Condensate Throttling Research Articles

Theoretical modeling and investigation of the influence of deaerator on the transient process in power plants

Deaerator is one of the most important equipment for steady state and dynamic operation of power plants. The deaerator energy storage utilization process is one of the most essential ways to enhance the variable load rate of power plants. The purpose of this study is to improve the dynamic simulation performance of the deaerator during unit load changes by constructing a more reasonable deaerator model, aiming to provide guidance for practical operations. In this paper, a thermal mass microelement algorithm is proposed for the heat transfer between droplets and steam in the deaerator, followed by segmental modeling of the deaerator. By comparing with the operation data of a power plant, the steady state operation error of the deaerator model is within 0.6 %. Subsequently, the unit load variation process is simulated and the dynamic variation accuracy of the model proposed in this paper is enhanced by 1–2 % compared to the lumped parameter model. The dynamic characteristics of the deaerator are obtained by simulating the step and ramp changes of the deaerator boundary conditions and the deaerator start-up process. In addition, during the simulation of condensate throttling, the maximum power of the unit using the deaerator model in this paper is 0.2–1.5 MW larger than that of the lumped parameter model.

Basic study of condensate throttling operation for nuclear power plants

Basic study of condensate throttling operation for nuclear power plants

The depth utilization method of condensate system’s energy-storage to improve large turbine generator units’ load response characteristic

Load response characteristics of high thermal power units are critical to a safe and efficient grid-connected utilization of large-scale renewable energy with strong randomness. A condensate throttling regulation was reported to improve the units variable load rate. However, it is not verified by tests in different types of units. In the paper, the influence of the storage capacity of the steam generator’s condensate system on the load response characteristics is studied for four subcritical 330 MW heating units by simulation and an experimental test. The result shows the feasibility of the condensate throttling regulation, which is of great value to the practical engineering application in the future. In addition, this paper obtains the condensate regulation potential of units under different power generation load conditions through simulation and actual tests. These real data will help other units of the same type to carry out similar modifications or tests.

Flexibility enhancement versus thermal efficiency of coal-fired power units during the condensate throttling processes

The improvement in operational flexibility of thermal power plants plays an essential role in the stable and safe operation of large-scale power grids. Condensate throttling is an effective method for enhancing the operational flexibility of thermal power plants, but it inevitably influences their thermal efficiency. In fact, the entire condensate throttling process consists of two stages: the condensate throttling process and the recovery process of the deaerator water level. To evaluate exergy efficiency during the entire condensate throttling process, dynamic models of a condensate throttling system were developed and exergy analysis was performed. Results indicate that additional exergy losses occur during the condensate throttling process. The cold end system is the component that exhibits the highest additional exergy loss (64.89%), followed by the deaerator (40.49%), heaters (4.82%), and turbines (−10.20%). Operational flexibility is in contrast with thermal efficiency during the condensate throttling process. The cycling and total exergy losses of the system increase with an increase in the condensate throttled ratio. Cycling loss can be decreased by a maximum of 51.46% by selecting an appropriate condensate water adjustment strategy during the entire condensate throttling process.

Modeling condensate throttling to improve the load change performance of cogeneration units

The operational flexibility of coal-fired units plays an important role in the stable and safe operation of power grid under fluctuant renewable power resources. As they represent a large proportion of coal-fired units, cogeneration units need to be studied to improve the load change performance. The purpose of this study is to activate the energy storage of regenerative system by condensate throttling, which can improve the load change performance of cogeneration units. The static and dynamic models of condensate throttling were established through a mechanism analysis. And a 350 MW cogeneration unit was chosen as a case study to simulate the dynamic model under 10 operating conditions with different condensate throttled flowrates. The results reveal that the load change performance of condensate throttling is more improved when the output power is higher, the increased condensate throttled flowrate can further improve the load change performance. Moreover, the increased operational flexibility can be obtained when cogeneration units working under the sliding pressure operating condition. Finally, the maximum duration and the 1-min output power increment are also evaluated. The maximum duration is mainly influenced by the condensate throttled flowrate. And the maximum 1-min output power increment is between 4.972 MW and 22.999 MW.

An Intelligent Dual Optimization Approach for Improved Load Following of Supercritical Power Unit Based on Condensate Throttling

In modern real-time unit load scheduling, it is unavoidable for large-capacity supercritical (SC) units to participate in peak-load regulation with automatic generation control (AGC), which raises the requirements for load control of a large SC power unit. With only the traditional coordinated control system, it is easy to fail in meeting the requirements of rapid load-changing and cause large fluctuations for main steam pressure and temperature. Condensate throttling technique, as an emerging new technology for rapid adjustment of unit load, has attracted much attention in recent years. This paper develops a neural network based unit load prediction model which takes condensate throttling into account for a 600 MW SC power unit. An intelligent dual optimization approach is then developed, which uses the load prediction model twice, first to optimize the deaerator valve opening during the initial load-changing stage for fast load following, and then to optimize the turbine valve opening during the later condensate flow recovery phase to keep the load-following accuracy. Simulation tests show that the proposed approach can greatly improve the unit load dynamic response in speed and control accuracy, thus effectively improve the unit load adaptability to AGC.

Research on Design Method of Coordination Control System for Ultra Supercritical Power Generation Unit Based on Condensate Throttling Security Control Strategy

Condensate throttling security control strategy is introduced for the problems existing in ultra supercritical power generation unit. Its load and control method are analyzed and discussed. The related results show that this control strategy not only solves the unit pressure fluctuate wildly as well as but also improve the unit operation efficiency.

An experiment-based model of condensate throttling and its utilization in load control of 1000 MW power units

Coal-fired power units are important to stabilize the grid fluctuation especially for the electrical power system with a large proportion of renewable sources. The unit load change speed and range controlled by traditional coordinate control system has become more and more insatiable for the integrations of fluctuant power sources. Condensate throttling is an efficient way to utilize storage energy of units, the mechanism analysis of regulating range and regulation maximum period in wide range of operating condition is proposed, and dynamic model in varying operation conditions is established through lots of trial experiments in a 1000 MW coal-fired power plant, the parameters of model are also discussed in different operating situations. A novel coordinate control system combining traditional coordinate control and condensate throttling system is proposed and the control performance in different regulating rates is investigated, the results and load distribution analysis proved that novel strategy achieve a superior fast response ability and static accuracy.

Improved boiler-turbine coordinated control of 1000 MW power units by introducing condensate throttling

Improving the operating flexibility of coal-fired units has become more and more important since an increasing number of fluctuant renewable energy connected to the power grid would make the power system easily unstable. However, it is difficult for the 1000MW power units to improve their load change capability because the large delay of their once-through boilers. In this paper, the condensate throttling and coordinated control are combined to accelerate the load response, and a 4-inputs 3-outputs control model is firstly set up. Then a dual controller is designed to realize the combination control of fuel flow and condensate water flow on turbine load; also, the dual controller can recover the condensate water flow and deaerator level to their former values. Furthermore, the feedforward control based on stable inversion is developed to advance the response of fuel regulation, and the main steam pressure control and separator outlet enthalpy control are decoupled for convenient control. Finally, simulation tests and analyses on a 1000MW unit are carried out to prove the effectiveness of our strategy.

Modeling for condensate throttling and its application on the flexible load control of power plants

Most power associations have made stringent requirements on the load change speed and range of thermal power plants. However, it has become more and more difficult to improve their load change capabilities just through coordinated control system because of boiler's large delay. Condensate throttling is one of the few efficient methods which can be used to rapidly activate stored energy enough for unit load support. We first set up its static and dynamic models. Then we design an improved load control strategy by combining traditional coordinated control with condensate throttling control. This strategy can also recover the balance of deaerator level to prepare for the next load-change use. Finally, simulation results reveal that our strategy has much better performance than traditional coordinated control.

Dynamic model for controller design of condensate throttling systems

Improving the load adjustment rate of coal-fired power plants in China is very important because of grid load fluctuations and the construction of new large-scale power plants connected to the country׳s power grid. In this paper, a new application of condensate throttling system for rapid load adjustment is proposed on the basis of the characteristics of turbine-stored energy. To ensure effective and safe operation of the condensate throttling system, a non-linear control model is derived through reasonable simplifications of fundamental physical laws, and the model parameters are identified using experimental data from a 660MW supercritical coal-fired power plant. The model outputs are compared with actual measured data for different unit loads. Results show that the established model׳s responses strongly correlate with the actual unit׳s responses and can be used for controller design.

Optimization of an air-cooling system and its application to grid stability

Because of the energy shortage, fluctuation of grid load and preparing for large-scale new energy power plants connected to the grid, it is important to ensure high efficiency of coal-fired power plants and improve the adjustment range of unit loads in China. In this research, based on the characteristics of direct air-cooling systems, calculation of the heat transfer coefficient and exhaust steam enthalpy in a variation condition is put forward, and a cold-end adjustment system using the frequency conversion adjustment of axial-flow fans is proposed to improve the efficiency of power plants and the capability of thermal power plants to execute rapid load changes. A case study on the cold-end adjustment system shows that the adjustment range of a direct air-cooling unit is affected greatly by ambient temperature; therefore, to overcome the shortcomings of a direct air-cooling system, the authors combine a cold-end adjustment system with a condensate throttling system, and thus rapid and broad-load-range adjustment of coal-fired power plants is achieved.

Simple Models for Model-based Portfolio Load Balancing Controller Synthesis

Abstract This paper presents a collection of models of so-called ‘effectuators', i.e., subsystems in a power plant portfolio that represent control actions with associated dynamics and actuation costs. These models are derived in order to facilitate higher-level model-based control synthesis of a portfolio of generation units existing in an electrical power supply network, for instance in model-based predictive control or declarative control schemes. We focus on the effectuators found in the Danish power system. In particular, the paper presents models for boiler load, district heating, condensate throttling and wind turbine effectuators. Each model is validated against actual measurement data. Considering their simplicity, the models fit the observed data very well and are thus suitable for control purposes.

Improved maneuverability of power plants for better grid stability

The interaction between power systems and power plants is becoming more and more important as power system operators look at the properties of power plants with respect to their response and maneuvering capabilities, whereas plant operators look at the expenses that are incurred with frequency support operation. The new unit control method presented here is designed to improve power plant response. The thermodynamic losses usually associated with rapid frequency control can be avoided if, in addition, condensate throttling is used. The proposed method has been proved over several years. Experimental results are presented, demonstrating the validity of the approach.

Improved Maneuverability of Power Plants for Better Grid Stability and Economic Dispatch

Abstract The interaction between power systems and power plant becomes more and more important as power system operators look at the properties of power plants with respect to their primary and secondary control capabilities whereas plant operators look at the expenses that are incurred with frequency support operation. The New Unit Control method presented guarantees an exceptionally careful operation of the plant. Scheduled load variations will be realized according to the natural transfer response. Because there are less movements of the actuators you have less wear and tear on the plant. The smoother pressure and temperature control reduces the thermal stress of the plant thus increasing lifetime. The firing will become even more smooth if Condensate Throttling (C.T.) is used. C.T. is used not only on major frequency drops, but also during normal operation. Overfirring with the fuel controller can then to a large extend be reduced and replaced by the load reserves of the condensate throttling circuit. The New Unit Control has been proven over several years. It can be installed instead of any conventional unit control in any fossil-frred power plant. Experimental results are presented demonstrating the validity of the approach.