A unity power factor three phase PWM SCR rectifier for high power applications in the metal industry

Abstract

Abstract-A new thyristor current-source rectifier that achieves unity power factor, low-current total harmonic distortion (THD), and dc-bus current and voltage control is presented. The rectifier is suitable for high-power applications such as induction heating and dc arc furnaces. It combines a traditional six-pulse thyristor bridge and a dc chopper that together solve power quality problems such as poor power factor and flicker generation. This topology achieves low input current THD and dc power control without additional power-factor-correction equipment, harmonic trap filters, use of multiple pulse rectifiers, or high--factor transformers.

Improved Control Strategy Based on Space Vectors for Suppressing Grid-Side Current Harmonics in Three-Phase Current Source Rectifiers with a Hybrid Switch

“…It is only feasible to attenuate the harmonics by adding a filter to the main circuit. However, this increases the cost and size of the whole circuit [10]- [12]. Judging by the simulation results, improving the switching frequency by using the optimal current source space vector control will cause certain grid-side current distortions.…”

“…In other words, it can ensure normal conduction of the current source space vectors of the circuit. This is validated by simulation and experiment in the following sections [10]- [15]. …”

Soft-switching of a hybrid bi-directional Current Source Converter

“…Laboratory experiments are thus required for obtaining this information. These were carried out in [5], mostly to show that an SCR can be actively commutated. However, a derating factor for parameter turn-off time (t q ) available in standard data sheets was not discussed.…”

“…These problems can be overcome by replacing the six SCRs with six switches and with pulse width modulation (PWM) techniques [2][3][4]. Hybrid topologies with a dc side force-commutated switch actively commutating the SCRs of a three-phase bridge can also overcome these problems with a lower cost [5][6]. However, the power flow becomes unidirectional and the angle between currents and voltages in the ac side of the converter is limited within ±30°.…”

Starting Strategy of Thyristor Power Supply in Parallel Resonant Induction Heating on Heavy Load

“…The TPSPRIH raised more concern because it can provide more efficient power, but it's difficult to start on heavy load because of its big problem in its popularization and application, especially when it's starting on heavy load, the success rate of starting is extremely low [3][4][5]. Although many scholars have studied on it, such as the [6] studied the pre-charge starting, the [7] proposed the double auxiliary bridge starting, the [8] presented the load premagnetizing starting etc., but their starting methods are mainly by means of changing topology of circuit to increase the medium-frequency voltage when converting the current so as to improve the success rate of starting on heavy load.…”