Novel active power filter filtering circuit

Abstract

The invention discloses a novel active power filter filtering circuit. The novel active power filter filtering circuit is characterized in that influence of resistance and capacitance parameter selection on an APF current inner loop is analyzed through a bode diagram thoroughly; a novel RC filtering circuit is designed; specific to the time delay problem, a current control method based on a prediction control strategy is proposed; the sampled power grid voltage and inverter output current are subjected to prediction in advance, so that influence to the system caused by time delay can be reduced, and robustness of the system is reinforced; by adopting the novel active power filter filtering circuit, influence of cut-off frequency selection on the current inner loop can be lowered effectively, a high suppression effect on higher harmonic can be achieved, and high system stability is achieved; and by virtue of the current control method based on the prediction control strategy, the stability of the sampled power grid voltage and inverter output current is improved highly, influence to the system caused by time delay can be reduced, and robustness of the system is reinforced.

Description

technical field [0001] The invention belongs to the field of current predictive control, in particular to a novel active power filter circuit based on current predictive control. Background technique [0002] In recent years, with more and more nonlinear loads connected to the power grid, the harmonic pollution of the power system has become increasingly serious, and the flood of harmonics has affected the safe and economical operation of the power grid. In order to effectively suppress harmonic pollution in the power grid and improve power quality, various passive power filters (PPF) and active power filters (APF) have received high attention. APF counteracts the dynamic harmonic current and reactive current generated by the load by injecting compensation current into the grid, and is widely used in various industrial and civil occasions. [0003] In terms of improving APF compensation accuracy, the following two problems must be solved: 1) In the actual work of APF, the c...

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Problems solved by technology

When the cut-off frequency is not selected properly, resonance peaks will be introduced, and high-order harmonics near the resonant frequency will be generated while APF output compensates sub-harmonics, which will affect the compensation performance of APF. When the content of high-order harmonics is too high, it will cause The entire control system is unstable

[0004] 2) The delay of the controller will also affect the compensation performance of the APF device to a large extent

The design of the current inner loop is the key to improving the delay. The APF current inner loop control methods are concentrated into the following types: Repeated control adds the deviation of the previous control cycle and the deviation of this cycle to the controlled object for control, improving The current tracking accuracy and the stability of the system are improved, but there is still the delay problem of control period lag; proportional-resonant (PR) control can be understood as a generalized integral of a sinusoidal signal, which has infinite gain at a specific frequency, so that the system The steady-state tracking error of the frequency is theoretically zero. This method can realize selective harmonic compensation, but corresponding to the harmonics of different frequencies, different resonance controllers need to be used, and the amount of calculation is still large; it is suitable for inverters. Robust predictive control, using the Romberg observer to predict the output current at the k+1th moment at the kth moment, and through its root locus diagram in the z domain, the influence of the delay on the system stability is analyzed in detail, but In actual engineering applications, it is slightly complicated

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