Grid-connected inverter for low-frequency current ripple output restraining of fuel cell and control device

Abstract

The invention discloses a grid-connected inverter for low-frequency current ripple output restraining of a fuel cell and a control device. The grid-connected inverter comprises the fuel cell FC, a boosting converter, a full bridge inverter and an LCL filter. The control device comprises a voltage sensor, a current sensor and a DSP digital controller. The boosting converter comprises an inverse-current-preventing diode, an input filtering capacitor Cin, a filtering inductor LB, an electric MOSFET and an output capacitor CDC. The full bridge inverter comprises four electric MOSFETs. The LCL filter comprises a capacitor C1 and two inductors L1 and L2. The DSP digital controller comprises a proportioner, a phase-locked loop, a subtracter, a PI adjuster, a multiplying unit, a summator, a signal generator, a comparer and a phase inverter. By establishing the boosting converter, energy decoupling on an input side and an output side is achieved, the fact that currents on the input side do not contain low-frequency ripples is guaranteed, the manufacturing cost of the grid-connected inverter is lowered, power conversion efficiency is improved, and an electric energy converting device suitable for fuel battery power generation is achieved.

Description

technical field [0001] The invention relates to a grid-connected inverter capable of suppressing low-frequency current ripple output by a fuel cell and a control device thereof, and belongs to the technical field of power electronic converters and control thereof. Background technique [0002] In order to deal with various adverse effects of distributed power grid-connected power generation on the power grid, and to maximize the use of the advantages of distributed power, the concept of AC micro-grid has been proposed in recent years. In order to ensure the stable operation of the AC microgrid, it is necessary to use different forms of distributed power sources to form complementary advantages, such as photovoltaic cells, wind turbines, batteries and fuel cells. Since the operation of the fuel cell is not affected by environmental changes, the role of the fuel cell in the stable operation of the microgrid is particularly obvious. In the AC microgrid, the energy generated by...

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Problems solved by technology

[0005] Purpose of the invention: In view of the shortcomings of the existing fuel cell grid-connected inverters, which have many conversion stages and complicated control, the present invention multiplexes the power devices of the boost converter and the full-bridge inverter, reducing the number of power conversion stages, Improve the conversion efficiency; control the boost converter at a fixed duty cycle, and ensure that the inductor current works in a discontinuous mode, without using complex control methods to ensure that the output current of the fuel cell does not contain low-order ripples; The bridge inverter adopts unipolar modulation mode, which can effectively reduce the size and weight of the filter, and can ensure high quality of grid-connected current

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