This paper proposes variable tip speed ratio control in a stand-alone small-scale wind power generation systems.The proposed variable tip speed ratio control changes the reference tip speed ratio when the generated power exceeds load power.The vertical axis wind turbine generates required torque of the load by using the proposed variable tip speed ratio control.Digital computer simulation is implemented to confirm the validity of the proposed method using PLECS (Piece-wise Linear Electrical Circuit Simulation) software. Simulation results demonstrate that the surplus power can reduce by the proposed variable tip speed ratio control.
To prepare for potential power outages, an increasing number of homes have been equipped with emergency power supplies. Although a grid-disconnected inverter with a battery is promising as an emergency power supply, in order to use home appliances continuously in the same manner as in normal times, the inverter needs to build a single-phase three-wire system as well as the commercial grid. To solve this problem, we propose the theory of virtual synchronous generator (VSG). This control method is developed expanding the previous method for a single-phase two-wired system to a single-phase three-wire system.Because the VSG can supply unbalanced power as same as the commercial grid, there is no need to reconnect home appliances to dedicated outlets, and it is possible to realize uninterruptible power supply to home appliances for daily use at the sudden power failure.
For the research and/or development of motors and their control methods, it’s necessary to obtain torque and voltage equations of the motors from their structure. This paper presents the derivation method of torque and voltage equations of IPMSM (Interior Permanent Magnet Synchronous Motor) and FMSM (Flux Modulating Synchronous Motor) from their basic structure. Fleming’s law is applied to derive torque equation.
Lithium ion batteries are incredibly popular these days. Lithium ion batteries have extremely high energy density, so if charge and discharge are not performed with precise control, battery life is shortened. In extreme cases it bursts or ignites.Therefore, accurate charge control is necessary. The lithium ion battery targeted in this research has 84 cells with a nominal voltage of 4.2 volts, fourteen of cells are connected in series, and six of them are connected in parallel. In addition, it has CAN communication function and can send the state of the battery to the outside. At present there is a charger for that one battery, but there is no charger that charges multiple batteries at the same time. In this research, we aim to develop a battery charger that can charge multiple batteries simultaneously by using data obtained from CAN bus.
In recent years, the development and application of GaN-HFET has become actively, which is one type of a wide band gap semiconductor. The GaN-HFETs has specialize high frequency operation, it is possible to improve the performance of the power converter by improving the switching frequency. In this paper, we describe a basic investigation in the case of GaN-HFETs applied Class-Φ2 inverter circuit, which is a resonant power conversion circuit and operated as an isolated DC-DC converter with a switching frequency at 13.56 MHz.
In the power electronics field, the movement that the EMI noise standard is revised is being carried out by IEC. This revision also affects electronic equipments using switching power supplies, and there is a possibility that they can not respond to conventional electronic equipments. In the frequency range of the new standard (below150 kHz), it is essential to take measures against noise from the fundamental wave with the highest noise level. In this paper, we will investigate measures to apply frequency spreading to the frequency range and measurement condition of the new standard, and to minimize the size and increase in cost of electronic equipment.
Modular multilevel converters (MMC) have been studied as an ac-dc converter applied to high voltage dc power transmission (HVDC). In order for MMC to maintain the dc bus voltage, it is necessary to balance the dc capacitor voltage of each cell. This paper presents “phase arm balance control” and “upper and lower arm balance control” using negative sequence components of ac grid current and circulating current. The proposed method is verified by numerical simulation.
LLC resonant converter which have features as high power density, high efficiency and low noise is widely used for consumer and industrial applications. Recently, LLC resonant converter with center tapped transformer is applied to industrial application such as FA (Factory Automation), because wide-input voltage range and high power density is required in this application. Accordingly, a problem of unbalanced secondary current for each half cycle becomes apparent. In this paper, the influence of coupling coefficient of center tapped transformer between primary and secondary to the unbalanced secondary current is investigated. As a result, an offset of magnetizing current by difference of the coupling coefficient occurs then the unbalanced secondary current are generated to cancel the offset.
This paper describes a history of power system simulators used for the development and manufacturing power electro equipment, e.g. high voltage DC power transmission systems(HVDC), Flexible AC Transmission System(FACTS) in power system. Due to advances in technology, Power system simulators have also evolved from analog to fully digital.
Thermoelectric modules can convert heat energy to electrical power directly. Thermoelectric power generation has the advantages of being maintenance free, silent in operation and involving no moving or complex parts. Many work has been reported on the thermoelectric power generator. In this paper, we proposed the new maximum power point tracking (MPPT) control which is applied to thermoelectric generator. The proposed method utilize ripples of current and voltage respectively, generated by switching. The effect of the proposed method can be confirmed in the equivalent circuit. Then, the characteristics of the thermoelectric power generation pot applying proposed method are verified experimentally.
The implementation of a magnetic bearing within a high-speed, high-capacity SPM motor (450kW, 17,000rpm) and the subsequent elimination of the step up gear from the centrifugal compressor have achieved increased efficiency, size reduction, and oil-free design of large HVAC chillers. This report examines the characteristics of magnetic bearings and describes the higher radial suspension force technology that allows for a shorter bearing length, key to achieving higher speeds and compressor size reduction. The report also introduces features of the large centrifugal chiller units containing the newly developed magnetic bearing in the US and China markets.
Micro-wind turbines (MWTs) should have wide range of wind speed. A MWT system can start quickly, but it may be difficult to stop it in low wind speeds. This paper proposes a converter system for variable-inertia and damping-control of MWT. The MWT controlled by the proposed method can be operating even if wind speed decreases momentarily.
Nowadays, interior permanent magnet synchronous motors (IPMSMs), generally driven by PWM inverters, are mainly utilized as the traction motors of eco-friendly vehicles. As a result of the carrier harmonics of the input current by PWM inverters, harmonic losses of IPMSMs become higher than those of IPMSMs with ideal current input. This paper discusses the characteristics of the proposed double-layered IPMSM and the conventional single-layered IPMSM with current inputs where the PWM carrier frequencies were set to 5, 10, and 20 kHz, respectively, which reveals the influence of various carrier frequencies on the performance of IPMSMs.
DC power supply systems are attracting attention. If a power line communication is introduced into a dc system, the power supply and the communication can be concentrated on the power line. In this reseach, a power line communication method is applied which provides zero voltage section periodically and applies negative or zero voltage is applied during the section to send a bit signal. In this method, when the dc voltage is increased, surge voltage across switching devices due to the line inductance becomes a problem. To solve this, we propose that a diode in the conventional circuit is substituted into a MOSFET. Experimental results show the surge voltage is sufficiently reduced with the proposed circuit.