Research On T-source Inverter With Low DC-Link Voltage Spike And Power Decoupling Capabilities

Prospering economic primarily oriented towards fossil energy has brought serious environmental pollution and climate changing problems.What’s more,the"dual carbon"target has tremendously transformed the traditional industrial system to a low-carbon direction.Among the electric power sector,it seems that using clean energy instead of coal power generation has become a dominant trend.Generally,the voltage class demanded by the AC load is higher than the voltage output by the PV plate in photovoltaic power generation system.However,according to the law of energy conservation and the characteristics of the inverter bridge,the modulation ratio should be less than 1,so that the ac voltage peak value obtained is lower than the voltage on the DC side,which is generally insufficient to meet the grid-connected voltage level.Such circumstance continued until the emergence of impedance source inverters,which can boost the input voltage in unipolar structure,also means smaller volume and higher efficiency.As the first echelon to introduce coupled-inductance into the impedance network,T-source inverter has the advantages of less components and flexible voltage gain by adjusting the turns ratio.However,T-source inverter still has some inevitable problems,which restrict the application range gravely.Therefore,this paper intends to solve the problems existing in the traditional T-source inverter,optimize the T-source impedance network,and conduct an in-depth study on the power decoupling technology,the specific contents are as follows:By analyzing working principle of T-source inverter minutely,the formation mechanism of dc-link voltage spike is obtained.Furthermore,through optimizing the impedance network and adjusting the position of components,a family of Low DC-Link Voltage Spike T-source inverters is proposed,which can continue the input current and recover the energy in the leakage inductance of coupled-inductor from the hardware level.At the same time,the dc-link voltage is completely clamped relying on the characteristics of capacitors,consequently,the dc-link voltage spike phenomenon can be suppressed.In order to comprehend the proposed topologies comprehensively,a small signal model is established in terms of the structure I in the Low DC-Link Voltage Spike Topology Family.Besides,the working state is divided into three parts within a switching cycle,which can improve the accuracy compared to the traditional ones,and the correctness of the established model is verified by the DC component.What’s more,the Laplace transform was applied to obtain transfer function of each parameter,and then the zero-pole distribution diagram was adopted to judge the system stability variation trend when the shoot-through duty ratio D,modulation ratio M,capacitance C₁,C₃ and inductor L_in changed slightly,which can provide guidance for the selection of passive device parameters in the initial inverter design stage.Commonly,the electrolytic capacitance with large capacitance in traditional impedance networks will undoubtedly cause reliability reduction problem.However,this predicament can be overcame perfectly through power decoupling technology.Coupling the power decoupling cell with impedance network,the High Voltage Gain LDLS-TSI-I structure with power decoupling capabilities was constructed subsequently,which can significantly reduce the capacitance value in impedance network.By controlling the voltage reference of the decoupling capacitor,the double frequency power ripple is transferred to the technical power decoupling cell,at the same time,the dc bias voltage of the decoupling capacitor is connected in series with the input power supply to raise the whole DC input voltage.Besides,the capacitance of decoupling capacitor is decreased by increasing the fluctuation voltage value of decoupling capacitor.Apparently,the film capacitor with longer service life could be selected to improve the entire system’s reliability.Finally,to illustrate the actual performance of the proposed structure,an experimental hardware platform is built realistically at the power rate of 180W.Therefore,the feasibility of the topology can be confirmed at the experimental level.