N. Martins

Three-phase power flow calculations using the current injection method

This paper presents a new sparse formulation for the solution of unbalanced three-phase power systems using the Newton-Raphson method. The three-phase current injection equations are written in rectangular coordinates resulting in an order 6n system of equations. The Jacobian matrix is composed of 6/spl times/6 block matrices and retains the same structure as the nodal admittance matrix. Practical distribution systems were used to test the method and to compare its robustness with that of the backward/forward sweep method.

Developments in the Newton Raphson power flow formulation based on current injections

This paper describes a sparse Newton Raphson formulation for the solution of the power flow problem, comprising 2n current injection equations written in rectangular coordinates. The Jacobian matrix has the same structure as the (2n/spl times/2n) nodal admittance matrix, in which each network branch is represented by a (2/spl times/2) block. Except for PV buses, the off-diagonal (2/spl times/2) blocks of the proposed Jacobian equations are equal to those of the nodal admittance matrix. The results presented show that the proposed method leads to a substantially faster power flow solution, when compared to the conventional Newton Raphson formulation, expressed in terms of power mismatches and written in polar coordinates.

Using a TCSC for line power scheduling and system oscillation damping-small signal and transient stability studies

This paper describes, in a tutorial manner, TCSC control aspects illustrated through simulation results on a small power system model. The analysis and design of the TCSC controls, to schedule line power and damp system oscillations, are based on modal analysis and time and frequency response techniques. Transient stability results are included, to validate and refine the TCSC controller design and protection logic under large disturbances.

An augmented Newton-Raphson power flow formulation based on current injections

This paper presents a new procedure for the solution of power flow problem, by using the current injection equations written in rectangular coordinates. From this formulation, it is possible to obtain the same convergence characteristics of the conventional power flow expressed in terms of power mismatches and written in polar coordinates. By using this methodology, a highly sparse augmented formulation suited to the incorporation of FACTS devices and control of any kind is also obtained. The results presented validate the proposed method.

Improved representation of control adjustments into the Newton -Raphson power flow

Abstract This paper describes a sparse (4 n ×4 n ) formulation for the solution of power flow problem, comprising 2 n current injection equations written in rectangular coordinates plus the set of control equations. This formulation has the same convergence characteristics of the conventional Newton power flow problem, expressed in terms of power mismatches written in polar coordinates and can be reduced to a (2 n ×2 n ) formulation plus the control equations. It is best suited to the incorporation of flexible AC transmission system devices and controls of any kind. Complex user-defined control functions, involving the participation of several regulating devices, can be directly introduced as power flow control data. The results presented validate the proposed method.

Redispatch to Reduce Rotor Shaft Impacts Upon Transmission Loop Closure

This paper describes a novel generation rescheduling method to reduce the generator rotor shaft impacts induced by transmission loop closures. The rotor shaft impact constraints, at the instant of transmission loop closure, are explicitly modeled into an interior point optimal power flow. This method represents a considerable improvement on the conventional redispatch for reducing the standing phase angle of the closing breaker. Optimal power flow and transient stability results are provided for a tutorial four-bus and the IEEE 118-bus test systems.

Reducing standing phase angles via interior point optimum power flow for improved system restoration

Maximum limits for standing phase angles (SPA) must be imposed upon network loop closure, during the transmission system restoration process. These limits reduce the risk of damage in generation and transmission equipment. This paper presents an interior point optimum power flow (OPF) tool, whose objective function to be minimized is the deviation of active power generation and/or load shedding. The maximum limits of SPA are modeled as additional constraints. A practical restoration problem in one large area of the Brazilian interconnected system was analyzed and the results indicated the effectiveness of the proposed technique.

An Optimal Power Flow Function to Aid Restoration Studies of Long Transmission Segments

This paper presents an optimal power flow function for aiding restoration studies of subsystems having long transmission segments. The method simultaneously computes an optimal set of variables which are critical for the subsystem restoration: the generation power plant high-side voltage, the minimum shunt reactor configuration and the maximum load to be safely energized. A set of overvoltage restoration scenarios following load rejection is constructed in such a way that the computed shunt reactor compensation becomes distributed along the transmission corridor. The whole problem is formulated as a single optimization problem whose solution is obtained by an optimal power flow, based on the Primal-Dual Interior Point Method. The described results for a restoration study on a system from practice confirm the effectiveness of the proposed method.

Some recent developments in small-signal stability and control

This paper describes recent work on power system small-signal stability, control applications and harmonic analysis carried out by CEPEL, Brazil. It describes developments carried out in CEPEL and related to the modal analysis of power system models.

Advanced SVC models for Newton-Raphson load flow and Newton optimal power flow studies [discussion and closure]

Two sets of authors provide separate comments on the paper by H. Ambriz-Perez et al. (see ibid., vol.15, no.1, p.129-36, 2000). The original authors reply to the comments.