The analysis and design of a parallel AC to DC CUK converter circuit based on power balance control technique for DC Distributed Power System (DPS) applications are presented. The three parallel modules system with fast dynamic response using single voltage loop control and inductor current calculator for input current wave shaping, inductor current sharing and output voltage regulation, while keeping the power factor very close to unity have been shown. The experimental prototype have been built with a DC output voltage -48V and output power 750W. Each converter operates in Continuous Conducting Mode (CCM) together with hysteresis current control. The experimental results indicate that such scheme is effective and offers the fast transient response. The results obtained are: power factor greater than 0.99 and input current Total Harmonic Distortion (THD) less than 3%. The system offers 85% efficiency and provide good current sharing among the converter modules.

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A unique generating system for Gas heat pump system (GHP) is presented. The GHP is an air-conditioning system, in which the compressors are driven by a gas engine. The proposed system is applied to the outside unit of GHP to feed the electrical equipments inside. The system utilizes a permanent magnet synchronous generator, which is connected to the gas engine, to realize high-efficiency and small-size. The generator is controlled by a converter with sensorless control technology to eliminate the position sensor. Another major topic is the “free-run startup" technique to start the converter when the generator is rotating. The system configuration and principles of the techniques are set forth, followed by experimental results which show that the system works properly and successfully.

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E-learning with pre-solved animations can provide a better understanding of the status and different network options, compared to complex simulation or a set of equations. In this paper, examples of such animations for e-learning for power quality are presented. Different network options in a centralized or distributed power system and power electronics based compensators are introduced in the form of a new web-based, software learning tool. Power flow congestion and the impact of power electronic compensators on the system, including detailed operations of power electronic based compensators are presented. These compensators include SVCs, Statcom and UPFC presented in this paper. Using these animated tools, both system level and component level operation of these devices are presented. Further the frequent solutions of power factor correction (PFC) applied on low power level of several hundred watts are treated in the paper.

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The new constitution method of the wind power generation simulator considering output characteristics of the windmill is proposed. The rotational speed of the windmill changes by not only wind velocity but also condition of the load connected with the generator. Therefore, the technique which fed back the torque of the generator was verified for the estimation of the rotational speed in addition to wind velocity and characteristics of the windmill. Characteristics of the operation of the simulator resembled actual windmill, and the validity of the simulator was approximately confirmed. In addition, derivation technique of the maximum power point proposed in advance was applied to this equipment, and the operating characteristic was verified by the experiment.

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This paper presents a detailed analysis of circuit operation under ZVS and NON-ZVS conditions in a full-bridge high-frequency phase-shift control series resonant MOSFET inverter with the load of induction heating. Various modes of circuit operation both under ZVS and NON-ZVS conditions are first analyzed in details. The voltage and current equations of these circuits are then obtained and used for calculation of the waveforms by MATLAB program. The calculated results can lead to the consideration of various circuit parameters that determine ZVS or NON-ZVS operating conditions. The theoretical results are also verified by experimental ones, using a prototype test set rated at 3kW.

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The series-parallel resonant converter and its magnetic components are analysed by extended fundamental frequency techniques. The proposed model allows an easy design of the resonant circuit and the integrated transformer and the calculation of the losses of all components of the converter. The purpose of the presented analytic model is an optimisation of the converter system—minimising either the volume/power density or the losses of the converter (restriction: temperature rise). Moreover, the presented equations also include a ZCS condition for one leg of the converter, the control of the converter by the frequency and duty cycle and a load model with offset voltage. The proposed analytic model is validated by simulation as well as by experimental results.

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This paper undertakes a comparison of the very sparse matrix converter (VSMC) and the back-to-back voltage DC-link converter (BBC) for a permanent magnetic synchronous motor drive application. The VSMC has the same functionality as the conventional matrix converter but a reduced number of switches and lower control complexity. The two converters are designed, using the same IGBT power modules, with a switching frequency of 40kHz and a thermal rating of 6.8kW at an ambient temperature of 45°C. From the design, the volume of the VSMC is 2.3 liters and is half that of the BBC. The efficiency for the VSMC at full load is 94.5% compared to 92% for the BBC. At very low output frequencies the output current of the VSMC can be increased by 25% above nominal compared to a 54% decrease for the BBC. Overall the VSMC offers advantages in volume and efficiency for motor drive applications requiring switching frequencies above 10kHz.

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Unbalanced supply voltages can be fully compensated in boost type power converters with active front end if sufficient energy storage is provided by the DC-link capacitor. In converters that have no energy storage, for example in a matrix converter, the maximum voltage transfer ratio will be limited if one or more input lines is at a reduced voltage. Control techniques to compensate the effect of unbalanced voltage supply for matrix converters allow for a limited output voltage and power capabilities, which depends on the level of unbalance. This paper proposes the utilization of the clamp capacitor, which is normally needed to protect a Direct Power Converter (DPC), to extend the operating range of a Two-Stage DPC during unbalanced supply conditions preserving its theoretic maximum voltage transfer ratio capability. A new topology based on a hybrid approach, consisting of an H-bridge inverter inserted into the intermediary link, which is also able to preserve the output voltage capability under unbalanced supply conditions, is proposed. Both solutions are validated through simulations.

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The experimental results of an innovative power conversion technology using magnetic energy recovery switch (MERS) in a wind turbine system with a synchronous generator to improve the output power and the efficiency are presented. The MERS can compensate for the reactance voltage of the generator. The output voltage of the system increases and the excitation power of the generator can be significantly reduced. The data indicate a great potential of the new power conversion technology to make the actual wind turbine system compact and to improve the efficiency.

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The harmonic resonance in the power distribution system or in the industrial facilities has been reported. The harmonic termination by installing a shunt active filter at the end of a radial line can suppress harmonic resonance; however, the harmonic voltage distortion along the line may still be significant due to harmonics standing waves. The distributed active filter system, which consists of multiple active filter units deployed along the power line, can effectively reduce voltage harmonics. Based on the pre-determined droop characteristics, the active filter units can share harmonic filtering workload without any communications. In this paper, the distributed active filter system is applied to a radial distribution line and a loop distribution line, which is often used in high-tech industrial parks for enhancing power reliability. This paper provides the theoretic analysis of harmonic resonance, simulation results and laboratory test results to verify the performance of the distributed active filter system. The deployment strategies of active filter units are also presented.

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Novel exact MOSFET switching loss analysis and formulation methods have been proposed for designing high output power density converters. To analyze influences of circuit stray parameters on MOSFET switching loss with experiments, a parameter adjustable circuit board has been fabricated. The circuit board has a function to vary circuit stray inductance and capacitance values like a circuit simulator. Correlations between MOSFET switching loss energies and circuit stray parameters are successfully analyzed with the circuit board. Based on the analysis results, switching loss energies are formulated with empirical equations to establish a exact power loss calculation tool for the converter design. Switching loss energies caused by semiconductor device parameters are modeled by a capacitance charge/discharge model. The procedure to formulate the switching loss energies with empirical equations is presented. Switching loss energies calculated with empirical equations are verified with measurements, and high accuracy of more than 95% has been achieved.

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Currently, there is an increasing trend to connect large MW wind farms to the transmission system. Therefore the power system becomes more vulnerable and dependent on the wind energy production. At the same time requirements that focus on the influence of the farms on the grid stability and power quality, and on the control capabilities of wind farms have already been established. The main trends of modern wind turbines/farms are clearly the variable speed operation and a grid connection through a power electronic interface, especially using doubly-fed induction generators. Using power electronics the control capabilities of these wind turbines/farms are extended and thus the grid requirements are fulfilled. However, the traditional squirrel-cage generators based wind turbines/wind farms directly connected to the grid does not have such control capabilities. They produce maximum possible power in continuous operation and are becoming disconnected in the case of a grid fault. Moreover, these wind turbines/farms cannot regulate their production and contribute to power system stability. A DC transmission system for connection of the active stall wind farms to the grid can be a solution to these problems. Such a system has special regulating properties e.g. decoupled control of active and reactive power, continuous AC voltage regulation, variable frequency control, black-start capability, etc. This paper focuses on the modeling of such systems and proposes a control method of a voltage source converter based DC transmission system for connecting active stall wind farms to the grid.

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Decentralized control is a promising method with many advantages while an effective design method for it is desired. Design in conventional methods is complicated because the correspondence between a system role and its controllers is unclear. To solve this problem, we have proposed the idea of “functionality" for a bilateral control system. The idea is to divide the system role into minimum components. The design method based on this idea is clear since controllers correspond to respective functions. Furthermore, the design method is simple since each function is a minimum component. This study expands the idea of the functionality to design of decentralized control systems. Subsystems are constructed based on functions. Functions for normal operation and for exception handling are treated in a unified manner. The system can automatically sustain important functions by a priority order of functions. This method realizes simple and explicit controller design for a decentralized control system with exception handling. Simulation and experimental results show the flexibility, fault tolerance and expandability of the decentralized system.

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An interior permanent magnet (IPM) motor drive system which has regenerating capability augmented by double-layer capacitors is proposed. The motor is driven by a PWM inverter with voltage booster. The voltage booster is used to control the dc link voltage in high speed region to improve the system efficiency. Furthermore, the double-layer capacitor as a storage element is combined with the PWM inverter with voltage booster to gain the efficiency for the regenerating operation. In this system, normally, the regenerative power does not return to a battery directly but is stored in the double-layer capacitors for the next motoring action to suppress the excessive regenerative current to battery, and the regenerative power returns to the battery when the regenerative energy is larger than a certain value. The charging current to the battery is controlled to a constant value to extend the life-time of the battery. The transient and steady state characteristics of the system for 1.5kW IPM motor are investigated by both simulation and experiment. Finally, the effectiveness of the system is demonstrated by the simulated and experimental results.

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In this paper, a new approach to estimate the power system frequency using wavelet transform is proposed. The wavelet function is expressed by the power series and is able to be performed by the z-transform, which can shorten the estimating time of the signal frequency compared with the Gabor function. Simulation results, in which the fundamental frequency (60Hz) or the harmonics frequency (300Hz) of the signals are quickly estimated by the proposed method, are presented and the online estimation of the frequencies is successfully achieved by the proposed method in the experimental system using DSP.

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Power electronics is an emerging technology. New applications are added every year as well as the power handling capabilities is steadily increasing. One example is renewable energy, which is efficiently enabled by power electronics. The demands to the education of engineers in this field are also increasing. Generally, the content of the curriculum should be more expanded without extra study time. This paper presents a teaching approach, which very fast makes it possible for the students to obtain in-depth skills into new research areas, and this method is the problem-oriented and project-based learning. The necessary skills for power electronic engineers are outlined that is followed up by a description on how the problem-oriented and project-based learning are implemented. A complete curriculum in power electronics and drives at Aalborg University is presented where different power electronics related projects at different study levels are finally presented.

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In this paper, simplified equations were derived about relation between the commutation surge voltageand key factors of Current Source type Inverter (CSI). And the new commutation method is proposed. The new method is verified by calculations and real test. The new method can decrease the commutation surge voltage smaller half than conventional method.
And error between data calculated with equations derived in this paper and results of real test is smaller than 5%.

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This paper proposes a new CSMA/CD MAC protocol for air-conditioner control networks using only the UART built in a microcontroller as a collision detection mechanism. For performance evaluation of the proposed protocol, steady state throughput and average delay are calculated by analysis based on an imbedded Markov chain model. The analysis forecasts adequate throughput and delay for an example control network. The implementation of the proposed protocol to a very low-cost microcontroller that is installed in each air-conditioner consumed only about 1 kbytes of ROM and 20 bytes of RAM. The experiments on the performance confirmed the analysis results and obtained satisfactory throughput and average delay.

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This paper presents a fast transmission power control scheme using a UPFC (Unified Power Flow Controller) under the output voltage saturation. For practical use of the UPFC, the fast and stable power response and the reduced power converter capacity are desired. The authors propose the fast and stable control scheme under the output voltage saturation of the reduced capacity UPFC. The effectiveness of the proposed control algorithm of the UPFC has been verified by experiments.

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JAEA and KEK are jointly constructing a high intensity proton accelerator project J-PARC. Its main accelerator is 3GeV rapid cycling synchrotron (RCS). Two types of resonant excitation systems, parallel and cascade, are introduced to excite DC biased 25Hz AC currents through its main magnets. The parallel excitation is adopted for dipole magnets power supply system, and the cascade excitations are adopted for seven family quadrupole magnets systems. In this paper, two systems are investigated and analyzed, and it is explained why different types are adopted to each system. Authors believe that such hybrid exciting systems are most suitable for high power RCS.

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On a food heating process, a heat transmission system has been used widely. Recently, the Joule heating system has been received keen attentions as a sophisticated heating system because of non-scorching and cleanness. This system is based on a Joule heat phenomenon, that is, an electric resistance of food generates the heat, and then heats up food itself. However, control performance for the Joule heating system is not known well. In this paper, experimental results of the heating control for NaCl solution and soymilk are reported as basic verification of the Joule heating method.

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