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The introduction of a large number of photovoltaic systems to distribution systems has increased the complexity of the voltage profile. It is thus necessary to manage voltage at a higher system level. For this purpose, the voltage profile of the distribution system can be calculated using state estimation and the voltage can be controlled based on the estimated values. Many methods for estimating voltage profiles using state estimation have been developed. However, the estimation accuracy of voltage profiles required for proper voltage control has not been discussed. If the assumed required estimation accuracy is too high, then more meters than necessary will be installed, unnecessarily increasing costs. Conversely, if the assumed required estimation accuracy is too low, voltage control equipment will not operate properly, and voltage violations may occur. Thus, it is important to determine the required estimation accuracy of voltage profiles for proper voltage control. In this paper, the estimation error of the voltage profile is expressed using a probability density function, and the estimation accuracy of voltage profiles required for proper voltage control is examined. A numerical case study was performed on a distribution network model with 2160 consumers, and revealed the following. To prevent voltage violations, an estimation accuracy of voltage profile that is approximately 10 times lower than that of the estimation accuracy based on current measurement equipment data is sufficient. To minimize the number of tap operations, an estimation accuracy needs to be improved by 70% compared with the estimation accuracy based on current measurement equipment data. [ABSTRACT FROM AUTHOR]

With many distribution networks adopting photovoltaic (PV) generation systems in their networks, there is a significant risk of over-voltages, reverse power flow, line congestion, and increased harmonics. Therefore, there is a need to estimate the amount of PV that can be injected into the distribution network without pushing the network towards these threats. The largest amount of PV a distribution system can accommodate is the PV hosting capacity (PVHC). The paper proposes an efficient method for estimating the PVHC of distribution networks that combines particle swarm optimization (PSO) and the gradient descent algorithm (GD). PSO has a powerful exploration of the solution space but poor exploitation of the local search. On the other hand, GD has great exploitation of local search to obtain local optima but needs better global search capabilities. The proposed method aims to harness the advantages of both PSO and GD while alleviating the ills of each. The numerical case studies show that the proposed method is more efficient, stable, and superior to the other meta-heuristic approaches. [ABSTRACT FROM AUTHOR]

Abstract: A cationic spiropyran iodide derivative (SPI) was synthesized as a photoresponsive compound, and SPI/montmorillonite clay hybrid films were prepared using ion- and guest-exchange intercalation methods. When the ion-exchange method was applied to clay with a low cation-exchange capacity (CEC), intercalation of SPI into clay interlayers did not occur. Using the clay with a high CEC, SPI was intercalated into clay interlayer and the interlayer distances were elongated. Upon UV and visible light irradiation, SPI in hybrid film photoisomerized reversibly and the interlayer distance also changed reversibly. On the other hand, intercalation by the guest-exchange method using cethyltrimethylammoniumbromide (CTAB) as a pre-exchanging reagent was independent on the CEC. After the addition of SPI, the CTAB in the clay interlayers was exchanged for SPI, but a partial CTAB remained in the interlayer. SPI in the hybrid films prepared by the guest-exchange method photoisomerized reversibly without any change in interplanar distance due to the coexisted CTAB. [Copyright &y& Elsevier]

The authors have proposed the Flexible, Reliable and Intelligent ENergy Delivery System (called “FRIENDS”), which is a new concept for future power distribution systems. Also, a “micro grid” which is a similar concept to FRIENDS has been developed. In a micro grid, an independent distribution system can be constituted by a number of distributed generators. In this paper, FRIENDS, Micro grid, and conventional distribution systems are compared quantitatively in supply reliability and system cost through time sequential Monte Carlo simulations. In addition, for cost evaluation, interruption costs are included to show risk incurred by unsupplied energy. Finally, the authors search for preferable form with install and operation of distributed generators and network composition according to social cost including interruption cost and system cost. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 167(2): 28–37, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20659 [ABSTRACT FROM AUTHOR]

In this paper, we assume 2 models for securing reserve capacity. One is “Commitment-based Security Model” and the other is “Reserve Market-based Security Model.” In Commitment-based security model, ISO commits procurement of reserve energy to a particular generation company. Meanwhile, in Reserve market-based security model, ISO procures reserve energy through reserve market. The main object of this research is to investigate which model will be preferable for the viewpoint of consumer's cost. To compare these models, two things are considered in this paper. One is bidding behavior of agents which bids to energy market and reserve market. To consider this, Q-Learning of multi-agent model is used. Also, the Unit Commitment (UC) is considered to calculate generation cost. This is to calculate the cost for securing reserve power more precisely. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 167(1): 18– 25, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20705 [ABSTRACT FROM AUTHOR]

Recently, the basic framework of electric power systems has been changed significantly by deregulation of electric power industry. Also, distributed generators (DGs) such as renewable energy generations, co-generations, and energy storage systems have been introduced into the demand sides not only for saving energy and the global environment, but also for compensating voltage drops and supply interruption. In the future power systems, a lot of small-sized DGs will supply the electricity with existing large-scale generators under a competitive environment. In this context, it is desirable that DGs contribute to stable, reliable and economic operations by coordinating with existing large-scale generators. For example, power from large-scale generators could be leveled if DGs are operated during the peak period. Also, ancillary services such as frequency control, voltage control, and supply of reserve capacity could be executed by controlling DGs directly or indirectly. Under these circumstances, the authors have proposed a new power distribution system: Flexible, Reliable and Intelligent ENergy Delivery System (FRIENDS). This paper investigates some kinds of power supply systems which coordinate DGs with existing large-scale generators including the concept of FRIENDS and considering how DGs are managed. The effects of DGs which contribute to supply the energy and/or the reserve in every power system are evaluated. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 163(1): 48–56, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20358 [ABSTRACT FROM AUTHOR]

As deregulation in the electric power industry has advanced in many countries, a spot market and a futures market for electric energy have already been formulated. In Japan, the foundation of a day-ahead spot market is scheduled for the 2005 fiscal year. This paper presents a method to evaluate the expected profit and risk for an electric power supplier considering both spot market and bilateral market. In this paper, the Vasicek model is used to represent the fluctuations in spot price and demand in a bilateral market, and additionally, Value at Risk (VaR) is used as a risk index. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 161(4): 1–11, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20515 [ABSTRACT FROM AUTHOR]

Recently, consumers have shown concern about the reliability of electricity to be served. For example, some consumers need electricity with a higher reliability via automation of manufacturing processes. On the other hand, some consumers need electricity at a cheaper price even if the reliability becomes a little worse. Under such circumstances, it is necessary that power suppliers evaluate the needs of every consumer precisely and propose the most desirable measures for meeting their requirements. This paper develops a tool to analyze the reliability for high-voltage supplied consumers quantitatively. Further, this paper presents a method for evaluating the outage cost of consumers to help them choose the most appropriate measures for maintaining reliability. The proposed method applies the fuzzy reasoning approach. The validity of the proposed method is ascertained through some numerical simulations. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 153(3): 41–51, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20137 [ABSTRACT FROM AUTHOR]

The authors have proposed a Flexible, Reliable and Intelligent ENergy Delivery System (called “FRIENDS”), which is a new concept for a future power distribution system. One of the most important feature of FRIENDS is to be able to manage the reliability of power supply. In this paper, FRIENDS and a conventional distribution system are compared quantitatively as to supply reliability and cost through time sequential Monte Carlo simulation. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 151(4): 25–35, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20053 [ABSTRACT FROM AUTHOR]

Abstract: In this paper, a new bidding strategy for a day-ahead market is formulated. The proposed algorithm is developed from the viewpoint of a generation company wishing to maximize a profit as a participant in the deregulated power and reserve markets. Separate power and reserve markets are considered, both are operated by clearing price auction system. The optimal bidding parameters for both markets are determined by solving an optimization problem that takes unit commitment constraints such as generating limits and unit minimum up/down time constraints into account. This is a non-convex and non-differentiable which is difficult to solve by traditional optimization techniques. In this paper, evolutionary programming is used to solve the problem. The algorithm is applied to both single-sided and double-sided auctions, numerical simulations are carried out to demonstrate the performance of the proposed scheme compared with those obtained from a sequential quadratic programming. [Copyright &y& Elsevier]

In this paper, the authors propose a fuzzy-optimization approach to dynamic economic dispatch, considering the uncertainties in deregulated energy and reserve markets. The methodology was developed from the viewpoint of a generation company wishing to maximize its own profit and to hedge its risks as a participant In the energy market and 10-min spinning reserve market. The uncertainties in the current paper were represented with fuzzy numbers, and consist of the demand and reserves required In each market, prices cleared in each market, and the probability that reserves are called upon in actual operation. The energy and reserve markets were coordinated by the generator ramp rate limits. The optimal amounts of power. and reserve were determined by solving the optimization problem. Two reserve payment methods, payment for power delivered and payment for reserve allocated, were Investigated in this paper. [ABSTRACT FROM AUTHOR]

The authors have proposed FRIENDS—Flexible, Reliable and Intelligent Electrical eNergy Delivery System—as a future electric power distribution system. The most important idea of FRIENDS is to install new facilities called Quality Control Centers (QCCs) between the distribution substation and customers. By controlling QCCs appropriately, various purposes of FRIENDS can be achieved. It is indispensable to design the concrete interior structure of QCC in order to realize FRIENDS. This paper proposes the interior structure and control methods of QCC from the viewpoint of power conditioning functions by energy storage system in QCC. In this paper, it is assumed that SMES is used as the energy storage system in QCC. The proposed interior structure is based on the concept of UPS (Uninterruptable Power Supply). In this paper, SMES is installed in the DC side of UPS. Further, this paper proposes control methods of SMES and PWM converters. The proposed control methods are used to satisfy various purposes, such as load fluctuation compensation, load leveling, and cooperation with dispersed-type generator. Finally, the validity of these control methods is confirmed through transient analysis PSCAD/EMTDC. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 143(3): 20–28, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10056 [ABSTRACT FROM AUTHOR]

Presents a new unit commitment (UC) method between Lagrange Relaxation and evolutionary programming for the power industry, as of February 2003. Functions of the new method; Importance of the method to generating companies; Formulation of the new UC problem.

The authors have proposed FRIENDS as a concept of the future electric power system. In order to realize FRIENDS, it is necessary to design the concrete interior structure and control scheme of the Quality Control Center (QCC) which is to be installed between distribution substation and customers. Hybrid-type transfer switches are assumed to be installed on the high-voltage side of the QCC to realize network reconfiguration. Some devices for handling power quality are also assumed to be installed on the low-voltage side to realize customized power quality. In this paper, a novel control scheme for shutoff of the thyristor switches by the power quality handling devices is proposed and the effectiveness of the proposed scheme is investigated through momentary analysis using PSCAD/EMTDC. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 142(1): 32–41, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10077 [ABSTRACT FROM AUTHOR]

The authors have proposed the Flexible Reliable and Intelligent Electric eNergy Delivery System (FRIENDS) as a future electric power distribution system. In order to realize FRIENDS it is indispensable to design the concrete interior structure of the key facility, the Quality Control Center. This paper proposes an interior structure and control schemes for the Quality Control Center from the viewpoint of customized power quality service, which is one of the most important objectives of FRIENDS. The validity of the proposed structure and control schemes is confirmed through transient analysis using PSCAD/EMTDC. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 139(3): 45–52, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.1159 [ABSTRACT FROM AUTHOR]

Presents a study that examined the application of evolutionary programming with sequential quadratic programming for solving dynamic economic dispatch (DED) in power generation operation and control. Background on DED; Problem formulation; Results and discussion.

Recently, utilities have been able to purchase the electric energy supplied from independent power producers (IPP) owing to deregulation in the electric industry. This paper evaluates the influence of IPP uncertainty on the utility and/or customer. In general, the production cost of energy supplied from IPPs is lower than that of a utility, although the IPP energy has more uncertainty compared with the utilities energy. This paper analyzes the effects caused by IPPs from the following three points: (i) By modeling a process of determining purchased power price as a negotiation model, the authors evaluate the influence of its uncertainty on a potentiality to introduce IPPs through variation of the purchased price. (ii) The authors evaluate the difference of power system reliability between a system under the deregulated environment with IPPs and a conventional system without IPPs. It is assumed that the system reliability is determined by minimizing the sum of supply cost and outage cost. (iii) Finally, the authors evaluate how the customer's various requirements about reliability influence the introduced amount of IPPs. © 2000 Scripta Technica, Electr Eng Jpn, 131(1): 56–67, 2000 [ABSTRACT FROM AUTHOR]

This paper discusses optimal planning problems for dispersed generating sources so as to provide a guideline for their introduction to power systems. First, a recursive method is developed from the viewpoint of supplying electric power only where solutions for one unit are superposed. The computational loads are decreased by selecting alternatives of buses based on the so-called penalty factor. However, for effective utilization of dispersed generating sources, it is indispensable to consider their thermal merits in addition to electric power. After applying the Kuhn-Tucker theory to the optimal dispatching problem including boiler fuel costs, thermal values of the dispersed generating units are evaluated quantitatively. Finally, the above-mentioned technique for the optimal planning basically is also the proposed algorithms are demonstrated using a real-scale model system. [ABSTRACT FROM AUTHOR]

This paper proposes a new dynamic preventive control strategy to maintain power system security, in terms of both transient and midterm stabilities. While the authors have already presented preventive control strategies for transient stability, a new problem has arisen in midterm instability in which some generators lose synchronism after 10 seconds or more from a fault clearance. It is clear that the cause of the instability is mainly post-contingency dynamic steady-state instability. This paper first shows a preventive control strategy for improving midterm stability using a dominant eigenvalue of post-contingency equilibrium point. This paper also presents a unified dynamic preventive control algorithm that can maintain both stabilities together. In this algorithm, the time domain for each stability problem is considered appropriately and the difference between the classical model and the detailed model is analyzed in detail. The effectiveness of the proposed method is examined with numerical examples for a model system. [ABSTRACT FROM AUTHOR]

This paper presents a method for obtaining preventive control strategies based on nonlinear optimization for power systems which will incur voltage instability when load demand increases. An algorithm is proposed to determine an appropriate and effective control action taking into account the operating constraints to widen the margin between the present operating point and a voltage collapse point, thereby improving the system state. The method proposed here is based on a complex-valued load-flow technique using the Newton-Raphson method which has been developed already by the authors. Consequently, the preventive control algorithm also can evaluate the voltage instability in the event the present operating point becomes closer to the critical point and the system state becomes unfeasible at increased loading point. Further, in optimization, two-types of objective functions are introduced so that voltage stabilization and dissolution of constraint violation can be attained simultaneously. In addition, this paper discusses the extension of the proposed preventive control to the successive control method which carries out the control action to avoid voltage collapse while the load demand is increasing. Numerical examples for various model systems demonstrate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

To maintain power system security, the authors are developing an integrated security monitoring and control (ISMAC) system which consists of the three main functions: security monitoring, preventive control and emergency control. This paper focuses on the dynamic preventive control which deals with the transient stability assessment using the pattern recognition with two-dimensional feature space. Therefore, a preventive control strategy can be obtained rapidly. An index which represents the severity of the contingency quantitatively (security index) is defined by the distance from a linear decision surface which divides a feature plane into a stable and an unstable region. Further, this method has also the advantage that it is possible to consider the effect of the control devices or damping to some extent and specify the operator demand for stabilization flexibly. The effectiveness of the proposed method is ascertained through numerical examples for model power systems. [ABSTRACT FROM AUTHOR]

This article provides information on a study that proposed a preventive control strategy for an integrated security monitoring and control system. There are two categories underlying the preventive control problem: dynamical and statical. Information is presented on the P-Q decomposition used in the study. The objective functions of each sub-problem are discussed, as well as the effectiveness of the proposed technique in reducing operating costs.

The enforcement of a feed‐in tariff (FIT) program in Japan has increased the number of installations of photovoltaic generation systems in its residential sector. After the end of an FIT program, the surplus electricity of an individual prosumer is purchased by the utility company at a reduced price, which may have an economic impact on the prosumer. To avoid this adverse effect, peer‐to‐peer (P2P) electricity transactions among prosumers based on blockchain and smart contract technologies as well as introduction of residence‐use stationary storage batteries are generating significant interest. In this study, the potential economic merit of P2P transactions and residential storage battery introduction are evaluated using a total optimization approach. For realizing a more practical perspective, this study also investigates the economic merit based on a partial optimization approach, in which an individual prosumer pursues its own profit. Furthermore, in this study, the grid‐side merit of P2P electricity transactions among prosumers is examined. Comparison of the merits determined by the total and partial optimization approaches shows that the realization of P2P transactions could provide a notable economic merit to the participants and reduce both the required facility capacity and power flow variation. © 2022 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

Given the fluctuations in wind speed, wind power is always accompanied by uncertainty. An accurate forecasting of wind speed is critical to the effective operation of a power system. A hybrid forecasting system for 24 h-ahead wind speed forecasting is proposed in this article. This system applies complementary ensemble empirical mode decomposition to decompose wind speed data and uses permutation entropy to filter and reconstruct the decomposed components. Afterward, the ant colony optimization and genetic algorithms are used to optimize the initial parameters of the recurrent neural network containing the long short-term memory framework. This optimized neural network is then used to forecast the wind speed component and integrate the result. Numerical simulation results show that compared with traditional methods, this hybrid forecasting system has a better 24 h-ahead wind speed forecasting accuracy and a significantly higher forecast stability. This system is implemented by using the TensorFlow and Keras libraries. [ABSTRACT FROM AUTHOR]

Recent growth of renewable energy 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 cogeneration 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. [ABSTRACT FROM AUTHOR]

Network reconfiguration results in voltage deviations because of the time-varying nature of loads. Nowadays, with the integration of renewable energy sources with the power grid, the optimal configuration should be determined taking into account the variations in loads and distributed generations. In this study, a long-term reconfiguration method named the long-term extended flow algorithm, which improves the timeliness of configuration behavior on time-varying loads, is proposed to substitute for the previous short-term ones. Moreover, optimal reconfiguration instants are achieved by a novel approach of optimal daily schedule called accumulation of unbalanced load distribution based on the trade-off between switching operations costs and reduction in voltage deviations. The proposed methods were tested by case studies of two test distribution systems under real-time measured data with the interconnection of photovoltaic generators in the MATLAB environment. By applying the proposed methods, the total operating cost of the network is reduced significantly within reasonable computation time, and its efficiency is also improved compared to fixed configuration, online reconfiguration policies, and daily schedule proposed by previous authors. © 2017 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [ABSTRACT FROM AUTHOR]

The supervisory control and data acquisition (SCADA) system is used in power systems worldwide because of its maturity and capability. However, the SCADA system is vulnerable to fast system changes. Wide area monitoring system (WAMS) based on phasor measurement units (PMUs), which requires high investment, is being thought of as one of the solutions in recent power systems. This paper proposes a procedure to upgrade SCADA into WAMS by installing sufficient numbers of additional PMUs without removing conventional measurements from the existing SCADA system. The WAMS hybrid configuration is focused on the optimal PMU placement and state estimation strategy for hybrid PMU-SCADA measurements. The optimal placement of PMUs is subject to the improvement in estimation accuracy. For guaranteeing secure operation, line contingencies and some important buses are considered as subproblems of PMU placement. The state estimation procedure manages the initial state variable and modifies the weighting factor strategy that is suitable for the hybrid system especially during fast system changes. The results show that the proposed WAMS hybrid guarantees better estimation accuracy and faster state estimation process than SCADA in both non-contingency and contingency conditions. In addition, the WAMS hybrid has the capability to perform preventive strategy for securing voltage stability, which was previously applied in the PMU-based WAMS system. © 2017 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [ABSTRACT FROM AUTHOR]

The interconnection of distributed generators (DGs) in a power system increases the difficulty of managing the system. The minimization of the voltage deviation by network reconfiguration is an important requirement for dealing with the issue. We had previously developed a reconfiguration technique, named the intelligent flow algorithm (IFA), for determining the optimum or suboptimum network configuration within a short computation time. In the present paper, we propose an extension of IFA, named the extended flow algorithm (EFA), for more effective determination of the optimal network configuration of a distribution system containing massive installations of DGs. EFA is a two-stage method in which the configuration that produces uniform power supply, referred to as the balanced configuration, is first generated, and then used to seek the optimal configuration using an improved branch exchange approach. Accordingly, EFA is more simplified to improve its computation speed on large-scale systems. The algorithm was tested by case studies of different test distribution systems in the MATLAB environment, and was confirmed to have high performance to cope with DG installations and large-scale systems. © 2017 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [ABSTRACT FROM AUTHOR]

The high degree of penetration of residential rooftop photovoltaic systems causes the overvoltage problem in power distribution systems. This paper aims to introduce demand-side management for a distribution system for overvoltage prevention. A real-time overvoltage prevention coordination scheme between an on-load tap changer ( OLTC) and multi-community energy management systems (multi- CEMSs) is proposed. The main objectives of this control are to relieve the stress in the OLTC tap operation using household schedulable loads and to maximize customer profit in each CEMS. The load scheduling performed by each CEMS is formulated as a combinatorial, nonlinear, time-series scheduling optimization problem and is solved by a sequential search method named voltage-ranking-based load combination search algorithm. The effectiveness of the proposed method is validated in a model distribution system with1800 customers. © 2017 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [ABSTRACT FROM AUTHOR]

Demand response ( DR), which is used to shave the peak demand for securing supply reliability in a power system, is one of the promising constitutions for the end users. In a commercial building ( COB), the most popular adjustable DR resource ( DRR) is the chiller system. More specifically, its power consumption can be reduced by thermal mass control (precooling) in a specified DR duration. On the other hand, installation of energy storage systems ( ESSs) is going on at an accelerated pace because of its high economic efficiency. ESSs have been used for peak-shift operation under the time-of-use ( TOU) tariff. However, ESS can be also used as an attractive DRR because it can reduce the net load by discharging the ESS for a specified DR duration. Based on this background, this paper presents a method for determining the optimal DR capacity in a COB with a chiller system and ESS. In the proposed scheme, the optimal DR capacity ( kW) can be determined so that the total expected cost of a COB becomes minimum by using the chiller system and ESS while avoiding the DR penalty threat adopted in the Korean DR market. Uncertainty in the ambient temperature, the amount of reduction, and DR durations are considered as the scenarios. The estimation and economic evaluation of the proposed scheme is ascertained through case studies. © 2017 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [ABSTRACT FROM AUTHOR]

• Microgrid construction for power system stabilization. • Sector coupling between electricity, heat, and hydrogen demand. • Formulate a multi-objective optimization problem. • Integrating all electricity, heat, and hydrogen is effective. This paper discusses how the contribution of microgrid (MG) introduction to the power grid depends on sector coupling. MG is designed to suppress the residual demand from the grid and its variation, under the cost constraint. In this paper, three levels of sector coupling are considered for electricity, heat, and hydrogen demand. In Lv.1, the MG supplies only electricity to the demand. The MG is equipped with photovoltaic (PV) and storage battery. In Lv.2, the MG equipped with PV, storage battery, heat pump, chiller, thermal tank, and hydrogen gas boiler to supply both electricity and heat to demand. For heat delivery, heat pipeline network is laid and used. In Lv.3, all electricity, heat, and hydrogen supplies are coupled at MG. From the obtained results, it is ascertained that the higher sector coupling can realize the higher flexibility in residual demand. [ABSTRACT FROM AUTHOR]

SUMMARY To reduce the environment load, electric vehicles (EV) have been attracting attention and expectations. since they can run with at good fuel efficiency and without exhaust gases. It is expected that EV will become more and more popular. Generally, EVs would be used for driving during daytime and be charged during the nighttime, considering lifestyle and time-of-use patterns. If most EV owners adopt this use pattern, feeder voltage profiles could be greatly affected, causing severe voltage drops. The battery charger for EVs described in this papers consists of a self-commutated inverter, which in principle can control not only active power but also reactive power. We propose a basic feeder voltage regulation algorithm, 'PQ control', using EVs which involves adjustment of the EV charging schedule and reactive power injection. In addition, we propose 'prediction control', which is based on 'PQ control' and is takes account of prediction of the receiving voltage. Advanced 'communication control' regulation algorithms, utilizing communication among EVs and the distribution system operator, are also proposed. The purpose of this paper is to confirm the effectiveness of the three proposed algorithms by simulations. [ABSTRACT FROM AUTHOR]

In the future, renewable energy (RE) generation systems will be constructed and interconnected to the power system by nonutility entities such as generation companies and residential customers. Therefore, generation expansion planning (GEP) should consider the effects of RE generation. The purpose of this paper is to discuss the best GEP from the economic, supply reliability, and environmental aspects considering the penetration of RE generation. For this purpose, this paper proposes a model of a utility's GEP process considering RE generation. The proposed method is based on stochastic dynamic programming (SDP) in which long-term uncertainties are modeled by geometric Brownian motion (GBM) and the binomial lattice process. The variation of RE generation output due to the weather conditions (short-term uncertainty) is also considered in the proposed method by means of the net load curve. [ABSTRACT FROM AUTHOR]

Penetration of photovoltaic (PV) generation system into the power system may have some negative effects on stable operations of the power system; for example, on frequency control. Therefore, investigation of the short-term fluctuations of PV generation is important as a precaution for further PV penetration. Since PV generation is approximately proportional to the incident solar radiation, this paper develops static and dynamic characteristic models for short-term fluctuations of global solar radiation. The static characteristic model is a set of standard deviations which have been statistically estimated based on past observed data. The dynamic characteristic model consists of autoregressive models which are designed for actually observed time-sequential short-term fluctuation data. In both models, the clearness index is used to eliminate seasonal variation of solar radiation. [ABSTRACT FROM AUTHOR]

Reactive power supply plays an important role in active power supply with adequate system voltages. Various pricing mechanisms for reactive power supply have been developed and some of them have been adopted in some power systems, but they are in a trial stage. The authors also focus on development of a pricing method for reactive power ancillary services. This problem involves two technical issues: rational estimation of the cost associated with reactive power supply, and fair and transparent allocation of the estimated cost among the market participants. This paper proposes methods for evaluating the contribution of generators and demands. © 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 174(2): 36-45, 2011; Published online in Wiley Online Library (). DOI 10.1002/eej.21016 [ABSTRACT FROM AUTHOR]

The authors have proposed Flexible, Reliable and Intelligent ENergy Delivery System (FRIENDS) as a future power distribution system. In the FRIENDS, new facilities called quality control centers (QCCs), which consist of power electronics devices, distributed generators (DGs), energy storage systems (ESSs), etc., are installed between distribution substations and customers. By controlling and operating those devices in QCCs adequately, various functions can be realized. Particularly, when a power supply from the transmission network is interrupted, isolated local networks which consist of some QCCs are composed in order to realize uninterruptible power supply. In the isolated local network, the DG and ESS in QCCs are employed as backup generators. This paper proposes a novel distributed and autonomous method for balancing the supply and demand during isolated operation. This paper also investigates the effectiveness of the proposed method through some computational simulations using PSCAD/EMTDC. [ABSTRACT FROM AUTHOR]

In order that the supply of electric power remain stable and sustainable, a certain level of power quality must be maintained while securing energy resources and resolving environmental issues. The distributed generation (DG) has become an essential and indispensable element of such distribution systems from both an environmental and an energy security perspective. However, the installation of DGs in distribution systems may cause variations of voltage on distribution feeder because the DG power outputs may change randomly and dramatically. Generally, the sending voltage at substation in distribution systems can be regulated by an under load tap changer (ULTC) designed to maintain customers' receiving voltages within a predetermined range. Voltage regulation performed by ULTC calls for two parameters: the equivalent impedance and the load center voltage. Therefore, in distribution networks with DG interconnections, these parameters should be designed with attention not only to load variations but also to DG outputs. This paper proposes a method for designing ULTC parameters with reference to variations in DG output. The proposed algorithm is tested with IEEE 13-node system and Korean model network. The results demonstrate the validity of the proposed design method for varying DG distribution. [ABSTRACT FROM AUTHOR]

The authors have proposed a new concept of a distribution system “Flexible, Reliable and Intelligent ENergy Delivery System (FRIENDS)” with intent to solve imminent operating problems faced by utilities in providing their customers with reliable supply of power at several levels of quality. The main idea of FRIENDS is to introduce new facilities, so-called Quality Control Centers (QCCs), which are installed very close to the customers for the purpose of implementing multiple functions, such as Customized Power Quality Service. In addition, these QCCs form a network for energy and information transmission at a level below distribution substations. QCCs make it possible to frequently change configuration of the network depending on the system and load conditions. These frequent reconfigurations of the network require fast and reliable Transfer Switching in the QCCs to ease an effect on customers. The reconfiguration for the purpose of fault area isolation also requires a fast Fault Detection feature. This paper presents a new method for controlling Transfer Switching and a method of Fault Detection in order to realize a fast and reliable reconfiguration of QCC network in a normal state, as well as under fault conditions. This paper also analyzes the methods in terms of instantaneous values calculated by PSCAD/EMTDC. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 148(3): 25–35, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10298 [ABSTRACT FROM AUTHOR]

Recently, the worldwide deregulation of the electric power industry is progressing. Further, it is expected that a many distributed generation facilities and energy storage systems will be installed at the end point of the power systems. Therefore, the future power system must be able to cope with these various qualities of power in the deregulated situation. The authors have proposed the FRIENDS (Flexible, Reliable, and Intelligent ENergy Delivery System) concept as a new distribution system that copes with a new framework of the electric power business in the near future. The most typical aspect of FRIENDS is the introduction of new equipment; Quality Control Centers (QCC) between distribution substations and customers. In this paper, the authors propose a concrete interior structure and investigate some control methods for realizing unbundling power quality supply and power conditioning using the proposed UPQC-type QCC. The effectiveness of the proposed method is confirmed through the instantaneous value analysis using PSCAD/EMTDC. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 146(3): 26–38, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10243 [ABSTRACT FROM AUTHOR]

In recent years, the introduction of superconducting magnetic energy storage systems (SMES) into a power system is drawing considerable research effort because of their high efficiency rate and large storage capacity characteristics. In this paper, the introduction of SMES into a power system and its effects on energy and on environmental issues are addressed. The analysis results show that the introduction of SMES can considerably cut down CO2 emissions without increasing the production cost if it substitutes for the operation of thermal plants during peak load period. However, to achieve this, nuclear plants are also needed for charging purposes. Thus, an algorithm to find the best generation mix, subject to CO2 emissions constraints and nuclear plant introduction constraints, is proposed. The inclusion of nuclear plant constraints increases the coal consumption, hence CO2 emissions. Nevertheless, in most of the analyzed cases, the introduction of SMES could attain important cost savings and environmental conservation. © 2000 Scripta Technica, Electr Eng Jpn, 131(1): 32–44, 2000 [ABSTRACT FROM AUTHOR]

Multiple factors regulate glucagon-like peptide-1 (GLP-1) secretion, but a group of apparently healthy subjects showed blunted responses of GLP-1 secretion in our previous study. In this study, we examined whether the reduction in GLP-1 secretory capacity is associated with increased extent of coronary artery stenosis in non-diabetic patients. Non-diabetic patients who were admitted for coronary angiography without a history of coronary interventions were enrolled. Coronary artery stenosis was quantified by Gensini score (GS), and GS ≥ 10 was used as an outcome variable based on its predictive value for cardiovascular events. The patients (mean age, 66.5 ± 8.8 years; 71% males, n = 173) underwent oral 75 g-glucose tolerant tests for determination of glucose, insulin and active GLP-1 levels. The area under the curve of plasma active GLP-1 (AUC-GLP-1) was determined as an index of GLP-1 secretory capacity. AUC-GLP-1 was not correlated with fasting glucose, AUC-glucose, serum lipids or indices of insulin sensitivity. In multivariate logistic regression analysis for GS ≥ 10, AUC-GLP-1 < median, age and hypertension were selected as explanatory variables, though fasting GLP-1 level was not selected. The findings suggest that reduction in GLP-1 secretory capacity is a novel independent risk factor of coronary stenosis. [ABSTRACT FROM AUTHOR]

[Display omitted] • The data area division method is proposed to divide wind speed data into areas. • Noise reduction and decomposition strategy of data for wind speed time series. • Genetic algorithm-optimized deep learning neural networks are used. • Forecasting of wind speed time series for different time intervals. • The wind power impact indicator is proposed to judge the forecast deviation. Wind speed forecasting is essential for the dispatch, controllability, and stability of power grids, and its accuracy is vital to the effective use of wind resources. In this study, a novel hybrid wind speed forecasting system is developed based on the data area division (DAD) method and a deep learning neural network model. The system consists of three modules: extraction module, data preprocessing module, and forecasting module. In the data extraction module, a large amount of valid historical data is extracted, filtered, and classified from the forecast location and the surrounding locations. In the data preprocessing module, complementary ensemble empirical mode decomposition is used to decompose the wind speed data. In the forecasting module, a long short-term memory network optimized by using a genetic algorithm is used to forecast the decomposed wind speed data and integrate them into the final forecast results. Numerical simulation results show that (a) the forecast system maintains RMSE in the range of 0.2–0.6 m/s and MAPE in the range of 3.0–7.0% for short-term wind speed forecasts at different locations for different time periods, showing good stability. (b) For wind speed forecasting at different time intervals, the accuracy of wind speed forecasting at 10-minute and 30-minute intervals is better, while the accuracy of forecasting at a 60-minute interval needs to be improved, but overall, the forecasting system shows good generalizability. (c) The forecast system improves the forecast accuracy of short-term wind speed forecasting more effectively than other conventional methods, and the improvement of RMSE and MAPE remains in the range of 14–39% and 13–27% even compared with the hybrid forecast model that has better forecast accuracy. (d) For area-wide short-term wind power forecasting, the forecast deviation value of this forecasting system remains below 6% throughout the year, showing good practicality. [ABSTRACT FROM AUTHOR]

Renewable energy (RE) sources like wind and solar power have been introduced to power systems to make the energy market more sustainable and environmentally friendly. For this reason, the supply-demand mismatch in power systems is more severe than before, in terms of both frequency and magnitude. It is therefore necessary to reinforce the capability to make supply and demand adjustments in power grids. Here, we clarified the dynamic characteristics of biogas plants with combined heat and power (CHP) systems, that represent controllable RE power sources, and evaluated the possibility of using these systems as a new resource for supply-demand adjustments in the power grid. Additionally, the properties of the exhaust gas from the investigated CHP engines were measured as an environmental evaluation. We considered real-world biogas CHP systems operating in both Germany and Japan. Based on the results, biogas CHP systems have the potential to contribute to a long-term power equivalent adjustment such as tertiary control reserve (TCR) in Germany. However, these systems required several minutes between starting and stopping. Furthermore, increased emissions of methane and formaldehyde were measured when the CHP systems were starting up. We found that an operation with as few starts and stops as possible is therefore desirable. • Evaluation of the dynamic characteristics of actual biogas CHP systems. • Investigation of load response with biogas CHP systems operating in Germany and Japan. • Analysis of load adjustment as well as start-up and shut-down behavior of CHP systems. • Measurement exhaust gas emissions during supply-demand adjustment. • Biogas CHP systems can contribute to long-term power equivalent adjustment. [ABSTRACT FROM AUTHOR]

SUMMARY Penetration of photovoltaic ( PV) generation system into the power system may have some negative effects on stable operations of the power system; for example, on frequency control. Therefore, investigation of the short-term fluctuations of PV generation is important as a precaution for further PV penetration. Since PV generation is approximately proportional to the incident solar radiation, this paper develops static and dynamic characteristic models for short-term fluctuations of global solar radiation. The static characteristic model is a set of standard deviations which have been statistically estimated based on past observed data. The dynamic characteristic model consists of autoregressive models which are designed for actually observed time-sequential short-term fluctuation data. In both models, the clearness index is used to eliminate seasonal variation of solar radiation. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 186(2): 10-20, 2014; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.22469 [ABSTRACT FROM AUTHOR]

Presents a study which developed a manufacturing process of piezoelectric thin film dual-state actuator for positioning a magnetic head for high density hard disk drives. Microactuator structure and fabrication; Effect of internal stress on specific inductive capacity; Migration test results.