基于运行工况的低水头水轮发电机不圆度分析

Analysis on out-of-roundness of low-head hydrogenerator under operation condition

由于结构的特殊性,农村电网中低水头、小容量发电机在运行中圆度变化较大,影响着发电机的稳定性。为了改善该类型发电机运行品质,提高低水头水轮发电机可靠性,该文针对发电机运行参数进行数据分析、并进行理论解析方程及ANSYS仿真分析计算,对造成发电机不圆度机理进行研究,发现作用在低水头水轮发电机特殊结构上的不平衡重力及交变离心力导致发电机偏心,从而造成发电机不圆度增大。同时偏心引起的不平衡磁拉力对机组稳定性影响较大,反过来不平衡磁拉力又使发电机不圆度增大。依据该文研究结论提出了低水头、小容量发电机安全运行措施,经过实际运行考验,证实运行效果比较理想。该研究可为农村小水电发电机安全运行提供一种解决方法。

Low-head hydro-generators are an internationally recognized renewable green clean energy with the most advantages in China. At present, hydro-generators operating in the countryside with electrified wire netting are generally a horizontal structure with a low-head and small capacity. With the increase of low head hydroelectric generating turbines operating in the river, there still exist different problems in the various links. However, a relatively short history of the design, manufacture, installation, operation and maintenance of low head hydraulic turbines may easily lead to the increase of roundness deformation of the generator in operation. Field technicians usually do nothing more that an analysis of the structure and operating conditions. Moreover, the research by experts and scholars the problems are limited. The generator related accidents are more common both at home and abroad, and have become more and more serious. This paper studied this problem on the practical side. The existence of gravity and centrifugal force during operation creates eccentricity and an uneven air gap in the low head hydraulic generator, forming an unbalanced magnetic field which leads to an unbalanced magnetic pull. The effect of the alternating load finally not only creates an increase of the roundness deformation of the generator stator and the rotor, but also creates a torsional bending of the generator, increasing vibrations and possibly a generator fatal“friction”accident. This paper took unit # 1 at the Chaijiaxia hydropower station on the Yellow River as the research object through the parameter analysis of the generator eccentricity and the air gap, the exciting current in steady and transient states and the loss of excitation in generator, and the generator temperature, including the change law of unbalanced electromagnetic force, axis changes, torsional bending, vibrations, and the roundness deformation. On this basis, by studying the generator magnetic force, torque, analytical equations of coupled bending, and torsional vibrations of the rotor, this paper described, the cause of the change of the generator roundness deformation through the qualitative analysis of the gas gap, unbalanced magnetic pull, as well as the generator operation stability under the condition of static eccentricity, eccentric motion and eccentric vibrations. It undertook a quantitative analysis of the variation of the generator air-gap and magnetic pull that influenced the roundness deformation, and the cause that produced vibration, overheating, and fatigue in the load condition via finite element calculation. According to this research conclusion, running measures have been put forward to make the generator run in its optimal condition, and the obvious effect has been obtained. Moreover, the theoretical basis, the analysis methods, and operation mode are provided to solve the problem of the roundness deformation in a low head hydraulic generator.