A Discrete State Event Driven Simulation based Losses Analysis for Multi-terminal Megawatt Power Electronic Transformer

At present,power electronic transformers(PETs)have been widely used in power systems.With the increase of PET capacity to the megawatt level.the problem of increased losses need to be taken seriously.As an important indicator of power electronic device designing,losses have always been the focus of attention.At present,the losses are generally measured through experiments,but it takes a lot of time and is difficult to quantitatively analyze the internal distribution of PET losses.To solve the above problems,this article first qualitatively analyzes the losses of power electronic devices and proposes a loss calculation method based on pure simulation.This method uses the Discrete State Event Driven(DSED)modeling method to solve the problem of slow simulation speed of large-capacity power electronic devices and uses a loss calculation method that considers the operating conditions of the device to improve the calculation accuracy.For the PET prototype in this article,a losses model of the PET is established.The comparison of experimental and simulation results verifies the feasibility of the losses model.Then the losses composition of PET was analyzed to provide reference opinions for actual operation.It can help pre-analyze the losses distribution of PET,thereby providing a potential method for improving system efficiency.

Research on power electronic transformer applied in AC/DC hybrid distribution networks

The AC/DC hybrid distribution network is one of the trends in distribution network development, which poses great challenges to the traditional distribution transformer. In this paper, a new topology suitable for AC/DC hybrid distribution network is put forward according to the demands of power grid, with advantages of accepting DG and DC loads, while clearing DC fault by blocking the clamping double sub-module(CDSM) of input stage. Then, this paper shows the typical structure of AC/DC distribution network that is hand in hand. Based on the new topology, this paper designs the control and modulation strategies of each stage, where the outer loop controller of input stage is emphasized for its twocontrol mode. At last, the rationality of new topology and the validity of control strategies are verified by the steady and dynamic state simulation. At the same time, the simulation results highlight the role of PET in energy regulation.

Low-voltage ride through of multi-port power electronic trans-former

A low-voltage ride-through(LVRT)control strategy for the multi-port power electronic transformer(PET)based on power co-regulation is proposed.During the sag and recovery of the grid-side voltage of the medium-voltage ac(MVac)port,the grid-connected active power of the low-voltage ac(LVac)port,rather than the power from external renewable energy sources(e.g.,photovoltaic(PV)),is adjusted quickly to rebalance the power flowing across all ports,thereby preventing overcurrent and overvoltage.Moreover,a power-coordinate-frame-based LVRT mode classification is designed,and a total of six LVRT modes are classified to meet the LVRT requirements in all power configuration scenarios of the PET.In this way,the PET is endowed with the LVRT capability in both power-generation and power-consumption states,which is significantly different from traditional power generation systems such as PV or wind power.Furthermore,by optimizing the active power regulation path during LVRT transition,the overcurrent problem caused by the grid-voltage sag-depth detection delay is overcome.Finally,the effectiveness of the proposed control scheme is verified by experiments on a hardware-in-the-loop platform.

Photoinduced Electron Transfer (PET) between C_(60) and Amines in Micelle Solution A Kinetic ESR Study

As indicated by kinetic ESR measurements, the key factor to affect electron recombination in the process of PET between C60 and amines is the space between donor and C60. To increase solubility of C60 in water, it was incorporated into micelle of surfactants. ]