Research On Inverter Control Strategy For Mining Digital AC Stabilized-Voltage Powr Supply

The project is an important part of“Development of Mining Digital AC Stabilized Power Supply and High Power Intrinsically Safety Power Supply",which is Shanxi Province Science and Technology Research Industrial Projects(No.20090321046).Mining Digital AC Stabilized Power Supply developed to improve the quality of power supply of mine safety monitoring equipment.It mainly consists of the rectifier and inverter.The rectifier is used to realize system power factor correcting and stabilizing DC bus voltage,inverter provides high quality AC power to the load.The inverter of mining digital AC stabilized power supply is requested the following advantages,such as high control precision in steady-state,fast dynamic response and strong ability against periodic disturbance.So the choice of control strategy,one of the factors directly determining the performance of the inverter,is very important.The traditional control strategies of inverter possess their own advantages,but can not own these characteristics at same time.Consequently,according to the performance index of inverter of mining AC stabilized power supply,a variety of control strategies of inverter are studied further.A repetitive sliding-mode control strategy of inverter is proposed.The researched inverter control strategies are verified through a series of simulations and experiments.The experimental results have shown that the proposed control strategy greatly improve the steady-state characteristics,dynamic characteristics and robustness of control system.The specific research contents of thisdissertation are as follows:The AC small-signal dynamic model and switching cycle averaging model of inverter based on unipolar modulation are built up though the state space average method.The control system based voltage and current dual-loop controller is designed.Simulation and experimental results can be shown that the performance of the control system can not meet the requirements,so the research of more advanced control strategy is necessary to improve the performance of the inverter.In order to eliminate the steady state error of mine AC stabilized power supply inverter with rectificative load,repetitive control technique based on the internal model principle is researched.In view of disadvantages of slow dynamic response and designing complexity with the traditional repetitive control,instead of the traditional compensator using FIR digital filter.The conditions for stability and the expression of errors of improving repetitive controller are derived.The experimental results are shown that the improving repetitive strategy is better than the traditional repetitive strategy at aspect of steady-state performance and nonlinear load adaptability,but because of the constraints of inherent periodic delay,the dynamic characteristics of improving repetitive strategy can not meet the requirements.In order to improve the dynamic characteristics of the system,sliding mode controller is designed based on the discrete variable rate reaching law by adopting the output voltage and capacitor current as state feedback variables.Then the control law expression,the range of parameters and conditions of stability of control system is derived.The output performance of sliding mode control inverter based on the constant rate reaching law and the variable rate reaching law are compared by the experiment and simulation.The results can be shown that output voltage chattering and steady-state error of sliding mode controller based on the variable rate reaching law is smaller,and dynamic response is faster.However,the output voltage waveform of inverter has large distortion under nonlinear loads,can not meeting request of anti periodic disturbance capacity.The improving repetitive controller has the advantages of high steady-state control accuracy and strong ability of anti periodic disturbance,and the discrete sliding mode controller can greatly improve the system dynamic performance and robustness.However,two control strategies have their own shortcomings.Therefore,a hybrid control strategy of inverter based on repetitive control and sliding mode control is proposed in this dissertation.On the basis of the equivalent control principle of sliding mode,sliding mode controller is divided into two parts as error correction and reference signal feedforward,with the repetitive control embedded in the error correction to constitute repetitive sliding-mode controller.Transfer function and stability conditions of repetitive sliding-mode control inverter system are derived and analyzed,and the control law expression is given.Experimental results can be shown that steady-state error of output voltage of repetitive sliding-mode control inverter under rated resistive loads is only 2V.The total harmonic distortion is only 1.0%under nonlinear loads.Amplitude of output voltage fall is only 20%of peak value when inverter increasing load suddenly,and output voltage can tracking the reference signal again within 1.5ms.Therefore,the proposed control strategy can greatly improve steady-state control accuracy,dynamic response and ability of anti periodic disturbance of mining AC stabilized power supply inverter,meeting the all of performance index of mining AC stabilized power supply inverter at same time.