Modified Continuation Power Flow Research Articles

Analysis of overvoltage reactive power margin for future power systems with renewable energy generation

As modern power systems continue to adopt wide usage of Renewable Energy (RE) sources, the reliance on conventional generators is slowly reducing. Countries are adopting new energy policies to speed up the transition of future power systems to a fully renewable and clean system, and this is centered around the increase of RE penetration to reduce carbon emissions. However, it is expected that this transition will be met with stability issues due to the intermittent nature of REs and reduction of conventional generators. In recognition of these expected complications for the future systems, an analysis method is proposed in this paper to identify critical buses in terms of voltage stability for power systems with high RE penetration level. A new method that utilizes both modified continuation power flow and Q-V analysis to determine acceptable reactive power margins for each bus considering the intermittency of RE sources is presented in this study. This work is focused on the future Korea Power Systems with 16.05 GW of renewable energy. Considering different RE levels and loading conditions, several scenarios are studied to identify the voltage stability in the different Korea regions with a high penetration of RE. The resulting reactive power margins can be used to prevent overvoltage through the identification of weak and vulnerable buses for the future power systems.

Improvement of the line losses, weaker buses and saddle-node-bifurcation points using reconfigurations of the identified suitable lines

For the planning, operation and design of the modern power systems, the effect of the network reconfiguration of the identified weaker lines are nowadays investigated. Gradually increasing the load, saddle-node bifurcation (SNB) is determined using modified continuation power flow (MCPF) algorithm. Judging three different sets of the security limits, the weaker buses are detected from the power flow solution at the SNB point. The three different reconfigurations are implemented on the identified weaker lines for the standard IEEE-14, 30 and 57-bus test systems separately. The optimal location and the suitable lines for the reconfiguration are demonstrated with the results. Using the network reconfiguration, the significant improvement of the SNB points or load margin, weaker buses, voltage profile, line losses for the different cases are proved showing results.

A directional control method for interface flow considering static voltage stability

A directional control method (DCM) for power flows on a set of interface lines between two regions of power system considering static voltage stability margin is developed in this paper. A surface approximation approach is firstly used to obtain the relationship between the interface flow solution and the generation direction of generator (the portion of generation variation in each participating generator to satisfy the desired power increase on the interface and the system loss). Then, an optimization model is built to determine the optimum dispatching scheme of generators. This method not only can control the total power on the interface to satisfy the power demand but also can realize the directional control of power on each interface line based on the needs of operation. The proposed DCM is further extended to determine the optimum dispatching scheme of generators for maximizing the interface flow margin (IFM), which is the active power margin of the key transmission lines between two regions of power system constrained by static voltage stability. A modified continuation power flow (MCPF) is used to show and evaluate the impacts of the DCM on the IFM. The New England 39-bus system and the IEEE 300-bus system have been employed to verify the effectiveness of the DCM.

Enhancement of Interface Flow Limit using Static Synchronous Series Compensators

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.

Reactive reserve-based contingency constrained optimal power flow (RCCOPF) for enhancement of voltage stability margins

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.

A Study on Determination of Interface Flow Limits in the KEPCO System Using Modified Continuation Power Flow (MCPF)

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.

A study on determination of interface flow limits in the KEPCO system using modified continuation power flow (MCPF)

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.

A Study on Determination of Interface Flow Limits in the KEPCO System Using Modified Continuation Power Flow (MCPF)

A Study on Determination of Interface Flow Limits in the KEPCO System Using Modified Continuation Power Flow (MCPF)

Determination of interface flow margin using the modified continuation power flow in voltage stability analysis

A new concept of interface flow margin in terms of steady-state voltage stability is introduced. 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, a technique is proposed to trace interface flow-voltage (f-V) curves by applying a continuation method. From the f-V curves, the interface flow margin can be easily obtained, which is useful to determine the secure flow limit of the specified interface. In the case study, an illustrative example with the New England 39-bus system is shown.