CN102854911A - Photovoltaic battery maximum power tracking method - Google Patents

Abstract

The invention provides a photovoltaic battery maximum power tracking method. The method includes acquiring voltage and current of a photovoltaic battery panel via a voltage transformer and a Hall sensor, sending the acquired voltage and current to a DSP(digital signal processor) or a single-chip microcomputer through a voltage and current conditioning circuit, calculating power and derivative of current power to the voltage, generating a fuzzy control strategy by an MATLAB readfis function according to a membership function and a fuzzy rule list, saving the fuzzy control strategy to the DSP or the single-chip microcomputer, selecting input quantities E and EC and an output variable which is duty ratio increment delta d of an IGBT(insulated gate bipolar transistor), calculating a duty ratio increment delta d of an output variable DC/DC circuit according to the input quantities E and EC by searching a fuzzy control strategy list in the DSP or the single-chip microcomputer via a program on the basis of the input quantities E and EC, and generating PWM(pulse width modulation) signals to a switching tube by a DSP event manager according to the calculated value of the delta d. The photovoltaic battery maximum power tracking method overcome defects and problems existing in current conventional algorithms.

Description

A kind of maximum power tracking method of photovoltaic cell

Technical field

The present invention relates to the parallel network power generation technical field, relate in particular to a kind of maximum power tracking method of photovoltaic cell.

Background technology

Along with the continuous consumption of fossil energy, being on the rise of environmental pollution, greatly developing new forms of energy has become a kind of irresistible trend.Sun power more and more is subject to the attention of countries in the world as a kind of regenerative resource of cleaning.Under the energetically support of national governments, the average annual i.v. of the solar-energy photo-voltaic cell output in the whole world is 60%.China is having and is enriching very much solar energy resources, and theoretical reserves reach annual 17000 hundred million t standard coal equivalents, and the potentiality of solar energy resources development and use are boundless.In recent years, under the strong pulling in the national project such as " bright engineering " guide's project and " every township will have electricity " engineering and photovoltaic generation market, the world, especially the appearance of " planning of regenerative resource Long-and Medium-term Development " and " solar roof project ", " golden sun engineering ", the photovoltaic generation industry of China has obtained fast development." planning of regenerative resource Long-and Medium-term Development " clearly by 2010, the photovoltaic generation total volume will reach 300MW, and the year two thousand twenty reaches 1800MW.

The efficient of photovoltaic generating system is one of most important index of photovoltaic system, and it is the important channel of improving the efficient of photovoltaic system that photovoltaic system is carried out high-power point is followed the tracks of, and domestic and international many scholars have proposed a variety of MPPT maximum power point tracking technology.Commonly used have constant-voltage method, power disturbance observation, a conductance increment method.Wherein constant-voltage method can only use in the less scope of temperature inversion, is a kind of approximate MPPT maximum power point tracking technology, and tracking accuracy is not high.The disturbance observation can trace into maximum power point, but it is subjected to the impact of disturbance step-length larger, can trace into fast maximum power point when the disturbance step-length is larger, but larger in the vibration of maximum power point place; When the disturbance step-length hour, although less in the vibration of maximum power point place, tracking time is longer, tracking velocity is not high.

Fuzzy control is as a kind of advanced person's control technology, fuzzy control is the New Intelligent Control Technology in conjunction with traditional RBES, fuzzy set theory and control theory, compare with tradition control, fuzzy control does not rely on by the mathematical models of control object, especially non-linear object is shown preferably adaptability.For control object, select suitable input, output variable, formulate suitable membership function, can adaptive realization control purpose, saved PI parameter testing tuning process loaded down with trivial details in traditional control.Because the photovoltaic array output characteristics is non-linear, therefore domestic and international many scholars are applied to fuzzy control technology in the MPPT maximum power point tracking of photovoltaic system.

Retrieving fuzzy control has at Patents and the paper of the application of photovoltaic MPPT maximum power point tracking:

I. Ren Biying, Zhong Yanru, Sun Xiangdong. based on the maximum power point tracing method research [J] of fuzzy control. Power Electronic Technique, 2008,42 (11): 47-48.

II. Qiao Xinghong, Wu Bijun, Wang Kunlin. based on the photovoltaic generating system MPPT[J of fuzzy control]. regenerative resource, 2008,26 (5): 13-16.

III. Su Haibin, Wang Guangzheng, Wang Jidong. based on the maximum track algorithm [J] of the photovoltaic generating system of fuzzy logic dicyclo control. protecting electrical power system and control, 2010,38 (21): 215-218.

IV. Yuan Lulu, Su Haibin, Wu Donghui. based on the photovoltaic maximum power point Tracking Control Strategy research [J] of fuzzy theory. power electronics, 2009:18-21.

The when output power that the fuzzy MPPT method of above-mentioned document is all chosen photovoltaic array output power and output voltage is the input of fuzzy controller with the derivative of the ratio of output voltage, adopts symmetrical membership function and choose reasonable fuzzy rule to realize.Above-mentioned way can realize the MPPT maximum power point tracking function under certain condition, but it has ignored 2 problems:

1) the fuzzy PD controller is a kind of difference controller that has, and can not realize zero steady state error control under any condition in theory.

2) output characteristic curve of photovoltaic array is asymmetrical in the maximum power point both sides, and symmetrical membership function is not considered the photovoltaic device characteristic in the maximum power point both sides and the different interval differences in left side.

Fig. 2 has increased integral action and has consisted of fuzzy controller for becoming Structure Fuzzy-PID controller architecture figure on the basis of the fuzzy PD controller, this controller can be realized complete zero steady state error control, realizes high-precision tracking.Fig. 3 be photovoltaic array power to the output characteristic curve of voltage derivative and voltage, the C point is maximum power point, it is different that power that photovoltaic device is caused by same change in voltage in the maximum power point both sides changes.When choosing dP/dU and being the input quantity of fuzzy controller, the result of calculation that A, B are 2 is basic identical, but as can be seen from the figure the A point is away from MPP, and the B point is not inconsistent with result of calculation near MPP.This explanation: symmetrical membership function can not reflect that photovoltaic device is in the variation of MPP left side duty.

Fuzzy controller is comprised of obfuscation, knowledge base, fuzzy reasoning, ambiguity solution four parts.The effect of obfuscation is that the accurate amount that will input converts the obfuscation amount to.Knowledge base has comprised knowledge in the concrete application and the control target of requirement, and it normally is comprised of database and fuzzy rule base two parts.Fuzzy reasoning is based on that implication relation in the fuzzy logic and inference rule carries out.Ambiguity solution is that the fuzzy controlled quentity controlled variable that obtains is transformed to the clear amount that is actually used in control.

Low for the tracking accuracy that exists in the conventional maximum power point tracing method, response speed is slow, bad adaptability and follow the tracks of the low and existing the fuzzy PD controller of efficient and be difficult to realize the problems such as high-precision tracking maximum power point.This patent is realized a kind of new maximum power tracking method, can solve some problems that exist in the existing algorithm.

Therefore, instantly need a urgent technical matters that solves to be exactly: how can propose a kind of effective measures, to solve problems of the prior art.

Summary of the invention

Technical matters to be solved by this invention provides a kind of maximum power tracking method of photovoltaic cell, solves the deficiency and the problem that exist in the present conventional algorithm, counts photovoltaic system applicable to different capacity.

The invention is characterized in that the maximal power tracing algorithm that adopts is the thought according to fuzzy control, adopt the fuzzy controller and the asymmetrical membership function that become structure, Effective Raise tracking accuracy, realize that fast and stable follows the tracks of the maximum power point of photovoltaic cell accurately.

In order to solve the problems of the technologies described above, the invention provides a kind of maximum power tracking method of photovoltaic cell, comprising:

Gather the photovoltaic battery panel voltage and current by voltage transformer (VT), Hall element, with the voltage and current that collects through superpotential, current regulating circuit, deliver in DSP or the single-chip microcomputer, in DSP or single-chip microcomputer, calculate power by P (k)=U (k) * I (k), and calculate current time power to the derivative of voltage, wherein power is to the derivative of voltage, and two moment power deviations are divided by two moment of front and back voltage deviation before and after can adopting Come approximate solution power to the derivative of voltage;

According to membership function and fuzzy reasoning table utilize MATLAB readfis function to generate the fuzzy control decision table and deposit DSP in or single-chip microcomputer in;

Select the input quantity of fuzzy controller $E=\frac{\mathrm{dP}\left(k\right)}{\mathrm{dU}\left(k\right)},$ $\mathrm{EC}=\frac{\mathrm{dP}}{\mathrm{dU}}\left(k\right)-\frac{\mathrm{dP}}{\mathrm{dU}}(k-1),$ Output variable is the dutycycle increment Delta d of IGBT, looks into dutycycle increment Delta d that fuzzy decision table calculate output variable DC/DC circuit by program according to input quantity E and EC in DSP or single-chip microcomputer;

By the Δ d value of calculating, utilize the DSP task manager to produce pwm signal and give switching tube.

Further, described method also comprises: according to the control system requirement, formulate membership function and the fuzzy reasoning table of input and output amount.

To sum up, the invention provides a kind of maximum power tracking method of photovoltaic cell, thought based on fuzzy control neural network control, adopted improved change Structure Fuzzy-PID controller with integrating function, input, output quantity have reasonably been selected, formulate membership function and the fuzzy rule of asymmetrical input, output quantity, controlled photovoltaic permutation stable output power at maximum power point by adaptive adjustment pid parameter.The present invention can adapt to fast the photovoltaic array working environment and change, and has improved speed and the lasting accuracy of MPPT maximum power point tracking, has reduced system oscillation, satisfies the requirement of system's maximal power tracing.

Description of drawings

Fig. 1 is under normal circumstances photovoltaic array power-voltage output characteristics curve synoptic diagram of the present invention;

Fig. 2 is that the present invention becomes Structure Fuzzy-PID controller architecture figure schematic diagram;

Fig. 3 is the output characteristic curve schematic diagram of photovoltaic array dP/dU of the present invention and U;

Fig. 4 is the membership function schematic diagram of the E of the fuzzy PD of the present invention;

Fig. 5 is the membership function schematic diagram of the EC of the fuzzy PD of the present invention;

Fig. 6 is the membership function schematic diagram of the Δ d of the fuzzy PD of the present invention;

Fig. 7 is the membership function schematic diagram of the E of the fuzzy P of the present invention;

Fig. 8 is the membership function schematic diagram of the Δ d of the fuzzy P of the present invention;

Fig. 9 is the fuzzy PD Rule Expression intention of the present invention;

Figure 10 is the fuzzy P Rule Expression intention of the present invention;

Figure 11 is the present invention and method of perturbation simulated effect schematic diagram relatively.

Embodiment

The present invention is further detailed explanation below in conjunction with the drawings and specific embodiments.

The invention is characterized in that the maximal power tracing algorithm that adopts is the thought according to fuzzy control, adopt the fuzzy controller and the asymmetrical membership function that become structure, Effective Raise tracking accuracy, realize that fast and stable follows the tracks of the maximum power point of photovoltaic cell accurately.

Technical scheme of the present invention is as follows:

The first step: gather the photovoltaic battery panel voltage and current by voltage transformer (VT), Hall element, with the voltage and current that collects through superpotential, current regulating circuit, deliver in DSP or the single-chip microcomputer, in DSP or single-chip microcomputer, calculate power by P (k)=U (k) * I (k), and calculate current time power to the derivative of voltage.Wherein power is to the derivative of voltage, and two moment power deviations are divided by two moment of front and back voltage deviation before and after can adopting Come approximate solution power to the derivative of voltage.

Second step: according to the membership function of Fig. 4 and Fig. 5 and fuzzy reasoning table utilize the MATLABreadfis function to generate the fuzzy control decision table and deposit DSP in or single-chip microcomputer in.

The 3rd step: the input quantity of selecting fuzzy controller $E=\frac{\mathrm{dP}\left(k\right)}{\mathrm{dU}\left(k\right)},$ $\mathrm{EC}=\frac{\mathrm{dP}}{\mathrm{dU}}\left(k\right)-\frac{\mathrm{dP}}{\mathrm{dU}}(k-1),$ Output variable is the dutycycle increment Delta d of IGBT.In DSP or single-chip microcomputer, look into dutycycle increment Delta d that fuzzy decision table calculate output variable DC/DC circuit by program according to input quantity E and EC.

The 4th step: by the Δ d value of calculating, utilize the DSP task manager to produce pwm signal and give switching tube.

Maximal power tracing algorithm of the present invention, adopt improved fuzzy controller with integrating function, by voltage, current sensor, voltage, current regulating circuit send photovoltaic battery panel electric current and voltage, realize the maximal power tracing algorithm in digital signal processor (DSP) or single-chip microcomputer, control PWM output waveform realizes power adjustments.Initialization system at first, then sample photovoltaic battery panel output voltage, electric current calculate current time photovoltaic array current time power to the derivative of voltage $E=\frac{\mathrm{dP}\left(k\right)}{\mathrm{dU}\left(k\right)},$ And power voltage derivative difference $\mathrm{EC}=\frac{\mathrm{dP}}{\mathrm{dU}}\left(k\right)-\frac{\mathrm{dP}}{\mathrm{dU}}(k-1),$ Calculate the dutycycle increment Delta d of IGBT according to fuzzy decision table, realized the MPPT maximum power point tracking of photovoltaic array.

In the photovoltaic generating system, the output power of photovoltaic cell, the pass of voltage and current are: P=U*I, under the normal operation, the power voltage curve of photovoltaic cell is single protruding peak shape (as shown in Figure 1), has a unique maximum power point.When photovoltaic system is operated in the maximum power point place, slope dP/dU=0; DP/dU during the maximum power point left side〉0, dP/dU＜0 during maximum power point the right.Therefore, the design control system, adopt the fuzzy controller control (as shown in Figure 2) that becomes structure, select the input E of fuzzy controller, EC is respectively the derivative of dP/dU and dP/dU, output variable is the dutycycle increment Delta d of IGBT, has formulated asymmetrical input, output membership function, and ambiguity solution adopts gravity model appoach.Realize the MPPT maximum power point tracking of photovoltaic system.

More specifically, its specific implementation process is as follows:

I. the photovoltaic battery panel voltage U (k) that sampling is obtained and electric current I (k) P (k) that multiplies each other to get calculates current time power to the derivative of voltage

Wherein power is to the derivative of voltage

Two moment power deviations are divided by two moment of front and back voltage deviation before and after can adopting

Come approximate solution power to the derivative of voltage.

$\frac{\mathrm{dP}\left(k\right)}{\mathrm{dU}\left(k\right)}=\frac{P\left(k\right)-P(k-1)}{U\left(k\right)-U(k-1)}---\left(1\right)$

II. select the input quantity of fuzzy controller $E=\frac{\mathrm{dP}\left(k\right)}{\mathrm{dU}\left(k\right)},$ $\mathrm{EC}=\frac{\mathrm{dP}}{\mathrm{dU}}\left(k\right)-\frac{\mathrm{dP}}{\mathrm{dU}}(k-1),$ Output variable is the dutycycle increment Delta d of IGBT.

III. according to the control system requirement, formulate membership function and the fuzzy reasoning table of input and output amount.

IV. obtain output quantity dutycycle increment Delta d according to the gravity model appoach ambiguity solution.

Further, because the photoelectric conversion rate of photovoltaic cell is lower, for effectively utilizing photovoltaic cell, improve the efficient of photovoltaic system.Need to carry out maximal power tracing to photovoltaic cell.Lot of domestic and international scholar has proposed a lot of maximum power point tracing methods.Commonly used have constant-voltage method, disturbance observation and a conductance increment method etc.The weakness such as but conventional track algorithm exists in the process of following the tracks of fast maximum power point, and precision is low, bad adaptability and tracking efficient are low, this patent adopts a kind of novel maximum power tracking method to follow the tracks of fast, accurately the maximum power point of photovoltaic cell.

This maximum power tracking method has adopted improved fuzzy controller with integrating function, selective light photovoltaic array output power to the derivative of voltage and power to the input as fuzzy controller of the derivative of the derivative of voltage, rational fuzzy rule, asymmetrical membership function has been adopted in input and output, the gravity model appoach ambiguity solution is adopted in output, selecting the change in duty cycle amount of IGBT is the fuzzy controller output variable, realizes the MPPT maximum power point tracking of photovoltaic system.

Emulation confirms that the method with respect to traditional MPPT maximum power point tracking algorithm, has improved precision, speed and the stability of MPPT maximum power point tracking.

Above maximum power tracking method to a kind of photovoltaic cell provided by the present invention is described in detail, used specific case herein principle of the present invention and embodiment are set forth, the explanation of above embodiment just is used for helping to understand method of the present invention and core concept thereof; Simultaneously, for one of ordinary skill in the art, according to thought of the present invention, all will change in specific embodiments and applications, in sum, this description should not be construed as limitation of the present invention.

Claims (2)

1. the maximum power tracking method of a photovoltaic cell is characterized in that, comprising:

Gather the photovoltaic battery panel voltage and current by voltage transformer (VT), Hall element, with the voltage and current that collects through superpotential, current regulating circuit, deliver in DSP or the single-chip microcomputer, in DSP or single-chip microcomputer, calculate power by P (k)=U (k) * I (k), and calculate current time power to the derivative of voltage, wherein power is to the derivative of voltage, and two moment power deviations are divided by two moment of front and back voltage deviation before and after can adopting

Come approximate solution power to the derivative of voltage;

According to membership function and fuzzy reasoning table utilize MATLAB readfis function to generate the fuzzy control decision table and deposit DSP in or single-chip microcomputer in;

Select the input quantity of fuzzy controller $E=\frac{\mathrm{dP}\left(k\right)}{\mathrm{dU}\left(k\right)},$ $\mathrm{EC}=\frac{\mathrm{dP}}{\mathrm{dU}}\left(k\right)-\frac{\mathrm{dP}}{\mathrm{dU}}(k-1),$ Output variable is the dutycycle increment Delta d of IGBT, looks into dutycycle increment Delta d that fuzzy decision table calculate output variable DC/DC circuit by program according to input quantity E and EC in DSP or single-chip microcomputer;

By the Δ d value of calculating, utilize the DSP task manager to produce pwm signal and give switching tube.

2. the maximum power tracking method of photovoltaic cell according to claim 1 is characterized in that, described method also comprises:

According to the control system requirement, formulate membership function and the fuzzy reasoning table of input and output amount.

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