Method for improving grid-connected performance by variable switching frequency

Abstract

The invention discloses a method for improving grid-connected performance by variable switching frequency. The method comprises the following steps of calculating the output power value of a grid-connected inverter by detecting the voltage value of a grid and the grid-connected current value of the grid-connected inverter in real time; and dynamically adjusting the switching frequency value of a power switching tube of the grid-connected inverter according to the output power value of the grid-connected inverter. With the adoption of the method for adjusting the switching frequency of the power switching tube, the problem that the grid-connected current harmonics are bad in case that the output power of the grid-connected inverter is smaller is solved and the pollution to the grid is reduced. Meanwhile the method has the advantages of improving the inversion frequency in case that the output power of the grid-connected inverter is larger, reducing the size of an LC filter, decreasing the cost, improving the temperature rise, and enhancing the system reliability.

Description

technical field [0001] The invention relates to a control method of a grid-connected inverter, more specifically a method for improving grid-connected performance by variable switching frequency. Background technique [0002] The existing single-phase or three-phase switching frequency is fixed. Regardless of the single-stage, bipolar, control vector or other control methods, the high-frequency switching frequency is set at a fixed frequency point. However, for grid-connected performance The index requires that the efficiency must be greater than the specified value, and the grid-connected current harmonics should be less than the specified value. [0003] In the grid-connected application of photovoltaic grid-connected inverters, due to the uncertainty of sunlight, the energy of photovoltaic grid-connected power generation is also constantly changing with the intensity of sunlight on the photovoltaic panels. The output power is variable. In the case of relatively small ou...

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Problems solved by technology

In the case of relatively small output power, the grid-connected current harmonics are large at this time. In order to reduce the grid-connected current harmonics, the LC filter is usually used to achieve the target requirements when the switching frequency is fixed, but the large When the output power of the filter is large, the efficiency of the whole machine is low, the cost is high, the temperature rise is poor, and the reliability of the whole machine is low

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