Frequency response

About: Frequency response is a research topic. Over the lifetime, 25705 publications have been published within this topic receiving 332249 citations.

Control topology options for single-phase UPS inverters

Abstract: Several control topologies for single-phase UPS inverters are presented and compared, with the common objective of providing a dynamically stiff, low THD, sinusoidal output voltage. Full state feedback, full state command controllers are shown utilizing both filter inductor current and filter capacitor current feedback to augment output voltage control. All controllers presented include output voltage decoupling in a manner analogous to "back-EMF" decoupling in DC motor drives. Disturbance input decoupling of the load current and its derivative is presented. An observer-based controller is additionally considered, and is shown to be a technically viable, economically attractive option. The accuracy transfer function of the observer estimate is used to evaluate its measurement performance. Comparative disturbance rejection is evaluated by overlaying the dynamic stiffness (inverse of output impedance) frequency response of each controller on a single plot. Experimental results for one controller are presented.

Performance comparison of three identification methods for the analysis of electromechanical oscillations

Abstract: This paper describes the results of a study to evaluate the performance of three identification methods for the study of low frequency electromechanical oscillations. The three identification methods considered are: the Steiglitz-McBride algorithm; the eigensystem realization algorithm; and the Prony method. The identification methods are used to identify low order linear systems of power systems modeled in standard transient stability programs. This is accomplished by processing the system response to a simple probing pulse. The frequency domain characteristics of several identified systems are compared using three power systems with lightly damped electromechanical modes.

Controller Design for Flexible, Distributed Parameter Mechanical Arms Via Combined State Space and Frequency Domain Techniques

Abstract: The potential benefits of the ability to control more flexible mechanical arms are discussed. A justification is made in terms of speed of movement. A new controller design procedure is then developed to provide this capability. It uses both a frequency domain representation and a state variable representation of the arm model. The frequency domain model is used to update the modal state variable model to insure decoupled states. The technique is applied to a simple example with encouraging results.

Alternative Geometries for Increasing Power Density in Vibration Energy Scavenging for Wireless Sensor Networks

Abstract: Vibration energy scavenging with piezoelectric material can currently generate up to 300 microwatts per cubic centimeter, making it a viable method of powering low-power electronics. Given the growing interest in small-scale devices, particularly wireless sensor networks, concerns over how to indefinitely power them have become extremely relevant. Current limiting factors in the field of piezoelectric vibration energy scavenging include: coupling coefficients, strain distribution, and frequency matching. This paper addresses each of these three factors with a novel design and a corresponding analysis of its performance. For example, the power output of a cantilevered rectangular piezoelectric beam is limited by its uneven strain distribution under load. A prototype scavenger using a harmonically matched trapezoidal geometry solves this problem by evening the strain distribution throughout the beam, increasing by 30% the output power per unit volume. Another design is created which softens the frequency response of the generator, relaxing the constraint of frequency matching. The paper concludes that each of the three challenges to vibration energy scavenging can be met through creativity in mechanism design, making higher power densities possible and broader applications more feasible.

Simulation of transmission line transients using vector fitting and modal decomposition

Abstract: This paper introduces a fast and robust method for rational fitting of frequency domain responses, well suited for both scalar and vector transfer functions. Application of the new method results in increased computational efficiency for transmission line models using modal decomposition with frequency dependent transformation matrices. This is due to the fact that the method allows the fitted elements of each eigenvector to share the same set of poles, and that accurate fitting can be achieved with a relatively low number of poles.