Study On Theory And Technology Of Connecting PWR To Power Grids

With the advent of the energy crisis and increasing awareness of environmental protection, the proportion of nuclear power in the grid increases, which makes the studies on nuclear power plant operating characteristics of critical importance in safe and stable operation of power grid. The current PWR (AP1000) nuclear power plants were taken as the research subjects in the paper, the neutron dynamic process and heat transfer process in the reactor were anaylyzed, and the modeling of reactor core was implemented. Dynamic responses of the NPP core under the input of step disturbance of reactivity and cool-line temperature were simulated, and the simulationresults showed that, owing to the temperature effect and poisoning effect of the NPP core, reactor core is endowed with certain self-stability which protects the security of the NNP core and meets the requirements of the initial design. Being consistent with the historical data, the simulation further backs the proposed NPP core model. Based on the NPP core model, various models were integrated as a comprehensive package, including nuclear power plant hot and cold-line model, first loop coolant temperature model, U-tube temperature model, second loop vapor pressure model, first loop average temperature model, steam turbine and steam turbine governor system, and reactor control system. Through the simulation of single machine infinite-bus system, the conclusion was drawn that if the fault is cleared promptly and the NPP control system works well, the nuclear power plant can accept certain disturbances from the power grid. Moreover, this simulation validates the model.The nuclear power plant, when completed, generally keeps running at full capacity in order to obtain much greater economic benefits, and alternatively, ensure the stable operation of its own security unit. However, along with the rapid development of China's nuclear power construction, it is said that the power line will be heavily affected once the installed nuclear power capacity accounts for a considerable proportion of the grid, or fails to conduct certain load tracking. To ensure the power grid operated in a secure and stable manner, load tracking can be realized by using the power control system and regulating the reactivity of the reactor in PWR nuclear power plants. This paper deals with the fuzzy optimal power control system of boron concentration by using fuzzy controller as well as the rod speed and boron concentration. In doing so, the rod shift and boron concentration would be effectively regulated, Furthermore, the optimal choice is to be made to ensure that together with the increases or decreases of core power, Axial Deviation (AD) is guaranteed to change within a permitted range, and the reactor core power makes even changes to avoid the power distortion, local overheating, core melting and other hazardous incidents. The control system can accelerate the response speed by virtue of the power compensation channel, which has been defined by the Matlab for its excellent load tracking capacity. Connecting the self-defined control system model into the Nuclear Power Plant-wide System Model, simulation result demonstrates that the load tracking capability of the PWR nuclear power plant can meets the power requirements of the daily peak load.To connect the NPP into the whole power system, it is necessary to evaluate the reliability of the power system at the access point for NPP. This includes analyzing the intensity of electricity grid, and the reliability of it serving as an external power supply plant. The power grid malfunction or disturbance may lead to instability of the terminal voltage of NPP and grid frequency, which may cause the fluctuations in intrinsic parameters of nuclear power generating sets. Also the withdrawal of nuclear power units will cause the system to lose substantive active power, making the malfunction even worse. In the paper, the response of the intrinsic parameters of nuclear power generating sets is analyzed during the fluctuation of grid voltage and frequency. All the anticipatory accidents are found out by simulation when the criterion of NPP disconnection is met, and the probability of the ones is evaluated to determine whether the power grid meets the standard of IEAE. Different access ways of the NPP were simulated and stability margin of the access ways were analyzed based on the simulation results. The results demonstrated that in the three transmission modes:independent transmission mode, bundling power transmission mode, connecting the huge power supplier with sending terminal. The latter two is better than the first one. Whether to adopt the second mode or the third one depends on concrete issue.Although it has witnessed a huge fore-investment for nuclear power plant, more and more policy support from the government can be found due to its environmental-friendly concept, increasing security and stability, as well as frequency and peaking regulation. Economically, the traditional power supply planning has been shifted from individual optimization to multi-objective optimization by taking account of the ideas from the decision-maker and experts. However, it remains unsolvable since the multi-objective planning is labeled by high dimensionality, nonlinearity and multi-constraint condition. An improved Pareto fitness genetic algorithm (IPFGA) was proposed in this paper to deal with GEP problems. IPFGA is based on the basic concept of genetic algorithm, and decides the crossover rate and mutation rate by applying fuzzy system. In the genetic algorithm, double ranking strategy (DRS) is used to decide the fitness value, and uses population size adaptive density estimation (PSADE) to avoid premature local convergence, by which the same Pareto Front is obtained as other algorithms, and the effectiveness of the proposed algorithm is proved. Compared to other algorithms, IPFGA can effectively prevent genetic drift and maintain population diversity; in the meanwhile, it can improve the search efficiency, avoid regional optimal solution and at last, but not the least, promote the calculating speed. IPFGA can be easily applied to find the optimal solutions for various utilities via various expert opinions, and can be well and widely adopted. Based on safety stability conclusion, combining with fuzzy analytic hierarchy process and expert group decision-making system, the final access way is decided by comprehensive analysis and comparison of the NPP transmission mode. The ideas and methods are of important guiding significance at pre-planning of the connection with the power grid of NPP.