powerline modem over dc line

Mar 25, 2007 1 Replies

Hi, has someone any kind of experience or information about implementing a communication over a dc power bus. In particular that dc bus is the output (700V) of various step-up machines that are in parallel elevating the voltage of independent photovoltaic strings in order to be the input of a three-phase inverter to be the power injected in a low-voltage three-phase distribution power line. The frequency of the switching of the machines is arround 15KHz.



The first idea is the use of comercial PL modems like ST7540. But I has the impression that perhaps this would be not correct at all, because these are implemented in order be used in a residencial powerline with the type of transmision caracteristics of them (attenuation,...), with the types of loads characteristics in that nets, and with the type of noise superimposed also. In consecuence the frequency of the carrier, characteristic of the transmisor driver, and receiver filters and perhaps the type of modulation are adecuated to this (typically FSK or BPSK instead of spread spectrum for example), but not to my case.



What do you opinion about this?



It is probably not a good idea.

Typically, on a DC bus, you are trying to avoid noise. You usually have capacitors and other filters to try and eliminate noise as much as possible. Most powerline data transmission is on an AC bus, where such noise is a little (not much) more acceptable.

If you need to monitor and control solar panels, just run some CAT5 out to them, and do yourself a huge favor... 8-)

Charlie

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