning system. Moreover, the produced energy can supply the plant’s total consumption, in addition to offering an excess of 57,312 kWh per month, which was reflected in the analysis of energy for sale to users with a high domestic consumption rate (DAC, for its Spanish acronym). The proposal’s total investment is USD 1,091,258, with a net monthly savings of USD 30,901, and an investment payback period of 2.9 years, which indicates the viability of this project according to its energy characteristics, notwithstanding that it is for a service provider company.

Three flywheel energy-stored impulse motor-generators (MGs) are used in the power supply system of HL-2A tokamak to produce short high-voltage or high-current pulse of desired parameters that are usually used for magnetic field coils and auxiliary heating equipment loads. The operation changing of these loads will cause disturbances in generator’s terminal voltage and the remarkable drop in MG’s rotating speed. This paper describes the implementation of an excitation controller using LabVIEW and CompactRIO for a 125-MVA impulse MG in power supply system of HL-2A/2M. Both a staged control strategy and digital PID algorithm built in LabVIEW are applied to the excitation controller that runs preciously in a 1-ms cycle to achieve voltage feedback control. The excitation controller, composed mainly of host computer and CompactRIO embedded reconfigurable system, is available to restore and stabilize terminal voltage in accordance with the desired voltage curves set by operators when pulsed loads and motor speed change quickly. It also implements real-time monitoring of the working condition and some electrical parameters of excitation system and communicates with central control system via Ethernet to either download discharge control files at time interval between two impulse discharges or upload waveform data generated in control process after a pulsed discharge. Engineering experiment results show that the use of excitation controller improves the voltage stiffness of the power supply system and provides the effective control of generator’s terminal voltage under the management of central control system.

This paper presents an $\mathcal {H}_\infty$ controller with an $\mathcal {H}_\infty$ state estimator using a linear parameter-varying (LPV) model of permanent magnet synchronous motor (PMSM). The proposed control method comprises a nonlinear torque modulation, an LPV $\mathcal {H}_\infty$ state estimator, and an LPV $\mathcal {H}_\infty$ state feedback controller. The use of nonlinear torque modulation enables formulation of the electromechanical dynamics of the PMSM in the form of an LPV system. The LPV $\mathcal {H}_\infty$ state estimator is designed to estimate the velocity, currents, and disturbance based solely on position measurement. We introduce a vertex expansion technique to cover all operating points of an LPV system. A velocity tracking controller is designed in the frame work of $\mathcal {H}_\infty$ control to be robust against disturbance. The proposed controller was implemented and validated with a motor generator set consisting of two PMSMs. Experimental results are presented to validate the effectiveness of the proposed method compared to conventional field-oriented control. These results show improved transient responses to velocity reference in the presence of disturbance.

The environmental problem is a major practical problem that China and the world are faced with. It is a trend for the future power grid to be dominated by the increasing penetration of renewable energy. However, the high penetration power system may face many new problems, including reduced inertia of the power system, the stability of the frequency stability, and the weak grid characteristics of the output system may limit the delivery capacity of renewable energy base. The motor-generator pair (MGP) system can deal with these problems efficiently, but the current MGP system control method is still flawed. In this paper, the mathematical model of the MGP system is analyzed. The characteristics of the source-grid difference control method is analyzed by simulation and experiment. In the experiment, the shortcoming of existing control method that the control system is sensitive to the power grid frequency change is found. The optimized control method based on power feedback is proposed. The feasibility of the power feedback control method is proved by the experimental and simulation. The result shows that the source-grid phase difference method based on power feedback can make the MGP system follow the power reference value to transmit active power stably and reduce the frequency sensitivity of the MGP system.

The Sun’s slow periodic flux transfer to the Earth, the low frequency of Schumann Resonance, and the fixed DC voltage of the capacitor direct us toward direct current (DC) machines for electrical modeling purposes. The Earth exhibits dual characteristics of a motor generator set by motoring the mechanical Earth around its axis, while at the same time generating energy for its spherical capacitor. It follows that electrical and mechanical output of the Earth are powered by the magnitude of the flux transfer events, the constant DC voltage supply and any potential nuclear contribution within the core. Like an induction furnace, powerful magnetic flux from the Sun partially melts the outer iron core of the Earth and magnetizes the inner solid iron core. The solid inner magnetic core acts as a rotating armature similar to a DC machine. All electrical machines experience no load and full load power loss while in operation. Speed control of large rotating DC machines is well understood and has been applied in industry for over a century. Speed can be changed either by varying the field resistance and/or the armature resistance. The characteristic of a constant speed DC machine is such that a change in field resistance will cause a compensatory change in armature resistance to maintain velocity. In the case of the earth, a decrease in armature resistance results in an increase in volume of the iron core, which may result in greater seismic and volcanic activity. Climate change may be the direct result of changes in soil and sea water resistance, which we lump together as field resistance.

When the poloidal field (PF) magnet power supplies (MPSs) of 11 units are operated, maximum power of 200 MVA is required to achieve long pulse operation of Korea superconducting tokamak advanced research (KSTAR). Motor generator (MG) system was installed to resolve the power shortage because the available grid power is only 100 MVA at the National Fusion Research Institute site. MG system is composed of mechanical devices (stator, rotor, bearings, etc.), power control devices (variable voltage variable frequency and exciter), power facilities (transformers, switchboard, uninterruptible power system, filter, dynamic brake, etc.), utilities (cooling water pump, heat exchangers, cooling fans, oil circulation pump, mechanical brake, etc.), and control systems. MG system supplies power to the PF MPS of 11 units. And we configure the reactive power compensator (RPC) and harmonic filter (HF) system to stabilize the MG power system. After installing the MG system, individual tests and dummy coil tests were conducted to determine the safety and performance of MG system. And we completed the commissioning of the MG system by carrying out the superconducting magnet coil load tests for the 2014 KSTAR experiment. MG system was operated up to 150 MVA of PF MPS with the RPC and HF system. And the maximum operating duration was about 100 s. In this paper, we discuss about the power characteristic results of the MG system according to the superconducting magnet coil load tests.

The normal life of a transformer is well above 25 years. The economical operation of the distribution system has its roots in the equipments being used. The economy being such, that it is financially advantageous to replace transformers with more than 15 years of service in the second perennial market. Testing of transformer is required, as its an indication of the extent to which a transformer can comply with the customers specified requirements and the respective standards (IEC 60076-3). In this paper, induced over voltage testing on transformers using enhanced Z source inverter is discussed. Power electronic circuits are now essential for a whole array of industrial electronic products. The bulky motor generator set, which is used to generate the required frequency to conduct the induced over voltage testing of transformers is nowadays replaced by static frequency converter. First conventional Z-source inverter, and second an enhanced Z source inverter is being used to generate the required voltage and frequency to test the transformer for induced over voltage test, and its characteristics is analysed.

To predict the fatigue life of motor-generator rotor in a pumped-storage plant, the most dangerous position of the rotor under the highest applied load was found to be at the dovetail of magnetic pole and yoke after failure analysis and stress condition analysis. In this work, two types of steel sheets used to manufacture those parts were chosen to study the microstructures and mechanical properties, especially the fatigue properties. Based on those results, some methods including widely applied Forschungskuratorium Maschinenbau (FKM) method and modified one were used to predict fatigue life of the key parts. Considering possible influencing factors, based on the fatigue theories or methods to modify mean stress and predict fatigue life, a novel method, named key part life (KPL) method, was proposed briefly. The KPL method not only suits well for the motor-generator rotor, but also provides a new idea for life prediction of parts in engineering field.

Increasing penetration rate of renewable energy sources makes it a trend for power system to be dominated by power electronics, which brings challenges for reliability and stability: first, unlike synchronous generator, converters do not have inherent inertia which is important for frequency response. Second, more complex interaction induced by renewable energies causes problems of power system dynamics, for example damping oscillation. In addition, converters cannot support high fault current, leading to limitation of some existing control schemes during transient events. However, compared with converters, synchronous generator has some advantages to solve aforementioned problems. Therefore, this study proposes a synchronous motor-generator pair (MGP) system as a possible grid-connection way for high penetration of renewable energies to improve stability. State equations for analysis of small signal stability are established based on proposed equivalent rotor angle, which is verified by experiment. Results of mode shape analysis and transient simulation show that MGP can effectively enhance frequency response, damp oscillation and isolate and weaken the negative effects brought by wind farm. Effects on damping ratio with different proportions of MGP are also investigated in different penetration rates.

High penetration rates of renewable energy will bring stability problems for the future power grid. One of the critical issues is lack of inertia. In this paper, a synchronous motor-generator pair (MGP) system is proposed as a possible solution for renewable energy integration to enhance inertia and improve grid stability. First, feasibility studies of MGP on inertia, damping, efficiency, and cost are presented. Second, an analytical model is established based on its rotor angle relation. An active power control scheme based on voltage phase difference between renewable energy source and grid is then proposed, and state equations of MGP are derived for small signal stability. Next, two experiments are designed and implemented to verify stable operation and active power regulation of the MGP system. A single-machine infinite bus system is tested to investigate small signal stability and frequency response of MGP. The results show that the MGP system has a solid base in physics and is a feasible solution for providing enough inertia and improving small signal performance in the power grid with high penetration of renewable energy. The paper concludes with a discussion on future research directions to gain a better understanding of MGP.

With the advancement of technology, power demand is increasing day-by-day. Energy deficiency problem and increasing petroleum/diesel cost have resulted in severe impacts to many technical facts. Introduction of non-conventional energy sources such as wind and photovoltaic energy, which is clean and copiously present in nature, can be possible solutions to these problems. This chapter presents optimization of a Hybrid power system, with one of swarm intelligent algorithms named as particle swarm optimization (PSO). The hybrid system uses PID controllers for controlling its output. It has been done by studying various combinations of diesel engine generator, wind turbine generator, aqua electrolyzer, fuel cell, and battery. With the optimized system parameters, high-quality power supply can be delivered to the load and the frequency fluctuations can also be minimized.

In this practical project, an advanced reconfigurable communication unit is studied which is well-matched to be used in harsh agriculture environment. The unit transfers all data through SQL database and back-end with a UF (user friendly) web interface. It collects many data online from different sources like accelerometer, tensometers, CAN, temp. sensors and analog or digital inputs. The communication is based on Global System for Mobile Communications (GSM) and It uses GPS data to obtain accurate real-time localization for knowing where the machine is. The unit is powered with three different power sources. An external motor generator, a solar battery or a standard 12 V tractor battery. To enable the device working even without any of the above-mentioned power sources, an internal battery is also provided as a secondary source. The heart and novelty of the unit is a multifunctional Linux based Printed Circuit Boards (PCB) which would be described in detail. Several simultaneously working units, can be simply addressed using private standard network. The back-end lets the operators to organize chosen activities. One can select desired data to be detected. It is conceivable to arrange the time span between two different packages and the data acquisition rate which would be sent to back-end. Information are accessible via web interface and can be copied in CSV format for post processing. The whole system is also designed to capture user-defined data constraints and if such a constraint is touched, a warning message would be sent to a pre-defined contact.

Flywheel energy storage is considered in this paper for grid integration of renewable energy sources due to its inherent advantages of fast response, long cycle life and flexibility in providing ancillary services to the grid, such as frequency regulation, voltage support, etc. The fundamentals of the technology and recent developments are reviewed, firstly with an emphasis on the design considerations and performance metrics. Then the progress and development trends in electric motor/generators employed in flywheel energy storage systems (FESS) are summarized, showing the potential of axial-flux permanent-magnet (AFPM) machines in such applications. Design examples of high-speed AFPM machines are provided and evaluated in terms of specific power, efficiency, and open-circuit losses in order to validate their suitability in FESS.

Windup effect in a PID controller is the condition of cumulative error in the integral action. It saturates the system actuators, letting the system out of control with a higher controller action. Putting a saturator for the controller action, it is limited into a linear range of operating values. However, it does not eliminate the cumulative error of the integral term. This paper presents the speed control of a motor generator system using a digital PID controller with antiwindup method to eliminate the cumulative error of the integral term of controller action. Initially, a linear model of the motor generator system was identified. From the linear model of the system, a PID controller was designed using pole placement technique. Controller discrete implementation was performed using the backward difference discretization methodology. PID controller consider the antiwindup scheme and its practical implementation employing the Matlab Stateflow toolbox and a data acquisition card. Obtained results showed that the PID controller with antiwindup digital implementation has a good performance against external disturbances and random noise.

Based on power balance and stability of power grid, pumped storage power station plays an important role in modern power system. Motor-generator is the main equipment of a pumped storage power station. The fault rate and operation reliability of motor-generator is directly related to safe and stable operation of the power station and even the power grid. This paper summaries different types of faults with several examples of fault treatment of large-scale motor-generators, and puts forward corresponding countermeasures and suggestions, which provides a good reference for similar fault prevention and diagnosis.

Small capacity battery of fuel cell electric vehicles (FCEVs) may cause regenerative braking to become disabled halfway through long downhill. To prevent brake lost accident, FCEVs mount a huge discharge resistor which restricts hydrogen space. Then this paper proposes motor-generator loss increase control as a substitute for the resistor. The proposed method realizes sufficient braking force without charging the FCEV battery by converting the braking energy into the motor-generator and its inverter losses. The algebraic analysis of the current vector set-point of the proposed method using motor-generator parameters is clarified. Moreover the principle of the proposed method was verified by small scale experiments using 2-kW machine. By using the proposed method, it is possible to mount additional hydrogen tank instead of the resistor and extend the cruising distance.