The basic principle of flywheel energy storage is the conversion between electrical energy and the kinetic energy of the rotating body: in the energy storage stage, the flywheel is driven by the motor to accelerate, and the electrical energy is converted into mechanical energy; in the energy release stage, the motor operates as a generator and the flywheel motor decelerates. Convert mechanical energy into electrical energy and output.

　　China Energy Storage Network News: Researchers Dai Xingjian, Jiang Xinjian, Wang Qiunan, Wang Yong, and Wang Shanming from the Department of Engineering Physics, Tsinghua University, and the Department of Electrical Engineering, Tsinghua University, wrote an article on the 21st issue of "Journal of Electrotechnical Engineering" in 2017, for the hybrid power of drilling rigs The transmission system has developed a 1MW/60MJ flywheel energy storage system, and carried out experimental research on shaft dynamic balance, charging and discharging, loss and efficiency testing.

　　Using high-strength alloy steel variable cross-section flywheel to store kinetic energy, the flywheel motor shaft system is a vertical support structure, and the heavy-duty assembled permanent magnet ring bearing bears 97% of the shafting weight. The permanent magnet motor rotor adopts grid structure silicon steel with embedded magnetic steel to realize high-speed and safe operation.

　　Based on high-capacity power electronic conversion and motor control technology, the control circuit hardware and software for 100-300kW charging and 500-1000kW discharge have been developed. The dual closed-loop control strategy of magnetic field weakening, speed and current is adopted during the charging process, and the dual closed-loop control strategy of magnetic field weakening, speed and current is adopted during the discharge process. Voltage closed loop and current feedforward control strategy. After dynamic balance, the vibration of the flywheel energy storage unit is reduced to within 0.07mm. The charging and discharging cycle efficiency of the flywheel energy storage power supply reaches 86%-88%.

　　The basic principle of flywheel energy storage is the conversion between electrical energy and the kinetic energy of the rotating body: in the energy storage stage, the flywheel is driven by the motor to accelerate, and the electrical energy is converted into mechanical energy; in the energy release stage, the motor operates as a generator and the flywheel motor decelerates. Convert mechanical energy into electrical energy and output.

　　Modern flywheel energy storage system integrates advanced composite rotor technology, magnetic bearing technology, high-speed motor and power electronic technology to greatly improve performance. Around 2000, modern flywheel energy storage products began to be popularized in uninterruptible power supply, power quality management, and grid frequency modulation. Flywheel energy storage applications under development include wind power generation and solar power generation. In recent years, breakthroughs have been made in the research and development of key flywheel energy storage technologies in China, and it is in the period of industrialized application expansion.

　　Oil drilling rig is the main equipment for drilling construction. Its power is usually provided by diesel or natural gas engine. The output characteristics of the power unit are not flexible enough to adapt to frequent and large fluctuations in the load of the drilling rig, and the power system has too much redundant capacity.

　　Introduce peak-shaving motors and flywheel energy storage devices into the drilling rig power system to achieve power peak-shaving operation; use the redundant output of the power unit to drive the peak-shaving motors to generate electricity at low loads and charge the flywheel energy storage system; when peak loads occur, The flywheel energy storage system discharges, drives the peak-shaving motor for electric operation, and quickly releases power to the power system to balance the load. The peak-shaving operation of the power unit runs smoothly and can reduce redundant capacity, which is conducive to energy saving and emission reduction.

　　The technical indicators of the energy storage unit proposed by the hybrid power transmission system of the drilling rig are: charging power 100-300kW, generating power 500-1000kW, available energy 42MJ, and frequent charging and discharging cycles of 3-5min. Investigations show that no manufacturer can provide mature products. For this reason, a 1MW/60MJ flywheel energy storage system has been developed, and the shaft dynamic balance, charging and discharging, loss and efficiency test experiments have been carried out.

　　in conclusion

　　Using the finite element strength analysis method, modeling and optimizing the design of a large-scale alloy steel flywheel with variable cross-section and the grid structure of the embedded permanent magnet motor rotor. After optimized design and assembled permanent magnet bearing, the bearing capacity reaches 50kN, which is equivalent to the weight of the flywheel motor shaft system.

　　Based on the high-capacity power electronic conversion and motor vector control technology, the control circuit hardware and software for low-power charging and high-power generation have been developed, using field weakening, current feedforward, voltage closed loop and speed closed loop compound control strategies. After the motorized balance, the vibration of the flywheel energy storage unit is reduced to less than 0.02mm in the high-speed area, achieving smooth operation in the full-speed range.

　　Theoretical analysis of mechanical loss and motor iron loss is consistent with the experimental results. The standby loss of the system is 18kW, which is 2% of the maximum power generation. The charging and discharging cycle efficiency of the flywheel energy storage system is 86%-88%. Experiments prove that flywheel energy storage is a high-power, high-efficiency energy storage technology.