ES2273576A1 - Solar control equipment for photovoltaic concentrators adjusts parameters internally after errors are automatically collected - Google Patents

Abstract

Electronic controller calculates, processes and measures electrical variables, and integrates an internal clock, an electronic module for controlling an electrical motor, current and voltage sensors, a global solar radiation sensor, and sensors of rotary axes. Connection of sensors and commutation modules of power line of photovoltaic concentrators are integrated in equipment. Solar events are calculated based on time and generic model of errors in installation and fabrication of concentrators or internal clock. Parameters are internally adjusted after automatically collecting the errors. An independent claim is also included for a control method.

Description

Equipment and follow-up control procedure solar with self-calibration for photovoltaic concentrators.

The present invention relates to an Equipment of Solar Tracking Control with self-calibration capability for photovoltaic concentrators The present team is capable of control the solar tracking of photovoltaic concentrators in one or two axes in any arrangement, with very high precision.

Background of the invention

The mechanical solar trackers that carry on its mounting surface optical systems for the concentration of direct solar radiation, and its subsequent conversion into electricity through thermal or photovoltaic processes, they require an accuracy of pointing to the sun as much as The higher the concentration factor used. So the precision required, in these systems, it is usually below the grade, and often in the tenth grade range. Whether they take into account the large dimensions of the surfaces of assembly, or openings, of these followers, currently in the range Approximately 25-250 m2, the difficulty of pointing to the sun with such precisions. For achieving this objective on the one hand is a necessary condition that the solar tracker meets strict stiffness specifications, and that Its transmission provides high positioning resolution. On the other hand, a device capable of controlling so is required. permanent solar tracking with the specified accuracy, without that it is interfered with or deteriorated by the appearance of clouds, and that alternatively effectively manage the situations of interruption of solar tracking, either during the night, or by cause of high winds that put at risk the structure of the follower, or excessively high temperatures in the light receptors concentrated that can damage them.

To date solar tracking control It has been approached primarily by two paths, (i) based on aiming sensors that feedback motor control that drive the rotation of the axes of the solar tracker (ii) through equipment based on microcontrollers or microprocessors that from the calculation of solar ephemeris obtain the coordinates of the sun at every moment using these as a slogan to the aforementioned motor control. The first approach is the object of Spanish Patent ES-488887, or of the Patent of USA US-3917942, in whose line they have been proposed subsequently numerous variations. The underlying principle is the use of a two or four segment photodiode in such a way that each tracking axis is associated with a pair of segments, and that is mounted inside a collimator. This allows, within the range of a certain angular aperture (field sensor vision) imposed by the length of the collimator, detect the deviation of the solar vector with respect to the axis of the collimator in one or two tracking axes, provided that the outputs of current of the pair of segments associated to an axis are not equals, and that will control motor control with the aim of cancel these deviations. In general these procedures called generally of "closed loop", although simple and cheap of implement, and able to be precise enough under skies cleared, they handle with difficulty in cloudy conditions intermittent and are generally inefficient to show relocate to the sun after periods of concealment or manage the aforementioned solar tracking interruption situations. further in high precision applications it is difficult to achieve mounting for the sensor such that its aiming axis of the match the axis of the concentration system that mounts the follower in its opening, defined as the one that maximizes the electrical power generated. Finally the field experience accumulated with these devices indicates that they require maintenance and periodic calibration. In sum, although the follow-up control closed loop solar can be effective in applications laboratory measurement, where its use is limited to optimal days and in in any case they have frequent maintenance and assistance, they are far of being an ideal solution for the control of solar plants endowed with several tens of followers and in which the maximum long-term reliability with the smallest maintenance possible. Follow-up control based on the calculation of ephemeris Solar has its first proposals in the Spanish Patent ES-522081, or US Pat. US-4215410. The availability of solar ephemeris with accuracies below one hundredth grade and in many cases with fairly compact analytical expressions, he also suggests, since the beginning of the developments in solar concentration, the possibility of a follow-up control based on its calculation in real time, are the so-called "open loop" strategies. With the proliferation of powerful microprocessors and Low-cost microcontrollers will make the production of electronic solar tracking control equipment, which on par that implement strategies based on the calculation of solar ephemeris that enable a much greater robustness and efficiency in the tracking that achieved with pointing sensors, achieve great versatility in the management of alternative situations and emergencies, and the integration of additional capabilities e.g. remote monitoring, user interface etc. that facilitate and They reduce the cost of maintenance.

The accuracy attainable with strategies based on the calculation of solar ephemeris, is ultimately limited in the chapter of the follow-up control due to the accuracy of these ephemeris and the resolution of the position sensors that feed the orientation achieved in each control tracking axis In the chapter of the tracker in one or two axes that is controlled, the tracking accuracy limits the positioning resolution of the mechanical transmissions used, their slack function, reduction employed etc. These last limits are to be considered during the design stages and must be adjusted so that the specifications are met. But in addition, in order to achieve this precision of aiming for which it has been designed through an open-loop monitoring control, it will be necessary on the one hand that the internal time based on which the solar ephemeris be calculated is kept within certain Precision margins and, on the other hand, that the reference set by the mechanical follower assembly and concentration system that it carries coincides at all times with the reference of the solar ephemeris. Whether this identity is achieved between referentials will depend on the one hand that a correct installation and orientation of the tracker in the field is achieved, as well as its axis position feedback sensors, and the concentration system mounted on the follower opening, but also in certain aspects, of the manufacture and precise assembly of the follower. These differences between referents introduce monitoring errors in a control based on solar ephemeris for which two fundamental types of correction procedures have been proposed: (i) based on the classical linear control theory (Luque-Heredia, I. et al "A PI Hybrid Sun Tracking Algorithm Sun Tracking Algorithm for Photovoltaic Concentration" Proceedings 19th European Photovoltaic Solar Energy Conference, Paris, 2004) that try to predict the error that will occur in the follow-up of the follower from previous measures of this error, and (ii) based on the construction of tracking error tables and their periodic update procedures (Arboiro, JC & Sala, G. "Self-learning tracking: a new control strategy for PV concentrators", Progress in Photovoltaics, 5, 1997). These correction procedures ultimately result in routines that correct the coordinates initially served by the solar ephemeris and thus require some means to provide pointing errors, such as a pointing sensor, they are called "hybrid" strategies because they take resources and procedures from both the "open loop" and "closed loop" strategies described above.

Description of the invention

The present invention relates to equipment electronic solar tracking control that has the resources needed to implement a new control strategy solar tracking especially suitable for concentrators photovoltaic

Physical Description of the Tracking Control Team

In essence, the team is based on a microprocessor or microcontroller, an internal clock based on a quartz oscillator, and an electronic motor control unit DC or AC electric as appropriate. He microcontroller has a series of inputs and outputs digital and also analog inputs, which are equipped with external signal conditioning circuits required allow the reading of current sensors with different sensitivity, a global solar irradiance sensor, and / or a sensor voltage, and / or a pointing sensor as described more above based on the general principle of quadrant photodiode under collimator. The equipment is also equipped with sensors that they inform the orientation at each moment of the different axes of monitoring under control e.g. incremental optical encoders or Absolutes, inductive sensor systems etc.

Solar Tracking Control Routine

The microcontroller, by computing the programmed solar ephemeris, is capable of producing the pair of coordinates (azimuth and elevation) of the solar vector i.e. the vector that It has its origin in the location of the follower and points to the center of the solar disk, depending on the time supplied by the watch internal and of the geographical coordinates in which it is found that they have previously introduced So starting from the basis that the follow-up control knows at all times the position of its two tracking axes through the corresponding sensors referred, the basic solar tracking routine will consist of a loop that continuously calculates the position of the sun based on the time and transform these angular coordinates first of all in the angles of rotation in volume to the follower tracking axes under control that are necessary to guide the normal to the follower opening parallel to the solar vector, and to then these angles in the units in which the readings of the position sensors of the tracking axes, which depending on the type of sensors used will be continuous magnitudes or discreet If in any of the two tracking axes the difference between calculated and current position equals or exceeds a certain threshold the ephemeris calculation loop is interrupts, and the microcontroller starts to operate on the outputs digital that control the motor control unit in such a way that axis rotates until it exceeds the position calculated by a value equal to the aforementioned threshold, after which the calculation loop resumes ephemeris continuum waiting for you back to the position of the sun surpasses the current positions of any of the two axes When the follower has only one axis, the above has if corrected as long as the objective will be to point the normal to the opening parallel to the projection of the solar vector in the normal plane to the tracking axis. It is observed that it is a routine of solar tracking of discontinuous type, in the that every time on an axis the sun moves over a threshold the axis rotates to exceed the sun by the value of that same threshold, of such that this threshold is the maximum tracking error in each axis and since it alternates between the advance and the delay with Regarding the sun, the average error is zero. The discontinuous nature of this solar tracking routine is justified on the one hand at its low consumption, i.e. each engine only operates the time necessary to carry the axis of the orientation in which in that axis the monitoring begins solar in the morning until the one where it stops in the afternoon, and on the other hand it is the best way for possible slacks and Follower inertia does not induce oscillations in the control.

Systematic sources of tracking errors

The described routine of follow-up control operates under the assumption that the follower meets a certain arrangement of tracking axes. So in the case of a two-axis follower, in which one can distinguish between an axis primary, defined as the one whose support is linked to the ground by foundation or anchor, and a secondary axis, defined as the one whose support is linked to the primary axis, the control routine tracking requires for proper operation that the axis primary is installed on the ground with a certain orientation, or what is the same as a vector concrete, and that its position sensors locate their origin of angles for the turn following a certain orientation. In the common of cases the follow-up control routine also requires the perpendicularity of the primary and secondary axis, and that the sensors of position of the secondary axis locate their origin of angles for the turn following a certain orientation. Finally if once mounted the concentration system on the follower opening, we define the targeting vector as the one that remains static in a referential with one of its axes following the direction of the secondary axis and that rotates with it, and points in a direction such that when by the combined turns of the axes primary and secondary is coincident with the solar vector, produces the maximum photovoltaic power, the routine monitoring control It also has as a requirement for its correct operation that this aiming vector is normal to the secondary axis.

Tracking Error Model

The conditions described in the previous paragraph are referred to above as the need for coincidence between the references of the solar ephemeris and the of the solar tracker together with the concentration system it carries in its opening. To the extent that any of the requirements of the previous paragraph are not met this will cause tracking errors additional to those derived from the intrinsic precision of solar ephemeris as calculated by the microcontroller, and to the resolution of the position sensors installed on the axes of tracing.

Inaccuracies in the assembly and manufacturing of follower and its concentration system as well as in its subsequent installation and field mounting will produce compliance errors of the above requirements. The microcontroller has programmed a mathematical model of errors characterized by six parameters the mentioned errors, so that each of these parameters is associated with one of the aforementioned requirements or causes of mistake. Thus the mentioned parameters are:

?

Azimuth of the axis inclination primary (var): Two angular parameters, azimuth and angle zenith characterize the actual arrangement of the primary axis. (29) and (30)

?

Aerial angle of inclination of primary axis (the): Zenith angle of the primary axis. \ varphi and \ theta denote the incorrect alignment in the field of primary axis of monitoring. (31)

?

Primary axis offset (?): Angle difference between the origin of angles or reference of the primary axis and the South in the Northern Hemisphere (the North in the Southern hemisphere) when the rest of the parameters affecting to the primary axis. Collect errors of installation and manufacturing of follower, related to their incorrect alignment in the field, or the inaccuracies in the placement of the sensor that indicates the orientation of reference in the primary axis. (32)

?

No axis orthogonality (λ): Angle difference between the secondary and the normal axis to the primary axis, contained in the plane of the primary axes and secondary. It is a factory or field mounting error that characterizes the lack of perpendicularity between the axes of monitoring, and that in addition to introducing errors, results in a limitation of the orientation space within the reach of the follower. (33) and (34)

?

Axial inclination of the vector pointing (δ): Angle difference between the vector of pointing, and normal to the secondary axis contained in the plane of the aiming vector and the secondary axis. It is an error whose origin can be multiple, from the manufacture or assembly of the structure of the follower opening, up to that of the system concentration that carries well by misalignments between different parts of the collector / concentrator optics, of the receivers or between receivers and optics. (35) and (36)

?

Secondary axis offset (η): Angle difference between the reference of the secondary axis and the horizontal when the rest of the parameters are canceled. Pick up also errors of multiple origin, such as the imprecise placement of the sensor that indicates the references of the secondary axis, until the radial inclination of the pointing vector, this is the angle difference between the normal orientation to the orientation of reference of the secondary axis in the normal plane to the secondary axis and the projection of the point vector in the normal plane to the axis secondary, derived the same as in the case of? del imprecise alignment of the structure of the opening, the different parts of collector / concentrator optics, receivers or between receivers and optics (37)

It is a mathematical model in which of course the specific values of the six parameters are known for a particular follower and its concentration system, which characterize the various described errors that have been made, it will take the azimuth and elevation coordinates supplied by the solar ephemeris and transforms them into others in which there are already neutralized these errors so that the coordinate in azimuth can be converted to units handled in the readings of the primary axis sensors and the same with respect to the coordinate of elevation on the secondary axis.

Error model setting

The way to know the values of these parameters is for an adjustment of the model against a set of errors Tracking taken at different times. This setting can be carried out by least squares or any other estimating measure of maximum similarity that may be more robust to measures anomalous or defective. Follow-up errors are understood as differences between the coordinates obtained when by any manual or automatic procedure the follower is oriented along with its concentration system until the power output photovoltaic is maximum, and the coordinates calculated by the solar ephemeris at the same time that this occurs optimal targeting This would be obtained for each point and in a two-axis follower a couple of errors, one in azimuth and one in elevation. Thus, the model used is a nonlinear model it will be necessary to use iterative optimization algorithms to achieve the adjustment of the set of errors through the model of errors, for example in the case of using a minimum adjustment squares it is optimal to use the algorithm of Levenberg-Marquardt for said adjustment (Marquardt, D.W. "An algorithm for least-squares estimation of non-linear parameters "Journal of the Society of Industrial and Applied Mathematics, 11, 1963). Microcontroller You have programmed this adjustment procedure and once you are supplied the set of pointing errors is capable of automatically obtain the error model setting and six precise parameters that correspond to the follower and system of concentration that is controlling so. Once these are obtained parameters the loop of the essential follow-up routine before described is modified so that they will be computed continuously the solar ephemeris and the coordinates obtained are transformed through the model of errors with the mentioned parameters, being these corrected coordinates those that are transformed into units of the position sensors and are continuously compared with the position Current axes.

Acquisition of tracking errors to adjust the model

Together with the aforementioned error model and its adjustment procedure against a set of errors of monitoring, the microcontroller has also programmed the procedure for automatic collection of error set of follow up. In general terms this procedure is a stage with an approach in "closed loop" in which periodically the follower points to the sun, automatically, and you get the difference between the coordinates that are derived from the readings of the axis position sensors and those they get from the computation of the solar ephemeris in that same instant. This procedure has two possible variants according to which be the system used to determine when the follower with his Concentration system are correctly targeted. The first variant corresponds to the ideal procedure from the point of view of its accuracy which is the one that assumes that the follower and his system of concentration are correctly pointed when the power delivered by the photovoltaic generator is maximized. This variant however requires the connection of the generator to a load electric variable that polarizes it at its maximum power point, what is normally known as a follower stage of the point of maximum power (MPPT: Maximum Power Point Tracker), which is in essence a level conversion circuit in direct current DC-DC So, first of all a tracking of the sun according to which the follower sweeps the space of follow up with its two axes until the angular error between the solar vector and the targeting vector is less than or equal to the angular opening of the concentration system and sensors Current and voltage of the Tracking Control Equipment begin to Measure the power generation. At this point it is about find the maximum of a two-dimensional function - power delivered based on azimuth angular coordinates and elevation - for what will be done via maximization iterative of successive lines in this two-dimensional space and by which the follower will move at the speed allowed by their engines The fundamental difficulty of this procedure is that the stage that follows the point of maximum power must have its correction algorithm specially prepared to maintain continuously the optimal polarization of the photovoltaic generator in rapidly changing irradiance conditions, such as that occur during this maximization procedure of power. Thus, correction algorithms are usually used in conventional point tracking modules maximum power have longer response times than those need for the referred power maximization, the choice of This procedure would require integration into the control team of monitoring a stage following the point of maximum power specially prepared for speed tracking imposed by the motors of the follower shafts. In any case this precise tracking procedure of the follower would be repeated at different times and as many times as tracking errors We would like to set the error model set.

An alternative that to some extent can accelerating the procedure described in the first variant would require the integration of a pointing sensor, so that the first operation before proceeding to collect errors from Tracking would calibrate this against maximum power output. The aiming sensor would be installed at the follower opening ensuring that your exits always cancel and point correct in an address as close as possible, within economically reasonable, to the one in which the maximum occurs photovoltaic generator power output. Being so the pointing sensor may not have its own vector of aiming - the one for which the couple's exits from Photodiode segments associated with each axis are equalized - perfectly parallel to the solar tracker pointing vector and its concentration system, the correct solar tracker to maximize its output power by the procedure indicated above and at that time the readings of the pointing sensor channels, such that those will be the ones to reproduce whenever you want to get A precise point. Thus after this first aiming sensor calibration, the subsequent stage of collection of tracking errors that requires as seen successive correct follower prompts, will no longer require that these, in their last phase of approximation, in which the solar vector enters the angular opening of the concentration system, perform iterative power maximization, but as soon the solar vector is included within the angular opening of the pointing sensor, the tracking control becomes fed by the pointing sensor until it can reproduce the readings obtained in the calibration in its four channels, what That is always faster. However, keep in mind that this alternative does not eliminate if the follower assembles a photovoltaic generator, the need to integrate the module Maximum power point tracking of specific design above, as this will be necessary for the initial calibration of the pointing sensor.

The second variant, applicable is based on the approximate equivalence between the orientation in which the generator photovoltaic mounted on the tracker generates the maximum output of power with the generator with the variable polarization of a module maximum power point follower - as obtained in the first variant - and the orientation in which this same generator delivers maximum current when polarized to a voltage constant, provided that it is inferior at all times to the maximum power point voltage. In this way it is enough to provide to the Tracking Control Team with a current sensor (e.g. easy-to-install Hall effect toroidal sensor and that provides galvanic isolation), without the need for a sensor voltage or pointing sensor. On the other hand, the simplest will be polarize in short circuit, which only requires that the Tracking Control integrate capable switching devices occasionally disconnecting the generator output line photovoltaic of the load and short-circuit it, and above all avoid need for a maximum power point tracking module of a specific nature. In the maximization procedure of the current the procedure would be the same as the first variant, this is a first phase of tracking until the solar vector enters at the angular opening of the concentration system, the generator photovoltaic begins to generate constant voltage current, and the subsequent iterative maximization of the current function at constant tension depending on azimuth and elevation. In any case the advantages in terms of simplicity of implementation of this variant are at the cost of possible loss of precision not only because the orientations that maximize power and polarization current constant do not match exactly, but because it can also occur that the function of constant voltage current depending on of azimuth and elevation has the maximum little pronounced and therefore can be masked by noise of different types.

Regarding the automatic procedure of collection of tracking error set remains to be described the tracking procedure in one or two tracking axes, from an initial orientation of the follower that at the beginning of the process, in The first measure will be derived from the calculation of the ephemeris solar and its transformation to units of position sensors, until the solar vector enters inside the angular aperture of the concentration system, in the photovoltaic case, any whatever its polarization, or the pointing sensor. To increase the effectiveness of this tracking process comes into play the sensor of global irradiance in the opening plane, which integrated with the Tracking Control Equipment, may well be a cell properly encapsulated photovoltaic and with a resistance of precision ("shunt") in parallel, to be mounted parallel to the opening of the concentration system. Of this mode the easiest tracking procedure to program in the microcontroller, in the case of a two-axis follower, would be the one that from the initial point activates the two axes, so that two consecutive turns of the same axis are they produce in opposite directions and the one that occurs second extends to the first at an angle equal to the product \ sqrt {2} for the angular opening of the system that is using to determine the correct tracking of the follower, be it as said the concentration system, or the sensor pointing. If we represent the angular rotations of the follower axes in a plane with two Cartesian axes, the tracking procedure describes a rectangular spiral that starting from the initial search point, it opens by filling in the flat and in such a way that any straight line that passes through the origin of the spiral will have its consecutive cuts with this one at a distance always less than twice the angular opening of the system, so that it is impossible for even a spot of collimated light - that is with apparent diameter practically null - not detected by the system that is being used to determine the pointing Right. At the moment when the solar vector enters the said angular opening of the system used, the tracking is stops and starts the power maximization procedure, according to the variants that have already been described above. Once it has located for the first time the correct pointing of the sun - it it already has a first measure of pointing error for the set with which the error model will be adjusted - the points of start of the following search spirals that lead to new values of the pointing error do not have to be always the points generated by the ephemeris without any correction at the time of the start of the search, but these can corrected with an error estimate that can be obtained from of predictive filters that integrate the error measures of follow-up obtained up to that point, in this way it will be achieved gradually that the starting point of the spiral is closer to the correct point of aiming and therefore the time will be reduced Tracking The role of the global solar irradiance sensor in the opening plane will be to stop the tracking procedure when this is in progress, and in general inhibit the collection of tracking errors, provided that the global solar irradiance in this plane fall below a threshold, as this will indicate the concealment of the sun by clouds and therefore the impossibility of from that moment on the system that is being used to Determine the correct point to detect it. As soon as global irradiance exceeds the aforementioned threshold will remain enabled the error collection procedure again tracing. The global solar irradiance sensor can also be used to make a first approximation to the orientation of correct pointing, prior to the start of the spiral search and the subsequent maximization of generator power photovoltaic, which would proceed through consecutive maximization first by actuating a tracking axis and then the other, if there would be, of the measure of irradiance generated by this. Reached this maximum of the global irradiance sensor output, which does not has to match the orientation that generates the maximum of Photovoltaic generator power, because of its misalignments and the little pronounced of this maximum that prevents its determination accurately, the search would begin spiral.

Adjustment of temporary drifts

A source of error of particular importance to any solar tracking strategy based on the computation of ephemeris derive from the inaccuracy in the time supplied by the Internal clock of the Tracking Control Team. A clock controlled by a quartz oscillator will suffer significant drifts especially when it is installed outdoors as its Accuracy is primarily a function of temperature. So a conventional quartz oscillator can lead to errors in the range of ± 1 hour per year. It will therefore be necessary to synchronize periodically the system's internal clock with a time signal precise, and in this sense, there are several possibilities within reach e.g. time signal emitted by the GPS system, radio signals timetables, Internet synchronization protocols, etc. that also They are based on atomic clocks of the highest precision. Do not Despite the implementation of these types of synchronization in a Tracking control team demands the integration of resources additional physicals such as radio or GPS receivers or connectivity Internet, which will affect the final cost of the equipment. At Monitoring Control Team an approach is implemented alternative to those cited that takes advantage of the fact that it is available of very high precision solar ephemeris, so we can enter an additional parameter to adjust against the errors of collected follow-up, which represents the delay or advance accumulated by the internal clock of the Equipment. In this way the errors solar tracking are thus characterized by seven parameters, the six described above and the temporal drift parameter that add to the independent variable, time, of the equations that make up the solar ephemeris. In this way during the process of adjustment against the set of tracking errors, in addition to get the parameters that characterize installation errors, assembly, and manufacture of the follower, you will get the drift that has suffered the internal system clock so that this can be set again on time eliminating this.

Generalized Self-Calibration

We have described here all the routines and procedures that the Monitoring Control Team carries out to achieve maximum precision solar tracking and physical resources that said team gathers to carry them out. The oldest emphasis has been placed on the description of the procedures that performs to calibrate the internal solar ephemeris so automatic. However, the fact of that to adjust the error model parameters and the temporary drift parameter the ephemeris to be used do not have because they are necessarily those of the sun, and for the purposes of calibration procedure will be equally valid those of any Celestial body of equivalent precision. In this sense the alternative to the sun more interesting while viable would be the moon, for which there are also high-precision ephemeris whose programming and computing by the microcontroller of the Equipment Solar tracking is equally feasible. The apparent diameter of the moon and sun are practically identical, so the procedure for acquiring tracking errors would be applicable with the terrestrial satellite with hardly any modifications, except in relation to the sensors to be used to determine the precise pointing must have a much greater sensitivity, being so that the full moon has an irradiance six orders of magnitude lower than that of the sun. So for example in the case of the described variant that only integrates a current sensor, this, based on the open circuit efficiencies and voltages usual in a photovoltaic concentration system, it must be sensitive to currents of the order of microamps, although the precision and stability of high value resistors than this would not be a critical parameter because in maximization only attends to the relative variations of the current and not to the measurement accuracy. In the particular case that the acquisition errors are made with the moon, it will also be necessary to program in the microcontroller lunar phase equations depending on the day, because lunar ephemeris calculate the lunar vector based on the time and this always points to the center of the lunar disk, so and to avoid errors, the acquisition of errors should be done in the days when the phase is very close to the full moon. Topic apart will be the use of the irradiance sensor integrated in the procedure for acquiring follow-up errors based on Sun. The great advantage of being able to make the acquisition of errors tracking with the moon is that this process to be carried out by the sun requires a full day in which production Photovoltaic generator energy will be reduced (case of the first variant described above with maximization of the power of output) or completely interrupted (case of the second variant with short circuit current maximization), so beyond of the first calibration performed on the day of installation and commissioning follower point other calibrations would not be desirable. Without However, there are clearly variable sources of error with time, as is the drift of the internal clock of the Team of Follow-up Control, which would require periodic adjustments via calibration that could well be performed in periods of the lunar cycle. Another additional advantage of the use of the moon is that its irradiance is three orders of magnitude greater than that of brightest planets in the solar system and four times higher than that of the brightest stars, which makes it easy discriminate this star from the remaining nocturnal ones based on the power delivered by the photovoltaic generation system or equivalent.

Again with more accurate sensors too it will be possible to make the acquisition of errors with the planets or the brightest stars, for which there are also ephemeris of great precision and with special reason in the case of stars in which they only consist of transformations of their celestial fixed coordinates to the local observation point. They will also be practically spotlights which can result in greater precision in tracking error measurements, and they can also be alternatives in cases where the moon phase from the moon this distant from the full moon. His main drawback is the possibility that the procedure of error acquisition take some planets or stars for others, because in this case you can present several stars with irradiations of the same order of magnitude.

Brief description of the drawings

To complement the description and with in order to help a better understanding of the characteristics of the invention, a detailed description of a preferred embodiment, based on a set of diagrams and diagrams of flow that accompanies this descriptive report, being part member of the same and where merely for guidance and not limiting, the following has been represented:

Figure 1 shows in a block diagram the fundamental physical constituents of the Control Team of Solar Tracking, as well as the interrelationships between these

Figures 2 to 7 illustrate by diagrams of Flow the operation method of the Tracking Control Equipment Solar.

Figures 8 to 10 indicate the parameters angles that integrate the tracking error model.

Description of a preferred embodiment Constituents

A preferred embodiment of the Control Equipment Proposed Solar Tracking will have the following constituents fundamental physicists:

?

A microcontroller (1)

?

An internal clock based on a quartz oscillator (2)

?

An electronic unit of control of electric motors of direct or alternating current according to the case (3)

?

Optical encoders incrementals that inform the orientation in each moment of the different tracking axes under control, and circuits corresponding for decoding your signals and reading by microcontroller part (4)

?

Limit sensors electromechanical type that point to the microcontroller the ends of the tracking ranges of the different tracking axes under control, and prevent its overcoming (5)

?

Switching devices the power line of the photovoltaic generator that assembles the solar tracker to control, in order that the microcontroller have the option of occasionally disconnecting said line from the load and then short circuit it (6)

?

Switching devices the power line of the photovoltaic generator that assembles the solar tracker to control, in order that the microcontroller have the option to occasionally select which sensor current below described will measure the line current when this is shorted (7)

The aforementioned microcontroller will have a series of analog inputs, which equipped with the necessary external signal conditioning circuits will allow the Reading of:

?

A current sensor dimensioned based on maximum generator current photovoltaic to mount the solar tracker to control under source solar (8)

?

A very low current sensor dimensioned based on maximum generator current photovoltaic to mount the solar tracker to control under source mole (9)

?

A solar irradiance sensor global (10)

Operation method

In general terms the procedure of solar tracking will be carried out as follows:

one.

After Connection of the Follow-up Control Team to the follower to control and field installation of the whole set, proceed to perform a first self-calibration process that follows the following sequence:

to.

Conditioned to overcome in the global irradiance sensor of a preset threshold the microcontroller proceeds to short circuit the power line of the Photovoltaic generator that mounts the solar tracker (11).

b.

He microcontroller proceeds to switch as necessary so that the current sensor measure the line current, which will be the short circuit current of the photovoltaic generator (12).

C.

Conditioned at all times to the global threshold irradiance sensor exceeded preset, said irradiance is maximized consecutively in both tracking axes (13).

d.

Conditioned at all times to the global threshold irradiance sensor exceeded preset, it is traced by rectangular spirals, taking as starting point the guidance provided by the ephemeris solar, until the current sensor output exceeds a certain preset threshold (14).

       \ newpage
    

and.

Conditioned at all times to the global threshold irradiance sensor exceeded preset, linear maximizations are performed iteratively necessary so that the orientation of the two is located axes for which the maximum current is measured (15).

F.

Be record tracking errors on each axis (16).

g.

In as long as a number of follow-up error measures are not exceeded preset, after a certain time interval, calculated from such so that the number of measurements needed by the time interval equal to the time that on that day the sun remains within the range Following the follower, return to point a (17).

2.

He microcontroller acts on the switching devices of line to reconnect this to the load (18).

3.

With the set of tracking errors collected during the day and once at sunset the solar vector is outside the range of solar tracker tracking, the six adjustment is made Parameters of the tracking error model. Fit it performs the microcontroller by applying the iterative algorithm of Levenberg-Marquardt for which he has all the night, until the next morning the solar vector returns to enter within the follower tracking range (19).

Four.

With the photovoltaic generator again connected to the load starts the solar tracking procedure based on coordinates supplied by the solar ephemeris and its subsequent correction for the error model working with the product parameters of the adjustment made the night after the morning of collection of tracking errors Follow-up procedure that successive will be developed day after day as long as the coordinates supplied are kept within the tracking range of the Solar Tracker. At sunset when the solar vector leaves the tracking range, the microcontroller is always positioned at an orientation close to that in which at dawn you will find the solar vector for the first time within the range of follow-up, so that the next day the child is lost time to start tracking once it becomes possible (twenty).

5.

With in order to eliminate errors in the internal clock of the Equipment Solar Tracking will periodically adjust the drift parameter temporary against a set of tracking errors. To avoid that these periodic settings interrupt power generation by the photovoltaic generator, the corresponding session of collection of tracking errors will be developed by on nights of approximately full moon, therefore in a period not less than of lunar rotation, around 29.5 days. With this purpose the microcontroller has programmed the equations that compute the percentage of lunar disk illuminated according to the day, and the self-calibration procedure begins in the first night that a certain predetermined percentage is exceeded next to 100% and follow the following sequence (21):

to.

He microcontroller proceeds to short circuit the power line of the Photovoltaic generator that mounts the solar tracker (22).

b.

He microcontroller proceeds to switch as necessary so that the Very low current sensor measure the line current, which will be The short-circuit current of the photovoltaic generator (2. 3).

C.

Be track by rectangular spirals, taking as a starting point the guidance provided by the solar ephemeris and its subsequent correction by the error model working with the parameters product of the self-calibration developed in 1, up to that the very low current sensor output exceeds a certain preset threshold and go to point d. If on the contrary the linear velocity of trace expansion drops below the maximum lunar displacement speed without the sensor very Low current exceeds the aforementioned threshold, the tracking stops and go to point f. (24).

d.

From iterative mode the necessary linear maximizations of such that the orientation of the two axes for which the maximum current is measured (25).

and.

Be record tracking errors on each axis (26).

F.

In as long as a predetermined number of traces started is not exceeded although not necessarily culminated with an error measure of tracking, after a certain time interval, calculated in such so that the number of traces required by the interval of time is equal to time that on that night the moon remains inside of the follower tracking range, return to point a. (27).

6.

If the amount of tracking error measures collected during that night does not exceed the minimum amount required to ensure a precise adjustment of the temporary drift parameter is develop error collection sequence described in point 5 on successive nights and as for the percentage of Illuminated lunar surface remains higher than the preset value. If a night comes when the percentage of lunar surface illuminated is below the value and quantity of measurements of tracking error is still less than the minimum amount preset night self-calibration is suspended, the measures taken and return to point 4. On the contrary in the time when the amount of tracking error measures collected exceed the minimum amount required to guarantee an adjustment the microcontroller will start by applying the iterative algorithm of Levenberg-Marquardt taking advantage of the periods of time that follow in which the solar vector is not within the tracking range of the follower. Once this adjustment has been made and the parameter of temporary drift the microcontroller will correct the clock time internal by adding this correction factor, and return to point 4 (28).

Claims (7)

1. A Solar Tracking Control Procedure for photovoltaic concentrators characterized by operating in accordance with a method comprising the preliminary computation of the local coordinates of the sun (azimuth & elevation) by means of solar ephemerides encoded in a microcontroller, and their subsequent conversion at rotation angles of the monitoring axes of the photovoltaic concentrator with respect to its reference positions by means of the equations of an error model, which are also encoded in the microcontroller, take into account the differences between the reference of said ephemeris and the of the solar tracker being controlled, differences that are due to errors with respect to the specifications in the installation, manufacture and assembly of both said solar tracker and the photovoltaic concentration system that supports and points to the sun. 2. A Solar Tracking Control Procedure for photovoltaic concentrators characterized by operating according to a method comprising the use of an error model according to claim 1 that characterizes the differences between the reference of the solar ephemeris and that of the solar tracker that Control the Solar Tracking Control Equipment, by means of six parameters. The values of the aforementioned six parameters that correspond to the solar tracker under control are adjusted internally in the microcontroller from a set of pointing errors to the sun or the moon. 3. A Solar Tracking Control Procedure for photovoltaic concentrators characterized by operating in accordance with a method comprising automatic collection of sun pointing errors for use according to claim 2. Said automatic error collection method locates the actual orientation. of the sun in terms of angular rotations of the follower axes, by means of search routines that develop in three stages: (i) the maximization of the short-circuit current of a global solar irradiance sensor incident at the aperture or plane of collection of the photovoltaic concentrator, in such a way that said current is maximized first by operating the motor of one axis in the direction in which it grows, and then this same operation is repeated on the other axis, (ii) the plot of search movements that describe a rectangular spiral when the rotations printed to the two ej are represented in Cartesian coordinates It is over time as a parameter, movements that continue in this way until the sun is detected by means of current and voltage sensors that measure these variables at 1 output of the photovoltaic concentrator, or equivalently the sun is detected by means of a sensor that has previously been calibrated with the maximum power output of said concentrator. (iii) the maximization of the power delivered by the photovoltaic concentrator, as measured with current and voltage sensors, or equivalently by pointing a pointing sensor that has been previously calibrated with the maximum power output of said hub. Once the sun is located, the orientations of the two tracking axes are stored in terms of their respective rotations
angular. 4. A Solar Tracking Control Procedure for photovoltaic concentrators characterized by operating according to a method comprising automatic collection of sun pointing errors for use according to claim 2, and operating according to claim 3, with the variant that the step (ii) of search by rectangular spirals is developed until it is detected when the current delivered by the constant voltage polarized photovoltaic concentrator is increased above a predetermined threshold, as measured with a current sensor. The step (iii) is then started, which in this variant aims to maximize the current delivered by the constant voltage polarized photovoltaic concentrator, as measured with a current sensor. Once the sun is located, the orientations of the two tracking axes are stored in terms of their respective angular rotations. 5. A Solar Tracking Control Procedure for photovoltaic concentrators characterized by operating in accordance with a method comprising automatic collection of moon pointing errors for use according to claim 2. Said automatic error collection method locates the orientation. real of the moon in terms of angular rotations of the follower axes, by means of search routines that are developed in two stages (i) the tracing of search movements describing a rectangular spiral according to claim 3, movements that continue from this mode until the moon is detected when the current delivered by the polarized photovoltaic concentrator at constant voltage is increased above a predetermined threshold, as measured with a very low current sensor. The step (ii) that seeks to maximize the current delivered by the polarized photovoltaic concentrator at constant voltage is then started, as measured by the very low current sensor. Once the moon is located, the orientations of the two tracking axes are stored in terms of their respective angular rotations. 6. A Solar Tracking Control Procedure for photovoltaic concentrators characterized by operating according to a method comprising the use of a temporary drift parameter in an error model according to claim 2, whose specific value for the concentrator under control can be adjusted , individually or in conjunction with the other parameters of the model, from the set of pointing errors acquired automatically according to claims 3, 4 6 5 and thus correct the delays or advances that may arise from an integrated internal clock in the Solar Tracking Control Team, depending on whose time the solar ephemeris are calculated.

         \ newpage
      

7. A Solar Tracking Control Equipment for photovoltaic concentrators characterized by comprising:

?

A microcontroller or microprocessor.

?

An internal clock

?

An electronic unit of control of electric motors of direct or alternating current according to the case.

?

Position sensors that feedback to the control the orientation achieved on each axis of tracing.

?

Switching devices the power line of the photovoltaic concentrator with which occasionally disconnect said line from the load and then short circuit it.

?

Switching devices the power line of the photovoltaic concentrator with which power select the current sensor that will measure the line current when it is shorted.

?

A current sensor dimensioned based on maximum concentrator current photovoltaic

?

A very low current sensor dimensioned based on maximum concentrator current photovoltaic to the irradiance of the full moon.

?

A tension sensor dimensioned based on maximum concentrator tension photovoltaic

?

An irradiance sensor global.

?

A pointing sensor solar.