CN103490717B - A kind of photovoltaic module output P-V characteristic optimizing device and its control method - Google Patents

Abstract

The invention discloses a kind of photovoltaic module output P-V characteristic optimizing device and relevant method, it is characterised in that device includes set of cells, discharge brachium pontis, electric capacity brachium pontis, and the network that switch brachium pontis is constituted. Further, based on this optimization device, specific driving method is used to control switch brachium pontis, it is possible to obtain good single power extreme point output effect. Simple circuit of the present invention, cost is low, the problem that when can effectively solve local shades, conventional maximal power tracing algorithm is easily trapped into Local Extremum, suitable in the various photovoltaic power supply systems that local shades problem is comparatively serious, also can be widely used to the low profile photovoltaic systems such as photovoltaic illumination, being particularly suitable for the application of photovoltaic module integrated converter, compatibility is good, effect is obvious.

Description

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

Technical field

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

Background technology

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

In photovoltaic generating system, owing to output power of photovoltaic module-voltage (P-V) characteristic presents non-linear, and there is maximum power point, and its maximum power point changes along with the change of the factor such as illumination and ambient temperature, in order to maximize the output of system, it is necessary to adopt suitable maximal power tracing point technology. Guarantee system always operates in photovoltaic module maximum power point, to obtain the maximum efficiency of photovoltaic generation.

Photovoltaic module is when illumination condition is constant, and its P-V characteristic curve only one of which extreme point, i.e. maximal power tracing point, as it is shown in figure 1, V-I and the P-V characteristic curve that photovoltaic module is under different illumination conditions. But around photovoltaic generating system, it is usually present the shelter such as building or trees, its local shades formed on photovoltaic module not only results in output power of photovoltaic module to be reduced, and there are multiple extreme points in its P-V characteristic curve, as in figure 2 it is shown, the P-V characteristic curve of photovoltaic module when being local shades.Owing to the P-V characteristic curve of photovoltaic module occurs in that multiple extreme point, conventional disturbance observational method and incremental conductance method are easily trapped into Local Extremum, thus not ensuring that photovoltaic module operates in real global maximum power point, cause energy loss, inefficiency.

In order to improve the output of the photovoltaic module with multiple power extreme point, existing corresponding strategies is devoted to improve and propose novel global maximum power point track algorithm aspect at present, there is a common problem in these methods: after multiple extreme points occurs in photovoltaic module, these methods can only be passive the search current global maximum power point of 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; Meanwhile, the parameter designing of MPPT maximum power point tracking algorithm and realize more complicated.

Summary of the invention

The primary and foremost purpose of the present invention is to provide a kind of output P-V characteristic optimizing device for photovoltaic module and relevant control method, photovoltaic module is made still to have a peak power extreme point under the severe lighting effects such as local shades, ensure the realization of global maximum power extreme point, ensure that the photovoltaic module energy conversion efficiency when local shades.

It is a further object to provide a kind of output P-V characteristic optimizing device for photovoltaic module and relevant control method, under the premise ensureing output usefulness, original disturbance observational method and incremental conductance method equipment can be mated, rear class equipment will not be made to increase extra burden, there is versatility.

Technical scheme is as follows:

Photovoltaic module output P-V characteristic optimizing device, it is characterised in that: it includes:

Set of cells, including the first, second, third and fourth photovoltaic battery elements that output voltage is identical, is each in series by both positive and negative polarity forward, has three battery node of A1, B1 and F1 by series sequence;

Electric discharge brachium pontis, including the first, second, third and fourth diode being reversely in series by both positive and negative polarity; By series sequence, there is A2, B2 and F2 three electric discharge node;

Electric capacity brachium pontis, including by positive and negative electrodes in same to the first, second, third and fourth electric capacity being in series; By series sequence, there are three capacitive nodes of A3, B3 and F3

Switch brachium pontis, including the first, second, third and fourth switch being in series; By series sequence, there are three switching nodes of A4, B4 and C4;

Wherein, the direction that all connect according to respective inner member in the two ends of described set of cells, electric discharge brachium pontis, electric capacity brachium pontis and switch brachium pontis is in parallel in the same direction; It is connected with coil L3 between A2 and A3; There is between A3 and A4 coil L1; There is between F3 and F4 coil L2; This coil L1, L2 and L3 couple, and Same Name of Ends lays respectively at A2, A3 and F3; B1, B2, B3 and B4 connection; F1, F2 and F3 connect.

The improvement of this programme structure has:

In preferred version, described switch is the electrical switch parts of electrical/optical control mode, including MOSFET, diode. Wherein MOSFET can also use transistor, photoelectrical coupler etc. to substitute.

In preferred version, described first and the 3rd switch be P-channel MOSFET; Described second and the 4th switch be N-channel MOS FET; Described first switch is connected with each drain electrode of the 4th switch with second switch, described 3rd switch; Described second switch and the 3rd switch are connected with source electrode;

Wherein, described first switch is each with second switch, the 3rd switch and the 4th switch shares one drivingly.

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

Wherein, first, second, third and the 4th switch all with etc. the cycle, 50% dutycycle type of drive work; Described first switch is each complementary with the 4th switch with second switch, the 3rd switch; The driving signal of described first switch and the 3rd switch has a phase shifting angle ��;

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 �� V_ref, it is determined that phase shifting angle ��

��=������_ref��

Further, on such scheme basis, described switch is MOSFET, and the complementary waveform that described first switch switchs with the 4th with second switch, the 3rd switch exists the dead band preventing described switch bridge arm direct pass.

The beneficial effect of this programme has:

1. simple circuit of the present invention, cost is low, the problem that when can effectively solve local shades, conventional maximal power tracing algorithm is easily trapped into Local Extremum, suitable in the various photovoltaic power supply systems that local shades problem is comparatively serious, also can be widely used to 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 so that it is possessed the passage of power-balance. So, this device can realize the decile output of each photovoltaic battery elements voltage, it is simple to obtains single power extreme point. Switch brachium pontis is controlled operation, makes each switch conduction and cut-off in a proper manner, such that it is able to obtain, from this device, the effect that each photovoltaic battery elements E1-E4 output voltage is equal.

3. this programme compatibility uses the maximum power point tracing method that original disturbance observational method or incremental conductance method etc. are conventional can ensure that system operates in maximal power tracing point. There is good compatibility.

4. the electrical switch parts that switch S1-S4 is electrical/optical control mode of the present embodiment, including MOSFET, diode. MOSFET is used to be conducive to integrating with other electronic control systems, it is achieved miniaturization, integrated.

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 photovoltaic module different illumination conditions;

The P-V characteristic curve schematic diagram of photovoltaic module when Fig. 2 is local shades;

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

Fig. 4 is the equivalent circuit diagram that its neutral balance of embodiment illustrated in fig. 3 controls;

Fig. 5 is Fig. 4 primary and secondary voltage and current waveform realizing neutral-point voltage balance;

Fig. 6 Phaseshift controlling angle of phase displacement �� realizes schematic diagram;

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

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

Detailed description of the invention

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

First Fig. 3 illustrates the circuit diagram of this embodiment device part. This device includes four major parts, is set of cells, electric discharge brachium pontis, electric capacity brachium pontis and switch brachium pontis respectively.

Set of cells, including the first, second, third and fourth photovoltaic battery elements that output voltage is identical, is E1, E2, E3 and E4 respectively, is each in series by both positive and negative polarity forward, has three battery node of A1, B1 and F1 by series sequence (from top to bottom);

Electric discharge brachium pontis, including the first, second, third and fourth diode being reversely in series by both positive and negative polarity, is D1, D2, D3 and D4 respectively;By series sequence (from top to bottom), there is A2, B2 and F2 three electric discharge node;

Electric capacity brachium pontis, including by positive and negative electrodes in same to the first, second, third and fourth electric capacity being in series; It is C1, C2, C3 and C4 respectively, by series sequence (from top to bottom), there are three capacitive nodes of A3, B3 and F3

Switch brachium pontis, including the first, second, third and fourth switch being in series, is S1, S2, S3 and S4 respectively; By series sequence (from top to bottom), there are three switching nodes of A4, B4 and C4;

Wherein, the direction all connected according to respective inner member in the two ends of set of cells, electric discharge brachium pontis, electric capacity brachium pontis and switch brachium pontis is in parallel in the same direction, is namely connected in parallel on OUT1 and OUT2 two ends; It is connected with coil L3 between A2 and A3; There is between A3 and A4 coil L1; There is between F3 and F4 coil L2; This coil L1, L2 and L3 couple, and Same Name of Ends lays respectively at A2, A3 and F3; B1, B2, B3 and B4 connection; F1, F2 and F3 connect.

The structure of this device is by above-mentioned brachium pontis so that it is possessed the passage of power-balance. So, this device can realize the decile output of each photovoltaic battery elements voltage, it is simple to obtains single power extreme point. S1-S4 is operated, makes each switch conduction and cut-off in a proper manner, such that it is able to obtain, from this device, the effect that each photovoltaic battery elements E1-E4 output voltage is equal.

Use square wave drive S1-S4, wherein the dutycycle of S1-S4 be 50% and the cycle identical. S1 and S2, S3 and S4 drive signal complementary

For electric capacity C1 and C2, work as U_C1>U_C2, after S1 turns on, voltage is added in coupling inductance armature winding L₁On, owing to L1 and the L3 number of turn is identical, secondary windings L3 induces identical voltage U_C1, C2 is charged by L3 by D2. Through some switch periods, when two capacitance voltages are identical, L3 does not have electric current flow through. Vice versa.

When S1 and S3 is absent from phase shift, S1 and S3 drives phase place identical, it is ensured that the voltage self-balancing between electric capacity C1 and C3. Now S2 and S4 drives phase place also identical, it is ensured that the voltage self-balancing between electric capacity C2 and C4.

On the basis of above-mentioned self-balancing, for realizing overall power-balance by this device, to guarantee single power extreme point, in addition it is also necessary to the process carrying out neutral point voltage balance between C1-C3 and C2-C4.

Neutral point voltage balance is realized by phase-shift control mode. Neutral balance realization mechanism is similar with bi-directional half bridge DC-DC converter, and its equivalent circuit is as shown in Figure 4. This junction, circuit midpoint is equivalent to the anode of the primary negative terminal of bi-directional DC-DC half-bridge converter and primary side and connects together. L_s1With L_s2Respectively coupling inductance primary leakage inductance and secondary leakage inductance. Fig. 5 is the desired voltage current waveform that coupling inductance is primary with secondary, and the relational expression of the power of this positive side of figure bridge arm and minus side transmission is:

$P=\frac{U_{P_2-M}\·U_{M-N_2}\·\mathrm{\φ}\·(\mathrm{\π}-\mathrm{\φ})}{{\mathrm{\ωL}}_s\mathrm{\π}}---\left(0.1\right)$

In formula, L_sFor the leakage inductance sum of three winding coupling inductance primary leakage inductance and the second winding, U_P2-MFor the node P2 voltage to midpoint M, that is first and second liang of capacitance voltage sum. U_M-N2For midpoint M to node P₂Voltage, that is third and fourth two capacitance voltages sum. �� is the phase shifting angle of the positive side of brachium pontis and minus side.

Phaseshift controlling realizes principle as shown in Figure 6. ��_refIt is a reference signal, ��_triFor having the carrier signal of unit magnitude values. �� is the service time of switch in a cycle (any one in S1-S4), ��_ref' formed by one square wave of superposition in reference signal.

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:

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

As carrier wave ��_triSlope be on the occasion of time, this square wave be also on the occasion of, as carrier wave ��_triDuring for negative value, this square wave is also then negative value. Therefore, ��_triWith ��_ref' crossing comparison point always than ��_triWith ��_refCrossing comparison point delayed. Lagging phase angle and square wave �� ��_refProportional:

��=������_ref(0.2)

As �� ��_ref< when 0, then can obtain an advanced phase angle.

Angle of phase displacement �� control block diagram is as it is shown in fig. 7, ��^*For the lagging phase of brachium pontis minus side reference signal, ��_P2-MFor node P₂Relative to the voltage of midpoint M, ��_M-N2For midpoint M relative to node N₂Voltage. Low pass filter is for filtering the ripple component of two DC voltages detected.

Such as Fig. 8, P-V characteristic curve schematic diagram for the photovoltaic module before and after output P-V characteristic optimizing device correction, can be seen that, virgin curve 1 has multiple extreme point, and curve 1 is the latter through exporting P-V characteristic optimizing, the P-V characteristic curve only one of which extreme value of photovoltaic module, and the output ratio of maximum power point be not optimised before be greatly increased. Visible, this result uses the maximum power point tracing method that original disturbance observational method or incremental conductance method etc. are conventional can ensure that system operates in maximal power tracing point. There is good compatibility.

The electrical switch parts that switch S1-S4 is electrical/optical control mode of the present embodiment, including MOSFET, diode. MOSFET is used to be conducive to integrating with other electronic control systems, it is achieved miniaturization, integrated.

First switch S1 and the three switchs S3 and is P-channel MOSFET; Second switch S2 and the four switchs S4 and is N-channel MOS FET; First switch S1 and second switch S4, the 3rd switch S3 and the four switch S4 each drain and are connected; Second switch S2 and the three switchs S3 and is connected with source electrode; Wherein, described first switch is each with second switch, the 3rd switch and the 4th switch shares one drivingly. This form simplifies switch S1-S4 driving used power supply, and four pipes have only to two-way insulating power supply and can drive. Considering that the first switch is likely to occur overlapping with second switch, the 3rd switch with the complementary waveform of the 4th switch, cause the situation of the shoot throughs such as switch brachium pontis, there is dead band in the drive waveforms of the present embodiment, strictly avoids straight-through possibility.

The above, be only present pre-ferred embodiments, therefore can not limit scope of the invention process according to this, and the equivalence namely made 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 output P-V characteristic optimizing device, it is characterised in that: it includes:

Set of cells, including the first, second, third and fourth photovoltaic battery elements that output voltage is identical, is each in series by both positive and negative polarity forward, has three battery node of A1, B1 and F1 by series sequence;

Electric discharge brachium pontis, including the first, second, third and fourth diode being reversely in series by both positive and negative polarity; By series sequence, there is A2, B2 and F2 three electric discharge node;

Electric capacity brachium pontis, including by positive and negative electrodes in same to the first, second, third and fourth electric capacity being in series; By series sequence, there are three capacitive nodes of A3, B3 and F3

Switch brachium pontis, including the first, second, third and fourth switch being in series; By series sequence, there are three switching nodes of A4, B4 and C4;

Wherein, the direction that all connect according to respective inner member in the two ends of described set of cells, electric discharge brachium pontis, electric capacity brachium pontis and switch brachium pontis is in parallel in the same direction; It is connected with coil L3 between A2 and A3;There is between A3 and A4 coil L1; There is between F3 and F4 coil L2; This coil L1, L2 and L3 couple, and Same Name of Ends lays respectively at A2, A3 and F3; B1, B2, B3 and B4 connection; F1, F2 and F3 connect.

2. photovoltaic module exports P-V characteristic optimizing device according to claim 1, it is characterised in that: described switch is the electrical switch parts of electrical/optical control mode, including MOSFET, diode.

3. according to claim 2 photovoltaic module output P-V characteristic optimizing device, it is characterised in that: described first and the 3rd switch be P-channel MOSFET; Described second and the 4th switch be N-channel MOS FET; Described first switch is connected with each drain electrode of the 4th switch with second switch, described 3rd switch; Described second switch and the 3rd switch are connected with source electrode;

Wherein, described first switch is each with second switch, the 3rd switch and the 4th switch shares one drivingly.

4. a photovoltaic module output P-V characteristic optimizing method, it is characterised in that it includes a P-V characteristic optimizing device, and it includes:

Set of cells, including the first, second, third and fourth photovoltaic battery elements that output voltage is identical, is each in series by both positive and negative polarity forward, has three battery node of A1, B1 and F1 by series sequence;

Electric discharge brachium pontis, including the first, second, third and fourth diode being reversely in series by both positive and negative polarity; By series sequence, there is A2, B2 and F2 three electric discharge node;

Electric capacity brachium pontis, including by positive and negative electrodes in same to the first, second, third and fourth electric capacity being in series; By series sequence, there are three capacitive nodes of A3, B3 and F3

Switch brachium pontis, including the first, second, third and fourth switch being in series; By series sequence, there are three switching nodes of A4, B4 and C4;

The direction all connected according to respective inner member in the two ends of described set of cells, electric discharge brachium pontis, electric capacity brachium pontis and switch brachium pontis is in parallel in the same direction; It is connected with coil L3 between A2 and A3; There is between A3 and A4 coil L1; There is between F3 and F4 coil L2; This coil L1, L2 and L3 couple, and Same Name of Ends lays respectively at A2, A3 and F3; B1, B2, B3 and B4 connection; F1, F2 and F3 connect;

Wherein, first, second, third and the 4th switch all with etc. the cycle, 50% dutycycle type of drive work; Described first switch is each complementary with the 4th switch with second switch, the 3rd switch; The driving signal of described first switch and the 3rd switch has a phase shifting angle ��;

One carrier wave V_tri, its waveform is:

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

One square wave V '_ref, its waveform is:

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

This carrier wave V_triWith square wave V '_refSuperimposed, according to this �� V_ref, it is determined that phase shifting angle ��

��=�� �� ��_ref��

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