Three-phase CLC immittance converter-based photovoltaic grid-connected topology and power control method

Abstract

The invention provides a three-phase CLC immittance converter-based photovoltaic grid-connected topology and belongs to the technical field of photovoltaic power generation. The three-phase CLC immittance converter-based photovoltaic grid-connected topology comprises a parallel photovoltaic array, an LC low-pass filter circuit, a current-type three-phase bridge inverter circuit, a three-phase CLC immittance conversion circuit and a grid-connected circuit, wherein a modulation wave frequency of the current-type three-phase bridge inverter circuit is consistent with a resonant frequency of the three-phase CLC immittance conversion circuit and is equal to a 50Hz grid frequency; and generated power of the parallel photovoltaic array is controlled through regulating a phase of a modulation wave of the current-type three-phase bridge inverter circuit. The three-phase CLC immittance converter-based photovoltaic grid-connected topology has the advantages that the photovoltaic array is connected in parallel, so that additional power loss caused by local shadow shielding can be eliminated; voltage required for grid connection can be obtained without a booster circuit; a relatively high harmonic characteristic can be obtained without a filter circuit; the output power of the photovoltaic array can be controlled through controlling the phase of the modulation wave; and MPPT control is simplified.

Description

technical field [0001] The invention belongs to the technical field of photovoltaic power generation, and in particular relates to a photovoltaic grid-connected topology and power control method based on a three-phase CLC impedance converter. Background technique [0002] Photovoltaic power generation has the advantages of no noise, no pollution, low failure rate, and easy maintenance. It is an ideal sustainable green energy source. Although in recent years, affected by various factors, the development of the photovoltaic industry has been at a low ebb, but in the long run, its application prospects are still very broad. The I-V characteristics of photovoltaic cell output are as figure 1 As shown, in its output voltage range, it mainly shows the characteristics of a current source, and it becomes an approximate voltage source near the open circuit voltage. Restricted by the output characteristics, the output power of photovoltaic cells has a maximum power point, such as ...

AI Technical Summary

Problems solved by technology

Obviously, in this case, the traditional MPPT algorithm is easy to fall into a local optimum, and a more complex algorithm must be used to find the real maximum power point, and the more components in series, the more local peak points, and the more complex the algorithm

In addition, under partial shading, if the shadowed photovoltaic modules are bypassed by bypass diodes, these photovoltaic modules not only do not generate electricity, but also become energy-consuming devices; The normal photovoltaic modules connected in series will inevitably reduce the output current and reduce the power output

It can be seen that no matter what the above situations are, the photovoltaic array will lose some power, so that the maximum power output cannot be achieved, and the more components connected in series, the more power is wasted

[0004] At present, various mature technical solutions only focus on selecting the best of the above two situations, without further considering the power loss caused by shading to the series photovoltaic array

In fact, this part of the power may be much larger than the power increase obtained through the MPPT algorithm

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