Wojtek Kolodziej

Bang-bang series capacitor transient stability control

The design of a series capacitor bang-bang control for the transient stabilization of interconnected power systems is presented. First, a time-optimal switching policy is fully characterized for the second order swing equation. Next, the switching policy is modified to provide a robust transient stability control for the interconnected power systems. A relay-based controller is proposed, and its implementation is discussed. A simulation example illustrates the design concepts of the proposed transient stability control. >

An application study for sizing and rating controlled and conventional series compensation

A step by step method for determining controlled and conventional series compensation requirements is developed. The Montana 500 kV transmission system is taken as an example in this study. A base transfer rating of 2200 MW for the system already exists, and it is assumed that as its power loading increases, controlled series compensation is needed to reinforce the system. Combination of conventional and thyristor-controlled series compensators (TCSCs) is considered as a means of increasing the system transfer capability. Powerflow and transient stability studies are performed to rate and size the series compensators. The TCSC reactance control capabilities are established for steady-state and transient conditions. An installation sequence is developed relating facility requirements to system loading.

Robust transient stability control using thyristor-controlled series compensation

This paper presents an example of a thyristor-controlled series compensator (TCSC) application for transient stability enhancement of the Montana power system. TCSC capability characteristics are established based on the device current ratings and capacitor ohmic size, and next used in transient stability studies. A transient stability controller is designed to maximize the TCSC effectiveness for the first swing stability enhancement. The concepts of operating and restraint characteristics are presented, and a robust control law is proposed. Transient stability studies are performed for the Montana system, and the benefits of applying the TCSC for the stability enhancement are demonstrated. Design and performance of the TCSC-based transient stability controller are presented.

Design of a guided-asynchronous graduate course in multimedia signal processing

This paper describes the design of a new guided-asynchronous graduate course in multimedia signal processing (MMSP). MMSP expertise is increasingly critical for many working engineers from diverse disciplines. Targeted students have some prior DSP-related experience, but need an introduction to MMSP fundamentals before participating in more specialized courses. A modular structure, asynchronous design and application focus are used to meet the educational and logistical needs of working engineers. Industry and university partners use MMSP technologies to provide remote access to pre-configured laboratory experiments and educational resources, and support for distributed collaboration and guided learning. Thus hands-on experience with MMSP technologies is integrated with learning about underlying MMSP concepts. A central element of the course design are on-line, multimedia topical learning modules which provide evaluation of student level of expertise, guidance in choosing course activities to effectively meet learning goals, student practice and projects, and feedback and evaluation of student performance.

Interconnections between continuous and discrete games with applications to H/sup infinity /

This study establishes some interesting interconnections between continuous- and discrete-time H/sup infinity / problems. The approach highlights the similarities and differences and reveals that the discrete-time problem has a significantly richer structure. Also, all continuous-time results given here can be obtained from the (more complex) discrete-time results by letting Delta =0. This fact is a consequence of the formulation of the discrete case using the unified approach to the H/sup infinity / disturbance rejection problem, set up in the framework of linear quadratic game theory.<<ETX>>

Stochastic Dynamic System Suboptimal Control with Uncertain Parameters

The control of a linear system with random coefficients is studied here. The cost function is of a quadratic form and the random coefficients are assumed to be partially observable by the controller. By means of the stochastic Bellman equation, the optimal control of stochastic dynamic models with partially observable coefficients is derived. The optimal control is shown to be a linear function of the observable states and a nonlinear function of random parameters. The theory is applied to an optimal control design of an aircraft landing in wind gust.

Sensitive-cell-based fish chromatophore biosensor

A sensitive biosensor (cytosensor) has been developed based on color changes in the toxin-sensitive colored living cells of fish. These chromatophores are highly sensitive to the presence of many known and unknown toxins produced by microbial pathogens and undergo visible color changes in a dose-dependent manner. The chromatophores are immobilized and maintained in a viable state while potential pathogens multiply and fish cell-microbe interactions are monitored. Low power LED lighting is used to illuminate the chromatophores which are magnified using standard optical lenses and imaged onto a CCD array. Reaction to toxins is detected by observing changes is the total area of color in the cells. These fish chromatophores are quite sensitive to cholera toxin, Staphococcus alpha toxin, and Bordatella pertussis toxin. Numerous other toxic chemical and biological agents besides bacterial toxins also cause readily detectable color effects in chromatophores. The ability of the chromatophore cell-based biosensor to distinguish between different bacterial pathogens was examined. Toxin producing strains of Salmonella enteritis, Vibrio parahaemolyticus, and Bacillus cereus induced movement of pigmented organelles in the chromatophore cells and this movement was measured by changes in the optical density over time. Each bacterial pathogen elicited this measurable response in a distinctive and signature fashion. These results suggest a chromatophore cell-based biosensor assay may be applicable for the detection and identification of virulence activities associated with certain air-, food-, and water-borne bacterial pathogens.

Application of hierarchical neural-network-based control to transient stabilization of interconnected power systems

Flexible AC Transmission Systems (FACTS) research is aimed at increasing transmission capabilities of existing power systems. FACTS devices provide means to dynamically control parameters of the transmission lines. In particular thyristor-controlled series capacitors have been proposed to increase inter-area transient stability margins. Design of a suitable control algorithm for adjusting capacitor compensation level is a challenging task. The power system dynamics, particularly during transients caused by severe faults, are highly nonlinear. A series capacitor affects the system dynamics in nonlinear fashion, further increasing the difficulty of applying traditional linear control. There is also an inherent system uncertainty due to fluctuations of operating conditions and to sudden structural changes caused by faults. A successful controller should be robust with respect to these uncertainties and must accommodate the nonlinear dynamics of the system. The above issues are addressed here using neural-network methodology.<<ETX>>

Robust control for transient stabilization of interconnected power systems

Methodology of robust controller design for transient stabilization of the interconnected power systems is presented. The model of the interconnected power systems for braking resistor control is derived, and a PID controller is proposed to control the amount of power dissipated by the brake. The Kharitonov approach is used for an initial tuning of the controller gains. Next, transient energy functions are applied for final controller tuning and choice of the actuator size, operating and restraint characteristics. The multiple equilibria problem is addressed and a solution is proposed. Technical implementation issues of the control scheme are discussed. The controller design and tuning procedure for a multimachine model is illustrated by a simulation example.<<ETX>>

Reliable control to actuator signal attenuation-type faults

Controller designs are presented that are robust to partial actuator signal losses in linear systems. Design ranges are specified for the attenuation factor on each actuator signal. Both closed-loop stability and a prespecified H/sub /spl infin// norm bound are guaranteed for any combination of actuator attenuation-type failures in the design ranges. The reliable controller designs derived are related to associated soft-constrained (nonlinear) min-max-max game problems. Two choices of regulated-output variable are made. When the control signal is weighted by the attenuation factor in the cost functional, no nontrivial Nash equilibrium solution exists among pure strategies, but a reliable controller design is found corresponding to the upper value of the game. When the control signal is not weighted by the attenuation factor in the cost functional, a Nash (saddle-point) equilibrium solution exists with game value zero, resulting in a second reliable controller design.<<ETX>>