| Elevators are increasingly irreplaceable in the modernization of society, and since their invention,they have undergone several generations of replacement and technology upgrades, while providing convenience for people to move. Numerous studies show that the energy consumed by elevators accounts for about 20% of the total energy consumption of high-rise buildings. As the global energy shortage becomes increasingly relevant, the prospects for high-energy consumption elevators are not optimistic. The development of such technology is severely restricted by energy consumption issues.With rapid economic development and improving living standards, there has been a sharp rise in domestic elevator ownership: the data show that, in 2014, the total domestic elevator ownership has reached 3.6 million units with an annual growth rate of approximately 20%. In an era where the scale of industrial production continues to expand, China’s power generation capacity is relatively weak, as is the energy supply. The contradiction between supply and demand for energy has become increasingly prominent, and increasingly more focus has been placed on research on energy-saving elevators by the government, manufacturers, and customers. Therefore, the realization of energy consumption reduction is not only of important economic value, promoting the rapid development of the elevator industry, but also in accordance with the present stage of green and sustainable development strategies in our nation.To reduce the energy consumption of the elevator and achieve its energy-saving operational purpose, this study proposed and designed a new type of high-efficiency hybrid hydraulic-electric drive energy-saving traction elevator system based on the structural, operating, and energy-consumption characteristics of traction elevators. The system combines pump/motors, accumulators, and other elements of the traction motor drive system to form an energy-recycling hybrid hydraulic- Electric energy-saving drive system. This system and the traction drive system are coupled. For an elevator in operation, when the hoisting machine is in the power-generating state, the majority of the gravitational potential energy is stored in the accumulator in the form of hydraulic energy; when the hoisting machine is in the power-driven state, the energy stored in the hydraulic accumulator is released, thus assisting the hoisting machine and, ultimately, reducing energy consumption and thus saving energy. The simulation and experimental results showed that the new energy-saving elevator could start up steadily and smoothly with good speed control performance. The energy-saving efficiency of the new elevator is approximately 15%, significantly reducing the temperatures of the elevator control system and engine room. The new elevator uses the existing traction elevator control method, simplifying the control strategy. It’s known from the research that the traction motor of the energy saving elevator will change from generating state to electric state as the pressure of accumulator becoming large in the process of accumulator filling which will cause the energy consumption again.When the accumulator is in the process of releasing oil, for the large initial pressure, the output power of the accumulator is larger than the operation required power of elevator which will cause the energy dissipation again. So in this study, a torque-compensation method based on a variable- displacement pump/motor is put forward, and the simulation results show that this method could effectively reduce the energy consumption of the traction elevator.In recent years, elevator accidents have occurred; thus, the safety issue of traction elevators cannot be overlooked. The existing protection system of the safety gear-overspeed governor system of elevators can resolve the falling and over-speeding of elevators caused by control failure, brake failure, and sudden power outages. However, because mechanical structures are not guaranteed to be infallible, accidents involving falling elevators cannot be totally avoided. In this research, the new energy-saving traction elevator system uses a directional valve to control the working state of the accumulator. In a sudden power outage, each type of valve has a different power-off mechanism. That is to say, when the directional valve is in the state of filling the accumulator, the pump/motor provides a reverse torque that stops the elevator, and works together with the safety gear to halt the operation of the elevator. When the valve is at the stop position, because the four oil ports are all closed, the hydraulic pump/motor cannot rotate forward or backward, which could prevent the elevator from falling and instead park it safely.The energy-saving principle of Hydraulic-Electric hybrid traction elevator can not only reduce energy consumption, but ensure security and safety that is more important for its running. Especially in the case of all electrical control failure, the elevator can also keep in stop state moothly.The main contents of the thesis are as follows:Chapter I describes the current development status and trends in China’s elevator market and the energy consumption of existing elevators. Furthermore, elevator history and classifications are reviewed, focusing on an overview of energy-saving technologies used in traction elevators and the development and application of energy-saving and energy-recycling technologies. Finally, based on the comprehensive analysis mentioned above, the significance of this research and the main research content are proposed.Chapter II introduces the operating characteristics of conventional elevators and analyzes the basic structure of the traction elevator and its typical operating quadrants. Torques exerted on elevators with different counterweights at different operating conditions are analyzed in detail, and the dynamic model of the elevator is constructed. Through the analytical simulation of the dynamic model, the torques exerted on elevators with different counterweights are obtained under different loading and working states. A new hybrid hydraulicElectric drive traction elevator energy-conserving principle is proposed by analyzing the working principle and operating characteristics of the energy-saving elevator. Finally, hoisting machines and hydraulic components are selected for the system, and an energy-efficient traction elevator control system is designed.Chapter III constructs a mathematical model for the high-efficiency energy-saving elevator system, mainly based on the analysis and mathematical modeling of the features and operating characteristics of synchronous traction machines, hydraulic pump/motors, and accumulators. The two-speed curves of an operating elevator are analyzed and compared, and curves of velocity and acceleration are simulated. The goal of this project is to reduce the energy consumption of the elevator system, so an energy-consumption analysis of conventional elevators is necessary to understand variations in the process. This chapter establishes conventional elevator models using the simulation software SimulationX, and analyzes the simulation of elevator energy consumption under different operating conditions.Chapter IV establishes the proposed simulation model for the energyefficient traction elevator and analyzes the simulation of elevators with different counterweights. In cases with counterweights of 1000 and 1500 kg, the change in energy consumption is analyzed in the simulation under four different working conditions: light-load upward, light-load downward, heavy-load upward, and heavy-load upward, and the energy efficiency of the energy-saving elevator is calculated. Furthermore, the energy-saving results of the elevator with the variable-displacement pump/motor energy-saving system is simulated and analyzed after the adoption of torque-matching control.Based on the above theoretical research and simulation analyses, Chapter V determines the test components and test plan of the energy-saving elevator through the detailed analysis and parameter optimization of the energy-saving elevator system and structure. The energy-efficient traction elevator energy-testing rig is built. First, tests and analyses are conducted for the energy consumption of conventional elevators with different loads and different operating distances, and the results are compared with simulation outcomes. Then the energy-saving system and traction drive shaft are coupled for the integrated test. Through the comparison and analysis of no-load tests on the ground and on the floors, the operating efficiency of the mechanical energy-saving system is obtained. Furthermore, the energy consumption of the energy-saving elevator at different operating conditions is tested and analyzed, and the energy consumption of traditional elevators is compared to obtain the energy efficiency of the proposed high-efficiency elevators.The sixth chapter summarizes the research work, arrives at the main research conclusions, and proposes future research directions for material not addressed by this work.The research work showed that the proposed hybrid hydraulic-electric drive energy-saving traction elevator system had the correct design principles and good energy saving results, and could effectively improve the safety and reliability of traction elevators and achieve the desired objectives. The research achievement of the paper not only is one development direction of the energy saving elevator, but also has good application prospect in other vertical elevatoring mechanical devices. |
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