| Electric motors have been widely used in our daily life,such as household appliances,electric vehicles with increasing share today,and even medical and office equipment.Before the motor is officially put into the market,it needs to be debugged to test the effectiveness of its control strategy.At present,the most widely used test method is to connect the motor control system to the traditional motor towing test platform.However,the towing test has high cost,long cycle,and needs to constantly replace the driver to be tested.This device is also known as a motor simulator.Traditional motor simulators often use two-level interleaved parallel converter to simulate the input and output characteristics of real motors.However,two-level interleaved parallel converter cannot realize higher precision motor simulation due to the limitations of its structure,and also cannot realize the motor simulation under high voltage application scenarios.Three-level interleaved parallel converter structure can effectively solve the above problems.In this paper,the control strategy of flying-span capacitive three-level interleaved shunt converter is studied.This paper analyzes traditional modulation strategies and propose new control schemes to improve the control stability and response speed of the system.In this paper,the operating principle of flying-span capacitor three-level circuit is deeply analyzed,and the switching states of different branch structures are mainly explained.The influence of different switching states on branch current and crosscapacitor voltage of flying-span is clarified by establishing branch voltage equation.Then,based on the analysis of the branch,the mathematical model of the three-level interleaved parallel circuit of the take-off trans-capacitance is established,and the relationship between the branch current ripple and the output current ripple as well as the mathematical relationship between the input and output voltages is derived.At the same time,the relationship between common mode and differential mode current of branch and different parameters of interleaved shunt converter is explained in the form of relation.By analyzing the current imbalance between branches of interleaved parallel circuit,combining the traditional control strategy of flying-span capacitive three-level interleaved parallel circuit and the existing control strategy of two-level interleaved parallel converter,a new control strategy based on sorting algorithm is designed for flying-span capacitive three-level interleaved parallel converter.Then,the causes and solutions of flying-span capacitance voltage deviation problem in the branch of converter are analyzed.Finally,the proposed control strategy is improved to realize the adjustment of flying-span capacitance voltage under the premise of steady-state operation of the system.In the following paper,the dead-zone continuation problem in the converter is analyzed,and the specific value of the output voltage error caused by the dead-zone continuation is derived,and the corresponding compensation for the error is carried out.In view of the dead-zone compensation scheme mentioned above,the paper establishes the simulation model of staggered parallel converter,and makes a comparative analysis of the dead-zone compensation effect.Verify the effectiveness of the proposed deadtime voltage compensation scheme.In order to verify the superiority of the proposed new control strategy,a flying span capacitive three-level interleave parallel converter and a semi-physical simulation platform based on RT-LAB were built.The control strategy proposed in the paper was tested in practice,and the experimental results proved the effectiveness of the proposed control strategy. |
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