CN105634043A - Photovoltaic intelligent charging control device - Google Patents

Abstract

The invention belongs to the technical field of new energy and specifically relates to a photovoltaic intelligent charging control device. The photovoltaic intelligent charging control device comprises a photovoltaic cell array and a power supply Ed. A diode D1, an inductor L1, a capacitor C2 and an inductor L2 are serially connected between the photovoltaic cell array and the power supply Ed in sequence. An anode of the diode D1 is connected with the photovoltaic cell array, a cathode of the diode D1 is connected with the inductor L1. The inductor L1 is connected with an anode of the capacitor C2. A cathode of the capacitor C2 is connected with the inductor L2, and the other end of the inductor L2 is connected with a cathode of the power supply Ed. A capacitor C1 is arranged between the cathode of the diode D1 and an anode of the power supply Ed. A switch tube Vr is connected between the anode of the capacitor C2 and the anode of the power supply Ed. A diode D2 is arranged between the cathode of the capacitor C2 and the anode of the power supply Ed. According to the invention, multiplication operation is not needed, and the photovoltaic intelligent charging control device has the advantages the algorithm is simple and the influences of environment factors are small, so that the cost of the system is further lowered, and the operation load of a single-chip microcomputer is reduced.

Description

Photovoltaic intelligent battery charge controller

Technical field

The invention belongs to technical field of new energies, be specifically related to a kind of photovoltaic intelligent battery charge controller.

Background technology

Saving the energy, protect environment to have become as the essential condition of human kind sustainable development, the attention of people is just turning to utilization and the exploitation of the renewable sources of energy, and wherein, solar electrical energy generation has become the focus of recent researches. Photovoltaic charging system generally comprises solaode, controller for solar and accumulator. Solar cell power generation climate condition affects, and output changes with ambient temperature, intensity of illumination change, has non-linear behavior. Under certain weather conditions, solaode has stream but can be operated in the feature of different output voltages, only when a certain output voltage values and optimum output voltage value, the output of solaode can be only achieved maximum, at this moment the operating point of solaode has just reached the peak of output-output voltage curve, i.e. maximum power point. At present, traditional photovoltaic charging method is not adopt DC/DC changer between photovoltaic cell and accumulator, directly utilize integrated circuit or special chip to be charged accumulator controlling, so can save DC/DC changer, improve main circuit efficiency, but, due to the running voltage of photovoltaic cell by case position on the charged electrical pressure point of accumulator, thus it cannot be guaranteed that photovoltaic cell is operated in maximum power point, being unfavorable for the raising of whole system efficiency.

Summary of the invention

The technique effect of the present invention can overcome drawbacks described above, a kind of photovoltaic intelligent battery charge controller is provided, adopt DC/DC changer as the interface circuit of photovoltaic cell and lead-acid accumulator, it is achieved the MPPT maximum power point tracking in a big way, be greatly improved the utilization rate of photovoltaic cell.

For achieving the above object, the present invention adopts the following technical scheme that it includes photovoltaic battery array, power supply E_d, photovoltaic battery array and power supply E_dBetween be sequentially connected in series diode D1, inductance L1, electric capacity C2, inductance L2, the positive pole of diode D1 connects photovoltaic battery array, and the negative pole of diode D1 connects the positive pole that inductance L1, inductance L1 connect electric capacity C2, the negative pole of electric capacity C2 connects the other end of inductance L2, inductance L2 and connects power supply E_dNegative pole; The negative pole of diode D1 and power supply E_dPositive pole between be provided with electric capacity C1, the positive pole of electric capacity C2 and power supply E_dPositive pole between be provided with switching tube Vr, the negative pole of electric capacity C2 and power supply E_dPositive pole between be provided with diode D2.

Select Cuk changer as the main circuit of charge controller, Cuk changer has boosting and buck functionality simultaneously, MPPT maximum power point tracking can be realized in a big way, and adopt Direct Current Control tracing, namely carry out MPPT maximum power point tracking by the charging current of detection charge controller. Export electric current according to changer and carry out MPPT maximum power point tracking as basis for estimation, then be possible not only to save two sensors, and without multiplying, have algorithm simple, by advantages such as such environmental effects are little, reduce system cost further, alleviate single-chip microcomputer computational burden.

Accompanying drawing explanation

Fig. 1 is Direct Current Control MPPT maximum power point tracking algorithm flow chart of the present invention;

Fig. 2 is the Cuk charge controller main circuit of the present invention;

Fig. 3 is the Cuk changer continuous operation mode equivalent circuit diagram of the present invention;

Fig. 4 MPPT maximum power point tracking charging control characteristic figure;

Fig. 5 MPPT maximum power point tracking charging control strategy flow chart.

Detailed description of the invention

The photovoltaic intelligent battery charge controller of the present invention includes photovoltaic battery array, power supply E_d, photovoltaic battery array and power supply E_dBetween be sequentially connected in series diode D1, inductance L1, electric capacity C2, inductance L2, the positive pole of diode D1 connects photovoltaic battery array, and the negative pole of diode D1 connects the positive pole that inductance L1, inductance L1 connect electric capacity C2, the negative pole of electric capacity C2 connects the other end of inductance L2, inductance L2 and connects power supply E_dNegative pole; The negative pole of diode D1 and power supply E_dPositive pole between be provided with electric capacity C1, the positive pole of electric capacity C2 and power supply E_dPositive pole between be provided with switching tube Vr, the negative pole of electric capacity C2 and power supply E_dPositive pole between be provided with diode D2.

Its operation principle is as follows:

First make two hypothesis:

1. the loss of changer own power is zero, and namely the output power from photovoltaic cells is equal to changer output:

2. load both end voltage (battery tension or line voltage) is invariable.

According to assuming to obtain formula (1), in formula, K is constant.

P_PV=P_out=U_LI_L

U_L=K (1)

Formula (2) can be obtained according to formula (1):

P_PV��I_L(2)

According to disturbance observation Fa Ke get:

D_k+1=D_k+|��D|sign(��D)sign(I_Lk-I_Lk-1)(3)

(3) formula is Direct Current Control MPPT maximum power point tracking basis for estimation, from formula (3): Direct Current Control MPPT maximum power point tracking only needs a current sensor, it is made directly perturbation direction according to load current size to judge, it is no longer necessary to photovoltaic cell output voltage and output electric current are detected and power calculation, simplify algorithm, reduce cost. Fig. 1 is Direct Current Control MPPT maximum power point tracking algorithm flow chart.

Cuk changer has boosting and buck functionality simultaneously, selects Cuk changer as the main circuit of charge controller, and its system topological is as shown in Figure 2. Cuk changer is in load current continuous print situation, and the steady-state process of its circuit has:

(T during the conducting of (l) switching tube_on=DT_S)

Switching tube V during this_rConducting, electric capacity C₂On voltage make diode D₂Reverse-biased and end, at this moment input current i_L1Make inductance L₁Energy storage; C₂Discharge current i_L2Make inductance L₂Energy storage, and supply electricity to load, as shown in Figure 3.

(2) switching tube V_r(T during cut-off_on=(1-D) T_S)

Switching tube V during this_rCut-off, diode D₂Positively biased and turn on, power supply E_dWith inductance L₁Release can electric current i_L1To C₂Charging, simultaneously inductance L₂Release can electric current i_L2To maintain load, as shown in Figure 3.

Therefore, V_rCut-off period C₂Charging, V_rConducting period C₂To load discharge, C₂Play the effect of energy transmission

When power supply steady-state operation, in a switch periods, by inductance L₁Volt-second equilibrium principle can obtain:

${\∫}_0^{{\mathrm{DT}}_S}{u}_S\mathrm{dt}={\∫}_0^{(1-D)T_S}(u_{c2}-u_S)\mathrm{dt}---\left(4\right)$

Due to C₂Value is relatively big and switching frequency is higher, therefore u_C2It is believed that invariable, then can be obtained by formula (4):

$u_{C2}=\frac{u_S}{1-D}---\left(5\right)$

In like manner, in a switch periods, by inductance L₂Volt-second equilibrium principle can obtain:

${\∫}_0^{{\mathrm{DT}}_S}(u_{c2}-u_O)u_S\mathrm{dt}={\∫}_0^{(1-D)T_S}{u}_O\mathrm{dt}---\left(6\right)$

Can be obtained by formula (6):

u_O=Du_C2(7)

Output voltage u is obtained by formula (5) and formula (7)₀With input voltage u_sBetween functional relationship be:

$u_O=u_S\frac{D}{1-D}---\left(8\right)$

From the foregoing, Cuk changer can realize MPPT maximum power point tracking in a big way, be conducive to the raising of system effectiveness.

The present invention adopts a kind of MPPT maximum power point tracking charge control method suitable in photovoltaic generating system, wherein MPPT maximum power point tracking adopts Direct Current Control tracing, namely MPPT maximum power point tracking is carried out by the charging current of detection charge controller, concrete charging method is as shown in Figure 4, C is the capacity (Ah) of accumulator, C₁��C₂��C₃������C_nFor accumulator charge rate. the charging incipient stage, arranging maximum charging current is C/10, as long as now charging current is less than maximum allowable charging current, carry out MPPT maximum power point tracking, photovoltaic cell Maximum Power Output charges a battery, if owing to intensity of illumination causes more greatly charging current more than maximum allowable charging current, then exit MPPT maximum power point tracking control, now charge a battery with maximum allowable charging current: once intensity of illumination weakens causes that charging current is less than maximum allowable charging current, now re-start MPPT maximum power point tracking control, make photovoltaic cell Maximum Power Output. along with the carrying out of charging process, once accumulator both end voltage rises to a certain setting value, progressively reduce maximum allowable charging current, curve C in figure₂��C₃����C_nShown in. Repeating charging process above with different charge rates, after several times circulate, maximum allowable charging current drops to C/100, and now accumulator is completely filled with.

Concrete control method is: sets a maximum allowable charging current to accumulator when just starting to charge up, such as makes C₁=C/10 (see thick line in Fig. 4), by constantly detecting battery current, and compares with this maximum allowed current, as long as charging current is not more than maximum allowable charging current. Meanwhile, constantly detect battery tension, once reach 2.4V/ cell, illustrating that accumulator comes into the state of overcharging, now should reduce the maximum charging current of setting, such as change C into₂=C/20, and repeat said process. Until when charging current reaches C/100, it was shown that accumulator has reached 100% full state. In traditional charge control method for photovoltaic power generation system, only adopting MPPT control method in the stage of filling soon, other charging stages do not adopt the method. This charge control method, owing to have employed electric current control, as long as therefore in any charging stage charging current under the premise of maximum allowable charging current, can adopt MPPT charge control method. Under the premise less than maximum allowable charging current, make photovoltaic array Maximum Power Output charge a battery, improve the utilization rate of photovoltaic array. For preventing accumulator from occurring section to charge after reaching 100% full state, setting the maximum charging current of accumulator as C/10, minimum charge current is C/100. Charging stage after this, as long as accumulator keeps a little charging current to compensate the loss caused of himself discharging. When detecting that electric discharge occurs, accumulator is again allowed to be charged with maximum current. The control flow of MPPT maximum power point tracking charge control algorithm is as shown in Figure 5, in figure, FLAGMPPT is MPPT maximum power point tracking flag bit, FLAGMPPT=1 represents that startup MPPT maximum power point tracking controls FLAGseMPPT=0 and represents that actual charge current is more than maximum allowable charging current, it is necessary to reducing actual charge current: N is accumulator series connection number (saving as standard with monomer 12V/); Overcharged voltage is set as 14.9V; Minimum voltage is set as 12.7V, represents under 25 DEG C of conditions, and accumulator capacity is battery open-circuit voltage value during 90% state: trickle current is set as 0.2A; Coefficient k selects standard to be that, in accumulator maximum allowable charging current reduction process from C/10 to C/100, in order to prevent overcharging, the change of battery state of charge is less than the 1% of normal accumulator capacity.

Claims (1)

1. a photovoltaic intelligent battery charge controller, it is characterised in that include photovoltaic battery array, power supply E_d, photovoltaic battery array and power supply E_dBetween be sequentially connected in series diode D1, inductance L1, electric capacity C2, inductance L2, the positive pole of diode D1 connects photovoltaic battery array, and the negative pole of diode D1 connects the positive pole that inductance L1, inductance L1 connect electric capacity C2, the negative pole of electric capacity C2 connects the other end of inductance L2, inductance L2 and connects power supply E_dNegative pole; The negative pole of diode D1 and power supply E_dPositive pole between be provided with electric capacity C1, the positive pole of electric capacity C2 and power supply E_dPositive pole between be provided with switching tube Vr, the negative pole of electric capacity C2 and power supply E_dPositive pole between be provided with diode D2.