Topology And Modulation-control Strategy Of PMSM Three-phase Three-level DC-AC Converter For Full Electric Vehicle

Permanent magnet synchronous motors(PMSM)with high efficiency and power density are widely used in full electric vehicles.The energy source of PMSM is mainly limited by the storage capacity such as battery.On the premise of ensuring safety,improving the overall performance of the control system to increase the endurance mileage puts forward higher requirements for the converter responsible for signal source conversion and its modulation and control strategy.Therefore,this topic takes the NPC(neutral piont clamp)three-level DC-AC converter controlling PMSM as the research object.Based on the three-level,there are two-level and three-level topologies,DC voltage linear region modulation strategy,system stability and reliability control strategy,and parameter identification strategy affecting system control performance are studied.The main research work and results are as follows:1.The three-phase two-level topology and space vector modulation algorithm are studied,and the two-level topology is improved.The region sequence judgment and the optimal modulation algorithm of the action time are proposed.The modulation steps of the traditional modulation algorithm are simplified and the calculation method of the space vector action time in the region is optimized.The improved two-level topology provides the conditions for the three-level and two-level modulation conversion algorithm,and the optimized modulation algorithm saves hardware resources.2.The topology of traditional D-NPC(Diodes Neutral-Piont-Clamped)and A-NPC(Active Neutral-Point-Clamped)three-level converters is studied.The ID-NPC(Improved-Diodes Neutral-Piont-Clamped)and IA-NPC(Improved-Active NeutralPoint-Clamped)topology are proposed,and the switch loss distribution is analyzed.The distribution of heat loss of converter with ID-NPC and IA-NPC topology is more uniform.3.The principle and steps of traditional modulation algorithm of three-level SVPWM are analyzed.The optimized three-level angle sequence synthesis modulation step,improved the synthesis algorithm in the process of vector synthesis,proposed 2× amplitude substitution using the short vector synthesis algorithm which has fewer passing sectors and 1/2× amplitude substitution using the medium and long vector synthesis algorithm which has more passing sectors.When using the 2× amplitude substitution algorithm,the linear modulation region is increased to 1.103 times.4.Based on the analysis of two-level and three-level topology,combined with different level characteristics,a three-two-level modulation conversion strategy based on loss allocation and fault tolerant function ID-NPC topology is proposed.This modulation strategy improves the reliability of the converter.5.In order to overcome the influence of operation state and nonlinear factors on PMSM parameter identification and improve the system stability,an improved double closedloop PID predictive control strategy with least square full-parameter identification is proposed.By controlling the changing rate of current and voltage,the sampled data is selected for the first time,and twice sampling for full rank is to solve the estimated state equation,then the improved least square parameter identification method is improved.The improved least square method can only identify the flux linkage,resistance and inductance.The control strategy also needs the moment of inertia,torque,damping coefficient and other parameters.With the introduction of constrained multi-objective optimization full parameter algorithm,the required parameters are modified secondly.Based on the results of full parameter correction,the structure of generalized predictive control loop is used to replace that of speed loop in the double closed-loop PID control strategy,so the double closed-loop PID predictive control strategy is improved.Using ID-NPC topology,2 × amplitude substitution algorithm,three-two-level modulation conversion strategy and double closed-loop predictive control strategy of improved least squares full parameter identification,the simulation analysis is carried out in Matlab environment,and the simulation platform of three-level DC-AC converter control system of full electric vehicle PMSM is built for experimental verification.