CN110649700A - Method for preventing user circuit from reversely transmitting power to power grid - Google Patents
Method for preventing user circuit from reversely transmitting power to power grid Download PDFInfo
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- CN110649700A CN110649700A CN201910976294.4A CN201910976294A CN110649700A CN 110649700 A CN110649700 A CN 110649700A CN 201910976294 A CN201910976294 A CN 201910976294A CN 110649700 A CN110649700 A CN 110649700A
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- 238000000034 method Methods 0.000 title claims abstract description 10
- 238000004146 energy storage Methods 0.000 claims abstract description 22
- 238000010248 power generation Methods 0.000 claims abstract description 5
- 238000002955 isolation Methods 0.000 abstract description 3
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J9/00—Circuit arrangements for emergency or stand-by power supply, e.g. for emergency lighting
- H02J9/04—Circuit arrangements for emergency or stand-by power supply, e.g. for emergency lighting in which the distribution system is disconnected from the normal source and connected to a standby source
- H02J9/06—Circuit arrangements for emergency or stand-by power supply, e.g. for emergency lighting in which the distribution system is disconnected from the normal source and connected to a standby source with automatic change-over, e.g. UPS systems
- H02J9/061—Circuit arrangements for emergency or stand-by power supply, e.g. for emergency lighting in which the distribution system is disconnected from the normal source and connected to a standby source with automatic change-over, e.g. UPS systems for DC powered loads
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Abstract
The invention discloses a method for preventing a user circuit from transmitting power to a power grid in a reverse direction, which comprises a power supply network and the user circuit with power generation equipment, wherein the user circuit comprises an energy storage device, a grid-connected inverter circuit, a user load and a control circuit; the grid-connected inverter circuit is connected with a power supply network through a power supply line, and a user load is connected to the power supply line; the two current detectors of the control circuit are respectively used for detecting any two items of the inverter current Iinv, the grid current Igrid and the load current Iload; real-time computing
According to the value of Pequ, the output power of the energy storage device is adjusted to enable Pequ to be more than or equal to 0 and less than or equal to Pmax; wherein, T is the work period of the power grid, Pequ is the input active power of the power grid, and Pmax is the set maximum value of the dynamic range of Pequ. The control circuit has small hardware volume and low cost, and the used circuits all work under the isolation safety voltage, thereby having convenient application and flexible use.
Description
[ technical field ]
The invention relates to distributed power generation, in particular to a method for preventing a user circuit from transmitting power to a power grid in a reverse direction.
[ background art ]
The wide application of renewable energy sources such as solar photovoltaic, wind energy and the like effectively relieves the energy crisis and reduces the emission of carbon dioxide. Its inherent volatility also requires the addition of energy storage devices to increase the availability of renewable energy sources. However, when the energy storage device discharges, the electric energy may be reversely fed into the power supply network through the power transmission line, so that the electric energy of the power supply network is disturbed, and meanwhile, when the energy storage device is overhauled, the possibility that the line which is disconnected upstream is electrified may occur, so that the risk is brought to the safe operation of the power grid.
There are two methods to prevent back feeding. One is working in off-grid state, when the energy storage device discharges, the energy transmission to the power grid is stopped because of no power grid access, but the support of the power grid is lacked, and when the user load changes dynamically, the power supply quality is poor; the other is to add a reverse flow prevention device which detects the flow direction of energy in the power grid in real time, and when the energy flowing into the power grid is found, the output of the energy storage device is started to be reduced.
[ summary of the invention ]
The technical problem to be solved by the invention is to provide a method for preventing a user circuit from transmitting power to a power grid in a reverse direction, wherein the method is small in hardware size and low in cost.
In order to solve the technical problems, the invention adopts the technical scheme that the method for preventing the user circuit from reversely transmitting power to the power grid comprises a power supply network and the user circuit with power generation equipment, wherein the user circuit comprises an energy storage device, a grid-connected inverter circuit, a user load and a control circuit; the grid-connected inverter circuit is connected with a power supply network through a power supply line, and a user load is connected to the power supply line; the control circuit comprises two current detectors, the two current detectors are respectively used for detecting any two items of the inversion current Iinv, the grid current Igrid and the load current Iload, and the rest item is obtained by calculation according to the kirchhoff current law; real-time computing
According to the value of Pequ, the output power of the energy storage device is adjusted to enable Pequ to be more than or equal to 0 and less than or equal to Pmax;wherein, T is the work period of the power grid, Pequ is the input active power of the power grid, and Pmax is the set maximum value of the dynamic range of Pequ.
The control circuit has small hardware volume and low cost, and the used circuits all work under the isolation safety voltage, thereby having convenient application and flexible use.
[ description of the drawings ]
The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.
Fig. 1 is a circuit architecture diagram of an embodiment of the present invention.
[ detailed description of the invention ]
An applicable framework of the embodiment of the invention is shown in fig. 1, and comprises a power supply network and a user circuit with power generation equipment, wherein the user circuit comprises an energy storage device, a grid-connected inverter circuit, a user load and a control circuit. The grid-connected inverter circuit is connected with a power supply network through a power supply line, and a user load is connected to the power supply line. The energy storage device discharges through the grid-connected inverter circuit to provide energy for the user load, the power grid is used as supplementary energy of the energy storage device, and when the power of the user load is larger than the energy storage inverter energy, insufficient energy is provided by the power grid to support uninterrupted power supply of the user load.
The control circuit of the invention adopts two current detectors to replace a reverse-flow prevention device, the two current detectors are used for detecting any two items of inversion current Iiinv, grid current Igrid and load current Iload, and the rest one item can be according to kirchhoff current law: i lload ═ Iinv + Igrid are calculated, and fig. 1 illustrates detection of the inverter current Iinv and the load current Iload as an example. Iiv, Iload, and Igrid ═ Iload-Iiv are known. The power factor of the inverter current Iinv generated by the grid-connected inverter circuit can reach 0.99, even under the condition of light load, the power factor can reach 0.95, so that the phase of Iinv can be approximate to the phase of the power grid voltage U, namely: U-R × Iinv, R is a proportionality coefficient of Iinv and U, and since the grid-connected inverter circuit is always output power, R is always positive. According to an active power calculation formula:t is the grid duty cycle, if P>0 means that the power flows in the same direction as the reference direction of the current, if P<0, then indicates that the power flow is opposite to the reference direction of the current. In order to ensure that no energy is supplied to the grid, it is necessary to ensure
Namely, it is
R is positive value, does not affect the positive and negative, so long asThe energy storage device will not deliver energy to the grid. The larger the P value is, the larger the user load energy borne by the power grid is, and the lower the energy storage utilization rate is. In order to improve the energy storage utilization rate, P is controlled to be equal to 0 as far as possible, because Pequ and P are in a linear relation, Pequ is controlled to be 0, Pequ is used as a given value, a Pequ true value is detected in real time, the error between the true value and the given value is calculated to perform loop control, and the error between the true value and the given value is zero by adjusting the output power of the energy storage device.
The invention is used for detecting any two items of inversion current Iiinv, grid current Igrid and load current Iload through two current detectors, and real-time calculation is carried out
The direction of active power in the power grid is judged according to the positive and negative values of the values so as to adjust the output of the energy storage device and ensure that the energy storage device cannot transmit energy to the power grid. In the practical application process, in order to ensure the energy storage utilization rate and simultaneously ensure that no energy flows into the power grid, Pequ is generally equal to or larger than Pmax as a control target, that is, Pequ is equal to or larger than 0 and equal to or smaller than Pmax, where Pequ is the active power input by the power grid, and Pmax is the maximum value of the dynamic range of Pequ.
The above embodiment of the invention does not detect or calculate the true value of the active power of the power grid, but determines the direction of the active power of the power grid through the two current detectors, supports the adjustment of the utilization rate of the stored energy, reduces the cost and the occupied area of hardware, and the used circuits all work under the isolation safety voltage, and have convenient application and flexible use.
Claims (1)
1. A method for preventing a user circuit from transmitting power to a power grid in a reverse direction comprises a power supply network and the user circuit with power generation equipment, wherein the user circuit comprises an energy storage device, a grid-connected inverter circuit, a user load and a control circuit; the grid-connected inverter circuit is connected with a power supply network through a power supply line, and a user load is connected onto the power supply line, and the grid-connected inverter circuit is characterized in that the control circuit comprises two current detectors, the two current detectors are respectively used for detecting any two items of inverter current Iiinv, grid current Igrid and load current Iload, and the rest one item is obtained by calculation according to kirchhoff current law; real-time computingAccording to the value of Pequ, the output power of the energy storage device is adjusted to enable Pequ to be more than or equal to 0 and less than or equal to Pmax; wherein, T is the work period of the power grid, Pequ is the input active power of the power grid, and Pmax is the set maximum value of the dynamic range of Pequ.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201910976294.4A CN110649700A (en) | 2019-10-15 | 2019-10-15 | Method for preventing user circuit from reversely transmitting power to power grid |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201910976294.4A CN110649700A (en) | 2019-10-15 | 2019-10-15 | Method for preventing user circuit from reversely transmitting power to power grid |
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| Publication Number | Publication Date |
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| CN110649700A true CN110649700A (en) | 2020-01-03 |
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| CN201910976294.4A Pending CN110649700A (en) | 2019-10-15 | 2019-10-15 | Method for preventing user circuit from reversely transmitting power to power grid |
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|---|---|---|---|---|
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2019
- 2019-10-15 CN CN201910976294.4A patent/CN110649700A/en active Pending
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