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SUMMARY The high penetration of variable sources of renewable power generation will lead to operational difficulties in supply/demand balancing in the entire power system. The mass deployment of electric vehicles (EVs) and plug-in hybrid vehicles (PHEVs) will also cause significant changes in electricity demand. Therefore, controlling and managing the charging time of EVs/PHEVs are effective approaches that are imperative for improving balancing in power system operation. We assumed travel patterns for EVs in a model of the future Tokyo power system and analyzed the power system loads, including the charging load of the EVs, under several charging control scenarios. We verified that charging time controls are substantially effective for reducing the fuel costs in the power system. Further, we found that load leveling under a multicar charging management scenario gave the best results in terms of the fuel costs in all cases. [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]

This paper presents an evaluation of the impact of extensive introduction of photovoltaic (PV) systems and stationary battery technology into the optimal power gen-eration mix in the Kanto and Kinki regions. The introduc-tion of solar PV systems is expected to be extensively deployed in the Japanese household sector and utility com-panies in order to address the concerns of energy security and climate change. Considering this expected large-scale deployment of PV systems in electric power systems, it is necessary to investigate the optimal power generation mix which is technologically capable of controlling and accom-modating the intermittent output-power fluctuations inher-ent in PV systems. Against this background, we develop both a solar photovoltaic power generation model and an optimal power generation mix model, including stationary battery technology, which can be used to explicitly analyze the impact of PV output fluctuations at a detailed time interval resolution such as 10 minutes for 365 consecutive days. Simulation results reveal that PV introduction does not necessarily increase battery technology due to the cost competitiveness of thermal power plants in the load-follow-ing requirement caused by PV systems. Additionally, on the basis of sensitivity analysis on PV system cost, dramatic cost reduction proves to be indispensable for PV to supply bulk electricity similarly to thermal and nuclear power plants. © 2012 Wiley Periodicals, Inc. Electr Eng Jpn, 182(2): 9-19, 2013; Published online in Wiley Online Library (wileyonlinelibrary.com). [ABSTRACT FROM AUTHOR]

Despite substantial progress of research efforts in the field of photovoltaic (PV) power generation, some serious problems remain to be solved, including a fairly low energy generated by PV systems in comparison to the expected output, and a broad spread of output values among individual PV systems. The expected level of generated energy is usually evaluated by means of such coefficients as “the performance ratio” which is obtained as the energy actually generated by a PV array over a period of 1 year divided by the calculated output over the same period. However, this method has some limitations, such as the necessity to continuously perform data measurements over a long time, difficulties in the examination of factors reducing the level of the generated energy or improving the system efficiency, and so on. In this study, the authors propose a new method of accurate evaluation of the generated energy. The authors also examined a method for classifying the losses caused by the rise of the PV cell temperature and presented a method of data measurements over a short time period. The proposed method can also be applied to the classification and analysis of losses occurring at the time of the MPPT operation of the system (Pmax operation). © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 154(4): 24–33, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20222 [ABSTRACT FROM AUTHOR]

The suitable hybrid configuration of Darrieus lift-type and Savonius drag-type rotors for stand-alone wind turbine-generator systems is discussed using our dynamic simulation model. Two types of hybrid configurations are taken up. Type A installs the Savonius rotor inside the Darrieus rotor and Type B installs the Savonius rotor outside the Darrieus rotor. The computed results of the output characteristics and the dynamic behavior of the system operated at the maximum power coefficient points show that Type A, which has fine operating behavior to wind speed changes and can be compactly designed because of a shorter rotational axis, is an effective way for stand-alone small-scale systems. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 150(4): 13–22, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20071 [ABSTRACT FROM AUTHOR]

Since the present hierarchical power grid structure and AC interface are mature and rigid, a new electric power system architecture is proposed here to save the earth by making use of renewable energy sources. The architecture consists of a new concept and a historical technology, that is, a network of many “electric clusters” with a DC interface. The cluster includes dispersed electric power generators, electric appliances, electric storage, and “electric power routers.” The router is equipment to resourcefully route electrical energy between neighboring clusters and to manage electrical energy in the cluster. The transfers of electrical energy (between clusters and within clusters) and the generation of electricity from renewal energy sources (such as sunlight, wind, tides, and biogas) are intermittent and have very wide dynamic ranges, so that the interface must make use of DC. When we achieve an energy society with this architecture, we will be able to reduce energy consumption, greenhouse gas emissions, and materials use. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 150(1): 18–25, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20039 [ABSTRACT FROM AUTHOR]

Recently, there has been growing interest in utilizing dispersed generation systems, which are grouped into micro turbine systems, co-generation systems, and so on, as a substitute for fuel oil energy and a technology to prevent global warming. Since start-up time of dispersed generation systems is short, it is possible to operate systems to supply load power corresponding to a demand. Moreover, PPSs (Power Producers and Suppliers) can participate in a power retail sales company, since deregulation of electric utilities was instituted in March 2000. However, PPSs have to keep instantaneous generating power commissioning rule, to maintain supply-and-demand balance between customer and supplier. Therefore, in this paper, we examine instantaneous generating power commissioning for dispersed generators where start-up time is short and it is possible to operate systems to supply a power load corresponding to a demand. We adopt a PI controller as a controller. The system is composed of double control loop in inner loop and in outer loop. In inner loop electric power is controlled and in outer loop electric energy is controlled. The controller parameters are designed using the pole-placement technique. The effectiveness of the proposed control system is confirmed by simulations. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 145(2): 58–66, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10200 [ABSTRACT FROM AUTHOR]

The MHD flow behavior and the performance of an experimental nonequilibrium subsonic disk MHD generator driven by a shock-tube facility have been examined with time-dependent r-z two-dimensional and r-θ-z three-dimensional Large Eddy Simulation for the first time. The calculation region is extended and covers a hot duct through a downstream duct including the subsonic MHD generator with two throats. For optimal and high load operations, the flow chokes at the downstream throat and the subsonic flow is maintained in the generator channel. The discharge structure is uniform in the θ direction, and suitable fluid flow is realized in the generator channel, although the large boundary layer separations and eddies are observed behind the downstream throat. For low load operations, the flow chokes at the upstream throat and the flow becomes supersonic, where pseudo-shock waves and large eddies are observed in the generator channel and the downstream duct. The ionization instability in the r-θ plane occurs in the generator channel, which deteriorates the generator performance. Asymmetric flow at the generator inlet, which is attributed to the change of flow direction from the hot duct, seems not to be significant for the generator performance. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 143(3): 1–8, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10130 [ABSTRACT FROM AUTHOR]

In recent years, the trend has been toward factors (e.g., demand for load, energy cost) becoming more and more uncertain in power system expansion planning. Thus, it has become necessary to take this uncertainty into account in determining generation plans. In this paper, a robust generation plan is defined explicitly as a plan that ensures fixed performance (economy) despite deviations in these factors. In addition, a new formulation of the robust generation mix problem, whose purpose is to determine the most robust combination of plants in a target year, is proposed. It is generally difficult to solve the formulated problem with parameters. However, by analyzing a proposed formulation from the viewpoint of optimization, we show that the proposed formulation is transformed into the conventional optimization problem without parameters. The simulation results on a typical model show that the generation mix produced by the proposed formulation is more robust than that produced by the conventional formulation. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 141(1): 26–35, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.2009 [ABSTRACT FROM AUTHOR]

A thermoelectric generator has been manufactured and evaluated for the purpose that the behavior of heat conduction and power generating performance can be clarified when the thermoelectric generator is powered by a high-temperature heat transfer medium oil over 500 K. The thermoelectric generator needs a compression fitting mechanism which holds heat sinks and thermoelectric generating modules so tight that desirable heat conduction can be maintained for thousands of heat cycles. The pressure required for the compression fitting mechanism was experimentally investigated with a trial manufactured thermoelectric generator. As an experimental result the compression fitting mechanism of the modules requires 0.28 MPa compressive load, which is 80% less than the recommended value by one of the module manufacturers. Electricity obtained by the trially manufactured thermoelectric generator with bismuth telluride-based modules increases in proportion to the square of the logarithmic mean temperature difference between the heat transfer medium oil and cooling water and attains 165 W at the logarithmic temperature difference of 180 K. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 141(1): 36–44, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10042 [ABSTRACT FROM AUTHOR]

This paper describes the evaluation results of CO2-capturing power generation systems which use solar thermal energy and gasified coal as the input energy. The following two power generation systems have been proposed and evaluated from the characteristic and economic points of view: a CO2-capturing hybrid power generation system (proposed system I), and a CO2-capturing three-stage heat-utilizing power generation system (proposed system II). In evaluation, a conventional integrated coal-gasification combined cycle power generation system (IGCC system) is adopted as the reference system. The proposed systems are assumed to be constructed in Albuquerque, U.S. and Osaka, Japan. The net coal-to-electricity efficiency has been estimated to be 51.0% for the proposed system I, and to be 40.1% for the proposed system II on higher heating value basis, whereas the efficiency of the conventional system is estimated to decrease from 43.7% to 32.7% when the CO2 generated is captured. Taking the IGCC system without CO2 capture as the reference system, the cost of CO2 emission reduction of the proposed systems I and II in Albuquerque are estimated to be 22,100–23,800 yen/t-C and 21,800–23,000 yen/t-C, respectively, and that in Osaka to be 37,000–38,700 yen/t-C and 23,300–24,500 yen/t-C, respectively. It has been shown that these are lower than the cost of CO2 emission reduction of the IGCC system with CO2 capture by 43,800–48,400 yen/t-C. © 2001 Scripta Technica, Electr Eng Jpn, 138(1): 1–13, 2002 [ABSTRACT FROM AUTHOR]

The network of Chugoku Electric Power Co. is connected to the networks of other utilities, and a fault occurring in the network may cause loss of synchronism between the group of generators belonging to the western side of the network and that of the remaining generators. In order to prevent a wide-area blackout, a power system stabilizing controller is implemented which checks the results of numerous stability calculations, selects generators to be shed for stabilization if instability is predicted, and sheds them when a fault actually occurs. This paper describes the development and application of a new approach to the construction of an external equivalent for use by power system stabilizing controllers. © 2001 Scripta Technica, Electr Eng Jpn, 134(4): 1–9, 2001 [ABSTRACT FROM AUTHOR]

In Japan, electric power utilities purchase electricity from independent power producers (IPPs) through competitive bidding; the IPP evaluation is based on the avoided costs of corresponding generators of utilities. In this evaluation, however, nonpricing factors such as power flow constraints in the electric power system cannot be considered. In this paper, we propose a new approach to evaluate economic impacts of IPPs, the IPP electricity being priced on the basis of total generating costs of the electric power utilities. Such a price to purchase the electricity of IPPs is referred to as the “break-even cost.” The main results are summarized as follows: 1) Break-even cost depends on not only the power flow constraints in the system, but also various IPP factors such as generating pattern, location, and capacity, 2) Break-even cost for the base-type IPP is higher than the avoided cost of corresponding utility generators, because IPPs located on demand sides can reduce the transmission power loss in the electric power system, 3) Break-even cost is affected by available capacity of utility generators, especially for the peak-type IPP generating only during peak demand periods. © 2000 Scripta Technica, Electr Eng Jpn, 133(2): 20–30, 2000 [ABSTRACT FROM AUTHOR]

A new gas turbine power generation system has been proposed, in which the steam (H2O) produced by utilizing waste heat from factories is used as the working fluid of gas turbine. A simulation model has been constructed to estimate power generation characteristics of the proposed system by adopting C++ language. It has been shown from simulation results that the proposed system has high exergetic efficiency, that is, the total exergetic efficiency is 46.3% and fuel-based efficiency is 56.3% for a case where steam with a temperature of 275 °C produced from a garbage incineration plant is used. Sensitivity analysis has also been carried out when usable steam temperature and pressure is changed, together with the case when condenser outlet pressure is changed. Characteristics of a dual fluid gas turbine cycle power generation system (DFGT) have also been estimated in this study. It has been shown that the proposed system has 16.9% higher exergetic efficiency and 41.8% higher fuel-base exergetic efficiency compared with DFGT. © 1999 Scripta Technica, Electr Eng Jpn, 130(1): 38–47, 2000 [ABSTRACT FROM AUTHOR]

We propose a method of single-phase PWM for an independent power supply in photovoltaic power generation systems. This new PWM is derived by comparing levels of signal waves with one of carrier waves which have bipolar swing different from unipolar swing in the conventional PWM. In this PWM, we can use a battery with lower voltage in combination with the photovoltaic power generation; fundamental level of output voltage is raised by about 11%, though poor in quality of waveforms. © 1998 Scripta Technica. Electr Eng Jpn, 122(4): 55–62, 1998 [ABSTRACT FROM AUTHOR]

Two-dimensional stability analyses for open-cycle supersonic disk MHD generators are carried out which take into account electrical boundary conditions. A method of r-θ two-dimensional linear stability analysis for supersonic disk MHD generators is proposed which examines the time growth rate of perturbations. The growth rate is determined by the characteristic equation which is derived from the electrical boundary conditions. Whether the perturbations grow or decay is judged diagrammatically in a way similar to the Nyquist method. A coal-fired outflow supersonic disk MHD generator of commercial scale is analyzed under several types of boundary conditions. The stability is much affected by the electrical boundary conditions and also by the azimuthal wavenumber of disturbances. Two-dimensional analysis has revealed an azimuthally nonuniform instability in one of the load sections of the generator, where no instability is found in the one-dimensional analysis. The analysis also shows that the instability can be suppressed by subdividing the load section with control electrodes. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 120(4): 23–30, 1997 [ABSTRACT FROM AUTHOR]

This paper proposes a new method which produces electric energy by utilizing the density difference of water by means of a “chimney effect.” The density difference of water occurs in two ways, i.e., differences of water temperature and consistency of suitable materials such as salt. For instance, water heated by solar energy is pointed out as an example of the former, while fresh water of a river versus seawater and seawater versus concentrated salt water may account for the latter. This paper also considers the three foregoing cases in a practical way. The analysis estimates that the proposed method generates energy of several hundreds or more, and ten thousands and millions of kilowatts in the respective cases. The amount of energy extracted in the third case is compared with that of the usual electric power stations using nuclear energy. The method is considered as a kind of so-called renewable energy conversion system which is free of CO2, high-energy density and is controllable. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 118 (2): 10–18, 1997 [ABSTRACT FROM AUTHOR]

This paper proposes a new electric power network that makes it possible for many types of dispersed generation plants owned by nonutility organizations to participate in an electric power market without the disadvantages of existing power utility and customers. This power network is called an open electric energy network (OEEN) because the network is open to the many types of plants for the participation. For achieving such openness, electric power storage devices, load controller at each customer and data communication network are installed in OEEN; the flow of excess electric power generated by each plant is controlled autonomously and in a distributed way. That is, the control is done by transmitting the data on excess electric power such as generation and demand point, power quality, price, etc., from each dispersed generation plant to the power storage devices and the load controllers through the communication network. Since this data-driven power flow control is similar to the mail system for a packet with the addresses of sender and receiver, it is called packet electric power transportation. In OEEN the storage device plays a different role from load leveling. Therefore, the way to determine the storage capacity differs from the conventional approach. In this paper, the applicability of queuing theory for determining the capacity is also discussed. [ABSTRACT FROM AUTHOR]

A CO-recovering hybrid power generation system utilizing thermal energy is proposed. In the system, relatively low temperature saturated steam around 220° is produced by using solar thermal energy and is utilized as the working fluid of a gas turbine in which generated CO 1 id recovered based on the oxygen combustion method. Hence solar thermal utilization efficiency is considerably higher as compared with that of conventional solar thermal power plants in which superheated steam near 400° must be produced for use as the working fluid of steam turbines; the requirement for solar radiation in the location in which the system is constructed can be significantly relaxed. The proposed system is a hybrid energy system using both the fossil fuel and solar thermal energy, thus the capacity factor of the system becomed very high. The fuel can be used exergetically in the system; i.e., it can be utilized for raising the temperature of the steam heated by utilizing the turbine exhaust gas more than 1000° The generated CO2 can be recovered by using oxygen combustion method, so that a high CO2,capturing ration of near 100. percent as well as no thermal NO, emission characteristics can be attained. It is been shown through simulation study that the proposed system has a net power generation efficiency of 63.4 percent, which is higher than 45.7 percent as compared with at that of the conventional power plant with 43.5 percent efficiency, when the amount utilized solar energy is neglected and the temperature of the saturated steam is 220° [ABSTRACT FROM AUTHOR]

This paper proposes graphical representation methods of static and dynamic characteristics of power systems. The methods use the computed results of load flow calculation and dynamic stability calculation. This work develops three kinds of representation methods using maps and animation which are sequential graphical representation of maps based on dynamic stability calculation. Conventionally the results of load flow calculation and dynamic stability calculation are represented and comprehended using load flow maps or dynamic swing curve. However, quick and effective comprehension of power system characteristics by such conventional representation methods is becoming more difficult as power systems to be analyzed are becoming larger and more complicated, especially in power systems with many loops or grids. Graphical representation using the proposed methods makes it easy to understand the static and dynamic characteristics of power systems quickly and comprehensively. In addition to these methods, this paper proposes a heuristic logic that makes it possible to draw maps automatically. It is very convenient to apply these methods to arbitrary power systems even if their constitutions or characteristics are not well known. [ABSTRACT FROM AUTHOR]

As the load in a power system continually changes, it is important to regulate the generator operating point. In this paper, assuming a suitable operating range for the generator the regulations for typical generator operating points within this range are selected and then fuzzy controllers are designed accordingly. To investigate the adaptation of each controller, many simulations are carried out for the various operating point changes. By quantitative investigation of the control performance of the adaptive controllers, a design method for fuzzy controllers for generator operating point regulation is proposed. Furthermore, a comparative estimation of the fuzzy control formula and optimal control formula with an observer is made using a common quantitative criterion. In addition, a one-machine infinite-bus system (including limits on the AVR and governor) is used as the control object model. [ABSTRACT FROM AUTHOR]

In general, electric power companies must prepare power supply capability for maximum electric load demand because it is very difficult at present to store electric power. It takes several years and requires a great amount of money to construct power generation and transmission facilities. Therefore, it is necessary to forecast long-term load demand exactly in order to plan or operate power systems efficiently. Several methods have been investigated so far for the long-term load forecasting. However, because the electric loads consist of many complex factors, good forecasting has been very difficult. This paper proposes a long-term load forecasting method using a recurrent neural network (RNN). This is a mutually connected network that has the ability of learning patterns and past records. In general, when interpolation is used for unlearned data sets, the neural network provides reasonably good outputs. However, when extrapolation is used, such as in long-term load forecasting, some kind of tunings have been necessary to obtain good results. Therefore, to solve the problem, a method is proposed in which growth rates are used as input and output data. Using the proposed method, successful results have been obtained and comparisons have been made with the conventional methods. [ABSTRACT FROM AUTHOR]

This paper investigates the voltage stability in a single OLTC (On-Load Tap Changer) system, which consists of a single OLTC and multiple generators as well as loads. It is shown that the sensitivity of the load voltage to tap position dV/dn = (I1 = exact value) plays an important role, independently of the existence of the equilibrium of the tap position. That is, when the equilibrium exists, the region where I1 > 0 is in the stability region; if the equilibrium disappears, the stability region also disappears but the voltage is still recovering in the region where I1 > 0. Based on these results, the region of reverse control action of OLTC is defined as the region where I1 < O. It is proved that another sensitivity I2, which is defined as dV/dn when constant power characteristics are assumed for loads, can be used to estimate the region of reverse control action when the exact load characteristics are not available. [ABSTRACT FROM AUTHOR]

The molten carbonate fuel cell (MCFC) power plant is expected to be one of the most promising future power generation systems for the electric utilities because of its high efficiency, environmental suitability and capability of using coal as fuel. To obtain such attractive performance, it is necessary for the plant to adopt the gas-recycling operation system. The authors tested a 6-kW class MCFC stack with three types of gas recyclings, i.e., cathode, anode and carbon dioxide ones, including pressurized conditions. This paper describes the test results and the effects of the gas-recycling operations. Cathode gas recycling is proved to be able to control the stack temperature and give the flexibility for setting oxygen utilization. Anode gas recycling is proved to be able to suppress the methane formation and decrease the deviation of the stacked cell voltages. Including the starting-up process, it is proved that the electricity can be generated from the stack without supplying carbon dioxide from outside the system by carbon dioxide gas recycling. In such a process using a burner for carbon dioxide gas recycling, burner temperature must be controlled to a certain value. It is important to adjust the fuel supplying rate, load current and cathode gas-recycling ratio to each other. At the load change process, constant gas utilization operation is not effective in change the burner temperature. [ABSTRACT FROM AUTHOR]

The future demand for electricity is uncertain and difficult to forecast, but it is necessary to do so in order to construct power plants. In that sense, a large-scale power plant is disadvantageous because it takes a long time to construct. On the other hand, although it takes less time to construct, a small-scale power plant is more expensive. Therefore large- and small-scale power plants could complement the disadvantages of each other. This paper develops a stochastic dynamic programming model to investigate the possibility. The model determines the capacities of large- and small-scale power plants in the face of uncertain demand to minimize the expected value of the total cost. Computed results have shown that small-scale plants can play a significant role in this case even if they are more expensive than large-scale plants. [ABSTRACT FROM AUTHOR]

Recently, active power filters (to be referred to as active filters in the following) using PWM inverters have attracted much attention as harmonic suppression equipment which can solve the problems of the LC filters. However, since the main circuit of the active filter requires a high-speed current response and high-accuracy frequency converter, there are problems in cost and efficiency. Accordingly, this paper proposes a harmonic suppression equipment based on a new principle, which can simultaneously solve the problems of conventional LC filters and active filters. Also, the system configuration, operation principle and control method are described, Moreover, it is clarified from both theory and experiment that excellent compensation characteristics can be obtained. [ABSTRACT FROM AUTHOR]

In this paper, we shall show the generation method of the switching patterns of the proposed PWM cycloconverter. By using these results we shall describe a control method for improving the input-output characteristics (indicating the distortions in the waveforms of the input and output voltages and currents as well as the input-to-output voltage ratio here) of the proposed PWM cycloconverter. Then, we shall show that the output current control having a good control accuracy and quick response is possible by using this control method. Also, the feasibility of the proposed control method is shown by simulation and experiment. [ABSTRACT FROM AUTHOR]

Focuses on the behavior of a high-frequency cycloconverter operating in discontinuous circulating mode and a control scheme for its circulating current. Path and modulation functions; Differences with thyristor controlled reactors; Simulation results.

Focuses on the effect of an energy storage system on the efficiency improvement of operation, consumption and transmission of electric energy, which is dependent on the generation mix and demand structure. Use of nonlinear programming to determine the best generation mix; Effects of economic characteristics of generating plants and load curve on the best generation mix.

Focuses on brushless three-phase synchronous generator without exciter. Problem associated with ac generators; Field excitation; Three-phase main winding.

Proposes a power system configuration in a power plant. Influence of load at sending terminal; Stability of the power source line; Effect of transmission distance on the stability limit.