Inverter system as well as control device and method thereof

Abstract

The invention discloses a control device of an inverter system, which is applied to the inverter system. The inverter system comprises a switching group, and a CMC and a voltage compensation device which are connected through the switching group, wherein the control device comprises a connection unit, a CMC control unit, a switching control unit and a compensation control unit; the connection unit is used for connecting the output end of the inverter system to a power grid; the CMC control unit is used for starting up a conversion circuit in the CMC and controlling the CMC to output sine alternating voltage V0; the switching control unit is used for controlling the switching group to be switched off when a difference value between an effective value of the V0 and an effective value of pre-set sine alternating voltage Vsin is in a pre-set range, and the CMC is connected into the power grid through the voltage compensation device; and the compensation control unit is used for starting up the voltage compensation device and adjusting output voltage Vcom of the voltage compensation device so that the sum of the Vcom and voltage Vgrid of the power grid is equal to the Vsin. Visibly, the voltage compensation device can be used for compensating distorted voltage of the power grid and the influences on the CMC by the distortion of the power grid are eliminated, so that the inverter system has a relatively good output waveform and a relatively rapid responding speed. The invention further discloses the inverter system and a control method thereof.

Description

technical field [0001] The invention relates to the technical field of inverter system control, in particular to an inverter system and its control device and method. Background technique [0002] Cascaded multilevel converters (CascadedMultilevelConverters, CMC) can be applied to a variety of workplaces, among which photovoltaic power generation systems are a common application, please refer to figure 1 and figure 2 ,in, figure 1 It is a schematic diagram of the principle of an inverter system integrated into the power grid provided by the present invention, figure 2 A conversion circuit provided by the present invention is a structural schematic diagram of a DCAC module. The cascaded multilevel converter CMC includes n sequentially connected DCAC modules and one general filter. [0003] When the cascaded multilevel converter topology is used in a photovoltaic power generation system, in order to ensure the overall cost and efficiency of the photovoltaic power generati...

AI Technical Summary

Problems solved by technology

However, after the cascaded multilevel converter adopts a single-stage inverter sub-module, on the one hand, the MPPT (Maximum Power Point Tracking, maximum power point tracking) algorithm, control strategy and modulation method of the photovoltaic power generation system often need to be coupled together for processing , which is equivalent to the indirect control of the grid-connected current; and the information interaction between the sub-modules of the cascaded multi-level converter will also increase the coordinated control time of the system, which will greatly increase the dynamic response time of the CMC system, which is not conducive to photovoltaic Control of power generation system to deal with grid distortion or flicker

On the other hand, even if grid voltage feed-forward is introduced to the system in order to cope with grid distortion or flicker, since the input voltage and modulation voltage of each inverter sub-module are different when CMC is used in a photovoltaic power generation system, The effect of feedback will also be greatly reduced

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