Hybrid Multilevel Converter of medium voltage.
Journal Title: Наукові праці Донецького Національного Технічного Університету серія: Електротехніка і Енергетика - Year 2015, Vol 1, Issue 1
Abstract
For the medium-voltage frequency converters are used: a cascade connection inverters (up to 10 kV) and three-level NPC inverters (up to 4.16 kV). ABB released a converter type ACS 2000 with active-neutral-point-clamped (ANPC) multilevel converter technology. It has a hybrid circuit and contains a three-level NPC inverter with a capacitor in the output phases. With IGBT capacitor may be connected in series with the load or phase NPC inverter. The voltage of the capacitor has 0.5Udc. This increases the number of levels of the converter output voltage. Due to the series connection of two IGBT output voltage of the ACS 2000 is increased to 6.9 kV. Number IGBT per phase 16 (total 48). The paper proposed to insert in each phase of a three-level NPC inverter an additional single-phase bridge inverter with DC source. The ratio of voltage sources of inverters 2: 1 or 3: 1. When picking the type of the ACS 1000 converter (12 IGCT + 6 clamping diodes) and the addition of three bridges (12 IGBT- class 3.3 kW) is provided by an increase in the voltage to 6.9 kV with 7 levels (2:1). The input transformer should be added three secondary windings. In a series connection of two IGBT in the basic scheme of a three-l evel NPC inverter (voltage ratio of 3:1) increases the output voltage up to 10 kV, with 9 levels. There are considered the principles of formation of the output voltage using PWM and level quantization. To exclude the change in the direction of energy transfer additional inverter at relative amplitude of the output voltage of 1.8 ÷ 3.4 (3:1) proposed to use the modulation reference voltage third harmonic setting a negative value of its amplitude. The total amplitude of the first and third harmonics does not exceed the corresponding 4 voltage levels. The results of mathematical modeling show that the proposed solutions (voltage ratio 3:1) using PWM it possible to obtain for the output voltage THD=7.2%, using the quantization THD=5.1%. For the design the ACS 2000 THD=14.28%. It also reduces the number of switching of IGBT to the base NPC inverter circuit. Thus, using the principle of voltage asymmetry for hybrid circuits increases the converter output voltage and improving the harmonic content of the voltage, without increasing the number of IGBT.
Authors and Affiliations
A. А. SHAVELKIN, N. L. TYUTYUNNYK
Keywords
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