CN103034278A

CN103034278A - Method for realizing simulation circuit based on double linear approximate value MPPT (Maximum Power Point Tracking) algorithm

Info

Publication number: CN103034278A
Application number: CN2012105293993A
Authority: CN
Inventors: 李支柱; 张晓彬; 王�锋; 夏勇
Original assignee: EABAR TECHNOLOGY (WEIHAI) Co Ltd
Current assignee: EABAR TECHNOLOGY (WEIHAI) Co Ltd
Priority date: 2012-12-11
Filing date: 2012-12-11
Publication date: 2013-04-10

Abstract

The invention discloses a method for realizing a simulation circuit based on a double linear approximate value MPPT (Maximum Power Point Tracking) algorithm. The method is centrally characterized in that the double linear approximate value algorithm is applied; a double linear approximate computation circuit consists of a photosensitive diode and a thermistor, the reference voltage of a maximum power point is computed and outputted according to real-time illumination and temperature, a steady error signal with reference voltage and photovoltaic array real-time voltage is outputted by an adder and a PI (proportional integral) controller, and a duty ratio of a Buck step-down circuit is changed by a PWM (pulse width modulation) voltage comparator, so as to realize the MPPT; and the method comprises five specific steps. The method has the advantage that compared with the conventional MPPT control technique, the principle and the control algorithm are easier, the cost is lower, the vibration on the maximum power point is little, the control precision is high, the response speed is high, and the simulation circuit can be easily embedded into photovoltaic systems with different scales.

Description

Mimic channel implementation method based on the MPPT algorithm of dual linear approximation

Technical field

The present invention relates to a kind of mimic channel implementation method, relate in particular to a kind of mimic channel implementation method based on dual linear approximation MPPT controller control algolithm, belong to the MPPT maximum power point tracking technical field of photovoltaic generating system.

Background technology

The full name of MPPT controller " MPPT maximum power point tracking " (Maximum Power PointTracking) controller for solar is the upgraded product of traditional solar charging/discharging controller.So-called MPPT maximum power point tracking namely refers to the generating voltage that controller can the detecting real-time solar panels, and follows the trail of ceiling voltage current value (VI), make system with the highest efficient to charge in batteries.The MPPT algorithm is the MPPT maximum power point tracking algorithm, is the algorithms most in use in the photovoltaic circuit.

Photovoltaic generating system is to utilize the photovoltaic effect that luminous energy is directly changed into the electricity generation system of electric energy, and the MPPT maximum power point tracking of photovoltaic battery array (MPPT) key component of a photovoltaic system normally.In solar photovoltaic generation system, the impact that the output characteristics of photovoltaic battery array is subject to illumination and environment temperature is very large, has obvious nonlinear characteristic.Therefore, in order to improve the conversion efficiency of photovoltaic battery array, just need to judge fast and accurately the output characteristics of photovoltaic battery array, find the maximum power point of photovoltaic battery array.Maximal power tracing technology (MPPT) is exactly a technology of following the tracks of photovoltaic battery array maximum power point under both fixed temperature and intensity of illumination.

Conventional MPPT scheme such as disturbance observation, conductance increment method etc. need to be by microcontroller devices such as DSP at present, obtain fast real-time voltage and current waveform by the sensor sample technology, by specific algorithm waveform is identified, size by PWM technology change dutycycle finally reaches the purpose of following the trail of maximum power point.Can realize the tracking of maximum power point by the MPPT control program of above-mentioned routine, and have faster tracking velocity and preferably adjusting function.But, though the realization of these technology in that all more complicated and cost compare are high on the hardware design or in algorithm control, can there be certain hysteresis in easy generation vibration when following the trail of maximum power point near maximum power point.

Summary of the invention

The object of the invention is to overcome the deficiency of above-mentioned technology, a kind of mimic channel implementation method of the MPPT algorithm based on dual linear approximation is provided, can overcome conventional MPPT control program complex structure and the high shortcoming of cost by this scheme, vibration is little at the maximum power point place, control accuracy is high, speed is fast, and this programme circuit has preferably economic benefit and is embedded into easily in the photovoltaic system of different scales.

The technical solution adopted in the present invention is: a kind of mimic channel implementation method of the MPPT algorithm based on dual linear approximation, its core characteristics are utilizations of dual linear approximation algorithm, the approximate value of dual linearity refers to that respectively photovoltaic system is under constant temperature, the linear approximation relation of maximum power point voltage and intensity of illumination and photovoltaic system are under constant light is shone, the linear approximation relation of maximum power point voltage and temperature, the maximum power point of photovoltaic system satisfies the system of this dual linear approximation relation just; The present invention has used photodiode and the dual linear approximation computing circuit of the common composition of thermistor, by real-time illumination and temperature computing Maximum Power Output point reference voltage, steady-state error signal by totalizer and pi regulator output reference voltage and photovoltaic array real-time voltage, use the PWM voltage comparator to change the dutycycle of Buck reduction voltage circuit, thereby realized the tracking of maximum power point;

Its specific implementation step is as follows:

(1), dual linear approximation analog operational circuit is according to the intensity of illumination of photodiode and thermistor Real-time Collection and the maximum power point reference voltage Vref of temperature signal computing output photovoltaic array, photovoltaic array Real-time Collection magnitude of voltage Vpv;

(2), by adder circuit the reference voltage Vref in (1) and array real-time voltage Vpv are realized additive operation V=Vref-Vpv;

(3), regulate output signal V in (2) by pi regulator, the error signal Vi of output stable state;

(4), the error signal Vi of (3) and the square-wave signal of 12kHz are passed through the PWM voltage comparator, the dutycycle of change square-wave signal;

(5), the Buck reduction voltage circuit is because the variation of square-wave signal dutycycle in (4), the conducting turn-off time of switching tube changes, make the voltage Vpv of photovoltaic array towards the direction adjustment that reduces error until the elimination error finally reaches stable maximum power output;

The present invention is based on respectively approximate linear principle of the maximum power point of photovoltaic array and intensity of illumination and environment temperature, adopt simple mimic channel to build, circuit has used photodiode and thermistor simulation to realize the doublet sexual intercourse of photovoltaic array, determine accurately the reference voltage at maximum power point place, the array voltage difference of reference voltage and Real-time Collection is calculated error signal through the regulation output stable state of pi regulator, dutycycle by PWM comparer change Buck circuit realizes the accurate tracking of maximum power point.Compare the control technology of conventional MPPT, it is simple many that principle and control algolithm are wanted, and cost is lower, and it is little to vibrate at the maximum power point place, and control accuracy is high, and fast response time is embedded in the photovoltaic system of different scales easily.

Description of drawings

Fig. 1 is constant temperature, the power-voltage curve of photovoltaic array under different illumination intensity.

Fig. 2 is under the constant illumination condition, the power-voltage curve of photovoltaic array under different temperatures.

Fig. 3 is structural principle circuit diagram of the present invention.

Fig. 4 is control flow chart of the present invention.

Embodiment

By shown in Figure 3, ingredient of the present invention mainly comprises: photovoltaic array 1, Buck reduction voltage circuit 2, dual linear approximation computing circuit 3, totalizer 4, pi regulator 5 and PWM voltage comparator 6.

Photovoltaic array 1 provides DC source for whole system, the dutycycle that changes Buck reduction voltage circuit 2 can be followed the trail of the maximum power point of photovoltaic system, dual linear approximation computing circuit 3 can accurately calculate the reference voltage at the maximum power point place of array under real-time lighting and the temperature conditions, realize the calculating of reference voltage and real-time voltage error by totalizer 4, pass through again the error of pi regulator 5 regulation output stable states, computing through PWM voltage comparator 6, change the dutycycle of Buck reduction voltage circuit 2, make system voltage to the state operation that reduces error, finally reach and be stabilized in maximum power point output.When intensity of illumination and temperature changed, dual linear approximation computing circuit 3 calculated rapidly new reference voltage, by the adjusting of subsequent conditioning circuit, accurately reached rapidly new maximum power point stable state output.

Specifically introduce the implementing procedure of control program of the present invention below in conjunction with Fig. 4:

When system starts, execution in step 1, dual linear approximation computing circuit is according to real-time intensity of illumination and environment temperature computing Maximum Power Output point reference voltage Vref; Execution in step 2, Real-time Collection is to the real-time voltage Vpv of photovoltaic array; Execution in step 3 by totalizer, is calculated the difference V of Vref and Vpv, V=Vref-Vpv; Execution in step 4 is by the error signal Vi of the output of the difference V in the pi regulator regulating step 3 stable state; Execution in step 5, whether the error in judgement signal is 0; If be 0, then execution in step 6, and dutycycle does not change, and then execution in step 12, and voltage Vpv does not adjust, and then return step 2 and carry out; If be not 0, execution in step 7, judge difference whether be on the occasion of, if be on the occasion of, then execution in step 8, system duty cycle reduces, then execution in step 10, then voltage Vpv turns back to step 2 and carries out to the direction adjustment that increases; If difference is negative value, then execution in step 9, and the dutycycle of system increases, and then execution in step 11, and then voltage Vpv turns back to step 2 and carry out to the direction adjustment that reduces; Above-mentioned process circular flow, system will reach the peak power operation of stable state.

The below describes in detail to the embodiment of this circuit in actual motion:

At first, system opens, photodiode in the dual linear approximation computing circuit and thermistor are by sensing real-time intensity of illumination and temperature, adjust corresponding output, the reference value that computing by circuit obtains the voltage at maximum power point place is reference voltage Vref, by the collection to the magnitude of voltage of system's photovoltaic array, obtain the real-time voltage value Vpv of system's operation, through a totalizer, can calculate the difference V=Vref-Vpv of reference value and instantaneous value, the error Vi of pi regulator by amplification and the integral adjustment of this small error signal are exported stable state, error signal Vi and the pwm signal of stable state are exported through the PWM voltage comparator, corresponding variation can occur in the dutycycle of system, changes the turn-on and turn-off time of switching tube Q, thereby the voltage of system is moved to the direction of eliminating error.The state of error Vi is different, the variation of the dutycycle of system is just different, the direction that system voltage is eliminated error is just different, work as Vi=0, the reference value that is peak power voltage is identical with the array voltage instantaneous value, the dutycycle of system does not just need to change, and voltage can not change yet, and this moment, system namely exported at maximum power point; When Vi＞0, namely the reference value of peak power voltage is greater than the instantaneous value of photovoltaic array voltage, and the dutycycle of system will reduce, and the ON time of switching tube Q reduces, and system voltage increases until array voltage reaches reference value; When Vi＜0, i.e. the instantaneous value of the reference value of peak power voltage＜photovoltaic array voltage, the dutycycle of system will increase, and the ON time of switching tube increases, and system voltage reduces until array voltage reaches reference value.

The said process circulation is carried out, system will be issued to stable maximum power output in a certain illuminance and temperature conditions, and along with the rapid variation of intensity of illumination and temperature, dual linear approximation computing circuit can calculate again new peak power voltage reference value, and Circuit tuning reaches new stable maximum power output state rapidly.

Claims

1. mimic channel implementation method based on the MPPT algorithm of dual linear approximation, it is characterized in that: its core characteristics are utilizations of dual linear approximation algorithm, the approximate value of dual linearity refers to that respectively photovoltaic system is under constant temperature, the linear approximation relation of maximum power point voltage and intensity of illumination and photovoltaic system are under constant light is shone, the linear approximation relation of maximum power point voltage and temperature, the maximum power point of photovoltaic system satisfies the system of this dual linear approximation relation just; The present invention has used photodiode and the dual linear approximation computing circuit of the common composition of thermistor, by real-time illumination and temperature computing Maximum Power Output point reference voltage, steady-state error signal by totalizer and pi regulator output reference voltage and photovoltaic array real-time voltage, use the PWM voltage comparator to change the dutycycle of Buck reduction voltage circuit, thereby realized the tracking of maximum power point;

Its specific implementation step is as follows:

(5), the Buck reduction voltage circuit is because the variation of square-wave signal dutycycle in (4), the conducting turn-off time of switching tube changes, make the voltage Vpv of photovoltaic array towards the direction adjustment that reduces error until the elimination error finally reaches stable maximum power output.