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A control method for cascaded photovoltaic solid-state transformers

A solid-state transformer and control method technology, which is applied in photovoltaic power generation, control/regulation systems, instruments, etc., can solve the problem of four times the power frequency envelope wave of the cascade photovoltaic solid-state transformer, which increases the cost and complexity of the system. Reduce system reliability and other issues

Active Publication Date: 2020-06-02
HEFEI UNIV OF TECH
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Problems solved by technology

[0008] 1) At present, the main research is the double power frequency ripple suppression of the DC side capacitor voltage of the single-phase inverter, and additional auxiliary devices need to be added, which will increase the cost and complexity of the system and reduce the reliability of the system sex
[0009] 2), the existing literature rarely mentions the quadruple power frequency envelope wave problem of cascaded photovoltaic solid-state transformers

Method used

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  • A control method for cascaded photovoltaic solid-state transformers
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  • A control method for cascaded photovoltaic solid-state transformers

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[0082] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention will be further clearly and completely described below in conjunction with the accompanying drawings and embodiments.

[0083] figure 1 It is the topology of the main circuit of the cascaded photovoltaic solid-state transformer implemented in the present invention, which is composed of phase A, phase B and phase C; phase A contains N modules, phase B contains N modules, phase C contains N modules, and phase A , B-phase and C-phase module structures are exactly the same, and N is a positive integer greater than 1; each module is composed of a two-level full-bridge LLC converter connected in series with an H-bridge converter, the H-bridge converter The AC output terminal is connected in parallel with a bypass switch. The bypass switch is a relay with a controllable switch state; the AC output terminals of all modules in phase A, phase B and phase ...

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Abstract

The invention discloses a control method of a cascade photovoltaic solid-state transformer and is to solve the problem of envelope ripples of quadruple power frequency of resonance current of a preceding-stage two-level full-bridge LLC converter after compensation of third harmonic voltage for the system. The method mainly comprises the following steps: controlling the average value of DC capacitor voltage of all H-bridge converters and obtaining an active current instruction value; controlling grid current and calculating third harmonic voltage and compensating the third harmonic voltage forthe system; controlling output voltage of the two-level full-bridge LLC converter and suppressing resonance current quadruple power frequency envelope ripples; and controlling input bus voltage of a Boost converter to realize maximum power point tracking control of a preceding-stage photovoltaic array. Compared with the prior art, the method can realize suppression of quadruple power frequency envelope ripples of the preceding-stage two-level full-bridge LLC converter without adding any hardware device, thereby improving system performance.

Description

technical field [0001] The invention belongs to the photovoltaic power generation technology in the field of electrical engineering, and in particular relates to a method for suppressing the quadruple power frequency envelope ripple of the resonant current of a two-level full-bridge LLC converter in a cascaded photovoltaic solid-state transformer. Background technique [0002] Due to the limitations of semiconductor switching devices, it is practically challenging and uneconomical to increase the power rating of conventional centralized inverters above 1WM. One of the methods can use a three-phase solid-state transformer topology based on cascaded H-bridge multilevel converters. The modular structure can use common low-voltage components on the market to expand the entire system to higher voltage and power levels, making it possible to connect the entire power station to the medium-voltage grid with only a single converter. Since the high-frequency transformer in the isolat...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H02M3/335H02M1/14H02J3/01H02J3/38
CPCH02J3/01H02J3/385H02M1/14H02M3/33576Y02E10/56Y02E40/40
Inventor 张兴赵涛王明达毛旺王付胜李飞
Owner HEFEI UNIV OF TECH
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