The Technical Committee (TC) of the Institute of Electrical Engineers of Japan (IEEJ) is putting a great deal of effort into producing power system standard models for the purpose of providing power system engineers with a common starting point. TC has already overseen the development of two categories of standard models. One is a set of 4 types of standard bulk-transmission network models, and the other is a set of 3 types of standard sub-transmission network models. This paper describes two additional activities of TC. One is expanding these models and the other one is developing data of new models. In the expansion activities, TC held several seminars for power system engineers to describe the basic ideas behind these system models, their features, and examples of using these models. In the development activities, TC developed data for studying the optimal power flow and voltage stability analysis (EAST/WEST 10-machine system models of IEEJ). The data of these all models can be download from IEEJ Power and Energy Society's homepage (http://www.iee.or.jp/pes/).
Because of the introduction of deregulation and competition in the electricity supply industry, large number of IPPs (Independent Power Producers) will get into the market. It has become much more important to able to determine which generators are supplying a particular load, which generator is making of a transmission line congestion and what is each generators contribution to the system losses. In this paper, we propose the way to calculate these contributions automatically. The applicability of the proposed technique is demonstrated using the EastlO 47 buses power system.
Transient stability constrained optimal power flow (SCOFF) has been recognized as a potentially mighty tool for secure and optimal operation planning of power systems since its advent, especially in nowadays open transmission access environment. However, although a lot of works have been done regarding this attractive topic, no SCOPF with multi-contingency has been reported until now. In this paper, first, the necessity for multi-contingency SCOPF (MC-SCOPF) is illustrated based on the results of the IEEJ WEST10 model system. Then MC-SCOPF problem is formulated and a solution method is proposed. Computation results on the IEEJ WEST10 model system demonstrate the effectiveness of the presented MC-SCOPF formulation and the efficiency of the proposed calculation approach.
This paper presents a method for Parameterized Contingency Constrained Optimal Power Flow (PCCOPF) whose formulation can discriminate unpreventable contingencies, determine the existence of feasible solutions for post contingencies and analyze the feasible solution for the contingencies in terms of static sense. The proposed formulation is based on parameterized contingency constraints in which each contingency parameter represents the achievement ratio of each selected contingency. In the formulation, not only parameterized contingency constraints are given by a set of equality constraints which is modified power flow equations, but also the objective is maximization of the'sum of the achievement ratios of selected contingencies. Since contingency parameters are treated as decision variables in the proposed method, the information on unsolvability with respect to each contingency can be efficiently obtained. The feasibility and effectiveness of the proposed method are demonstrated on test problems with 4-bus and 71-bus systems.
To make more use of existing electric power transmission facilities, security assessment utilizing on-line data is thought to be one of the effective measures that can be taken. To realize on-line assessment of post-fault small signal stability for a number of supposed contingencies, it is effective to pick out severe contingencies to be analyzed with precise assessment program, e.g. S-method. We developed contingency selection method that has two indexes for selection. One of the indexes is post-fault eigenvalue estimation based on 2nd approximation of eigenvalue change for system matrix change, which is effective for relatively weak non-linear eigenvalue change. The other one is Non-linearity Index that indicates the strength of non-linearity of eigenvalue change. It is effective to detect the strong non-linear eigenvalue change that can not be estimated correctly by the 2nd approximation estimation. Calculation results with IEEJ Bulk Power System Models show that the proposed method can effectively decrease the number of contingencies that have to be analyzed with precise Small Signal Stability Analysis method.
Unit commitment problem is an optimization problem to determine the start-up and shut-down schedule of thermal units while satisfying various constraints, for example, generation-demand balance, unit minimum-up/down time, system reserve and so on. Since this problem involves a large number of 0-1 type variables that represent up/down status of the unit and continuous variables expressing generation output, it is one of the difficult combinatorial optimization problems to solve. The study at present is groping the method for requiring the sub-optimum solution efficiently. Unit commitment method widely used solves the problem without consideration of voltage, reactive power and transmission constraints. In this paper, we will propose a solution of unit commitment with voltage and transmission constraints, based on the unit decommitment procedure (UDP) method, heuristic method and optimal power flow (OPF). In this method, initial unit status will be determined from random numbers and the feasibility will be checked for minimum start-up/shut-down time and demand-generation balance. If the solution is infeasible, the initial solution will be regenerated until a feasible solution can be found. Next, OPF is applied for each time period with the temporary unit status. Then, the units that have less contribution to the cost are detected and will be shutdown based on the unit decommitment rules. This process will be repeated until sub-optimal solution is obtained. The proposed method has been applied to the IEEE 118-bus test system with 36 generating units with successful result.
Power systems have become larger and more complex because of the increase of the electric power demand, and the analysis of power systems requires heavier computation than before. On the other hand, the social dependence on electric power is increasing, and thus the influence of outages in power systems is becoming more crucial. Therefore on-line preventive control is more important than ever. In this paper, we propose a generation rescheduling method for transient stability preventive control. First we check all contingencies in the decreasing order of their severities by sorting them in the increasing order of their critical clearing times (CCTs) computed by the dynamic extended equal-area criterion. Second we select several contingencies among them as objects of consideration, and compute generation rescheduling amounts using rotor angles of some machines at an appropriate time and the linear relationship between CCTs and outputs of the most critical machine. To investigate the validity of the proposed method, a demonstrative example is shown using the IEEJ EAST 10-machine system.
System stability and protection from any disturbances are significant issues in a recent power system especially in a deregulated power system. In this paper a Superconducting Fault Current Limiter (SFCL) assembled with a series damping resistor is investigated as a powerful controller for the transient stability enhancement of power systems. The application of series damping resistor controlled by SFCL combined with a Superconducting Magnetic Energy Storage (SMES) for power system stabilization is proposed and the effectiveness is investigated in detail. The SFCL with a series damping resistor is capable of absorbing the accelerating power of generator effectively, by which the capacity of SMES is significantly reduced. As a result, the power system dynamic stability as well as the transient stability has been effectively enhanced by the SMES with SFCL.
This paper discusses about the voltage harmonics generated from the multiple connected voltage source type self commutated converter, which is switched with PWM (Pulse Width Modulation) signal generated by comparing sinusoidal signal wave with triangle carrier wave. The conventional harmonics analysis of the multiple connected converters directly calculates Fourier coefficients to the output waveform. This paper formularized the harmonics component of single converter in convenient expression for the analysis of multiple connected converters with using multiple Fourier transform. The obtained equations not only can give harmonics of the multiple connected converters with easily, but also can give index to determine the suitable settings of the PWM carrier for harmonics reduction. The theoretical designing of the harmonics reduction of the converter output is confirmed through EMTP simulations.
Lightning observations have been made to study the lightning phenomena on UHV designed transmission line. And many shielding failures not to be predicted by the conventional shielding theory have been observed. This paper describes the study of lightning-surge overvoltages at substations caused by direct lightning strokes to phase conductors on transmission lines. The overvoltages were evaluated to compare with the overvoltages due to back flashover and the lightning impulse withstand voltage. The direct lightning current used for the calculation was set up by the analysis of a result of observation. And, this report explains effects of capacitance of a transformer and an arrester upon overvoltages at a primary terminal of a transformer. Transient calculations were performed by the EMTP.
Grounding resistance of a transmission tower in Japan is commonly required to be less than 10 ohm to avoid lightning back flashover accident. However, it takes huge amount of cost to improve the resistance to the recommended value especially in the mountainous region. In order to reduce the cost of these works, the authors have investigated on flashover simulation with various grounding conditions. The paper deals with experimental results on grounding resistance of an actual 500-kV transmission tower footing and its downsized models. After brief review of necessity and scaling rule of the downsizing, we discuss dynamic characteristic of grounding resistance imposing very large current of 30kA.
This paper proposes a new semiconducting-type fault current limiter(FCL) using the digital signal processor(DSP) to improve the instantaneous voltage drop and to reduce the falut cureent of power system. The proposed FCL used a insulated gate bipolar transistor (IGBT) as a commutation element. Next, the DSP is used in proposed FCL in order to detect the fault current at high speed. The examination was carried out using equipment of small capacity in order to demonstrate the effectiveness of the proposal technique.