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This paper proposes frequency-shift acceleration control for anti-islanding of an inverter-based distributed generator. The proposed control is based on frequency positive feedback in the synchronous dq frame. Overall, the scheme of the proposed control is described. The design methodology of the frequency-shift acceleration gain is presented based on small-signal stability and step input response. The proposed control is intended for zero nondetection zone, noncompromised power quality, and easy implementation without additional devices required. Simulation and experimental results verify that the proposed anti-islanding scheme and the gain design approach are effective and useful in real applications.

This paper addresses improving the voltage stability limit of interface flow between two different regions in an electric power system using the Static Synchronous Series Compensator (SSSC). The paper presents a power flow analysis model of a SSSC, which is obtained from the injection model of a series voltage source inverter by adding the condition that the SSSC injection voltage is in quadrature with the current of the SSSC-installed transmission line. This model is implemented into the modified continuation power flow (MCPF) to investigate the effect of SSSCs on the interface flow. A methodology for determining the interface flow margin is simply briefed. As a case study, a 771-bus actual system is used to verify that SSSCs enhance the voltage stability limit of interface flow.

This paper proposes a probabilistic evaluation for the transient stability of electrical power systems incorporating FACTS devices. The uncertainties of the fault location and relay operation time play important keys in power system instability evaluation. The TCSC and SVC are employed for the reduction of system instability probability. This method is demonstrated by the WSCC test system and the results are compared with and without FACTS by means of Monte Carlo simulation.

This paper presents a new concept of reactive reserve-based contingency constrained optimal power flow (RCCOPF) for voltage stability enhancement. This concept is based on the fact that increase in reactive reserves is effective for enhancement of voltage stability margins of post-contingent states. In this paper, the proposed algorithm is applied to voltage stability margin of interface flow. Interface flow limit, in the open access environment, can be a main drawback. RCCOPF for enhancement of interface flow margin is composed of two modules, modified continuation power flow (MCPF) and optimal power flow (OPF). These modules are recursively performed until satisfying the required margin of interface flow in the given voltage stability criteria.

This paper reports a study on determining the steady-state voltage stability limit of interface flow on a set of interface lines between the metropolitan region and the neighboring regions in the Korea Electric Power Corporation (KEPCO). The interface flow limit considering severe contingencies is determined with a concept of interface flow margin, which is the active power flow margin of the key transmission lines between one region and others under a fixed load demand condition. The paper proposes a procedure to determine secure limit of active power flow on a set of specified interface lines. The procedure uses the modified continuation power flow (MCPF) tracing a path of power flow solutions with respect to generation shift to vary interface flow. In simulation, voltage stability limits of the metropolitan interface flow of the 1998 KEPCO system are determined.

In this paper, a fast contingency screening algorithm using SIME for the transient stability monitoring of the KEPCO system is implemented. This method evaluates the first-swing stability of a large number of contingencies in a short time with reliable accuracy. The salient feature of the proposed screening algorithm is as follows. First, critical cluster of generators is identified by a new index in the early stage of the time domain simulation. Thus, the computational time required for finding the equivalent one machine infinite bus system can be reduced significantly. Second, clustering critical machines can perform even in very stable cases. It allows us to avoid extra calculation of the time trajectory that is needed in the SIME for classifying the stable cases. Third, the screening capability is improved using the power-angle trajectory and subdividing the contingency classification.

A fast contingency screening algorithm using SIME for the transient stability monitoring of the KEPCO system is implemented. This method evaluates the first-swing stability of a large number of contingencies in a short time with reliable accuracy. The salient features of the proposed screening algorithm are as follows. First, a critical cluster of generators is identified by a new index in the early stage of the time domain simulation. Thus, the computational time required for finding the equivalent one machine infinite bus system can be reduced significantly. Second, clustering critical machines can perform even in very stable cases. This allows us to avoid the extra calculation of the time trajectory that is needed in the SIME for classifying the stable cases. Third, the screening capability is improved using the power-angle trajectory and subdividing the contingency classification. The test results on the KEPCO system show that the proposed method can be adopted as a contingency screening function and the transient stability assessment for the transient stability monitoring of the KEPCO system.

For any one control area, the rest of the interconnection is considered as one equivalent area. System time error and inadvertent interchange energy of an area are considered as a vector with two coordinates. This vector can be decomposed into two vector components: a component caused by the area itself, and a component caused by the rest of the interconnection.

Nathan Cohn's newly proposed technique of coordinated, system-wide correction of time error and inadvertent interchange is examined and validated by computer simulations. Area and system performances are investigated for a sudden change in load or generation in a three-area power system. The following effects are examined: changing the time of correction; simultaneous versus individual correction of time error and inadvertent interchange; the type of disturbance; the governor delay time; and the presence of sustained errors.

This paper introduces a new concept of interface flow margin in terms of steady-state voltage stability. The interface flow margin is the active power flow margin of the key transmission lines between one region and others under a fixed load demand condition. In addition, the paper proposes a technique to trace interface flow-voltage (f-V) curves by applying a continuation method. From the f-V curves, interface flow margin can be easily obtained, which is useful to determine secure flow limit of the specified interface. In the case study, illustrative examples with the New England 39-bus system and a practical 771-bus system are shown.