The control method of MPPT optimizers in a kind of photovoltaic generating system
Technical field
The present invention relates to a kind of control of MPPT optimizers in technical field of photovoltaic power generation, more particularly to photovoltaic generating system
Method.
Background technology
Large-scale ground photovoltaic plant is typically confluxed using header box, centralized photovoltaic inverter grid-connected.Existing photovoltaic electric
Pond plate operating voltage is generally 500-700V, and with external environment, such as change of environment temperature, irradiation level, photovoltaic cell
The voltage of plate can be in interior fluctuation on a large scale.To realize DC voltage higher, maximum work can be carried out with photovoltaic submatrix cell distribution
The mode of rate point tracking (MPPT) optimization, that is, install MPPT optimizers additional.MPPT optimizers can be separately positioned at battery pack string side,
Can also be integrated with header box, form so-called intelligent junction box.Photovoltaic is installed additional by centralized inverter front end
The MPPT optimizers of submatrix unit, on the one hand can reduce the MPPT match penalties of photovoltaic module, on the other hand can also improve
The output characteristics of photovoltaic battery panel.MPPT optimizers generally can rise high voltage using Boost circuit, and circuit topology is as schemed
Shown in 1.Existing control mode typically all uses pulse width modulation (PWM) control mode, and switching frequency is constant.When load compared with
When low, or input voltage and output voltage difference it is smaller when, inductive current ripple can be smaller, the iron loss of inductor also compared with
It is small, but, now switching device works also according to original frequency, and switching loss is basically unchanged.Under this operating mode, use
Surely work is unfavorable for the lifting of conversion efficiency to PWM frequently.
The content of the invention
It is an object of the invention to by a kind of control method of MPPT optimizers in photovoltaic generating system come more than solving
The problem that background section is mentioned.
It is that, up to this purpose, the present invention uses following technical scheme:
The control method of MPPT optimizers in a kind of photovoltaic generating system, it includes:According to the work of photovoltaic generating system
State, according to the switching frequency of predeterminated frequency regulative mode real-time adjustment MPPT optimizers.
Especially, the predeterminated frequency regulative mode is specifically included:The switching frequency of MPPT optimizers is with PWM duty cycle
Change and change, when PWM duty cycle is more than preset value, the switching frequency of MPPT optimizers keeps default maximum switching frequency value
It is constant, when PWM duty cycle be less than preset value when, the switching frequency of MPPT optimizers with certain amplitude linear reduction, until reaching
During lower frequency limit, keep constant.
Especially, the predeterminated frequency regulative mode is specifically included:When PWM duty cycle is more than 0.2, MPPT optimizers
Switching frequency keeps 16KHZ constant, and when PWM duty cycle is less than 0.2, the switching frequency of MPPT optimizers is linear with certain amplitude
Reduce, until when reaching 4KHZ, keeping constant.
Work of the control method of MPPT optimizers according to photovoltaic generating system in photovoltaic generating system proposed by the present invention
State, the switching frequency of real-time adjustment MPPT optimizers is simple and easy to apply to realize the maximization of system effectiveness, can be certain
Photovoltaic generating system generated energy is lifted in degree, the gene-ration revenue of photovoltaic system is lifted.
Brief description of the drawings
Fig. 1 is MPPT optimizers circuit topology schematic diagram provided in an embodiment of the present invention;
Fig. 2 is the function relation figure of switching frequency provided in an embodiment of the present invention and PWM duty cycle.
Specific embodiment
The invention will be further described with reference to the accompanying drawings and examples.It is understood that tool described herein
Body embodiment is used only for explaining the present invention, rather than limitation of the invention.It also should be noted that, for the ease of retouching
State, part rather than full content related to the present invention is illustrate only in accompanying drawing, it is unless otherwise defined, used herein all
Technology and scientific terminology are identical with the implication that those skilled in the art of the invention are generally understood that is belonged to.It is used herein
Term be intended merely to describe specific embodiment, it is not intended that in limitation the present invention.
The control method of MPPT optimizers is specifically included in photovoltaic generating system in the present embodiment:According to photovoltaic generating system
Working condition, according to the switching frequency of predeterminated frequency regulative mode real-time adjustment MPPT optimizers.
For photovoltaic generating system, improving conversion efficiency means more generated energy, it may be considered that in some operating modes
Decline low switching frequency, reduce switching loss.The reduction of switching frequency, can cause inductance ripple current to increase, and iron loss increases.But
Boost circuit operative duty cycles are smaller, and inductance ripple current is smaller.Switching frequency can be now reduced, it is appropriate to increase electricity
Sense iron loss, exchanges the significantly reduction of switching loss for, improves the transformation efficiency of converter.
It is optimal as principle with photovoltaic generating system gross efficiency, determine the mode of frequency conversion and the scope of frequency conversion.MPPT optimizes
The switching frequency of device determines frequency work with PWM duty cycle as variable change during higher than certain dutycycle, dutycycle is less than certain value
When, working frequency reduction, dutycycle is smaller, and working frequency is lower.
Predeterminated frequency regulative mode is specifically included described in the present embodiment:The switching frequency of MPPT optimizers is accounted for PWM
The change of empty ratio and change, when PWM duty cycle is more than preset value, the switching frequency of MPPT optimizers keeps default maximum switch
Frequency values are constant, when PWM duty cycle is less than preset value, the switching frequency of MPPT optimizers with certain amplitude linear reduction, directly
When lower frequency limit is reached, keep constant.Specifically, as shown in Fig. 2 when PWM duty cycle be more than 0.2 when, MPPT optimizers
Switching frequency keeps 16KHZ constant, and when PWM duty cycle is less than 0.2, the switching frequency of MPPT optimizers is linear with certain amplitude
Reduce, until when reaching 4KHZ, keeping constant.
, according to the working condition of photovoltaic generating system, the switch of real-time adjustment MPPT optimizers is frequently for technical scheme
Rate, it is simple and easy to apply to realize the maximization of system effectiveness, photovoltaic generating system generated energy can be to a certain extent lifted, carry
Rise the gene-ration revenue of photovoltaic system.
The preferred embodiments of the present invention are the foregoing is only, is not intended to limit the invention, for those skilled in the art
For, the present invention can have various changes and change.It is all any modifications made within spirit and principles of the present invention, equivalent
Replace, improve etc., should be included within the scope of the present invention.