CN114825894A - Wave-by-wave current limiting control method and device for Heric inverter circuit and inverter - Google Patents
Wave-by-wave current limiting control method and device for Heric inverter circuit and inverter Download PDFInfo
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- CN114825894A CN114825894A CN202210710885.9A CN202210710885A CN114825894A CN 114825894 A CN114825894 A CN 114825894A CN 202210710885 A CN202210710885 A CN 202210710885A CN 114825894 A CN114825894 A CN 114825894A
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- 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
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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
- 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
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
- H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
- H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/53—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M7/537—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
- H02M7/5387—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration
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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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Abstract
The invention provides a wave-by-wave current-limiting control method and device for a Heric inverter circuit and an inverter, and relates to the technical field of photovoltaic inverters. The invention relates to a wave-by-wave current limiting control method for a Heric inverter circuit, wherein the Heric inverter circuit comprises an H-shaped inverter bridge and a follow current path, the follow current path is used for providing a follow current channel in a follow current stage so as to completely close the H-shaped inverter bridge, and the wave-by-wave current limiting control method comprises the following steps: checking an overcurrent signal, and acquiring the current direction and the voltage direction of the inversion output when the overcurrent signal is generated; and determining the work attribute of the Heric inverter circuit according to the current direction and the voltage direction, and blocking the H-shaped inverter bridge or the follow current path according to the work attribute. According to the technical scheme, the stress of the high voltage of the bus and the stress of the switching tube device are effectively reduced, meanwhile, the connection time of the photovoltaic panel and the power grid is reduced, and the instantaneous leakage current is reduced.
Description
Technical Field
The invention relates to the technical field of photovoltaic inverters, in particular to a wave-by-wave current limiting control method and device for a Heric inverter circuit and an inverter.
Background
The Heric inverter circuit consists of two direct current buses, an H-shaped inverter bridge and a follow current path, and as shown in fig. 2, the H-shaped inverter bridge consists of four switching tubes from V1 to V4, the follow current path consists of the switching tubes from V5 to V6, and the follow current paths from V5 and V6 are used for providing a follow current path in the follow current stage so that the V1 to V4 tubes can be completely closed to isolate the connection between the photovoltaic module and the power grid.
In order to protect the inverter, current-limiting protection is usually required to be implemented on output current, common protection methods include wave-by-wave current-limiting protection and the like, and by taking the current wave-by-wave current-limiting method as an example, once overcurrent occurs, all switching tubes of an inverter circuit are blocked, that is, if current limiting occurs in any power frequency section, a zero-level follow current loop is cut off, current must follow current through V1-V4 at the moment, so that the stress problem of bus high voltage and switching tube devices is caused, and the problem that leakage current exceeds the standard possibly caused by long-term connection of a power grid and a photovoltaic panel, so that leakage current protection is triggered, the inverter is shut down, and the service life of the inverter is influenced by the problems.
Disclosure of Invention
The invention solves the problem that the service life of an inverter is influenced by stress and instantaneous leakage current existing in the conventional wave-by-wave current limiting scheme.
In order to solve the above problems, the present invention provides a wave-by-wave current limiting control method for a Heric inverter circuit, where the Heric inverter circuit includes an H-type inverter bridge and a freewheel path, and the freewheel path is used to provide a freewheel channel at a freewheel stage to completely close the H-type inverter bridge, and the wave-by-wave current limiting control method includes: checking an overcurrent signal, and acquiring the current direction and the voltage direction of the inversion output when the overcurrent signal is generated; and determining the work attribute of the Heric inverter circuit according to the current direction and the voltage direction, and blocking the H-shaped inverter bridge or the follow current path according to the work attribute.
Optionally, the checking the overcurrent signal, and when the overcurrent signal is generated, the obtaining the current direction and the voltage direction of the inverter output includes: detecting output current, and generating the overcurrent signal when the output current is greater than a preset value; and acquiring the current direction through a current sensor, and acquiring the voltage direction through a voltage sensor.
Optionally, the determining a work attribute of the Heric inverter circuit according to the current direction and the voltage direction includes: when the current direction is the same as the voltage direction, judging that the work is in an active power section; and when the current direction is different from the voltage direction, judging that the work is in a reactive power section.
Optionally, said blocking said H-type inverter bridge or said free-wheeling path according to said work-done attribute comprises: when the work is in the active power section, blocking a driving signal of the H-shaped inverter bridge; and when the work is in the reactive power section, blocking the driving signal of the follow current path.
Optionally, the wave-by-wave current limiting control method for the Heric inverter circuit further includes: and when the next PWM period comes, the over-current signal is detected again, if the over-current signal disappears, the PWM wave generation is opened again, an interruption event is eliminated, and if the over-current signal does not disappear, the H-shaped inverter bridge or the follow current path is blocked continuously according to the acting attribute.
According to the wave-by-wave current-limiting control method for the Heric inverter circuit, when an overcurrent signal is generated, the current direction and the voltage direction of inverter output are obtained, the acting attribute of the Heric inverter circuit is determined according to the current direction and the voltage direction, and the H-shaped inverter bridge or the follow current path is blocked according to the acting attribute, so that the stress of a bus high voltage and a switch tube device is effectively reduced, meanwhile, the connection time of a photovoltaic panel and a power grid is reduced, and the instantaneous leakage current is reduced. And the problem that the inductive current continuously increases when the reactive output is over-current under the traditional local wave-sealing strategy is solved. In addition, when photovoltaic inverter's life was effectively improved, can provide more stable power for electric automobile's equipment such as electric pile that fills.
The invention also provides a wave-by-wave current-limiting control device for the Heric inverter circuit, which applies the wave-by-wave current-limiting control method for the Heric inverter circuit, wherein the Heric inverter circuit comprises an H-shaped inverter bridge and a follow current channel, the follow current channel is used for providing a follow current channel in the follow current stage to completely close the H-shaped inverter bridge, and the wave-by-wave current-limiting control device comprises an overcurrent detection circuit, a reactive power judgment circuit and a blocking circuit; the overcurrent detection circuit is used for detecting output current and generating an overcurrent signal when the output current is greater than a preset value; the active and reactive power judging circuit is used for determining the work property of the Heric inverter circuit according to the current direction and the voltage direction; the blocking circuit is used for blocking the H-shaped inverter bridge or the follow current path according to the acting attribute.
Optionally, the over-current detection circuit is configured to output a low level to generate the over-current signal when the output current is greater than a preset value.
Optionally, the active and reactive power determining circuit includes a comparator and an exclusive or gate, the comparator includes a current comparator and a voltage comparator, the current comparator is configured to output a high level when the current direction is in a negative half cycle, the voltage comparator is configured to output a high level when the voltage direction is in a positive half cycle, and the exclusive or gate is configured to take an output of the current comparator and an output of the voltage comparator as inputs, output a high level when the work is in an active power section, and output a low level when the work is in a reactive power section.
Optionally, the blocking circuit is configured to block a driving signal of the H-type inverter bridge or a driving signal of the freewheel path according to the work attribute.
Compared with the prior art, the advantages of the wave-by-wave current-limiting control device for the Heric inverter circuit and the wave-by-wave current-limiting control method for the Heric inverter circuit are the same, and are not repeated herein.
The invention also provides an inverter which comprises the wave-by-wave current-limiting control device for the Heric inverter circuit. Compared with the prior art, the advantages of the inverter and the wave-by-wave current limiting control device for the Heric inverter circuit are the same, and are not described again.
Drawings
Fig. 1 is a schematic flow chart of a wave-by-wave current limiting control method for a Heric inverter circuit according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a Heric inverter circuit according to an embodiment of the present invention;
FIG. 3 is a timing logic diagram of the wave-by-wave current limiting of the active power section according to the embodiment of the present invention;
FIG. 4 is a schematic diagram of an over-current detection circuit according to an embodiment of the present invention;
FIG. 5 is a schematic diagram of a reactive power determining circuit according to an embodiment of the present invention;
FIG. 6 is a block circuit diagram of the V5 tube and the V6 tube according to the present invention;
FIG. 7 is a block circuit diagram of the V1-V4 tube according to the embodiment of the present invention;
FIG. 8 is a flowchart of a process of an embodiment of the present invention.
Detailed Description
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below.
As shown in fig. 1, an embodiment of the present invention provides a wave-by-wave current limiting control method for a Heric inverter circuit, where the Heric inverter circuit includes an H-type inverter bridge and a freewheel path, and the freewheel path is used to provide a freewheel channel in a freewheel phase to completely close the H-type inverter bridge, where the wave-by-wave current limiting control method includes: checking an overcurrent signal, and acquiring the current direction and the voltage direction of the inversion output when the overcurrent signal is generated; and determining the work attribute of the Heric inverter circuit according to the current direction and the voltage direction, and blocking the H-shaped inverter bridge or the follow current path according to the work attribute.
Specifically, in this embodiment, when an overcurrent signal is generated, a current direction and a voltage direction of the inverter output are obtained, and a working attribute of the Heric inverter circuit is determined according to the current direction and the voltage direction, for example, the current and voltage are in the same direction, an active power section is used to block the H-type inverter bridge, and if the current and voltage are in the opposite direction, a reactive power section is used to block the follow current path, so that partial blocking of the switching tube is realized, the stress of the high voltage of the bus and the switching tube device is effectively reduced, the connection time of the photovoltaic panel and the power grid is reduced, and the instantaneous leakage current is reduced. For the switch circuit formed by the MOSFET, the switching action of the follow current tube is kept, so that the part of active follow current is kept, and the conduction loss in the follow current stage is improved. Taking a photovoltaic inverter as an example, the photovoltaic inverter converts direct current provided by the solar module into alternating current for civil use or industrial use, and can be used for charging electric automobiles and the like. When photovoltaic inverter's life was effectively improved, can provide more stable power for equipment such as electric automobile's the electric pile that fills.
Referring to fig. 2 (a left line of C1 is connected to a dc power supply), taking a herc inverter circuit as an example, the herc inverter circuit is composed of two dc buses, an H-type inverter bridge composed of four switching tubes V1-V4, and a follow current auxiliary tube composed of switching tubes V5 and V6, and the V5 and V6 function to provide a follow current channel in a follow current stage to isolate the connection between the photovoltaic module and the grid.
The existing wave-by-wave current-limiting global wave-sealing control method can synchronously block all switch tubes of an inverter circuit after overcurrent occurs, namely, a zero-level follow current loop can be cut off if overcurrent occurs. At this point, current must freewheel through the body diode from V1 to V4, causing bus high voltage and switching device stress problems. Meanwhile, when current flows through the body diode, the power grid is connected with the photovoltaic panel for a long time, short-time leakage current exceeding the standard possibly is caused, leakage current protection is caused, and therefore the inverter is shut down. And the conduction loss generated when the body diode freewheels is large, and large loss is generated. The existing local wave-sealing mode does not consider the problem of increase of inductive current caused by opening of an auxiliary tube under the reactive condition.
In order to solve the problems of stress of a bus high voltage and a switching tube device generated in a full wave-sealing mode adopted for wave-by-wave current limiting, excessive transient leakage current and high conduction loss which are possibly generated, and meet the requirement of wave-by-wave current limiting control under a reactive condition, a control strategy of a non-full-sealing mode is designed, V5 and V6 are kept to work at a useful power current-flowing stage as far as possible, and the connection between a power grid and a photovoltaic panel is reduced. However, the problem of the excessive inductive current is not caused again when the V5 and V6 work, so the reactive modulation problem under the reactive condition must be considered (in the reactive state, the voltage and the current are opposite, when the V5 and V6 are conducted, the inductive current rises under the action of the grid voltage, at this time, the V1-V4 needs to be opened, and the reverse voltage drop is applied to the inductor to reduce the inductive current, if only the V5 and V6 are conducted, but the V1-V4 are not conducted, the inductive current is only increased but not reduced in the negative power interval, so the excessive inductive current is caused). For the Heric topology, since the high-frequency tubes in V5 and V6 are complementary to the inverter bridge driving signals, the high-frequency tubes have reactive modulation characteristics without changing the wave-sending logic. But in reactive modulation, the situation is different from active modulation. In active modulation, when the V1-V4 switching tube is turned on, the inductive current rises, the V1-V4 switching tube is turned off, and when the V5 and the V6 switching tube are turned on, the inductive current drops. However, in reactive power modulation, the situation is opposite, if the reactive power section is in overcurrent, the V1-V4 switching tube is turned off, and the V5 and V6 switching tubes are turned on, so that the overcurrent is further aggravated.
Referring to fig. 8, when an interruption event caused by an overcurrent is received, the judgment is made, and if the interruption event is active, the driving signal of the V1-V4 tube is blocked when the overcurrent occurs, and the V5 and the V6 are not limited or immediately open the tube to enter the follow current. If the tube is idle, the V5 tube and the V6 tube are immediately blocked, and the V1-V4 are normal. And if the overcurrent signal disappears, the drive signal is blocked according to the logic continuously, the interrupt event is not cleared, and the shutdown is stopped when the interruption continuously exists for more than 200ms within 1 second (the interruption exceeds 200ms is defaulted as overload, and the conditions are dangerous, such as output short circuit, continuous overload, circuit control failure and the like).
In combination with the sequential logic of the wave-by-wave Current limiting of the active power section shown in fig. 3, PWM1A _ TTL is a driving signal of the V1 and V4 transistors, PWM _ V1-V4_ TTL is a signal to which the wave-by-wave Current limiting protection is added, CBC _ LOCK1 is a wave-by-wave Current limiting and wave-blocking signal (active low), and Current _ Limit is an overcurrent detection signal (active low).
Because the body diode of V1-V4 is required to carry out follow current, the closing time of the switch tube is relatively long, the current of the inductor is large, the energy stored in the inductor is fully charged into the capacitor through the follow current loop, the voltage at two ends of the capacitor is increased, the bus is increased, and the problem that the bus voltage is increased, which possibly causes damage because the bus voltage exceeds the withstand voltage value of the switch tube or the bus capacitor, is solved.
The wave-by-wave current limiting protection can allow the current to exceed a specified value for a short time by a small amount, and performs feedback action on a switch control strategy, so that the phenomenon that the inverter is stopped due to short-time surge current or instantaneous current spike can be avoided on the premise of protecting the safety of a machine. The wave-by-wave current limiting strategy is that an overcurrent signal is generated by an overcurrent detection circuit, an interruption event is generated, when the interruption event exists, a response switch tube is blocked to enable the current to fall to a safe range, the interruption event is cleared, and the wave form is opened in the next PWM period after the interruption is relieved. The current wave-by-wave current limiting scheme is divided into two types, one is that all switch tubes are blocked immediately when overcurrent occurs, and the other is that only the inverter bridge switch tube is blocked. This scheme is a further improvement over the second partial lockout scheme.
Compared with the traditional H4 inverter circuit with hybrid modulation, the Heric inverter circuit has lower leakage current, so that higher efficiency and higher safety are obtained. In practice, V5, V6 can be connected in parallel with diodes between the live line and the neutral line, so that an interlock logic must be added between V1-V4 and V5, V6 to ensure that V5, V6 are not conductive during the opening period of V1-V4 to prevent short circuit. One tube is in a power frequency working state during the freewheeling period, but in order to ensure that the Heric inverter circuit can still normally freewheel in the reactive state, the other tube of the V5 and the V6 is in a high-frequency working state. When wave-by-wave current limiting is carried out in the scheme, the control characteristic is utilized, and current limiting control is carried out on the auxiliary tube during reactive power output.
The scheme of the embodiment can also be applied to an inversion topology, a main pipe and an auxiliary pipe in the inversion topology are separated, and the main pipe and the auxiliary pipe are respectively blocked according to different work attributes. The application range comprises: an H4 inverter circuit under hybrid modulation, an H5 inverter circuit H6 inverter circuit under hybrid modulation, a T-type NPC neutral point clamped half-bridge inverter circuit (TNPC), an I-type NPC neutral point clamped half-bridge inverter circuit (INPC) and an active neutral point clamped topology (ANPC).
In the embodiment, when an overcurrent signal is generated, the current direction and the voltage direction of the inverter output are obtained, the acting attribute of the Heric inverter circuit is determined according to the current direction and the voltage direction, the H-shaped inverter bridge or the follow current path is blocked according to the acting attribute, the stress of the high voltage of the bus and the stress of a switching tube device are effectively reduced, meanwhile, the connection time of the photovoltaic panel and a power grid is reduced, and the instantaneous leakage current is reduced. And the problem that the inductive current continuously increases when the reactive output is over-current under the traditional local wave-sealing strategy is solved. In addition, when photovoltaic inverter's life was effectively improved, can provide more stable power for electric automobile's equipment such as electric pile that fills.
Optionally, the checking the overcurrent signal, and when the overcurrent signal is generated, the obtaining the current direction and the voltage direction of the inverter output includes: detecting output current, and generating the overcurrent signal when the output current is greater than a preset value; and acquiring the current direction through a current sensor, and acquiring the voltage direction through a voltage sensor.
In this embodiment, when the overcurrent detection circuit generates an overcurrent signal, the current direction is obtained by the current sensor, the voltage direction is obtained by the voltage sensor, and then the work attribute can be determined according to the current direction and the voltage direction, so as to block the H-type inverter bridge or the follow current path according to the work attribute.
Optionally, the determining the work property of the logic inverter circuit according to the current direction and the voltage direction includes: when the current direction is the same as the voltage direction, judging that the work is in an active power section; and when the current direction is different from the voltage direction, judging that the work is in a reactive power section.
In the embodiment, the work applying property of the Heric inverter circuit is determined according to the current direction and the voltage direction, the H-shaped inverter bridge or the follow current path is blocked, the stress of the high voltage of the bus and the switch tube device is effectively reduced, meanwhile, the connection time of the photovoltaic panel and the power grid is reduced, and the instantaneous leakage current is reduced.
Optionally, said blocking said H-type inverter bridge or said free-wheeling path according to said work-done attribute comprises: when the work is in the active power section, blocking a driving signal of the H-shaped inverter bridge; and when the work is in the reactive power section, blocking the driving signal of the follow current path.
In the embodiment, the drive signal of the H-shaped inverter bridge or the drive signal of the follow current path is blocked according to the acting attribute, so that the stress of the high voltage of the bus and the stress of the switching tube device are effectively reduced, meanwhile, the connection time of the photovoltaic panel and the power grid is reduced, and the instantaneous leakage current is reduced. And the problem that the inductive current continuously increases when the reactive output is over-current under the traditional local wave-sealing strategy is solved.
Optionally, the wave-by-wave current limiting control method for the Heric inverter circuit further includes: and when the next PWM period comes, the over-current signal is detected again, if the over-current signal disappears, the PWM wave generation is opened again, an interruption event is eliminated, and if the over-current signal does not disappear, the H-shaped inverter bridge or the follow current path is blocked continuously according to the acting attribute.
In the embodiment, the overcurrent signal is detected again when the next PWM period comes, which is beneficial to the accuracy of high ripple-by-ripple current-limiting control.
The wave-by-wave current-limiting control device comprises an overcurrent detection circuit, a reactive power judgment circuit and a blocking circuit, wherein the reactive power judgment circuit is connected with the overcurrent detection circuit and the blocking circuit; the overcurrent detection circuit is used for detecting output current and generating an overcurrent signal when the output current is greater than a preset value; the active and reactive power judging circuit is used for determining the work property of the Heric inverter circuit according to the current direction and the voltage direction; the blocking circuit is used for blocking the H-shaped inverter bridge or the follow current path according to the acting attribute.
Specifically, in the present embodiment, a wave-by-wave current-limiting hardware wave-sealing (i.e., blocking the driving signal) scheme, which is not a full-sealing scheme, is described below with reference to a specific circuit.
Referring to fig. 4, when detecting the overcurrent signal, the comparator detects whether the inductor current (i.e., the output current) exceeds a current limit value (a preset value), and if so, outputs a low level to generate the overcurrent signal, and then the voltage and current directions are obtained by the voltage and current sensors.
In fig. 4, I _ REF _ H and I _ REF _ L are voltage reference values given by the DAC for setting upper and lower current limits, and IAC _ sample is connected to the output port of the current sensor.
Referring to fig. 5, the principle of the reactive power determining circuit is that the comparator determines the direction of current and voltage, and VAC _ MID and IAC _ MID are the output values of the voltage sensor and the current sensor at zero voltage and zero current, respectively, and are used as reference values here. VAC _ sample and IAC _ sample are output values of the voltage sensor and the current sensor, respectively. The current comparator outputs high level when the current direction is in a negative half cycle, the voltage comparator outputs high level when the voltage direction is in a positive half cycle, and the output of the circuit can be judged whether to output active work or not through an exclusive-OR gate, wherein the high level is useful work, and the low level is useless work.
If the current and the voltage are in the same direction, an active power section is formed, the V1-V4 switch tube is blocked, and if the current and the voltage are in the reverse direction, the V5 and V6 switch tubes are blocked, so that the blocking of an H-shaped inverter bridge or a follow current path is realized, the stress of the high voltage of a bus and the switch tube device is effectively reduced, meanwhile, the connection time of a photovoltaic panel and a power grid is reduced, and the instantaneous leakage current is reduced.
Referring to fig. 6, the core of the wave-sealing circuit of the V5 and V6 transistors is a D flip-flop, which takes and of the driving signals PWM2A _ TTL and PWM1B _ TTL of the V5 and V6 provided by the DSP to obtain the clock signal of the V5, V6PWM waveform. And judging whether the wave-sealing signal needs to be cleared or not every time when the rising edge occurs, taking 'OR' between the overcurrent signal and the reactive power judging signal, if the low level is output, indicating that the reactive power section is overcurrent, sending a low level wave-sealing signal CBC _ LOCK, and taking 'AND' between the wave-sealing signal and the driving signal given by the DSP to obtain driving waveforms V5 and V6 after wave-by-wave current limiting protection. Referring to fig. 7, the wave-by-wave current limiting of the V1-V4 tube is similar to that of V5 and V6, and the output of the reactive power judgment is inverted and connected to the D flip-flop.
The above contents provide two wave-sealing modes of software and hardware, and a part of hardware circuit and a part of software function are combined into a wave-by-wave current-limiting protection circuit with local blocking, which still remains the protection scope of the patent.
The implementation platform is not limited to the DSP but also comprises microcontrollers such as an MCU, an FPGA and the like. The logic gate position and the logic gate type in the circuit can be adaptively changed, and the purpose of blocking the switch tube in the patent is achieved; the scheme of using hardware description languages such as VHDL, Verilog and the like to realize the functionally equivalent circuit functions in the patent on FPGA and CPLD is also in the protection scope.
Optionally, the over-current detection circuit is configured to output a low level to generate the over-current signal when the output current is greater than a preset value.
Optionally, the active and reactive power determining circuit includes a comparator and an exclusive or gate, the comparator includes a current comparator and a voltage comparator, the current comparator is configured to output a high level when the current direction is in a negative half cycle, the voltage comparator is configured to output a high level when the voltage direction is in a positive half cycle, and the exclusive or gate is configured to take an output of the current comparator and an output of the voltage comparator as inputs, output a high level when the work is in an active power section, and output a low level when the work is in a reactive power section.
In the embodiment, the work attribute is determined by the reactive power judgment circuit, so that the H-shaped inverter bridge or the follow current path is blocked according to the work attribute, the stress of the high voltage of the bus and the switch tube device is effectively reduced, meanwhile, the connection time of the photovoltaic panel and the power grid is reduced, and the instantaneous leakage current is reduced. And the problem of the increase of the inductive current caused by keeping the corresponding follow current tube open according to the acting property is solved.
Optionally, the blocking circuit is configured to block a driving signal of the H-type inverter bridge or a driving signal of the freewheel path according to the work attribute.
Another embodiment of the present invention provides an inverter, including the above wave-by-wave current-limiting control device for a Heric inverter circuit.
Although the present disclosure has been described above, the scope of the present disclosure is not limited thereto. Various changes and modifications may be effected therein by one of ordinary skill in the pertinent art without departing from the spirit and scope of the present disclosure, and these changes and modifications are intended to be within the scope of the present disclosure.
Claims (10)
1. A wave-by-wave current limiting control method for a Heric inverter circuit, wherein the Heric inverter circuit comprises an H-shaped inverter bridge and a free-wheeling channel, and the free-wheeling channel is used for providing a free-wheeling channel in a free-wheeling stage so that the H-shaped inverter bridge is completely closed, and the wave-by-wave current limiting control method comprises the following steps:
checking an overcurrent signal, and acquiring the current direction and the voltage direction of the inversion output when the overcurrent signal is generated;
and determining the work attribute of the Heric inverter circuit according to the current direction and the voltage direction, and blocking the H-shaped inverter bridge or the follow current path according to the work attribute.
2. A wave-by-wave current limiting control method for Heric inverter circuit as claimed in claim 1, wherein said checking the over-current signal, when the over-current signal is generated, obtaining the current direction and the voltage direction of the inverter output comprises:
detecting output current, and generating the overcurrent signal when the output current is greater than a preset value;
and acquiring the current direction through a current sensor, and acquiring the voltage direction through a voltage sensor.
3. A wave-by-wave current limiting control method for a Heric inverter circuit as claimed in claim 2, wherein said determining work attributes of the Heric inverter circuit according to the current direction and the voltage direction comprises:
when the current direction is the same as the voltage direction, judging that the work is in an active power section;
and when the current direction is different from the voltage direction, judging that the work is in a reactive power section.
4. A wave-by-wave current limiting control method for a Heric inverter circuit as claimed in claim 3, wherein said blocking said H-type inverter bridge or said free-wheeling path according to said work attributes comprises:
when the work is in the active power section, blocking the driving signal of the H-shaped inverter bridge;
and when the work is in the reactive power section, blocking the driving signal of the follow current path.
5. A wave-by-wave current limiting control method for a Heric inverter circuit as claimed in any one of claims 1 to 4, further comprising: and when the next PWM period comes, the over-current signal is detected again, if the over-current signal disappears, the PWM wave generation is opened again, an interruption event is eliminated, and if the over-current signal does not disappear, the H-shaped inverter bridge or the follow current path is blocked continuously according to the acting attribute.
6. A wave-by-wave current limiting control device for a Heric inverter circuit, which applies the wave-by-wave current limiting control method for the Heric inverter circuit as claimed in any one of claims 1 to 5, wherein the Heric inverter circuit comprises an H-shaped inverter bridge and a free-wheeling channel, the free-wheeling channel is used for providing a free-wheeling channel in the free-wheeling stage so that the H-shaped inverter bridge is completely closed, and the wave-by-wave current limiting control device comprises an overcurrent detection circuit, a reactive power determination circuit and a blocking circuit;
the overcurrent detection circuit is used for detecting output current and generating an overcurrent signal when the output current is greater than a preset value;
the active and reactive power judging circuit is used for determining the work property of the Heric inverter circuit according to the current direction and the voltage direction;
the blocking circuit is used for blocking the H-shaped inverter bridge or the follow current path according to the acting attribute.
7. A wave-by-wave current limit control device for Heric inverter circuit as defined in claim 6, wherein said over-current detection circuit is used for outputting low level to generate said over-current signal when said output current is larger than a preset value.
8. A wave-by-wave current limiting control apparatus for an Heric inverter circuit as claimed in claim 6, wherein said active and reactive power decision circuit includes a comparator and an exclusive-OR gate, said comparator includes a current comparator for outputting a high level when said current direction is in a negative half cycle and a voltage comparator for outputting a high level when said voltage direction is in a positive half cycle, said exclusive-OR gate is for taking as input an output of said current comparator and an output of said voltage comparator, outputting a high level when working is in an active power section and outputting a low level when working is in a reactive power section.
9. A wave-by-wave current limiting control apparatus for Heric inverter circuit as defined in claim 6, wherein said blocking circuit is used for blocking the driving signal of said H-type inverter bridge or the driving signal of said freewheel path according to said work attribute.
10. An inverter, characterized by comprising the wave-by-wave current limiting control device for a Heric inverter circuit of any one of claims 6 to 9.
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