Looking for breakthrough ideas for innovation challenges? Try Patsnap Eureka!

Non-isolated intermediate-point clamping photovoltaic grid connected inverter and modulation method thereof

A non-isolation and inverter technology, applied in the direction of photovoltaic power generation, AC network circuit, single-network parallel feeding arrangement, etc., can solve the problems of increasing cost, volume and loss, affecting reliability, and not being able to completely cut off the leakage current loop , to achieve the ability to suppress leakage current and solve the effect of leakage current

Active Publication Date: 2019-07-12
ZHENGZHOU UNIV
View PDF3 Cites 4 Cited by
  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

(1) The power frequency isolated inverter can realize the electrical isolation between the photovoltaic side and the grid side to suppress the leakage current, but it increases the problems of cost, volume and loss, and there are many deficiencies in industrial applications
(2) High-frequency isolated inverters reduce system volume and cost, but the power level is divided into several levels, which affects reliability and does not significantly improve the overall efficiency of the system
However, due to the existence of switch junction capacitance, the leakage current loop cannot be completely cut off, causing the ground voltage at the midpoint of the inverter output bridge arm to be in a suspended and uncertain state during the grid-connected current continuous flow stage, and the common-mode voltage cannot be guaranteed to be constant, thus Generates common mode leakage current
The generation of common-mode leakage current will cause problems such as grid-connected current distortion and electromagnetic interference, especially posing a threat to personal safety

Method used

the structure of the environmentally friendly knitted fabric provided by the present invention; figure 2 Flow chart of the yarn wrapping machine for environmentally friendly knitted fabrics and storage devices; image 3 Is the parameter map of the yarn covering machine
View more

Image

Smart Image Click on the blue labels to locate them in the text.
Viewing Examples
Smart Image
  • Non-isolated intermediate-point clamping photovoltaic grid connected inverter and modulation method thereof
  • Non-isolated intermediate-point clamping photovoltaic grid connected inverter and modulation method thereof
  • Non-isolated intermediate-point clamping photovoltaic grid connected inverter and modulation method thereof

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0039] as attached figure 1 As shown, a non-isolated mid-point clamped photovoltaic grid-connected inverter is set between the photovoltaic array output unit and the AC grid, which includes a capacitor string 1, a clamp unit 3, a freewheeling unit 5, and a bridge arm I2 and bridge arm II4; the bridge arm I2 is respectively connected in parallel with the capacitor string 1, the bridge arm II4 and the photovoltaic array output unit; the positive end of the clamping unit 3 is respectively connected to the freewheeling unit 5 connected to the bridge arm II4, the negative terminal of the clamping unit 3 is connected to the midpoint of the capacitor string 1; one end of the freewheeling unit 5 is connected to the positive terminal of the clamping unit 3, and the other One end is connected to the midpoint of the bridge arm I2; point a of the bridge arm I2 and point b of the bridge arm II4 form the AC voltage output terminal u of the non-isolated midpoint clamp photovoltaic grid-conne...

Embodiment 2

[0042] This embodiment provides a specific implementation of the non-isolated neutral point clamped photovoltaic grid-connected inverter, as shown in the attached figure 2 As shown, the capacitor string 1 is composed of equivalent DC input voltage dividing capacitors C connected in series dc1 and C dc2 Composed, the freewheeling unit 5 includes a switching tube S 5 and switch tube S 6 , the clamping unit 3 is a switching tube S 7 , the bridge arm I2 includes forward-series switching tubes S 1 and switch tube S 2 , the bridge arm II 4 includes forward-series switching tubes S 3 , switch tube S 5 and switch tube S 4 , each of the switching tubes is connected in reverse parallel with a freewheeling diode; wherein, the switching tube S of the clamping unit 7 The positive end of the bridge arm II and the switching tube S 3 connected to the negative terminal of the clamp unit, the switching tube S 7 The negative end of the capacitor string is connected to the midpoint; th...

Embodiment 3

[0065] In this embodiment, the non-isolated neutral point clamped photovoltaic grid-connected inverter and its modulation method are verified by simulation.

[0066] Setting: DC input voltage is 400V, AC grid voltage is 380V / 50Hz, output filter inductance L 1 and filter inductor L 2 is 4mH, the DC bus capacitance is 2200μF, the distributed capacitance is 120nF, the switching frequency is 15kHz, and the switching junction capacitance is 1.5nF.

[0067] as attached Figure 13 As shown, this embodiment gives the bridge arm output voltage u of the non-isolated neutral point clamped photovoltaic grid-connected inverter ab The simulation waveform of the bridge arm midpoint (a, b) to the DC bus negative terminal N point voltage u aN and u bN The simulation waveform of the simulation waveform, and the simulation waveform of the common-mode voltage, the common-mode voltage remains constant throughout the switching cycle, u cm Both are 200V.

[0068] as attached Figure 14 As sho...

the structure of the environmentally friendly knitted fabric provided by the present invention; figure 2 Flow chart of the yarn wrapping machine for environmentally friendly knitted fabrics and storage devices; image 3 Is the parameter map of the yarn covering machine
Login to View More

PUM

No PUM Login to View More

Abstract

The invention provides a non-isolated intermediate-point clamping photovoltaic grid connected inverter and a modulation method thereof. The non-isolated intermediate-point clamping photovoltaic grid connected inverter is arranged between a photovoltaic array output unit and an AC power grid, and comprises a capacitor bank, a clamping unit, a freewheeling unit and first and second legs; the first leg is in parallel connection with the capacitor bank, second leg and photovoltaic array output unit; the positive end of the clamping unit is connected with the freewheeling unit and the second leg, and the negative end of the clamping unit is connected to the intermediate point of the capacitor bank; one end of the freewheeling unit is connected with the positive end of the clamping unit, and theother end of the freewheeling unit is connected with the intermediate point of the first leg; and a point a of the first leg and a point b of the second leg form an AC voltage output end of the non-isolated intermediate-point clamping photovoltaic grid connected inverter. Thus, common-mode voltage oscillation caused by a switch junction capacitance parameter can be eliminated, and common-mode grounding leakage current caused by the switch junction capacitor is inhibited effectively.

Description

technical field [0001] The invention relates to the field of electric energy conversion and new energy distributed grid-connected power generation, and specifically relates to a non-isolated neutral point clamp photovoltaic grid-connected inverter and a modulation method thereof. Background technique [0002] Distributed photovoltaic power generation has the advantages of decentralized power generation, local use, avoiding investment and loss in power transmission and distribution, and no need to occupy additional land, and has been valued by countries all over the world. According to the function, photovoltaic inverters are divided into off-grid inverters and grid-connected inverters; the output of off-grid inverters is voltage, which is mainly used for energy storage systems and places that cannot be reached by the grid in remote areas; grid-connected inverters The output of the inverter is current, which is mainly used in the grid-connected system to obtain income or self...

Claims

the structure of the environmentally friendly knitted fabric provided by the present invention; figure 2 Flow chart of the yarn wrapping machine for environmentally friendly knitted fabrics and storage devices; image 3 Is the parameter map of the yarn covering machine
Login to View More

Application Information

Patent Timeline
no application Login to View More
Patent Type & Authority Applications(China)
IPC IPC(8): H02M7/487H02M7/5387H02J3/38
CPCH02J3/383H02M7/487H02M7/53871Y02E10/56
Inventor 王要强梁海艳秦明程子霞孔斌王军凡绍桂王昌龙
Owner ZHENGZHOU UNIV
Who we serve
  • R&D Engineer
  • R&D Manager
  • IP Professional
Why Patsnap Eureka
  • Industry Leading Data Capabilities
  • Powerful AI technology
  • Patent DNA Extraction
Social media
Patsnap Eureka Blog
Learn More
PatSnap group products

Browse by: Latest US Patents, China's latest patents, Technical Efficacy Thesaurus, Application Domain, Technology Topic, Popular Technical Reports.

© 2024 PatSnap. All rights reserved.Legal|Privacy policy|Modern Slavery Act Transparency Statement|Sitemap|About US| Contact US: help@patsnap.com