Photovoltaic inverter MPPT control method based on three-point comparison method

Abstract

The invention discloses a photovoltaic inverter MPPT control method based on a three-point comparison method. The method comprises the steps that (1) three-point continuous sampling is performed, wherein a point A, a point B and a point C on a solar cell P-V characteristic curve are selected at will for sampling, the three points are close, the voltage of the point A is U0, the power of the point A is Pa, the voltage of the point B is U0+delta U, the power of the point B is Pb, the voltage of the point C is U0-delta U, and the power of the point C is Pc; (2) the direction of voltage disturbance is judged, if Pa is smaller than Pb, a counter num plus one, or else, the counter num minus one, if Pa is greater than Pc, the counter num plus one, and or else, the counter num minus one; (3) with time T being a period, the magnitude of delta U is changed, and disturbance voltage is changed to the peak value delta Umax. By the adoption of the three-point comparison method, no judgment caused by the change of the external environment can be effectively avoided, and therefore an invertor control system can track the MPP accurately and effectively.

Description

technical field [0001] The invention relates to the field of photovoltaic inverters, in particular to a control method for maximum power point tracking of photovoltaic inverters based on a three-point comparison method. Background technique [0002] Photovoltaic inverter is the key equipment of solar photovoltaic power generation system. It converts the direct current generated by the solar photovoltaic cell array into alternating current that meets the quality requirements of the power grid and provides it to local users and the power grid. With the explosive growth of photovoltaic power plants, photovoltaic power generation efficiency is an important indicator and directly produces economic benefits. [0003] The main factors affecting the efficiency of photovoltaic inverters are: firstly, the power semiconductors are continuously chopping in the circuit to convert direct current into alternating current, and the power semiconductors generate heat loss; secondly, the react...

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Problems solved by technology

[0005] The technical problem to be solved by the present invention is that the existing two-point comparison method to determine the direction of voltage disturbance is prone to false disturbances and local maximum power points, and the improved "mountain climbing method" has compl

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