Frequency Response Of Control System Research Articles

Design of Plug-In Electric Vehicle's Frequency-Droop Controller for Primary Frequency Control and Performance Assessment

This paper describes a novel strategy to design the frequency-droop controller of plug in electric vehicles (PEVs) for primary frequency control (PFC). To be able to properly compare the frequency response of control system with and without PEVs, the design is done to guarantee the same stability margin for both systems in the worst case scenario. To identify the worst case, sensitivity analyses are conducted on a large set of system parameters performing eigenvalue analysis and bode plots. Three main contributions are included in this work: 1) we demonstrate that PEVs using the well-design droop controller significantly improve the PFC response while successfully preserving the frequency stability, 2) since the fast response of PEVs may cause to mask the governor-turbine response in conventional units, a novel control scheme is developed to replace some portion of PEV's reserve after a certain time by the reserve of conventional units during PFC, and 3) a method is proposed to evaluate the positive economic impact of PEV's participation in PFC. For the latter, the system PFC cost savings mainly through the avoidance of under frequency load shedding by PEVs are calculated. A large-scale power system and an islanded network are evaluated and compared through dynamic simulations, which illustrate the validity and effectiveness of the proposed methodologies.

Construction of bode envelopes using REP based range finding algorithms

The frequency domain analysis of systems is an important topic in control theory. Powerful graphical tools exist in classic control, such as the Nyquist plot, Bode plots, and Nichols chart. These methods have been widely used to evaluate the frequency domain behavior of system. A literature survey shows that various approaches are available for the computation of the frequency response of control systems under different types of parametric dependencies, such as affine, multi-linear, polynomial, etc. However, there is a lack of tools in the literature to construct the Bode envelopes for the general nonlinear type of parametric dependencies. In this paper, we address the problem of computation of the envelope of Bode frequency response of a non-rational transfer function with nonlinear parametric uncertainties varying over a box. We propose two techniques to compute the Bode envelopes: first, based on the natural interval extensions (NIE) combined with uniform subdivision and second, based on the existing Taylor model combined with subdivision strategy. We also propose the algorithms to further speed up both methods through extrapolation techniques.

On-Line Identification of Open-Loop Frequency Response and Two-Degree-of-Freedom Design Method of PID Control Systems

In this paper, we study the accuracy of the open-loop frequency response of control system obtained by on-line identification from the closed-loop frequency response, and show that the open-loop frequency response required for design based on the frequency response can be obtained accurately. Moreover, we consider feedforward-type two-degree-of-freedom PID control systems, and propose an on-line design method of feedback controllers, and a design method of feedforward controllers focused on the number of phase-lead elements between the reference input and the manipulated input. Furthermore, combining these design methods, an on-line design method of two-degree-of-freedom PID control systems is proposed. The efficiency of the proposed design method is evaluated by simulation.