Power supply prototype using SiC MOSFETs for energization of electrostatic precipitators
Authors
Sønderskov, Simon Dyhr ; Jørgensen, Asger Bjørn
Term
4. term
Education
Publication year
2016
Submitted on
2016-06-01
Pages
119
Abstract
Elektrostatiske filtre (ESPs) renser industrielle røggasser ved at fjerne støv og andre partikler. De kræver meget højspændte strømforsyninger. I dag bygger disse ofte på silicium-thyristorer eller IGBT’er (insulated-gate bipolar transistors). Nye komponenter i siliciumkarbid (SiC) kan skifte hurtigere og mere effektivt ved høje spændinger og kan derfor forbedre strømforsyningerne til ESP’er. Vi har designet en højspændingsforsyning baseret på en synkron boost-konverter og drevet den i discontinuous conduction mode (DCM) for at eliminere tændingstab. Fordi konverteren bruger flere SiC MOSFET’er i serie, skal spændingen deles jævnt mellem dem (spændingsbalancering), et område med begrænset tidligere forskning. Mange metoder tænder og slukker alle komponenter samtidigt, men den meget hurtige switching og de høje spærringsspændinger i SiC kan give spændingsspidser (overshoot), svingninger (ringing) og vanskelig spændingsdeling. For at imødegå dette byggede vi et modulært kredsløb, der tænder og slukker komponenterne i en kaskaderet, forskudt sekvens. Vi testede det i laboratoriet med en standard double-pulse test. Sammenlignet med tidligere studier brugte vi flere seriekoblede komponenter og opnåede bedre spændingsbalancering. Ved drift i DCM ved 50 kHz blev spændingsdelingen dog dårligere. Vi analyserer årsagerne til ubalancerne og skitserer forbedringer til fremtidige design.
Electrostatic precipitators (ESPs) clean industrial exhaust by removing dust and other particles. They need very high-voltage power supplies. Today these supplies often use silicon thyristors or IGBTs (insulated-gate bipolar transistors). New Silicon Carbide (SiC) devices can switch faster and more efficiently at high voltages, which may improve ESP power supplies. We designed a high-voltage supply based on a synchronous boost converter and operated it in discontinuous conduction mode (DCM) to eliminate turn-on losses. Because the converter uses several SiC MOSFETs connected in series, the voltage must be shared evenly across them (voltage balancing), a topic with limited prior research. Many existing methods switch all devices at the same time, but the very fast switching and high blocking voltages of SiC can cause voltage spikes (overshoot), oscillations (ringing), and difficult voltage sharing. To address this, we built a modular circuit that turns devices on and off in a cascaded, staggered sequence. We tested it in the lab using a standard double-pulse test. Compared with earlier studies, we used more series devices and achieved better voltage balancing. However, when running in DCM at 50 kHz, the voltage sharing worsened. We analyze the causes of these imbalances and outline improvements for future designs.
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