Turbine speed control system based on a fuzzy-PID

The flexibility demand of marine nuclear power plant is very high,the multiple parameters of the marine nuclear power plant with the once-through steam generator are strongly coupled,and the normal PID control of the turbine speed can't meet the control demand.This paper introduces a turbine speed Fuzzy-PID controller to coordinately control the steam pressure and thus realize the demand for quick tracking and steady state control over the turbine speed by using the Fuzzy control's quick dynamic response and PID control's steady state performance.The simulation shows the improvement of the response time and steady state performance of the control system.

On Advanced Control Methods toward Power Capture and Load Mitigation in Wind Turbines

This article provides a survey of recently emerged methods for wind turbine control. Multivariate control approaches to the optimization of power capture and the reduction of loads in components under time-varying turbulent wind fields have been under extensive investigation in recent years. We divide the related research activities into three categories： modeling and dynamics of wind turbines, active control of wind turbines, and passive control of wind turbines. Regarding turbine dynamics, we discuss the physical fundamentals and present the aeroelastic analysis tools. Regarding active control, we review pitch control, torque control, and yaw control strategies encompassing mathematical formulations as well as their applications toward different objectives. Our survey mostly focuses on blade pitch control, which is considered one of the key elements in facilitating load reduction while maintaining power capture performance. Regarding passive control, we review techniques such as tuned mass dampers, smart rotors, and microtabs. Possible future directions are suggested.

Research on Modeling and Control of a 100 kW Micro Bio-Gas Turbine

In order to know about the influences of disturbance on the operating performance, the present work developed the overall dynamic simulation model of the micro gas turbine and investigated the control system under the disturbances of environmental temperature and unit load. The response processes of main parameters have been obtained. It found that the compressor pressure ratio and the fuel flow rate increase in the case of natural gas being replaced by pine gas. When the system reaches a new steady state, the main parameters change to different values. The output power decreases with the declining of the air mass flow when the ambient temperature rises, the biomass gas mass flow rate increases under the regulation of the control system to maintain the output power and rotating speed in which the thermal efficiency reduces by 1.40%. The thermal efficiency enhances with the increase of output load. The control system can quickly and effectively act to maintain the key parameters at desired value.

SIMULATION STUDY OF GENERALIZED MINIMUM VARIANCE CONTROL FOR AN EXTRACTION TURBINE

In an extraction turbine, pressure of the extracted steam and rotate speed of the rotor are two important controlled quantities. The traditional linear state feedback control method is not perfect enough to control the two quantities accurately because of existence of nonlinearity and coupling. A generalized minimum variance control method is studied for an extraction turbine. Firstly, a nonlinear mathematical model of the control system about the two quantities is transformed into a linear system with two white noises. Secondly, a generalized minimum variance control law is applied to the system. A comparative simulation is done. The simulation results indicate that precision and dynamic quality of the regulating system under the new control law are both better than those under the state feedback control law.

Wind Generator Stabilization with Doubly-Fed Asynchronous Machine

This paper investigates the function of doubly-fed asynchronous machine(DASM)with emphasis placed on its ability to the stabilization of the power system including wind generators.P(active power)and Q(reactive power)compensation from DASM can be regulated independently through secondary-excitation controlling.Simulation results by power system computer aided design(PSCAD)show that DASM can restore the wind-generator system to a normal operating condition rapidly even following severe transmission-line failures.Comparison studies have also been performed between wind turbine pitch control and proposed method.

Analysis of grid-connected voltage stability of FSCWT based on bifurcation theory

This paper studies on the change mechanisms of the voltage stability caused by the grid connection of front-end speed-controlled wind turbines(FSCWT)integrating into power system.First of all,the differential algebraic equations describing the dynamic characteristics of wind turbines are illustrated.Then,under the guidance of IEEE3 node system model,the influence of the angular velocity of wind turbines,the reactive power and the active power at load bus on the voltage stability of grid-connection has been analyzed by using bifurcation theory.Finally,the method of linear-state feedback control has been applied to the original system in accordance with the bifurcation phenomenon of grid-connected voltage caused by the increase in the active power at load bus.Research shows that voltage at the grid-connected point would be changed with the fluctuation of turbines angular velocity.And increasing its reactive power can enhance voltage at the grid-connected point;problem of bifurcation at the grid-connected point can be delayed when increasing the gain k s of feedback controller within a certain range.

Optimal Auxiliary Frequency Control of Wind Turbine Generators and Coordination with Synchronous Generators

Auxiliary frequency control of a wind turbine generator(WTG) has been widely used to enhance the frequencysecurity of power systems with high penetration of renewableenergy. Previous studies recommend two types of control schemes,including frequency droop control and emulated inertia control,which simulate the response characteristics of the synchronousgenerator (SG). This paper plans to further explore the optimalauxiliary frequency control of the wind turbine based on previousresearch. First, it is determined that the virtual inertia control haslittle effect on the maximum rate of change of frequency (MaxROCOF)if the time delay of the control link of WTG is taken intoconsideration. Secondly, if a WTG operates in maximum powerpoint tracking (MPPT) mode and uses the rotor deceleration forfrequency modulation, its optimal auxiliary frequency control willcontain only droop control. Furthermore, if the droop control isproperly delayed, better system frequency response (SFR) willbe obtained. The reason is that coordination between the WTGand SG is important for SFR when the frequency modulationcapability of the WTG is limited. The frequency modulationcapability of the WTG is required to be released more properly.Therefore, when designing optimal auxiliary frequency controlfor the WTG, a better control scheme is worth further study.

Feedforward Control for Wind Turbine Load Reduction with Pseudo-LIDAR Measurement

A gain-scheduled feedforward controller, based on pseudo-LIDAR （light detection and ranging） wind speed measurement, is designed to augment the baseline feedback controller for wind turbine＇s load reduction in above rated operation. The pseudo-LIDAR measurement data are generated from a commercial software- Bladed using a designed sampling strategy. The nonlinear wind turbine model has been simplified and linearised at a set of equilibrium operating points. The feedforward controller is firstly developed based on a linearised model at an above rated wind speed, and then expanded to the full above rated operational envelope by employing gain scheduling strategy. The combined feedforward and baseline feedback control is simulated on a 5MW industrial wind turbine model. Simulation studies demonstrate that the proposed control strategy can improve the rotor and tower load reduction performance for large wind turbines.

Time-triggered State-machine Reliable Software Architecture for Micro Turbine Engine Control

Time-triggered （TT） embedded software pattern is well accepted in aerospace industry for its high reliability. Fi-nite-state-machine （FSM） design method is widely used for its high efficiency and predictable behavior. In this paper, the time-triggered and state-machine combination software architecture is implemented for a 25 kg thrust micro turbine engine （MTE） used for unmanned aerial vehicle （UAV） system; also model-based-design development workflow for airworthiness software directive DO-178B is utilized. Experimental results show that time-triggered state-machine software architecture and development method could shorten the system development time, reduce the system test cost and make the turbine engine easily comply with the airworthiness rules.

Passive Control of Laminar Separation Bubble with Spanwise Groove on a Low-speed Highly Loaded Low-pressure Turbine Blade

LES (Large-Eddy Simulation) computations were preformed to investigate the mechanisms of a kind of spanwisegroove for the passive control of laminar separation bubble on the suction surface of a low-speed highly loadedlow-pressure turbine blade at Re = 50,000 (Reynolds number, based on inlet velocity and axial chord length).Compared with the smooth suction surface, the numerical results indicate that: (1) the groove is effective toshorten and thin the separation bubble, which contributes the flow loss reduction on the groove surface, by thinningthe boundary layer behind the groove and promoting earlier transition inception in the separation bubble; (2)upstream movement of the transition inception location on the grooved surface is suggested being the result of thelower frequency at which the highest amplification rate of instability waves occurs, and the larger initial amplitudeof the disturbance at the most unstable frequency before transition; and (3) the viscous instability mode ispromoted on the grooved surface, due to the thinning of the boundary layer behind the groove.

Electroacupuncture compound anesthesia in radiofrequency ablation for hypertrophic inferior turbinate:a randomized controlled trial

Objective To explore the feasibility of electroacupuncture compound anesthesia in radiofrequency ablation for hypertrophic inferior turbinate.Methods The patients confirmed to the enrolled criteria were randomly divided into an observation group（n=31） and a control group（n=30）.In the observation group,electroacupuncture was applied to Sìbái（四白 ST 2）,Xiàguān（下关 ST 7）,Hégǔ（合谷 LI 4） and Zhīgōu（支沟 TE 6） on the left side for the anesthesia and the routine local anesthesia was done on the right side.In the control group,the routine local anesthesia was adopted on both sides.The feelings of pain,circulatory index and operation effect were observed and compared between the two groups.Results During radiofrequency ablation,the pain grades of two measurements on the left side and the 2nd measurement on the right in the observation group were all lower than those in the control group（all P〈0.05）.In the observation group,the pain grade on the left side was lower than that on the right side（P〈0.05）,and the systolic blood pressure and the heart rate were lower than those in the control group when undergoing the 2nd radiofrequency ablation on the right side and on the left side,respectively（all P〈0.05）.There was no significant difference in operation effect between the two groups.Conclusion Electroacupuncture compound anesthesia can meet the analgesia requirement of radiofrequency ablation for hypertrophic inferior turbinate,and would be helpful to prevent cyclic fluctuation during the operation at the same time.

Application of wireless sensor networks to aircraft control and health management systems

Use of fly-by-wire technology for aircraft flight controls have resulted in an improved performance and reliability along with achieving reduction in control system weight. Implementation of full authority digital engine control has also resulted in more intelligent, reliable, light-weight aircraft engine control systems. Greater reduction in weight can be achieved by replacing the wire harness with a wireless communication network. The first step towards fly-by-wireless control systems is likely to be the introduction of wireless sensor networks (WSNs). WSNs are already finding a variety of applications for both safety-critical and nonsafety critical distributed systems. Some of the many potential benefits of using WSN for aircraft systems include weight reduction, ease of maintenance and an increased monitoring capability. This paper discusses the application of WSN for several aircraft systems such as distributed aircraft engine control, aircraft flight control, aircraft engine and structural health monitoring systems. A brief description of each system is presented along with a discussion on the technological challenges. Future research directions for application of WSN in aircraft systems are also discussed.

An intelligent control method for a large multi-parameter environmental simulation cabin

The structure and characteristics of a large multi-parameter environmental simulation cabin are introduced.Due to the diffculties of control methods and the easily damaged characteristics,control systems for the large multi-parameter environmental simulation cabin are diffcult to be controlled quickly and accurately with a classical PID algorithm.Considering the dynamic state characteristics of the environmental simulation test chamber,a lumped parameter model of the control system is established to accurately control the multiple parameters of the environmental chamber and a fuzzy control algorithm combined with expert-PID decision is introduced into the temperature,pressure,and rotation speed control systems.Both simulations and experimental results have shown that compared with classical PID control,this fuzzy-expert control method can decrease overshoot as well as enhance the capacity of anti-dynamic disturbance with robustness.It can also resolve the contradiction between rapidity and small overshoot,and is suitable for application in a large multi-parameter environmental simulation cabin control system.

Numerical Study of Improving Aerodynamic Performance of Low Solidity LPT Cascade through Increasing Trailing Edge Thickness

This paper presents a new idea to reduce the solidity of low-pressure turbine(LPT) blade cascades,while remain the structural integrity of LPT blade.Aerodynamic performance of a low solidity LPT cascade was improved by increasing blade trailing edge thickness(TET).The solidity of the LPT cascade blade can be reduced by about12.5% through increasing the TET of the blade without a significant drop in energy efficiency.For the low solidity LPT cascade,increasing the TET can decrease energy loss by 23.30% and increase the flow turning angle by1.86% for Reynolds number(Re) of 25,000 and freestream turbulence intensities(FSTT) of 2.35%.The flow control mechanism governing behavior around the trailing edge of an LPT cascade is also presented.The results show that appropriate TET is important for the optimal design of high-lift load LPT blade cascades.