Right, the MPP Voltage of the turbine would hardly vary much if at all. The hydro voltage won't have to vary, or go up, unless diversion control is absent on the battery side. Otherwise, the input (hydro) output voltage will have to rise when the batteries get fully charged, or battery loads go away.
A clipper circuit on the hydro side would be an alternative and provide a minimum load to the turbine as well so it doesn't have to free-run. (I kinda like the term "FreeLoad" myself) boB --- In [email protected], Max Enfield <[EMAIL PROTECTED]> wrote: > tajuddin waris wrote: > > > > Dear > > All member > > > > As we know that MPPT (maksimum power point tracking) have been used in PV and wind turbine in order to improve efficiency the whole system. Is there any research application of MPPT for microhydro particularly microhydro driving small turbine like pump as turbine ? > > > > regard > > > > waris > > > In previous postings to this group I have stated that I gave up counting once > our accumulated experience using what are now called AERL Hydromax controllers > exceeded 50 years. The Hydromax controller is a modified Maximizer used for > MPPT of PV arrays. The main modification is that the automatic tracking feature > has been disabled and a manual adjustment used instead. It has proved itself to > be an excellent, flexible, efficient and robust arrangement that we have used > many times. The Hydromax controller is placed between (in an electrical sense) > the DC hydrogenerator and a lower voltage DC load, which is usually a 12V, 24V > or 48V battery. > > The method is suitable only when the turbine/generator can be freewheeled and so > this typically limits the method to low and medium head sites. We have > successfully used this approach for Banki-crossflow, Turgo, Pelton wheel and > Aquair UW propellor turbines. A novel application is undergoing trials in > southern NSW (Australia) on a large travelling irrigator. Some of the water > delivered under pressure to the irrigator passes through a propellor turbine and > an AERL Hydromax controller is used to control the generation of electricity > required for on-board use. > > Any MPPT device requires a real time algorithm to determine the MPP. With AERL > units this is done once every 25 seconds by momentarily allowing the input to go > to open circuit voltage and then bringing this voltage down until there is no > further improvement in output. This is OK for PV but with micro- hydro it > presents at least two difficulties. Firstly it induces an unpleasant voltage > spike and secondly the spinning reserve of the turbine/generator defeats the > controller's efforts to determine OC voltage within the few milliseconds time > frame it allows itself. This is why a manual adjustment is used. > > It may at first appear that manual setting of the MPP defeats the benefits of > automatic tracking that has proved so useful for PV. However this is not so and > although the reason is not straightforward, I will try to explain it simply. > > As the head and flow characteristics of a turbine site vary, due to the season > or rainfall level, usually it is the flow rate rather than the head that changes > dramatically. It is unusual for the net head to vary by more than 30% above or > below some average value. The output voltage characteristics of a generator > depend only on the net head and hardly at all on the flow rate. Furthermore, > any > change in net head results in proportionately a much smaller change in the MPP > - only about half as much. For example a 30% increase in net head will increase > the MPP voltage by only 14%. > > An additional stabilizing factor is that at the maximum power point the power > curve is rather flat. So operating a few percentage points either side of this > point causes only a small reduction in output. Using the above example, if the > MPP voltage is 14% above the operating voltage the reduction in output is barely > 2%. So, for all practical purposes, the reduced efficiently due to manual > rather than automatic setting of the MPP is tiny. > > The relationship between head variation and reduced efficiency involves a > quartic polynomial. If anyone is interested in the formula they can contact me > directly. > > Regards, > > Max Enfield > Planetary Power > www.planetarypower.com.au Does your company feature in the microhydro business directory at http://microhydropower.net/directory ? If not, please register free of charge and be exposed to the microhydro community world wide! NOTE: The advertisements in this email are added by Yahoogroups who provides us with free email group services. The microhydro-group does not endorse products or support the advertisements in any way. More information on micro hydropower at http://microhydropower.net To unsubscribe: send empty message to [EMAIL PROTECTED] Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/microhydro/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
