CN103490717A - Photovoltaic module output P-V characteristic optimizing device and control method thereof - Google Patents

Abstract

The invention discloses a photovoltaic module output P-V characteristic optimizing device and a control method thereof. The photovoltaic module output P-V characteristic optimizing device is characterized by comprising a network formed by a battery pack, a discharging bridge arm, a capacitor bridge arm and a switch bridge arm. Based on the optimizing device, the switch bridge arm is controlled by a specific driving method to achieve good single power extreme point output effects. The photovoltaic module output P-V characteristic optimizing device is simple in circuit, low in cost, capable of effectively solving the problem that a general maximum power tracing algorithm is prone to being caught in a partial extreme point in the partial shadow condition, suitable for various photovoltaic power supply systems with serious partial shadow problems, widely applied to small photovoltaic systems of photovoltaic lighting, especially suitable for integrated converters of photovoltaic modules, good in compatibility and obvious in effect.

Description

A kind of photovoltaic module output P-V characteristic optimizing device and its control method

Technical field

The present invention relates to the photovoltaic power generation technology field, be specifically related to a kind of output device for the photovoltaic power supply system photovoltaic module and control method thereof.

Background technology

Along with the growing tension of the energy, the development new energy technology progressively becomes the focus of concern.Wherein safety, clean, and solar energy has become the important component part of new forms of energy reliably, in every field, starts to play a role.Therefore, solar energy generation technology is to solve global energy crisis and environmental problem, realizes one of Critical policies of sustainable development.

In photovoltaic generating system, because output power of photovoltaic module-voltage (P-V) characteristic presents non-linear, and there is maximum power point, and its maximum power point is along with factors vary such as illumination and ambient temperatures and change, in order to maximize the power output of system, must adopt suitable maximal power tracing point technology.The assurance system always operates in the photovoltaic module maximum power point, to obtain the maximum efficiency of photovoltaic generation.

Photovoltaic module is in the situation that illumination condition is constant, and its P-V characteristic curve only has an extreme point, i.e. maximal power tracing point, as shown in Figure 1, V-I and the P-V characteristic curve of photovoltaic module under different illumination conditions.Yet usually there are the shelters such as building or trees around photovoltaic generating system, its local shade formed on photovoltaic module not only causes output power of photovoltaic module to reduce, and a plurality of extreme points appear in its P-V characteristic curve, as shown in Figure 2, be the P-V characteristic curve of photovoltaic module under local shade condition.Because a plurality of extreme points have appearred in the P-V characteristic curve of photovoltaic module, disturbance observation and incremental conductance method commonly used easily are absorbed in Local Extremum, thereby can not guarantee that photovoltaic module operates in real global maximum power point, causes energy loss, inefficiency.

In order to improve the power output of the photovoltaic module with a plurality of power extreme points, at present existing corresponding strategies is devoted to improve and propose novel global maximum power point track algorithm aspect, there is a common problem in these methods: after a plurality of extreme points appear in photovoltaic module, these methods can only be passive the current global maximum power point of search photovoltaic module, now the power of global maximum power point is much smaller than the exportable power of current photovoltaic module, and its efficiency is still low; Simultaneously, the parameter designing of MPPT maximum power point tracking algorithm and realize more complicated.

Summary of the invention

Primary and foremost purpose of the present invention is to provide a kind of P-V of the output for photovoltaic module characteristic optimizing device and relevant control method, make still there is a maximum power extreme point under the photovoltaic module lighting effect severe at local shade etc., ensure the realization of global maximum power extreme point, thereby guaranteed the energy conversion efficiency of photovoltaic module under local shade condition.

Another object of the present invention is to provide a kind of P-V of the output for photovoltaic module characteristic optimizing device and relevant control method, under the prerequisite that guarantees output usefulness, can mate original disturbance observation and incremental conductance method equipment, can not make rear class equipment increase extra burden, there is versatility.

Technical scheme of the present invention is as follows:

Photovoltaic module output P-V characteristic optimizing device, it is characterized in that: it comprises:

Battery pack, comprise the first, second, third and the 4th photovoltaic battery elements that output voltage is identical, by the both positive and negative polarity forward, is in series separately, by series sequence, has A1, B1 and tri-battery node of F1;

The electric discharge brachium pontis, comprise the first, second, third and the 4th diode oppositely be in series by both positive and negative polarity; There are A2, B2 and tri-electric discharge nodes of F2 by series sequence;

The electric capacity brachium pontis, comprise by positive and negative electrodes in same to the first, second, third and the 4th electric capacity be in series; There are A3, B3 and tri-capacitive nodes of F3 by series sequence

The switch brachium pontis, comprise the first, second, third and the 4th switch be in series; There are A4, B4 and tri-switching nodes of C4 by series sequence;

Wherein, the two ends of described battery pack, electric discharge brachium pontis, electric capacity brachium pontis and switch brachium pontis are all in parallel in the same way according to the direction of inner member series connection separately; Between A2 and A3, with coil L3, be connected; There is coil L1 between A3 and A4; There is coil L2 between F3 and F4; This coil L1, L2 and L3 coupling, and Same Name of Ends lays respectively at A2, A3 and F3; B1, B2, B3 and B4 are communicated with; F1, F2 and F3 are communicated with.

The improvement of this programme structure has:

In preferred version, the electronic switch parts that described switch is electricity/photocontrol mode, comprise MOSFET, diode.Wherein MOSFET also can be used transistor, photoelectrical coupler etc. to substitute.

In preferred version, the described first and the 3rd switch is the P channel mosfet; The described second and the 4th switch is N-channel MOS FET; Described the first switch drains and is connected separately with the 4th switch with second switch, described the 3rd switch; Described second switch is connected with source electrode with the 3rd switch;

Wherein, each shared one, described the first switch and second switch, the 3rd switch and the 4th switch drive ground.

On this organization plan basis, the P-V optimisation strategy of employing is:

Wherein, the first, second, third and the 4th switch all with etc. the type of drive work of cycle, 50% duty ratio; Described the first switch and second switch, the 3rd switch and the 4th switch are complementary separately; The driving signal of described the first switch and the 3rd switch has a phase shifting angle φ;

One carrier wave V _tri, its waveform is:

$V_{\mathrm{tri}}=\left\{\begin{array}{c}\frac{\mathrm{\ωt}}{\mathrm{\π}},[2\mathrm{k\π}-\frac{\mathrm{\π}}{2},2\mathrm{k\π}+\frac{\mathrm{\π}}{2},)\\ \mathrm{\π}-\frac{\mathrm{\ωt}}{\mathrm{\π}},[2\mathrm{k\π}+\frac{\mathrm{\π}}{2},2\mathrm{k\π}+\frac{3\mathrm{\π}}{2},)\end{array}\right.$

One square wave V ' _ref, its waveform is:

${V^{\′}}_{\mathrm{ref}}=\left\{\begin{array}{c}0.5+{\mathrm{\ΔV}}_{\mathrm{ref}},[2\mathrm{k\π}-\frac{\mathrm{\π}}{2},2\mathrm{k\π}+\frac{\mathrm{\π}}{2},)\\ 0.5-\mathrm{\Δ}{V}_{\mathrm{ref}},[2\mathrm{k\π}+\frac{\mathrm{\π}}{2},2\mathrm{k\π}+\frac{3\mathrm{\π}}{2},)\end{array}\right.$

This carrier wave V _triwith square wave V ' _refsuperimposed, according to this Δ V _ref, determine phase shifting angle φ

φ=π·Δυ _ref。

Further, on the such scheme basis, described switch is MOSFET, and there is the dead band that prevents described switch bridge arm direct pass in the complementary waveform of described the first switch and second switch, the 3rd switch and the 4th switch.

The beneficial effect of this programme has:

1. simple circuit of the present invention, cost is low, can effectively solve under local shade condition the problem that the maximal power tracing algorithm easily is absorbed in Local Extremum of commonly using, be applicable to the various photovoltaic power supply systems that local shadow problem is comparatively serious, also can be widely used in the low profile photovoltaic systems such as photovoltaic illumination, be particularly suitable for the application of photovoltaic module integrated converter.

2. the structure of device is by above-mentioned brachium pontis, it the is possessed passage of power-balance.So this device can be realized the decile output of each photovoltaic battery elements voltage, is convenient to obtain single power extreme point.The switch brachium pontis is carried out to control operation, make each switch with appropriate mode conduction and cut-off, thereby can obtain the equal effect of each photovoltaic battery elements E1-E4 output voltage from this device.

3. the compatible maximum power point tracing methods commonly used such as original disturbance observation or incremental conductance method that use of this programme can guarantee that system operates in the maximal power tracing point.There is good compatibility.

4. the electronic switch parts that the switch S 1-S4 of the present embodiment is electricity/photocontrol mode, comprise MOSFET, diode.Use MOSFET to be conducive to integrate with other electronic control systems, realize miniaturization, integrated.

The accompanying drawing explanation

Below in conjunction with accompanying drawing embodiment, the invention will be further described:

Fig. 1 is the P-V characteristic curve schematic diagram under typical light photovoltaic assembly different illumination conditions;

The P-V characteristic curve schematic diagram that Fig. 2 is photovoltaic module under local shade condition;

The circuit diagram that Fig. 3 is one embodiment of the invention P-V characteristic optimizing device;

Fig. 4 is the equivalent circuit diagram of its mid point control balancing system embodiment illustrated in fig. 3;

Fig. 5 is that Fig. 4 realizes the primary and secondary voltage and current waveform that neutral point voltage balance is controlled;

The schematic diagram of realizing of angle of phase displacement φ is controlled in Fig. 6 phase shift;

Fig. 7 is the control block diagram of realizing angle of phase displacement φ;

Fig. 8 is the P-V characteristic curve schematic diagram of the photovoltaic module before and after output P-V characteristic optimizing device correction.

Embodiment

As shown in Figures 3 to 8, showed a preferred embodiment of the present invention.

At first Fig. 3 has showed the circuit diagram of this embodiment device part.This device comprises four major parts, is respectively battery pack, electric discharge brachium pontis, electric capacity brachium pontis and switch brachium pontis.

Battery pack, comprise the first, second, third and the 4th photovoltaic battery elements that output voltage is identical, is respectively E1, E2, E3 and E4, by the both positive and negative polarity forward, is in series separately, by series sequence (from top to bottom), has A1, B1 and tri-battery node of F1;

The electric discharge brachium pontis, comprise the first, second, third and the 4th diode oppositely be in series by both positive and negative polarity, is respectively D1, D2, D3 and D4; There are A2, B2 and tri-electric discharge nodes of F2 by series sequence (from top to bottom);

The electric capacity brachium pontis, comprise by positive and negative electrodes in same to the first, second, third and the 4th electric capacity be in series; Be respectively C1, C2, C3 and C4, by series sequence (from top to bottom), there are A3, B3 and tri-capacitive nodes of F3

The switch brachium pontis, comprise the first, second, third and the 4th switch be in series, and is respectively S1, S2, S3 and S4; There are A4, B4 and tri-switching nodes of C4 by series sequence (from top to bottom);

Wherein, the two ends of battery pack, electric discharge brachium pontis, electric capacity brachium pontis and switch brachium pontis are all in parallel in the same way according to the direction of inner member series connection separately, are connected in parallel on OUT1 and OUT2 two ends; Between A2 and A3, with coil L3, be connected; There is coil L1 between A3 and A4; There is coil L2 between F3 and F4; This coil L1, L2 and L3 coupling, and Same Name of Ends lays respectively at A2, A3 and F3; B1, B2, B3 and B4 are communicated with; F1, F2 and F3 are communicated with.

The structure of this device is by above-mentioned brachium pontis, it the is possessed passage of power-balance.So this device can be realized the decile output of each photovoltaic battery elements voltage, is convenient to obtain single power extreme point.S1-S4 is operated, make each switch with appropriate mode conduction and cut-off, thereby can be obtained the equal effect of each photovoltaic battery elements E1-E4 output voltage from this device.

Drive S1-S4 with square wave, wherein the duty ratio of S1-S4 be 50% and the cycle identical.S1 and S2, S3 and S4 drive the signal complementation

For capacitor C 1 and C2, work as U _c1u _c2, after the S1 conducting, voltage is added in coupling inductance armature winding L ₁upper, because L1 is identical with the L3 number of turn, induce identical voltage U on secondary winding L3 _c1, L3 charges to C2 by D2.Through some switch periods, when two capacitance voltages are identical, on L3, do not have electric current to flow through.Vice versa.

When there are not phase shift in S1 and S3, S1 drives phase place identical with S3, has guaranteed the voltage self-balancing between capacitor C 1 and C3.Now S2 drives phase place also identical with S4, has guaranteed the voltage self-balancing between capacitor C 2 and C4.

On the basis of above-mentioned self-balancing, for realize whole power-balance by this device, to guarantee single power extreme point, also need carrying out the processing of neutral point voltage balance between C1-C3 and C2-C4.

Neutral point voltage balance is realized by phase-shift control mode.The neutral balance realization mechanism is similar with bi-directional half bridge DC-DC converter, and its equivalent electric circuit as shown in Figure 4.The anode that this circuit mid point junction is equivalent to the elementary negative terminal of bi-directional DC-DC half-bridge converter and primary side connects together.L _s1with L _s2be respectively the elementary leakage inductance of coupling inductance and secondary leakage inductance.Fig. 5 is the elementary and secondary desired voltage current waveform of coupling inductance, and the relational expression of the power of the positive side of this figure bridge arm and minus side transmission is:

$P=\frac{U_{P_2-M}\&CenterDot;U_{M-{\mathrm{<figure-callout\; id="2"\; label="N"\; filenames="HDA0000380947010000011.png"\; state="\{\{state\}\}">N</figure-callout>}}_2}\&CenterDot;\mathrm{\&phi;}\&CenterDot;(\mathrm{\&pi;}-\mathrm{\&phi;})}{{\mathrm{\&omega;L}}_s\mathrm{\&pi;}}---\left(0.1\right)$

In formula, L _sbe the leakage inductance sum of the elementary leakage inductance of three winding coupled inductance and the second winding, U _p2-Mfor the voltage of node P2 to mid point M, that is first and second two capacitance voltages sum.U _m-N2for mid point M to node P ₂voltage, that is third and fourth two capacitance voltages sum.The phase shifting angle that φ is the positive side of brachium pontis and minus side.

Phase shift is controlled and is realized that principle as shown in Figure 6.υ _refbe a reference signal, υ _trifor thering is the carrier signal of unit amplitude value.The service time that δ is switch in one-period (any in S1-S4), υ _ref' by a square wave of stack on reference signal, formed.

One carrier wave V _tri, its waveform is:

$V_{\mathrm{tri}}=\left\{\begin{array}{c}\frac{\mathrm{\&omega;t}}{\mathrm{\&pi;}},[2\mathrm{k\&pi;}-\frac{\mathrm{\&pi;}}{2},2\mathrm{k\&pi;}+\frac{\mathrm{\&pi;}}{2},)\\ \mathrm{\&pi;}-\frac{\mathrm{\&omega;t}}{\mathrm{\&pi;}},[2\mathrm{k\&pi;}+\frac{\mathrm{\&pi;}}{2},2\mathrm{k\&pi;}+\frac{3\mathrm{\&pi;}}{2},)\end{array}\right.$

One square wave V ' _ref, its waveform is:

${V^{\&prime;}}_{\mathrm{ref}}=\left\{\begin{array}{c}0.5+{\mathrm{\&Delta;V}}_{\mathrm{ref}},[2\mathrm{k\&pi;}-\frac{\mathrm{\&pi;}}{2},2\mathrm{k\&pi;}+\frac{\mathrm{\&pi;}}{2},)\\ 0.5-\mathrm{\&Delta;}{V}_{\mathrm{ref}},[2\mathrm{k\&pi;}+\frac{\mathrm{\&pi;}}{2},2\mathrm{k\&pi;}+\frac{3\mathrm{\&pi;}}{2},)\end{array}\right.$

As carrier wave υ _trislope be on the occasion of the time, this square wave be also on the occasion of, as carrier wave υ _triduring for negative value, this square wave is also negative value.Therefore, υ _triwith υ _ref' crossing comparison point always than υ _triwith υ _refcrossing comparison point lag behind.Lagging phase angle and square wave Δ υ _refproportional:

φ=π·Δυ _ref (0.2)

As Δ υ _ref, can obtain a leading phase angle at<0 o'clock.

Angle of phase displacement φ control block diagram as shown in Figure 7, φ ^*for the lagging phase of brachium pontis minus side reference signal, υ _p2-Mfor node P ₂with respect to the voltage of mid point M, υ _m-N2for mid point M with respect to node N ₂voltage.Low pass filter is for filtering the ripple composition of two direct voltages that detect.

As Fig. 8, P-V characteristic curve schematic diagram for the photovoltaic module before and after output P-V characteristic optimizing device correction, can find out, virgin curve 1 has a plurality of extreme points, and curve 1 is the latter through output P-V characteristic optimizing, the P-V characteristic curve of photovoltaic module only has an extreme value, and the power output of maximum power point greatly increases before not optimizing.Visible, this result is used the maximum power point tracing methods commonly used such as original disturbance observation or incremental conductance method can guarantee that system operates in the maximal power tracing point.There is good compatibility.

The electronic switch parts that the switch S 1-S4 of the present embodiment is electricity/photocontrol mode, comprise MOSFET, diode.Use MOSFET to be conducive to integrate with other electronic control systems, realize miniaturization, integrated.

The first switch S 1 and the 3rd switch S 3 are the P channel mosfet; Second switch S2 and the 4th switch S 4 are N-channel MOS FET; The first switch S 1 drains and is connected separately with second switch S4, the 3rd switch S 3 and the 4th switch S 4; Second switch S2 is connected with source electrode with the 3rd switch S 3; Wherein, each shared one, described the first switch and second switch, the 3rd switch and the 4th switch drive ground.This form has been simplified switch S 1-S4 driving power used, and four pipes only need the two-way insulating power supply to drive.The complementary waveform of considering the first switch and second switch, the 3rd switch and the 4th switch likely overlaps, and causes the situation of the shoot throughs such as switch brachium pontis, and there is dead band in the drive waveforms of the present embodiment, has strictly avoided straight-through possibility.

The above, only for preferred embodiment of the present invention, therefore can not limit according to this scope of the invention process, the equivalence of doing according to the scope of the claims of the present invention and description changes and modifies, and all should still belong in the scope that the present invention contains.

Claims (5)

1. photovoltaic module is exported P-V characteristic optimizing device, and it is characterized in that: it comprises:

Battery pack, comprise the first, second, third and the 4th photovoltaic battery elements that output voltage is identical, by the both positive and negative polarity forward, is in series separately, by series sequence, has A1, B1 and tri-battery node of F1;

The electric discharge brachium pontis, comprise the first, second, third and the 4th diode oppositely be in series by both positive and negative polarity; There are A2, B2 and tri-electric discharge nodes of F2 by series sequence;

The electric capacity brachium pontis, comprise by positive and negative electrodes in same to the first, second, third and the 4th electric capacity be in series; There are A3, B3 and tri-capacitive nodes of F3 by series sequence

The switch brachium pontis, comprise the first, second, third and the 4th switch be in series; There are A4, B4 and tri-switching nodes of C4 by series sequence;

Wherein, the two ends of described battery pack, electric discharge brachium pontis, electric capacity brachium pontis and switch brachium pontis are all in parallel in the same way according to the direction of inner member series connection separately; Between A2 and A3, with coil L3, be connected; There is coil L1 between A3 and A4; There is coil L2 between F3 and F4; This coil L1, L2 and L3 coupling, and Same Name of Ends lays respectively at A2, A3 and F3; B1, B2, B3 and B4 are communicated with; F1, F2 and F3 are communicated with.

2. photovoltaic module is exported P-V characteristic optimizing device according to claim 1, and it is characterized in that: the electronic switch parts that described switch is electricity/photocontrol mode comprise MOSFET, diode.

3. photovoltaic module is exported P-V characteristic optimizing device according to claim 2, and it is characterized in that: the described first and the 3rd switch is the P channel mosfet; The described second and the 4th switch is N-channel MOS FET; Described the first switch drains and is connected separately with the 4th switch with second switch, described the 3rd switch; Described second switch is connected with source electrode with the 3rd switch;

Wherein, each shared one, described the first switch and second switch, the 3rd switch and the 4th switch drive ground.

4. a photovoltaic module output P-V characteristic optimizing strategy, is characterized in that, it comprises a P-V characteristic optimizing device, and it comprises:

Battery pack, comprise the first, second, third and the 4th photovoltaic battery elements that output voltage is identical, by the both positive and negative polarity forward, is in series separately, by series sequence, has A1, B1 and tri-battery node of F1;

The electric discharge brachium pontis, comprise the first, second, third and the 4th diode oppositely be in series by both positive and negative polarity; There are A2, B2 and tri-electric discharge nodes of F2 by series sequence;

The electric capacity brachium pontis, comprise by positive and negative electrodes in same to the first, second, third and the 4th electric capacity be in series; There are A3, B3 and tri-capacitive nodes of F3 by series sequence

The switch brachium pontis, comprise the first, second, third and the 4th switch be in series; There are A4, B4 and tri-switching nodes of C4 by series sequence;

The two ends of described battery pack, electric discharge brachium pontis, electric capacity brachium pontis and switch brachium pontis are all in parallel in the same way according to the direction of inner member series connection separately; Between A2 and A3, with coil L3, be connected; There is coil L1 between A3 and A4; There is coil L2 between F3 and F4; This coil L1, L2 and L3 coupling, and Same Name of Ends lays respectively at A2, A3 and F3; B1, B2, B3 and B4 are communicated with; F1, F2 and F3 are communicated with;

Wherein, the first, second, third and the 4th switch all with etc. the type of drive work of cycle, 50% duty ratio; Described the first switch and second switch, the 3rd switch and the 4th switch are complementary separately; The driving signal of described the first switch and the 3rd switch has a phase shifting angle φ;

One carrier wave V _tri, its waveform is:

$V_{\mathrm{tri}}=\left\{\begin{array}{c}\frac{\mathrm{\&omega;t}}{\mathrm{\&pi;}},[2\mathrm{k\&pi;}-\frac{\mathrm{\&pi;}}{2},2\mathrm{k\&pi;}+\frac{\mathrm{\&pi;}}{2},)\\ \mathrm{\&pi;}-\frac{\mathrm{\&omega;t}}{\mathrm{\&pi;}},[2\mathrm{k\&pi;}+\frac{\mathrm{\&pi;}}{2},2\mathrm{k\&pi;}+\frac{3\mathrm{\&pi;}}{2},)\end{array}\right.$

One square wave V ' _ref, its waveform is:

${V^{\&prime;}}_{\mathrm{ref}}=\left\{\begin{array}{c}0.5+{\mathrm{\&Delta;V}}_{\mathrm{ref}},[2\mathrm{k\&pi;}-\frac{\mathrm{\&pi;}}{2},2\mathrm{k\&pi;}+\frac{\mathrm{\&pi;}}{2},)\\ 0.5-\mathrm{\&Delta;}{V}_{\mathrm{ref}},[2\mathrm{k\&pi;}+\frac{\mathrm{\&pi;}}{2},2\mathrm{k\&pi;}+\frac{3\mathrm{\&pi;}}{2},)\end{array}\right.$

This carrier wave V _triwith square wave V ' _refsuperimposed, according to this Δ V _ref, determine phase shifting angle φ

φ=π·Δυ _ref。

5. according to claim 4 photovoltaic module output P-V characteristic optimizing strategy, it is characterized in that: described switch is MOSFET, and there is the dead band that prevents described switch bridge arm direct pass in the complementary waveform of described the first switch and second switch, the 3rd switch and the 4th switch.

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