The penetration of photovoltaic power generation (PV) in the utility system is increasing rapidly. Many issues such as voltage fluctuation in distribution system, occurrence of surplus power in whole utility system, increase of reserve margin, destabilization of the utility system in the event of system fault, etc. may become more remarkable with the massive penetration of PV.
In the paper, those assumed issues and recent trends of PV operation and control techniques for the massive penetration such as new distribution line voltage control methods cooperated with the voltage control devise installed in the distribution system, restraint method of PV surplus power using communication network, etc. are described. New measures of the utility system side such as new fast response type voltage regulator for distribution system, new LFC method using large scale storage battery, operation technique of existing synchronous generator to cope with destabilization of the utility system, etc. are also introduced.
In this paper, we propose a priority control method for a step voltage regulator (SVR) considering reactive power of a static var compensator (SVC) in distribution network. The method enables SVR to estimate voltages of distribution line without SVC and SVR to decide SVR tap position considering the estimated voltage. SVC operation data transmitted to SVR via communication network is used to estimate the line voltage. The method enables SVC to reduce the short term voltage fluctuation and to reduce the long term voltage fluctuation cooperatively. The method is also applicable using intermittent telecommunication.
Fuel cells and photovoltaic systems are increasing in distribution networks for reduction of CO2 emission. These power sources require inverters to connect to ac network. There is a possibility that sub-network, called as microgrid, containing inverter power sources will be disconnected from the utility network and operated as standalone mode. This paper focuses on a standalone microgrid supplied by inverter power sources without synchronous generator, and proposes new inverter control in the microgrid. The feature of the inverter control is that one inverter is operated as a master power source mainly determines frequency and voltage, and the other inverters are operated as subordinate power source with active and reactive power control. Coordinated operation of all inverters in the microgrid is obtained.
Generally, if the power transmission lines are heavily loaded, the transient stability and frequency stability tend to be worse, and one power system fault may cause wide-area blackouts. However, restriction of the power flow sacrifices economical operations. To solve this problem, CEPCO (Chubu Electric Power Co., Inc. ) had implemented the Online Stability Control System.
Since current system was constructed more than 20 years ago, the situation of power system has drastically changed such as a large scale introduction of Distributed Energy Resource (DER) or increase of cross-regional power interchange. To cope with these changes, we are developing a new Stability Control System with new control functions. And, the new system integrates the current systems which were constructed separately for the purposes. As the result, the number of equipment was dramatically reduced.
This paper describes the outline of developing system and the new stability control functions to overcome various situational changes which have happened in CEPCO power grid.
The output fluctuation of renewable energy generation may disturb the stable power system operation. Against this issue, the authors are investigating the feasibility of Power to Heat (P2H) technology, in which co-generation systems and other heat-supply devices are utilized cooperatively to provide adjustable electricity generation/consumption. This paper introduces the heat pump (HP) and the biogas engine generator (BG) system as one of the P2H technology, and proposes the detailed control strategies. The proposed control strategies are composed of “day-ahead scheduling” and “real-time operation”. Day-ahead scheduling decides operation schedules for HP and BG which minimize total output fluctuation using forecasted output of wind farm. Real-time operation revises the result of day-ahead scheduling to satisfy the control target using actual output of wind farm. Effectiveness of those proposed control strategies are evaluated computational simulations.
In the SF6 gas disconnector, a loose connection and an abnormal overheating of the contact may be caused by aging and multi-frequency operation. To detect the loose connection of the disconnector, we developed the condition assessment method that used the SF6 decomposition gas. The proposal technique uses the amount of CF4 in an internal insulation gas with the operation frequency of the disconnector, and we investigated the insulation gas of the disconnector in the actual substation. When the developed method was applied for field apparatus, it was judged that five apparatuses were abnormal. Therefore, the major inspection was executed later for four apparatuses of them, and, as a result, internal abnormalities were discovered at all apparatuses.
In Japan, including in the Chugoku region, overhead groundwires and surge arresters are used as lightning protection equipment on power distribution lines. Nowadays, surge arresters are installed at regular intervals (200-300m; every 4-6 spans) on distribution lines. Recently, current-limiting arcing horn with zin c oxide elements have additionally been installed on power distribution lines as lightning protection equipment. However, there has been little quantitative evaluation of the effect of installing surge arresters and current-limiting arcing horn with zin c oxide elements on distribution lines on reducing lightning outage and the construction cost. It is very important to evaluate their cost and their effect on reducing lightning outage.
In this paper, we show an analytical study of rational lightning protection measures with these equipment for power distribution lines using assessment method of lightning risk. Then we propose rational lightning protection measures in the Chugoku region.
The leakage current behaviors of MOVs (Metal Oxide Varistors) having different conditions of manufacturing process were investigated and distinguished into 4 categories. It is confirmed that the behavior of leakage current during DC application are quite similar to those during AC application. The initial leakage current, dominated by the applied voltage ratio, and the temperature during the ageing test are the principal factors on variation of leakage current. As the index to judge the degradation, the varistor voltage at DC several μA to mA in both directions is more sensitive and effective than the behavior of leakage current.
Metal wires are widely used for arc ignitions in power arc tests on electrical power installations, and their material and thickness are selected variously. However, the material and thickness of the metal wire are thought to be influential factors in the severity of the power arc test, because they may change the arc duration and the physical characteristics of arc. In this paper, we made the experiment, where arcs were generated in a closed chamber by two ignition methods. one was with using various metal wires for ignition, and another was without using them, namely with causing dielectric breakdown due to imposing the impulse high voltage. From the results, the difference of characteristics between arcs with and without using metal wires for ignition was investigated, focusing on the arc energy and the internal pressure rise, which can be seen as indexes of the severity of the power arc tests. Consequently, we pointed out that the severity of the power arc tests with using metal wires investigated in this study may be equal to or more than that of the tests with causing dielectric breakdown if there is little difference in the time integral of current during the arcing time.