Streszczenie. Artykuł przedstawia wyniki symulacyjne układu 2 poziomowego, 3 gałęziowego falownika z przewodem neutralnym. Przekształtniki tego typu stosowane są w zasilaczach bezprzerwowych UPS. Zaproponowana struktura sterowania zapewnia stabilizowanie sinusoidalnego napięcia wyjściowego z niską zawartością wyższych harmonicznych przy nieliniowym lub niesymetrycznym obciążeniu. (Sterowanie 3-gałęziowego 4-przewodowego falownika z filtrem pasywnym LC z nieliniowym lub niesymetrycznym obciążeniem) Abstract. Article presents simulation results of two-level three phase inverter with neutral wire. Such inverters are commonly used in uninterruptible power supplies. The proposed control structure enables sinusoidal output voltage with low THD value under nonlinear or unbalanced load.Słowa kluczowe: sterowanie, falownik czteroprzewodowy, UPS, nieliniowe obciążenie, niesymetryczne obciążenie.
This paper describes a new concept of a three phase switch dedicated for low voltage capacitor bank for reactive power compensation (RPC). The switch combines electromagnetic relay with a solid-state valve. In contrast to state-of-the-art solution where thyristors are used, the proposed device utilizes fully controllable IGBT transistors. IGBT gives possibility to turn-on the switch without inrush current at the voltage zero-crossing, and moreover, turn-off in a moment which ensures that capacitors in all phases are discharged and there is zero voltage across its terminals. This solves well known phenomena of thyristor based solutions, where an increased voltage stress for a switch and capacitor exists. The advantage of the proposed circuit is that the capacitor bank can be turned on immediately after its disconnection. As a result, response time of reactive power compensation system can be significantly shortened. Reactive power compensator's (RPC) capacitors are often dealing with distorted grid voltages. Therefore the detuning inductors are required to cut-otT higher harmonics currents. It creates a problem for the proposed hybrid switch with interrupting inductive currents. Paper describes structure of hybrid switch and its operation with capacitor bank and detuning inductor. Descriptions are verified by laboratory model measurements.
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