CN114865776A - Spare power automatic switching device and method without switching new energy unit and load and application - Google Patents
Spare power automatic switching device and method without switching new energy unit and load and application Download PDFInfo
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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
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/26—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/04—Circuit arrangements for ac mains or ac distribution networks for connecting networks of the same frequency but supplied from different sources
- H02J3/06—Controlling transfer of power between connected networks; Controlling sharing of load between connected networks
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/12—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load
- H02J3/14—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load by switching loads on to, or off from, network, e.g. progressively balanced loading
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
- H02J3/381—Dispersed generators
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
- H02J3/388—Islanding, i.e. disconnection of local power supply from the network
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
- H02J2300/20—The dispersed energy generation being of renewable origin
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
- H02J2300/40—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation wherein a plurality of decentralised, dispersed or local energy generation technologies are operated simultaneously
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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
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
- Y02B70/30—Systems integrating technologies related to power network operation and communication or information technologies for improving the carbon footprint of the management of residential or tertiary loads, i.e. smart grids as climate change mitigation technology in the buildings sector, including also the last stages of power distribution and the control, monitoring or operating management systems at local level
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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
- Y04—INFORMATION OR COMMUNICATION TECHNOLOGIES HAVING AN IMPACT ON OTHER TECHNOLOGY AREAS
- Y04S—SYSTEMS INTEGRATING TECHNOLOGIES RELATED TO POWER NETWORK OPERATION, COMMUNICATION OR INFORMATION TECHNOLOGIES FOR IMPROVING THE ELECTRICAL POWER GENERATION, TRANSMISSION, DISTRIBUTION, MANAGEMENT OR USAGE, i.e. SMART GRIDS
- Y04S20/00—Management or operation of end-user stationary applications or the last stages of power distribution; Controlling, monitoring or operating thereof
- Y04S20/20—End-user application control systems
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Abstract
The invention discloses a spare power automatic switching device without switching on a new energy machine set and a load, a method and application thereof. And determining the running state of the energy storage device according to the relative relation, starting the energy storage device according to the determined running state after the main supply line is tripped and the new energy source unit and surrounding loads form an island, then putting into a standby line, and finally pushing out the energy storage device to finish the spare power automatic switching. The spare power automatic switching method without switching on the new energy source unit and the load can realize the spare power automatic switching without switching on the new energy source unit and the load and simultaneously reduce the impact current generated by switching on as much as possible, thereby realizing the rapid and safe automatic switching on of the spare power supply.
Description
Technical Field
The invention belongs to the technical field of power system relay protection, and particularly relates to a spare power automatic switching device and method without switching on a new energy unit and a load, and a new energy access station.
Background
With the centralized and distributed large-scale access of large-scale new energy, the wide application of large-capacity multi-loop direct current feed-in feed-out and the like, the action principle, the configuration scheme and the setting principle of the traditional relay protection need to be further improved to adapt to the safe operation requirement of the power electronic power grid. Among them, a standby power supply switching device (referred to as a backup automatic switching device for short) is an important device for recovering the power supply of a system. When the system loses power supply due to faults, the spare power automatic switching device quickly switches the spare power into the system so as to ensure reliable power supply of the system. However, after the new energy is connected to a large system of a power grid in a large scale, the low voltage ride through characteristic of the new energy can cause the voltage of a system working bus when a fault occurs, so that the 'no-voltage' starting condition of the backup power automatic switching device is not met, and the traditional backup power automatic switching device fails.
At present, a spare power automatic switching method for new energy station access is provided, wherein the application number is 201911112750.7 entitled switching method of spare power automatic switching device of new energy power plant grid-connected substation, the switching method of the spare power automatic switching device of the new energy power plant grid-connected substation provides a method for establishing a cause-effect relationship matrix among internal elements of the new energy power plant grid-connected substation and the like to judge the island operation state of the new energy power plant grid-connected substation; and switching the spare power automatic switching device according to the island operation state. Although the reliability of switching the spare power automatic switching device of the new energy power plant grid-connected substation can be improved, the method needs to cut off all new energy stations, and great economic loss can be caused. The application number 202011279547.1 entitled "tandem spare power automatic switching device with new energy" further provides that a tandem spare power automatic switching device is arranged at each power station in a matched manner, so that the off-grid time of the new energy power station from the voltage loss of a local power station to the power supply of a remote power station is reduced, part of important load is brought to the new energy power station during the power failure, and the power failure area is reduced. However, the method aims to match the output power of the new energy power station with the load power, and when the load is larger or the output power of the new energy is larger, part of the load or the new energy station is still cut off to realize power matching. The application number 201811123557.9 is called 'a standby power supply automatic switching method suitable for a distributed new energy power grid', and provides a method that after a main supply line is disconnected, the frequency difference between incoming line voltage and bus residual voltage and the voltage angle difference are detected, and if the phase angle difference and the frequency difference do not exceed a set value, a standby line is switched to complete standby automatic switching. Although the method theoretically realizes spare power automatic switching without cutting off new energy and load, in actual operation, when the power difference between the new energy and the load in an island is large, the frequency and the voltage phase angle of the island side change rapidly, the synchronous capturing is almost impossible, and finally all new energy stations still need to be cut off. An article of 'novel spare power automatic switching scheme adaptive to new energy access' of authors such as zhengtao, and the like, proposes a method for performing spare line switching by firstly switching energy dissipation resistors to absorb surplus power when power generated by new energy is greater than load consumption power after island operation. Although the method realizes the spare power automatic switching without cutting off the new energy station, when the load power of an island is higher than the power generated by the new energy, the method still needs to cut off partial load to realize the spare power automatic switching. Therefore, it is desirable to provide a backup power automatic switching method that can complete backup power automatic switching without cutting off any new energy unit and load.
Disclosure of Invention
In order to overcome the defects in the prior art, the invention provides the spare power automatic switching method without switching on a new energy unit and a load, so that the spare power automatic switching can be completed quickly and safely under the condition of not switching off the new energy unit and the load completely, and the aim of limiting the switching-on impact current is fulfilled.
In order to achieve the above object, the present invention provides a spare power automatic switching device without new energy source unit and load, and its technical scheme is as follows:
a spare power automatic switching device without switching new energy machine set and load is characterized in that: the new energy is connected to a bus n through an outlet breaker BRK5, a load 1 is connected to the bus n through an outlet breaker BRK6, a current transformer is arranged on the bus n, and the bus n is connected to a bus m through a bus connection breaker; when the new energy source unit operates normally, a power grid is connected with a bus m through a main supply line, at the moment, circuit breakers BRK1 and BRK2 on the main supply line are both in a closing state, a voltage transformer and a current transformer are arranged on the bus m, and an energy storage device is directly connected with the bus m; the power grid is connected with a bus n through a standby line, and circuit breakers BRK3 and BRK4 on the standby line are in an opening state under normal operation.
The invention discloses a spare power automatic switching method without switching on a new energy unit and a load, which is characterized by comprising the following steps: when the new energy unit is in normal operation, a voltage transformer and a current transformer in the bus m measure the voltage of the bus m and the current flowing through the main supply line, the current flow is calculated in the data storage element according to the voltage and the current, and the current flow is stored in the data storage element according to the time sequence;
the opening and closing state of the circuit breaker is judged by detecting the position information of the auxiliary contact points of the circuit breakers BRK1 and BRK2 on the main supply line, and the current flowing through the main supply line is detected through a current transformer;
when the breaker is in a brake-off state and the current transformer detects that the current is lower than a no-current threshold value, the main supply circuit is considered to be disconnected at the moment, and a main supply circuit disconnection signal and a tidal current signal are sent to the energy storage device through the signal transmitting device; after the energy storage device receives the signals through the signal receiving device, selecting a charge-discharge state to be adopted according to a tide signal value in the signals and starting the charge-discharge state; after the energy storage device is started successfully, a successful starting signal is sent to the spare power automatic switching device, and the spare power automatic switching device closes the circuit breakers BRK3 and BRK4 in the spare line in a delayed mode and switches into the spare line; and finally, detecting auxiliary contacts of the BRK3 and the BRK4 in the spare line, wherein when the position information of the auxiliary contacts of the circuit breaker is in a closed position and the current transformer on the n bus detects that the current is higher than a no-current threshold, the spare power automatic switching device generates a spare power automatic switching success signal to the energy storage device, and the energy storage device quits the operation after receiving the signal through the signal receiving device.
The invention discloses a spare power automatic switching method without switching on a new energy unit and a load, which comprises the following steps:
the method comprises the following steps: circuit breaker operating state identification
Detecting the opening and closing states of the main supply line circuit breakers BRK1 and BRK2, when the position information of an auxiliary contact of the circuit breakers is jump position, if a current transformer on the main supply line detects that the current is lower than a no-current threshold value at the same time, determining that the main supply line circuit breakers BRK1 and BRK2 are in the opening state, and starting the spare power automatic switching device at the moment; if the current transformer on the main supply line detects that the current is higher than the no-current threshold value, the position of an auxiliary contact of the circuit breaker is considered to be wrong, warning information is sent out, and the spare power automatic switching device is locked at the moment;
step two: detecting the size and direction of the tidal current on the main supply line
When the running states of the main supply line circuit breakers BRK1 and BRK2 are identified as the brake-separating state, starting the spare power automatic switching device and starting to detect the main supply line current; the new energy and the load form an island system. In an island condition, the power generated by the new energy source is different from the power consumed by the load, so that surplus power or shortage power exists in an island system;
step three: the spare power automatic switching device transmits the obtained tide information to the energy storage device;
step four: the energy storage device analyzes the tidal current value and starts;
step five: the spare power automatic switching device starts a spare circuit breaker to switch on;
step six: and (4) the energy storage quits the operation, and the spare power automatic switching is completed.
The invention also discloses a station for new energy access, which is characterized in that: the system adopts the spare power automatic switching method without switching the new energy machine set and the load to realize the control of the station.
Due to the adoption of the technical method, the invention has the following technical advantages:
a) compared with the traditional spare power automatic switching method, the method adopts the additional energy storage device to realize the spare power automatic switching, the input is fast, and the system can be quickly recovered and stabilized.
b) The method can completely avoid switching on the new energy unit and load while limiting the switching-on impact current, reduce the user loss and increase the utilization rate of the new energy unit.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed in the embodiments will be briefly described 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 without creative efforts.
FIG. 1 is a schematic diagram of a backup power automatic switching line;
FIG. 2 is an active power control loop of a doubly-fed wind turbine;
FIG. 3 is a graph showing the frequency change when the new energy output is unequal to the load power after the main supply line is disconnected; wherein, fig. 3(a) is a graph of frequency change of an island system when the new energy output is larger than the load power; FIG. 3(b) is a diagram of frequency change of an island system when the new energy output is smaller than the load power;
FIG. 4 is a three-phase voltage change diagram when the new energy output and the load power are not equal after the main supply line is disconnected; wherein, fig. 3(a) is a three-phase voltage change diagram when the new energy output is larger than the load power; FIG. 3(b) is a graph of the change of three-phase voltage when the new energy output is less than the load power;
FIG. 5 shows three-phase currents of a main power supply line and a standby line when the new energy output is greater than the load power; fig. 5(a) shows three-phase current of the main supply circuit, and fig. 5(b) and (c) show three-phase current of the standby circuit when the energy storage is not started and the energy storage is started respectively. (the current is per unit value p.u, and the current of the main supply line is taken as the reference when in normal operation);
fig. 6 shows three-phase currents of the main supply line and the standby line when the new energy output is smaller than the load power. Fig. 6(a) shows three-phase current of the main supply line, and fig. 6(b) and (c) show three-phase current of the standby line when the energy storage is not started and the energy storage is started respectively. (the current is per unit value p.u, and the current of the main supply line is taken as the reference when in normal operation);
fig. 7 is a flow chart of the fast backup power automatic switching method without switching on the new energy unit according to the present invention.
Detailed Description
The technical solution in the embodiments of the present invention is clearly and completely described below by the embodiments and with reference to the drawings. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. 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 invention aims to provide a quick spare power automatic switching scheme without switching on a new energy source unit, so that quick spare power automatic switching can be realized without switching off the new energy source unit, and simultaneously, impact current generated by switching on is reduced as much as possible, so that quick and safe automatic switching on of a spare power supply is realized.
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.
Description of the system architecture:
fig. 1 shows a structural diagram of a power supply system, in a conventional case, a main supply line is in a conducting state (that is, circuit breakers BRK1 and BRK2 are in a closing state), and a new energy source and a load 1 are connected to a power grid through the main supply line.
In order to prevent the relay protection device from acting to disconnect the circuit breakers BRK1 and BRK2 due to the fault of the main supply line, so that the new energy and the load 1 form an island operation state, a line is generally provided, and when the main supply line is disconnected, a backup automatic switching device (a backup automatic switching device) acts to switch on the circuit breakers BRK3 and BRK4, so as to recover the power supply of an island system.
A spare power automatic switching device without switching new energy unit and load is characterized in that: the new energy is connected to a bus n through an outlet breaker BRK5, a load 1 is connected to the bus n through an outlet breaker BRK6, a current transformer is arranged on the bus n, and the bus n is connected to a bus m through a bus connection breaker; when the new energy source unit normally operates, a power grid is connected with a bus m through a main supply line, circuit breakers BRK1 and BRK2 on the main supply line are both in a closing state, a voltage transformer and a current transformer are arranged on the bus m, and an energy storage device is directly connected with the bus m; the power grid is connected with a bus n through a standby line, and circuit breakers BRK3 and BRK4 on the standby line are in a brake-separating state under normal operation;
when the new energy unit is in normal operation, a voltage transformer and a current transformer in the bus m measure the voltage of the bus m and the current flowing through the main supply line, the current flow is calculated in the data storage element according to the voltage and the current, and the current flow is stored in the data storage element according to the time sequence;
the opening and closing state of the circuit breaker is judged by detecting the position information of the auxiliary contacts of the circuit breakers BRK1 and BRK2 on the main supply line, and the current flowing through the main supply line is detected through a current transformer;
when the breaker is in a brake-off state and the current transformer detects that the current is lower than a no-current threshold value, the main supply circuit is considered to be disconnected at the moment, and a main supply circuit disconnection signal and a tidal current signal are sent to the energy storage device through the signal transmitting device; after the energy storage device receives the signals through the signal receiving device, selecting a charge-discharge state to be adopted according to a tide signal value in the signals and starting the charge-discharge state; after the energy storage device is started successfully, a successful starting signal is sent to the spare power automatic switching device, and the spare power automatic switching device closes the circuit breakers BRK3 and BRK4 in the spare line in a delayed mode and switches into the spare line; and finally, detecting auxiliary contacts of the BRK3 and the BRK4 in the spare line, wherein when the position information of the auxiliary contacts of the circuit breaker is in a closed position and the current transformer on the n bus detects that the current is higher than a no-current threshold, the spare power automatic switching device generates a spare power automatic switching success signal to the energy storage device, and the energy storage device quits the operation after receiving the signal through the signal receiving device.
The spare power automatic switching method without switching new energy unit and load includes the following steps:
the method comprises the following steps: circuit breaker operating state identification
Detecting states of circuit breakers BRK1 and BRK2 of a main supply line, and when auxiliary contact position information of the circuit breakers is jumping, if a current transformer on the main supply line simultaneously detects that current is lower than a no-current threshold value at the moment, determining that the circuit breakers are in a brake-separating state, and starting a spare power automatic switching device at the moment; and if the current transformer on the main supply line detects that the current is higher than the no-current threshold value, the position of the auxiliary contact of the circuit breaker is considered to be wrong, warning information is sent out, and the spare power automatic switching device is locked at the moment.
Step two: detecting the size and direction of the tidal current on the main supply line
And when the operating state of the circuit breaker is identified as the opening state, starting the spare power automatic switching device and starting to detect the power flow of the main supply line.
The new energy and the load form an island system. In an island condition, the new energy source generates power and the load consumes power, and surplus power or shortage power exists in an island system. And in the power system, the relationship between power and frequency is as follows:
ΔP＝Δf×K S
where Δ P represents surplus or deficit power (surplus is positive and deficit is negative), Δ f represents frequency variation, K s Representing the unit regulated power of the system. As shown in fig. 3(a), (b), when the system has a surplus or shortage of power, the system frequency changes.
The power surplus has an influence on the voltage level of the island system at the same time. Taking the most representative doubly-fed wind turbine in new energy as an example, the internal active power control loop is shown in fig. 2, where ω is r For real-time rotation speed of the fan, MPPT is maximum power point tracking control, P ref Is an active power reference value, P ce For measuring the real-time output power of the fan, PI is proportional-integral controller i rdref Reference value of J-axis current component for rotor current under dq-axis transformation, i rd As measured fan d-axis current, ω r σL r For a voltage compensation term, U rd Is the d-axis component of the rotor voltage.
When the surplus or the shortage of power occurs, the rated power reference value P set by the fan ref Actual output power P of new energy of island system ce A difference value occurs, and the rotor voltage U is finally enabled to be in a PI control link rd And the voltage generated by the new energy source is changed. In the island system, only the new energy source supplies power, so that the voltage change generated by the new energy source can cause the voltage change of the island system.
As shown in fig. 4(a) and (b), after the main supply line is disconnected, the frequency and voltage level of the islanding system may change due to the power imbalance of the islanding system. Therefore, a specific value of the island system power surplus or shortage needs to be obtained firstly.
The distribution of the general load is more dispersed, so that the difference between the output power directly passing through the new energy and the current load power is not advisable. Considering that the tidal current flowing through the main supply line is the difference value between the output power of the fan and the load power, and considering that the output power of the new energy and the load power cannot be suddenly changed in a short time, the tidal current flowing through the main supply line before the formation of the island (namely before the disconnection of the main supply line) is measured to be used as a specific numerical value of the surplus or the shortage of the system power in the island at the moment, and the direction of the tidal current determines whether the system power in the island is in a surplus or shortage state.
The main supply line voltage and current are represented as:
where t represents time, U (t) represents a function of voltage over time, i (t) represents a function of current over time, n represents the nth harmonic, and n representing the effective value of the n-th harmonic voltage, I n Representing the effective value of the nth harmonic current) phi n Representing the phase difference between the nth harmonic voltage and the current; omega n Representing the angular frequency, ψ, of the n-th harmonic n Representing the initial phase angle of n-th harmonic voltage and current, the active power part of the main supply line tide is as follows:
typically, the power in the system is primarily the fundamental (i.e., n is 1, fundamental frequency f) 1 50HZ, T ═ 0.02s) power, so a current transformer and a voltage transformer can be installed at the bus m, assuming a sampling rate f k ，u(t g ),i(t g ) For each sampling point t g And (3) measuring the lower voltage and current, wherein the active power measured value P is as follows:
when power flows to the power grid from the bus m, namely the output power of the new energy is greater than the load power, the measured value of the active power is a positive value. When power flows from the power grid to the bus m, namely the output power of the new energy is smaller than the load power, the active power measured value is a negative value.
In order to obtain the power flow flowing through the main supply line before the island is formed, the obtained active power measured value can be stored through a data storage element, and after the main supply line is disconnected, the last data before the disconnection is taken as a power imbalance numerical value in the island.
Step three: the spare power automatic switching device transmits the obtained tide information to the energy storage device;
step four: the energy storage device analyzes the tidal current value and starts
And after the spare power automatic switching device transmits the tidal current information f to the energy storage device, the energy storage device analyzes the tidal current information f. The charging and discharging power depends on the specific numerical value of the tide f, in order to prevent the energy storage from frequently changing the charging and discharging state, a power critical value P is selected, and the f numerical value is divided into 3 intervals:
(1) tidal current I area (energy storage discharge area): the interval is f is less than or equal to-P l Therefore, the island system is considered to have the shortage power, the energy storage and discharge are performed to make up for the shortage power of the island system, and the energy storage and discharge power is the tidal current numerical value f.
(2) Tidal current area II (energy storage inactive interval): the interval is-P l ＜f＜P l Therefore, the island system is not considered to have a large power imbalance phenomenon, and the energy storage does not act at the moment.
(3) Tidal current III region (energy storage charging interval): the interval is f ≧ P l Therefore, surplus power exists in the island system, the energy storage charging is used for absorbing the surplus power of the island system, and the energy storage charging power is still the tidal current numerical value f.
Critical power value P l And the starting time of stored energy and the rated power P of new energy N It is related. Considering main supplyUnder the condition that the time for transmitting the line tide signal to the energy storage device and completing analysis and judgment is 20ms, a large number of simulations show that the critical power value P is l Can be selected as the rated power P of new energy N 0.05 times of the total weight of the powder.
Step five: switching-on of spare circuit breaker for starting of spare automatic switching device
After the energy storage starting strategy is completed, the BRK3 and the BRK4 of the standby line circuit breakers are switched on after the time delay of 40 ms.
Step six: the energy storage quits the operation to finish the spare power automatic switching
And detecting the opening and closing states of the BRK1 and the BRK2 of the standby circuit breakers. When the auxiliary contact position information of the circuit breaker is in a closed position, if the current mutual inductor on the standby circuit detects that the current is higher than a no-current threshold value at the same time, the circuit breakers BRK1 and BRK2 of the main supply circuit are in a closed state, the spare power automatic switching is successful, a successful spare power automatic switching signal is sent to the energy storage device through the spare power automatic switching device, and the energy storage device quits the operation after receiving the signal; if the current transformer on the standby line detects that the current is lower than the no-current threshold value, the position of the auxiliary contact of the circuit breaker is considered to be wrong, warning information is sent out, and the standby automatic switching device is locked at the moment.
Fig. 5 shows that in the system structure shown in fig. 1, when the main supply line is disconnected (i.e., the BRK1 and the BRK2 are disconnected), the new energy and the load form an island, and the output power of the new energy is greater than the load power at this time, the backup power automatic switching method respectively adopts current waveforms on the backup line when the energy storage is started and not started (where the current unit p.u. is a per unit value, and the current flowing through the line in normal operation is a reference value). Fig. 5(a) shows the main supply line current waveform at 0.4s indicating that the main supply line is open and islanding. And fig. 5(b) shows that the energy storage is not started, the standby line is directly switched into through the automatic standby switching device at 0.46s, and the impact current flowing on the standby line at the moment can be seen to be as high as 10.1 p.u.. The manner of starting energy storage charging to absorb surplus power and then putting the energy storage charging into the standby line is shown in fig. 5(c), and at the moment, the impact current flowing through the standby line is only 1.3p.u., so that grid connection conditions of a power grid are met.
Fig. 6 shows that in the system structure shown in fig. 1, when the main supply line is disconnected (i.e., the BRK1 and the BRK2 are disconnected), the new energy and the load form an island, and the output power of the new energy is smaller than the load power at this time, the backup power automatic switching method respectively adopts current waveforms on the backup line when the energy storage is started and not started (where the current unit p.u. is a per unit value, and the current flowing through the line in normal operation is a reference value). Fig. 6(a) the main supply line current waveform shows that at 0.4s the main supply line is open and islanding. And fig. 6(b) shows that the energy storage is not started, the standby line is directly switched into through the automatic backup switching device at 0.46s, and the impact current flowing on the standby line at the moment can be seen to be 3.3 p.u.. The manner of starting the energy storage and discharging to supplement the shortage power and then putting the power into the standby line is shown in fig. 6(c), and at the moment, the impact current flowing through the standby line is only 1.01p.u., so that the grid-connected condition of the power grid is met.
According to the simulation analysis, the invention applies the energy storage to carry out the spare power automatic switching, can effectively limit the impact current generated by the spare line, and does not cut out a new energy unit and a load at all.
The foregoing shows and describes the general principles, essential features, and advantages of the invention. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are merely illustrative of the principles of the invention, but that various changes and modifications may be made without departing from the spirit and scope of the invention, which fall within the scope of the invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.
Claims (10)
1. A spare power automatic switching device without switching new energy unit and load is characterized in that: the new energy is connected to a bus n through an outlet breaker BRK5, a load 1 is connected to the bus n through an outlet breaker BRK6, a current transformer is arranged on the bus n, and the bus n is connected to a bus m through a bus connection breaker; when the new energy source unit normally operates, a power grid is connected with a bus m through a main supply line, circuit breakers BRK1 and BRK2 on the main supply line are both in a closing state, a voltage transformer and a current transformer are arranged on the bus m, and an energy storage device is directly connected with the bus m; the power grid is connected with a bus n through a standby line, and circuit breakers BRK3 and BRK4 on the standby line are in an opening state under normal operation.
2. A spare power automatic switching method without switching new energy units and loads is characterized in that: when the new energy unit is in normal operation, a voltage transformer and a current transformer in the bus m measure the voltage of the bus m and the current flowing through the main supply line, and the load flow is calculated according to the measured voltage and current and stored in a data storage element according to the time sequence;
the opening and closing states of the circuit breakers BRK1 and BRK2 are judged by detecting the position information of the auxiliary contact points of the circuit breakers BRK1 and BRK2 on the main supply line, and the current flowing through the main supply line is detected through a current transformer;
when the circuit breakers BRK1 and BRK2 are in the opening state and the current transformer detects that the current is lower than the no-current threshold value, the main supply line is considered to be disconnected at the moment, and a main supply line disconnection signal and a power flow signal are sent to the energy storage device through the signal transmitting device; after the energy storage device receives the signals through the signal receiving device, selecting a charge-discharge state to be adopted according to a tide signal value in the signals and starting the charge-discharge state; after the energy storage device is started successfully, a successful starting signal is sent to the spare power automatic switching device, and the spare power automatic switching device closes the circuit breakers BRK3 and BRK4 in the spare line in a delayed mode and switches into the spare line; and finally, detecting auxiliary contacts of the circuit breakers BRK3 and BRK4 in the spare line, wherein when the position information of the auxiliary contacts of the circuit breakers BRK3 and BRK4 is in a closed position and the current transformer on the bus n detects that the current is higher than a no-current threshold, the spare power automatic switching device generates a spare power automatic switching success signal to the energy storage device, and the energy storage device quits the operation after receiving the signal through the signal receiving device.
3. The spare power automatic switching method without switching on the energy unit and the load according to claim 2, characterized by comprising the following steps of:
the method comprises the following steps: circuit breaker operating state identification
Detecting the opening and closing states of the main supply line circuit breakers BRK1 and BRK2, when the position information of an auxiliary contact of the circuit breakers is jump position, if a current transformer on the main supply line detects that the current is lower than a no-current threshold value at the same time, determining that the main supply line circuit breakers BRK1 and BRK2 are in the opening state, and starting the spare power automatic switching device at the moment; if the current transformer on the main supply line detects that the current is higher than the no-current threshold value, the position of an auxiliary contact of the circuit breaker is considered to be wrong, warning information is sent out, and the spare power automatic switching device is locked at the moment;
step two: detecting the size and direction of the tidal current on the main supply line
When the running states of the main supply line circuit breakers BRK1 and BRK2 are identified as the brake-separating state, starting the spare power automatic switching device and starting to detect the main supply line current; the new energy and the load form an island system. In an island condition, the power generated by the new energy source is different from the power consumed by the load, so that surplus power or shortage power exists in an island system;
step three: the spare power automatic switching device transmits the obtained tide information to the energy storage device;
step four: the energy storage device analyzes the power flow value and starts;
step five: the spare power automatic switching device starts a spare circuit breaker to switch on;
step six: and (4) the energy storage quits the operation, and the spare power automatic switching is completed.
4. The backup power automatic switching method without switching on the energy source unit and the load according to claim 2, characterized in that: the step 2 further comprises the following steps: the power versus frequency relationship in an electrical power system is:
ΔP＝Δf×K S
where Δ P represents surplus or deficit power, Δ f represents frequency variation, K s Representing the unit regulated power of the system.
5. The spare power automatic switching method without switching on the new energy unit and the load according to claim 4, wherein: the step 2 further comprises the following steps:
when the surplus or the shortage of power occurs, the rated power reference value P set by the fan ref Actual output of new energy of island systemPower P ce A difference value occurs, and the rotor voltage U is finally enabled to be in a PI control link rd And the voltage generated by the new energy source is changed.
6. The spare power automatic switching method without switching on the new energy unit and the load according to claim 3, wherein: the step 2 further comprises the following steps:
the main supply line voltage and current are represented as:
where t represents time, U (t) represents a function of voltage over time, i (t) represents a function of current over time, n represents the nth harmonic, and U n Representing the effective value of the n-th harmonic voltage, I n Represents the effective value of the n-th harmonic current; phi n Representing the phase difference between the nth harmonic voltage and the current; omega n Representing the angular frequency, ψ, of the n-th harmonic n Representing the initial phase angle of n-th harmonic voltage and current, the active power part of the main supply line tide is as follows:
7. the spare power automatic switching method without switching on the new energy unit and the load according to claim 3, wherein: the step 4 further comprises the following steps: after the spare power automatic switching device transmits the tidal current information f to the energy storage device, the energy storage device analyzes the tidal current information f; the charging and discharging power depends on the specific value of the tide f, and in order to prevent the frequent change of the charging and discharging state of the stored energy, a power critical value P is selected l The f-number is divided into 3 intervals.
8. The backup power automatic switching method without switching new energy source unit and load according to claim 7, characterized in that: the 3 intervals are:
(1) tidal current I area (energy storage and discharge area): the interval is that f is less than or equal to-P l Therefore, the island system is considered to have the shortage power, the energy storage and discharge are carried out to make up the shortage power of the island system at the moment, and the energy storage and discharge power is a tidal current numerical value f;
(2) tidal current II area (energy storage non-operation interval): the interval is-P l <f<P l Therefore, the island system is not considered to have a large power imbalance phenomenon, and the stored energy does not act at the moment;
(3) tidal current III area (energy storage charging area): the interval is f ≧ P l Therefore, surplus power exists in the island system, the energy storage charging is used for absorbing the surplus power of the island system, and the energy storage charging power is still the tidal current numerical value f.
9. The backup power automatic switching method without switching on the energy unit and the load according to claim 3, characterized in that: the stored energy is charged and discharged to ensure the power balance of an island system, so that the change of the electric quantity of a grid connection point is limited, the slip voltage of the circuit breaker is reduced during the spare power automatic switching action, and the switching-on impact current is reduced.
10. New energy access station, characterized by: the system comprises a spare power automatic switching control system without switching on the new energy source unit and the load, and the system adopts the spare power automatic switching method without switching on the new energy source unit and the load according to any one of claims 2 to 9 to realize the control of the station.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN108539776A (en) * | 2018-05-10 | 2018-09-14 | 国网江苏省电力有限公司徐州供电分公司 | One kind being used for low pressure flexibility supplying power allocation system coordination control method |
| CN112366809A (en) * | 2020-11-16 | 2021-02-12 | 国家电网有限公司 | Pilot plant spare power automatic switching device with new forms of energy |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN108539776A (en) * | 2018-05-10 | 2018-09-14 | 国网江苏省电力有限公司徐州供电分公司 | One kind being used for low pressure flexibility supplying power allocation system coordination control method |
| CN112366809A (en) * | 2020-11-16 | 2021-02-12 | 国家电网有限公司 | Pilot plant spare power automatic switching device with new forms of energy |
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