Power System Toolbox Webpage


The purpose of this web site is to distribute three software packages for power system computation, analysis, and control:

    - PST (Power System Toolbox)

    - Power System Coherency Toolbox for the PST

    - MatNetFlow, and

    - MatNetEig

See below for information about each of these softwares.

To obtain these softwares, please review the Software Request Page.

Limited support is available from Graham Rogers, Prof. Joe H. Chow or Dr. Luigi Vanfretti.

Additional questions might be addressed to Prof. Joe H. Chow or Dr. Luigi Vanfretti.

This website is maintained by Dr. Luigi Vanfretti, along with Dr. Scott Ghiocel they handle the requests for software available in the Software Request Page.

About PST

The Power System Toolbox (PST) was conceived and initially developed by Dr. Kwok W. Cheung and Prof. Joe Chow from Rensselaer Polytechnic Institute in the early 1990s. From 1993 to 2009, it was marketed, and further developed, by Graham Rogers (formerly Cherry Tree Scientific Software), and is in use by utilities, consultants and universities world wide.

Since Graham Rogers took over the development of PST the software went under major upgrades including vectorized computations for increasing computation speed, the inclusion of additional power system components, more features for linear analysis, and other improvements.

Starting in February 2010, the PST and other software from Graham Rogers will be distributed through this webpage. Cherry Tree Scientific Software is not longer in operation.

PST consists of a set of coordinated MATLAB m-files which model the power system components necessary for power system power flow and stability studies. The toolbox comes with the m-files, demo examples of how the models can be used, several sets of dynamic data and a user's manuals.

The original paper about PST was published in the IEEE Transactions on Power Systems:

J.H. Chow and K.W. Cheung, A toolbox for power system dynamics and control engineering education and research, IEEE Transactions on Power Systems, vol.7, no.4, pp.1559-1564, Nov 1992.


PST Version 3 was developed for Graham Roger’s book:

Graham Rogers, Power System Oscillations, Kluwer Academic Publishers, 1999.


About MatNetFlow and MatNetEig

MatNetFlow and MatNetEig were developed by Graham Rogers (formerly Cherry Tree Scientific Software).


MatNetFlow is a fully featured power system load flow program which uses MATLAB as the basic computation engine. MatNetFlow may be used directly from the MATLAB command line, or through a panel based GUI. The code is supplied as a set of MATLAB m-files, which use MATLAB classes extensively. To obtain the full potential of MATLAB, the code is vectorized and sparsity is fully exploited.


MatNetEig is a MATLAB toolbox for small signal stability analysis of interconnected ac power systems. It interfaces with MatNetFlow.

MatNetEig is an object oriented program which models the following power system elements:


    -Classical - voltage behind transient reactance.

    -Subtransient - either round rotor or salient pole. Saturation is modeled on each axis in both    

    models, in the round rotor model the saturation of the d and q axis are coupled, in the salient pole

    model the saturation in the two axes are decoupled.

Excitation Systems - All IEEE standard exciter models

Governor Systems - Thermal and hydraulic governor turbine models

Induction Machines - Induction motors or generators may be modeled.


    -Static VAR Compensator

    -Thyristor Controlled Series Compensator

    -Unified Power Flow Controller: UPFC, STATCON and SECON

Active Load Modulation

Reactive Load Modulation


The network model is obtained from a solved MatNetFlow network object. MatNetFlow contains a function which outputs a linearized network admittance matrix augmented by the defined non-linear load characteristics, which is used in MatNetEig.

MatNetEig forms the sparse linearized coupled differential algebraic equations describing the systems dynamics in the frequency range of transient power system dynamics.

The functions can be called easily from the MATLAB command line, in addition a MATLAB generated GUI is available for model formulation and analysis.

For systems having up to 1000 states, it is feasible to determine a full linearized model with the network states eliminated. Model analysis may be performed using the MATLAB function eig . In this case all eigevalues and their associated left and right eigenvectors and participation vectors are determined.

Frequency response may be calculated between user selected inputs and outputs. Step responses between a single input and multiple outputs may also be calculated.

The sanity of generator data may be checked by plotting performance charts, and open circuit saturation curves.

About the Power System Coherency Toolbox (for PST)

The purpose of dynamic equivalencing is to reduce a large size power system model to a smaller one for control system design or rapid security assessment. The process of dynamic equivalencing consists of two distinct steps: 1. the identification of the coherent groups, and 2. the aggregation of the power network and the machine models.

The Power System Coherency Toolbox for the Power System Toolbox (PST), provides several functions available for each step. The user documentation is written as a tutorial tutorial discussing the use these functions to set up a reduced order model. There are dynamic aggregation examples, but these are not documented.

This toolbox was developed by Prof. Joe Chow and builds from his substantial contributions to the area of power system dynamic equivalencing.

Related work:

J. H. Chow, editor, Time-Scale Modeling of Dynamic Networks with Applications to Power Systems, Springer-Verlag, Berlin, 1982.

J. H. Chow, editor, Power System Coherency and Model Reductioin, Springer, 2013.