Pulse Step Modulation Technology Research Articles

Microsecond Overshoot Characteristics of PSM High-Voltage Power Supply

The gyrotron is a critical component of electron cyclotron resonance heating systems and is highly sensitive to the rising edge of the cathode’s high-voltage power supply (HVPS). HVPS is based on pulse-step modulation technology, which requires a rapidly rising edge and low-voltage overshoot. An equivalent mathematical model is thus established to analyze the transient characteristics of HVPS. An optimized control strategy is obtained from detailed theoretical calculations verified via simulations. A time interval of $1 ~\mu \text{s}$ is used to ensure that the voltage overshoot is controlled to within 1% over the rated output voltage range. Finally, the theoretical analysis is verified through experimental tests.

Reconstruction Progress of the COMPASS-D ECRH System on J-TEXT

To make the J-TEXT tokamak more flexible for physics experiments, an electron cyclotron resonance heating (ECRH) system is being developed. The main parts of the J-TEXT ECRH system are donated by the Culham Science Center from the former COMPASS-D, including six 60 GHz/200 kW/5 s (0.5 s) gyrotrons, six magnets, and auxiliary power supplies for the gyrotrons, transmission parts, and so on. For the ECRH system, the output mode of the gyrotron from the former Varian Associates, Inc. is TE $_{{\mathrm {02}}}$ mode and converted to TE $_{{\mathrm {01}}}$ mode for low loss transmission. The TE $_{{\mathrm {01}}}$ –TE $_{{\mathrm {11}}}$ –HE $_{{\mathrm {11}}}$ mode converter is used at the end of the transmission lines for efficient coupling. Then, the high-power wave is injected to the desired area of the plasma by a rotatable quasi-optical launcher. A 100 kV/60 A power supply based on a pulse step modulation technology has been developed to feed all the gyrotrons. The control system based on the compact reconfigurable I/O—9068 platform of National Instruments for monitoring, timing, and protection is being designed. Other units, such as the cooling loops, the launcher, and a spared auxiliary power supply, are on the way. We hope that four subsystems can be finally used on J-TEXT.

Transient Process of Stray Capacitance for PSM High Voltage Power System

At present, based on the features of Pulse Step Modulator (PSM) technology in high voltage power supply (HVPS) is applied to drive the auxiliary heating system in domestic and foreign Tokomak facility. Before design of PSM HVPS, it is necessary to consider the effect of stray parameter existed in HVPS on the dynamic process of HVPS and load. In this paper, based on PSM technology 50 kV HVPS have been completed which is built for EAST auxiliary heating system and the relationship between the stray capacitance and leakage impedance respectively existed in the oil isolation transformer and dry multi-secondary winding transformer is discussed. Finally a stray parameters electrical circuit model of HVPS is presented. At last, from the results of experiment,it is consistent with the results of simulation.

Study and Design a Strategy to Control High-Voltage Power Supply Based on PSM Technology on J-TEXT Tokamak

To energize the gyrotrons of the electron cyclotron resonance heating system, high-voltage power supply (HVPS) at 100 kV/60 A was built on J-TEXT tokamak. The HVPS was based on pulse step modulation (PSM) technology. This power supply has many advantages, including low energy storage and a short protective time in the event of a short circuit fault. In this study, we analyze and compare several common control strategies for PSM power supply. To enhance dynamic performance, the improved queue-up PSM control strategy was proposed. The control algorithm was generated using a controller based on parallel card interface extensions for instrumentation (PXI) technology, which conforms to the control, data access, and communication standard of the ITER. This controller also operates the modules of switch power supply. Experimental results show that the control system is effective and that the PXI controller can rebalance the output voltage and frequency in 60 μs when the module malfunctions under the improved system. Furthermore, the algorithm for the PXI controller is easy to develop and does not require much resources.

A Control System Based on PXI Technology for the ECRH Power Supply of J-TEXT

A 100-kV/60-A high-voltage power supply (HVPS) is developed to supply the auxiliary heating system for a J-TEXT tokamak. This power supply is based on pulse step modulation (PSM) technology and consists of 144 switch modules. To fulfill the isolation, control, and protection requirements, a control system based on the PCI extensions for instrumentation is designed with the PSM technology for the HVPS. Experimental results show that the system has a good control performance and fast response. Thus, the proposed system meets the control requirement of the 100-kV/60-A HVPS.

Optimization Design for a High Voltage DC Power Supply Module Based on PSM Technology

Pulse step modulator (PSM) topology is applied to the EAST auxiliary heating system, which consists of a neutral beam injection (NBI) and the related microwave heating system. This paper firstly analyzes the merits and demerits of the traditional PSM modules adopted by other international companies, and then optimizes the topology of the module using the analysis results. Finally, a new topology for the PSM module (a three-phase neutral-point diode-clamped rectifier) is proposed. This new module overcomes the problems of traditional modules and has better cost-effective performance. The experimental results verify that the new module is feasible for engineering applications.

Analysis of the Soft-Start Circuit of the High Voltage Power Supply Based on PSM Technology

The power supply based on pulse step modulation technology has been widely used as the high-voltage power supply (HVPS) for additional heating systems. The topology contains numbers of converters and multisecondary transformers. For the magnetizing inrush of the transformer and charging current of the converters connecting with the secondary windings of transformer, the power up of the power supply system is quite complex. There are resistor branches series with the transformer and each converter is used to limit the inrush current. A lot of resister branches and parallel contactors in the converter modules are required, and as a result the dissipation and electromagnetic interference inside the module are serious. In this paper, the soft-start circuit is simplified to only one resistor branch. The precharge circuits of the converters, which are connected to the secondary, are diverted from the inside of the modules to the primary winding of transformer. Since the multisecondary transformer powers up at the same time as converters, the capacitors in all converters will limit the ramp up rate of the transformer voltage, and the magnetic inrush current can be ignored. To analyze the characters of the precharge branches, all converters can be equaled as parallel during the soft-start process. The equivalent circuit, a series RLC circuit, is proposed in this paper. A 1.2-kV power supply, contains 12 converters, with soft start has been built up in laboratory. Simulation and experiment results are shown to verify the theoretical analysis. A new soft-start circuit of 100-kV HVPS system was designed.

High voltage power supplies for ITER RF heating and current drive systems

The RF heating and current drive (H&CD) systems to be installed for the ITER fusion machine are the electron cyclotron (EC), ion cyclotron (IC) and, although not in the first phase of the project, lower hybrid (LH). These systems require high voltage, high current power supplies (HVPS) in CW operation. These HVPS should deliver around 50 MW electrical power to each of the RF H&CD systems with stringent requirements in terms of accuracy, voltage ripple, response time, turn off time and fault energy. The PSM (Pulse Step Modulation) technology has demonstrated over the past 20 years its ability to fulfill these requirements in many industrial facilities and other fusion reactors and has therefore been chosen as reference design for the IC and EC HVPS systems. This paper describes the technical specifications, including interfaces, the resulting constraints on the design, the conceptual design proposed for ITER EC and IC HVPS systems and the current status.