Method for carrying out model prediction control on grid-side converter of photovoltaic power generation system under unbalanced voltage

Abstract

The invention discloses a method for carrying out model prediction control on a grid-side converter of a photovoltaic power generation system under unbalanced voltage. According to the technical scheme, the method is characterized by including the first step of carrying out analytic calculation to obtain reference current of the AC side of the converter according to voltage of a sampling grid, delayed signals and given initial power, the second step of obtaining prediction current through a prediction model under the action of voltage vectors, the third step of selecting the voltage vector, which minimizes the absolute value of the difference between the current reference value and the current prediction value, as the optimal voltage vector through a value function, and the fourth step of selecting a switch position signal corresponding to the optimal voltage vector as a switching signal for controlling a power device. Under the condition of network voltage unbalance, it is guaranteed that DC bus voltage is stable and grid-side current is sinusoidal through the control of balance of the power of the two sides of the converter. The whole process is based on a two-phase static coordinate frame, and rotational coordinate conversion is avoided. Moreover, the control method does not include the positive and negative sequence decomposition and phase locking steps, the control structure is simple, and the calculated amount is small.

Description

[0001] technical field [0002] The invention relates to a model predictive control method for a grid-side converter of a photovoltaic power generation system under unbalanced voltage, and belongs to the field of power electronic power conversion device control. Background technique [0003] Compared with the traditional vector control based on PI controller, model predictive control has the advantages of simple structure, fast dynamic response, no need to adjust controller parameters, etc. It is an advanced control method with broad application prospects. The model predictive control method is applied to the operation control of the converter in the photovoltaic power generation system, which can obtain accurate and fast current regulation effect. However, when the model predictive control method is used for control, it is assumed that the three-phase grid voltage is balanced. When the grid voltage is unbalanced, the DC bus voltage will generate double-frequency pulsation ...

AI Technical Summary

Problems solved by technology

The existing solutions are all unbalanced control methods for vector control strategies, which cannot be applied to model predictive control methods, and require the process of rotating coordinate transformation or performing positive and negative sequence decomposition operations on control variables. The control system is relatively complex, and the amount of calculation bigger

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