Eigenvalue and frequency-domain analysis of the intermountain power project and the wscc network
The Western Systems Coordinating Council (WSCC) has several interarea modes of oscillation in the range of 0.3 to 0.8 Hz. The results of an investigation of how various network parameters and operating conditions affect the stability of those modes are presented. Eigenvalue and frequency-domain techniques are used. The study results show that numerous system parameters can have a significant impact on overall network stability. These parameters can include control settings, such as those in HVDC systems or power system stabilizers, or operational parameters, such as scheduled tie-line flows. The results show that careful analysis and tuning of all significant controls in a large network are necessary to ensure overall system stability and satisfactory performance. >
Small-signal modulation of the Pacific HVDC intertie
Recent undamped oscillations in the Western U.S. power system have indicated the need to improve system damping. The development of a control algorithm for small-signal modulation of the Pacific HVDC Intertie is described. The control signal which would be applied to the current regulator at the sending end of the dc intertie is based on rate of change of ac-intertie power. Results from simulation studies are presented which show that modulation will produce considerable damping.
Mechanism of the depressor response to dopamine in the rat treated with phenoxybenzamine.
Alterations of hypotensive responses to dopamine by antagonists were characterized in alpha-blocked, anaesthetized rats. Responses were not affected by d-propranolol (0.1 mg/kg) whereas d,1-propranolol (0.1 mg/kg) or haloperidol (1.0 mg/kg) attenuated them; higher doses of inhibitors (1.0 mg/kg; 5.0 mg/kg, respectively) failed to produce a higher inhibition, but combinations of low doses abolished the depressor responses. In adrenalectomized rats, hypotensive responses decreased; haloperidol always attenuated the responses while d,1-propranolol became ineffective. Dopamine produced an enhancement of plasma adrenaline and noradrenaline levels, which was decreased by d,1-propranolol and increased by haloperidol. The data suggest that in rats the depressor component of dopamine is due to activation of both dopaminergic and beta-adrenoceptors. The beta component appears to be due to the release of adrenaline. The results also support the concept of the existence in sympathetic nerve endings and adrenal glands of stimulatory beta-adrenergic and inhibitory dopaminergic prejunctional receptors.