| The ferformance converter is widely used because of its excellent speed regulating device.The input AC voltage converter for power system fault and the occurrence of a degree drop,during this time,the fall of the input AC voltage in inverter rectifier bridge under the effect caused by the DC bus voltage inverter internal to a certain extent reduced,thereby causing the protection action of frequency converter,which is driven by the motor will stop.Serious when can cause the generator tripping.Thus,the inverter can achieve low voltage ride in safety production becomes critical,through the anal ysis of the working principle of the inverter power circuit can be learned,low voltage protection hardware inherent protection within the inverter,not by modifying the parameters of the change,only in the external circuit of inverter,installation of a set of inverter DC bus the voltage is not lowered by the external voltage fluctuation of the converter without external device to ensure that the effect of voltage fluctuation,can output a constant AC voltage frequency converter,so as to ensure the LVRT ability.On the basis of consulting a large number of domestic and overseas literatures,this paper makes clear the goal of the design of low voltage ride through system.Finally,the scheme of adding a set of power electronic devices on the external circu it of the inverter is established.By analyzing the working principle of the general inverter power circuit and the principle of its low voltage ride through,the mathematical model of DC/DC(LVRTS)is established on the basis of the single BOOST circuit.The paper also analyzes the operation mode of the mathematical model and the criterion of starting and exiting in the running mode.Some important problems in the design of hardware and software(LVRTS)are discussed.In the aspect of hardware design,the BOOST basic DC/DC circuit based on the design of BOOST circuit rectifier and phase transformation module as multiple parallel inverter power supply,to ensure the DC bus voltage of the inverter input fluctuation.In order to meet the requirements of the design,the actual parameters of the LVRTS components and the auxiliary control circuit of LVRTS are defined.In the aspect of software design,the fuzzy adaptive PI control algorithm and bang-bang hysteresis control algorithm combined,put forward the strategy of automatic control of composite DC voltage loop,we developed a RTDS controller and a real-time simulation system,the hardware in the loop simulation test loop.The simulation results not only prove the rationality in the LVRTS parameter the design,commissioning and guidance of the PI controller parameters in the experiment.).In order to verify the actual effect of the LVRTS,a low voltage through power supply was made on the five coal feeder of Unit No.third of Baotou thermal power plant,and the no-load experiment was carried out.The experimental data show that the LVRTS established in this paper is different from the input voltage of the coal feeder.Can be stable under rated output DC,and does not affect the normal operation of the inverter internal control loop.To achieve the inverter and some of the important equipment vulnerable to fluctuations in the external voltage,still safe and stable operation. |
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