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.

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• Engineering & Computer Science (AREA)
• Power Engineering (AREA)
• Inverter Devices (AREA)

Applications Claiming Priority (2)

Publications (1)

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ID=89662388

Family Applications (1)

Country Status (2)

Families Citing this family (16)

Family Cites Families (3)

• 2011
  • 2011-08-03 WO PCT/KR2011/005697 patent/WO2012105737A1/en active Application Filing
  • 2011-08-03 EP EP11857825.1A patent/EP2671311A1/de not_active Withdrawn

Non-Patent Citations (1)

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