Variable power sources like photovoltaics (PV) and wind turbine (WT) are largely penetrating recent years. Therefore, heat pump water heater (HPWH) for household has been focused as a controllable load (CL) for load leveling. HPWH should be operated without loss of the user's convenience while using as a CL. In this paper, HPWH model shown in the previous research has been verified by acquiring the characteristics of the actual machine. In addition, we have designed a multiple units control method for load leveling while suppressing the sharply load fluctuation, and a method to optimize the starting times to reduce the risk of hot water shortage based on the clustering result of actual hot water demand. The effects of the proposed methods have been verified using the simulation model for automatic generation control and HPWH model including thermal system.

Recent growth of renewable energy (RE) generations with natural variability, such as photovoltaic generation and wind turbine generation, would make the demand and supply control in a whole power system more difficult, and therefore, alternatives for demand and supply regulation resources would be required. The authors focus on co-generation system (CGS) as one of regulation resources. In order to procure adequate volume of regulation capability, an aggregator coordinates a number of CGSs efficiently and flexibly considering the wide variety of electricity/thermal demands of CGS owners. This paper proposes a novel optimal operation strategy of CGS coordinated by the aggregator considering the energy balance and operation cost of individual CGS owner. This paper also demonstrates the availability of CGSs for regulation capability by numerical case studies in which the actual consumption profile is employed.

The installed capacity of photovoltaic (PV) systems has been increasing rapidly due to the enforcement of the feed-in tariff scheme in Japan. However, reverse power flows from PV systems cause voltage rise in distribution networks. As one of the ways to avoid voltage rise, there is a constant power factor control by Power Conditioning Subsystem of PV (PV-PCS). In long-distance distribution networks, however, constant power factor control could cause voltage drop; in addition, rapid load changes cause voltage fluctuation problems. Static Var Compensator (SVC) can solve these problems, but it is high cost. Therefore, it is more economical to use PV-PCS than to install SVC. In this paper, we propose variable power factor control and reactive power compensation using available capacity of PV-PCS. While the variable power factor control maximizes PV power generation for PV owners, the available capacity of PV-PCS supplies reactive power to suppress voltage fluctuations, which is equivalent to SVC for electric utilities. The result shows that the variable power factor control can increases PV power generation more than constant power factor control. We clarified a range of available capacity of PV-PCS to supply reactive power that generates a Win-Win situation for PV owners and electric utilities.

Although various studies investigated on photovoltaic (PV) energy curtailment in a bulk power system in recent years, they rarely considered transmission network constraints or cross-regional power exchange. In this study, we develop an economic-load dispatching (EDC) control method by optimal power flow (OPF) with PV energy curtailment considering transmission network constraints. Firstly, we propose a PV energy curtailment method considering transmission network constraints. Secondly, we propose an EDC method considering cross-regional power exchange in the interconnected power systems. The effectiveness of the proposed methods is evaluated by simulations conducted on IEEJ EAST 30-machine system model representing interconnected bulk power systems.

The optimal Phasor Measurement Unit (PMU) placement problem in power systems has been considered and investigated by many researchers for accurate and fast state estimation by PMU. There is a problem that the current channel cost of the PMU affects the total placement cost. This paper proposes novel formulation in multi objective optimal PMU placement which minimizes the PMU placement cost with the current channel selection and the state estimation error. The current channel selection is represented as a decision variable in the optimization. For those trade-off objective functions, the Pareto approach by Non-dominated Sorting Genetic Algorithm II (NSGA-II) is applied in the optimization. The result of the numerical experiment in this paper demonstrates the advantage of considering the appropriate PMU current channel allocation, compared to the conventional method which ignores it, in the modified IEEE New England 39-bus test system. As a result, the proposed method obtained a better Pareto solution compared to the conventional one because of consideration for the current channel selection. The proposed PMU placement shows its advantage that it is able to reduce the total PMU placement cost while it keeps the state estimation accuracy.

In this paper, an efficient method is proposed for Voltage and Reactive Power Control (VQC) with Predator-Prey Brain Storm Optimization (PPBSO). VQC plays an important role to main voltage profiles within the appropriate bounds. In recent years, the use of renewable energy such as PV systems and wind power generation, Demand Response (DR), energy storage systems (ESS), etc. has been spread in power systems. As power system operation becomes more complicated, more advanced VQC schemes are required to deal with such power systems. This paper proposes a new VQC method for improving the solution quality and speeding up computation time. Specifically, a couple of techniques are employed to handle advanced VQC. One is to use PPBSO of high performance evolutionary computation and evaluate better solutions while the other is to employ hierarchical optimization, apply parallel computation of OpenMP to the subsystems and speed up computational time. The effectiveness of the proposed method is demonstrated in the IEEE sample system.

Simulator for distribution network with smart inverter controlled by frequency-watt function has been developed. Since the frequency-watt function which is one of the grid support functions of smart inverter adjusts the output of active power owing to the frequency fluctuation in the power grid, a power flow calculation which can represent the frequency fluctuation based on the power imbalance has been implemented in the developed simulator. The frequency-watt function of the smart inverter has been assessed with the developed simulator. It was found that the smart inverter controls the active power depending on the frequency.

In future power systems with extremely large integration of photovoltaic (PV) generation, it is necessary to not only properly maintain supply-demand balance without power shortfall but also utilize as much PV energy as possible. The application of PV power forecast and energy storage devices to power system operation is necessary. In this study, we propose a method for determining and modifying the charging and discharging schedule of battery energy storage system (BESS) and the unit commitment (UC) of thermal generators based on the PV power forecast. The proposed method is evaluated by numerical simulations for one year. The results show that both the energy shortfall and PV curtailment can be reduced by the proposed method.

By theoretical study of P-V curve and P-Q curve drawn from circuit equations for 2-node simple distribution system model, we have examined the influence of var loss with voltage reduction in distribution line which large capacity of photovoltaic system is installed. It was found that the var loss increases when the voltage reduction occurs due to large reverse power flow. The measured values coincide with the obtained P-V and P-Q curves. The influence of var loss on the voltage profile of distribution line has been also discussed.

In recent years, the introduction of renewable energy such as solar power generation has been advanced. However, if a large amount of distributed power source is introduced, the voltage at the interconnection point will rise due to the backward flow, and voltage deviation from the specified range will occur. The authors proposed autonomous operation control by each customer and proposed Cell Grid for suboptimization of voltage optimization. This is a power system with each consumer load as a minimum unit. In this paper, we introduce the concept of machine learning into each Cell Grid and autonomously resolve voltage deviation in each Cell Grid.

To evaluate the degree of degradation of the transformer, average degree of polymerization (DP) of the insulating paper on winding is measured in general. This measuring process accompanies insulation risk because several tens centimeter of the insulating paper has to be cut off from the winding in transformer. In this paper, a new method is proposed to estimate the average DP of the insulating paper by measuring the refractive index of cellulose fibers on the paper. The relationship between wavelength characteristics of dispersion color on cellulose fibers and DP of the paper was revealed using Mahalanobis-Taguchi method. Only hundreds of cellulose fibers that come off from paper surface or paper edge are used in this method, it becomes possible to know DP without cutting of the insulating paper.

Partial discharge inception characteristics of an oil impregnated paper insulating system with inserted oil impregnated insulating papers of a removed oil filled cable were investigated. It was found that the partial discharge inception stress of the insulating system with inserted removed insulating papers without deposit was almost the same as that of the insulating system with inserted fresh insulating papers. On the other hand, the partial discharge inception stress of the insulating system with inserted removed insulating papers with deposit was lower than that with inserted fresh insulating papers.

The recovery voltages between contacts of circuit-breaker during capacitive current interruption on overhead transmission lines with high resistance neutral system were investigated. Conditions were clarified which are to be equivalent on recovery voltage level between high resistance neutral system and effectively earthed neutral system using single line and double line systems. The conditions are tentatively indicated as less than 100km of line length and less than 1 kilo ohms of neutral resistance.

In this paper, we focus on the relationship between wind turbine separation distance, wind speed and power output, and this paper aims to evaluate the wind speed ratio and the power output ratio due to wake. We selected three wind turbines influenced by wake from the already operating wind farm, and calculated the wind speed ratio and the power output ratio which were influenced by the wake of the front wind turbine. As a result of comparing these ratios for each wind turbine, as the separation distance becomes larger, the influence of wake by the front wind turbine becomes smaller and the wind speed and the power output were recovered. Furthermore, we compared the wind speed ratio calculated from the general wake model and the ratio calculated from the observed data. As a result, it became clear that the result of the wake model is different from the observed data.

The 29th Power and Energy Society Annual Conference was held on September 12-14, 2018 at Josanjima Campus of Tokushima University in Tokushima, Japan. The total number of presented technical papers was 409 and that of technical sessions was 52 (51 oral sessions and one poster session). A panel discussion and a special lecture were also organized during the conference period. The seats of the most events held during the period were fully occupied with audiences, and the final enrollment attained to 1,001. The conference was successfully completed with the great contribution from all the participants. This report reports the outline of the conference.