Wicket Gate Opening Research Articles

Application of a multi-input multi-output (MIMO) nonlinear non-minimum phase system control method to hydro turbine unit

In this paper, in view of the non minimum phase characteristics of hydraulic turbine unit, a method of designing the controller of multi-input multi-output (MIMO) nonlinear non-minimum phase system is proposed and applied to hydraulic turbine unit system described by double control input fifth order model. The turbine output electromagnetic power and generator power angle are stabilized by wicket gate opening and excitation combined control. Firstly, the method for designing the controller of multi-input multi-output (MIMO) nonlinear non-minimum phase system is introduced. The method is based on state feedback theory, pole assignment theory and Lyapunov stability theory. Secondly, the control law of hydro turbine unit is given according to the method. Results of simulation indicate that this nonlinear non-minimum phase controller has a good effect when applied to the hydro turbine unit.

Transient simulation on closure of wicket gates in a high-head Francis-type reversible turbine operating in pump mode

To solve the problem of grid instabilities, regulation in the Pumped Hydro Energy Storage (PHES) plants should quickly respond to the variation of electricity produced by unpredictable renewable energy. In this paper, a power reduction scenario applied to a pump turbine of a PHES is simulated considering the transient closure process of wicket gate. A novel dynamic mesh technique is applied to simulate the rotation of wicket gate vanes from best efficiency point to shutdown condition. Detached Eddy Simulation (DES) turbulence model is utilized to capture complex unsteady flow and the water weak compressibility effect is considered in the transient simulation. Flow rate, torque, power and pressure are analysed by the Fast Fourier Transform (FFT) and Continuous Wavelet Transform (CWT) methods. The results illustrate the delay between the performance parameters flow rate and power and the wicket gate opening angle. The closure of wicket gates affects the flow characteristics downstream the wicket gates greatly, causing intensive pressure fluctuations. The magnitude of pressure fluctuations downstream the wicket gate becomes the highest with the wicket gate closure of about 60%. Aside the blade passage frequency, a low frequency occurs, with the appearance of unsteady flow in pump turbine. Moreover, strong torque pulsations occur on the pin of the wicket vane when the percentage of closure is between 60% and 80%, with peaks much higher than that at the best efficiency point. The transient results can provide meaningful reference to the regulation law of wicket gate for safe operation of the pump turbine.

Numerical Simulation of a Pump–Turbine Transient Load Following Process in Pump Mode

This paper presents the simulation of the dynamic behavior of variable speed pump–turbine. A power reduction scenario at constant wicket gate opening was numerically analyzed from 100% to 93% rpm corresponding to a power reduction from full load to about 70% with a ramp rate of 1.5% per second. The flow field analysis led to the onset and development of unsteady phenomena progressively evolving in an organized rotating partial stall during the pump power reduction. These phenomena were characterized by frequency and time–frequency analyses of several numerical signals (pressure, blade torque, and flow rate in blade passages). The unsteady pattern in return channel strengthened emphasizing its characteristic frequency with the rotational velocity decreasing reaching a maximum and then disappearing. At lower rotational speed, the flow field into the wickets gates channel starts to manifest a full three-dimensional (3D) flow structure. This disturbance was related to the boundary layer separation and stall, and it was noticed by a specific frequency.

Electric Speed Governor for 1kw Microhydro Generator

Electricity performance is characterized by the stability of voltage and frequency of the generator. To maintain the electricity performance, the generator speed is held stable at its nominal speed using a governor system. Electric governor system commonly used on hydro power plant. However in this study the electric governor system was developed for microhydro power plant. The Electric governor system was developed using NI myRIO® 1900 microcontroller device to accelerate the response due to load variations, and can be functioned as monitoring equipment.. The microcontroller device obtained input signal from generator speed sensor, voltage and ampere meter, and the position of the wicket gate. Afterwards, the microcontroller regulate the required wicket gate opening and the generator speed can be held stable. The governor system developed for 3000 rpm, 220 V, and 1 kW generator. The data obtained from this study shown that the developed electrical governor system has a 20-second response time to return the generator's speed to its nominal speed with load variations given to the generator is every 20% (200W). Operational shutdown system by the governor system due to the instability of the generator speed takes 24 s.

Assessing hydraulic conditions through Francis turbines using an autonomous sensor device

Fish can be injured or killed during turbine passage. This paper reports the first in-situ evaluation of hydraulic conditions that fish experienced during passage through Francis turbines using an autonomous sensor device at Arrowrock, Cougar, and Detroit Dams. Among different turbine passage regions, most of the severe events occurred in the stay vane/wicket gate and the runner regions. In the stay vane/wicket gate region, almost all severe events were collisions. In the runner region, both severe collisions and severe shear events occurred. At Cougar Dam, at least 50% fewer releases experienced severe collisions in the runner region operating at peak efficiency than at the minimum and maximum opening, indicating the wicket gate opening could affect hydraulic conditions in the runner region. A higher percentage of releases experienced severe events in the runner region when passing through the Francis turbines than through an advanced hydropower Kaplan turbine (AHT) at Wanapum Dam. The nadir pressures of the three Francis turbines were more than 50% lower than those of the AHT. The three Francis turbines had much higher magnitudes and rates of pressure change than the AHT. This study provides critical information on hydraulic conditions and fish passage information of Francis turbines, which can help guide future laboratory studies of fish passing through Francis turbine, design fish-friendly turbines, and optimize the operation of existing turbines for better fish passage conditions.

Simulation model for Francis and Reversible Pump Turbines

When simulating the dynamic behaviour of a hydro power plant, it is essential to have a good representation of the turbine behaviour. The pressure transients in the system occurs because the flow changes, which the turbine defines. The flow through the turbine is a function of the pressure, the speed of rotation and the wicket gate opening and is, most often described in a performance diagram or Hill diagram. In the Hill diagram, the efficiency is drawn like contour lines, hence the name. A turbines Hill diagram is obtained by performance tests on scaled model in a laboratory. However, system dynamic simulations have to be performed in the early stage of a project, before the turbine manufacturer has been chosen and the Hill diagram is known. Therefore one have to rely on diagrams for a turbine with similar speed number. The Hill diagram is drawn through measured points, so for using the diagram in a simulation program, one have to iterate in the diagram based on curve fitting of the measured points. This paper describes an alternative method. By means of the Euler turbine equation, it is possible to set up two differential equations which represents the turbine performance with good enough accuracy for the dynamic simulations. The only input is the turbine`s main geometry, the runner blade in- and outlet angle and the guide vane angle at best efficiency point of operation (BEP). In the paper, simulated turbine characteristics for a high head Francis turbine, and for a reversible pump turbine are compared with laboratory measured characteristics.

Dynamic Model of Kaplan Turbine Regulating System Suitable for Power System Analysis

Accurate modeling of Kaplan turbine regulating system is of great significance for grid security and stability analysis. In this paper, Kaplan turbine regulating system model is divided into the governor system model, the blade control system model, and the turbine and water diversion system model. The Kaplan turbine has its particularity, and the on-cam relationship between the wicket gate opening and the runner blade angle under a certain water head on the whole range was obtained by high-order curve fitting method. Progressively the linearized Kaplan turbine model, improved ideal Kaplan turbine model, and nonlinear Kaplan turbine model were developed. The nonlinear Kaplan turbine model considered the correction function of the blade angle on the turbine power, thereby improving the model simulation accuracy. The model parameters were calculated or obtained by the improved particle swarm optimization (IPSO) algorithm. For the blade control system model, the default blade servomotor time constant given by value of one simplified the modeling and experimental work. Further studies combined with measured test data verified the established model accuracy and laid a foundation for further research into the influence of Kaplan turbine connecting to the grid.

Differential Evolution-Based Identification of the Nonlinear Kaplan Turbine Model

In this paper, various new models of double-regulated Kaplan turbines are proposed, whose parameters are determined on the basis of field measurement data acquired during normal operating conditions. The model being identified is an extension of the nonlinear single-regulated turbine model obtained through an approximation function that defines the relationship between the wicket gate opening and runner blades angle. To determine the unknown parameters of the approximation function, a stochastic search algorithm called differential evolution (DE) is used. This paper focuses on the progressive development of the DE algorithm-based methods that are applied to determine different forms of the approximation functions, until an optimal form is attained that ensures the best possible agreement between the measured and calculated responses.

Wicket gate trailing-edge blowing: A method for improving off-design hydroturbine performance by adjusting the runner inlet swirl angle

At their best efficiency point (BEP), hydroturbines operate at very high efficiency. However, with the ever-increasing penetration of alternative electricity generation, it has become common to operate hydroturbines at off-design conditions in order to maintain stability in the electric power grid. This paper demonstrates a method for improving hydroturbine performance during off-design operation by injecting water through slots at the trailing edges of the wicket gates. The injected water causes a change in bulk flow direction at the inlet of the runner. This change in flow angle from the wicket gate trailing-edge jets provides the capability of independently varying the flow rate and swirl angle through the runner, which in current designs are both determined by the wicket gate opening angle. When properly tuned, altering the flow angle results in a significant improvement in turbine efficiency during off-design operation.

Simulation of Transient Flow in Hydroelectric Power Plants Using Unsteady Friction

In this paper the influence of surge tanks on transient flow generated by changing turbine gate opening has been numerically studied. For this purpose, the governing equations of transient flow are solved using the method of characteristics and considering unsteady friction. The surge tank and the hydraulic turbine are considered as internal boundary conditions. Comparison of transient results for pressure oscillations with the available experimental data shows good agreement. The surge tanks lower down the pressure levels at the upstream side of turbine and stabilize the pressure at the downstream side. Also, surge tanks delay the time occurrence of the maximum and minimum pressure. Finally, the effect of wicket gate closing followed by wicket gate opening on the so called speed no load operation (SNLO) on the transient flow is investigated and transient conditions improved by this sequence are found.

Notes: Turbine-Passage Mortality of Juvenile American Shad at a Low-Head Hydroelectric Dam

The immediate (1-h) turbine-related mortality of juvenile American shad Alosa sapidissima at the Hadley Falls Hydroelectric Station on the Connecticut River, Holyoke, Massachusetts, was estimated to be 0% ± 14.5% (95% confidence interval) at the 35% wicket gate opening and 2.7% ± 16.2% at the 100% opening. We used the HI-Z TurbˈN tag-recapture technique, which helped minimize control mortality and maximize recapture rates. Earlier literature estimates of turbine-related mortality (up to 82%) of juvenile alosids in passage through Kaplan turbines, in our view, were substantially overstated due to either low recapture rate, high control mortality, or both.

Effect of stay vane angle on the performance of hydraulic turbine.

The effects of stay vane angle on the turbine efficiency performance was investigated with a tandem circular cascade comprising stay vanes and wicket gates of a high specific speed Francis turbine. The velocity distributions around the stay various and wicket gates as wall as the variation of angular momentum along the streamline were calculated with the Flow analysis computer program based on the quasi-three dimensional Flow theory for the various combination of the stay vane setting angle and the wicket gate opening. A model Francis turbine having the same configurations of stay vane and wicket gate as those analyzed numerically was tested to measure the turbine efficiency and compare with the results of slow analysis. The measured results showed a good correlation with the calculated results and it made clear that the angle of stay vane affects the turbine efficiency in the region of large wicket gate opening.