INVERTERS: The Investigation to the * INVERTERS: The Investigation to the 07/16/96 optimal topology to the designing of a sinewave inverter range for the use in static as well as mobile applications Presenter: Dr Gawie van der Merwe *

* Background 07/16/96 PV and Mobile Inverters with a sinewave output is the optimal requirement. Various Topologies exist. Investigations done in order to search for the optimal topology. Investigation towards: Efficiency Cost Reliability Manufacture (Complexity/Simplicity) *

Sinewave Inverter Topologies * Sinewave Inverter Topologies 07/16/96 CVT (Constant Voltage Transformer) 50Hz Transformer Push Pull Primary- Full Bridge switching in Primary with series line Inductor High Frequency Isolation Transformer and Secondary H-Bridge Control Series or Parallel Transformer switching *

A) Constant Voltage Transformer * A) Constant Voltage Transformer 07/16/96 (Ferro Resonant Transformer) *

B) 50Hz - Transformer Topology * B) 50Hz - Transformer Topology 07/16/96 Various “50Hz” transformer topologies exist Push-pull - Inductor in primary Push-pull - Inductor in secondary Full Bridge Inductor in primary *

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* Topology B1 07/16/96 Push-pull - Inductor in primary *

Push-pull - Inductor in primary * Topology B1 07/16/96 Push-pull - Inductor in primary Advantages Simple manufacture & design Mosfet drive circuit referred to ground Disadvantages Voltage overshoot over devices - leads to voltage rating increase - Reduction in efficiency No-, or limited control over free running inductor current “Skewing” of transformer often occur. *

Topology B2 Push-pull - Inductor in secondary * Topology B2 07/16/96 Push-pull - Inductor in secondary Primary side Push-pull, series inductor in secondary *

Push-pull - Inductor in secondary * Topology B2 07/16/96 Push-pull - Inductor in secondary Advantages Simple manufacture & design Mosfet drive circuit referred to ground Disadvantages Voltage overshoot over devices - leads to voltage rating increase - Reduction in efficiency No-, or limited control over free running inductor current “Skewing” of transformer often occur. *

Topology B3 Full Bridge Inductor in primary Most popular used topology * Topology B3 07/16/96 Full Bridge Inductor in primary Most popular used topology *

Full Bridge Inductor in primary * Topology B3 07/16/96 Full Bridge Inductor in primary Advantages Complete control over primary side inductor current Uni-as well as bi-polar pwm control strategy possible Simple manufacturing Disadvantages System design is more complex Inverter efficiency is load dependent *

C) High Frequency Isolation * C) High Frequency Isolation 07/16/96 *

* 07/16/96 C) High Frequency Isolation Transformer with full H-bridge Control on Secondary High frequency isolation reduce physical size Direct output control leads to better output waveform control and reduced distortion *

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High Frequency Isolation Transformer * High Frequency Isolation Transformer 07/16/96 Advantages Units generally more mobile Possible to limit battery current drawn to a “smooth DC” Good efficiency with a non linear load Disadvantages Design is complex Manufacture is complex High cost *

D) Transformer - series and/or parallel switching * D) Transformer - series and/or parallel switching 07/16/96 A wide range of topologies exist A combination of various Transformer switching topologies Transformer secondary is in series Separate output voltage & frequency for each transformer *

Transformer-series and/or parallel switching * Transformer-series and/or parallel switching 07/16/96 *

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Transformer -series and/or parallel switching * Transformer -series and/or parallel switching 07/16/96 Advantages High running to overload ratio is Very popular design Advantages for motor startup High efficiency Disadvantages Control complex Manufacturing is complex Inverter is big and bulky *

Summary Matrix transformer topology * Summary 07/16/96 Different topologies have advantages for different applications Both topology A, B1&B2, (50Hz topology) are outdated High frequency option, has mobility & weight advantage Output distortion under all conditions low Matrix transformer topology Physical dimensions restrains mobility Ideal for short period overload power peak/Mass ratio is good *

Estimated Inverter Manufacturing Costs (Same Input Power Stage) * Estimated Inverter Manufacturing Costs (Same Input Power Stage) 07/16/96 Input power stage same for comparing Calculation done on continues rating without forced air cooling Cost calculated on discreet units *

Non linear load as a % of total power consumption * 07/16/96 Non linear load as a % of total power consumption Non linear loads - high percentage on power application below 1Kva typical loads, computer, fluorescent lights, video Higher power application, more resistive, i.e. Microwave, Hairdryer etc. < 1Kva most sensitive to PV applications *

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Topology Suggestions for Power Levels * Topology Suggestions for Power Levels 07/16/96 Power Rating High Frequency Full Bridge 50Hz Matrix Config. 100-600W Mobile (most cost efficient) 50% Advantage on perm installation 60% Too expensive 10% 400W-1500W Mobile General 70% PV-Permanent 100% 40% 1000W-2,5Kw PV-Permanent 70% PV & Mobile Stackable units in parallel 70% PV Permanent Best choice 80% 2Kw-5Kw Stackable parallel combination 100% Stackable Units 80% Mobile 30% (Percentage indicates topology choice for the application) *