Patent ID: 7788051
Filing Date: 2010-08-31
Classification: G06Q,H02J,Y02E,Y04S

Abstract:
1. A method of forming/defining and solving a model of a power network to affect control of voltages and power flows in a power system, comprising the steps of: obtaining on-line/simulated data of open/close status of switches and circuit breakers in the power network, and reading data of operating limits of components of the power network including PV-node, a generator-node where Real-Power-P and Voltage-Magnitude-V are given/assigned/specified/set, maximum and minimum reactive power generation capability limits of generators, and transformers tap position limits, obtaining on-line readings of given/assigned/specified/set Real-Power-P and Reactive-Power-Q at PQ-nodes, Real-Power-P and voltage-magnitude-V at PV-nodes, voltage magnitude and angle at a reference/slack node, and transformer turns ratios, wherein said on-line readings are the controlled variables/parameters, initiating loadflow computation with initial approximate/guess solution of the same voltage magnitude and angle as those of the reference/slack node for all the PQ-nodes and the PV-nodes, said initial approximate/guess solution is referred to as a slack-start, performing loadflow computation to calculate complex voltages or their real and imaginary components or voltage magnitude corrections and voltage angle corrections at nodes of the power network providing for calculation of power flow through different components of the power network, and to calculate reactive power generation and transformer tap-position indications, decomposing the power network for performing said loadflow computation in parallel by a method referred to as Suresh's diakoptics that involves determining a sub-network for each node involving directly connected nodes referred to as level-1 nodes and directly connected nodes to level-1 nodes referred to as level-2 nodes, and a level of outward connectivity for local solution of a sub-power-network around a given node is determined experimentally, initializing, at the beginning of each new iteration, a vector of dimension equal to the number of nodes in the power network with each element value zero, solving all sub-networks in parallel using available solution estimate at the start of the iteration, adding newly calculated solution estimates or corrections to the available solution estimate for a node resulting from different sub-networks, ‘q’ number of sub-networks, in which a node is contained, in a corresponding vector element that gets initialized zero at the beginning of each new iteration, counting the number of additions and calculating new solution estimate or corrections to the available solution estimate by taking the average or root mean square value using any relevant relations (30) to (39) in the following depending on the loadflow computation method used, and storing the new solution estimate at the end of the current iteration as initial available estimate for the next iteration, wherein said Suresh's diakoptics method uses the following relations, wherein relations (30) to (34), can also alternatively be written as relations (35) to (39) as below, wherein, square of any positive or negative number being positive, if the original not-squared value of any number is negative, the same algebraic sign is attached after squaring that number, and if the mean of squared values turns out to be a negative number, negative sign is attached after taking the square root of the unsigned number, V evaluating loadflow computation for any over loaded components of the power network and for under/over voltage at any of the nodes of the power network, correcting one or more controlled parameters and repeating the performing loadflow computation by decomposing, initializing, solving, adding, counting, storing, evaluating, and correcting steps until evaluating step finds no over loaded components and no under/over voltages in the power network, and affecting a change in power flow through components of the power network and voltage magnitudes and angles at the nodes of the power network by actually implementing the finally obtained values of controlled variables/parameters after evaluating step finds a good power system or alternatively the power network without any overloaded components and under/over voltages, which finally obtained controlled variables/parameters however are stored for acting upon fast in case a simulated event actually occurs.