Research On New Z-source Photovoltaic Grid-connected Inverter Based On MPIDNN Control

The topological structure of the common photovoltaic grid-connected inverter circuitwas analyzed in this paper, taking the existing problems in the common topology designinto account, the Z-source inverter circuit topology is used in grid-connected PV systems.Z-source network can boost the voltage of the DC side by using the characteristics ofpermiting the three-phase bridge arm shoot-through, and achieve the maximum powerpoint tracking of the photovoltaic cell array by regulating the direct duty cycle.First, the working principle of a Z-source photovoltaic grid-connected inverter wasanalyzed, constructing the low frequency signal mathematical model of the Z-source PVgrid-connected inverter in the S domain, aiming at the unquenchable output voltage spikeof the Z-source network in the traditional control strategy of Z-source inverter, proposed anon-symmetric MPIDNN unified controller to solve the non-minimum phasecharacteristics problem inherent in the Z-source network, decoupling control between thevariables, and inhibiting the DC link voltage spikes.Second, the forward algorithm is derived in detail, and the goal of error backpropagation MPIDNN algorithm is given. Taking the output current component based onthe non-symmetric MPIDNN unified controller as the command value of the d-axis of theinner current loop, the grid side adopt the grid-connected current decoupling controlstrategy based on the voltage feed-forward, controlling the active current and reactivecurrent in the d-q axis independently, solving the difficult problems brought about by themutual coupling of the control variable; the pulse width modulation strategy for thethree-phase inverter bridge switching tube is SVPWM_STV algorithm, modifying thetraditional SVPWM switching timing diagram; design parameters of the Z-source networkmaster circuit components and select the components, and gives part of PCB engineeringschematic designed.Then, the engineering model of the photovoltaic cells was constructed, and asimulation model was built in MATLAB software; according to the working environmentof the Z-source photovoltaic grid-connected inverter, the maximum power point trackingof the photovoltaic cell array was analyzed, the MPPT algorithm based on IOGM-CVTwas proposed, compiled the corresponding S-function, the algorithm can adapt to theenvironmental conditions of drastic changes of the light and the temperature, tracking themaximum power point effectively.Finally, a MATLAB simulation model of the photovoltaic Z-source grid-connected inverter system was built, and a comparison of simulation and the experimental resultsshowed that, relative to the traditional closed-loop PID control, non-symmetric MPIDNNunified control can effectively suppress the DC link voltage spikes, and can fast-track themaximum power of the photovoltaic cell array, and also verified the correctness of theSVPWM_STV; the hardware experimental platform built in the Z-source grid-connectedinverter take TI’s TMS320F2812as control core and Fairchild SPM FSB30CH as thepower device, tested the basic input and output waveforms and the drive waveform.