Abstract

As new electric power conversion equipment, a multi-port power electronic transformer (MP-PET), including a power electronic converter, high-frequency transformer, and multiple ac or dc interconnection interfaces, has a broad application in the hybrid distribution network. However, high integration and a large number of energy storage devices has led to very a high-order model of the system. To address this issue, a reduced-order small signal model of MP-PET is established in this paper. By taking the participation factors of the system mode to the state variables, the reduced-order model is derived based on the state variables, which are highly correlated with the dc voltage dominant mode. Compared with the full-order model, the proposed reduced-order model is accurate enough and simplified, and the validity of the simplified model is verified against simulations on a 10 kV/3 MVA MP-PET. The simulation results indicate that the proposed reduced-order model coincides well with the dynamic performance of the MP-PET.

Highlights

  • With the increase of distributed renewable energy, dc power load and different types of multi-energy power generation systems that are connected to the power grid, the dual-port power electronic transformer applied to the traditional ac distribution network has gradually failed to meet the access requirements

  • In [5], a multiport PET topology that was applied to the low-voltage dc bus was proposed and the circuit of each port is connected to the dc bus through the isolated dc-dc converter

  • In order to quickly and effectively analyze the dynamic response on system dc bus voltage, this paper uses the participation factor analysis method to establish a reduced-order small signal model based on the full-order mathematical model, which is derived from Section 2

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Summary

Introduction

With the increase of distributed renewable energy, dc power load and different types of multi-energy power generation systems that are connected to the power grid, the dual-port power electronic transformer applied to the traditional ac distribution network has gradually failed to meet the access requirements. In [6], a multi-port PET based on a multi-fed dc bus at the input stage, which can be connected to multiple high-voltage ac power grids, was proposed. In [8], a global small signal model is developed for VSC-HVDC applied to the passive network Based on this model, the model analysis method is used to analyze the system stability, and the sensitivity analysis method is proposed to identify the factors of the system instability. In order to describe the dynamic behavior characteristic of the whole system in detail, most existing studies have usually established a small signal model based on the full-order linearized state equation This method can completely retain all the modal information of the system, the derivation process is tedious and calculation is complicated, which leads to a very high-order model.

The Full-Order Small-Signal Model of MP-PET
PET Small Signal Modeling Analysis
Control system Small Signal Modeling Analysis
The Reduced-Order Small-Signal Model of MP-PET
PET Small Signal Model Eigenvalue Analysis
PET Small Signal Model Simplification
Simulation Results
Case II Model verification by power inversion
Case III Model contrast verification
Conclusions

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