Much attention has been paid to the “energy self-consumption system” in Germany, whose feed-in-tariff (FIT) rate has been decreased since renewable energy was introduced on a large scale. We developed the demonstration system using photovoltaics (PV), batteries, heat pumps and home energy management systems (HEMSs). The purpose of the system is the effective utilization of PV power in an apartment. We propose “the algorithm to maximize self-consumption” and “the algorithm to optimize charging and hot water generation, based on predictions of PV power and the demands of power and heat”. As a result, the system achieved improvement in the self-consumption rate in the whole year.
Wireless Power Transfer (WPT) of magnetic resonance coupling type can realize high-efficiency and high-power transmission. Recently, some studies have reported on the use of relay coils for controlling a system. Such a system shows complex resonance modes as it has many capacitors and coils. Therefore, the operating conditions depend on what a study focuses on. Additionally, almost studies have considered the system mathematically. There are few analyses that correspond to physical phenomena. In this study, we considered WPT in the resonance modes and transmission mechanisms on three coils. By using an original circuit derived from magnetic flux, two modes (Modes A and B) and energy transmission mechanisms were considered. The simulations and experiments show that the energy transmission mechanisms in the two modes are different. In mode A, the energy transmission from the power source to the load does not interfere with transmission field, whereas in mode B, it does.
In this paper, a method for dead time voltage compensation is proposed. The dead time is a period for preventing short circuits in the semiconductor power devices incorporated in inverters. Owing to this dead time, an error occurs in the output voltage of the inverter with respect to the voltage command. To suppress this error, a dead time compensation signal is generally added to the voltage command. However, the accuracy of the above-mentioned compensation control may be reduced because of the switching characteristics of the power device, transmission delay of the switching command, and so on. In the proposed method, to achieve highly accurate dead time compensation, the waveform of the compensation signal is formed based on a circuit model that assumes a virtual capacitor is connected to the semiconductor power device in parallel. In addition, an automatic adjustment method was proposed for parameters such as the capacitance of the virtual capacitor. The proposed method is validated experimentally.
This paper proposes a high power density inverter utilizing SiC metal-oxide-semiconductor field-effect transistor (MOSFET) modules and an interstitial via hole (IVH) printed circuit board (PCB) for a motor drive system. The inverter also includes a power circuit, heatsink, cooling fan, gate drive circuit, and DC capacitors. The output power density of the proposed inverter is 81kW/L. The inverter outputs 37kW for motor drive applications. To achieve this superior output power density, this paper explains a prototype SiC MOSFET module without an antiparallel schottky barrier diode, and a unique multilayer laminate IVH PCB to connect the modules and DC capacitors. This paper describes the experimental results to verify the motor drive performance and the increase in temperature under the rated load operation.
Linear resonance actuators (LRAs) have high efficiency and are small in size, and they are expected to be applied to industrial applications. The amplitude of an LRA changes with an external load therefore, the compensation for load is essential. We have proposed an amplitude control method by using a back-EMF. However, it has two problems: the low responsiveness in the transient state and the amplitude variation in the steady state. To address these problems, we proposed our method with a sensorless load estimation method based on energy conservation law. This study clarifies that the method can improve the responsiveness and amplitude variation.
This paper presents a new type of axial gap motor, called the flux-modulating hybrid field motor (FHM). For flux modulation, the FHM has rotor iron pieces sandwiched between two stators, the armature and field poles. The field poles comprise permanent magnets and electromagnets, and the magnetic flux of the electromagnets can be adjusted by changing the field current. To validate the principle of this FHM, a 0.8-kW prototype machine was fabricated, and the basic characteristics of the prototype machine were investigated through experiments and three-dimensional finite element analysis. The results show that the torque can be varied in a wider range by changing the armature current vector and field current.
This paper proposes a new torque-sensorless ripple-reduction torque control method for synchronous reluctance motors, which evolve torque ripples depending on the rotor position by the sinusoidal stator current. The proposed method, which requests the construction of a vector control system with a special command converter, has the following attractive features. (a) The average evolved torque matches its torque command. (b) The torque ripple can be considerably reduced. (c) The current command generated from the torque command is on the trajectory for efficient drives. (d) It is analytical and simple. The effectiveness of the proposed method is validated through extensive simulations.
Induction heating is required to search for load resonant frequency to control the inverter output power. However, harmonic components of a square-wave voltage output from the inverter result in poor load resonant frequency. This paper proposes a search method for obtaining the optimum load resonant frequency. The results confirmed that the sampling range was reduced by 66% and the sampling number was increased 2.9 times than those obtained using the conventional method.