JP2015102876A - Maximum power tracking control device and maximum power tracking control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a maximum power tracking control device capable of achieving high-accuracy extremum seeking while making parameter measurement and calculation simple.SOLUTION: A maximum power tracking control device 1 for exerting a tracking control over a variable u so as to make output power y maximum for a control target 2 of an evaluation function y=f (u), includes: an HPF section 11 removing a DC component from the output power, and outputting a first signal; a LPF section 12 extracting a low-pass component from a second signal obtained by multiplying the first signal by a first perturbation signal, and outputting a third signal; an integrating section 13 integrating the third signal, and outputting a fourth signal; and a perturbation-signal switching section 15 outputting a first perturbation signal at constant amplitude if a discrimination function h (ξ) set based only on the third signal is greater than a threshold h, and outputting a second perturbation signal having attenuated amplitude if the discrimination function h (ξ) is equal to or smaller than the threshold h, a signal obtained by adding the first or second perturbation signal to the fourth signal being input to the control target 2.

Description

  The present invention relates to a maximum power tracking control device and a maximum power tracking control method for operating a power generation device at a maximum output.

  In recent years, mega solar and residential solar panels have become widespread and solar power generation has been promoted. In the field of photovoltaic power generation, in order to operate output power that changes according to weather conditions at an optimum operating point, research on a control device that performs maximum power tracking (MPPT) is underway.

  As one of the MPPTs for operating a power generation device typified by solar power generation with maximum power, extreme value search control can be mentioned.

The extreme value search control is a method of searching for the maximum value y ^{* of the} evaluation function y = f (u) (u is a physical variable) representing the output power characteristic of the power generator and the optimum value u ^{* from} which the maximum value y ^* is obtained. one of. The power generation device is, for example, a solar cell, the output y is the output power P of the solar cell, and the physical variable u is the voltage V. That is, the output power of the solar cell varies depending on the voltage, and the evaluation function in this case is P = f (V).

A control device that executes extreme value search control includes a high-pass filter, a low-pass filter, an integration unit, and a perturbation signal addition unit (Non-Patent Document 1). The high pass filter removes the DC component of the output y, and the low pass filter extracts the low pass component of the signal obtained by multiplying the output y from which the DC component has been removed by the perturbation signal ε (t). The integration unit increases or decreases the physical variable u based on the result of integrating the low frequency components. Then, the control device inputs the signal (u + ε (t)) obtained by adding the perturbation signal ε (t) to the physical variable u adjusted by the integration unit to the evaluation function y = f (u), and outputs the output y. Move closer to the maximum output point while perturbing. In this way, the control device repeats high-pass filtering, perturbation signal multiplication, low-pass filtering, integration, and perturbation signal addition. That is, by adding a perturbation signal to the physical variable u, a change in the output y due to the perturbation signal is observed, and the physical variable u is increased or decreased in a direction in which the output y increases based on the change. As a result, a combination of the optimum value u ^* and the maximum value y ^* is obtained. Thereby, it is possible to always extract the optimum value u ^* and the maximum value y ^* even if the evaluation function y = f (u) changes without measuring the static characteristics of the power generation device in advance. .

Daisuke Ura and one other, “Maximum power tracking control considering partial shadow of photovoltaic power generation system”, 2013 IEEJ Electronics, Information and Systems Division Conference, September 2013, p. 1334-1339. Scott Moura, et al. , “Lyapunov-based switched extremum seeking for photovoltaic power maximization,” Control Engineering Practicing 21, p. 971-980, 2013.

In the above-described conventional extreme value search type control device, it is possible to extract the optimum value u ^* and the maximum value y ^* with respect to the change of the evaluation function y = f (u). A constant perturbation signal component is superimposed on the physical variable u. For this reason, the output y falls into an extreme periodic orbit near the maximum power point, and efficient operation cannot be expected.

  In view of this, Non-Patent Document 2 further proposes a control device capable of removing the ultimate periodic orbit by extreme value search control based on the Lyapunov function. The control device described in Non-Patent Document 2 defines a Lyapunov function F obtained by a calculation result using each parameter of a closed-loop system composed of a high-pass filter, a low-pass filter, and an integration unit. The perturbation signal ε (t) to be added to the physical variable u is switched in accordance with the Lyapunov function F.

  However, in the control device described in Non-Patent Document 2, when extracting the Lyapunov function F serving as an index for switching the perturbation signal ε (t), it is output from each of the high-pass filter, the low-pass filter, and the integration unit. Parameter to be measured. This complicates the configuration for measuring a plurality of parameters. Furthermore, it is necessary to obtain a Lyapunov function F using a plurality of measured parameters and performing complicated operations including coordinate transformation, quadratic approximation, linearization, and the like. In particular, the determination of the Lyapunov function F requires a predetermined function form such as y = f (u). However, since the evaluation function y = f (u) is unknown, the predetermined function form must be assumed. As a result, the Lyapunov function F includes uncertainty, and it is assumed that the accuracy of the extreme value search is lowered, which is not sufficient from the viewpoint of the accuracy of the extreme value search.

  Therefore, the present invention has been made in view of such problems, and provides a maximum power tracking control device and a maximum power tracking control method capable of highly accurate extreme value search while simplifying parameter measurement and calculation. For the purpose.

  In order to achieve the above object, one aspect of the maximum power follow-up control device according to the present invention provides the physical variable such that the output power is maximized with respect to the power generation device in which the output power is expressed as a function of the physical variable. Is a maximum power follow-up control device that performs follow-up control, and outputs a first signal that is a signal from which a direct current component of the output power is removed, and multiplies the first signal by a first perturbation signal. And a third signal that is a signal obtained by extracting a low-frequency component of the second signal obtained by multiplying the first signal by the first perturbation signal and reflecting the slope of the function Among the first signal to the fourth signal, a low-pass part that outputs the signal, an integration part that integrates the third signal, and an integration part that outputs a fourth signal corresponding to the slope of the function, An inclination extraction signal that is the third signal or the fourth signal When the discriminant function set based on the threshold value is larger than a predetermined threshold, the first perturbation signal having a constant amplitude is output, and when the discriminant function is equal to or smaller than the predetermined threshold, the amplitude passes over time. And a perturbation signal switching unit that outputs a second perturbation signal that attenuates, and the first signal or the second perturbation signal output from the perturbation signal switching unit is added to the fourth signal. A signal is input to the power generator as the physical variable.

  As a result, the amplitude of the perturbation signal attenuates as the operating point approaches the maximum power point, so that stable and efficient maximum power follow-up operation can be performed without falling into the ultimate periodic orbit. For setting the discriminant function that serves as an index for switching the perturbation signal, it is only necessary to measure the slope extraction signal that is the output from the low-pass section or the integration section. Therefore, it is possible to perform an extreme value search with simplified parameter measurement and signal calculation.

  Further, the discriminant function is a function representing a time change of the inclination extraction signal.

  Thereby, the setting of the discriminant function can be realized only by monitoring the time change of the slope extraction signal without requiring complicated operations such as coordinate transformation, approximation and linearization based on a plurality of signals. Therefore, parameter measurement and signal calculation can be simplified.

  The discriminant function at time t is a value obtained by integrating the slope extraction signal from time (t−T) to time t, where T is the period of the first perturbation signal and the second perturbation signal. And a second integrated value that is a value obtained by time-integrating the slope extraction signal from time (t−nT) to time (t− (n−1) T) (n is an integer of 2 or more). Is the absolute value of the difference.

  Thereby, the setting of the discriminant function can be realized only by subtracting the integral values of the slope extraction signals at different times. Therefore, parameter measurement and signal calculation can be simplified.

  Further, a state quantity detection unit that detects a state quantity of the power generation device that changes the function, and an evaluation function that is a control target according to the state quantity acquired from the state quantity detection unit, An evaluation function replacement unit that replaces the function with a pseudo evaluation function corresponding to the state quantity.

  As a result, even if the power generator has a multimodal function, the function is replaced with a pseudo-evaluation function corresponding to the state quantity of the power generator, and the extreme value search is performed. It is possible to avoid convergence to the maximum point.

  In addition, the evaluation function replacement unit replaces the evaluation function to be controlled with the pseudo evaluation function from the function of the power generation device, and after a predetermined period has elapsed, the evaluation function to be controlled with the pseudo evaluation The function is returned to the function of the power generator.

  As a result, even when the power generation device has a multimodal function, the function is replaced with a pseudo-evaluation function and then returned to the above function again after a predetermined time has elapsed. Is possible.

  Further, the power generation device includes a solar battery panel in which a plurality of solar cells are connected in series, the function is a function having the physical variable as a voltage, and the state quantity detection unit includes the plurality of solar batteries. The solar radiation amount of each cell is measured as the state quantity, and the maximum power follow-up control device further includes the solar radiation amount of each of the plurality of solar cells and the maximum value of the function among the plurality of maximum values in the function. Is stored in advance, and the evaluation function replacement unit determines whether or not the function has a plurality of maximum values according to the amount of solar radiation acquired from the state quantity detection unit. And determining that the function has a plurality of local maximum values, by referring to the table data, the local maximum point that is the maximum value is obtained from the voltage region where the local maximum point that is not the maximum value exists. A function that monotonically increases toward the voltage region standing, set as the pseudo evaluation function.

  When the power generation device includes a plurality of solar cells, it is assumed that different solar cells have different solar radiation amounts due to partial shadows. In this case, the function of the power generation device may exhibit multimodality (having a plurality of maximum values) due to the difference in the amount of solar radiation between solar cells. On the other hand, according to the maximum power follow-up control device according to an aspect of the present invention, the evaluation function replacement unit, based on the table data and the solar radiation amount data for each solar battery cell, the evaluation function to be controlled, It can be replaced with an appropriate pseudo-evaluation function. Therefore, since the evaluation function to be controlled can be appropriately set corresponding to the change in weather, accurate maximum power follow-up control of the solar cell panel is possible.

  The present invention can be realized not only as a maximum power follow-up control device but also as a maximum power follow-up control method using a processing unit constituting the maximum power follow-up control device as a step or cause a computer to execute these steps. It can also be realized as a program or a recording medium such as a computer-readable CD-ROM in which the program is recorded.

  According to the maximum power tracking control device and the maximum power tracking control method of the present invention, parameter measurement and calculation for determining a perturbation signal input to a function representing output power characteristics can be simplified. Therefore, it is possible to search for extreme values with high accuracy while simplifying the device configuration.

Functional block diagram showing the configuration of a control system including a conventional extreme value search type control device A graph showing the response simulation results when a conventional extreme value search type control device searches for the maximum power Functional block diagram showing a configuration of a control system including a control device introduced with a Lyapunov function, described in Non-Patent Document 2. Functional block diagram showing a configuration of a control system including the maximum power tracking control device according to the first embodiment of the present invention. The figure explaining the function of the perturbation signal switch part which concerns on Embodiment 1 of this invention. The graph showing the response simulation result when the maximum power tracking control device according to the first embodiment of the present invention searches for the maximum power. Functional block diagram of control system including solar battery power generation device Graph showing voltage-current characteristics of solar panel Graph showing the voltage-power characteristics of solar cell panels Functional block diagram of the maximum power follow-up control system when a solar cell power generation device is a control target The graph showing the response simulation result when the maximum power tracking control device according to the embodiment searches for the maximum power Functional block diagram showing a configuration of a control system including a maximum power tracking control device according to Embodiment 2 of the present invention. The figure explaining the function of the perturbation signal switching part which concerns on Embodiment 2 of this invention. The graph showing the response simulation result when the maximum power tracking control device according to the second embodiment of the present invention searches for the maximum power. Functional block diagram showing a configuration of a control system including a maximum power tracking control device according to Embodiment 3 of the present invention. The figure explaining the structure and electrical property of the solar cell panel which concern on Embodiment 3. FIG. The figure which shows the electrical property of the solar cell panel when the state of the partial shadow is different The figure explaining the problem of extreme value search control when a partial shadow occurs Diagram explaining an example of setting a pseudo evaluation function Graph showing response characteristics when switching to pseudo-evaluation function Functional block diagram showing the configuration of a control system including a maximum power tracking control device having an evaluation function replacement unit and a perturbation signal switch unit based on a Lyapunov function

(Knowledge that became the basis of the present invention)
The present inventor has found that the following problems occur with respect to the conventional maximum power tracking control device described in the “Background Art” section.

FIG. 1 is a functional block diagram showing a configuration of a control system including a conventional extreme value search type control device. The control system shown in the figure is a system for maximizing the output of the control target 502, and includes a control target 502, a high-pass filter (HPF) unit 511, and a low-pass filter (LPF) unit 512. And an integration unit 513. The control target 502 is represented by an evaluation function y = f (u) that is a function of the physical variable u, and is, for example, a power generator such as a solar cell. In this case, y is output power and the variable u corresponds to voltage. In the control system described above, the extreme value search type control device including the HPF unit 511, the LPF unit 512, and the integration unit 513 is the optimum value for obtaining the maximum value y ^* of the output y and the maximum value y ^*. Search for the value u ^* .

The HPF unit 511 removes the DC component of the output y, and the LPF unit 512 reduces the signal obtained by multiplying the output y from which the DC component has been removed by the perturbation signal ε (t) (= a ₀ sin (ωt)). Extract band components. The integrating unit 513 increases or decreases the variable u based on the integrated value obtained by integrating the low frequency components. The conventional control device inputs a signal x (= u + ε (t)) obtained by adding the perturbation signal ε (t) to the variable u adjusted by the integration unit 513 to the evaluation function y = f (u). Then, the output y is brought close to the maximum output point while being perturbed. In this way, the conventional control device repeats high-pass filtering, perturbation signal multiplication, low-pass filtering, integration, and perturbation signal addition. That is, by adding the perturbation signal ε (t) to the variable u, a change in the output y due to the perturbation signal is observed, and the variable u is increased or decreased in a direction in which the output y increases based on the change. As a result, a combination of the optimum value u ^* and the maximum value y ^* is obtained. Thereby, it is possible to always extract the optimum value u ^* and the maximum value y ^* even if the evaluation function y = f (u) changes without measuring the static characteristics of the controlled object 502 in advance. Become.

  FIG. 2 is a graph showing a response simulation result when a conventional extreme value search type control device searches for maximum power. The upper part of FIG. 2 shows the time response characteristic of the signal x (= u + ε (t)), and the lower part shows the time response characteristic of the output y. With the control device, the signal x converges to 4 (au) while continuing a constant perturbation, and the output y converges to 10 (au). Here, even in the steady state after the elapse of 2 seconds, since the constant perturbation signal ε (t) is superimposed on the variable u, the output y vibrates near the maximum power point (y = 10). That is, since the output y falls into the limit periodic orbit, efficient operation cannot be expected.

  In order to eliminate the behavior of this extreme periodic orbit, in Non-Patent Document 2, the extreme periodic orbit is removed by extreme value search control based on the Lyapunov function.

  FIG. 3 is a functional block diagram showing the configuration of a control system including an extreme value search type control device introduced with a Lyapunov function described in Non-Patent Document 2. The control system shown in the figure further includes a perturbation signal switch unit 514 based on the Lyapunov function, in addition to the conventional control device shown in FIG. In the following, the control device shown in FIG. 3 will be described focusing on differences from the control device shown in FIG.

  In the extreme value search type control device shown in FIG. 3, the perturbation signal ε (t) that is switched according to the Lyapunov function F as shown in the following equation 1 with respect to the variable u output from the integration unit 513. Is added.

Here, a ₀ is the initial amplitude of the perturbation signal, ω is the angular frequency of the perturbation signal, Fth is a threshold, γ is an attenuation constant, and τ is the time when F = Fth. In the above equation 1, when F is larger than Fth, ε (t) becomes a sine wave having a constant amplitude a ₀ that does not depend on time, and when F becomes less than Fth, ε (t) It shows switching to a sine wave having an exponentially decaying amplitude. That is, when the output y approaches the maximum point, the amplitude of the perturbation signal ε (t) is attenuated so that the output y and the variable u do not fall into the ultimate periodic trajectory, thereby realizing a stable maximum point operation. Is possible.

  Here, the derivation process of the Lyapunov function F for switching the perturbation signal ε (t) will be described. First, the perturbation signal switch unit 514 based on the Lyapunov function measures the output (y−η) from the HPF unit 511, the output ξ from the LPF unit 512, and the output u from the integration unit 513. Here, η is a DC component of the output y. Next, the perturbation signal switch unit 514 converts the state equation of the closed loop system shown in FIG. 3 such as u (t), η (t), and ξ (t) to the equilibrium point (maximum power point) of the closed loop system. ) In a new coordinate system that translates to the origin. Next, the perturbation signal switch unit 514 approximates each state equation converted in the new coordinate system with a quadratic expression to obtain a nonlinear system. Next, the perturbation signal switch unit 514 linearizes the nonlinear state equation. Finally, the perturbation signal switch unit 514 derives the Lyapunov function F by substituting the linearized state equation into the Lyapunov equation.

  That is, in the extreme value search type control device shown in FIG. 3, the perturbation signal switch unit 514 (1) measures the parameters output from the HPF unit 511, the LPF unit 512, and the integration unit 513, and (2) The Lyapunov function F is derived by coordinate-transforming the state equation of the closed loop system, (3) quadratic approximation of the coordinate-transformed state equation, and (4) linearizing the quadratic approximated state equation.

  As described above, in the control device described in Non-Patent Document 2, the Lyapunov function F serving as an index for switching the perturbation signal ε (t) is derived from each unit as described in (1) to (4) above. Measurement of parameters that are outputs of the above and complicated operations such as coordinate transformation, approximation, and linearization are required. For this reason, the configuration for measuring a plurality of parameters is complicated, and it is assumed that the accuracy of the extreme value search is lowered depending on the controlled object due to the complicated calculation, which is sufficient from the viewpoint of the accuracy of the extreme value search. I can't say that.

  In order to solve such a problem, the maximum power tracking control device according to one aspect of the present invention is configured so that the output power is maximized with respect to the power generation device in which the output power is expressed as a function of a physical variable. A maximum power tracking control device for tracking control of a physical variable, a high-pass section that outputs a first signal that is a signal from which a direct current component of the output power is removed, and a first perturbation signal to the first signal And a signal obtained by extracting a low-frequency component of the second signal obtained by multiplying the first signal by the first perturbation signal and reflecting the slope of the function. A low-pass section that outputs three signals, a signal that is an integration of the third signal, and that outputs a fourth signal corresponding to the slope of the function, and the first signal to the fourth signal Among them, the third signal or the fourth signal is a tilt extraction. When the discriminant function set based only on the signal is larger than a predetermined threshold, the first perturbation signal having a constant amplitude is output, and when the discriminant function is equal to or smaller than the predetermined threshold, the amplitude is time A perturbation signal switching unit that outputs a second perturbation signal that attenuates with time, and adding the first perturbation signal or the second perturbation signal output from the perturbation signal switching unit to the fourth signal The signal is input to the power generator as the physical variable.

  According to this aspect, parameter measurement and calculation for determining the perturbation signal input to the function representing the output power characteristic of the power generation device can be simplified, so that an extreme value search with high accuracy can be performed while simplifying the device configuration. It becomes.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Each of the embodiments described below shows a preferred specific example of the present invention. The numerical values, the constituent elements, the arrangement positions of the constituent elements, the order of the connection forms, and the like shown in the following embodiments are merely examples, and are not intended to limit the present invention. The invention is specified by the claims. Therefore, among the constituent elements in the following embodiments, constituent elements that are not described in the independent claims indicating the highest concept of the present invention are not necessarily required to achieve the object of the present invention. It will be described as constituting a preferred form.

(Embodiment 1)
[overall structure]
FIG. 4 is a functional block diagram showing a configuration of a control system including the maximum power tracking control device according to Embodiment 1 of the present invention. The control system shown in the figure includes a maximum power tracking control device 1 and a control object 2. Hereinafter, each configuration of the control system will be described.

  The control target 2 is a power generation device having an evaluation function y = f (u). The y is the output of the power generator, and u is a physical variable. The power generation device is, for example, a solar battery. In this case, y is output power and u is voltage.

  The maximum power tracking control device 1 is a control device that performs tracking control of a physical variable so that the output power is maximized with respect to a power generation device in which the output power is expressed as a function of the physical variable. The maximum power tracking control device 1 includes an HPF (high-pass filter) unit 11, an LPF (low-pass filter) unit 12, an integration unit 13, a perturbation signal multiplication unit 14, and a perturbation signal switching unit 15. .

  A control system including the HPF unit 11, the LPF unit 12, the integration unit 13, the perturbation signal multiplication unit 14, and the controlled object 2 performs extreme value search control. Hereinafter, the extreme value search control will be described.

[Extreme search control]
First, as shown in Equation 2, by inputting x consisting of the physical variable u and the perturbation component ε (t) into the evaluation function y = f (u), the output y (t) is expressed by Equation 2 below. expressed.

  When the above expression 2 is expanded to the second-order term by Macrolin's expansion, the output y (t) becomes as shown in the following expression 3.

  Y (t) expressed by the above equation 3 passes through the HPF unit 11 which is a high-pass unit. As a result, the output from the HPF unit 11 becomes the first signal (y−η) from which the DC component η of the output y (t) has been removed, and is expressed by the following Expression 4.

Here, as shown in FIG. 4, the perturbation signal multiplier 14 generates a perturbation signal ε (t) ((= a ₀ sin (ωt)), and the perturbation signal is expressed by the equation (4 (y (t ) −η), the second signal that is an input signal of the LPF unit 12 is expressed by the following Expression 5.

  The input signal of the LPF unit 12 expressed by the above expression 5 passes through the LPF unit 12 which is a low-pass unit. As a result, the output ξ of the LPF unit 12 as the third signal is expressed by the following Expression 6.

  From the above equation 6, it can be seen that the output ξ of the LPF unit 12 is proportional to the slope (∂f / ∂u) of the evaluation function f (u). That is, the output ξ is a signal obtained by extracting the low frequency component of the input signal of the LPF unit 12 and is a signal reflecting the slope of the evaluation function y = f (u). Therefore, when the output ξ is positive, there is a maximum point of f (u) in the direction of increasing the physical variable u, and when the output ξ is negative, f (u) in the direction of decreasing the physical variable u. It can be seen that there is a maximum point. From this relationship, the fourth signal, which is a signal obtained by integrating the output ξ by the integrating unit 13 and corresponding to the gradient of the evaluation function y = f (u), is defined as the physical variable u to the evaluation function y = f (u). By inputting, the inclination of the evaluation function f (u) is associated with the increase / decrease of the physical variable u.

As described above, in the extreme value search control according to the present embodiment, the evaluation function y = f (u) acquires the slope of y with respect to u on the u-y plane from the perturbation signal, and the acquired y U is increased / decreased based on the slope of. Thereby, the extreme value search control according to the present embodiment does not measure the evaluation function y = f (u) in advance, and even if the evaluation function changes, the optimum value u ^* and the maximum value y ^* Can be extracted.

However, in the steady state where the optimum value u ^* and the maximum value y ^* are extracted, when the constant perturbation signal ε (t) is continuously superimposed on the variable u, the output y is near the maximum power point. Fall into the ultimate periodic orbit. On the other hand, the maximum power tracking control device 1 of the present invention further includes a perturbation signal switching unit 15. Hereinafter, the configuration of the perturbation signal switching unit 15 will be described.

[Perturbation signal switching]
The perturbation signal switching unit 15 obtains the output ξ of the LPF unit 12, compares the discriminant function h (ξ) with the obtained output ξ as a variable, and the discriminant threshold value h _th, and _sets the variable u based on the comparison result. The perturbation signal ε (t) to be superimposed is switched. Hereinafter, the function of the perturbation signal switching unit 15 will be described with reference to FIG.

  FIG. 5 is a diagram illustrating the function of the perturbation signal switching unit according to Embodiment 1 of the present invention. First, the graph on the left side of the figure is a graph showing the time response characteristic of the output ξ of the LPF unit 12 expressed by Expression 6. From this graph, the output ξ repeats vibration having a period T (= 2π / ω). Here, as the physical variable u changes with time, the waveform of each cycle of the output ξ also changes with time. In order to detect the waveform change of the output ξ, a discriminant function h (ξ) expressed by the following equation 7 is defined.

Discriminant function h (xi]) is defined by the above formula 7, a first integrated value is an integral value of output xi] time of one cycle at determined time _{t 0 (t 0 -T~t 0)} , the 1 It indicates the absolute value of the difference between the second integrated value is a value output ξ and integration time of one period (t ₀ -2T~t _{0 -T)} of the previous cycle. That is, the discriminant function h (ξ) is a function that represents a time change of the output ξ, and since the output ξ is a slope extraction signal that reflects the slope of the evaluation function f (u), the discriminant function h (ξ) is , Represents a change in the slope of the evaluation function f (u). For example, as the discriminant function h (ξ) is larger, the time change of the gradient of the evaluation function f (u) is larger, and as the discriminant function h (ξ) is smaller, the time change of the gradient of the evaluation function f (u) is smaller. The period during which the second integral value is acquired is preferably a period immediately before the period during which the first integral value is acquired, but is not limited thereto. Period the second integral value is obtained, the time _(t 0 -nt) from time _{(t 0 - (n-1} ) T) (n is an integer of 2 or more) may be any. Here, as is apparent from Equation 7, the discriminant function h (ξ) is a function set based on only the third signal among the first signal to the fourth signal.

The perturbation signal switching unit 15 switches and outputs the perturbation signal ε (t) as shown in the following Expression 8 by comparing the above-described discriminant function h (ξ) and the discrimination threshold h _th .

Here, a ₀ is the initial amplitude of the perturbation signal, ω is the period of the perturbation signal, h _th is the discrimination threshold, γ is the attenuation constant, and τ is the time at which h (ξ) = h _th It is. In the above equation 8, when the discriminant function h (ξ) is larger than the discriminant threshold h _th , the perturbation signal ε (t) becomes a sine wave having a constant amplitude a ₀ that does not depend on time, and the discriminant function h (ξ) is discriminated. When the threshold value _hth or less is reached, the perturbation signal ε (t) indicates that it switches to a sine wave having an amplitude that decays exponentially with time.

  A signal (u + ε (t)) obtained by adding the output (ε (t)) of the perturbation signal switching unit 15 to the fourth signal (u) output from the integration unit 13 is input to the controlled object 2 as a physical variable. The

FIG. 6 is a graph showing a response simulation result when the maximum power tracking control device according to the first embodiment of the present invention searches for the maximum power. The upper part of FIG. 6 shows the simulation result of the time response of the signal x (= u + ε (t)), and the lower part shows the simulation result of the time response of the output y. As shown in the upper part of FIG. 6, the signal x converges to 4 (au) while continuing a constant perturbation until 3 seconds, and after 3 to 4 seconds, an exponential function with time elapses. It converges to 4 (au) while having a perturbation in which the amplitude attenuates. On the other hand, as shown in the lower part of FIG. 6, the output y converges to 10 (au) while continuing a large perturbation until 3 seconds, and after 3 to 4 seconds, the index increases with time. It converges to 10 (au) while having a perturbation in which the amplitude attenuates functionally. Here, in 3 to 4 seconds, the perturbation signal switching unit 15 switches the perturbation signal ε (t) by comparing the discriminant function h (ξ) and the threshold value h _th . For this reason, the output y does not fall into the ultimate periodic trajectory, and a stable and efficient maximum power follow-up operation can be performed.

  Further, in the maximum power tracking control device 1 according to the present embodiment, as compared with the control device described in Non-Patent Document 2, the derivation of a discriminant function h (ξ) serving as an index for switching the perturbation signal ε (t). Therefore, it is not necessary to measure the output parameters from the HPF unit 11 and the integrating unit 13, and only the output ξ from the LPF unit 12 may be measured. Furthermore, it is only necessary to integrate the output ξ for a fixed period without requiring complicated operations such as coordinate transformation, approximation, and linearization. As a result, it is possible to perform an extreme value search with simplified parameter measurement and calculation.

  As described above, according to the maximum power tracking control device 1 according to the present embodiment, the amplitude of the perturbation signal is attenuated as the operating point approaches the maximum power point, so that it is stable and efficient without falling into the ultimate periodic orbit. The maximum power follow-up operation can be performed. In addition, it is not necessary to acquire a predetermined function format such as y = f (u) in advance for setting a discriminant function as an index for switching the perturbation signal, and only the output ξ from the LPF unit 12 is measured. That's fine. Therefore, it is possible to perform an extreme value search with simplified parameter measurement and signal calculation.

[Example]
Next, the example which controls the output electric power of a solar cell power generator using the maximum electric power tracking control apparatus 1 which concerns on this Embodiment is demonstrated.

  FIG. 7 is a functional block diagram of a control system including the solar battery power generation device. The control system shown in the figure includes a maximum power follow-up control device 1 and a solar cell power generation device 21 that is a control target.

  The solar battery power generation device 21 includes a solar battery panel in which a plurality of solar battery cells are arranged in an array, and a DC / DC converter (booster). The output terminal of the solar cell power generator 21 is connected to the system via a DC / AC converter connected to the subsequent stage. In the solar cell power generator 21, the following formula 9 is established.

Here, V _inv is a voltage across the capacitor disposed at the output end of the solar cell power generation device 21 and is an input voltage of the DC / AC converter. V is a DC voltage from the solar cell panel, and d is a duty ratio when PWM controlling the output voltage of the DC / DC converter. In this case, the maximum power tracking control device 1 acquires the output power P (I × V) by measuring the DC voltage V and the DC current I from the solar battery panel, and sets the evaluation function as P = f (d). Execute power tracking control. Specifically, the maximum power follow-up control device 1 outputs the optimum duty ratio d ^* for the DC / DC converter of the solar battery power generation device 21. As a result, the constant voltage V _inv is supplied to the _subsequent DC / AC converter.

  FIG. 8A is a graph showing voltage-current characteristics of the solar cell panel, and FIG. 8B is a graph showing voltage-power characteristics of the solar cell panel. Specifically, in FIG. 8A and FIG. 8B, characteristics when the amount of solar radiation is changed are represented, and a plurality of solar cells constituting the solar cell panel have the same performance and a plurality of solar cells. Is assumed that the amount of solar radiation is equal. 8A and 8B are results obtained by numerically solving a nonlinear equation representing the relationship between the current I and the voltage V of the solar cell panel using the Newton-Raphson method in the above assumption. As shown in FIG. 8A, the larger the amount of solar radiation, the larger the current I flows. As shown in FIG. 8B, the larger the amount of solar radiation, the larger the output power P. Further, as shown in FIG. 8B, it can be seen that the electric power with respect to the voltage exhibits a single peak (having one maximum point) at a certain amount of solar radiation. Further, in FIG. 8B, a point marked with a circle indicates that it is the maximum power point (MPP: Maximum Power Point). Hereinafter, a maximum power tracking control system in which the solar battery power generation device 21 having the above characteristics is incorporated will be described.

  FIG. 9 is a functional block diagram of the maximum power follow-up control system when the solar battery power generation device is a control target. The maximum power follow-up control system shown in the figure is composed of a maximum power follow-up control device 1 and a solar battery power generation device 21. In the following, the description will be focused on the point of difference in configuration from the control system shown in FIG.

The control target in the control system of the present embodiment is the solar battery power generation device 21, and the maximum power follow-up control device 1 sets the duty ratio d of the DC / DC converter as the physical variable u, and the maximum power P ^* and the P Follow-up control is performed with the optimum duty ratio d ^* when ^* is obtained. That is, in contrast to the evaluation function y = f (u) in the control system shown in FIG. 4, the evaluation function of the solar cell power generation device 21 in the control system of the present embodiment can be replaced with P = f (d). it can.

The perturbation signal switching unit 15 obtains the output ξ of the LPF unit 12, compares the discriminant function h (ξ) with the obtained output ξ as a variable, and the discriminant threshold value h _th, and _sets the variable d based on the comparison result. The perturbation signal ε (t) to be superimposed is switched.

FIG. 10 is a graph illustrating a response simulation result when the maximum power tracking control device according to the embodiment searches for the maximum power. The upper part of FIG. 10 shows the simulation result of the follow-up response of the output power P, and the lower part shows the simulation result of the time response of the discriminant function h (ξ). The graph on the left side of the upper stage of FIG. 10 indicates that the maximum power tracking control device 1 tracks the maximum power with respect to a rapid change (step change) in the amount of solar radiation. Moreover, it can be seen from the graph on the right side of the upper stage of FIG. 10 that the ultimate periodic trajectory decays exponentially as the maximum power point is approached. On the other hand, as shown in the lower graph of FIG. 10, the state where the discriminant function h (ξ) crosses the threshold value h _th is shown. It can be seen that the amplitude of the output power P shown in the upper right graph of FIG. 10 begins to attenuate in response to the time when the discriminant function h (ξ) becomes equal to or less than the threshold value h _th .

  As described above, according to the maximum power follow-up control device 1 of the present embodiment, the output power P of the solar battery power generation device 21 does not fall into the ultimate periodic orbit and can perform a stable and efficient maximum power follow-up operation. It becomes. Further, in order to derive the discriminant function h (ξ), only the output ξ from the LPF unit 12 needs to be measured, and further, complicated calculations such as coordinate transformation, approximation and linearization are not required, and the output ξ is constant. It is sufficient to integrate during the period. As a result, also in the present embodiment, it is possible to perform an extreme value search with simplified parameter measurement and calculation.

(Embodiment 2)
The maximum power tracking control device 1 according to Embodiment 1 sets a discriminant function h (ξ) based only on the output ξ of the LPF unit 12, and the magnitude relationship between the discriminant function h (ξ) and the discriminant threshold value _hth. Thus, the perturbation signal ε (t) to be added to the output u of the integrator 13 is switched. On the other hand, the maximum power tracking control device 20 according to the present embodiment sets a discriminant function h (u) based only on the output u of the integrating unit 13, and determines the discriminant function h (u) and the discriminant threshold h. 'The perturbation signal ε (t) to be added to the output u of the integrator 13 is switched according to the magnitude relationship with _th .

[overall structure]
FIG. 11 is a functional block diagram showing a configuration of a control system including the maximum power tracking control device according to Embodiment 2 of the present invention. The control system shown in the figure includes a maximum power tracking control device 20 and a control object 2. Hereinafter, the description of the configuration of the control system is omitted with respect to the same points as in the first embodiment, and different points are mainly described.

  The maximum power tracking control device 20 is a control device that performs tracking control of a physical variable so that the output power is maximized with respect to a power generation device whose output power is expressed as a function of the physical variable. The maximum power tracking control device 20 includes an HPF unit 11, an LPF unit 12, an integration unit 13, a perturbation signal multiplication unit 14, and a perturbation signal switching unit 25.

  A control system including the HPF unit 11, the LPF unit 12, the integration unit 13, the perturbation signal multiplication unit 14, and the controlled object 2 performs extreme value search control. Since the extreme value search control is the same as that of the first embodiment, the description thereof is omitted.

[Perturbation signal switching]
The perturbation signal switching unit 25 acquires the output u of the integration unit 13, compares the discriminant function h (u) with the acquired output u as a variable, and the discriminant threshold h ′ _th, and based on the comparison result, the variable u The perturbation signal ε (t) to be superimposed on is switched. Hereinafter, the function of the perturbation signal switching unit 25 will be described with reference to FIG.

  FIG. 12 is a diagram illustrating the function of the perturbation signal switching unit according to Embodiment 2 of the present invention. First, the graph on the left side of the figure is a graph showing the time response characteristics of the output u of the integrating unit 13. From this graph, the output u repeats vibration having a period T (= 2π / ω). Here, the waveform of each cycle of the output u changes with time. In order to detect the waveform change of the output u, a discriminant function h (ξ) represented by the following expression 10 is defined.

Discriminant function h (u) is defined by the formula 10, and the first integration value is a value obtained by integrating the output u time of one cycle at determined time _{t 0 (t 0 -T~t 0)} , the 1 It indicates the absolute value of the difference between the second integral value is an integral value of the output u time of one period (t ₀ -2T~t _{0 -T)} of the previous cycle. That is, the discriminant function h (u) is a function that represents a time change of the output u, and since the output u is a slope extraction signal corresponding to the slope of the evaluation function f (u), the discriminant function h (u) is , Represents a change in the slope of the evaluation function f (u). For example, as the discriminant function h (u) is larger, the time change of the gradient of the evaluation function f (u) is larger, and as the discriminant function h (u) is smaller, the time change of the gradient of the evaluation function f (u) is smaller. The period during which the second integral value is acquired is preferably a period immediately before the period during which the first integral value is acquired, but is not limited thereto. Period the second integral value is obtained, the time _(t 0 -nt) from time _{(t 0 - (n-1} ) T) (n is an integer of 2 or more) may be any. Here, as is apparent from Equation 10, the discriminant function h (u) is a function set based on only the fourth signal among the first signal to the fourth signal.

The perturbation signal switching unit 25 switches the perturbation signal ε (t) and outputs it by comparing the above-described discriminant function h (u) with the discriminant threshold value h ′ _th as shown in the following Expression 11.

Here, a ₀ is the initial amplitude of the perturbation signal, ω is the period of the perturbation signal, h ′ _th is the discrimination threshold, γ is the attenuation constant, and τ is h (u) = h ′ _th It is time to become. When the discriminant function h (u) is larger than the discriminant threshold h ′ _th , the perturbation signal ε (t) becomes a sine wave having a constant amplitude a ₀ that does not depend on time, and the discriminant function h (u) is When the threshold value is equal to or less than the determination threshold h ′ _th , the perturbation signal ε (t) indicates that it switches to a sine wave having an amplitude that decays exponentially with time.

  A signal (u + ε (t)) obtained by adding the output (ε (t)) of the perturbation signal switching unit 25 to the fourth signal (u) output from the integration unit 13 is input to the control target 2 as a physical variable. The

FIG. 13 is a graph showing a response simulation result when the maximum power tracking control apparatus according to the second embodiment of the present invention searches for the maximum power. The upper part of FIG. 13 shows the simulation result of the time response of the signal x (= u + ε (t)), and the lower part shows the simulation result of the time response of the output y. As shown in the upper part of FIG. 13, the signal x converges to 4 (au) while continuing a constant perturbation until 3 seconds, and after 3 to 4 seconds, an exponential function with time elapses. It converges to 4 (au) while having a perturbation in which the amplitude attenuates. On the other hand, as shown in the lower part of FIG. 13, the output y converges to 10 (au) while continuing a large perturbation until 3 seconds, and after 3 to 4 seconds, the output y increases as time passes. It converges to 10 (au) while having a perturbation in which the amplitude attenuates functionally. Here, in 3-4 seconds, perturbation signal switching unit 25, as compared to the discriminant function h (u) and a threshold value h _'th switches the perturbation signal ε (t). For this reason, the output y does not fall into the ultimate periodic trajectory, and a stable and efficient maximum power follow-up operation can be performed.

  In the maximum power tracking control device 20 according to the present embodiment, only the output u from the integrating unit 13 is measured in order to derive the discriminant function h (u) serving as an index for switching the perturbation signal ε (t). Good. Therefore, similarly to the maximum power tracking control device 1 according to the first embodiment, it is possible to perform an extreme value search with simplified parameter measurement and calculation.

  As described above, according to the maximum power tracking control device 20 according to the present embodiment, the amplitude of the perturbation signal is attenuated as the operating point approaches the maximum power point, so that it is stable and efficient without falling into the ultimate periodic orbit. The maximum power follow-up operation can be performed. In addition, it is not necessary to acquire a predetermined function form such as y = f (u) in advance for setting a discriminant function as an index for switching perturbation signals, and only the output u from the integrating unit 13 is measured. That's fine. Therefore, it is possible to perform an extreme value search with simplified parameter measurement and signal calculation.

(Embodiment 3)
Maximum power tracking control apparatuses 1 and 20 according to Embodiments 1 and 2 are configured to perform maximum power tracking control on the assumption that the evaluation function to be controlled has a single peak (there is only one maximum value of output y). Is to do. On the other hand, in the present embodiment, a description will be given of a maximum power tracking control device that can be applied when the evaluation function to be controlled has multimodality (there are a plurality of maximum values of output y).

  FIG. 14 is a functional block diagram showing a configuration of a control system including the maximum power tracking control device according to the third embodiment of the present invention. The control system shown in the figure includes a maximum power tracking control device 10 and a control object 2. Hereinafter, each configuration of the control system will be described.

[Evaluation function with multimodality]
The control target 2 is a power generation device having an evaluation function y = f (u). In this embodiment, the control target 2 is assumed to be a solar cell power generation device, and the evaluation function is P = f (d). . As in the example of the first embodiment, P is the output of the solar battery power generation device, and d is the duty ratio of the DC / DC converter. Here, the solar cell power generation device according to the present embodiment will be described focusing on differences from the solar cell power generation device according to the first embodiment. It is assumed that the solar battery panel of the solar battery power generator according to the present embodiment is composed of two solar battery cells connected in series.

FIG. 15 is a diagram illustrating the configuration and electrical characteristics of the solar cell panel according to Embodiment 3. As shown on the left side of the figure, when the amount of solar radiation incident on the two solar cells 1 and 2 connected in series is different (S ₁ ≠ S ₂ ), that is, when a partial shadow occurs, Electrical characteristics as shown are obtained. For example, when the solar battery cell 1 has a solar radiation amount of S ₁ = 1000 W / m ² and the solar battery cell 2 has a solar radiation amount of S ₂ = 400 W / m ² , as shown in the upper right side of FIG. The voltage-current characteristic of the solar cell panel is a step-like characteristic. Correspondingly, as shown in the lower right side of FIG. 15, the voltage-power characteristic of the solar cell panel is multimodal with respect to the voltage V (there are two maximum values of power P). . Here, in the voltage-power characteristic showing multimodality, which maximum value is the maximum power point is determined by the magnitude relationship between the solar radiation amounts of S ₁ and S ₂ . The relationship between the magnitude of the solar radiation amount of S ₁ and S ₂ and the electrical characteristics will be described with reference to FIG.

FIG. 16 is a diagram showing the electrical characteristics of the solar cell panel when the partial shadow states are different. In the figure, voltage-current characteristics and voltage-power characteristics are shown for three patterns in which the difference in the amount of solar radiation to the solar cells 1 and 2 is different. In either case, the voltage - although power characteristic has a _multimodal, | _S 1 -S 2 | when the _{= 200 (<S 1/2} ) , the maximum power point of the high-voltage side a maximum point _{P R, | S 1 -S 2} | when the _{= 800 (> S 1/2} ) , the maximum power point is the maximum point _{P L} of the low voltage side. _Moreover, | _S 1 -S 2 | when the _{= 500 (= S 1/2} ) , the maximum power point is two points of maximum points _{P R} maxima _{P L} and a high-voltage side of the low voltage side.

  Here, the problem of the extreme value search control when a partial shadow is generated on the solar cell panel will be described.

[Problems of extreme value search control]
FIG. 17 is a diagram for explaining the problem of extreme value search control when a partial shadow occurs. In FIG. 17, first, when there is no partial shadow and the solar cells 1 and 2 have the same amount of solar radiation (for example, S ₁ = S ₂ = 1000 W / m ² ), the voltage-power characteristic is as shown by a broken line. Has unimodality. In this case, when the extreme value search control is executed, the voltage V moves from the initial operating point to the maximum power point P _max1 while perturbing. In this state, caused partial shadow on the solar cell _panel, | _S 1 -S 2 | when a _{= 800 (> S 1/2} ), the voltage - power characteristics to the solid line as multimodal Change. In this case, the extremum search control, the operation point corresponding to the voltage V of the maximum power point P _max1, search point moves converges to an operating point P _R is the maximum point. However, the maximum power point P _L when the partial shadow is generated, rather than P _R, present on the lower voltage side. Consequently, when a partial shadow occurs, the operating point is converged to a local maximum point P _R, cases occur such can not be accurate MPPT to the maximum power point P _L.

  On the other hand, even if the controlled object has a multimodal evaluation function, the maximum power tracking control device 10 according to the present embodiment enables accurate maximum power tracking control. Hereinafter, the maximum power tracking control device 10 will be described.

[overall structure]
As shown in FIG. 14, the maximum power tracking control device 10 according to the present embodiment includes an HPF unit 11, an LPF unit 12, an integration unit 13, a perturbation signal multiplication unit 14, a perturbation signal switching unit 15, An evaluation function replacement unit 26, a solar radiation amount detection unit 27, and table data 28 are provided. The maximum power tracking control device 10 according to the present embodiment is provided with an evaluation function replacement unit 26, a solar radiation amount detection unit 27, and table data 28, compared to the maximum power tracking control device 1 according to the first embodiment. The point is different as a configuration. Hereinafter, the maximum power tracking control device 10 according to the present embodiment will be described focusing on differences from the maximum power tracking control device 1 according to the first embodiment.

[Main part configuration]
The solar radiation amount detection unit 27 is a control target state amount detection unit that measures the state amount of the control target 2 that changes the evaluation function, and specifically measures the solar radiation amount received by the solar cells 1 and 2. The solar radiation amount detection unit 27 outputs the measured solar radiation amounts of the solar cells 1 and 2 to the evaluation function replacement unit 26.

  The evaluation function replacement unit 26 replaces the evaluation function of the control target 2 with the pseudo evaluation function Pf according to the state quantity of the control target 2 acquired from the solar radiation amount detection unit 27. Here, the pseudo evaluation function Pf in the present embodiment is a pseudo evaluation function corresponding to the state quantity of the controlled object 2. Specifically, when it is determined that the evaluation function of the control target 2 has multimodality, the pseudo evaluation function Pf is a maximum from a maximum point that is not the maximum point among a plurality of maximum points that the evaluation function has. It is a function that increases monotonously toward the point. Hereinafter, the processing procedure of the evaluation function replacement unit 26 will be described.

  First, the maximum power follow-up control device 10 holds data indicating a discriminant represented by the following formula 12 as table data 28 in advance.

Here, P _L corresponds to the maximum point of the low-voltage side of the two maximum points constituting the multimodal, P _R corresponds to the maximum point of the high-voltage side. That is, the table data 28 is data indicating the relationship between the amount of solar radiation of each of the plurality of solar cells and the voltage region where the maximum value is obtained among the plurality of maximum values in the evaluation function.

Next, the evaluation function replacement unit 26 refers to the table data 28 based on the solar radiation amounts S ₁ and S ₂ of the solar cells 1 and 2 acquired from the solar radiation amount detection unit 27, and the maximum power point is on the low voltage side. Or on the high voltage side, or on both the low voltage side and the high voltage side. Note that the evaluation function replacing unit 26 does not acquire an accurate maximum operating point from the acquired solar radiation amounts S ₁ and S ₂ and the table data 28, but the maximum operation based on the solar radiation amounts S ₁ and S _2. This limits the physical variable area where the point exists.

  Next, the evaluation function replacement unit 26 determines whether or not to replace the current evaluation function with the pseudo evaluation function Pf based on the determination result. This determination will be described with reference to FIG.

FIG. 18 is a diagram illustrating an example of setting a pseudo evaluation function. The upper side of the figure, caused partial shadow on the solar cell _panel, | it is assumed that becomes _{= 800 (> S 1/2} ) | S 1 -S 2. In this case, the voltage-power characteristic changes to multimodality as shown by a solid line. At this time, the evaluation function replacement unit 26 refers to the table data 28 (Formula 12) based on the solar radiation amount S ₁ (= 1000 W / m ² ) and S ₂ (= 200 W / m ² ), and corresponds to CASE 1. to decide. That is, the evaluation function replacement unit 26 determines whether or not the evaluation function has a plurality of maximum values according to the solar radiation amount acquired from the solar radiation amount detection unit 27. In this example, the evaluation function replacement unit 26, the maximum power point is determined to be present in the low-voltage side, among the plurality of local maximum points with the current multimodal evaluation function, to the presence of P _R is not a maximum point the presence function monotonically increasing toward voltage region (the voltage V ₂ which belongs _to) that of the P _L from the voltage region (voltages V ₁ belonging _to) a pseudo evaluation function Pf, to replace the current evaluation function pseudo evaluation function Pf Select.

Here, the decision to replace the evaluation function of the controlled object with the pseudo-evaluation function is made when the evaluation function of the controlled object changes, the physical variable area where the maximum power point before the change exists, and the maximum after the change. This is a case where the physical variable area where the power point exists is different. In the example of FIG. 18, the maximum power point of the evaluation function having a single peak before the occurrence of the partial shadow exists on the high voltage side, but the maximum power point of the evaluation function having the multimodality after the generation of the partial shadow is present. P _L exists on the low voltage side. Therefore, the evaluation function replacement unit 26 selects to replace the current evaluation function with the pseudo evaluation function Pf.

In any of the three cases shown in FIG. 16, the evaluation function replacement unit 26 may replace the current evaluation function with the pseudo evaluation function Pf. For example, if the upper part of FIG _16, | _S 1 -S 2 | a _{= 200 (<S 1/2} ), the evaluation function substitution portion 26 selects CASE3 from the table data 28. In this case, the evaluation function replacement unit 26 determines that the maximum power point exists on the high voltage side, and the presence of P _L that is not the maximum point among the plurality of maximum points that the current multimodal evaluation function has. a function that monotonically increases from the voltage domain to the voltage region in the presence of P _R to the pseudo evaluation function Pf, choose to replace the current evaluation function pseudo evaluation function Pf. In this case, although it is not necessary to replace the pseudo evaluation function Pf, accurate maximum power follow-up control is executed.

  Next, the maximum power tracking control device 10 executes the extreme value search control for a predetermined period Tf, assuming that the evaluation function of the control target 2 is the pseudo evaluation function Pf. As a result, the operating point of the extreme value search control moves from the voltage region including the local maximum point that is not the maximum point to the voltage region including the maximum point.

  Next, after the extreme value search control using the pseudo evaluation function Pf described above is executed for a predetermined period Tf, the evaluation function replacement unit 26 uses the currently set pseudo evaluation function Pf as the evaluation function of the control target 2. Return to. Thereby, the operating point that has moved to the region including the maximum point follows the maximum power point with high accuracy based on the true evaluation function of the control object 2.

FIG. 19 is a graph showing response characteristics at the time of switching to the pseudo evaluation function. In the upper part of FIG. 19, the time response of the voltage V is shown. Prior to the occurrence of partial shadows (up to 5 seconds), the time converges with the maximum power point existing on the high voltage side of the unimodal evaluation function. Here, a partial shadow occurs at time 5 seconds, and the evaluation function changes from unimodal to multimodal. Evaluation function replacement unit 26 determines that corresponds to CASE1 in equation 12, to select a function that increases monotonically toward the existing voltage region of the P _R as a pseudo evaluation function Pf to a voltage region where the presence of P _L, multimodal Replace sex evaluation function.

  During the predetermined period Tf from time 5 seconds, the maximum power follow-up control device 10 executes extreme value search control for the pseudo evaluation function Pf. In this period Tf, the operating point moves from the high voltage side (1.5 V to 2 V) to the low voltage side (1 V or less) as shown on the lower right side of FIG. Then, after the elapse of the predetermined period Tf, the currently set pseudo evaluation function Pf is returned to the evaluation function of the control object 2. Thereby, as shown in the lower part of FIG. 19, the operating point moved to the low voltage side, which is the region including the maximum power point, is determined based on the true evaluation function of the controlled object 2 in the low voltage region. Is followed with high accuracy.

  As described above, according to the maximum power tracking control device 10 according to the present embodiment, even if the power generation device has a multimodal evaluation function, the evaluation function corresponds to the state quantity of the power generation device. Since the extreme value search is executed by replacing the pseudo evaluation function, it is possible to avoid the operating point from converging to an incorrect local maximum point.

  In addition, after the evaluation function is replaced with the pseudo evaluation function, the evaluation function is returned again after the elapse of the predetermined period Tf, so that accurate maximum power tracking control can be performed.

  As in the present embodiment, in particular, when the power generation device is composed of a plurality of solar cells, the evaluation function of the power generation device is multimodal due to the difference in the amount of solar radiation between the solar cells due to the occurrence of partial shadows. May show gender. On the other hand, according to the maximum power tracking control device 10, the evaluation function replacement unit 26 uses the table data 28 and the solar radiation amount data for each solar battery cell from the solar radiation amount detection unit 27 to make the appropriate pseudo evaluation function. Pf can be set. Therefore, since the evaluation function to be controlled can be appropriately set in response to changes in the weather or the like, accurate maximum power follow-up control of the solar cell panel is possible.

  In the present embodiment, for example, the pseudo evaluation function Pf shown in the lower part of FIG. 18 is set to a quadratic function of the voltage V as follows.

Here, alpha, beta, gamma, like monotonically increasing toward the existing voltage region of the P _R is not a maximum point (voltages V ₁ belongs _to) to the voltage region (the voltage V ₂ which belongs _to) in the presence of P _L Is a constant of a function. In this case, the lower limit of the length of the period Tf is determined by the following Expression 14, for example.

Here, k is a proportional gain of the integrating unit 13, a ₀ is an initial amplitude of the perturbation signal, and V _inv is an input voltage of the DC / AC converter. Note that the length of the period Tf is not limited to this. It is desirable that the length of the period Tf be set longer than the length defined by Equation 14 above. Further, the length of the period Tf is also adjusted according to the response performance of the controlled object.

(Other)
As described above, the maximum power tracking control device according to the present invention has been described based on the first and second embodiments, but the present invention is not limited to these embodiments. Unless it deviates from the meaning of the present invention, various modifications conceived by those skilled in the art have been made in the first and second embodiments, and forms constructed by combining components in different embodiments are also within the scope of the present invention. included.

  For example, the perturbation signal switching unit 15 of the maximum power tracking control device 10 according to the third embodiment may be replaced with the perturbation signal switching unit 25 of the maximum power tracking control device 20 according to the second embodiment.

  Further, the perturbation signal switching unit 15 may be realized in software by a program executed by a processor provided in a computer or the like, or may be realized in hardware by a dedicated electronic circuit such as a semiconductor integrated circuit. .

  In addition, this invention can be implement | achieved not only as the maximum power tracking control apparatus mentioned above but as a maximum power tracking control method which uses the process part which comprises the maximum power tracking control apparatus as a step. The maximum power follow-up control method of the present invention is a maximum power follow-up control method for causing a power generation device in which output power is represented as a function of a physical variable to follow up the physical variable so that the output power is maximized. A high-pass step for outputting a first signal that is a signal from which a direct current component of power is removed, a perturbation signal multiplication step for multiplying the first signal by a first perturbation signal, and a first perturbation signal for the first signal. Is a signal obtained by extracting a low-frequency component of the second signal multiplied by, and outputting a third signal that reflects the slope of the function, and a signal obtained by integrating the third signal, An integration step unit that outputs a fourth signal corresponding to the slope of the function, and a discriminant function that is set based on only the slope extraction signal that is the third signal or the fourth signal among the first to fourth signals is a predetermined function. If it is greater than the threshold, Outputs a first perturbation signal having a constant value, and when the discriminant function is equal to or less than a predetermined threshold, a perturbation signal switching step for outputting a second perturbation signal whose amplitude attenuates with time, and a perturbation to the fourth signal A perturbation signal addition step of inputting a signal obtained by adding the first perturbation signal or the second perturbation signal output in the signal switching step to the power generator as a physical variable.

  As a result, the amplitude of the perturbation signal attenuates as the operating point approaches the maximum power point, so that stable and efficient maximum power follow-up operation can be performed without falling into the ultimate periodic orbit. For setting the discriminant function that serves as an index for switching the perturbation signal, only the slope extraction signal that is the output from the low-pass section or the integration section may be measured. Therefore, it is possible to perform an extreme value search with simplified parameter measurement and signal calculation.

  Further, a state quantity detection step for detecting a state quantity of the power generation device that changes the function, and an evaluation function to be controlled according to the state quantity detected in the state quantity detection step, for a predetermined period, After the evaluation function replacement step of replacing the function of the power generation device with a pseudo evaluation function corresponding to the state quantity, and the evaluation function replacement step, the evaluation function to be controlled is returned from the pseudo evaluation function to the function of the power generation device. An evaluation function restoring step.

  As a result, even if the power generator has a multimodal function, the function is replaced with a pseudo-evaluation function corresponding to the state quantity of the power generator, and the extreme value search is performed. Therefore, it is possible to avoid convergence to the maximum point and to perform accurate maximum power tracking control.

  Further, the present invention may be a computer program that realizes the maximum power tracking control method by a computer, or may be a digital signal composed of the computer program.

  Furthermore, the present invention provides a non-transitory recording medium that can read the computer program or the digital signal, for example, a flexible disk, a hard disk, a CD-ROM, an MO, a DVD, a DVD-ROM, a DVD-RAM, a BD ( It may be recorded on a Blu-ray (registered trademark) Disc), a semiconductor memory or the like. The digital signal may be recorded on these non-temporary recording media.

  In the present invention, the computer program or the digital signal may be transmitted via an electric communication line, a wireless or wired communication line, a network represented by the Internet, a data broadcast, or the like.

  The present invention may be a computer system including a microprocessor and a memory, wherein the memory stores the computer program, and the microprocessor operates according to the computer program.

  Further, by recording the program or the digital signal on the non-temporary recording medium and transferring it, or transferring the program or the digital signal via the network or the like, It may be implemented by a computer system.

  Note that the maximum power tracking control device 10 according to the third embodiment includes an HPF unit 11, an LPF unit 12, an integration unit 13, a perturbation signal multiplication unit 14, a perturbation signal switching unit 15, and an evaluation function replacement unit 26. A solar radiation amount detection unit 27 and table data 28. However, from the viewpoint of a control device that accurately follows the maximum power of a control target having a multimodal evaluation function, a discriminant function set based only on the third signal among the first to fourth signals. Therefore, the perturbation signal switching unit 15 that switches the perturbation signal is not an essential component. For example, the control device in the above aspect may include a perturbation signal switch unit 514 based on the Lyapunov function shown in FIG. 3 instead of the perturbation signal switching unit 15. Hereinafter, the control apparatus will be described with reference to FIG.

  FIG. 20 is a functional block diagram showing a configuration of a control system including a maximum power tracking control device having an evaluation function replacement unit and a perturbation signal switch unit based on a Lyapunov function. As shown in the figure, the maximum power follow-up control apparatus includes an HPF unit 11, an LPF unit 12, an integration unit 13, a perturbation signal switch unit 514, an evaluation function replacement unit 26, and a solar radiation amount detection unit 27. And table data 28. Compared with the maximum power tracking control device 10 according to the third embodiment, this maximum power tracking control device does not have the perturbation signal multiplication unit 14 and the perturbation signal switching unit 15 but has a perturbation signal switch unit 514 added thereto. Is different in configuration. Hereinafter, description of the same points as those of the maximum power tracking control device 10 according to the third embodiment will be omitted, and only different points will be described.

  In the maximum power tracking control device, a perturbation signal ε (t) that is switched according to the Lyapunov function F is added to the variable u output from the integration unit 513 as shown in Expression 1. Further, the configuration for executing the replacement of the multimodal evaluation function with the pseudo evaluation function is the same as that of the maximum power tracking control device 10 according to the third embodiment.

  In the case of the above configuration, since complicated calculations such as coordinate transformation, approximation, and linearization are required for derivation of the Lyapunov function F, parameter measurement and calculation cannot be simplified. Since the evaluation function replacement unit 26 sets an appropriate pseudo evaluation function Pf, accurate maximum power follow-up control of the solar battery panel is possible.

  In the third embodiment, the maximum power follow-up control for the evaluation function having two maximum points is introduced, but the present invention is not limited to this. The maximum power tracking control device 10 of the present invention can be expanded even when there are three or more maximum points of the evaluation function.

  In the first to third embodiments, the solar cell power generation device is exemplified as the power generation device. However, the present invention is not limited to this, and the present invention can be applied to a wind power generation device, a fuel cell power generation device, and a distributed power source in which these are distributed.

  The present invention is useful as a maximum power follow-up control device, particularly for a photovoltaic power generation system that enables highly accurate extreme value search while simplifying parameter measurement and calculation.

1, 10, 20 Maximum power tracking control device 2, 502 Control object 11, 511 High-pass filter section (HPF section)
12, 512 Low-pass filter part (LPF part)
DESCRIPTION OF SYMBOLS 13, 513 Integration part 14 Perturbation signal multiplication part 15, 25 Perturbation signal switching part 21 Solar cell power generation device 26 Evaluation function replacement part 27 Solar radiation amount detection part 28 Table data 514 Perturbation signal switch part

Claims (8)

A maximum power follow-up control device that performs follow-up control on the physical variable such that the output power is maximized with respect to a power generation device whose output power is expressed as a function of a physical variable,
A high-pass section that outputs a first signal that is a signal obtained by removing a DC component of the output power;
A perturbation signal multiplier for multiplying the first signal by a first perturbation signal;
A low-pass section that outputs a third signal that is a signal obtained by extracting a low-frequency component of a second signal obtained by multiplying the first signal by the first perturbation signal and that reflects the slope of the function When,
An integration unit that outputs a fourth signal corresponding to the slope of the function, which is a signal obtained by integrating the third signal;
Of the first signal to the fourth signal, the amplitude is constant when the discriminant function set based only on the third signal or the slope extraction signal that is the fourth signal is larger than a predetermined threshold value. A perturbation signal switching unit that outputs a first perturbation signal, and outputs a second perturbation signal whose amplitude attenuates with time when the discriminant function is equal to or less than the predetermined threshold;
A maximum power follow-up control device, wherein a signal obtained by adding the first perturbation signal or the second perturbation signal output from the perturbation signal switching unit to the fourth signal is input to the power generation device as the physical variable. The maximum power follow-up control device according to claim 1, wherein the discriminant function is a function representing a time change of the slope extraction signal. The discriminant function at time t is a value obtained by integrating the slope extraction signal from time (t−T) to time t, where T is the period of the first perturbation signal and the second perturbation signal. A first integral value and a second integral value that is a value obtained by time-integrating the slope extraction signal from time (t−nT) to time (t− (n−1) T) (n is an integer of 2 or more). The maximum power tracking control device according to claim 1, wherein the maximum power tracking control device is an absolute value of a difference. further,
A state quantity detector that detects a state quantity of the power generation device that changes the function;
An evaluation function replacement unit that replaces an evaluation function to be controlled with a pseudo evaluation function corresponding to the state quantity from the function of the power generation device according to the state quantity acquired from the state quantity detection unit. The maximum electric power tracking control apparatus of any one of 1-3. The evaluation function replacement unit replaces the evaluation function to be controlled with the pseudo-evaluation function from the function of the power generation device, and after the elapse of a predetermined period, the evaluation function to be controlled with the pseudo-evaluation function The maximum power tracking control device according to claim 4, wherein the function is returned to the function of the power generation device. The power generation device includes a solar panel in which a plurality of solar cells are connected in series,
The function is a function using the physical variable as a voltage,
The state quantity detection unit measures the amount of solar radiation of each of the plurality of solar cells as the state quantity,
The maximum power tracking control device further includes:
Preliminarily storing table data indicating the relationship between the amount of solar radiation of each of the plurality of solar cells and the voltage region in which the maximum value of the function is obtained among the plurality of maximum values in the function,
The evaluation function replacement unit determines whether or not the function has a plurality of maximum values according to the amount of solar radiation acquired from the state quantity detection unit, and determines that the function has a plurality of maximum values By referring to the table data, a function that monotonously increases from the voltage region where the maximum point that is not the maximum value exists toward the voltage region where the maximum point that is the maximum value exists is set as the pseudo evaluation function. The maximum power follow-up control device according to claim 4 or 5. A maximum power tracking control method for performing tracking control of the physical variable such that the output power is maximized with respect to a power generation device in which output power is expressed as a function of the physical variable,
A high-pass step of outputting a first signal which is a signal from which a direct current component of the output power is removed;
A perturbation signal multiplication step of multiplying the first signal by a first perturbation signal;
A low-pass step of outputting a third signal, which is a signal obtained by extracting a low-frequency component of the second signal obtained by multiplying the first signal by the first perturbation signal and reflecting the slope of the function When,
An integration step unit for outputting a fourth signal corresponding to the slope of the function, which is a signal obtained by integrating the third signal;
Of the first signal to the fourth signal, the amplitude is constant when the discriminant function set based only on the third signal or the slope extraction signal that is the fourth signal is larger than a predetermined threshold value. A perturbation signal switching step for outputting a first perturbation signal and outputting a second perturbation signal whose amplitude is attenuated over time when the discriminant function is equal to or less than the predetermined threshold;
A perturbation signal addition step of inputting a signal obtained by adding the first perturbation signal or the second perturbation signal output in the perturbation signal switching step to the fourth signal as the physical variable to the power generator. Including maximum power tracking control method. further,
A state quantity detection step of detecting a state quantity of the power generation device that changes the function;
An evaluation function replacement step of replacing an evaluation function to be controlled with a pseudo evaluation function corresponding to the state quantity from the function of the power generation device for a predetermined period according to the state quantity detected in the state quantity detection step; ,
The maximum power follow-up control method according to claim 7, further comprising: an evaluation function restoration step that returns an evaluation function to be controlled from the pseudo evaluation function to the function of the power generator after the evaluation function replacement step.

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