| Since the beginning of the new century,the rapid economic development of our country is closely related to oil consumption.In order to respond to the development concept of carbon neutralization and carbon peak,electric workover rig have been widely used.However,most of them work in the limited scale of the grid environment,unable to meet the needs of each power level,so when the load is too large,it will threaten the safety of the network electrical transformer,the use of brake resistance to consume feedback energy will cause the waste of electric energy,load changes caused by busbar voltage fluctuations will affect the normal operation of the system.To this end,the super capacitor is added to the AC-DC-AC system of the electric workover rig,and the energy flow of the electric workover rig can be controlled by charging and discharging.First of all,combined with the working condition of the electric workover rig,the super capacitor energy storage system realizes the protection of the grid transformer,the stability of the busbar voltage,the capacity regulation of the super capacitor and the recovery of the braking energy through mode switching control.Then the circuit topology of the system is modeled mathematically,the working condition parameters and security threats to the system are analyzed when each working mode is switched.Secondly,the inductive current of charge and discharge of super capacitor is selected as the control object,and the fuzzy flexible switching control strategy is proposed.In this method,the magnitude proportion of inductance current in the last working period and the magnitude proportion of slope corresponding to its change are taken as inputs,and membership function and fuzzy rules are designed according to the control effect.Mamdani algorithm is used for fuzzy reasoning to output the change of inductance current in this working period to realize adaptive dynamic tracking of the given value after mode switching.In the process of flexible switching,the change rate of inductance current is always controlled within the set threshold range,which restrains the impact on the power switch tube and the network transformer and ensures the safe operation of the system.Then,in order to meet the flexible requirements of each working mode switching of the energy storage system,the flexible switching time,the curvature of inductance current in each working period and the square of the difference of inductance current change in each working period were selected to measure the speed of the control strategy and the smoothness of the output flexibility.The fitness function was designed to adjust the weight coefficients of the two parts according to the flexible requirements.The parameters of the fuzzy controller were encoded by chromosome,and the fitness value was used as the evaluation basis to optimize the parameters of the fuzzy controller by genetic algorithm.The optimal parameters of the fuzzy controller meeting the requirements of the switching flexibility of each working mode were obtained,and the flexible switching control with the optimal comprehensive flexible effect was realized.Finally,the experimental platform of the super capacitor energy storage system with DSP as the core controller was built,and the control experiment of each working mode of the energy storage system and the flexible switching experiment between each mode were completed based on the working condition of the electric workover rig,which verified the correctness and effectiveness of the proposed control strategy.Based on LabVIEW,the upper computer monitoring platform is equipped to realize real-time monitoring of the working parameters and working state of each port of the energy storage system,online regulation of each mode control parameter and recording of the system’s operating data. |
