Positive sequence component-based three-phase inverter control method and device

Abstract

The invention discloses a positive sequence component-based three-phase inverter control method and a device, so as to improve the power supply quality of the inverter when unbalanced fault happens to the grid. The method of the invention comprises steps: a three-phase voltage positive sequence component is extracted and converted into a per unit value, computation is carried out between the per unit value and a power reference value, a d-axis current reference value and a q-axis current reference value are obtained, output current of the inverter undergoes Park transformation and then is compared with the current reference value to obtain a difference value, and after proportion integral control and Park inverse transformation, a three-phase modulation wave waveform is formed. The device of the invention is provided with a Park transformation and Park inverse transformation unit, a sinusoidal pulse width modulation unit, a positive sequence component extracting unit, a per unit value unit and a constant power control unit. Compared with the prior art, bad influences of negative sequence voltage on output features of the inverter in the case of unbalanced fault are eliminated, the control method is simplified, the response speed is improved, and the power supply quality of the inverter in the case of unbalanced fault is improved.

Description

technical field [0001] The invention relates to a control method of an inverter, in particular to a control method of a three-phase inverter. Background technique [0002] As distributed power is more and more widely integrated into the grid, the control method of the inverter of grid-connected distributed power has been paid more and more attention by people. The three-phase inverter control method in the prior art adopts double-loop proportional-integral PI control. The outer loop controls the output characteristics such as the DC side voltage, the AC side voltage, or the output power of the inverter according to actual needs and provides a current reference signal to the inner loop. The inner-loop controller mainly performs fine adjustments to improve the power quality output by the inverter, and generally has a faster dynamic response. Among the various control objectives of the outer loop, the control strategy (method) to maintain the stability of the active and reacti...

AI Technical Summary

Problems solved by technology

The disadvantage of this method is that the output power of the inverter still has double frequency fluctuations, and the difference between the rated power and output power will not be stable, resulting in poor tracking effect of the power outer loop PI controller

In order to overcome the defect that the PI regulator cannot effectively track the non-DC flow, a proportional resonant PR regulator is used

The difference between the PR regulator and the PI regulator is that it can track sinusoidal signals, thus simplifying the control link (Journal of Electrotechnical Society, December 2010, Control of three-phase grid-connected inverter under asymmetric grid voltage conditions, Zhang Wei, Wang Hongsheng, Ren Yuan, Hu Jiabing, He Yikang, pp. 103-110), its disadvantages are that the parameters of the PR regulator are complex and inconvenient to adjust, and in general, the output current of the inverter cannot track the reference current value smoothly and without error. Worse than PI control

Both of the above two methods have the problems of power sampling value fluctuation, complex control links and long adjustment time.

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