Control Switching Scheme Research Articles

Reduction of Three-Phase Transformer Inrush Currents Using Controlled Switching

This article proposes a new approach for reducing inrush currents in three-phase three-legged stacked-core power transformers. Although magnitudes of inrush currents may not be as high as short-circuit currents, they are extremely detrimental to normal operation of power transformers. In this article, a new controlled switching scheme that takes into consideration both core saturation and residual flux is proposed to reduce inrush currents. Also, a transient model based on the duality transformation between electric and magnetic circuits is proposed, where a nonlinear inductance is used to simulate core saturation. The proposed scheme is demonstrated on a real transformer by both laboratory experiments and performing simulations. The Alternative Transients Program is used to simulate a wide spectrum of possible operating conditions. The experimental and simulation results show that inrush currents are significantly reduced after utilizing the proposed scheme. Therefore, the proposed controlled switching scheme will result in relaxing inrush-current-related constraints in designing and manufacturing three-phase power transformers, which, in turn, will reduce their cost.

Mystique: A Fine-Grained and Transparent Congestion Control Enforcement Scheme

TCP congestion control is a vital component for the latency of Web services. In practice, a single congestion control mechanism is often used to handle all TCP connections on a Web server, e.g., Cubic for Linux by default. Considering complex and ever-changing networking environment, the default congestion control may not always be the most suitable one. Adjusting congestion control to meet different networking scenarios usually requires modification of TCP stacks on a server. This is difficult, if not impossible, due to various operating system and application configurations on production servers. In this paper, we propose Mystique, a light-weight, flexible, and dynamic congestion control switching scheme that allows network or server administrators to deploy any congestion control schemes transparently without modifying existing TCP stacks on servers. We have implemented Mystique in Open vSwitch (OVS) and conducted extensive test-bed experiments in both public and private cloud environments. Experiment results have demonstrated that Mystique is able to effectively adapt to varying network conditions, and can always employ the most suitable congestion control for each TCP connection. More specifically, Mystique can significantly reduce latency by 18.13% on average when compared with individual congestion controls.

A 96.88% area-saving and 99.72% energy-reduction switching scheme for SAR ADC with a novel two-step quantisation technique

This paper presents a novel area-saving and energy-efficient switching capacitor structure for successive approximation register analog-to-digital conversions, which uses a two-step quantisation logic control switching scheme. The two steps are coarse and fine quantisation respectively. During the coarse quantisation, there is no power consumption at the first two cycles. The fine quantisation does not increase the number of binary capacitors while consumes no energy. Therefore, the two-step quantisation switching scheme can significantly reduce both the power consumption and the capacitor area. Simulation results show that the structure can reduce the average energy and the capacitor area by 99.72% and 96.88% respectively over the conventional method.

Redundant adaptive robust tracking of active satellite and error evaluation

An approach to active target satellite tracking is presented. The kinematic models based on differential orbital elements and unbiased converted measurements are adopted to approximate the dynamic orbital relative tracking system, and then followed by the proposed redundant adaptive robust extended Kalman filter (RAREKF). The analysis of working status of robust filters shows that the innovation controlled switching scheme in AREKF fails under the unmodelled non-linear errors that exist all the time in orbital motions, and the loss of filtering optimality will be caused. So, a tunable redundancy factor and a novel compensation function are introduced into the RAREKF by extending the sufficient conditions of stable filtering. To evaluate the result of this tracking method, a meaningful error index is provided by consideration of the errors from both the model and the filter. The simulation shows the superiority of the RAREKF over the AREKF, uncoupled extended Kalman filter (EKF) and the usual EKF. By using the provided index, it also illustrates the lowest error level and best performance of the proposed tracking method in all the compared ones with different models and filters.

Proportional Integral Derivative Based Fault Tolerant Control for a Gas Turbine

This paper presents a fault tolerant control switching scheme with embedded fault detection and isolation system for the gas turbine of a combined cycle power plant. Mechanical faults of the turbogenerator are considered as case study. Previous to the control design, the detection and isolation capabilities of the gas turbine are studied by applying structural analysis to a first principles based gas turbine model. As a result, a new sensor was suggested to improve the detectability and isolability with respect to mechanical faults and sensors faults. Furthermore, the active fault tolerant control developed is based on stabilizing families of proportional integral derivative (PID) controllers, which are tuned off-line and the plant switching scheme preserves the stability of the whole closed-loop system, thanks to a careful selection of controller according to fault conditions. Simulation results with nonlinear model show the potential of the procedure.

Fault Tolerant Control with PID's for a Gas Turbine

This paper proposes a fault active tolerant control switching scheme with a PID's set and switching functions to manage the faults conditions. The family of PIDs which stabilizes the model in each fault condition is off-line computed following a procedure based on the signature of the closed loop rational function. To guarantee the closed loop stability between switching and reduce the number of PID's sets in the scheme a switching logic function for the controllers is selected using the LMI theory. The scheme is applied to the case of critical faults of a gas turbo generator of an electric plant, assuming the existence of a fault reconstruction system and known the multiple frequency responses of the gas turbine with four fault conditions. The comparison of a classic controller and the new scheme is shown by simulation results using real parameter of a Mexican electric plant.