Yuanhang Dai

Dispatch Model of Combined Heat and Power Plant Considering Heat Transfer Process

Due to the coupling of its heat and power output, combined heat and power (CHP) has limited flexibility, which is one of the main reasons for variable renewable energy source (RES) curtailment problem in Northern China. Almost all the existing studies have modelled the CHPs output characteristics as a feasible operation region of electric power and heat power. However, only the extraction steam of a CHP unit that used for district heating can be controlled directly, without considering the extraction steams heat transfer process, the actual heat power output cannot be precisely decided. Thus this paper proposes a detailed CHP dispatch model based on the principles of heat transfer. A three-stage heat transfer model of the extraction steam is used to describe the heating process. Then, a joint dispatch model concerning CHP units, conventional thermal power units, and RESs is given. Finally, the impacts of different factors on the extraction steams heat transfer process and its influence for RES accommodation are analyzed. Results show that considering heat transfer process is essential in modelling the CHP plant that used for district heating, especially when the CHP plant is working at a status that deviates from the rated one significantly.

Modeling and analysis of electrical heating system based on entransy dissipation-based thermal resistance theory

Electrical heating with thermal storage using surplus wind power is now promoted in northern China for wind power accommodation and clean heating. This paper presents the results of a study on the modeling of the electrical heating system. Based on the entransy dissipation-based thermal resistance theory, heat source, heat exchanger, pipeline and heat load in the system are modeled from the perspective of thermo-electricity analogy method and two different pipeline models are given. The electrical heating system is a controllable load enhancing the flexibility of the power system and the model can effectively describe its dynamic response characteristics.

Integrated Dispatch Model for Combined Heat and Power Plant With Phase-Change Thermal Energy Storage Considering Heat Transfer Process

Combined heat and power (CHP), with its limited flexibility, is one of the leading causes for the curtailment problem of variable renewable energy source (VRES) in Northern China. To increase the flexibility for CHP, thermal energy storage (TES) is considered to be an effective solution, and a phase-change TES demonstration pilot project is now being constructed in Northern China. Almost all the previous studies have modeled the TES device without considering the heat transfer process, which is a main constraint in thermal system analysis. Thus, in this contribution, we consider the heat transfer process for the phase-change TES device installed in a CHP plant based on the steams three-stage heat transfer model and the entransy dissipation-based thermal resistance theory. An integrated electrical–thermal dispatch model concerning conventional thermal units, VRESs, and CHP units with phase-change TES device is given, and an iteration method for solving this nonlinear programming problem is proposed. Case studies show that it is vital to consider the heat transfer process in the modeling of CHP plant with phase-change TES device, and it has significant influence on the flexibility that the TES device can provide when the working conditions vary.

A dispatch method of combined heat and power plants with heat storage facilities for wind power accommodation

An effective way to solve the problem of wind power curtailment is to install heat storage (HS) facilities in CHP plants. However, the existing power grid does not have the ability to schedule the heat storage facilities. In this paper, we have developed the combined heat and power dispatching system to schedule the power plants as well as the heat storage facilities for the maximum effect of wind power accommodation. The results show that cooperating with the existing scheduling system, the combined heat and power dispatching system has fine-tuned the initial schedules with the adjustment of the heat storage facilities to achieve the desired effect of improving the wind power consumption. Meanwhile, the maximum heat storage amount of the HS facility that limits the capacity of increasing wind power accommodation. Whats more, the capacity can be affected when the heat load varies seasonally owing to the external characteristics of the CHP unit.

Active and Passive Thermal Energy Storage in Combined Heat and Power Plants to Promote Wind Power Accommodation

AbstractEmploying thermal energy storage (TES) for combined heat and power (CHP) can improve flexibility in an integrated electric-thermal system (IETS) and therefore is beneficial to the accommoda...

Study on the mechanism of transient voltage stability of wind power with power electronic interface

Voltage stability is an important issue to be considered in power system with large scale wind power integration. The mechanism of transient voltage instability induced by wind power is studied. A variable speed wind turbine can control the power rapidly and flexibly with power electronic convertors. The fast dynamics related to power electronic control transients can be neglected, and the wind power is simplified to static power injection model in electromechanical transients. The wind power is modelled with power balance algebraic equations, and the system dynamic equations are differential algebraic equations. The trajectory encountering a singular point corresponds to transient voltage instability of the system, and at this point the power balance equations of wind power become insoluble. Simulation results validate the mechanism, and reveal the variation of instability mode of a wind-thermal-bundled sending system. As the proportion of wind power increases, the instability mode of the system changes from rotor angle instability dominated by synchronous generator to voltage instability dominated by wind power.