32 results about "Superposition theorem" patented technology

The invention discloses an equivalent three-phase short circuit calculation method which considers an outer network ground branch circuit and sensitivity information. Firstly, whole-network basic data including system element parameters, a topology structure and a trend calculation result under a normal running condition is input, then based on a sensitivity consistency equivalent method, an equivalent network is constructed, through a sensitivity weighing method, ground branch circuit admittance parameters are deducted, and according to trend, sensitivity and power transfer characteristic consistency, other parameters are solved. Finally, an improved equivalent method is applied to three-phase short circuit calculation, through the adoption of a node impedance method and a superposition theorem and based on the trend calculation result, a short circuit point current under a three-phase short circuit fault of an inner network, all node short circuit voltages and all branch circuit short circuit currents are calculated.

The invention belongs to the technical field of stability analysis of power systems and particularly relates to a position function-based out-of-step and oscillation center positioning and migration tracking system and method under multi-frequency oscillation. The method comprises the steps of connecting power supplies at three sides to a point through three lines to build a three-machine equivalent system model; obtaining a voltage vector expression of any point under the simultaneous action of the power supplies at three sides according to a superposition theorem; setting position functionsof oscillation centers according to line impedance ratios; rewriting the voltage vector expression of any point into a form of modulus and phase, expanding the expression into a quadratic function, calculating a partial derivative and then obtaining an expression of the position of the oscillation center at any side according to a trigonometric function relationship and a mean value inequality; and analyzing the influences of three factors, namely relative power angles of systems, impedance structure parameters and power supply voltage amplitudes of the systems on the oscillation centers, obtaining conditions of appearing of an out-of-step center at various sides, obtaining a criterion according to the trigonometric function relationship of one voltage vector and then determining the position of the out-of-step center.