Background technology
At present, the development and utilization of regenerative resource receives the attention of national governments day by day, and photovoltaic generation is the important component part of regenerative resource, and following photovoltaic generation has very big development potentiality.According to EPIA (EPIA) in 2011 prediction, to the year two thousand fifty whole Europe 100% the energy all provide by photovoltaic generation.
Development along with photovoltaic industry; With middle-size and small-size is main BIPV (Building Integrated Photovoltaics; BIPV) will become one of principal mode of following photovoltaic generation; And intensive high building building, tree shade and cloud layer etc. can cause certain covering to photovoltaic cell unavoidably; Characteristic by photovoltaic cell is original can know that photovoltaic cell output power under the condition of covering will reduce, and then output power decline is obvious more to cover more serious (intensity of illumination that promptly arrives photovoltaic cell is more weak).
Existing photovoltaic power generation technology, like constant voltage process, disturbance observation, increment conductance method etc., mainly research all is not have to cover the MPPT maximum power point tracking under the situation, fails to consider the serious power loss problem of bringing of covering.At present; There is a small amount of article to propose even maximum power point (the Maximum Power Point down of uneven illumination abroad; MPP) tracking; And domesticly seldom have article to propose, and there is following problem in the method that has proposed: increase the hardware device input, precision is not high, efficient is low, algorithm problems such as too complicacy, bad adaptability, practicality be not strong.
Photovoltaic cell component is formed by a plurality of photovoltaic cell SP usually, and photovoltaic array is made up of a plurality of photovoltaic cell component SP usually, and photovoltaic generating system then is made up of through SP a plurality of photovoltaic arrays.When part photovoltaic module crested (the suffered uneven illumination of photovoltaic array is even) is arranged in the photovoltaic array; Whole photovoltaic array output current ability that should parallel connection will be restricted; But there is not the parallel photovoltaic array output current ability of crested can not reduce fully; If both are cascaded and adopt the generating of traditional MPPT maximum power point tracking algorithm controls total system, then can significantly reduce the output power of system, this power loss can reach more than 30% even be more serious.Therefore, propose a kind of inhomogeneous maximum power point tracing method of illumination photovoltaic generating system down, can significantly reduce and cover the serious decline that brings the total system output power.
Summary of the invention
In order to overcome the shortcoming of above-mentioned prior art, the present invention provides maximum power point of photovoltaic power generation system tracking under a kind of uneven illumination, need not to increase additional hardware equipment, has reduced system because the photovoltaic array uneven illumination is spared and has brought serious power loss.
The present invention realizes with following technical scheme: maximum power point of photovoltaic power generation system tracking under a kind of uneven illumination; Photovoltaic generating system brings into operation under photovoltaic array illumination evenly and has been in maximum power point M place, writes down the voltage
and the electric current
of photovoltaic array output this moment; If it is even that this moment, uneven illumination appearred in photovoltaic array; The voltage
and the electric current
of photovoltaic array output will change; Detect photovoltaic array output voltage
and electric current
after changing; Judge through the MPPT maximum power point tracking device whether draw photovoltaic array exists uneven illumination even then; If evenly then carrying out variable step disturbance observation, illumination obtains maximum power point; If the even reference voltage
first that then calculates of uneven illumination; Utilize variable step disturbance observation to obtain first local maximum power point again; And record correspondent voltage
and power
; Increase reference voltage then to
; Utilize variable step disturbance observation to obtain second local maximum power point again; And record correspondent voltage
and power
; And the like; Gained voltage is designated as successively
,
...,
; Power be designated as successively
,
...,
; Compare this
individual local maximum power value again; The reference voltage
that extracts maximum local maximum power point and the voltage of correspondence is exported as the MPPT maximum power point tracking device; Last controller calculates dutycycle according to the reference voltage
of MPPT maximum power point tracking device output, traces into global maximum power point.
The invention has the beneficial effects as follows: significantly reduced system because the photovoltaic array uneven illumination is spared and brought serious power loss; This method almost only from the realization of software consideration algorithm, need not to increase additional hardware equipment, has significantly reduced cost, and whole algorithm is simple relatively, and software is realized also than being easier to; Maximal power tracing device and controller adopt DSP control, have improved overall optical photovoltaic generating system algorithm accuracy, stability and real-time.
Embodiment
As shown in Figure 1; Photovoltaic array 11 connects
counnter attack diode 12;
Counnter attack diode 12 connects photovoltaic array outgoing side
electric capacity 22; Photovoltaic array outgoing side
electric capacity 22 connects
Boost circuit 21; Boost
circuit 21 connects the big
electric capacity 14 of DC filtering; The big
electric capacity 14 of DC filtering connects
voltage source inverter 15;
Voltage source inverter 15 connects
LCL filtering 17,
LCL filtering 17 connects
local load 18 and three-phase alternating current isolating
switch 19; Three-phase alternating current isolating
switch 19 connects three
phase network 20; The voltage
of photovoltaic array 11 outputs is connected MPPT maximum power
point tracking device 13 with electric current
through sensor; MPPT maximum power
point tracking device 13 output reference voltages
connect
controller 16;
Controller 16 output pulses
connect
Boost circuit 21; Thereby MOSFET turns on and off in the
control Boost circuit 21, and the adjustment load current satisfies the global maximum power of output power coupling photovoltaic array 11 outputs.MPPT maximum power
point tracking device 13 all adopts DSP control with
controller 16, has improved overall optical photovoltaic generating system algorithm accuracy, stability and real-time.
As shown in Figures 2 and 3,
curve 1 is that output current and voltage response are evenly descended in photovoltaic array (PV) illumination;
Curve 2 is even output current and voltage responses down of photovoltaic array uneven illumination; Curve 3 is that output power and voltage response are evenly descended in photovoltaic array illumination;
Curve 4 is even output power and voltage responses down of photovoltaic array uneven illumination.
Inverse parallel number of diodes for photovoltaic array;
Output current for photovoltaic array;
Output voltage for photovoltaic array;
Reference voltage for the output of MPPT maximum power point tracking device;
pPulse signal for controller output;
Be the short-circuit current value under the photovoltaic array illumination evenly;
Be the short-circuit current value of photovoltaic array uneven illumination under even; M is the maximum power point under the photovoltaic array illumination evenly;
Be the maximum power point current value under the photovoltaic array illumination evenly;
Be the maximum power point voltage value under the photovoltaic array illumination evenly;
Evenly descend the voltage of maximum power point M for illumination
With photovoltaic array inverse parallel number of diodes
Ratio; A1 is the even starting point of following the tracks of local maximum power point first down of photovoltaic array uneven illumination; A2 increases voltage through M1 down for the photovoltaic array uneven illumination is even
After the working point; A
n-2 for the photovoltaic array uneven illumination even down through M
n-3 increase voltage
After the working point; A
n-1 for the photovoltaic array uneven illumination even down through M
n-2 increase voltage
After the working point; A
nFor the photovoltaic array uneven illumination is spared down through M
n-1 increases voltage
After the working point;
It is build-up of voltage
Coefficient;
Voltage for local maximum power point M1;
Voltage for local maximum power point M2;
Voltage for local maximum power point Mn-2;
Be local maximum power point M
n-1 voltage;
, local maximum power point M
nVoltage; M1 is first local maximum power point; M2 is second local maximum power point; M
n-2, n-2 local maximum power point; M
n-1, n-1 local maximum power point; M
nBe n local maximum power point;
Power for local maximum power point M1;
Power for local maximum power point M2;
Be local maximum power point M
n-2 power;
Be local maximum power point M
n-1 power;
Be local maximum power point M
nPower;
For judging the even voltage difference that presets of photovoltaic array uneven illumination.
As shown in Figure 4, be example with the stage type photovoltaic generating system, the concrete steps of this method are following:
A, Detect the current moment PV array output voltage signal
and the current signal
;
B, if
, then continue down execution in step C; Otherwise, carry out variable step disturbance observation;
The value of C, calculating
; If
then continues down to carry out D; Otherwise, carry out variable step disturbance observation;
is the even voltage difference that presets of photovoltaic array uneven illumination, chooses according to actual open-circuit voltage values;
D, calculating starting potential are blocked a some V0;
; Wherein, The coefficient of build-up of voltage
is the illumination voltage
that evenly descends maximum power point M and the ratio of photovoltaic array inverse parallel number of diodes
, i.e.
;
is the coefficient of the coefficient
of build-up of voltage; Suitably choose according to the actual situation of covering,
;
E, be starting point with
; Utilize variable step disturbance observation to trace into local maximum power point M1 first; And the voltage
and the power
at record M1 place this moment; Increase reference voltage then to
; Utilize variable step disturbance observation to trace into local maximum power point M2 once more; And the voltage
and the power
at record M2 place this moment; The rest may be inferred; Gained voltage is designated as successively
,
...,
, power be designated as successively
,
...,
;
F, comparison
,
...,
Size, find out the maximum point of local maximum power point and extract the reference voltage of corresponding voltage as MPPT maximum power point tracking device output
, last controller is according to the reference voltage of MPPT maximum power point tracking device output
Calculate dutycycle, drive output pulse signal through MOSFET
pGo the MOSFET that controls the Boost circuit to turn on and off, thereby make total system trace into global maximum power point.
Protection scope of the present invention is not limited to the above embodiments.