Hysteretic control of grid-side current for a single-phase LCL grid-connected voltage source converter

© 2016. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/This paper proposes a new approach to control the grid-side current of LCL-grid connected voltage source converters using hysteretic relay feedback controllers. The closed loop system is stabilized by designing a local feedback around the relay element. The compensator allows the use of relay feedback controllers by making the controlled plant almost strictly positive real. The article proposes the use of the locus of the perturbed relay system as analysis and design tool and studies orbital stability for several plant and controller conditions. The approach is validated by means of simulation testing.Postprint (author's final draft

The determination of asymptotic and periodic behavior of dynamic systems arising in control system analysis Final report

Asymptotic and periodic behavior prediction for nonlinear control system with mathematical model of rigid body vehicl

Dynamic analysis of self-oscillating H-bridge inverters with state feedback

This paper presents a comprehensive approach to analyze the dynamics of a generalized model of resonant inverters using nonsmooth dynamical system theory. The model simultaneously covers both parallel and series resonant inverters under state feedback control. The multi-parametric physical space is reduced to a plane, which is divided in several regions with different dynamical behavior. The boundaries separating these regions are located by solving their corresponding equations and it is found that they all emerge from a singular point in the parameter plane. Suitability for applications of these regions is emphasized, thus providing useful criteria for parameter selection.Postprint (author's final draft

Conditions for forced and subharmonic oscillations in relay and quantized feedback systems

Ph.DDOCTOR OF PHILOSOPH

Study of numeric Saturation Effects in Linear Digital Compensators

Saturation arithmetic is often used in finite precision digital compensators to circumvent instability due to radix overflow. The saturation limits in the digital structure lead to nonlinear behavior during large state transients. It is shown that if all recursive loops in a compensator are interrupted by at least one saturation limit, then there exists a bounded external scaling rule which assures against overflow at all nodes in the structure. Design methods are proposed based on the generalized second method of Lyapunov, which take the internal saturation limits into account to implement a robust dual-mode suboptimal control for bounded input plants. The saturating digital compensator provides linear regulation for small disturbances, and near-time-optimal control for large disturbances or changes in the operating point. Computer aided design tools are developed to facilitate the analysis and design of this class of digital compensators

New results in relay feedback analysis and multivariable stability margins

Ph.DDOCTOR OF PHILOSOPH

Design study for LANDSAT-D attitude control system

The gimballed Ku-band antenna system for communication with TDRS was studied. By means of an error analysis it was demonstrated that the antenna cannot be open loop pointed to TDRS by an onboard programmer, but that an autotrack system was required. After some tradeoffs, a two-axis, azimuth-elevation type gimbal configuration was recommended for the antenna. It is shown that gimbal lock only occurs when LANDSAT-D is over water where a temporary loss of the communication link to TDRS is of no consequence. A preliminary gimbal control system design is also presented. A digital computer program was written that computes antenna gimbal angle profiles, assesses percent antenna beam interference with the solar array, and determines whether the spacecraft is over land or water, a lighted earth or a dark earth, and whether the spacecraft is in eclipse

Sliding mode control of constrained nonlinear systems

This technical note introduces the design of sliding mode control algorithms for nonlinear systems in the presence of hard inequality constraints on both control and state variables. Relying on general results on minimum-time higher-order sliding mode for unconstrained systems, a general order control law is formulated to robustly steer the state to the origin, while satisfying all the imposed constraints. Results on minimum-time convergence to the sliding manifold, as well as on the maximization of the domain of attraction, are analytically proved for the first-order and second-order sliding mode cases. A general result is presented regarding the domain of attraction in the general order case, while numerical results on the estimation of the domain of attraction and on minimum-time convergence are discussed for the third-order case, following a procedure applicable to a sliding mode of any order

PWM motor control: Model and servo analysis

In recent years, the performance requirements of high power servo motor systems utilizing pulse width modulated (PWM) switching amplifiers have steadily increased. These PWM motor amplifiers perform an important function in the d.c. servo system by boosting the low level command signal to the high voltage and current levels required by the motor. Ideally, this power gain is to be constant over all input frequencies but, in reality, gain is frequency dependent which affects system dynamics. The amplifier gain and phase versus frequency relationships an*i amplifier noise and d.c. offsets which may affect system response must be known to the servo designer to properly design the motor control system. The switching effects of the PWM amplifier may result in making the overall system unstable if the system bandwidth is kept high with respect to the PWM switching frequency. Since the standard servo design techniques utilize linear system modeling, analysis, and compensation, it would be very advantageous to the design engineer to have a linear model which best approximates the true nonlinear PWM amplifier. This work will look at the output response of the PWM amplifier with respect to stability and output ripple. A linear model will be developed which simulates these stability and ripple effects in a position control servo system and which is valid as system bandwidth reaches one-third the PWM switching frequency. This work extends the application of the Principle of Equivalent Areas [141 to the bipolar PWM amplifier. It is then combined with a detailed analysis of the PWM waveform by Double Fourier Transform to yield the unique PWM switching effects in a position control servo system. Theoretical results of the newly derived sampling plus harmonic linear model are verified by computer simulation

Design, analysis, and control of large transport aircraft utilizing engine thrust as a backup system for the primary flight controls

A review of accidents that involved the loss of hydraulic flight control systems serves as an introduction to this project. In each of the accidents--involving transport aircraft such as the DC-10, the C-5A, the L-1011, and the Boeing 747--the flight crew attempted to control the aircraft by means of thrust control. Although these incidents had tragic endings, in the absence of control power due to primary control system failure, control power generated by selective application of engine thrust has proven to be a viable alternative. NASA Dryden has demonstrated the feasibility of controlling an aircraft during level flight, approach, and landing conditions using an augmented throttles-only control system. This system has been successfully flown in the flight test simulator for the B-720 passenger transport and the F-15 air superiority fighter and in actual flight tests for the F-15 aircraft. The Douglas Aircraft Company is developing a similar system for the MD-11 aircraft. The project's ultimate goal is to provide data for the development of thrust control systems for mega-transports (600+ passengers)