EP2671311A1 - Method and circuits for common mode current depression in 3 phase transformerless pv inverter - Google Patents

Method and circuits for common mode current depression in 3 phase transformerless pv inverter

Info

Publication number
EP2671311A1
EP2671311A1 EP11857825.1A EP11857825A EP2671311A1 EP 2671311 A1 EP2671311 A1 EP 2671311A1 EP 11857825 A EP11857825 A EP 11857825A EP 2671311 A1 EP2671311 A1 EP 2671311A1
Authority
EP
European Patent Office
Prior art keywords
terminal
connects
inverter
boost
pwm
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP11857825.1A
Other languages
German (de)
French (fr)
Inventor
Ceu Pail
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
HD Hyundai Heavy Industries Co Ltd
Original Assignee
Hyundai Heavy Industries Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Hyundai Heavy Industries Co Ltd filed Critical Hyundai Heavy Industries Co Ltd
Publication of EP2671311A1 publication Critical patent/EP2671311A1/en
Withdrawn legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/12—Arrangements for reducing harmonics from ac input or output
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/381—Dispersed generators
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/32—Means for protecting converters other than automatic disconnection
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
    • H02J2300/20—The dispersed energy generation being of renewable origin
    • H02J2300/22—The renewable source being solar energy
    • H02J2300/24—The renewable source being solar energy of photovoltaic origin
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/50—Photovoltaic [PV] energy
    • Y02E10/56—Power conversion systems, e.g. maximum power point trackers

Definitions

  • the subject of the invention is a method and circuits for common mode current depression in 3 phase transformerless PV inverter.
  • the invention is connected to the RCD (residual current detection) too.
  • the photovoltaic cells are organized into strings.
  • the strings are paralleled and connected to an inverter DC input. It is also well known that the strings have stray capacitance to the earth potential.
  • the common mode voltage generates common mode current through the stray capacitance of the strings and this current is sensed by RCD circuits. If the sensed common mode current exceeds the set protection level in that case the inverter will be separated from utility grid.
  • the efficiency can be increased in 3 phase PWM inverters by means of a 3rd harmonic component of the PWM reference signal. This makes possible that to feed the energy into the utility grid at less DC input voltage of the inverter. This solution reduces the losses of the switching devices of the inverter.
  • the applied additional 3rd harmonic reference signal cases 3rd harmonic common mode voltage what generate common mode current through the RCD circuit.
  • the advantage of our invention is that the solution does not cancel the additional 3rd harmonic PWM reference signal application, but limits its value in some special cases as thin film solar cells or special installation like very near cells to the ground. This way our invention can ensure a higher efficiency than other products.
  • the invention advantage is that the method and circuits are applicable with 2 and more level invetres and the controller can be built up in d,q or x,y reference frame too.
  • the DC energy is provided by A string which output 1is connected to B well known boost terminal 1and A string terminal 2 is connected B boost terminal 2.
  • the increased voltage from B boost output terminal 3 and 4 is connected to the well-known D inverter terminal 1 and 2.
  • D inverter R,S,T outputs go through the E RCD ring and connected to the F utility grid terminal R,S,T.
  • a string terminal 1 connected to C1 sray capacitance while terminal 2 is connected to C2 stray capacitance while C1 nad C2 stray capacitance other terminal are connected to the ground (earth) potential.
  • E RCD terminal 1 connects to H filter and G comparator terminal 1, while H filter terminal 2 connects to I modifier terminal 1.
  • I modifier terminal 2 connects J controller terminal 2 while J controller terminal 1 connects to K PWM terminal 3.
  • K PWM terminal 1 connects to B boost terminal 5 while K PWM terminal 2 connects to D inverter terminal 3.
  • B boost increases the DC voltage if necessary and forwards the DC voltage to the D inverter input.
  • the D inverter and the including sinusoidal filter converts the DC energy with the well-known PWM mode and feeds it through the E RCD into the AC utility grid.
  • E RCD measures the common mode current and gives the measured value to G comparator and H filter.
  • H filter forwards the 3rd harmonics only to the I modifier.
  • I modifier adjusts its input signal and limits its output signal and to the K controller.
  • K controller provides the right DC voltage and adjust the PWM base and 3rd harmonics reference value and optimize the additional 3rd harmonics PWM reference value .
  • K PWM unit provides the gating of the B boost and D inverter.
  • Figure 1 is a basis of one possible version of the invention.
  • Figure 2 is an operation of one possible version described in figure 1.

Abstract

The DC energy is provided by A string which output 1is connected to B well known boost terminal 1and A string terminal 2 is connected B boost terminal 2. The increased voltage from B boost output terminal 3 and 4 is connected to the well-known D inverter terminal 1 and 2. D inverter R,S,T outputs go through the E RCD ring and connected to the F utility grid terminal R,S,T. A string terminal 1 connected to C1 stray capacitance while terminal 2 is connected to C2 stray capacitance while C1 nad C2 stray capacitance other terminal are connected to the ground (earth) potential. E RCD terminal 1 connects to H filter and G comparator terminal 1, while H filter terminal 2 connects to I modifier terminal 1. I modifier terminal 2 connects J controller terminal 2 while J controller terminal 1 connects to K PWM terminal 3. K PWM terminal 1 connects to B boost terminal 5 while K PWM terminal 2 connects to D inverter terminal 3.

Description

    METHOD AND CIRCUITS FOR COMMON MODE CURRENT DEPRESSION IN 3 PHASE TRANSFORMERLESS PV INVERTER
  • The subject of the invention is a method and circuits for common mode current depression in 3 phase transformerless PV inverter. The invention is connected to the RCD (residual current detection) too.
    •
  • Well known that the photovoltaic cells are organized into strings. The strings are paralleled and connected to an inverter DC input. It is also well known that the strings have stray capacitance to the earth potential.
  • Furthermore it is well known that the DC energy of the strings is converted into the alternating voltage utility grid. The national and international standards require RCD protection what aim is the life protection.
  • It is also well known that the common mode voltage generates common mode current through the stray capacitance of the strings and this current is sensed by RCD circuits. If the sensed common mode current exceeds the set protection level in that case the inverter will be separated from utility grid.
  • It is well known that there is a sharp competition between the manufacturer on the renewable market and the efficiency is one of the most important technical parameter. The efficiency can be increased in 3 phase PWM inverters by means of a 3rd harmonic component of the PWM reference signal. This makes possible that to feed the energy into the utility grid at less DC input voltage of the inverter. This solution reduces the losses of the switching devices of the inverter. On the other hand the applied additional 3rd harmonic reference signal cases 3rd harmonic common mode voltage what generate common mode current through the RCD circuit.
  • State of art
  • The manufacturers give a limit in the manual related to the maximum stray capacitance of strings to the earth potential. One of the leader company, the SMA applied the limitation of stray capacitance and solved the trouble this way.
  • Our invention’s essence is that the common mode 3rd harmonic current through the RCD is controlled by the applied additional 3rd harmonics of the PWM reference signal and keeps it below a certain value. This solution automatically provides the optimal 3rd harmonics PWM reference signal in applications with higher or lower stray capacitance of strings. It means that not necessary to limit the stray capacitance value of the strings and the possible best efficiency is achieved independently from the type of installation and type of solar cell.
  • The advantage of our invention is that the solution does not cancel the additional 3rd harmonic PWM reference signal application, but limits its value in some special cases as thin film solar cells or special installation like very near cells to the ground. This way our invention can ensure a higher efficiency than other products.
  • Further important advantage is the safe RCD protection operation because the control system can make a certain margin from the default residual current level.
  • The invention advantage is that the method and circuits are applicable with 2 and more level invetres and the controller can be built up in d,q or x,y reference frame too.
  • In the following part the invention is introduced in one possible version on the basis of figure 1.
  • Static and dynamic description:
  • The DC energy is provided by A string which output 1is connected to B well known boost terminal 1and A string terminal 2 is connected B boost terminal 2. The increased voltage from B boost output terminal 3 and 4 is connected to the well-known D inverter terminal 1 and 2. D inverter R,S,T outputs go through the E RCD ring and connected to the F utility grid terminal R,S,T. A string terminal 1 connected to C1 sray capacitance while terminal 2 is connected to C2 stray capacitance while C1 nad C2 stray capacitance other terminal are connected to the ground (earth) potential.
  • E RCD terminal 1 connects to H filter and G comparator terminal 1, while H filter terminal 2 connects to I modifier terminal 1. I modifier terminal 2 connects J controller terminal 2 while J controller terminal 1 connects to K PWM terminal 3. K PWM terminal 1 connects to B boost terminal 5 while K PWM terminal 2 connects to D inverter terminal 3.
  • Operation:
  • A string DC terminal voltage and its current supplies B boost. B boost increases the DC voltage if necessary and forwards the DC voltage to the D inverter input. The D inverter and the including sinusoidal filter converts the DC energy with the well-known PWM mode and feeds it through the E RCD into the AC utility grid. E RCD measures the common mode current and gives the measured value to G comparator and H filter. H filter forwards the 3rd harmonics only to the I modifier. I modifier adjusts its input signal and limits its output signal and to the K controller. K controller provides the right DC voltage and adjust the PWM base and 3rd harmonics reference value and optimize the additional 3rd harmonics PWM reference value . K PWM unit provides the gating of the B boost and D inverter.
    •
  • Figure 1 is a basis of one possible version of the the invention.
  • Figure 2 is an operation of one possible version described in figure 1.
  • List of reference symbols
  • A string
  • B boost
  • C1 stray capacitance
  • C2 stray capacitance
  • D inverter
  • E RCD residual current detection
  • F utility grid
  • G comparator
  • H filter
  • I modifier
  • J controller
  • K PWM = pulse width modulation
    •

Claims (10)

  1. Advanced method and circuits for depression of common mode currents caused stray capacitances in 3 phase transformerless PV inverters, in case the DC energy is provided by 1 or more strings (A) which terminal 1 connected to the well-known boost (B) terminal 1 while string (A) terminal 2 is connected to boost (B) terminal 2 and boost (B) terminal 3 and 4 respectively supply inverter (D) terminal 1 and 2 and inverter (D) outputs R,S,T go through the RCD ring (E) and connected to the utility grid (F) terminal R,S,T furthermore string (A) terminal 1 connects to stray capacitance (C1) while terminal 2 is connected to stray capacitance (C2) while stray capacitances (C1) and (C2) other terminals are connected to the ground (earth) potential while RCD (E) terminal 1 connects to filter (H) and comparator (G) terminal 1, while filter (H) terminal 2 connects to modifier (I) terminal 1 and modifier (I) terminal 2 connects controller (J) terminal 2 while controller (J) terminal 1 connects to PWM (K) terminal 3 while PWM (K) terminal 1 connects to boost (B) terminal 5 while PWM (K) terminal 2 connects to inverter (D) terminal 3.
  2. A method and circuits according to claim 1, characterized that not only R,S,T but the neutral wire of the utility grid (F) led through RCD (E).
  3. A method and circuits according to claim 1, characterized that the PWM (K) provides for the inverter (D) shifted PWM signal with 120± 90 electric degrees.
  4. A method and circuits according to claim 1, characterized that the inverter (D) modulation signal PWM (K) is asynchronous to the utility grid (F).
  5. A method and circuits according to claim 1, characterized that one MPPT is applied.
  6. A method and circuits according to claim 1, characterized that where more boost (B) and more MPPT are applied.
  7. A method and circuits according to claim 1, characterized that there is no boost (B) is applied.
  8. A method and circuits according to claim 1, characterized that not only R,S,T but the neutral wire of the utility grid (F) led through RCD (E).
  9. A method and circuits according to claim 1, characterized that the circuits contains EMC filters and at string (A) side and utility grid (F) side.
  10. A method and circuits according to claim 1, characterized that the stray capacitance (C1, C2) common mode current are measured not in RCD (E) but it is derived in other way for instance the boost (B) input 1and 2 are led through a current transducer.
EP11857825.1A 2011-02-04 2011-08-03 Method and circuits for common mode current depression in 3 phase transformerless pv inverter Withdrawn EP2671311A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
HUP1102617 2011-02-04
PCT/KR2011/005697 WO2012105737A1 (en) 2011-02-04 2011-08-03 Method and circuits for common mode current depression in 3 phase transformerless pv inverter

Publications (1)

Publication Number Publication Date
EP2671311A1 true EP2671311A1 (en) 2013-12-11

Family

ID=89662388

Family Applications (1)

Application Number Title Priority Date Filing Date
EP11857825.1A Withdrawn EP2671311A1 (en) 2011-02-04 2011-08-03 Method and circuits for common mode current depression in 3 phase transformerless pv inverter

Country Status (2)

Country Link
EP (1) EP2671311A1 (en)
WO (1) WO2012105737A1 (en)

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US11460488B2 (en) 2017-08-14 2022-10-04 Koolbridge Solar, Inc. AC electrical power measurements
US11901810B2 (en) 2011-05-08 2024-02-13 Koolbridge Solar, Inc. Adaptive electrical power distribution panel
US8937822B2 (en) 2011-05-08 2015-01-20 Paul Wilkinson Dent Solar energy conversion and utilization system
US8982593B2 (en) 2012-04-27 2015-03-17 Rockwell Automation Technologies, Inc. Cascaded H-Bridge (CHB) inverter level shift PWM with rotation
US9425705B2 (en) 2012-08-13 2016-08-23 Rockwell Automation Technologies, Inc. Method and apparatus for bypassing cascaded H-bridge (CHB) power cells and power sub cell for multilevel inverter
US9007787B2 (en) 2012-08-13 2015-04-14 Rockwell Automation Technologies, Inc. Method and apparatus for bypassing Cascaded H-Bridge (CHB) power cells and power sub cell for multilevel inverter
US9240731B2 (en) 2013-03-18 2016-01-19 Rockwell Automation Technologies, Inc. Power cell bypass method and apparatus for multilevel inverter
US9083230B2 (en) 2013-06-20 2015-07-14 Rockwell Automation Technologies, Inc. Multilevel voltage source converters and systems
US9520800B2 (en) 2014-01-09 2016-12-13 Rockwell Automation Technologies, Inc. Multilevel converter systems and methods with reduced common mode voltage
US9325252B2 (en) 2014-01-13 2016-04-26 Rockwell Automation Technologies, Inc. Multilevel converter systems and sinusoidal pulse width modulation methods
US9559541B2 (en) 2015-01-15 2017-01-31 Rockwell Automation Technologies, Inc. Modular multilevel converter and charging circuit therefor
US9748862B2 (en) 2015-05-13 2017-08-29 Rockwell Automation Technologies, Inc. Sparse matrix multilevel actively clamped power converter
US9812990B1 (en) 2016-09-26 2017-11-07 Rockwell Automation Technologies, Inc. Spare on demand power cells for modular multilevel power converter
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US11342878B1 (en) 2021-04-09 2022-05-24 Rockwell Automation Technologies, Inc. Regenerative medium voltage drive (Cascaded H Bridge) with reduced number of sensors

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Also Published As

Publication number Publication date
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