| AC drive control systems are widely used in electric vehicles,CNC machine tools,and other fields.These applications have strict requirements on the current reconstruction accuracy,control reliability,and space volume cost of the electric drive system.Therefore,the AC drive system needs to improve control reliability while reducing the volume and cost of the control system.Aiming at the problems of low reconstruction accuracy,poor control performance,and inability to realize power tube fault detection when using the Space Vector Pulse Width Modulation(SVPWM)method to realize the DC bus single-sensor phase current reconstruction technology,this dissertation carried out the following research.The principle of phase current reconstruction technology of DC bus single-current sensor is analyzed,the concept of minimum current observation window duration is proposed,and the unobservable areas existing in the traditional SVPWM method to realize single-current reconstruction technology are classified and divided.In order to eliminate the unobservable area,a non-zero complementary voltage vector is used to replace the zero vector in the sector boundary and low modulation area,the SVPWM strategy is used in the rest area,and a mixed space vector pulse width modulation(MSVPWM)is proposed.Single current sensor phase current reconstruction method.The current observation window time is extended to ensure accurate current sampling in the entire space voltage vector plane.The adjustable range of the MSVPWM method and the relationship between the increase in rotational speed and switching loss at different switching frequencies are further analyzed.Simulation and experiments verify that the proposed MSVPWM method can accurately reconstruct the phase current in the entire space vector plane,and the reconstruction error is less than 3.7%,the total harmonic distortion content of the phase current is controlled by 4.02%,and the switching loss is increased to the maximum of 2%.In order to reduce the influence of the zero-point drift of the DC bus single current sensor on the phase current reconstruction accuracy,the causes of the zero-point drift error and the generation mechanism of the amplification effect were revealed,and an error self-correction method was proposed based on the MSVPWM strategy.By inserting two complementary effective voltage space vectors in each carrier cycle in the unobservable region to replace the zero-voltage vector,and double sampling the inserted complementary voltage vector and the effective voltage vector used for reconstruction,a reliable sampling window is provided for the current sensor,the current unobservable area is eliminated.At the same time,the drift error is calculated using the current information collected by the complementary vector,and the selfdetection and self-correction of the current zero-point drift are realized.Simulation and experiments verify that the reconstructed phase current error after self-correction is less than 3.56% under dynamic and static conditions,which can provide a reliable reconstructed current for the control system.Aiming at the fault of inverter power tube,the causes and characteristics of power tube drive signal fault,short-circuit fault,and open-circuit fault are analyzed,and it is clarified that opencircuit fault is the primary fault type of inverter power tube,and a method based on MSVPWM strategy is proposed.Single-sensor normalized average current absolute value power tube opencircuit fault diagnosis method,using the reconstructed three-phase current information after the fault occurs,calculates the normalized average current absolute value through Park transformation and compares it with the given fault diagnosis parameters to obtain the fault information.Finally,simulation verified that the proposed fault diagnosis method could quickly and accurately determine the open-circuit faults of various inverter power tubes,which provides an adequate basis for further improving the reliability of the control system. |
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