System and method of loadflow calculation for electrical power system

• US 8,315,742 B2
• Filed: 08/27/2007
• Issued: 11/20/2012
• Est. Priority Date: 08/27/2007
• Status: Expired due to Fees

• Current Assignee: Sureshchandra Patel
• Original Assignee: Sureshchandra Patel
• Inventors: Patel, Sureshchandra
• Primary Examiner(s): HARTMAN JR, RONALD D
• Application Number:
  US12/310,433
• Publication Number:
  US 20120089264A1
• Time in Patent Office: 1,912 Days
• Field of Search: 700/286, 700/291, 700/295, 700/297, 700/298
• US Class Current: 700/286
• CPC Class Codes: H02J 2203/20 Simulating, e g planning, reliability check, modelling or computer assisted design [CAD]
• CPC Class Codes: H02J 3/00 Circuit arrangements for ac mains or ac distribution networks
• CPC Class Codes: H02P 9/10 Control effected upon generator excitation circuit to reduce harmful effects of overloads or transients, e.g. sudden application of load, sudden removal of load, sudden change of load
• CPC Class Codes: Y02E 60/00 Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
• CPC Class Codes: Y04S 40/20 Information technology specific aspects, e.g. CAD, simulation, modelling, system security

Abstract

A method of performing loadflow computations for controlling voltages and power flow in a power network by reading on-line data of given/specified/scheduled/set network variables/parameters and using control means, so that no component of the power network is overloaded as well as there is no over/under voltage at any nodes in the network following a small or large disturbances. A loadflow computation method could be any method including invented Patel Decoupled Loadflow (PDL) method, and Decoupled Gauss-Seidel-Patel Loadflow (DGSPL) method. The invented Patel Decoupled Loadflow (PDL) calculation method is characterized in 1) the use of the same coefficient matrix [GB] for both the p-f and q-e sub-problems of the loadflow computation; 2) almost no effort in the modified mismatch calculations in the iteration process; and 3) all the nodes in both the sub-problems being active, no refactorization of [GB] required for implementation of Q-limit violations. These features make the invented PDL method computationally almost two times more efficient than the current state-of-the-art Super Super Decoupled Loadflow (SSDL) method. The invented DGSPL calculation method is characterized in decoupling the calculation of real and imaginary components of complex node voltage leading to increased stability and efficiency of the DGSPL calculation method.

Claims

1. A method of forming/defining and solving a loadflow computation model of a power network to affect control of voltages and power flows in a power system, comprising the steps of:

obtaining on-line or simulated data of open/close status of all switches and circuit breakers in the power network, and reading data of operating limits of components of the power network including maximum power carrying capability limits of transmission lines, transformers, and 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,

performing loadflow computation by forming and solving a loadflow model of the power network to calculate complex voltages or their real and imaginary components or voltage magnitude corrections and voltage angle corrections at the power network nodes providing for the calculation of power flowing through different network components, and reactive power generation at PV-nodes, and turns ratio of tap-changing transformers in dependence the set of said obtained-online readings, or given/scheduled/specified/set values of controlled variables/parameters and physical limits of operation of the power network components,

forming and solving the said loadflow model of the power network referred to as Patel Decoupled Loadflow (PDL) model as characterized by equations,

[RP]=[GB][f] 

 

(51)

[RQ]=[GB][e] 

 

(52)

wherein, each component of [RP], [RQ], and [GB] are defined by,

3. The method of forming/defining and solving a loadflow computation model of a power network to affect control of voltages and power flows in a power system as defined in claim 1 is the method that organizes a set of nonlinear algebraic equations in linear form as a product of coefficient matrix and unknown vector on one side of the matrix equation and all the other terms on the other side as known vector, and then solving the linear matrix equation for unknown vector in an iterative fashion.

2. A method of forming/defining and solving a loadflow computation model of a power network to affect control of voltages and power flows in a power system, comprising the steps of:

obtaining on-line or simulated data of open/close status of all switches and circuit breakers in the power network, and reading data of operating limits of components of the power network including maximum power carrying capability limits of transmission lines, transformers, and 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,

performing loadflow computation by forming and solving a loadflow model of the power network to calculate complex voltages or their real and imaginary components or voltage magnitude corrections and voltage angle corrections at the power network nodes providing for the calculation of power flowing through different network components, and reactive power generation at PV-nodes, and turns ratio of tap-changing transformers in dependence the set of said obtained-online readings, or given/scheduled/specified/set values of controlled variables/parameters and physical limits of operation of the power network components,

forming and solving the said loadflow model of the power network referred to as Decoupled Gauss-Seidel-Patel Loadflow (DGSPL) model as characterized by equations,