1991 outlook: mild recession, mild recovery

A summary of the January 18, 1991 Fourth District Economists' Roundtable, noting the panelists' forecasts for the economy in the wake of uncertainties surrounding the Persian Gulf War.Business forecasting

Can Long-Run Restrictions Identify Technology Shocks?

Gali's innovative approach of imposing long-run restrictions on a vector autoregression (VAR) to identify the effects of a technology shock has become widely utilized. In this paper, we investigate its reliability through Monte Carlo simulations of several relatively standard business cycle models. We find it encouraging that the impulse responses derived from applying the Gali methodology to the artificial data generally have the same sign and qualitative pattern as the true responses. However, we highlight the importance of small-sample bias in the estimated impulse responses and show that the magnitude and sign of this bias depend on the model structure. Accordingly, we caution against interpreting responses derived from this approach as ``model-independent'' stylized facts. Moreover, we find considerable estimation uncertainty about the quantitative impact of a technology shock on macroeconomic variables, and a corresponding level of uncertainty about the contribution of technology shocks to the business cycletechnology shocks, vector autoregressions, real business cycles

Razvoj i implementacija upravljačkih algoritama za sinkroni generator

This paper proposes a DSP based simulator for development and implementation of control algorithms. The simulator is used to control a synchronous aggregate model in real time. The simulator consists of a PC (on which a synchronous generator connected to AC network is simulated) connected through a communication channel to a DSP (on which the control algorithm is implemented). The simulator makes implementation of a control algorithm faster and easier. It also enables verification of a control algorithm in real time. Simulation results show that there are no significant differences between non-real time simulations (on a PC) and real time simulations (on a DSP based simulator). This paper also presents design and implementation of a nonlinear control algorithm for excitation control system based on the Lyapunov’s direct method. Both conventional excitation control algorithm and proposed nonlinear excitation control algorithm were implemented and tested on the real time simulator. The obtained simulation results show that proposed nonlinear excitation control algorithm better damps electromechanical oscillations than conventional excitation control algorithm.U radu je prezentirana upotreba simulatora za rad u stvarnom vremenu za razvoj i implementaciju upravljačkih algoritama. Simulator je korišten za upravljanje modelom sinkronog agregata u realnom vremenu. Simulator se sastoji od osobnog računala (na kojem se simulira model generatora spojen na elektroenergetski sustav) koje je preko komunikacijskog kanala spojen na DSP (na koji je implenetiran upravljački algoritam). Simulator omogućuje bržu i jednostavniju implementaciju upravljačkog algoritma. Isto tako omogućuje verifikaciju upravljačkog algoritma u realnom vremenu. Isto tako, u ovom radu dana je izvedba i implementacija nelinearnog algoritma upravljanja uzbudom zasnovana na direktnoj teoriji Ljapunova. I klasičan i predloženi nelinearni algoritam upravljanja uzbudom su implementirani i testirani na simulatoru za rad u stvarnom vremenu. Rezultati simulacije pokazuju da sustav s predloženim nelinearnim algorit-mom upravljanja uzbudom bolje prigušuje elektromehaičke oscilacije u odnosu na sustav s klasičnim algoritmom upravljanja uzbudom

Roundtable's Rx for the economy: first, do no harm

An overview of the January 24, 1992 meeting of the Fourth District Economists' Roundtable, at which participants discussed how longer-term structural adjustments taking place in many of the nation's industries may be restraining the recovery.Business forecasting

SIGMA: A New Open Economy Model for Policy Analysis

In this paper, we describe a new multicountry open economy SDGE model named "SIGMA" that we have developed as a quantitative tool for policy analysis. We compare SIGMA's implications to those of an estimated large-scale econometric policy model (the FRB/Global model) for an array of shocks that are often examined in policy simulations. We show that SIGMA's implications for the near-term responses of key variables are generally similar to those of FRB/Global. Nevertheless, some quantitative disparities between the two models remain due to certain restrictive aspects of SIGMA's optimization-based framework. We conclude by using long-term simulations to illustrate some areas of comparative advantage of our SDGE modeling framework.

Current outlook: sustained growth, sustained inflation

A report on the May 4, 1990 meeting of the Fourth District Economists' Roundtable, at which participants predicted a stronger long-term growth rate for the national economy through 1991 and an inflation rate of about 4 percent.Economic conditions - United States

Limiteri uzbude malih sinkronih generatora

Small synchronous generators connected to electrical power system operate by following changes in the system voltage. Limiting of the generator excitation current enables generator operation within limits of the power chart diagram and increases the safety and availability of generator in the system. This paper includes algorithms for the determination of maximum and minimum excitation current limits and the implementation within digital control system of generator voltage. The performance of generator excitation current limits was experimentally verified on a laboratory model.Mali sinkroni generatori pri radu u elektroenergetskom sustavu slijede promjene napona sustava. Limitiranje uzbudne struje generatora omogućava rad generatora unutar granica pogonske karte te povećava sigurnost i raspoloživost generatora u sustavu. Ovaj članak sadrži algoritme za određivanje limita maksimalne i minimalne uzbudne struje te za implementaciju u digitalnom sustavu regulacije napona generatora. Ponašanje limitera uzbudne struje generatora eksperimentalno je potvrđeno na laboratorijskom modelu

Limiteri uzbude malih sinkronih generatora

Small synchronous generators connected to electrical power system operate by following changes in the system voltage. Limiting of the generator excitation current enables generator operation within limits of the power chart diagram and increases the safety and availability of generator in the system. This paper includes algorithms for the determination of maximum and minimum excitation current limits and the implementation within digital control system of generator voltage. The performance of generator excitation current limits was experimentally verified on a laboratory model.Mali sinkroni generatori pri radu u elektroenergetskom sustavu slijede promjene napona sustava. Limitiranje uzbudne struje generatora omogućava rad generatora unutar granica pogonske karte te povećava sigurnost i raspoloživost generatora u sustavu. Ovaj članak sadrži algoritme za određivanje limita maksimalne i minimalne uzbudne struje te za implementaciju u digitalnom sustavu regulacije napona generatora. Ponašanje limitera uzbudne struje generatora eksperimentalno je potvrđeno na laboratorijskom modelu

The outlook: no boom, no doom

A summation of the forecasts of 25 economists meeting at the October 1991 meeting of the Fourth District Economists' Roundtable, with the consensus that a mild recovery is under way.Economic conditions - United States