Development Of Single-phase Inverter With Adjustable Frequency And Amplitude Based On Optimal Tracking Control

Single-phase inverter with adjustable frequency and amplitude is one of the most important devices in the smart meter calibration process,and its performance will directly affect the accuracy of the calibration.An excellent single-phase inverter with adjustable frequency and amplitude requires that the amplitude and frequency of the output voltage must be continuously adjustable within a certain range,with low output steady-state error and good output waveform quality.Based on this background,a quasi-single-stage inverter with adjustable frequency and amplitude is proposed in this paper.Besides,a steady-state error suppression strategy based on the design is also proposed to improve the calibration accuracy of smart meters.First of all,the traditional single-phase inverter with adjustable frequency and amplitude has large switching loss and complicated control because of two highfrequency parts in the traditional power supply.Aiming at reducing the large energy loss and simplifying the control system,this paper proposes a quasi-single-stage inverter design that combines a quasi-DC-DC converter with a commutation circuit.Quasi-DCDC converter,as a key part of this power supply,directly affects the realization of output adjustable frequency and amplitude modulation in the power supply.In order to facilitate subsequent research and design,a detailed analysis of its mathematical model must be made.Secondly,the Fourier analysis of the sine half-wave signal output by the quasi-DCDC converter in the power supply is carried out.Moreover,the filtering parameters and traditional double closed-loop parameter of the quasi-DC-DC converter based on increased bandwidth are proposed.Since the steady-state error of the quasi-DC-DC converter’s output sine half-wave voltage will seriously affect the amplitude error and waveform quality of the output sine voltage of the power supply,this paper will make a quantitative analysis of the output steady-state error of the quasi-DC-DC converter under traditional PI double closed-loop control.Finally,in view of the large steady-state error of the output sine-wave voltage in quasi-DC-DC converter under the traditional double closed-loop control,based on the linear quadratic optimal controller design,this paper proposes a steady-state error suppression strategy based on the LQR optimal tracking control.And it is combined with the quasi-DC-DC converter.In addition,this paper analyzes the principle of steady-state error suppression based on the LQR optimal tracking control from the bandwidth and the closed-loop root locus of the converter.At last,this paper verifies the correctness of the theoretical analysis through simulation experiments.Based on the foregoing theoretical analysis and simulation experiment results,this paper designs the hardware circuit and control program of the single-phase inverter with adjustable frequency and amplitude.By comparing and analyzing the output waveform and measurement data of the power supply under traditional double closed-loop control and LQR optimal tracking control,the rationality of the proposed design and steady-state error suppression strategy is verified.