Research On Broadband HF Link Inverter Based On Beat Frequency

As a kind of special power supply for testing,broadband inverter owns a wide application,which has relatively high research value and some room for technological innovation.With the goal of broadband output,this paper proposes a novel high-frequency link inverter topology based on beat frequency and LCC resonance.In line with this novel inverter topology,the system working principle is studied,key parameters are designed,and different control methods are discussed.Finally,a principle prototype is made and experiment research is conducted.In this paper,the main work and achievements are as below:(1)Systemic carding on current state of different types of high-frequency link inverter is carried out.To the technical problems caused by broadband output of inverter,the principle of high-frequency link inverter topology based on beat frequency is presented.(2)In terms of broadband output,to break through the shackles of existing technology,a novel high-frequency link inverter topology based on beat frequency and LCC resonance is proposed.Then,analyzes each switch status,soft switching mode,four-quadrant operation mechanism in detail and concludes equivalent circuit.Using sinusoidal steady-state analytical method and fundamental wave analytical method,the steady-state mathematical model is established,which can provide guidance for parameters design.(3)To the problem of great current value in circulation when beat frequency is modulated,four coupled inductors are used in the circulation loop.This method is expected to increase the impedance of circulation loop.By the means of theoretical derivation and simulated analysis,it proves that this method can greatly reduce current value,and realize the wholly conversion of current in primary winding to secondary winding.In this way,the quality of modulation waveform can be guaranteed.(4)To the key technical problem of adaptively capture synchronous demodulation signal,the scheme of integration of modulation signal and synchronous demodulation signal generation was proposed,and FPGA-based full-digital open-loop control system is established.According to this novel inverter topology,three control methods are discussed through simulation analysis.The results show that four-quadrant control method is the most appropriate,which can balance the quality of output voltage waveform and soft switching.(5)A principle prototype is made and experiment research is conducted.The experiment results show that this novel inverter topology and control method can realize broadband output voltage from 20 Hz to 1010 Hz.Within the range of broadband,the THD of output voltage is less than 3%,and the relative error of frequency is less than 0.2%.Meanwhile,the soft switching can be realized in spite of the changing output frequency.The output filter only has capacitors without inductance;Cycloconverter can be free of voltage spikes during commutation.Also,this inverter can operate in four quadrants.In general,the whole study proves that this novel inverter realizes the function of broadband output,and with characteristics of high-frequency link,current mode,soft switching and bi-directional power flow,which verifies the validity and feasibility of the scheme.