| Motor-driven systems are widely used in construction machinery,transportation,modern production and other fields.Motor power consumption is an important part of the country’s total energy consumption.The introduction of the frequency conversion control technology can greatly reduce energy consumption.However,during the operation of the system,there are frequent starting and braking states,accompanied by a large amount of regenerative braking energy,which is mostly consumed in the form of heat.If the braking energy is recovered,the system energy loss can be effectively reduced.At present,there are two commonly used methods of energy recovery: one is to feed the braking energy back to the power grid through the PWM rectifier unit,but this will cause the grid voltage to fluctuate and increase the harmonic content.The other is to recover and reuse the braking energy through the energy storage unit,which has a significant energy-saving effect and does not pollute the power grid,and has been rapidly promoted and developed.The energy storage unit includes power electronic converters and energy storage equipment.In energy storage equipment,supercapacitors have the advantages of high power density,fast response speed,and fast charging/discharging speed,so they are mostly used for the recovery and reuse of braking energy in motor-driven systems.However,in the process of braking energy recovery,if the energy storage unit is improperly controlled,the supercapacitor will not only absorb the excess energy of the DC bus,but also absorb energy from the power grid.Frequent energy conversion will cause unnecessary energy loss.In response to this,this paper proposes a method for improving the efficiency of a supercapacitor energy storage system used in motor-driven systems.The paper constructed a mathematical model of supercapacitor energy storage control for motor-driven systems,the topological structure and charging and discharging characteristics of supercapacitor energy storage system are studied,and the law of energy transfer and conversion of energy storage system by analyzing the energy flow mechanism of the system are sought.According to the system requirements,the overall control scheme is designed,and the parameters of the supercapacitor module,bidirectional DC/DC converter and filter components in the main circuit are calculated and selected.Analyzing the operating conditions of the motors when driving different loads,a state recognition controller is designed to realize the automatic switching between the buck and boost modes of the bidirectional DC/DC converter.Based on the study of traditional double closed-loop control,a multi-parameter energy coordinated control strategy is proposed,and a discrete control model is constructed.Through motor power prediction and tracking,and considering multi-parameters such as super capacitor side voltage and current,bus side voltage and current,the loss function is optimized real-time to ensure the best energy utilization efficiency of the system.The simulation and test platform for supercapacitor energy storage control of the motor-driven systems was built.Under the conditions of different load powers driven by the motor,the comparison under three control strategies of traditional double closed-loop control strategy,multi-parameter energy coordinated control strategy and energy consumption strategy was carried out respectively.The simulation and test results show that the energy-saving effect of multi-parameter energy cooperative control of supercapacitor energy storage system is significant. |
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