From Forbidden States to Linear Constraints
This paper deals with the problem of constructing
constraints in non safe Petri Nets and then reducing the number of the
constructed constraints. In a system, assigning some linear constraints
to forbidden states is possible. Enforcing these constraints on the
system prevents it from entering these states. But there is no a
systematic method for assigning constraints to forbidden states in non
safe Petri Nets. In this paper a useful method is proposed for
constructing constraints in non safe Petri Nets. But when the number of these constraints is large enforcing them on the system may complicate the Petri Net model. So, another method is proposed for reducing the number of constructed constraints.
discrete event system, Supervisory control, Petri Net, Constraint
Fail-safe Modeling of Discrete Event Systems using Petri Nets
In this paper the effect of faults in the elements and
parts of discrete event systems is investigated. In the occurrence of
faults, some states of the system must be changed and some of them
must be forbidden. For this goal, different states of these elements are
examined and a model for fail-safe behavior of each state is
introduced. Replacing new models of the target elements in the
preliminary model by a systematic method, leads to a fail-safe
discrete event system.
Discrete event systems, Fail-safe, Petri nets,
Reducing the Number of Constraints in Non Safe Petri Net
This paper addresses the problem of forbidden states in
non safe Petri Nets. In the system, for preventing it from entering the
forbidden states, some linear constraints can be assigned to them.
Then these constraints can be enforced on the system using control
places. But when the number of constraints in the system is large, a
large number of control places must be added to the model of system.
This concept complicates the model of system. There are some
methods for reducing the number of constraints in safe Petri Nets.
But there is no a systematic method for non safe Petri Nets. In this
paper we propose a method for reducing the number of constraints in
non safe Petri Nets which is based on solving an integer linear
discrete event system, Supervisory control, Petri Net,
Two Area Power Systems Economic Dispatch Problem Solving Considering Transmission Capacity Constraints
This paper describes an efficient and practical method
for economic dispatch problem in one and two area electrical power
systems with considering the constraint of the tie transmission line
capacity constraint. Direct search method (DSM) is used with some
equality and inequality constraints of the production units with any
kind of fuel cost function. By this method, it is possible to use several
inequality constraints without having difficulty for complex cost
functions or in the case of unavailability of the cost function
derivative. To minimize the number of total iterations in searching,
process multi-level convergence is incorporated in the DSM.
Enhanced direct search method (EDSM) for two area power system
will be investigated. The initial calculation step size that causes less
iterations and then less calculation time is presented. Effect of the
transmission tie line capacity, between areas, on economic dispatch
problem and on total generation cost will be studied; line
compensation and active power with reactive power dispatch are
proposed to overcome the high generation costs for this multi-area
Economic dispatch, Power System Operation, Direct
Search Method, Transmission Capacity Constraint.