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Modular multilevel converters (MMCs), with the filter-less and transformer-less features, are considered as a promising topology for high-efficiency medium voltage (MV) high voltage (HV) drive systems. However, at low frequencies (< 30 Hz), a large current ripple flowing through the capacitors of each submodule will cause significant capacitor voltage fluctuation. This paper proposes an optimal...
This paper presents the small-signal modeling and controller design of a single phase multilevel, three-port based on gallium nitride (GaN) devices for renewable energy and UPS applications. The system has two ac-port with five-level waveforms and one DC port. A small-signal model of the converter is derived by the method of state-space averaging. It is controlled with two loops, an outer voltage...
This paper describes the nominal control system design to counter the effect of deployment of an electro-dynamic tether on a polar low-earth orbit nano-satellite. The complete tether assembly including the deployment mechanism, choice of material, length of the tether, preferred door axis for deployment of tether have been explained in detail. Analysis of the effect of deployment of the tether on...
This paper describes the control systems employed by a nano-satellite ‘Parikshit’ to satisfy the payload requirement to limit the angular velocity of the satellite within 1 deg/sec. Also described is the satellite kinematics and dynamics model in space environment to test and evaluate the performance of the controller to meet the desired stability. The entire dynamics of the satellite have been modelled...
This paper describes the dynamics of a polar low earth orbit nano-satellite as a consequence of tether deployment; and the control system to counter its effect. The complete tether assembly, including the deployment mechanism, choice of material, length of the tether, preferred door axis for deployment of tether, have been explained in detail. A force sensor, to measure the forces associated with...
This paper describes a method to determine the rate of descent of a nano-satellite which uses an electrodynamic tether for de-orbiting. Also described, is an orbit propagator model of the continuously varying orbit and a control algorithm during its descent. An elaborate attitude control model is also proposed which is complemented by a set of sensors and actuators. Use of tethers provides an economical...
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