The accuracy of the load model has great effects on power system stability analysis and control. Based on our practice in China on modeling load from field measurements, this paper systematically develops a measurement-based composite load model. Principles guiding the load modeling practice are discussed based on detailed analysis on stochastic characteristics of the modeling procedure. The structure of the measurement-based composite load model is presented. A multicurve identification technique is described to derive parameters. The generalization capability of this built load model is also investigated in this paper. Two cases are studied to illustrate the accuracy of the developed load model on describing the load dynamic characteristics in the actual power system.

Composite load modeling via measurement approach

Accurate load modeling is essential for power system dynamic simulation. In this paper, four dynamic load models are identified based on multiple online measurement data from the Taiwan Power System. The performances in modeling real and reactive power behaviors by dynamic and selected static load models are evaluated. Parameter variation with respect to different loading conditions is analyzed. A simple and efficient method is presented to estimate a representative parameter set for different loading conditions. The cross-validation technique is applied to validate the four dynamic load models in order to obtain a better estimate of their performance. Numerical studies indicate that linear dynamic load models studied in this paper give better results than two nonlinear dynamic load models in modeling reactive power behaviors during disturbance while they are comparable in modeling real power behaviors

Measurement-based dynamic load models: derivation, comparison, and validation

This paper considers the significance of load voltage dynamics in studies of power system damping. A generic model of dynamic loads is used to investigate the influence of active and reactive power dynamics on the damping of oscillations in a multimachine power system. The interaction between the load and the power system is explored in terms of load and system transfer functions. It is shown that the power system transfer function is composed of a static part and a dynamic part. The static part is derived from the power flow Jacobian. The investigations indicate that load voltage dynamics can significantly influence the damping of modal oscillations. Static load models can give quite misleading predictions of damping when loads actually exhibit dynamic behaviour.

Load modelling in studies of power system damping

CIGRE WG C4.605 : “Modelling and aggregation of loads in flexible power networks”

Load model is one of the most important elements in power system simulation and control. Based on more than 20 years of practice using load characteristic recorders in the measurement-based load modeling, this paper proposes the expectation composite load model to predict unseen data. The methods for load bus classification and parameter identification are also provided. The generalization capability of the proposed load modeling is validated by the measured load dynamics and system dynamics during two three-phase short circuit tests of the NE power grid in China. In order to evaluate the measurement-based load model, the probabilistic collocation method (PCM) is applied to quantitatively analyze uncertainties of the simulation responses raised by the parameters.

A Real Application of Measurement-Based Load Modeling in Large-Scale Power Grids and its Validation

Accurate dynamic load models allow more precise calculations of power system controls and stability limits, which are critical in the planning and operation of power systems. The development of dynamic load models using the measurement approach for the Taipower system are described. Two dynamic load model structures are developed. A procedure for applying a set of measured data from an online transient recording system to develop dynamic load models for the Taipower system is described. A technique based on the concept of confidence interval is used to validate the developed high-order load model structure. Case studies are also presented. >

Dynamic load models in power systems using the measurement approach

A personal-computer-based plant transient recording and analysis (PTRA) system has been developed under a joint effort between the system planning department of Taiwan Power Company (TPC) and A-D Technology, Inc. The PTRA system is an integrated hardware and software computer system to collect the high resolution data of a power plant's transient conditions. The hardware of the PTRA system consists of Intel 80386-based personal computers, an intelligent data acquisition system, resistor boards, and data communication equipment. Special software modules were developed for the hardware to perform data monitoring, trigger detection, data collection, data transmission, and data analysis. The PTRA system has proved to be effective, accurate, flexible, and easy-to-use. It reveals high potential for various applications on electrical generation and transmission systems. >

A.Y.-T. Chen

Papers

Dynamic load models in power systems using the measurement approach

A powerful personal computer-based plant transient recording and analysis system