To design the vector control system of the induction motor, the γ . δ coordinate is used to obtain the high performance decoupling current control system. But the motor model using the γ . δ coordinate is different from the physical image of the motor, because the frequency ω1 of the power source is necessary for this model, and also this model is not three phase. To overcome above mentioned problems, a new three phase model of the induction motor based on a new state equation in which the frequency ω1 is not necessary will be presented. A new vector control system based on the three phase coordinate will also be proposed. The simulation results of the V/f control and the above vector control system using the proposed three phase model will be presented.

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Current-fed inverters for off-grid power systems have several advantages, such as no lower-limit of the dc-voltage range, and no electrolytic capacitors. However, the inverter with ordinal PWM (Pulse-Width-Modulation) scheme produces undesirable lower order harmonics in the ac-output voltage and the dc-input current under an inductor with limited inductance. Thus, the PWM scheme requires smoothed dc-inductor currents and so, a bulky and expensive inductor on the dc-side is necessary. To overcome the problem, the authors propose a three-phase current-fed inverter for off-grid power systems with a predictive-instantaneous-voltage-control and PSM (Pulse-Space-Modulation). In this paper, the principle and theoretical operation of the proposed inverter are described in detail and the theory is confirmed through simulation studies.

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This paper shows various rotor structures of interior permanent magnet synchronous moter (IPMSM) with Dy-reduced rare earth magnet. Dysprosium (Dy) is added to permanent magnet to increase the magnetic coercive force. However, Dy is so rare and expensive. A conventional model using Dy-reduced rare earth magnet cause ploblems with demagnetization. In these reasons, the rotor structures of IPMSM with Dy-reduced rare earth magnet for improvement of irreversible demagnetization without torque reduction are proposed. The presented IPMSM structures are analyzed by using finite element analysis (FEA). Finally, the proposed model which improved the demagnetization and torque characteristics was able to get approximately the same characteristics of conventional model using Dy-much rare earth magnet.

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EV category of the Student Formula Japan Competition will be an official event in 2013. In order to optimize the regulations of the category, we have developed an EV based on a vehicle driven by an engine for the student formula. At first, our prototype motor was applied to its traction motor and the test run was performed, and we developed an Interior Permanent Magnet Synchronous Motor (IPMSM) suitable for the formula by analyzing the test data. Furthermore, we developed a motor which achieved higher power density and correspondence to the regulation. This paper introduces the developed IPMSM.

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The miniaturization and weight saving of the boost converter for motor driving system of EV are very important issues for higher performance. This paper proposes the multi-phase boost chopper circuit for EV using coupled inductors which can achieve downsizing of inductors and the output smoothing capacitor. Coupled inductors enable to integrate magnetic components into one assembly. Therefore, the miniaturization and the lower cost of the magnetic component for the inductor are achieved. However, characteristics and design methods about integrated coupled inductors for proposed circuit have not been analyzed yet. This paper analyzes characteristic about the proposed circuit and flux in the core of proposed integrated coupled inductors. Moreover, the design procedure of proposed coupled inductors for the case of using the conventional three-leg core is presented. From experimental results, propriety of the design and effectiveness of the proposed circuit are confirmed.

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The characteristics of photovoltaic power generation system is nonlinear. In addition, photovoltaic characteristics becomes more complex due to partial shading condition. This paper examine the impact on the characteristic in a partial shading condition, and proposes an improved maximum power point tracking control using the optimum method of a particle swarm optimization algorithm. The main advantage of this revised method has the ability to keep tracking the maximum power point even in extreme cases, e.g., in a partial shading condition.

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The single-phase PFC converters are used for a lot of applications, such as air conditioners, heat pumps, etc. Its application range is expected to expand such as battery charger for EVs, PHEVs and home strages. However, the single-phase PFC converter has output voltage ripple caused by supply power ripple. It is a one of demerit of single-phase PFC converters. Then the authors proposed a ripple reducing control method which can apply to buck, buck-boost and series-type buck/boost converters. The converters are required to more improve conversion efficiency, cost and size. However, as far as the authors know, there has been no example of comparing the switching losses in these converters. Therefore, in this paper, the authors describe a comparison of the switching losses in three type converters with a simple analysis and computer simulation.

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Multiple winding motor and transformer is used with multiple inverters. The interference by magnetic coupling between the windings affects controller. Response of controller may be worse by the interference. In this paper, modeling of multi winding motor and transformer including magnetic coupling and decoupling control method is proposed.

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Wind energy is a clean and renewable energy source. A wind generator using a PMSG can operate in maximum power point tracking (MPPT) mode. In addition, it has capabilities for fault ride through (FRT), active power and reactive power control issues, and voltage regulations. We have already proposed a model following controlled PWM inverter that exhibits robustness. The proposed inverter can output a sine wave current regardless of the rippling input voltage. This paper presents a numerical simulation analysis of the transient characteristics of the discrete-time model following controlled PWM inverter for a wind turbine generator system with a synchronized grid interface.

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This paper proposes an efficient PWM modulation method in a three-phase PWM inverter which optimally reduces switching (SW) losses for one switch cycle according to the two-phase modulation. It selects the optimum switching vector (SV) pattern on-line which minimizes an estimation function based on switching losses considering phase currents among possible reduction patterns for one switching cycle. The estimation is composed of two types of SW losses. The first one is a PWM SW loss due to the two-phase modulation composed of three SVs for one switch cycle. The second one is a transition loss between one of six switch modes from I to VI to another. The proposed SW loss estimation is defined as ol-line subtraction of the first loss saving from the second loss locally for one switching cycle. The optimum switch pattern (SP) is defined as one with the lowest estimation and it can reduce SW losses most effectively. The proposed optimum PWM principle was experimentally investigated for output voltages of the two-level and three-level inverters connected with an universal load. It reduced number of switching times of the largest or secondly largest current. It can automatically adapt to various conditions of current amplitudes which are dependent on power factors of loads.

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A high-efficiency and high-performance bidirectional DC-DC converter is one of the key elements for interfacing the DC bus line and a battery in a DC micro grid system. A new prototype of primary-/secondary-side phase shifted zero voltage soft-switching (ZVS) pulse width modulation (PWM) dual resonant (series resonant and edge resonant) bidirectional DC-DC converter is proposed in this paper. The power regulation principle based on the primary-side phase shift (PPS) and secondary-side phase shift (SPS) is described by means of the simplified equivalent circuits of the proposed DC-DC converter. The essential performances of the bidirectional DC-DC converter are demonstrated in an experiment, then its validity is discussed from a practical point of view.

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This paper shows new induction generation system for wind power generation. This system has the voltage source converter (VSC) exciting induction generator (IG) and the power factor correction (PFC) converter to absorb the real power in parallel. Rating of the VSC is minimized since it supplies reactive power only and the PFC converter absorbs all the real power. The cost of IG is much lower than synchronous generator with permanent magnets (PMSG) and is possible to have the maximum power point tracking (MPPT) control by using VSC for exci tation. We also propose to minimize the loss in IG to increase the efficiency or the reactive power consumption of IG to decrease the rating of the VSC. The effectiveness of the proposed control for the wind power generation system was verified by simulation and experiments.

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A new control system of the bidirectional isolated dc/dc converter which can obtain the output voltage much higher than the turn ratio of the transformer, will be presented. The output terminals of two single phase bridge inverter A and B are connected through an isolated transformer, and the pulse width of the inverter of higher d.c. voltage is narrowed to make equal the fundamental a.c. voltage of both inverters. After doing so, to control the power flow, the phase angle between both inverters is controlled. To make explanation simple, the transformer turn ratio is supposed to be 1:1. The d.c. voltage of the INV-A is 100[V], and the d.c. voltage of the INV-B is 200[V]. In this case, to make the a.c. output voltage of both inverters same, the pulse width of the INV-A is 180 degree and the pulse width of INV-B is narrowed to 60 degree. By doing so, the power flow from the d.c. 100[V] source to the d.c.200[V] source can be realized.

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Currents of transformer consist of load current and magnetizing current. It is believed that magnetizing current flows only in primary winding and is not provided to load. It is correct for ordinary transformers but not for transformers of DC/DC converters. In this paper, many examples in which magnetizing currents flow in secondary winding and provided to load are described.

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