Contents I. Introduction
The auxiliary heating system of Tokamak normally means lower hybrid current drive (LHCD), electron cyclotron resonant heating (ECRH), ion cyclotron resonance heating (ICRH), and so on. The technology of pulse step modulation (PSM) switching power supply is widely used in the high-voltage power supply (HVPS) which plays an important role in the auxiliary heating system [1]–[3]. The HVPS based on PSM technology has the advantages of fast opening and closing, high reliability, and modularization, etc [4], [5]. Due to the modules of HVPS being in series, the output voltage can be achieved by controlling fast semiconductor switches [6]. As is shown in Fig. 1, the PSM technology is applied in a 4.6 GHz LHCD system. The system consists of four identical power supplies. For one power source, the 10 kV is sent to two multi-circle winding tap transformers after ±7.5° phase shifts, and the secondary windings are connected to the rectifier. So the 24 pluses rectification circuit consists of four modules can largely decrease the ripple wave of the output voltage [7]. The transformer of one HVPS has 32 delta- and 32 wye-connected secondary windings [8], [9]. As the load’s demand for dc voltage changes, the harmonic current of 10 kV changes frequently with the dynamic operation of module number. It has a great negative impact on the normal running of the sensitive equipment in the tokamak. Even worse, the parallel resonance caused by the effect of the system impedance and the filter device may amplify the specific harmonic current, which will lead to more serious consequences such as protection actions and equipment trouble [10].
PSM technology of cathode HVPS for a 4.6 GHz LHCD system.
