Inversion control method of photovoltaic grid-connected inverter

Abstract

The invention discloses an inversion control method of a photovoltaic grid-connected inverter, which comprises the steps of collecting ia, ib and ic; performing clark conversion to obtain ialpha, ibelta and iz; performing park conversion on the ialpha and the ibelta to obtain isq and isd; performing addition-subtraction and comparing between the isq and the isd as well as isqref and isdef respectively; enabling the modified and compared outcome to pass the rear voltage reference values Vsqref and Vsdref of a first PI (proportional-integral) controller, and generating Vsalpharef and Vsbeltaref through the park conversion; outputting and overlapping the Vsalpharef and Vsbeltaref passing through an SVM (space vector modulation) controller onto the input end of a PWM (pulse width modulation) controller; performing addition-subtraction and comparison on the zero sequence current iz and the zero sequence reference current izref and overlapping the outcome, obtained after addition-subtraction and comparison and passing a second PI controller, to the input end of the PWM controller, and adjusting the voltage by the PWM controller.

Description

technical field [0001] The invention relates to an inverter control method of a photovoltaic grid-connected inverter. Background technique [0002] Such as this figure 1 As shown, the traditional NPC three-level inverter bridge generally adopts the traditional space vector modulation method, which can effectively reduce the size of the output THD. But for the inverter system using three-level SVM modulation algorithm. Although it has greatly improved the output harmonics and common-mode voltage equivalent to the traditional two-level, but for photovoltaic grid-connected systems, the emission generated by its common-mode voltage is also likely to cause EMC to exceed the standard. EMI filter design is difficult and expensive. [0003] like figure 2 As shown, in the three-level space vector (SVM) control algorithm, the common mode voltage value has the following situations (assuming that when the upper transistor of each phase is turned on, the voltage is P(Vdc / 2); when th...

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Problems solved by technology

If you also use Figure 5 and Figure 6 control method, since the connection between O and M points exists, then , for the 3rd and 3rd multiple harmonic currents generated by the three phases a, b, and c, most of them will return from O to M on the AC current, so that Iz will be generated on each of the 3rd and 3rd multiple harmonics, so that The DQ control method cannot directly control the possible oscillating current

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