Study On The Power Supply With LVRT Capability For Frequency Inverters In Power Plant

As a kind of speed regulation device with excellent performance, frequency inverter is widely used in power plants. However, when the voltage dip occurs inside the power plants, the low voltage protection of the frequency converter will be triggered. A series of actions will create which may lead to the shutting down of the power plant. So the Low Voltage Ride Through (LVRT) of the frequency inverter has aroused wide attention. As the frequency inverters do not have the function of LVRT and the equipment is hardly reformed, the installation of the accessory equipment to achieve the function of LVRT for frequency inverters is of practical significance.In this dissatation, installing the electrical and electronic device is proposed to realize the LVRT. The principle of power supply with LVRT capability for frequency inverters (PSLFI) for frequency inverter is clarified in detail. Based on the BOOST circuit of one of DC/DC topology, the mathematic model is built. The different working modes and criterion of starting and seting down under the running mode are discussed. Based on this,the key technologies of software and hardware of PSLFI were discussed. The topology mainly consists of uncontrolled rectifier and the interleaved three phases BOOST. According to the design requirement, the component parameters and control circuit of PSLFI are committed. And based on the double loop control method, the fuzzy self-adapted control method and bang-bang hysteresis control method are proposed. The digital/physical hybrid simulation platform of PSLFI based on RTDS is constructed and closed loop experiments are done. The result shows that the parameters of the components designed above are reasonable and it can guide the direction of the PI parameters debugging in the field experiment.Finally, Combining with the coal feeder and its inverter, the field experiments are run. The result shows that the designed PSLFI in this dissatation can output the steady dc voltage and the control power is realiable under the different faults of power supply in the power plant. So the inverter and sensitive load can run with no disturbance.