Square wave compensation control method for operating range of enlarged cascaded H-bridge photovoltaic inverter

A photovoltaic inverter, compensation control technology, applied in photovoltaic power generation, single-network parallel feeding arrangement, output power conversion device, etc., can solve the ability to reduce system power generation, large capacitor voltage fluctuations, and system imbalance Weakness and other problems, to achieve the effect of expanding the operating range and small fluctuations in capacitor voltage

Active Publication Date: 2018-02-23
HEFEI UNIV OF TECH
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Problems solved by technology

[0008] 1) When the output power of each H-bridge unit is seriously unbalanced, although the reactive power compensation control strategy can ensure that all H-bridge units are not modulated, the power factor of the inverter is low and cannot meet the grid-connected standard
[0009] 2) Although the hybrid modulation strategy can expand the operating r...

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  • Square wave compensation control method for operating range of enlarged cascaded H-bridge photovoltaic inverter
  • Square wave compensation control method for operating range of enlarged cascaded H-bridge photovoltaic inverter
  • Square wave compensation control method for operating range of enlarged cascaded H-bridge photovoltaic inverter

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[0057] 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.

[0058] figure 1 The main circuit topology of the single-phase cascaded H-bridge photovoltaic grid-connected inverter implemented for the present invention includes N identical H-bridge units, and each H-bridge unit is composed of four fully-controlled switching devices. Each H-bridge front end is connected in parallel with an electrolytic capacitor C i (i=1,2,…,N), each electrolytic capacitor is connected to a photovoltaic cell PV i (i=1, 2, . . . , N) connection. After the AC side outputs of all H-bridges are connected in series, the filter inductor L 1 and L 2 connected to the grid, where R 1 and R 2 Respectively filter inductance L 1 and L 2 equivalent resistance. V in the figure dci and I PVi (i=1,2,...,N) respec...

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Abstract

The invention discloses a square wave compensation control method for the operating range of an enlarged cascaded H-bridge photovoltaic inverter and belongs to the field of photovoltaic power generation. The method mainly comprises the following steps of (1) independently controlling the direct-current-side capacitor voltage of each H-bridge unit and obtaining the active power instruction value ofa grid-connected current; (2) realizing the static-error-free control of the grid-connected current, and simultaneously generating the total modulating voltage of the inverter and the modulation degrees of all H-bridge units; (3) according to the square wave compensation strategy, calculating the modulation wave of each H-bridge module. Compared with published documents in the prior art, the normal operation of the power factor of an inverter unit is ensured when the input power of the cascaded H-bridge photovoltaic grid-connected inverter is not balanced seriously. Meanwhile, the fluctuation of the direct-current-side capacitor voltage of the enlarged cascaded H-bridge photovoltaic inverter is ensured to be small.

Description

technical field [0001] The invention belongs to photovoltaic power generation technology in the field of electrical engineering, and in particular relates to a square wave compensation control method for expanding the operating range of cascaded H-bridge photovoltaic inverters. Background technique [0002] Compared with traditional inverters, cascaded H-bridge multilevel inverters have the advantages of low grid current harmonic content, low switching frequency, small filter size and easy modularization, etc., so it has attracted the attention of many scholars. In addition, the DC side of each H-bridge unit of the cascaded H-bridge multi-level inverter can be independently powered by a photovoltaic cell, making its independent maximum power point tracking (MPPT—Maximum Power Point Tracking) control possible, so the level The H-bridge multilevel topology is especially suitable for photovoltaic grid-connected inverters. [0003] Although each H-bridge unit of the cascaded H-...

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Application Information

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IPC IPC(8): H02M7/483H02J3/38
CPCH02J3/385H02M7/483H02M1/007Y02E10/56
Inventor 张兴赵涛毛旺王明达王付胜王佳宁
Owner HEFEI UNIV OF TECH
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