This article surveys applications of advanced techniques of electromagnetic field analysis. Key topics are as follows: material modeling, model-order reduction, optimal design, high-performance computing and electromagnetic force. The first three topics and a stray loss analysis of transformer are mainly presented in this article.

In recent years, renewable energy such as solar power generation has become widespread in the world. The spread of distributed energy resources (DER) is also accelerating to realize multi-purpose values for power grid and DER owners. Each DER has specific function and potential, that will be maximized with coordinate optimization, operating and control by Home Energy Management System (HEMS). In this study, we focused on battery energy storage system (BESS), heat pump hot water server (HP) and fuel cell (FC) as typical controllable DERs. Then we developed a simulation model that enables to manage energy of hundreds of smart houses with DERs and HEMS. With this simulation, simultaneous realization of multi-purpose values with the supposed combination of DERs (BESS+HP+FC) was quantitively confirmed. Next, optimal DER allocation planning methods are proposed, that consider avoiding overinvestment with restricted one DER for each house. Type I DER allocation is top-down method, type II is bottom-up method, and type III is the method extended type II where all combinations of DERs were evaluated. With comparative evaluation of these methods, we visualized the potential of several index and their relationship. These studies will be effective to plan the DER spreading strategy in target area.

This paper presents a probabilistic reliability evaluation technique of bulk power transmission networks considering power system emergency operation models with a variety of dispatchable energy resources such as pumped-hydro generations, battery energy storage systems (BESS), and demand response (DR). Analytical models in emergency situations of dispatchable energy resources subject to Wh constraints (i.e. reservoir capacity and State-of-Charge) are defined and formulated in optimal power flow calculation process. Through numerical simulations on the tested bulk power system model (modified IEEE RTS model), the beneficial impact of coordinated system emergency operations with the dispatchable energy resources has been quantified and evaluated from the aspects of supply reliability and operational cost.

The paper examines the voltage fluctuations of a single-machine infinite-bus system in case of massive integration of current-control type inverters paying particular attention to the short circuit ratio of the inverters.

The increase of inverter-interfaced power sources, such as wind and photovoltaic power generation, arouses concerns on the voltage fluctuations in a power system because the increase causes the decrease of the short circuit capacity of a power system. In a power system with low short circuit capacity, an inverter could face challenges in power quality of the power system and the control stability of the inverter.

By normalizing active and reactive power with short circuit capacity, the paper exhibits general relationship between the active and reactive power of an inverter, to keep the terminal voltage of an inverter to a designated value, for various resistance-to-reactance-ratios of looking-back impedance of a power system. It also examines the sensitivity of the active and reactive power of an inverter to its terminal voltage.

In Japan, the introduction of photovoltaic systems, one of a renewable energy sources, has been encouraged by the government. A new energy supply system for tram power lines which can directly collect and use PV outputs is proposed as a method for PV utilization without relying on feed-in tariff. In the system, PVs are installed at public schools located along tram lines, and DC/DC interfacing converters are installed near tram stops. In this paper, a detailed algorithm and a brief algorithm are proposed to optimize the allocation of interfacing converters for the maximum economic benefits while considering fluctuations of PV output and tram load. The PV-converter systems and tram power systems were modeled as electric circuits in both algorithms. The brief algorithm can find the optimal allocation 0.487% of the time compared to the detailed algorithm while maintaining practical accuracy.

This paper proposes a dynamic state estimation method for distribution systems using measurement values from IT switches and smart meters. In future distribution systems, introduction of solar power generations and electric vehicles is expected to increase complexity of directions and changes in the power flow. The proposed method is able to observe power flow directions in the distribution systems better than conventional state estimation methods without using smart meters. Furthermore, in order to observe complicated changes in the power flow, measurement values from smart meters with long measurement periods and delays are weighted to adjust their influence on the state estimation results for better performance in tracking power flow changes. The proposed method is verified to be more accurate for the voltage estimation than conventional methods through simulations assuming complicated distribution systems.

AI control for building multi-type air conditioners which adapt to dynamic pricing type FastADR has begun to be considered. In order to adjust supply and demand balance, the grid management system needs to know how AI-controlled air-conditioners respond to unit price fluctuations. In this paper, we clarify the power response distribution of AI-controlled air-conditioners to unit price fluctuations at 30 minute intervals. Large-scale experiments on real buildings are difficult to conduct, and reproducibility cannot be ensured. Therefore, we used an emulator that can simulate the diverse and uncertain minute-by-minute power consumption of building multi-type air-conditioners, and quantify the expected power reduction and uncertainty range based on the power response distribution of 100 diverse virtual buildings.

Electric power generated by photovoltaic (PV) systems is generally unstable because of uncertain meteorological conditions. Stably maintaining the supply-demand balance of power systems requires an accurate prediction of the performance of PV systems. Especially for predicting the performance of the PV systems containing modules with different electrical characteristics or installed in different angles, it is necessary to calculate the generated power of the system by combining the current-voltage (I-V) characteristics of each module in series and parallel. Therefore, an accurate method is required for estimating the I-V characteristics in various meteorological conditions. In this paper, a simple modelling method of the I-V characteristics for crystalline silicon PV modules is proposed. The I-V characteristics can be simulated in a good accuracy for practical use based on a simplified equivalent circuit of PV modules and a temperature correction of the short-circuit current, open-circuit voltage, and the current and voltage at maximum power point. The validity of the proposed method is examined by comparing simulated and measured I-V characteristics of a PV module. Furthermore, to demonstrate the effectiveness of the proposed modelling method, it was applied to simulating the power generation of a PV system containing modules installed in different angles.