CN114865618A - Reactive power optimization and safety lifting device for photovoltaic inverter - Google Patents
Reactive power optimization and safety lifting device for photovoltaic inverter Download PDFInfo
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- CN114865618A CN114865618A CN202210387140.3A CN202210387140A CN114865618A CN 114865618 A CN114865618 A CN 114865618A CN 202210387140 A CN202210387140 A CN 202210387140A CN 114865618 A CN114865618 A CN 114865618A
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- 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
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
- H02H3/02—Details
- H02H3/05—Details with means for increasing reliability, e.g. redundancy arrangements
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
- H02H3/26—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to difference between voltages or between currents; responsive to phase angle between voltages or between currents
- H02H3/32—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to difference between voltages or between currents; responsive to phase angle between voltages or between currents involving comparison of the voltage or current values at corresponding points in different conductors of a single system, e.g. of currents in go and return conductors
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/10—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers
- H02H7/12—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers for static converters or rectifiers
- H02H7/122—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers for static converters or rectifiers for inverters, i.e. dc/ac converters
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/26—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H9/00—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection
- H02H9/04—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection responsive to excess voltage
- H02H9/045—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection responsive to excess voltage adapted to a particular application and not provided for elsewhere
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- 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
- H02J13/00—Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network
- H02J13/00006—Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network characterised by information or instructions transport means between the monitoring, controlling or managing units and monitored, controlled or operated power network element or electrical equipment
- H02J13/00022—Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network characterised by information or instructions transport means between the monitoring, controlling or managing units and monitored, controlled or operated power network element or electrical equipment using wireless data transmission
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- 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
- H02J13/00—Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network
- H02J13/00032—Systems characterised by the controlled or operated power network elements or equipment, the power network elements or equipment not otherwise provided for
- H02J13/00036—Systems characterised by the controlled or operated power network elements or equipment, the power network elements or equipment not otherwise provided for the elements or equipment being or involving switches, relays or circuit breakers
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- 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
- H02J13/00—Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network
- H02J13/00032—Systems characterised by the controlled or operated power network elements or equipment, the power network elements or equipment not otherwise provided for
- H02J13/00036—Systems characterised by the controlled or operated power network elements or equipment, the power network elements or equipment not otherwise provided for the elements or equipment being or involving switches, relays or circuit breakers
- H02J13/0004—Systems characterised by the controlled or operated power network elements or equipment, the power network elements or equipment not otherwise provided for the elements or equipment being or involving switches, relays or circuit breakers involved in a protection system
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- 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
- H02J3/01—Arrangements for reducing harmonics or ripples
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- 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
- H02J3/12—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load
- H02J3/16—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load by adjustment of reactive power
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- 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
- H02J3/18—Arrangements for adjusting, eliminating or compensating reactive power in networks
- H02J3/1807—Arrangements for adjusting, eliminating or compensating reactive power in networks using series compensators
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- 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
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- 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
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- 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
- H02J3/388—Islanding, i.e. disconnection of local power supply from the network
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- 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
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- 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
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- 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
- Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
- Y02E40/30—Reactive power compensation
Abstract
The invention provides a reactive power optimization and safety lifting device for a photovoltaic inverter, which comprises a composite protection circuit, a reactive power optimization circuit and a circuit-breaking trigger circuit, wherein the composite protection circuit is a resonant circuit, the composite protection circuit is connected between a zero phase in an input end of the circuit-breaking trigger circuit and a fire phase in an output end of the circuit-breaking trigger circuit, a first end of the reactive power optimization circuit is connected to a power grid, a second end of the reactive power optimization circuit is connected with an input end of the circuit-breaking trigger circuit, and an output end of the circuit-breaking trigger circuit is connected with the photovoltaic inverter. The invention realizes the auxiliary protection of the island with extremely low cost by arranging the resonant circuit and avoids the hidden trouble of the error tripping of the leakage circuit breaker. Meanwhile, overvoltage protection and reactive power absorption during operation of the photovoltaic inverter are achieved.
Description
Technical Field
The invention belongs to the field of photovoltaic power generation auxiliary equipment, and particularly relates to a reactive power optimization and safety lifting device for a photovoltaic inverter.
Background
With the development of power electronic technology, more and more small-sized micro-grids containing distributed power supplies are put into application, wherein the small-sized micro-grids represented by photovoltaic systems have the problems of unreliable island protection, easy overvoltage due to reactive disturbance and the like after being connected into a power grid in large quantity, and the photovoltaic systems contain a large number of electronic converters, so that the photovoltaic systems have special requirements on fault protection due to sensitivity to disturbance of power supply systems. If only the protection of the electronic converter is relied on, the method sometimes has obvious limitations in terms of island effect protection, overvoltage protection and the like.
In addition, after a photovoltaic system serving as a distributed power supply is connected into a microgrid, due to the fluctuation of transmission power and the characteristics of distributed loads, the voltage at each load node of a transmission line of the microgrid is higher or lower, so that the voltage deviation exceeds the technical index of safe operation, and after large-scale distributed photovoltaic access, the problem of static voltage deviation exists at local nodes of a power distribution network. The distribution network, especially the low-voltage network, is sensitive to voltage changes, and when the photovoltaic power generation output peak is in the early spring or in autumn in the afternoon of a clear day, the voltage of the low-voltage distribution network is seriously higher due to low consumption on the load side, so that great challenges are brought to the electric energy quality and the power supply safety. Meanwhile, in the aspect of relay protection, a large number of tail end distributed photovoltaics send fault currents to the same-level or higher-level power grid, and the problem of power direction is not considered in the existing distribution network protection, so that the protection misoperation or operation rejection probability is improved.
From the above, there is a need for an external circuit to implement reactive power optimization and auxiliary safety protection of a photovoltaic inverter in a simple manner.
Disclosure of Invention
In order to solve the defects and shortcomings in the prior art, the invention provides a photovoltaic inverter reactive power optimization and safety lifting device which comprises a composite protection circuit, a reactive power optimization circuit and a circuit-breaking trigger circuit, wherein the composite protection circuit is a resonance circuit, the composite protection circuit is connected between a zero phase in an input end of the circuit-breaking trigger circuit and a fire phase in an output end of the circuit-breaking trigger circuit, a first end of the reactive power optimization circuit is connected into a power grid, a second end of the reactive power optimization circuit is connected with an input end of the circuit-breaking trigger circuit, and an output end of the circuit-breaking trigger circuit is connected with a photovoltaic inverter.
Optionally, the composite protection circuit includes a capacitor C, a capacitor C1, an inductor L, a resistor R1, a resistor R2, a diode D, a thyristor SCR, and a high voltage trigger diode SIDAC;
the capacitor C and the inductor L are connected in parallel to form a resonant circuit, a first end of the resonant circuit is connected with a medium-temperature phase at the output end of the open circuit trigger circuit, a second end of the resonant circuit is connected with a first end of the resistor R1, a second end of the resistor R1 is connected with a negative electrode of the diode D and a zero phase at the input end of the open circuit trigger circuit, an anode of the diode D is connected with a first end of the capacitor C1, and a second end of the capacitor C1 is connected with a second end of the resonant circuit;
the first end of the resistor R2 is connected with the first end of the resonant circuit, the second end of the resistor R2 is connected with the cathode of the thyristor SCR, the anode of the thyristor SCR is connected with the anode of the diode D, the gate of the thyristor SCR is connected with the second end of the oscillating circuit, and the resistor R2 is connected with the zero phase in the input end of the circuit breaking trigger circuit after being connected with the high-voltage trigger diode SIDAC in series.
Optionally, the resonant frequency of the resonant tank is between 52Hz and 58 Hz.
Optionally, the reactive power optimization circuit includes a reactor and a capacitor, the reactor is connected in series to the zero phase at the input end of the open circuit trigger circuit, and the capacitor is connected in parallel between the fire phase and the zero phase at the input end of the open circuit trigger circuit.
Optionally, the open circuit trigger circuit includes a circuit breaker, a zero sequence induction coil, a contactor and a trigger tube;
the zero sequence induction coil is connected in parallel at two ends of the circuit breaker, a contact of the contactor is connected in series on a zero phase of an output end of the open circuit trigger circuit, and a coil of the contactor is connected in parallel at two ends of the zero sequence induction coil after being connected in series with the trigger tube.
Optionally, a release is connected to an operating mechanism of the circuit breaker, and the release includes a local release and a GPRS release.
The technical scheme provided by the invention has the beneficial effects that:
(1) the invention realizes the island auxiliary protection with extremely low cost, utilizes the resonant circuit to directly drive the leakage protection release to trip under the frequency deviation by arranging the resonant circuit, has the characteristics of simple structure and high reliability, and can be realized under the condition of not using any chip for control.
(2) The resonance frequency point of the resonance circuit is set and adjusted, so that the circuit is slightly inductive to 50Hz power frequency, a small inductive compensation current is arranged in the zero sequence induction coil of the leakage circuit breaker, the capacitive leakage current can be counteracted, and the hidden trouble of the false tripping of the leakage circuit breaker is avoided.
(3) The invention can realize the overvoltage protection at a very high level only by one high-voltage trigger diode and a resistor, the trigger diode is used as a mature passive device with very high reliability, and compared with the existing overvoltage protection device which adopts a large number of active detection circuit designs, the reliability of the device is greatly improved.
(4) Through the arrangement of the series reactor, the reactor can suppress the problem of higher harmonic interference of the photovoltaic inverter while absorbing reactive power, reactive power absorption during the operation of the photovoltaic inverter is realized, and an effective solution is provided for the problem of overhigh terminal voltage on the basis of not changing the setting of the photovoltaic inverter.
(5) According to the invention, the absolute value of the voltage at the tail end of the line and the voltage fluctuation rate are acquired by the trigger tube, whether the system has a fault or not is judged, and the system rapidly acts on the tripping and reclosing of the inverter, so that the relay protection of the existing distribution network does not need to consider the influence of the photovoltaic inverter.
(6) Through setting up the function that GPRS release realized the remote control circuit breaker, when needs manual work overhauls the electric wire netting, can jump off the circuit breaker through GPRS wireless remote control, further promote the security, take precautions against the bodily injury that photovoltaic back-off led to.
Drawings
In order to more clearly illustrate the technical solution of the present invention, the drawings required to be used in the description of the embodiments will be briefly introduced below, and it is apparent that the drawings in the description below are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained based on these drawings without creative efforts.
Fig. 1 is a circuit diagram of a photovoltaic inverter reactive power optimization and safety boosting device according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The terms "first," "second," "third," "fourth," and the like in the description and in the claims, as well as in the drawings, if any, are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used is interchangeable under appropriate circumstances such that the embodiments of the invention described herein are capable of operation in sequences other than those illustrated or described herein.
It should be understood that, in various embodiments of the present invention, the sequence numbers of the processes do not mean the execution sequence, and the execution sequence of the processes should be determined by the functions and the internal logic of the processes, and should not constitute any limitation on the implementation process of the embodiments of the present invention.
It should be understood that in the present application, "comprising" and "having" and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.
It should be understood that, in the present invention, "a plurality" means two or more. "and/or" is merely an association describing an associated object, meaning that three relationships may exist, for example, and/or B, may mean: a exists alone, A and B exist simultaneously, and B exists alone. The character "/" generally indicates that the former and latter associated objects are in an "or" relationship. "comprises A, B and C" and "comprises A, B, C" means that A, B, C all comprise, "comprises A, B or C" means comprise one of A, B, C, "comprises A, B and/or C" means comprise any 1 or any 2 or 3 of A, B, C.
It should be understood that in the present invention, "B corresponding to a", "a corresponds to B", or "B corresponds to a" means that B is associated with a, and B can be determined from a. Determining B from a does not mean determining B from a alone, but may be determined from a and/or other information. And the matching of A and B means that the similarity of A and B is greater than or equal to a preset threshold value.
As used herein, "if" may be interpreted as "at … …" or "when … …" or "in response to a determination" or "in response to a detection", depending on the context.
The technical solution of the present invention will be described in detail below with specific examples. The following several specific embodiments may be combined with each other, and details of the same or similar concepts or processes may not be repeated in some embodiments.
Example (b):
as shown in fig. 1, the present embodiment provides a photovoltaic inverter reactive power optimization and safety promotion device, which includes a composite protection circuit 10, a reactive power optimization circuit 20, and a trip trigger circuit 30, where the composite protection circuit 10 is a resonant circuit, the composite protection circuit 10 is connected between a zero phase N at an input end of the trip trigger circuit 30 and a fire phase L at an output end of the trip trigger circuit, a first end of the reactive power optimization circuit 20 is connected to a power grid, a second end of the reactive power optimization circuit 20 is connected to an input end of the trip trigger circuit 30, and an output end of the trip trigger circuit 30 is connected to the photovoltaic inverter.
In the embodiment, by the circuit structure, various protection effects such as island effect protection, overvoltage protection, electric leakage protection and the like can be realized. The structure and function of the reactive power optimization and safety boosting device will be described in detail with reference to the circuit shown in fig. 1.
The compound protection circuit 10 comprises a capacitor C, a capacitor C1, an inductor L, a resistor R1, a resistor R2, a diode D, a thyristor SCR and a high-voltage trigger diode SIDAC;
the capacitor C and the inductor L are connected in parallel to form a resonant loop, a first end of the resonant loop is connected with a fire phase L in the output end of the open circuit trigger circuit, a second end of the resonant loop is connected with a first end of the resistor R1, a second end of the resistor R1 is connected with a cathode of the diode D and a zero phase N in the input end of the open circuit trigger circuit 30, an anode of the diode D is connected with a first end of the capacitor C1, and a second end of the capacitor C1 is connected with a second end of the resonant loop;
the first end of the resistor R2 is connected with the first end of the resonant circuit, the second end of the resistor R2 is connected with the cathode of the thyristor SCR, the anode of the thyristor SCR is connected with the anode of the diode D, the gate of the thyristor SCR is connected with the second end of the oscillating circuit, and the resistor R2 is connected with the high-voltage trigger diode SIDAC in series and then is connected with the zero phase N in the input end of the circuit breaking trigger circuit.
In this embodiment, the resonant frequency of the resonant tank is between 52Hz-58 Hz.
The compound protection circuit 10 has the comprehensive protection functions of island auxiliary protection, breaker anti-error tripping protection and overvoltage protection. The method specifically comprises the following steps:
the island effect protection is indispensable to a tail end power grid containing a distributed power supply, and a plurality of new energy inversion units comprehensively apply active and passive island effect protection schemes, so that a good effect is achieved. However, for a low-voltage and small-capacity microgrid system, such as a household photovoltaic system and the like, because the island protection detection of an inverter is simple, the problems of slow shutdown and the like after external power grid faults occur frequently, and because the shutdown of the microgrid system is only stopped by a converter, the isolation of mechanical disconnection points of switching equipment cannot be realized, so that certain hidden dangers still exist. In the embodiment, the frequency detection is carried out through the composite protection circuit, and the auxiliary protection of the island effect is realized by means of the residual current protector, so that the island protection of the low-voltage small-capacity microgrid system is more reliable.
The voltage at the two ends of the resistor R1 changes along with the frequency change, but when the loop Q value is larger, the voltage at the two ends of the resistor R1 can be greatly increased by small deviation of the frequency, the voltage at the two ends of the resistor R1 is charged to the integrating capacitor C1 through the diode D, when the voltage at the two ends of the resistor R1 is higher than the gate trigger voltage of the thyristor SCR, the thyristor can be triggered to be conducted by charging of a plurality of cycles, so that a zero-sequence transformer of the residual current protector senses unbalanced current to act tripping, and the island effect protection effect of frequency deviation is achieved. However, when the system frequency is normal, the admittance of the parallel resonant circuit is very small, the voltage at the two ends of the resistor R1 is far lower than the gate trigger voltage of the thyristor, the thyristor cannot be triggered and conducted by mistake, when the power grid has transient disturbance, such as switching on and off of a switch, and the like, because of the transient process of the LC element, the two ends of the resistor R1 may have higher voltage, and then because of the energy storage buffering effect of the C1, the thyristor cannot be triggered by mistake due to the transient voltage of one or two cycles.
Because the power electronic equipment adopts anti-interference earth capacitors in a large quantity, the capacitors accumulate subsequent capacitive currents, the leakage circuit breaker can be easily tripped by mistake, the resonance frequency point of the resonance circuit can be set and adjusted, the 50Hz power frequency is slightly inductive, a small inductive compensation current is arranged in a zero sequence induction coil of the leakage circuit breaker, the capacitive leakage current can be counteracted, and the hidden trouble that the leakage circuit breaker is tripped by mistake is avoided.
The high-voltage trigger diode SIDAC is a nonlinear two-terminal device with negative resistance characteristics, when the voltage applied to two ends is lower than a starting voltage, the resistance value of the diode is extremely large, and only microampere-level leakage current is generated at the moment; when the voltage applied to the two ends exceeds the opening voltage UBO, the diode is quickly converted into a low-resistance conduction state, the on-state voltage UT of the diode is very low and is only about 1.5V, so that larger current can pass through the diode instantly. The SIDAC is in a self-locking state once it is turned on, and is turned off only when the current flowing through itself is interrupted or less than a holding current, and the on mode of the SIDAC is close to the voltage dependent resistor and the off mode of the SIDAC is close to the thyristor. The present embodiment utilizes the special current-voltage characteristics to design the composite protection circuit 10 for realizing the overvoltage detection function. The response speed of the SIDAC element reaches nanosecond level, so that the detection speed of overvoltage abnormity can be improved.
In this embodiment, it is only necessary to set the value of UBO, that is, the operation threshold voltage of the high-voltage trigger diode SIDAC to be slightly higher than the peak value of the trip setting voltage, so as to ensure that the SIDAC diode is turned on immediately after the overvoltage abnormality occurs, and by setting the value of the current-limiting resistor R2, the current after the SIDAC is turned on is not less than the operation current of the residual current protector. For example, when the circuit breaker is required to trip at a grid voltage of 250V, a K350-type SIDAC diode may be used, and when the grid voltage rises to 250V, the peak voltage is about 353V and exceeds a conduction threshold of the K350 diode 350V, and in order to ensure reliable operation of the residual current protector, if an operating current I is set to 50mA, R2 is set to 2.5K Ω.
In the present embodiment, the reactive power optimization circuit 20 includes a reactor 21 and a capacitor 22, the reactor 21 is connected in series to the zero phase N at the input end of the trip trigger circuit 30, and the capacitor 22 is connected in parallel between the fire phase L and the zero phase N at the input end of the trip trigger circuit 30.
By connecting the reactor in series and the capacitor in parallel, the adverse effect of distributed photovoltaic on the voltage reactive power of the power grid is improved. By arranging the series reactor, reactive absorption of the photovoltaic inverter during operation is realized, and an effective way is provided for solving the problem of high terminal voltage on the basis of not changing the setting of the photovoltaic inverter. When the photovoltaic inverter operates, the larger the output current is, the lower the reactive output of the parallel capacitor is due to the reduction of voltage, and meanwhile, the more the reactor absorbs the reactive power, the lower the power factor of the photovoltaic inverter is, so that the effect of adjusting the voltage at the tail end of a power grid is achieved, and the reactor also absorbs the reactive power and simultaneously suppresses the problem of higher harmonic interference of the photovoltaic inverter.
In the present embodiment, the breaking triggering circuit 30 includes a breaker 31, a zero sequence induction coil 32, a contactor 33, and a triggering tube 34;
the zero sequence induction coil is connected in parallel at two ends of the breaker 31, a contact of the contactor 33 is connected in series on the zero phase N of the output end of the open circuit trigger circuit 30, and the coil of the contactor 33 is connected in parallel at two ends of the zero sequence induction coil after being connected in series with the trigger tube 34.
The protection misoperation or the action rejection caused by the reverse transmission of the fault current of the photovoltaic system is avoided, the output of the photovoltaic inverter is instantly disconnected during the system disturbance, and the output of the inverter is quickly recovered after the voltage is recovered, so that the relay protection correct action and the recovery stability after the system fault are ensured. In this embodiment, the breakdown voltage of the trigger tube 34 is set to about 80% of the voltage peak value of a normal alternating current power grid, once the voltage drops below 80% due to a fault, the trigger tube is immediately cut off, the contactor 33 is released, and the rapid switch-on is performed after the voltage of the power grid is recovered, so that the rapid action and the tripping and reclosing of the inverter are realized, and the relay protection of the existing distribution network does not need to consider the influence of the photovoltaic inverter.
In this embodiment, a release is connected to an operating mechanism of the circuit breaker, and the release includes a local release 35 and a GPRS release 36. Therefore, in the circuit breaking trigger circuit 30, a tripping mechanism controlled by GPRS is further arranged, when the power grid needs to be manually overhauled, the breaker can be tripped out through GPRS wireless remote control, the safety is further improved, and personal injury caused by photovoltaic reverse transmission is prevented.
The sequence numbers in the above embodiments are merely for description, and do not represent the sequence of the assembly or the use of the components.
The above description is only exemplary of the present invention and should not be taken as limiting the invention, as any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (6)
1. The reactive power optimization and safety lifting device for the photovoltaic inverter is characterized by comprising a composite protection circuit, a reactive power optimization circuit and a circuit-breaking trigger circuit, wherein the composite protection circuit is a resonant circuit, the composite protection circuit is connected between a zero phase in an input end of the circuit-breaking trigger circuit and a fire phase in an output end of the circuit-breaking trigger circuit, a first end of the reactive power optimization circuit is connected to a power grid, a second end of the reactive power optimization circuit is connected to an input end of the circuit-breaking trigger circuit, and an output end of the circuit-breaking trigger circuit is connected to the photovoltaic inverter.
2. The photovoltaic inverter reactive power optimization and safety promotion device according to claim 1, wherein the composite protection circuit comprises a capacitor C, a capacitor C1, an inductor L, a resistor R1, a resistor R2, a diode D, a thyristor SCR and a high voltage trigger diode SIDAC;
the capacitor C and the inductor L are connected in parallel to form a resonant circuit, a first end of the resonant circuit is connected with a fire phase in an output end of the open circuit trigger circuit, a second end of the resonant circuit is connected with a first end of the resistor R1, a second end of the resistor R1 is connected with a negative electrode of the diode D and a zero phase in an input end of the open circuit trigger circuit, an anode of the diode D is connected with a first end of the capacitor C1, and a second end of the capacitor C1 is connected with a second end of the resonant circuit;
the first end of the resistor R2 is connected with the first end of the resonant circuit, the second end of the resistor R2 is connected with the cathode of the thyristor SCR, the anode of the thyristor SCR is connected with the anode of the diode D, the gate of the thyristor SCR is connected with the second end of the oscillating circuit, and the resistor R2 is connected with the zero phase in the input end of the circuit breaking trigger circuit after being connected with the high-voltage trigger diode SIDAC in series.
3. The pv inverter var optimization and safety enhancement device according to claim 1, wherein the resonant tank has a resonant frequency between 52Hz and 58 Hz.
4. The photovoltaic inverter reactive power optimization and safety lifting device according to claim 1, wherein the reactive power optimization circuit comprises a reactor and a capacitor, the reactor is connected in series with a zero phase at the input end of the circuit break triggering circuit, and the capacitor is connected in parallel between a fire phase and a zero phase at the input end of the circuit break triggering circuit.
5. The photovoltaic inverter reactive power optimization and safety lifting device according to claim 1, wherein the open circuit trigger circuit comprises a circuit breaker, a zero sequence induction coil, a contactor and a trigger tube;
the zero sequence induction coil is connected in parallel at two ends of the circuit breaker, a contact of the contactor is connected in series on a zero phase of an output end of the open circuit trigger circuit, and a coil of the contactor is connected in parallel at two ends of the zero sequence induction coil after being connected in series with the trigger tube.
6. The photovoltaic inverter reactive power optimization and safety lifting device according to claim 5, wherein a release is connected to an operating mechanism of the circuit breaker, and the release comprises a local release and a GPRS release.
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| CN117424465A (en) * | 2023-12-18 | 2024-01-19 | 深圳市三瑞电源有限公司 | Photovoltaic inverter assembly with open-circuit voltage protection function and photovoltaic inverter |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN117424465A (en) * | 2023-12-18 | 2024-01-19 | 深圳市三瑞电源有限公司 | Photovoltaic inverter assembly with open-circuit voltage protection function and photovoltaic inverter |
| CN117424465B (en) * | 2023-12-18 | 2024-03-26 | 深圳市三瑞电源有限公司 | Photovoltaic inverter assembly with open-circuit voltage protection function and photovoltaic inverter |
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