Research On The Control Method Of Energy-Feedback Elevator System And Its Power Quality

Elevators are used more and more in large public buildings and residential buildings, with the development of national economic. The huge power consumption cannot be ignored because of the shortage of energy, nowadays. Elevator energy-feedback technology has been becoming a new technical innovation in elevator industry, and the research of the correlation technique of energy-saving is imperative.To modify the VVVF (Variable Voltage Variable Frequency) elevators, which are popular used in our country, a parallel-structure elevator feedback system which has the function of energy-feedback and active power filter is presented. A three-phase voltage PWM converter, which is connected in parallel, is designed as the parallel energy-feedback device. Some innovative achievements are gained with the deep research of the power electronics technology and the control methods. The main research contents are as follows:(1) A circuit of elevator system with energy feedback is designed after analyzing the working principle. The plug-in PWM converter is paralleled to the grid-side, to build an energy feedback pathway. The regenerated energy will be fedback to the grid timely. In the absence of regenerated energy to feedback, the plug-in PWM converter works as an active power filter to eliminate the harmonics brought by nonlinear load and improve the power quality of the grid-side of the elevator system.(2) Research the DCC (Direct Current Control) method of the parallel three-phase PWM converter, a double closed-loop control structure is designed, in which current loop is considered as inner-loop and voltage loop is considered as outer-loop. SVPWM (Space Vector Pulse Width Modulation) method is used to modulate the switching signal. In order to increase the dynamic control performance of resisting load disturbance of the PWM rectifier, the load disturbance feed forward compensator is brought in the double closed-loop PI control structure. In addition, PI controller and repetitive controller are mixed used in the current control loop. The repetitive controller is used to restrain the periodic dead disturbance, to improve the accuracy of the steady state of the current. On the basis of theoretical analysis, simulation model of the elevator energy feedback system is built by using Matlab/Simulink software. Simulation results validate the feasibility of the theoretical analysis, guiding us to design and make an experimental prototype.(3) DPFC (Direct Power Fuzzy Control) method is proposed based on grid current detection. Grid current detection does not need load current detection and harmonic current extraction, is more simple and effective to solve the contradiction between the switch frequency and the width of hysteresis comparator in the traditional DPC(Direct Power Control) method. The errors of instantaneous active power and reactive power with their reference values are sent into fuzzy rule base as fuzzy variables. The switch signals are generated by fuzzy rules. This control method is more flexible and effective, without predefined switch table and hysteresis comparator. The simulation results show that the designed elevator system has excellent steady and dynamic performance. Sinusoidal grid current and unit power factor can be achieved. And the power quality is also improved. The novel DPC based on fuzzy control is better than DCC method and traditional DPC.(4) This thesis proposed a fractional-order PIλ controller to realize stability control of DC-side voltage. The fractional-order PIλ controller is designed with the frequency-domain method with the mathematical model of the power control system based on instantaneous power theory. The simulation results show that fractional-order PIλ controller has good dynamic and robust performance, and the DC-side voltage is still stable when there has impulse-voltage and load-changing. The DC-side voltage stabilized at the given value quickly and accurately. The new control strategy is better than the traditional PI control strategy.(5) A novel DPC method based on18sectors partition is proposed, in which the space voltage vector is divided into18average sectors, based on the influence between the voltage vectors and the active and reactive power in each sector. And then, new switch table is designed. Simulation results of the novel DPC based on the18sectors is more effective on the regulation of reactive power, grid current is better sinusoidal. DPFC based on18sectors partition is proposed, detail fuzzy logic rule-base is designed, and the simulation proves that this method improves the sinusoidal of the grid current, the control effect is better than that of using hysteresis comparator.(6) The hardware circuit of the elevator energy feedback system is designed in laboratory, using DSP as main control chip, to develop an experimental prototype. Experiments are carried on the design and development of the hardware and software, to obtain the experimental waveforms. The experimental results show that the system design is reasonable and effective, can effectively achieve the energy feedback function, is good to improve the work performance of the existing elevators, not only savinng the electrical energy but also achieving green power grid. The energy-saving test results can prove the research is viability.