A six-switch solid state variable capacitor with minimum DC capacitance

Abstract

A six-switch solid state variable capacitor (SSVC) with minimum dc capacitance is proposed. A variable ac capacitor (with capacitance variable from 0 to C ac ) is conventionally realized by an H-bridge inverter and a large electrolytic dc capacitor with capacitance of 10 times the ac capacitance value, C ac to absorb the 2ω dc ripple. The proposed SSVC consists of a six-switch converter with two ports. One port connected to an ac capacitor with fixed capacitance, C ac can reduce the dc capacitance to the minimum just for absorbing switching ripples. The fixed ac capacitor controlled by one port absorbs the 2ω component and theoretically can eliminate 2ω ripples to the dc capacitor completely. Therefore, no electrolytic capacitors would be needed. Theoretical analysis of the SSVC is provided. Simulation results are shown to prove the effectiveness of the proposed SSVC with minimum dc capacitance. I.978-1-4799-5776-7/14/$31.00 ©2014 IEEE

Modulation Schemes With Enhanced Switch Thermal Distribution for Single-Phase AC–DC–AC Reduced-Switch Converters

“…Ideally, the shifting should minimize T 1 , T 3 or both to zero, which in other words, means there will be some discontinuous clamping in each fundamental cycle. The clamping can be done by adding offsets to (15), giving rise to those modified references in (17). …”

“…9, depending on the and values specified. Advantages of the proposed scheme represented by (17) can therefore be summarized as improved thermal distribution among switches and lengthened phase-shift range, while retaining the minimum dc-link voltage represented by carrier peak , . This minimum dc-link voltage is the same as that demanded by the B6 converter discussed in Section II.…”

“…Another topology with lesser switches investigated here is the six-switch ac-dc-ac converter proposed recently in [17][18][19][20], which conceptually, is a simplified single-phase version of the three-phase nine-switch converter proposed in [21][22][23][24]. Instead of having three phase-legs with two switches each, the six switches are now divided equally between two phase-legs sharing a common dc-link in parallel.…”

Modulation schemes with enhanced switch thermal distribution for single-phase AC-DC-AC reduced-switch converters

“…Lesser switches in these topologies usually lead to interdependencies between their ac inputs and outputs, and hence a different set of performance requirements, which is presently not thoroughly discussed. It is thus chosen as the theme of this paper, but proposing modulation schemes for all possible ac-dc-ac topologies using lesser switches is nearly impossible since there are many invented over the past decades like in [9][10][11][12][13][14][15][16][17][18][19][20]. The focus has thus been narrowed to two six-switch ac-dc-ac converters.…”

Modulation Schemes for Single-Phase B6 Converters With Two Asymmetrical Terminal Voltages

“…The reduced-switch ac-dc-ac B6 converter was, in fact, proposed in year 2000 for replacing two full-bridges with four phase-legs connected back-to-back. It has since been commonly cited for comparison with other reduced-switch converters proposed in [23][24][25][26], where the main concerns mentioned with the B6 converter are its more restrictive input-output frequency selection and higher dc-link voltage demanded. These concerns have limited the scope of the B6 converter as a single-phase ac-dc-ac converter, but it is still suitable for use with an uninterruptible power supply (UPS) or a power conditioner [14][15][16], where input and output frequencies are the same.…”