The Thermo-Hydraulic Analysis for Sub-Module of ITER HC-SB TBM Design

As the ITER （international thermonuclear experiment reactor ） project is being carried out further, original parties （ EU, JA, RF ） of ITER had accomplished their ITER TBM （ test blanket module ） design in 2001. China joined the negotiation of 1TER project and planed to develop own TBM modules in 2003. A preliminary design description document （ DDD ） for the CH HCSB （ chinese helium-cooled solid breeder ） TBM module design had been completed at SWIP in 2004. A modified structure design based on the 2004 version had been carried out subsequently. Main modification of structure design is that the sub-module design is adopted instead of the previous integrative module design. The modified design enforces the reliability and the flexibility of TBM module structure. The integral TBM module consists of 9 sub-modules. The thermo-hydraulic analysis for sub-module is very important, because the sub-module as a relative independent module has the most basic function of the test blanket module, such as depositing heat, producing tritium, etc.

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.

A modular multilevel power flow controller for meshed HVDC grids

Based on the comparison of existing power flow controllers(PFC)in meshed HVDC grids,the full-bridge modular multilevel converter based PFC(MMPFC)is proposed.At first,the general branch current calculation method of meshed HVDC grids with the PFC is presented,and then,the issue of over-voltage on the thyristor based PFC is described and analyzed.Through the analysis of different operating modes of the full-bridge sub-module,the mechanism of over-voltage ride through of the MMPFC is indicated.The control strategy of the MMPFC,which is used to control branch current and keep capacitor voltage balancing,is elaborated.Finally,the performance on current regulation,bidirectional operation and over-voltage ride through is simulated and verified in a built model with PSCAD/EMTDC.

Modular Reciprocating HVDC Circuit Breaker with Current-limiting and Bi-directional Series-parallel Branch Switching Capability

The high-voltage direct current(HVDC)circuit breaker is becoming popular with the rapid development of the flexible HVDC grid for efficient DC fault ride-through purposes.This paper proposes a novel module for reciprocating HVDC circuit breaker topology,whose branch connections are able to switch between series and parallel modes to limit the rising rate and interrupt the DC fault currents.Diode-bridge submodules(DBSMs)are used to compose the main branch for current interruption.Besides fault clearance,the proposed topology has the advantageous function of DC fault current limiting by employing DBSMs with bi-directional conduction capability.The topology can easily switch among branch connection modes through the assembled trans-valves,and their resistance and reactance are very small in the normal state when branches are in parallel and the values become promptly large in the transient state when the branches are series connected.With the modular design,it is easy to change the number of branches or sub-modules and the types of sub-modules to adapt to more specific needs.A 6-terminal modular multi-level converter(MMC)based HVDC grid is established in PSCAD/EMTDC,and various simulation scenarios are carried out to validate the proposed topology.

Novel Modular Multilevel Converter Against DC Faults for HVDC Applications

In view of the DC fault current isolation deficiency for the conventional half-bridge sub-module(HBSM)based modular multilevel converter(MMC),this paper presents an improved MMC topology.Both quasi reverse blocking submodules(QRBSMs)and current limit modules(CLMs)are employed to improve the DC fault handling capability for HVDC applications.This paper analyzes such a new converter configuration and operation principles.Then the DC pole-to-pole short circuit fault is taken into consideration for further study,as well as the fault current blocking mechanism and quantitative relationship between system electrical stress and key parameters.To validate the feasibility of the proposed topology and fault protection theory,extensive simulation results are demonstrated.It is concluded that the QRB-MMC can effectively block the fault current under DC fault condition.In addition,CLMs play an important role in further accelerating fault current attenuation.Moreover,QRB-MMC employs the original control and modulation strategies under normal operation conditions;thus,it further reduces the complexity of industry design.

A DC Chopper Topology to Mitigate Commutation Failure of Line Commutated Converter Based High Voltage Direct Current Transmission

To reduce the probability of commutation failure(CF)of a line commutated converter based high-voltage direct current(LCC-HVDC)transmission,a DC chopper topology composed of power consumption sub-modules based on thyristor full-bridge module(TFB-PCSM)is proposed.Firstly,the mechanism of the proposed topology to mitigate CF is analyzed,and the working modes of TFB-PCSM in different operation states are introduced.Secondly,the coordinated control strategy between the proposed DC chopper and LCC-HVDC is designed,and the voltage-current stresses of the TFB-PCSMs are investigated.Finally,the ability to mitigate the CF issues and the fault recovery performance of LCC-HVDC system are studied in PSCAD/EMTDC.The results show that the probability of CF of LCC-HVDC is significantly reduced,and the performances of fault recovery are effectively improved by the proposed DC chopper.