Implementation and laboratory test results for an adaptive powersystem stabilizer based on linear optimal control

Implementation of an adaptive power system stabilizer (PSS) based on linear optimal control is described. The generator is identified in real time, and a special third-order discrete Riccati equation is solved in each sample interval. Because the output of the generator is fed back directly, the controller can track the system very fast. Experimental studies on a physical model of a micromachine alternator connected to a constant voltage bus through a transmission line are reported. The PSS was implemented using a multiprocessor architecture employing separate processors for identification, control, and man-machine interface. The various parameters are tuned to obtain the best performance under various disturbances. Test results show that the proposed PSS is very effective in damping out the system oscillation     

A self-tuning automatic voltage regulator

A self-tuning automatic voltage regulator (AVR) for a synchronous generator is presented. The regulator proposed improves the system stability; it is simple and can handle stochastic load changes. The algorithm for the proposed AVR combines a least-squares estimator with a minimum variance control strategy computed from an estimated model. It is shown that if the parameter estimates converge, the control law obtained is in fact the minimum variance control law that would be computed if the parameters of the system were known. The algorithm proposed has been tested by simulation and also by implementation on a minicomputer. Results show that, in general, the system performance is improved with a self-tuning regulator.     

On the polarographic behaviour of the palmitates and myristates of copper and cobalt

Pyridine complexes of myristates and palmitrates of copper and cobalt were found to be reducible at the dropping mercury electrode in 1) LiCl in 1:1 benzene methanol mixture; 2) MeHSO₄ in 1:1 benzene methanol mixture; and 3) KCl in glycol. The diffusion current was found to be a linear function of concentration. Hence it was concluded that this linear relationship can be successfully employed for the estimation of cobalt and copper concentration in their respective soaps.     

Optimal design of flexible chemical processes

Practical ways are still needed for optimizing the design of chemical processes, with allowance for uncertain specifications and future changes in economic parameters. This problem fits the two-stage formulation of Dantzig[1]. Unfortunately, we found several practical difficulties in applying this two-stage analysis to realistic process design models. Some of these can be overcome by proper formulation of the process model or by improvements in the computational algotrithm. In the end, we obtained, for two realistic process models, optimal designs with improved flexibility compared to designs based on fixed parameters; the well-known inequalities were satisfied. More generally, the paper includes suggestions for practical efficient use of the two-stage approach in process design.     

Mechanical properties of 2 % Co eutectoid steel

Tensile, impact and fatigue strength of high-purity 0 % and 2 % cobalt steels of eutectoid compositions have been determined using standard testing methods. The addition of cobalt has caused an increase in tensile and yield strength and a decrease in impact and fatigue strengths.     

A General Approach to Sampled-Data Modeling for Power Electronic Circuits

A general sampled-data representation of the dynamics of arbitrary power electronic circuits is proposed to unify existing approaches. It leads, via compact and powerful notation, to disciplined modeling and straightforward derivation of small-signal models that describe perturbations about a nominal cyclic steady state. Its usefulness is further illustrated by considering the representation and analysis of a class of symmetries in circuit operation. The results of the application of this methodology to modeling the small-signal dynamics of a series resonant converter are described. The results correlate well with simulation results obtained on the Massachusetts Institute of Technology's Parity Simulator. What is of greater significance is the fact that the small-signal model is obtained in a completely routine way, starting from a general formulation and working down to the actual circuit; this contrasts with the circuit-specific analyses that are more typical of the power electronics literature. The automatability of this procedure is also discussed, and it is pointed out that the key ingredients for automatic generation of dynamic models from a circuit specification are now available.     

Elasto-plastic response of an externally cracked cylinder analyzed by the method of lines

Further results on elasto-plastic response of flawed specimens by the Method of Lines are reported. Numerical results of stresses, displacements, the growth of plastic zone, and the J₁-integral are presented. Computations obtained include that for elastic response and that for elasto-plastic response. The stress intensity factor K₁ is determined by two different approaches: the two-term expansion method and the J₁-K₁ relation. A comparison of K₁ with that recorded in Tada, Paris and Irwin is presented. The range of percentage difference is between 6 and 23, depending upon crack length. A typical run of the computer program on an IBM $\text{370}\text{168}$, using double precision arithmetic, takes about 3 min CPU time and 700k bites of storage.