I want to design a solar-based inverter for high altitude ranges. So I want to know the parameters to be considered or that would affect the inverter's performance. Please suggest the topologies used for the inverter design at high altitudes, i.e. whether VSI or CSI design will have better performance? Also which software can be used to simulate high altitude inverter design. I also want to know the maximum power capacity of these high altitude inverters so far.
The design parameters for the power electronics and control will be similar to that of run of the mill solar inverters, except for the cooling of the power devices. You will have design for the environmental conditions and consequently, the heat transfer, for the specific environment.
Let's assume you want to design your inverter to run on a high mountain. (Space is a different story alltogether)
At altitude, the air pressure is lower, so that lowers your heat transfer rate. . Simultaneously it is also much cooler, which is better for heat transfer, as your heat transfer is proportional to thermal gradient. i.e. T(high) - T (low).
The Cp values at different pressures for air is readily available in heat transfer tables. Take into account that the value of Cp for air varies for both temperature and pressure.
I agree with others that the main issue to consider is heat dissipation.
As altitude increases convective heat transfer decreases and proportionally more of the heat needs to be dissipated by radiation. Also, insolation (absorption of solar heat per unit area) increases as the atmosphere thins, so if the power supply is exposed to direct sun, or is in an enclosure exposed the the direct sun, this could be a factor working against reliability. This has implications for the effectiveness of fans and heat sinks. I'm not sure the trade-off between the lower temperature and the higher altitude would be an even trade. For example, a heat sink that was intended to be cooled by natural convection might become rather ineffective if the fins of the heat sink all face each other (radiate heat to each other) and the primary means of cooling was designed to be convective. Also, the mass flow-rate of air delivered by a fan is going to decline along with the density of the air. I'd consult the manufacturer of critical heat-dissipating parts and follow their recommendations.
Shruthi ji,
As mentioned by the above comments, the heat factor comes into picture. The Mosfets that we generally use for inverter legs come with heat sinks. the more Current that passes through it, the more is the heat dissipation (cooling) requirement. Also the PV system is not designed to serve peaking loads. So, they are not generally connected to loads demanding large currents during transients. on the whole, I suggest a VSI method for those conditions. the designing and controlling of it is easy. make sure you have a fuse connected to the VSI (series with the source) to avoid peaking currents to be drawn from the panels / batteries.
thanks a lot for all for sharing your views. I would like to know which software can be used to design of high altitude inverter to test its characteristics at various air pressure levels?
Kadal sir, I want to design an inverter for high altitude range and want to know if it can be simulated in softwares like MATLAB, PSpice etc., with various air pressure levels (real time simulation software simulation)
Check all your components for high altitude. If you're not going into space, you only have to worry about capacitors, I'd guess. Also, you not only have to cool your semiconductors, but anything that produces heat, like transformers and the PV panels.
I agree with the others that apart from cooling issues there is nothing different. At 11,000 feet or above the low temperature will compensate for the wind flow for cooling. At best a cooling fan may be added or larger heat sinks for the power devices may be used with their fins vertical.
Dear Shruthi, the most important difference is the regulatory standard you must follow. There are big clearance/creepage and isolation quality requirements for high voltage circuits and components function of altitude, pressure, corrosion, humidity, etc. Just consult the standard requirements applicable to your location.
For simulation you can use LTSpice. It is great for power applications and fully functional without a license to pay.
It might be helpful if you told us what altitude and climate you have in mind. For example, a high-altitude aircraft flying at 20 km is different from a mountain at 5 km. And temperatures are different in different regions of the globe.
But as others have said, it's largely an issue of making sure your cooling systems work; secondarily making sure that each component is OK at the altitude you have in mind, particularly checking electrolytic capacitors. The choice of topology would not be important, or wouldn't be any more important than it is for any other altitude. It's details of the implementation of the topology that you'd need to check on, not the topology itself.
As far as simulation, if the thermal issue might be a concern, you could use some computational fluid dynamics (CFD) programs to model the cooling. If you google thermal CFD, you'll get a lot of the commercial options that are out there. I'm not sure you need that, but it could be a good way for you to teach yourself the effects of air pressure and temperature on the type of cooling system you are working with.
The heat capacity of the air is roughly proportional to the density. Other than cooling, components will perform about the same as at sea level, check cases of sealed elements like caps and batteries for pressure limits.
May be this site is very useful
and gives details for the design and implementation of the power inverter
http://www.semikron.com/skcompub/en/components-59.htm
for the DC/DC converter
may be this article is useful for the solar converter
Efficiency Optimization Through Current-Sharing for Paralleled DC–DC Boost Converters With Parameter Estimation
for the sun tracker
A new approach in tracking maximum power under partially shaded conditions with consideration of converter losses
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