Three-ring control method and three-ring control device of single-stage type photovoltaic grid-connected inverter system

Abstract

The invention discloses a three-ring control method and a three-ring control device of a single-stage type photovoltaic grid-connected inverter system. Three-ring control comprises a maximum power tracking outer ring, a direct-current voltage middle ring and a grid-connected current inner ring. Direct-current side voltage ring control is added so as to guarantee that the system can respond rapidly when outside illumination is reduced suddenly, direct-current bus voltage is stable in an operation process, and grid-connected current is not distorted. A maximum power tracking method adopts a step-variable disturbance observation method to enable the system to be operated at different voltage points so as to search the maximum power point rapidly. The control device comprises a sampling circuit, a capturing circuit, a digital signal processor (DSP) controller, a driving circuit and the like, and signals generated by the DSP controller are amplified by the driving circuit and sent to an inverter bridge to drive a switch tube. The control method can achieve that the single-stage type photovoltaic grid-connected inverter system can track the maximum power point rapidly when illumination varies frequently and is operated stably.

Description

technical field [0001] The invention relates to a control method for a photovoltaic grid-connected system, in particular to a three-loop control method for a single-stage photovoltaic grid-connected inverter system. Background technique [0002] Photovoltaic grid-connected power generation systems are divided into single-stage and multi-stage systems according to the topological level. The front-end photovoltaic panels of the single-stage grid-connected power generation system are directly connected to the grid through the inverter, which has the advantages of simple topology, low cost, and high efficiency, but its control strategy is complicated, and it needs to be connected to the grid on the control chip of the inverter Current control, taking into account maximum power tracking control and system stability. [0003] The main circuit of single-stage photovoltaic grid-connected system is composed of solar photovoltaic array, DC bus capacitor, inverter bridge, filter induc...

AI Technical Summary

Problems solved by technology

The control method and its device aim at the disadvantages of long tracking time and poor dynamic response in the traditional control method using fixed-step disturbance observation, and the disadvantages of bus voltage instability in the traditional double-loop current control method , use the control method of variable step size disturbance observation to speed up the power tracking time and improve the dynamic response, and use the three-ring to realize the inverter grid connection function to stabilize the bus voltage and make the system work more reliable

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