Hideharu Sugihara

Economic and Efficient Voltage Management Using Customer-Owned Energy Storage Systems in a Distribution Network With High Penetration of Photovoltaic Systems

The widespread installation of distributed generation systems is crucial for making optimal use of renewable energy. However, local distribution networks face voltage fluctuation problems if numerous photovoltaic (PV) systems are connected. Recently, energy storage systems that can be installed at commercial customers have been developed. This paper proposes a concept that solves the voltage fluctuation problem in distribution networks with high penetration of PV systems by using customer-side energy storage systems. The distribution network operator (DNO) is allowed to control the output of the energy storage systems of customers during a specific time period in exchange for a subsidy covering a portion of the initial cost of the storage system. The cost effectiveness of the cooperative operation for both customer and DNO is discussed by numerical simulations based on minute-by-minute solar irradiation data. Our results have clarified the possibilities of making voltage management more economical in distribution networks.

Analyzing the system effects of optimal demand response utilization for reserve procurement and peak clipping

In this paper the effect of demand response (DR) resource utilization in the system operation is analyzed by using an optimization based simultaneous market clearing framework. Two distinct utilization patterns that DR can be involved are reserve supplying by Reserve Supplying Demand Response (RSDR) and providing actual curtailment for demand reduction or peak clipping by Peak Clipping Demand Response (PCDR). The provider of RSDR will sell its ability to tolerate probable curtailment and the PCDR will sell its real curtailment ability. These utilizations have different effects on system indices. Therefore the effect of different DR utilization patterns are analyzed and compared in this paper. IEEE RTS is selected as the test case for studying the effect of DR utilization patterns.

A new operation framework of demand-side energy storage system cooperated with power system

Energy storage systems have increasingly been expected as a means of load leveling of the annual load factor in Japan. The demand-side energy storage system has the effects for not only improving load factor, but also for black out compensation or voltage sags. So it is expected to wide spread in the future. Then the authors proposed a method that the energy storage systems at customer side are used for a congestion relief on transmission networks. Consequently it is cleared in this paper that which kind of customers has the effect of relieving transmission line congestion. First of all, the authors determine the optimal configuration of energy system including energy storage system. By using an optimal power flow with unit commitment as an evaluation index of electric utility, this paper evaluates the possibility that gives cost merit to both the electric utility and the customer from economic point of view.

Optimal spinning reserve procurement using demand response in simultaneous clearing process

The objective of this paper is to study the effect of Demand Response (DR) in the optimal spinning reserve scheduling process. A probabilistic method is proposed which considers the probabilistic nature of contingencies and the value that customers consider for their electricity consumption continuity. The method does not use any pre defined external reliability index constraint or risk proxy as the criteria and considers interruption cost explicitly in the objective function. In this paper also the effect of single and double outage consideration in the interruption cost and its effect on DR utilization have been analyzed. The method has been tested on a 7 unit test case and the numerical results have been presented.

An economic effect of demand response with Thermal Storage Air-conditioning systems in electricity markets

This paper evaluates the economic effect of the Demand Response (DR) with Thermal Storage Air-conditioning (TSA) systems in electricity markets using market models based on the California Power Exchange (Cal-PX) and the Australian National Electricity Market (NEM). Our main objective is to evaluate the reductions in the Market Clearing Price (MCP) and wholesale purchase costs for all market participants by implementing the DR program. The DR program with TSA systems results in MCP reductions by shifting electricity demand for air-conditioning from on-peak to off-peak hours, and that economic benefit can be realized not only for the DR program owner but also for all purchasers in the electricity market. This paper also discusses the differences between the results obtained from the Cal-PX model and the NEM model.

A method for evaluating installable capacity of distributed generators with power factor control in MV and LV distribution networks

Local distribution networks face voltage-rise problems when numerous distributed generators (DGs) are connected. In particular, voltage rise at low-voltage wires or service wires is a significant because of their high resistance. This paper proposes a methodology for evaluating the installable capacity of DGs under bus-voltage constraints in medium- and low-voltage distribution networks in consideration with power factor control of DGs. Three different installation scenarios for DGs (ideal maximizing DG capacity case, neutral equally maximizing case, and worst minimizing case) are analyzed in medium- and low-voltage networks. Moreover, it is found that the installable capacity of DGs can be increased by using power factor control of inverter-based DGs.

An economic impact of thermal storage air-conditioning systems in consideration of electricity market prices

This paper evaluates the economic impact of the introduction of customer-owned thermal storage air-conditioning (TSA) systems in a deregulated electricity market from the viewpoint of the load service entity (LSE) and the whole-trade cost in the electricity market. Using market electricity demand and market clearing price (MCP) data based on the California Electricity Market 1999, our numerical results indicate that the LSE reduced the purchase cost of electricity at the MCP through the load managements of customers by operating TSA-systems instead of conventional air-conditioning (AC) systems. The introduction of customer-owned TSA-systems also reduced the variation of the MCP by shifting total market demand from on-peak to off-peak hours, and reduced the whole-trade cost in the electricity market. Thus, this paper provides the customer-owned TSA-systems contribution to the reductions in the purchase cost of the LSE and the whole-trade cost in the electricity market.

A multi-objective optimization model for urban energy systems in a specific area

Considering CO/sub 2/ emission, energy consumption and economic indices as evaluation factors, this paper proposes a new multi-objective optimization model for determining urban energy systems in a specific area. The proposed model is applied to an actual city in Japan, and the tradeoff relation among three indices is analyzed. The results show the roles of the energy system alternatives from viewpoints of CO/sub 2/ emission and primary energy consumption, respectively.

A short-term dynamic thermal rating for accommodating increased fluctuations in conductor current due to intermittent renewable energy

Implementation of a dynamic thermal rating (DTR) which periodically re-calculates conductor ampacity as ambient weather conditions change can increase line loadability when compared to the static thermal rating (STR). However, in recent years the direct use of temperature limits, whether directly or indirectly measured, has been shown to provide even higher loadability because of the conductor thermal inertia characteristic. This paper presents a short-term dynamic thermal rating referred to as dynamic electro-thermal rating (DETR), which incorporates both conductor thermal dynamics and changes in ambient weather conditions in its calculation. In this way, DETR is able to include the conductors thermal inertia characteristics in the determination of maximum allowable current and consequently result in loadability limits that are less conservative than the DTR. Presented simulation results show that DETR would allow for higher fluctuations in conductor current as compared to the DTR and can therefore be especially useful for conductors that experience large power fluctuations due to increased intermittent renewable energy sources in the network.

An evaluation of the influence caused by the introduction of IPP considering the uncertainty of supply capability

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 customers various requirements about reliability influence the introduced amount of IPPs.