Abstract
This paper deals with a novel method which allows the serial connection of Insulated Gate Bipolar Transistors (IGBTs). The different dynamic characteristics of serially connected IGBTs during turn ON and OFF cause a short-term overvoltage stress in the transistors. In contrary to the commonly used techniques, the presented method reduces additional commutation losses by actively correcting turn ON and OFF delays. The presented method uses overvoltages as measured by a peak detector. The correction circuit doesn’t require a high speed Analog-Digital converter (ADC) or high speed computation. The target power switch unit consists of two serial connected transistors with two identical parallel branches. The well-known 2-level inverter topology equipped with the power switch unit can be connected directly to the high-voltage grid. This converter topology was demanded by our industry partner for 11 MW mining machines. The paper contains a laboratory experiment conducted on a serial-parallel IGBT power switch unit with a tested output power of 1 kW. DOI: http://dx.doi.org/10.5755/j01.eee.22.1.14110
Highlights
Actual voltage, along with the physical limits of the current of semiconductor power switches, lead to serial and parallel connection of power components or whole power converters in high power applications (e.g. STATCOM [1], HVAC and HVDC)
This paper describes a possible variant of the implementation of the serial-parallel Insulated Gate Bipolar Transistors (IGBTs) switch
The resulted error signal is the input of PI (Proportional-Integral) controllers, whose outputs are the relative delay between transistor A and transistor B
Summary
Along with the physical limits of the current of semiconductor power switches, lead to serial and parallel connection of power components or whole power converters in high power applications (e.g. STATCOM [1], HVAC and HVDC). This paper describes a possible variant of the implementation of the serial-parallel IGBT switch It is a power unit with two parallel transistors connected in series to the other two parallel transistors (see Fig. 1). There are several methods that compensate for the different dynamic behaviour of IGBTs. The presented principle is based on the active compensation of different turn ON and turn OFF times of serially connected IGBTs. A combination of different methods is usually used in serially connected IGBTs. The presented method is complementary to other IGBT voltage balancing methods: RC or RCD (Resistor, Capacitor, Diode) snubber [4]–[6], active clamping [7], [8] and is analogous to the presented one in [9].
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