CN103185846B - A kind of countercurrent detection method, Countercurrent prevention control method, device and countercurrent prevention system - Google Patents
A kind of countercurrent detection method, Countercurrent prevention control method, device and countercurrent prevention system Download PDFInfo
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Abstract
The present invention is specifically related to a kind of countercurrent detection method, counterflow-preventing control device and countercurrent prevention system.The voltage over zero of the present invention by calculating electrical network access point and the mistiming of current zero-crossing point; detect adverse current whether to occur; detection speed is fast; adverse current can be detected within 1 ~ 5 cycle; thus quickening governing speed; avoid electric network protection device power-off protection, also for the time has been striven in soft readjustment, decrease the hard shutoff probability to grid power source.
Description
Technical Field
The invention belongs to an anti-reflux technology in the field of distributed power generation, and particularly relates to a countercurrent detection method, an anti-reflux control device and an anti-reflux system.
Background
At present, for a photovoltaic grid-connected power generation system, a power grid company generally requires that the photovoltaic grid-connected system is a non-countercurrent power generation system, that is, electricity generated by the photovoltaic grid-connected system is consumed by a local load and does not flow into a power grid to cause instability of the power grid and harmonic wave generation. With the support of the country on the photovoltaic power station, the number of photovoltaic grid-connected power stations is increased, and a reliable anti-reflux controller is needed.
The existing anti-reverse-current controller generally comprises a reverse power detection circuit, a reverse power control circuit and a reverse power regulating circuit; the inverse power detection generally adopts an intelligent measurement and control instrument, the instrument collects voltage and current parameters and then calculates power, an inverse power control circuit judges whether inverse power occurs or not according to the power, and then the inverse power control circuit controls an inverse power regulating circuit to correspondingly regulate. The method has the advantages that the detection speed is relatively slow, the power data is generally required to be updated for one time for more than 330ms, and therefore, the reverse power regulation has hysteresis and cannot be used in occasions with high requirements on reverse current protection time. And if the power grid reverse current exceeds the set protection time, the protection device is triggered to act, so that the power grid protective power failure accident is caused.
Disclosure of Invention
The invention provides a countercurrent detection method with high countercurrent detection speed, an anti-countercurrent control method, a device and an anti-countercurrent system aiming at the problems,
the invention provides a countercurrent detection method, which comprises the following steps:
detecting the voltage and the current of a power grid access point;
detecting the time difference between the voltage zero crossing point and the current zero crossing point of a power grid access point;
if the time difference is greater than one-quarter and less than three-quarters of the grid cycle, then reverse flow occurs, otherwise no reverse flow occurs.
The time difference between the voltage zero crossing point and the current zero crossing point of the power grid access point is detected by a timer, and specifically comprises the following steps:
when a voltage zero crossing point signal is detected, the timer starts timing, when a current zero crossing point signal is detected, the timer stops timing, and the time value detected by the timer is the time difference between the voltage zero crossing point and the current zero crossing point;
or,
and when the current zero crossing point signal is detected, the timer starts timing, when the voltage zero crossing point signal is detected, the timer stops timing, and the time value detected by the timer is the time difference between the voltage zero crossing point and the current zero crossing point.
According to the invention, whether the countercurrent occurs is detected by calculating the time difference between the voltage zero crossing point and the current zero crossing point of the power grid access point, the detection speed is high, and the countercurrent can be detected within 1-5 periods.
The invention provides an anti-reflux control method, which comprises a first countercurrent detection method, namely:
detecting an electric parameter of a power grid access point;
calculating power P of power grid access point1(ii) a Comparing the power P of the grid access points1And a preset counter-flow threshold value P0If P is1＞P0No reverse flow occurs, if P1＜P0Then a counter flow occurs;
further included is a second reverse power detection method, namely:
the method of countercurrent detection according to any one of claims 1 to 2;
and the first reverse power detection method and the second reverse power detection method detect simultaneously, if the reverse flow occurs, the output power of the grid-connected power supply is reduced, and if the reverse flow does not occur, the output power of the grid-connected power supply is increased.
Further, it is provided withThe period of the power grid is T, the time difference between the zero crossing point of the voltage and the zero crossing point of the current is T, and when 1/4T-T0< T < 1/4T or 3/4T < T < 3/4T + T0Or P1＜P0+P0' when, the output power of the grid-connected power supply is preset, i.e. reduced, where T0And P0' is a positive value.
When the power of the access point of the power grid suddenly drops, the first reverse power detection method cannot rapidly detect the reverse current, so that the power grid protective power failure accident is easily caused. The second reverse power detection method is high in detection speed and can quickly detect reverse current, and therefore the power grid protective power failure accident is prevented. However, the second inverse power detection method is more suitable for the situation that the countercurrent set threshold is zero, and the second inverse power detection method has low detection precision for the situation that the countercurrent set threshold is not zero, so that the method combining the two methods can meet the requirements of high precision and high detection speed.
The invention provides an anti-reflux control device, comprising:
the first reverse power detection circuit is used for acquiring voltage and current of a power grid access point, detecting a voltage zero crossing point and a current zero crossing point signal and sending the voltage zero crossing point and the current zero crossing point signal to the reverse power control circuit;
the reverse power control circuit is used for measuring the time difference between the voltage zero crossing point and the current zero crossing point of the power grid access point, and judging that the reverse flow occurs if the time difference is more than one fourth and less than three quarters of the power grid period, otherwise, the reverse flow does not occur;
and the reverse power regulating circuit controls the grid-connected power supply to work according to the judgment result.
Further, the backflow prevention control device further comprises:
the second reverse power detection circuit calculates the power P of the power grid access point according to the voltage and the current of the power grid access point acquired by the first reverse power detection circuit1Comparing the gridsAccess point power P1And a preset counter-flow threshold value P0If P is1＞P0No reverse flow occurs, if P1＜P0Then a counter flow occurs;
the first reverse power detection circuit and the second reverse power detection circuit work simultaneously, if reverse flow occurs, the reverse power adjusting circuit reduces the output power of the grid-connected power supply, and if no reverse flow occurs, the reverse power adjusting circuit increases the output power of the grid-connected power supply.
Further, when the grid period is T, the time difference between the zero crossing point of the voltage and the zero crossing point of the current is T, and when 1/4T-T0< T < 1/4T or 3/4T < T < 3/4T + T0Or P1＜P0+P0' when, the output power of the grid-connected power supply is preset, i.e. reduced, where T0And P0' is a positive value.
Further, the first inverse power detection circuit includes:
the voltage sampling circuit is used for acquiring voltage waveform signals of a power grid access point;
the voltage zero-crossing point detection circuit is used for receiving the voltage waveform signal of the power grid access point, detecting the voltage zero-crossing point and outputting the voltage zero-crossing signal to the reverse power control circuit;
the current sampling circuit is used for acquiring a current waveform signal of a power grid access point;
and the current zero-crossing point detection circuit is used for receiving the current waveform signal of the power grid access point, detecting the current zero-crossing point and outputting the current zero-crossing signal to the reverse power control circuit.
The method for measuring the time difference between the voltage zero crossing point and the current zero crossing point of the power grid access point comprises the following steps:
the voltage sampling circuit and the current sampling circuit collect voltage waveform signals and current waveform signals of a power grid access point;
when the voltage signal crosses zero, the voltage zero crossing point detection circuit outputs a zero crossing point signal to the reverse power control circuit, and a timer of the reverse power control circuit starts timing;
when the current signal crosses zero, the current zero crossing point detection circuit outputs a zero crossing point signal to the reverse power control circuit, and a timer of the reverse power control circuit stops timing;
the time value detected by the timer is the time difference between the voltage zero crossing point and the current zero crossing point;
or,
when the current signal crosses zero, the current zero crossing point detection circuit outputs a zero crossing point signal to the reverse power control circuit, and a timer of the reverse power control circuit starts timing;
when the voltage signal crosses zero, the voltage zero crossing point detection circuit outputs a zero crossing point signal to the reverse power control circuit, and a timer of the reverse power control circuit stops timing;
the time value detected by the timer is the time difference between the voltage zero crossing point and the current zero crossing point.
Furthermore, the number of the first inverse power detection circuits is multiple.
The invention provides an anti-reflux system, which comprises a grid-connected power supply, a power grid, a local load and a signal conversion device, wherein the grid-connected power supply and the power grid are respectively connected with the local load, and the system also comprises:
in the anti-backflow control device, one end of the anti-backflow control device is connected with the grid-connected power supply, and the other end of the anti-backflow control device is connected with the power grid through the signal conversion device.
According to the anti-reflux control device and the anti-reflux system, the reverse power detection method with high detection speed is adopted, and the reverse current can be detected within 1-5 periods, so that the adjustment speed is increased, the power-off protection of a power grid protection device is avoided, time is also strived for flexible adjustment, and the hard turn-off probability of a grid-connected power supply is reduced.
Drawings
FIG. 1 is a schematic diagram of the connection of one embodiment of the anti-reflux control device of the present invention;
FIG. 2 is a schematic connection diagram of a second embodiment of the backflow prevention control device of the present invention;
FIG. 3 is a schematic connection diagram of a third embodiment of the backflow prevention control device of the present invention;
FIG. 4 is a schematic connection diagram of a fourth embodiment of the backflow prevention control device of the present invention;
FIG. 5 is a schematic diagram of the connection of one embodiment of the anti-reflux system of the present invention.
Detailed Description
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 reverse power detection method is based on the following principle: and setting the power of the power grid access point as P, setting a counter flow threshold value as 0, when P is more than 0, no counter flow occurs, and when P is less than 0, counter flow occurs. The grid access point power P is U · I · cos θ, where U, I is the voltage and current of the grid access point and θ is the phase difference between U, I. When theta is less than 90 degrees, P is greater than zero, and when theta is greater than 90 degrees, P is less than zero. In order to realize the detection of theta, the invention adopts a method for detecting the time difference between the zero crossing point of the voltage and the zero crossing point of the current, and particularly, according to the fact that if the time difference between the zero crossing points of the voltage and the current is less than the quarter cycle time (50Hz power grid: 5000 mu s), theta is less than 90 degrees, P is greater than zero and no backflow occurs, if the time difference is greater than the quarter cycle time (50Hz power grid: 5000 mu s), theta is greater than 90 degrees, P is less than zero and backflow occurs.
According to the above principle, the present invention provides a method for detecting a reverse flow, comprising:
detecting the voltage and the current of a power grid access point;
detecting the time difference between the voltage zero crossing point and the current zero crossing point of a power grid access point;
if the time difference is greater than one-quarter cycle, then counter-flow occurs, otherwise no counter-flow occurs.
Specifically, the time difference between the zero crossing point of the voltage and the zero crossing point of the current of the power grid access point is detected by a timer, specifically:
when a voltage zero crossing point signal is detected, the timer starts timing, when a current zero crossing point signal is detected, the timer stops timing, and the time value detected by the timer is the time difference between the voltage zero crossing point and the current zero crossing point;
or,
and when the current zero crossing point signal is detected, the timer starts timing, when the voltage zero crossing point signal is detected, the timer stops timing, and the time value detected by the timer is the time difference between the voltage zero crossing point and the current zero crossing point.
Because the detection method is more suitable for the occasion that the counter current set threshold is zero and the occasion that the counter current set threshold is not zero, the detection precision of the detection method is low, and if the detection method is only adjusted according to the method, the counter current can not be accurately controlled, therefore, the invention provides a counter current control method adopting two counter power detection methods, which comprises the following steps:
the first counter-current detection method, namely:
detecting an electric parameter of a power grid access point;
calculating power P of power grid access point1(ii) a Comparing the power P of the grid access points1And a preset counter-flow threshold value P0If P is1＞P0No reverse flow occurs, if P1＜P0Then a counter flow occurs;
further included is a second reverse power detection method, namely:
the method of countercurrent detection according to any one of claims 1 to 2;
the first reverse power detection method and the second reverse power detection method detect simultaneously, and in any method, once the occurrence of the reverse flow is detected, the output power of the grid-connected power supply is reduced, and if the occurrence of the reverse flow is not detected, the output power of the grid-connected power supply is increased.
The countercurrent set threshold is generally zero or a positive value, and the second reverse power detection method is high in detection accuracy and high in speed when the countercurrent set threshold is zero. On the occasion that the set counter flow threshold value is not zero, when the power of the power grid access point is slowly reduced from a positive value, the counter flow cannot be detected by the second counter power detection method, and at the moment, the counter flow is mainly detected by the first counter power detection method for flexible adjustment; when the power of the power grid access point suddenly drops to zero, the first reverse power detection method is slow in detection speed, and therefore the reverse flow can not be detected quickly, and the second reverse power detection method can detect the reverse flow quickly at the moment, so that the defects of the first reverse power detection method are overcome. By adopting the method of combining the first inverse power detection method and the second inverse power detection method, the requirement of high precision can be met on the occasion that the countercurrent set threshold value is not zero, and the requirement of high detection speed can be met.
Further, when the grid period is T, the time difference between the zero crossing point of the voltage and the zero crossing point of the current is T, and when 1/4T-T0< T < 1/4T or 3/4T < T < 3/4T + T0Or P1＜P0+P0When, the output power of the grid-connected power supply is preset, i.e.Reducing the output power of a grid-connected power supply, wherein T0And P0' is a positive value.
When the time difference is close to 1/4 power grid period or 3/4 power grid period or the power of the power grid access point is close to a reverse flow set threshold value, the grid-connected inverter power supply is pre-adjusted, and reverse flow can be prevented better. The amplitude of the regulation may be smaller than the amplitude of the formal regulation, T0And P0The value of' can also be set as desired. Of course, the time or power may be segmented and the adjustment may be performed in a segmented manner.
For example 1/8T < T < 3/16T or 13/16T < T < 7/8T, the modulation amplitude is A1; when T is more than 3/16T and less than 1/4T or 3/4T and less than T and less than 13/16T, the adjusting amplitude is A2; when T is more than 1/4T and less than 3/4T, the regulating amplitude is A3; the A1 < A2 < A3.
The 1/4 grid cycle and 3/4 grid cycle are not limited to just 1/4 grid cycle or 3/4 grid cycle, and slightly less than or slightly greater than these values are within the scope of the present invention due to the different regulations of the grid companies.
Correspondingly, the invention also provides an anti-backflow control device, and the principles of the anti-backflow control device and the anti-backflow control method are basically the same, and the description is not repeated here.
As shown in fig. 1, the backflow prevention control apparatus of the present invention includes:
a first reverse power detection circuit 10, a reverse power control circuit 20, and a reverse power adjustment circuit 30; wherein, the signal input end of the reverse power control circuit 20 is connected with the signal output end of the first reverse power detection circuit 10 for monitoring the voltage and the current of the power grid 500, and the output end of the reverse power control circuit 20 is connected with the signal input end of the reverse power adjusting circuit 30. The first reverse power detection circuit 10 is used for acquiring voltage and current of a power grid access point, detecting a voltage zero crossing point and a current zero crossing point signal and sending the voltage zero crossing point and the current zero crossing point signal to the reverse power control circuit 20; the reverse power control circuit 20 is used for measuring the time difference between the voltage zero crossing point and the current zero crossing point of the power grid access point, and judging that the reverse flow occurs if the time difference is more than one fourth and less than three fourths of the power grid period, otherwise, the reverse flow does not occur; and a reverse power adjusting circuit 30 for controlling the operation of the grid-connected power supply 200 based on the determination result.
Further, as shown in fig. 3, the backflow prevention control device further includes:
and the input end of the second inverse power detection circuit 40 is connected with the output end of the first inverse power detection circuit 10, and the output end of the second inverse power detection circuit 40 is connected with the input end of the inverse power control circuit 20. The second inverse power detection circuit 40 calculates the power P of the power grid access point according to the voltage and current of the power grid access point collected by the first inverse power detection circuit 101Comparing the power P of the grid access point1And a preset counter-flow threshold value P0If P is1＞P0No reverse flow occurs, if P1＜P0Then a counter flow occurs;
the first reverse power detection circuit 10 and the second reverse power detection circuit 40 work simultaneously, if a reverse flow occurs, the reverse power regulation circuit 30 reduces the output power of the grid-connected power supply 200, and if no reverse flow occurs, the reverse power regulation circuit 30 increases the output power of the grid-connected power supply 200.
Further, when the grid period is T, the time difference between the zero crossing point of the voltage and the zero crossing point of the current is T, and when 1/4T-T0< T < 1/4T or 3/4T < T < 3/4T + T0Or P1＜P0+P0' when, the output power of the grid-connected power supply 200 is preset, i.e. the output power of the grid-connected power supply 200 is reduced, wherein T0And P0' is a positive value.
Specifically, as shown in fig. 2 and 3, the first reverse power detection circuit 10 includes: the device comprises a voltage sampling circuit 11, a voltage zero crossing point detection circuit 12, a current sampling circuit 13 and a current zero crossing point detection circuit 14; the signal output end of the voltage sampling circuit 11 is connected with the signal input end of the voltage zero crossing point detection circuit 12, the signal output end of the voltage zero crossing point detection circuit 12 is connected with the signal input end 101 of the inverse power control circuit 20, the signal output end of the current sampling circuit 13 is connected with the signal input end of the current zero crossing point detection circuit 14, and the signal output end of the current zero crossing point detection circuit 14 is connected with the signal input end I02 of the inverse power control circuit 20. The input end of the second inverse power detection circuit 40 is respectively connected with the output ends of the voltage sampling circuit 11 and the current sampling circuit 13, and the output end of the second inverse power detection circuit 40 is connected with the input end of the inverse power control circuit 20.
Specifically, the voltage sampling circuit 11 and the current sampling circuit 13 collect voltage waveform signals and current waveform signals of a power grid access point;
when the voltage signal crosses zero, the voltage zero crossing detection circuit 12 outputs a zero crossing signal to IO1 of the reverse power control circuit 20, and IO1 triggers a timer T of the reverse power control circuit 20 to start timing;
when the current signal crosses zero, the current zero crossing point detection circuit 14 outputs a zero crossing point signal to the IO2 of the reverse power control circuit 20, and the IO2 triggers the timer T of the reverse power control circuit 20 to stop timing;
the timing value is t, namely the time difference between the voltage zero crossing point and the current zero crossing point;
if t < quarter cycle time (50Hz grid: 5000 mus), the grid access point power P is positive and no reverse flow occurs, if t > quarter cycle time (50Hz grid: 5000 mus), the grid access point power P is negative and reverse flow occurs.
Then, the reverse power adjusting circuit 30 controls the grid-connected power supply 200 to operate according to the reverse flow judgment result.
Further, as shown in fig. 4, there are a plurality of first reverse power detection circuits 10. When the anti-backflow control device performs anti-backflow control on a three-phase system, 3 first anti-power detection circuits 10 need to be arranged to perform anti-power detection on each phase. When the anti-backflow control device controls a plurality of grid-connected inverter power supplies to work simultaneously, a plurality of first inverse power detection circuits 10 are also needed to be arranged to detect each grid-connected inverter power supply respectively.
As shown in fig. 5, the present invention further provides an anti-reflux system, including a grid-connected power supply 200, a power grid 500, a local load 400 and a signal conversion device 300, wherein the grid-connected power supply 200 is connected to the local load, the power grid 500 is connected to the local load through the signal conversion device 300, and the system further includes:
in the above anti-backflow control device, one end of the anti-backflow control device is connected to the grid-connected power supply, and the other end is connected to the power grid 500 through the signal conversion device 300. The signal conversion device 300 converts the electric parameters of the power grid access point from strong electric signals to weak electric signals and outputs the weak electric signals to the backflow prevention control device, and the backflow prevention control device performs control according to the method. The specific location of the grid access point is shown in figure 3.
Further, there are a plurality of grid-connected power supplies 200. When the local load 400 has a large power consumption, a plurality of grid-connected power supplies 200 can be used for supplying power to the load at the same time, and the backflow prevention control device can control the plurality of grid-connected power supplies 200 to work at the same time. The anti-backflow control device controls the power of the whole grid-connected power supply 200 to meet the requirements of anti-backflow and normal power supply, and different control strategies can be adopted for power distribution among the grid-connected power supplies 200 according to the requirements.
Further, the grid-connected power supply 200 is a photovoltaic grid-connected inverter power supply. The grid-connected power supply 200 is not limited to a photovoltaic grid-connected inverter power supply, and other power supplies such as a wind power grid-connected power supply, an energy storage grid-connected power supply and the like can be applied to the invention and achieve the purpose of the invention. The power grid 500 is not limited to a utility power grid, and may include other power generation devices.
Further, the reverse power control circuit 20 is an electrical element logic control circuit, and the anti-reverse flow control device is connected with the background monitoring system and the scheduling system through an ethernet, a CAN port or an optical fiber. The communication mode is not limited to these modes, and communication modes such as RS485 or wireless communication can also be adopted.
According to the invention, the voltage zero-crossing point and current zero-crossing point time difference of the power grid access point is detected, so that the detection of the voltage and current phase difference is realized, the countercurrent detection is realized, the speed is high, the countercurrent can be judged within 1-5 periods (50Hz power grid: 20-100 ms), the energy output from the photovoltaic grid-connected power supply to the power grid in the countercurrent mode can be rapidly avoided, the probability of hard cut protection is reduced, and the impact and harmonic pollution to the power grid are reduced.
Claims (10)
1. A method of counter-current detection comprising:
detecting the voltage and the current of a power grid access point;
detecting the time difference between the voltage zero crossing point and the current zero crossing point of a power grid access point;
if the time difference is more than one fourth and less than three quarters of the grid period, the counter flow occurs, otherwise, the counter flow does not occur;
the time difference between the voltage zero crossing point and the current zero crossing point of the power grid access point is detected by a timer, and specifically comprises the following steps:
when a voltage zero crossing point signal is detected, the timer starts timing, when a current zero crossing point signal is detected, the timer stops timing, and the time value detected by the timer is the time difference between the voltage zero crossing point and the current zero crossing point;
or,
and when the current zero crossing point signal is detected, the timer starts timing, when the voltage zero crossing point signal is detected, the timer stops timing, and the time value detected by the timer is the time difference between the voltage zero crossing point and the current zero crossing point.
2. An anti-reflux control method comprises a first reverse power detection method, namely:
detecting an electric parameter of a power grid access point;
calculating power P of power grid access point1(ii) a Comparing the power P of the grid access points1And a preset reverse flow threshold value P0If P is1＞P0No reverse flow occurs, if P1＜P0Then a counter flow occurs;
the method is characterized in that: further included is a second reverse power detection method, namely:
the countercurrent detection method of claim 1;
and the first reverse power detection method and the second reverse power detection method detect simultaneously, if the reverse flow occurs, the output power of the grid-connected power supply is reduced, and if the reverse flow does not occur, the output power of the grid-connected power supply is increased.
3. The backflow prevention control method according to claim 2, characterized in that:
setting the period of the power grid as T, the time difference between the zero crossing point of the voltage and the zero crossing point of the current as T, and when 1/4T-T0< T < 1/4T or 3/4T < 3/4T + T0Or P1＜P0+P0' when, the output power of the grid-connected power supply is preset, i.e. reduced, where T0And P0' is a positive value.
4. An anti-reflux control device is characterized in that: the method comprises the following steps:
the first reverse power detection circuit is used for acquiring voltage and current of a power grid access point, detecting a voltage zero crossing point and a current zero crossing point signal and sending the voltage zero crossing point and the current zero crossing point signal to the reverse power control circuit;
the reverse power control circuit is used for measuring the time difference between the voltage zero crossing point and the current zero crossing point of the power grid access point, and judging that the reverse flow occurs if the time difference is more than one fourth and less than three quarters of the power grid period, otherwise, the reverse flow does not occur; the time difference between the voltage zero crossing point and the current zero crossing point of the power grid access point is detected by a timer, and specifically comprises the following steps: when a voltage zero crossing point signal is detected, the timer starts timing, when a current zero crossing point signal is detected, the timer stops timing, and the time value detected by the timer is the time difference between the voltage zero crossing point and the current zero crossing point; or, when the current zero crossing point signal is detected, the timer starts timing, when the voltage zero crossing point signal is detected, the timer stops timing, and the time value detected by the timer is the time difference between the voltage zero crossing point and the current zero crossing point;
and the reverse power regulating circuit controls the grid-connected power supply to work according to the judgment result.
5. The backflow prevention control device according to claim 4, wherein: the backflow prevention control device further comprises:
the second reverse power detection circuit calculates the power P of the power grid access point according to the voltage and the current of the power grid access point acquired by the first reverse power detection circuit1Comparing the power P of the grid access point1And a preset reverse flow threshold value P0If P is1＞P0No reverse flow occurs, if P1＜P0Then a counter flow occurs;
the first reverse power detection circuit and the second reverse power detection circuit work simultaneously, if reverse flow occurs, the reverse power adjusting circuit reduces the output power of the grid-connected power supply, and if no reverse flow occurs, the reverse power adjusting circuit increases the output power of the grid-connected power supply.
6. The backflow prevention control device according to claim 5 or 4, wherein: setting the period of the power grid as T, the time difference between the zero crossing point of the voltage and the zero crossing point of the current as T, and when 1/4T-T0< T < 1/4T or 3/4T < 3/4T + T0Or P1＜P0+P0' when, the output power of the grid-connected power supply is preset, i.e. reduced, where T0And P0' is a positive value.
7. The backflow prevention control device according to claim 4, wherein: the first reverse power detection circuit comprises:
the voltage sampling circuit is used for acquiring voltage waveform signals of a power grid access point;
the voltage zero-crossing point detection circuit is used for receiving the voltage waveform signal of the power grid access point, detecting the voltage zero-crossing point and outputting the voltage zero-crossing signal to the reverse power control circuit;
the current sampling circuit is used for acquiring a current waveform signal of a power grid access point;
and the current zero-crossing point detection circuit is used for receiving the current waveform signal of the power grid access point, detecting the current zero-crossing point and outputting the current zero-crossing signal to the reverse power control circuit.
8. The backflow prevention control device of claim 7, wherein: the method for measuring the time difference between the voltage zero crossing point and the current zero crossing point of the power grid access point comprises the following steps:
the voltage sampling circuit and the current sampling circuit collect voltage waveform signals and current waveform signals of a power grid access point;
when the voltage signal crosses zero, the voltage zero crossing point detection circuit outputs a zero crossing point signal to the reverse power control circuit, and a timer of the reverse power control circuit starts timing;
when the current signal crosses zero, the current zero crossing point detection circuit outputs a zero crossing point signal to the reverse power control circuit, and a timer of the reverse power control circuit stops timing;
the time value detected by the timer is the time difference between the voltage zero crossing point and the current zero crossing point;
or,
when the current signal crosses zero, the current zero crossing point detection circuit outputs a zero crossing point signal to the reverse power control circuit, and a timer of the reverse power control circuit starts timing;
when the voltage signal crosses zero, the voltage zero crossing point detection circuit outputs a zero crossing point signal to the reverse power control circuit, and a timer of the reverse power control circuit stops timing;
the time value detected by the timer is the time difference between the voltage zero crossing point and the current zero crossing point.
9. The backflow prevention control device according to claim 4, wherein: the first reverse power detection circuit is provided with a plurality of circuits.
10. An anti-reflux system, comprising: the system comprises a grid-connected power supply, a power grid, a local load and a signal conversion device, wherein the grid-connected power supply and the power grid are respectively connected with the local load, and the system is characterized in that: the system further comprises:
the backflow prevention control device of any one of claims 4 to 9, wherein one end of the backflow prevention control device is connected to a grid-connected power supply, and the other end of the backflow prevention control device is connected to a power grid through a signal conversion device.
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| CN103779834B (en) * | 2013-11-09 | 2016-07-06 | 国家电网公司 | One is applied to distributed power generation grid integration counterflow-preventing intelligent detecting method |
| CN103887817B (en) * | 2014-03-15 | 2016-08-17 | 杭州国电能源环境设计研究院有限公司 | Family Anti-reflux controller |
| CN104124706A (en) * | 2014-07-16 | 2014-10-29 | 常州思普锐电力科技有限公司 | Reverse power protection power distribution network system with distributed power source |
| US9915687B2 (en) * | 2015-03-27 | 2018-03-13 | Liebert Corporation | Real current meter |
| CN104796077A (en) * | 2015-04-27 | 2015-07-22 | 浙江昱能科技有限公司 | Anti-countercurrent distributed solar photovoltaic system and countercurrent prevention method |
| CN105978040B (en) * | 2016-06-15 | 2018-10-09 | 苏州汇川技术有限公司 | Variable-frequency variable-voltage power supply intelligence inverse probability control system and control method |
| CN107069798B (en) * | 2017-01-17 | 2023-05-09 | 陕西科技大学 | Control method and system for distributed photovoltaic power generation system |
| CN110148928A (en) * | 2019-05-30 | 2019-08-20 | 中国石油大学(华东) | A kind of dotted network reverse-power protection method containing DERs based on forward-order current phase bit comparison |
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