Optimal Design Of Downhole Mud Turbine Permanent Magnet Synchronous Generator

In the process of oil drilling,the LWD test instrument can measure the feedback well slope,azimuth,downhole temperature,drill pipe torque and other parameters in time,which is the safety guarantee for the smooth drilling project.Lithium battery is used as power supply for most of the testing instruments while drilling,which has many disadvantages such as low power supply,low safety degree and serious pollution.The power supply mode of permanent magnet synchronous generator can overcome many defects brought by lithium battery power supply,improve the power supply stability,and provide corresponding guarantee for the smooth operation of drilling engineering.In the process of oil drilling,the circulating mud is usually used to cool and lubricate the drill bit.If the pressure energy and potential energy contained in the flowing mud are converted into electric energy,the purpose of energy recycling,energy saving and emission reduction can be achieved.In this paper,a downhole mud turbine permanent magnet synchronous generator which relies on circulating mud for power generation is taken as the research object.The purpose of reducing the torque of the permanent magnet motor groove,improving the motor performance and improving the power generation efficiency is achieved by improving the motor parameters.Start with downhole mud turbine permanent magnet synchronous generator as the prototype,established its global parsing model under no-load and load state,in every area of motor vector magnetic potential equation is established,in each region of the variable separation method is adopted to solve the partial differential equation and get the analytical solution,analytical solution model reflects the motor structure parameters on the effect of magnetic field.The analytical results are compared with the finite element results to verify the rationality and accuracy of the established analytical model.Secondly,based on the analytical model and maxwell tensor method,the analytical expression of the motor’s groove torque is derived,and a global analytical simulated annealing algorithm is proposed.Taking the slot width of motor stator,pole arc coefficient,permanent magnet thickness and air gap length as optimization variables and the amplitude of slot torque as optimization objective,univariate optimization experiment and multivariate optimization experiment were conducted respectively.The optimization results showed that:Different optimization experiments can reduce the motor groove torque in different degrees,but the multi-variable optimization effect is higher than the single variable optimization effect,and the amplitude of the motor groove torque decreases more obviously.According to the optimization of different experimental results from the modeling of motor,and respectively for the optimized the model of motor no-load air gap flux density,no-load induction electromotive force,the higher harmonic content in the air gap flux density harmonic condition compared with before optimization,in this paper,a new global parsing-simulated annealing algorithm for motor optimization effect significantly.Again,the efficiency of the permanent magnet synchronous generator is one of the important indices for objective response of motor performance,the motor efficiency operation are generally based on the finite element model,however,the global analytical object-the application of simulated annealing algorithm for the analytical model,so we can not directly on the motor efficiency optimization design,so this article use taguchi method of motor efficiency optimization.Taguchi algorithm optimization method for an experimental project in nature,and therefore need a lot of engineering experiment data as the basis of analysis,in addition,this algorithm is a kind of local optimization algorithm,compared with the global parsing-simulated annealing algorithm the optimum interval global optimization algorithm are smaller,so it is more convenient for engineering experiment,in view of the above points,The optimization experiment of motor efficiency in this paper is based on finite element calculation model.Finally,through the mean analysis,factor effect analysis and variance analysis of the experimental results of each group,the optimal parameter combination of motor design was found,which greatly reduced the motor loss,significantly improved the efficiency,and significantly improved the motor performance.