CN112421577A - Rapid power-off protection method for photovoltaic inverter - Google Patents
Rapid power-off protection method for photovoltaic inverter Download PDFInfo
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- CN112421577A CN112421577A CN202011168956.4A CN202011168956A CN112421577A CN 112421577 A CN112421577 A CN 112421577A CN 202011168956 A CN202011168956 A CN 202011168956A CN 112421577 A CN112421577 A CN 112421577A
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- inverter
- overcurrent
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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
- H02H7/1227—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 responsive to abnormalities in the output circuit, e.g. short circuit
Abstract
The invention discloses a rapid power-off protection method of a photovoltaic inverter, which comprises the following steps: A. configuring a PWM register of an inverter drive to seal the inverter drive at a software overcurrent protection point and during overcurrent; B. judging whether the output side of the photovoltaic inverter is powered off or not; when the result is true, the following step C is performed; C. triggering a software protection function, setting an overcurrent flag bit as 1, clearing an inverter current soft start flag bit as 0, and counting Count as 0; D. judging whether the Count value is less than 1 or not in the interrupt control; when the result is true, adding the soft start length to the Count value in each interrupt period; when the result is negative, the soft-start function is finished, the inversion current soft-start mark position is 1, and the Count is 1; E. and obtaining soft-start reference current according to the inversion control reference current and the Count value. The rapid power-off protection method can well solve the impact of inverter current at the moment of power-off.
Description
Technical Field
The invention belongs to the field of photovoltaic inverters, and relates to a rapid power-off protection method of a photovoltaic inverter.
Background
In our country, photovoltaic power generation occupies a very important position in the current power production, and through years of exploration and research, the number of construction is continuously increased, the scale is continuously enlarged, and the advantages of reproducibility, high conversion efficiency, environmental protection and the like are paid more attention and supported by the country.
In practical networking operation, grid-connected side voltage outage often occurs, and an island is formed between an inverter and a load. Due to the phenomenon, the pre-stage of the inverter inductor generates current to generate self-excited oscillation impact, and the impact can cause serious influence on the hardware reliability under a specific working environment. Especially, components with smaller overcurrent parameters are easy to break down.
Under the condition of overcurrent, a hardware overcurrent protection mode is generally adopted to realize the overcurrent protection method, the method is simple and quick, but the method can not be triggered every time the power is cut off.
Disclosure of Invention
In order to solve the technical problems, the invention aims to provide a rapid power-off protection method for a photovoltaic inverter, which triggers software overcurrent protection at the power-off instant, soft starts an inversion reference current during the overcurrent protection, and effectively controls the inversion reference current so as to well solve the impact of the inversion current at the power-off instant.
In order to achieve the purpose, the invention adopts the technical scheme that:
a rapid power-off protection method for a photovoltaic inverter comprises the following steps:
A. configuring a PWM register of an inverter drive to seal the inverter drive at a software overcurrent protection point and during overcurrent;
B. judging whether the output side of the photovoltaic inverter is powered off or not; when the result is true, the following step C is performed;
C. triggering a software protection function, setting an overcurrent flag bit as 1, clearing an inverter current soft start flag bit as 0, and counting Count as 0;
D. judging whether the Count value is less than 1 or not in the interrupt control; when the result is true, adding the soft start length to the Count value in each interrupt period; when the result is negative, the soft-start function is finished, the inversion current soft-start mark position is 1, and the Count is 1;
E. and obtaining soft-start reference current according to the inversion control reference current and the Count value.
Preferably, in the step B, when the result is no, the step a is returned to.
Preferably, in the step D, the soft start length is less than 1.
Preferably, in the step E, the reference current of the inverter control is multiplied by the Count value to obtain the soft-start reference current.
Compared with the prior art, the invention has the following advantages by adopting the scheme:
according to the rapid power-off protection method for the photovoltaic inverter, the software overcurrent protection point is set to serve as the reference of machine overcurrent, and after the software overcurrent action is triggered preferentially at the power-off moment, the driving of the inverter side is controlled. The control strategy adopts a voltage outer ring and a current inner ring for control, and the reference voltage is the voltage of the relay intermediate point. At the moment of power failure, the reference voltage cannot immediately disappear due to the capacitance of the reference voltage, so that the current reference of the control loop is continuously increased. The reference current is now limited to slowly increasing from 0 by increasing the soft-up function and soft-up step size. By the method, the risk of the explosion machine caused by overcurrent at most of power-off moments can be avoided.
Drawings
In order to more clearly illustrate the technical solution of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on the drawings without creative efforts.
FIG. 1 is a flow chart of a control method according to an embodiment of the invention;
FIG. 2 illustrates a software protection waveform;
FIG. 3 illustrates a software protection unwind waveform;
FIG. 4 shows waveforms for increasing soft-up reference current during software protection;
fig. 5 shows an expanded waveform for increasing soft-up reference current during software protection.
Detailed Description
Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings so that the advantages and features of the invention may be more readily understood by those skilled in the art. It should be noted that the description of the embodiments is provided to help understanding of the present invention, but the present invention is not limited thereto. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
The embodiment provides a rapid power-off protection method for a photovoltaic inverter, which can trigger software overcurrent protection at the moment of power failure, soft start an inversion reference current during overcurrent protection, and effectively control the inversion reference current to well solve the impact of the inversion current at the moment of power failure. Referring to fig. 1, the fast power-off protection method is implemented as follows.
S100, configuring a PWM register of inversion driving through software, and mainly configuring DACVAL and COMP control register COMPCTL. The method controls the software overcurrent protection point A and the action of sealing drive during overcurrent, and specifically comprises the following steps: after the MCU detects overcurrent, the stand horse releases a low level signal through the IO port, the signal is used as an enabling signal for controlling driving, and the high level is effective. Normally, the software protection point is smaller than the hardware overcurrent protection point of the hardware circuit design.
S200, at the moment of power failure of the output side of the photovoltaic inverter, due to the existence of a software protection function, the protection is triggered preferentially, the inverter side is driven, an overcurrent flag uwInveSurOverFlag is set to be 1, an inverter current soft start flag uwInveSoft Start flag is clear 0, and a soft start Count is clear 0.
S300, in the interrupt control, it is determined that when the Count value is smaller than 1, the soft start length mfinvesiftstartstep is added to the Count value for each interrupt cycle. mfinvesift startstep <1, which determines the soft-up period, the soft-up time is 800ms for the specific design in this example). When the Count is equal to or greater than 1, the soft start function is ended, uwInveSoft StarFlag is set to 1, and Count is set to 1. The interrupt control is specifically: through the register configuration of the MCU, the relevant parameters of the timer 0 are configured, the interrupt is configured to be 16K, namely the interrupt is timed to enter every 62.5us, and the interrupt requirement is processed.
S400, calculating soft start reference current: and multiplying the reference current of the inversion control by the soft-start Count to obtain a soft-start reference current. The soft-start reference current avoids the situation that the current reference is continuously increased in a self-excited mode to cause the explosion of the electric fryer due to the continuous action of the control loop at the moment of power failure.
Fig. 2 and 3 show waveforms in the same condition, wherein fig. 3 is an expanded view of fig. 2, it can be seen that at the moment of power failure, the output current will self-oscillate, and an overcurrent fryer is easy to occur. Fig. 4 and 5 show waveforms in the same condition, wherein fig. 5 is an expanded view of fig. 4, and a soft start function is added, and the reference current is slowly increased from 0 at the moment of power failure, so that the current impact is not basically seen at the moment of power failure.
The method takes a software overcurrent protection point as a machine overcurrent reference, and controls the driving of the inverter side after the software overcurrent action is preferentially triggered at the moment of power failure. The control strategy adopts a voltage outer ring and a current inner ring for control, and the reference voltage is the voltage of the relay intermediate point. At the moment of power failure, the reference voltage cannot immediately disappear due to the capacitance of the reference voltage, so that the current reference of the control loop is continuously increased. The reference current is now limited to slowly increasing from 0 by increasing the soft-up function and soft-up step size. By the method, the risk of the explosion machine caused by overcurrent at most of power-off moments can be avoided.
The above embodiments are merely illustrative of the technical ideas and features of the present invention, and are preferred embodiments, which are intended to enable those skilled in the art to understand the contents of the present invention and implement the present invention, and not to limit the scope of the present invention. All equivalent changes or modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.
Claims (4)
1. A rapid power-off protection method for a photovoltaic inverter is characterized by comprising the following steps:
A. configuring a PWM register of an inverter drive to seal the inverter drive at a software overcurrent protection point and during overcurrent;
B. judging whether the output side of the photovoltaic inverter is powered off or not; when the result is true, the following step C is performed;
C. triggering a software protection function, setting an overcurrent flag bit as 1, clearing an inverter current soft start flag bit as 0, and counting Count as 0;
D. judging whether the Count value is less than 1 or not in the interrupt control; when the result is true, adding the soft start length to the Count value in each interrupt period; when the result is negative, the soft-start function is finished, the inversion current soft-start mark position is 1, and the Count is 1;
E. and obtaining soft-start reference current according to the inversion control reference current and the Count value.
2. The fast power-off protection method according to claim 1, wherein: and in the step B, when the result is negative, returning to the step A.
3. The fast power-off protection method according to claim 1, wherein: in the step D, the soft starting length is less than 1.
4. The fast power-off protection method according to claim 1, wherein: in the step E, the reference current of the inverter control is multiplied by the Count value to obtain the soft-start reference current.
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Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103683893A (en) * | 2014-01-09 | 2014-03-26 | 惠州天能源科技有限公司 | Software protecting method for start short circuit of off-line inverter |
| CN106786395A (en) * | 2016-12-09 | 2017-05-31 | 芯洲科技（北京）有限公司 | A kind of protection circuit and method |
| CN107276019A (en) * | 2017-08-21 | 2017-10-20 | 合肥翔望智能科技有限公司 | A kind of dynamic over-current protection method of photovoltaic DC-to-AC converter |
| CN210579385U (en) * | 2019-09-23 | 2020-05-19 | 深圳瓦特智汇科技有限公司 | Sequential control circuit for suppressing current overshoot by BUCK topology |
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2020
- 2020-10-28 CN CN202011168956.4A patent/CN112421577B/en active Active
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103683893A (en) * | 2014-01-09 | 2014-03-26 | 惠州天能源科技有限公司 | Software protecting method for start short circuit of off-line inverter |
| CN106786395A (en) * | 2016-12-09 | 2017-05-31 | 芯洲科技（北京）有限公司 | A kind of protection circuit and method |
| CN107276019A (en) * | 2017-08-21 | 2017-10-20 | 合肥翔望智能科技有限公司 | A kind of dynamic over-current protection method of photovoltaic DC-to-AC converter |
| CN210579385U (en) * | 2019-09-23 | 2020-05-19 | 深圳瓦特智汇科技有限公司 | Sequential control circuit for suppressing current overshoot by BUCK topology |
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