Comprehensive Power Losses Model For Electronic Power Trans- Former And Its Application

The electronic power transformer(EPT)has higher power losses and lower efficiency than the conventional transformer.However,the EPT can provide not only the basic functions of the conventional transformer such as voltage transformation,isolation and power transmission,but also many additional functions.The EPT can correct the power factor,compensate the unbalanced current and reduce the line power losses in the distribution network.Therefore,when using the EPT to replace the conventional transformer in the distribution network from the aspect of the power losses,the higher power losses of the EPT and the consequent reduced power losses in the distribution network lines require a comprehensive consideration.In this paper,a comprehensi ve power losses analysis model for the EPT in distribution networks is proposed and its application is analyzed.The details are as follows:First of al,by analyzing the power losses in the power electronic converters and intermediate frequency transformers in the AC-DC-AC EPT,the EPT's self-losses analysis model is established,and based on this,the power losses of the EPT can be quickly and easily obtained.On this basis,the EPT's example model is used to verify the power losses of each device and the whole.The power losses of the EPT and the conventional transformer are compared,and the comparison shows that that the EPT has a higher power losses compared to the conventional transformer.Therefore,it is not economical to use the EPT to replace the conventional transformers in the distribution network in general occasions.Then,a EPT reactive power compensation control strategy for distribution network is proposed to make the distribution network maintains the operation of the power factor at 1,and the reduced power losses on the distribution lines when the EPT is used to replace the conventional transformers for distribution network reactive power compensation are analyzed;An EPT three-phase unbalance compensation control strategy using a voltage outer-loop and current inner loop is proposed to realize the effecti ve compensation of the three-phase unbalance in the distribution network;The current unbalanced degree is proposed,and this parameter is used as a unified variable to analyze the reduced power losses on the phase and neutral lines when the EPT is used to compensate the unbalanced current in the three-phase four-wire distribution network;The relationship between the extra power losses on the power transmission lines which is reduced by the application of the EPT and the load power factor and the current unbalanced degree of the three-phase distribution network is verified by an example simulation.Finally,the comprehensive power losses analysis model for the EPT in the distribution network is established.Based on this,the conditions in which using the EPT to replace the conventional transformer can cause less power losses are obtained;and the conditions in which the application of the EPT can cause less power losses are The sensitivity analysis for the EPT comprehensive power losses model is carried out by comparing the value of each parameter variation impact on the EPT losses model,which can determine the priority principle of the EPT application in the distribution network;In case study,the validity of the comprehensive power losses model is verified and It shows the EPT have a better applicability for the remote rural areas,the industrial and enterprise distribution networks or the electric transit and railroad systems away from the power center.In this paper,the overall power losses change when the electronic power transformer is applied to the distribution network is analyzed,and based on this,a comprehensive power losses analysis model for the electronic power transformer in the distribution network is established,aiming at providing reference for the distribution network application EPT from economic aspects.The purpose of this paper is to provide a reference for the application the EPT in the distribution network from the aspect of the economy.