| Permanent magnet machines has the advantages of high efficiency,high power density and quick response speed.At the same time,the PWM rectifier can be used for energy feedback,which can reduce the energy consumption of the drive system.The requirement of good dynamic performance and Bi-directional energy flow could be satisfied for special application scenarios.It has been applied in elevator,lifting,construction machinery and other condition.With the development of science and technology,higher standard requirements are put forward for permanent magnet motor drive system.However,there is still a big gap between China and developed countries in the high-performance permanent magnet motor drive system products.Therefore,it is of great practical significance to optimize the control performance of the drive system to improve the competitiveness of products and meet the market demand.In this paper,the common three-phase or six phase permanent magnet motor drive system is taken as the research object.The research includes model predictive control PWM rectifier current harmonic suppression,MEPA control based on virtual signal injection,capacitor current ripple suppression based on recombination PWM sequence control,and continuous overmodulation control based on switch hold angle.The specific research contents and innovations are as follows:(1)The harmonic suppression method of PWM rectifier based on model predictive power control is proposed,which solves the problem of current and power fluctuation and large amount of calculation in model predictive control.The mathematical model of grid inverter active and reactive power variation is obtained followed the model predictive power control method.The set cost function is used to select the active voltage vector and the duration is calculated according to the deadbeat control principle.The reason and mechanism of the larger power and current ripple phenomenon are analyzed comprehensively.The relationship of the power variation under different voltage vector is given and their transfer equation between the adjacent voltage vector can be obtained,thus the new duration can be obtained easily.When the duration is less than zero,an improved modulation control method is proposed by selecting the adjacent vector and new duration.With this method,the situation for duration less than zero is avoid.The simulation and experimental results verify that the proposed method can depress the ripple in power and current and reduce the calculation burden effectively.Thus the grid inverter's control performance and efficiency is improved.(2)A virtual signal injection method for the high efficiency control of inner permanent magnet synchronous machine drives is proposed.It provides a new idea for the high efficiency control for the permanent magnet machines drive system.The proposed method is suitable for searching the optimal current angle for the maximum efficiency per ampere control method for the inner permanent magnet synchronous drives and this method can contribute to realize the maximum efficiency operation for the machine system under the set current amplitude.For the conventional look-up table method,it requires huge experimental data,which would take much time and occupy large computational memory.While the online signal injection method would cause the additional loss and have the low convergence rate problems.Firstly,the system(the inverter and machine)loss and efficiency models are built.Secondly,a virtual signal injecting control scheme for the high efficiency control of inner permanent magnet synchronous machine drives is proposed.The loss and efficiency model after the signal injection can be derived.Though this method,the optimal current angle can be obtained to realize the maximum efficiency operation.Finally,the experiments verify that the proposed method is easy to implement and has the fast convergence rate.It could effectively improve the inner permanent magnet synchronous machine drive system efficiency.(3)In order to reduce the ripple of DC bus capacitance current,a dual three-phase permanent magnet motor drive control strategy based on recombined PWM sequence is proposed.Multi-phase permanent magnet machines has the advantages of high fault-tolerance and reliability performance.The multi inverters drives structure,paralleled on the same dc-link capacitor,are normally used to provide the support for stable dc-link voltage.However,the multi inverters parallel operation would cause the large current ripple in the dc-link capacitor,thus would increase the capacitor current stress and temperature rise.It would shorten the lifetime of the capacitor and reduce the reliability of drive system.In order to solve this problems,an optimal switching sequence control method for shifted 30°dual three phase machines drives is proposed.The dc-link current,correspondingly the voltage vector for inverter 1 and inverter 2,are reordered according to the current amplitude.The vectors for two inverters are rearranged which makes the dc-link current ripple smallest.The experiments shows the proposed method can reduce the dc-link current ripple effectively,and it has a slight effect on the current harmonic performance.Therefore,the proposed method can prolong the dc-link capacitor lifetime and improve reliability of the multi phase permanent magnet machine drive system.(4)The overmodulation control technology of dual three-phase permanent magnet motor based on switch hold angle control is proposed,which can improve the utilization of DC bus voltage and the maximum output torque control performance of motor system.When the requirement of high torque,the dual three phase permanent magnet machines work under overmodulation region,which could improve the maximum output power of the machine drive.However,the implementation process of the existing overmodulation technology for dual three phase machine is complex,and its performance can not be guaranteed.Therefore,in order to achieve maximize the DC bus voltage utilization rate of six-phase permanent magnet machine drive system easily,an overmodulation control strategy based on two three-phase converters are stuied.Firstly,the principle of three-phase inverter overmodulation control is analyzed,and the relationship between the switch holding angle and the modulation ratio is derived;then,the relationship of voltage vector in the double Y shift 30° six-phase motor system with is deduced,and the overmodulation control method under the control of the sixphase motor system is obtained.Finally,the effectiveness of the proposed algorithm is verified by experiments. |
PDF Full Text Request