Mppt control method and control circuit for distributed photovoltaic array

Abstract

The invention discloses an MPPT (maximum power point tracking) control method used for a distributed photovoltaic array. The method includes that a solar cell outputs voltage, a power source voltage generating module generates working voltage of a whole control circuit under the output voltage, a reference voltage module generates reference voltage, an error amplifier acquires an error signal, a PWM (pulse-width modulation) comparator acquires a PWM wave, and the solar cell is controlled to output voltage and wait a sampling signal after the PWM wave is driven; a current power value of the solar cell is input to a voltage comparator after the sampling signal is emitted, the voltage comparator stores the current power value, and at the same time, the reference voltage module regenerates reference voltage according to a comparison result; when the sampling signal is not emitted, the output voltage of the solar cell is repeatedly adjusted until the output voltage is stabilized around the reference voltage. The invention further discloses the control circuit. By the method and the circuit, scale of circuits performing MPPT control can be effectively reduced, and the control circuit is enabled to stably work.

Description

technical field [0001] The invention relates to the field of solar cell photovoltaic power generation, in particular to an MPPT control method and a control circuit for distributed photovoltaic arrays. Background technique [0002] Since the photovoltaic system composed of solar cells works in a changeable external environment, the temperature changes throughout the year and the difference in illumination during the day will have a great impact on the output of the solar cell array. At the same time, since the photovoltaic system is composed of a large number of solar cells, the mismatch between the panels and the partial shade of the panels often occur. Therefore, each panel in the photovoltaic system needs a maximum power point tracking (MPPT) circuit. , to achieve the maximum power output of the entire photovoltaic system under different conditions. [0003] At present, conventional MPPT control methods include disturbance and observation method, conductance increment me...

AI Technical Summary

Problems solved by technology

To realize these algorithms, AD / DA converters, DSP processors or single-chip microcomputers and other discrete units containing digital modules are usually required, plus some necessary DC / DC peripheral circuits, the entire control circuit is very large and complex, not only The cost is high, and due to the existence of digital modules, the size of the circuit cannot be reduced, and the overall power consumption is also difficult to reduce

[0004] In addition, the existing MPPT control methods basically add a first-level MPPT control circuit after the overall photovoltaic system, and the control circuit is basically powered by an external power supply.

However, once the photovoltaic system adopts distributed MPPT control, when the battery panels are connected in series and the voltage increases step by step, in the control circuit behind each level of battery panels, the amplitude of the square wave signal that controls the switching tube of the circuit also needs to be adjusted step by step. The level increases, which makes it difficult for the existing control methods to be applied to distributed photovoltaic MPPT systems

[0005] The patent document with the publication number 102880223A proposes a method for implementing a photovoltaic inverter MPPT analog circuit. Although this method abandons the conventional digital processing unit, it does not mention the power supply of the control circuit, and cannot rely on the provided control circuit to realize the photovoltaic system. Distributed MPPT control

In addition, the control method provided in the patent is to control each switch. The overall circuit does not have a stable control loop, that is, it relies on the method of frequency conversion control, which greatly reduces the stability of the circuit itself, and the frequency conversion circuit itself It will generate noise that is difficult to eliminate. At the same time, because there is no feedback loop, it is more sensitive to the interference of external noise, and it is also prone to errors in the process of maximum point tracking.

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