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For lack of effective methods of unified trigger and clock, the former poloidal field (PF) converter data acquisition system on EAST met the trouble of asynchronous sampling during the process of data acquiring. In this paper, a circuit to synchronize trigger and clock is described according to the requirement of PF converter data acquisition system. So that the operation analysis and fault diagnosis of EAST experiment can be fulfilled accurately. Hardware selecting, circuit designing, driver writing and program designing are included in this project. With this method, every DAQ card starts or stops the process of DAQ on unified trigger and clock signal which controlled by upper-computer via Ethernet.

This paper introduces a high power dc testing platform for components test of ITER poloidal field converter prototype. The platform is composed of four phase-controlled rectifiers in parallel with the same direction and output up to rated 120 kA long pulse and 400 kA maximum impulse dc current. In this paper, the circuit model is built and circuit analysis is performed to observe the dynamic behaviors. Due to the feature of strong coupling among paralleled branches, two different control strategies are compared, which respectively are decoupling control and dual closed-loop control. Two operation modes, long pulse model and impulse model adopt their own strategy. Experiments results are performed and the operation modes make an agreement with the theoretical analysis.

Thyristor is the key component for the PF converter module, which is directly to affect the operation performance of the PF converter. This paper mainly presents the analysis of the thyristor type and its parallel number selection used in the PF converter module, based on two worst fault conditions of the PF converter, two different analysis methods are applied to calculate the parallel number of three types of preselected thyristors in details, and the characteristic tests of the preselected thyristors have been done and compared, according to the results of the analysis and test of the preselected thyristors, the proper type and parallel number of the thyristor are chosen and used in the full scale prototype of the PF converter module.

The dynamic stability parameters are the important design inputs for the structure design of the PF converter. This paper mainly presents the analysis and calculation of the dynamic stability parameters for the PF converter. Based on the PSCAD software and the real operation conditions, the simulation model of the PF converter power supply system is built firstly, then the main fault conditions of the PF converter are analysed in details using the simulation model, and the analysis results are crosschecked by the theoretical calculation, lastly, the dynamic stability parameters are given based on the analysis and calculation results, which are the important basis and reference for the structure design and fault protection strategies of the PF converter.

For lack of effective methods of time synchronization, the former poloidal field (PF) converter data acquisition system on EAST met the trouble of asynchronous sampling during the process of data acquiring. In this paper, a method to synchronize time is described according to the requirement of PF converter data acquisition system, implements and verifies along with the regular upgrade of hardware and software on PF converter. With this method, a master node with a hardware clock synchronizes time of the slave nodes on the private time network in each second, and the maximum offset time between the master and the slave is

The proper RC snubber circuit is of great importance to protect the thyristor against overvoltage during the turn-off process. This paper mainly presents the design of commutating over-voltage RC snubber circuit for ITER poloidal field (PF) converter module. Based on the reverse recovery transient model of the multi-parallel thyristors and commutating overvoltage circuit model, the RC snubber parameters of PF converter module are obtained by the detailed theoretical calculations, and then the simulation analysis and the commutating overvoltage test of the prototype are done to verify the RC snubber components selection, the simulation and test results show that the design of RC snubber circuit can meet the commutating overvoltage protection requirement.

This paper presents the thermal analysis of a high-current dc disconnector which will be used in ITER poloidal field converter. The analysis is based on the finite element method, and thermal-electric module in ANSYS Workbench is adopted. An analysis model involving the effect of contact resistance is first built and then a thermal simulation is performed under the nominal working condition. In addition, the temperature rise test of the dc disconnector prototype has been done to verify the analysis result. The results from the simulation and the prototype test are consistent with each other very well. Proved by the test result, the analysis method presented in this paper is of valuable reference for the structure design of high-current dc disconnectors.

Clamp structure is a main part in thyristor installation technique. This paper presents the design and analysis of the thyristor clamp structure for ITER poloidal field converter unit. The clamp structure is designed to provide a mounting force up to 145 kN. Its structural stability is verified by a corresponding simulation and a static test. The contact effect of single side clamp and double side clamp is analyzed and compared, and double side clamp structure is applied in the design. In addition, an extra simulation is performed to study the influence on the contact effect due to unbalanced mounting forces. And a test is also performed. The analysis method and result presented in this paper will be very valuable in the design and analysis of clamp structure used in the converter systems.

The proper fuse selection is of great importance for the safety and reliability operation of the PF converter. This paper mainly presents the high speed fuse selection analysis of the PF converter module, combining with the characteristics of the fuse and thyristor, the normal operating condition and the possible worse fault cases of the PF converter are analysed in details, and the proper type of the high speed fuse is chosen and used in the PF converter module prototype, the relevant tests of the selected fuse are done to verify the selection. The test results indicate that the fuse selection can meet the design requirements of the PF converter module.

The current sharing of bridge arm is very important for the design of external bypass, which provides protection for the ITER poloidal field converter and magnets in fault conditions. Thyristors in parallel should withstand short peak current for each arms. In this paper, the method based on inductance matrix is presented. After theoretical analysis and simulation, the prototype has been manufactured by China industry. The test results on the prototype show that the current sharing performance of the prototype can fully satisfy the design requirement.

This paper presents the fault conditions and the corresponding structural analysis results of high-power dc reactor, which is applied to ITER poloidal field converter module. According to the fault analysis of the PF converter system, two worse fault conditions, i.e. the dc short-circuit downstream dc reactor fault and anti-parallel bridge bypass fault are introduced. Based on the finite-element method, the corresponding structural analysis is presented in details. The results of the fault current test show the reliability and availability of the prototype structure. In addition, the fabrication is also introduced in this paper.

This paper presents the eddy current heating effect on the surrounding components of high-current dc reactor, which is applied to ITER poloidal field converter. According to the normal operation analysis of the PF converter system, the ripple current can be up to 3 kA with the frequency of 300 Hz. Based on the finite element method, the eddy current heating effect on the surrounding magnetic components with high permeability, focusing on the floor rebar, steel column and roof beam, are analyzed in this paper, which provides an essential reference for the installation design of the stacked dc reactors.

International Thermonuclear Experimental Reactor (ITER) Poloidal Field (PF) converter fault will lead to the major accident of power supply system or even damage it. In this paper, detailed analysis on typical fault types of ITER PF AC/DC converter system under different operation mode is presented. Three typical fault were listed and analyzed, such as three-phase short circuit in second side of converter transformer, short circuit upstream DC reactor and thyristor failure. Theoretical analysis and simulation for each fault are carried respectively.

This paper describes the structure design of external bypass which provides protection for ITER poloidal field converter and magnets in fault conditions. It needs to withstand short peak current up to 350 kA within 80 ms according to the technical requirements. In order to meet the dynamic stability requirement, a special prototype design structure is presented based on the theoretical analysis and simulation. Now a full prototype has been manufactured by China industry, and the dynamic stability test of the prototype has also been accomplished successfully. It shows that the structure can fully satisfy the design requirement and the reliability has been improved.

The control system for poloidal field (PF) in ITER is running in a cluster of distributed controller nodes connected by a soft real-time network. The non-functional performance of network communication, such as latency and jitter, plays an important role in the control system. We analyze the essential of network communication for PF converter control system with stringent real-time requirement and identify the feasibility of the conventional time division method at the request of current data size. However, in order to meet the increased demand for communication data size, we present the design of a timed-token based method and its network scheduler. A test scenario involving a cluster of local control cubicles has been set up to verify the method. The test result shows the timed-token method is more competent to the conventional method and more qualify to the networked control system of PF converter. Meanwhile, in other network with similar architecture, implementation of the timed-token method can guarantee real-time performance as well.

This paper describes the bypass circuit design applied to International Thermonuclear Experimental Reactor (ITER) poloidal field converter system. In the baseline design, an internal bypass scheme was designed for purposes of quench protection and reactive power reduction by bypass operation. However, due to the potential risks that exist in case of fault protection, internal bypass scheme is abandoned finally and external bypass scheme is proposed to replace the internal bypass design. In this paper, the weakness of internal bypass design has been reviewed and the reliability of external bypass design at different sites is analyzed. Simulations based on SIMULINK are performed to confirm the reasonability and availability of external bypass proposals.

Current sharing control is used to assure the stability of unbalanced current between two paralleled bridges when International Thermonuclear Experimental Reactor poloidal field converter operates in parallel mode. This paper, based on the equivalent model of current sharing circuitry, describes the dynamic behavior of current sharing control by means of frequency and time domain methods. A control strategy is proposed and simulations are performed to verify the effectiveness of the proposed strategy in current sharing control.

The dynamic behavior of circulating current control of International Thermonuclear Experimental Reactor poloidal field converter is the subject of this investigation. Four quadrants operation with circulating current has proved to be a reasonable way to perform smooth transition at the zero crossover of load current. In this paper, a control method, specially for circulating current control, on the basis of equivalent circuit, is proposed. With simulations it is verified that the circulating current can be controlled in such a way that it never become zero, and load current can change polarity without any discontinuity and dead zone, even if in the case that the total reference voltage of converter changes rapidly.

A snowflake divertor magnetic configuration (Ryutov in Phys Plasmas 14(6):064502, 2007) with the second-order poloidal field null offers a number of possible advantages for tokamak plasma heat and particle exhaust in comparison with the standard poloidal divertor with the first-order null. Results from snowflake divertor experiments are briefly reviewed and future directions for research in this area are outlined.