CN110474301B - Frequency and voltage protection method for power grid side energy storage power station - Google Patents
Frequency and voltage protection method for power grid side energy storage power station Download PDFInfo
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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
- H02H7/18—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for batteries; for accumulators
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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
- H02J3/28—Arrangements for balancing of the load in a network by storage of energy
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Abstract
The invention provides a frequency and voltage protection method for a power grid side energy storage power station, which comprises the following steps: step 1: introducing a three-phase current of a grid connection point into control protection equipment; step 2: the frequency voltage protection action logic of the control protection equipment is modified, three-phase alternating current is introduced into the frequency voltage protection equipment, and the active and reactive power blocking function output by the energy storage station is introduced into the frequency voltage protection logic, so that more slave protection systems are protected by frequency voltage and can be triggered to act correctly in time.
Description
Technical Field
The invention relates to the technical field of power grid side battery energy storage power stations, in particular to a power grid side energy storage power station frequency and voltage protection method.
Background
The energy storage system has the capability of time-space migration of power and energy, is an effective measure for solving the inherent problems of intermittent new energy power output fluctuation, intermittence and the like, and is rapidly developed along with the wide popularization and application of new energy technologies such as wind power generation, photovoltaic power generation and the like. Compared with energy storage modes such as a flywheel, pumped storage, compressed air, a super capacitor and the like, the battery energy storage power station has the advantages of high energy storage density, flexible site selection, convenience in installation, capability of running smoothly and stably in four quadrants and the like, and has a small construction scale at both the power supply side and the load side in the domestic wide construction stage. The power grid side battery energy storage power station has the functions of participating in peak clipping and valley filling, frequency adjustment, reactive power support, emergency control and the like of a power grid, and the flexibility, stability, economy and cleanliness of system operation can be effectively improved after large-scale construction.
Independent frequency voltage protection equipment is configured in the battery energy storage power stations on the power grid side, and safe and stable operation of a power system is expected to be supported through quick response of the energy storage stations when system voltage and frequency are abnormal. However, the energy storage station has dual attributes of power supply and load, a frequency and voltage control device adapted to the energy storage station on the power grid side is not on the market, the frequency and voltage control protection device assembled in the energy storage station cannot monitor the running state of the energy storage station at present, and the situations that the energy storage station cuts off the energy storage station when the system frequency is low while the energy storage station discharges to further deteriorate the system frequency and cuts off the energy storage station when the system voltage is high while the energy storage station absorbs reactive power may occur. In other words, the frequency and voltage stabilization control device configured in the energy storage station cannot really perform the emergency support function of the near-zone system, so that the form is closer to that of disconnecting the tie line when a frequency or voltage stabilization accident occurs in the power system, and the isolation accident system protects the safety of the energy storage station equipment.
In order to avoid the error response of the energy storage station to deteriorate the system running state when the system is in fault and fully play the technical performance of the frequency voltage protection equipment, the invention provides a frequency voltage protection scheme of the energy storage power station on the power grid side.
Disclosure of Invention
In order to avoid the error response of the energy storage station in system failure to deteriorate the system running state and fully exert the technical performance of the frequency voltage protection equipment, the invention provides a frequency voltage protection method of the power grid side energy storage power station.
According to one aspect of the invention, a frequency and voltage protection method for a power grid side energy storage power station is provided, which comprises the following steps:
step 1: introducing a three-phase current of a grid connection point into control protection equipment;
step 2: modifying the frequency voltage protection action logic of the control protection equipment, calculating the magnitude and direction of active power and reactive power of a line according to the three-phase current of the grid-connected point, and judging that the active power output by the energy storage station to the system is negative before the action due to low frequency; before the action due to high frequency, the energy storage station needs to judge that the active power output to the system is positive; before the system operates due to low voltage, the energy storage station needs to judge that the reactive power output to the system is negative; before the system operates due to high voltage, the energy storage station needs to judge that the reactive power output to the system is positive.
Further, the detailed steps of step 1 include:
step 1-1: expanding the capacity of a sampling board card of the frequency-voltage protection equipment to enable the sampling board card to support at least one grid-connected point three-phase voltage and one grid-connected point three-phase current sampling capacity;
step 1-2: modifying the sampling display of the frequency-voltage protection equipment, and increasing the amplitude and phase display, active and reactive vector display of the three-phase current of the outgoing line grid-connected point on the basis of the original analog quantity display;
step 1-3: a connecting line between a low-voltage bus of the energy storage station and an electric power system is defined as an outgoing line, and a connecting line between the low-voltage bus of the energy storage station and an in-station energy storage converter is defined as an incoming line;
step 1-4: connecting the grid-connected point three-phase current of each outgoing line into a control protection device, and if the outgoing line switch cabinet is provided with a standby independent protection level CT winding, connecting the CT winding into the control protection device by laying a cable; if the standby independent protection CT winding is not available, switching from other screen cabinets can be considered, but the secondary load of the current loop is ensured to meet the requirement on the premise;
step 1-5: the grid side battery energy storage power station is composed of a plurality of energy storage converters, each energy storage converter is distributed to different low-voltage bus sections in the station, each bus section is provided with independent frequency and voltage protection equipment, and when three-phase currents of grid-connected points are accessed, power calculation and action measure errors caused by confusion of the three-phase currents of different outgoing lines are avoided.
Further, the detailed steps of step 2 include:
step 2-1: modifying a program in the control protection equipment, and increasing the calculation of the active power and the calculation of the reactive power of the outgoing line;
step 2-2: the outgoing line power direction is specified, when the energy storage power station outputs active/reactive power to the power system, the active/reactive power of the outgoing line is judged to be positive, otherwise, the active/reactive power of the outgoing line is judged to be negative;
step 2-3: when the control protection equipment monitors that the system frequency is low, and simultaneously judges that the active power of the outlet wire is negative, the outlet wire jumping switch is operated in turns, and the frequency of the support system is recovered;
step 2-4: when the control protection equipment monitors that the frequency drop amplitude of the system is large, the change rate df/dt of the frequency along with the time exceeds a fixed value, and meanwhile, the active power of the outgoing line is judged to be negative, the control protection equipment immediately acts to jump off all incoming lines on the corresponding low-voltage bus;
step 2-5: when the control protection equipment monitors that the system frequency is higher, and simultaneously judges that the active power of the outgoing line is positive, the outgoing line jumping switch is operated in turns, and the frequency of the system is restored;
step 2-6: when the control protection equipment monitors that the rising amplitude of the system frequency is large, the change rate df/dt of the frequency along with the time exceeds a fixed value, and meanwhile, the active power of the outgoing line is judged to be positive, the control protection equipment immediately acts to jump off all incoming lines on the corresponding low-voltage bus;
step 2-7: when the control protection equipment monitors that the system voltage is low, and simultaneously judges that the reactive power of the outlet wire is negative, the outlet wire jumping switch is operated in turns to support the system voltage recovery;
step 2-8: when the control protection equipment monitors that the voltage drop amplitude of the system is large, the change rate du/dt of the voltage along with the time exceeds a fixed value, and meanwhile, the reactive power of the outgoing line is judged to be negative, the control protection equipment immediately acts to trip off all incoming lines on the corresponding low-voltage bus;
step 2-9: when the control protection equipment monitors that the system voltage is higher, and simultaneously judges that the reactive power of the outgoing line is positive, the outgoing line is tripped into the line switch by the action of the control protection equipment in turns, and the voltage of the system is supported to be recovered;
step 2-10: when the control protection equipment monitors that the rising amplitude of the system voltage is large, the change rate du/dt of the voltage along with the time exceeds a fixed value, and meanwhile, the reactive power of the outgoing line is judged to be positive, the control protection equipment immediately acts to jump off all incoming lines on the corresponding low-voltage bus.
Further, the step 2-3 to the step 2-10 are executed in parallel.
In another aspect, the present invention further discloses a system for protecting frequency and voltage of a power grid side energy storage power station, including:
at least one processor; and
at least one memory communicatively coupled to the processor, wherein:
the memory stores program instructions executable by the processor, the processor invoking the program instructions to perform a protection method as claimed in any one of the preceding claims.
In another aspect, the invention also discloses a non-transitory computer-readable storage medium storing computer instructions for causing the computer to perform the protection method according to any one of the above.
The invention has the advantages that the frequency and voltage protection method for the energy storage power station at the power grid side is provided, and the method can fully realize the quick response characteristic of the energy storage station so as to support the stable operation of the power grid. Therefore, the invention provides that measurement of grid-connected three-phase current is introduced, active and reactive power blocking logic is added in frequency and voltage protection logic, and positive and negative of active and reactive power are judged to perform corresponding protection actions. Specifically, before the system acts due to low frequency, the energy storage station needs to judge that the output active power to the system is negative; before the action due to high frequency, the energy storage station needs to judge that the output active power to the system is positive; before the system operates due to low voltage, the energy storage station needs to judge that the output reactive power of the system is negative; before the action of high voltage, the output of reactive power from the energy storage station to the system needs to be judged to be positive, the power flow direction of a grid-connected point is considered in the logic judgment, the safe and stable operation of the support system is really realized when the voltage and the frequency of a system in a near area are abnormal, the situations that the frequency of the system is further deteriorated when the frequency of the energy storage station is cut off when the frequency of the system is low while the energy storage station discharges and the voltage of the system is further deteriorated when the voltage of the system is high while the energy storage station absorbs reactive power can be avoided, and the protection method is particularly suitable for being used in a power grid side energy storage power station with the dual properties of a power supply and a load.
Drawings
FIG. 1 is a schematic diagram of a low-voltage bus connection in a power grid energy storage station according to the present invention;
fig. 2 is a schematic diagram of an active and reactive power blocking logic of the power grid side energy storage power station frequency and voltage protection method of the present invention.
Detailed Description
The present invention will be described more fully hereinafter with reference to the accompanying drawings and examples, in which the technical problems and advantages of the present invention are solved, wherein the described examples are only intended to facilitate the understanding of the present invention, and are not to be construed as limiting in any way.
The grid side battery energy storage power station uses a battery stack as an energy storage carrier, adopts a Pulse Width Modulation (PWM) conversion technology to realize four-quadrant operation, and a core device for power conversion and transmission is an Insulated Gate Bipolar Transistor (IGBT), and the turn-off and the turn-on of the power conversion and transmission can be flexibly controlled by triggering pulses. Due to limitations of IGBT capacity and electric endurance performance, voltage level and capacity of a single energy storage converter (PCS) in energy storage field engineering are not high. In order to realize large-capacity reactive power regulation, a grid-side battery energy storage power station is usually formed by connecting a large number of PCS in parallel, and the PCS is connected with a battery cabin comprising a plurality of battery stacks. The energy storage power station comprises a plurality of sections of low-voltage buses, each section of bus is directly led from the low-voltage side of each main transformer of an adjacent substation, namely, the frequency and voltage protection function of each section of low-voltage bus has certain independence. And each PCS is uniformly distributed to each section of low-voltage bus in the energy storage power station, and frequency voltage protection equipment needs to be independently configured for each section of low-voltage bus. Now, a certain set of frequency voltage protection equipment configured on a certain section of low-voltage bus is taken as an example for explanation, and a wiring schematic is shown in fig. 1.
At present, the frequency voltage protection equipment only collects the three-phase alternating voltage of a low-voltage bus in a station at present, and the logic judgment is rough slightly. For example, the energy storage station sends power to the system, and at the same time, the system frequency is low, the frequency voltage protection still acts to cut off the energy storage station, and the system frequency is deteriorated, so that a Current Transformer (CT) needs to be introduced in fig. 1 to measure the grid-connected point three-phase alternating current of each branch.
For this purpose, the invention proposes to add an active reactive blocking logic in the frequency voltage protection logic, as shown in fig. 2, for the technical problem and the type of control object. Before the action due to low frequency, the energy storage station needs to judge that the output active power to the system is negative; before the action due to high frequency, the energy storage station needs to judge that the output active power to the system is positive; before the system operates due to low voltage, the energy storage station needs to judge that the output reactive power of the system is negative; before the system operates due to high voltage, the energy storage station needs to judge that the output reactive power of the system is positive. Therefore, the action correctness of the frequency-voltage protection equipment is improved, the fast response characteristic of the energy storage station can be fully supported to stably operate a power grid, and the situations that the energy storage station cuts off the energy storage station when the system frequency is low while discharging and further deteriorates the system frequency and cuts off the energy storage station when the system voltage is high while absorbing reactive power can be avoided. Of course, the power judgment needs to be calculated through voltage and current, so the improved protection method of the invention needs to introduce three-phase alternating current of the outlet grid-connected electricity of the energy storage station into the frequency voltage protection equipment in fig. 1.
Specifically, as shown in fig. 2, based on the technical problems carefully analyzed and found, the present invention proposes an improved method for protecting the frequency and voltage of the grid-side energy storage power station,
step 1: introducing a three-phase current of a grid connection point into control protection equipment;
the step 1 specifically comprises the following steps 1-1 to 1-5:
step 1-1: expanding the capacity of a sampling board card of the frequency-voltage protection equipment to enable the sampling board card to support at least one path of three-phase alternating voltage and one path of three-phase alternating current sampling capacity;
step 1-2: modifying the sampling display of the frequency-voltage protection equipment, and increasing the amplitude and phase display, active and reactive vector display of the three-phase current of the outgoing line grid-connected point on the basis of the original analog quantity display;
step 1-3: a connecting line between a low-voltage bus of the energy storage station and an electric power system is defined as an outgoing line, and a connecting line between the low-voltage bus of the energy storage station and an in-station energy storage converter is defined as an incoming line;
step 1-4: each outgoing three-phase alternating current is connected to the control protection equipment, and if the outgoing switch cabinet is provided with a standby independent protection level CT winding, a cable is laid to connect the CT winding to the control protection equipment; if the standby independent protection CT winding is not available, switching from other screen cabinets can be considered, but the secondary load of the current loop is ensured to meet the requirement on the premise;
step 1-5: the power grid side battery energy storage power station is composed of a plurality of energy storage converters, each energy storage converter is distributed to different low-voltage bus sections in the station, each bus section is provided with independent frequency and voltage protection equipment, and when three-phase alternating current of an outgoing line is accessed, power calculation and action measure errors caused by confusion of different three-phase currents of the outgoing line are avoided;
step 2: modifying the frequency voltage protection action logic of the control protection equipment, calculating the active power and the reactive power of a line according to the three-phase current of the grid-connected point, and judging that the active power output by the energy storage station to the system is negative before the action due to low frequency; before the action due to high frequency, the energy storage station needs to judge that the active power output to the system is positive; before the system operates due to low voltage, the energy storage station needs to judge that the reactive power output to the system is negative; before the system operates due to high voltage, the energy storage station needs to judge that the reactive power output to the system is positive.
The step 2 specifically comprises the following steps 2-1 to 2-10:
step 2-1: modifying a program in a CPU of the control protection equipment, and increasing the calculation of the active power and the calculation of the reactive power of the outgoing line;
step 2-2: the outgoing line power direction is specified, when the energy storage power station outputs active/reactive power to the power system, the active/reactive power of the outgoing line is judged to be positive, otherwise, the active/reactive power of the outgoing line is judged to be negative;
step 2-3: when the control protection equipment monitors that the system frequency is low, and simultaneously judges that the active power of the outlet wire is negative, the outlet wire jumping switch is operated in turns, and the frequency of the support system is recovered;
step 2-4: when the control protection equipment monitors that the frequency drop amplitude of the system is large, the change rate df/dt of the frequency along with the time exceeds a fixed value, and meanwhile, the active power of the outgoing line is judged to be negative, the control protection equipment immediately acts to jump off all incoming lines on the corresponding low-voltage bus;
step 2-5: when the control protection equipment monitors that the system frequency is higher, and simultaneously judges that the active power of the outgoing line is positive, the outgoing line jumping switch is operated in turns, and the frequency of the system is restored;
step 2-6: when the control protection equipment monitors that the rising amplitude of the system frequency is large, the change rate df/dt of the frequency along with the time exceeds a fixed value, and meanwhile, the active power of the outgoing line is judged to be positive, the control protection equipment immediately acts to jump off all incoming lines on the corresponding low-voltage bus;
step 2-7: when the control protection equipment monitors that the system voltage is low, and simultaneously judges that the reactive power of the outlet wire is negative, the outlet wire jumping switch is operated in turns to support the system voltage recovery;
step 2-8: when the control protection equipment monitors that the voltage drop amplitude of the system is large, the change rate du/dt of the voltage along with the time exceeds a fixed value, and meanwhile, the reactive power of the outgoing line is judged to be negative, the control protection equipment immediately acts to trip off all incoming lines on the corresponding low-voltage bus;
step 2-9: when the control protection equipment monitors that the system voltage is higher, and simultaneously judges that the reactive power of the outgoing line is positive, the outgoing line is tripped into the line switch by the action of the control protection equipment in turns, and the voltage of the system is supported to be recovered;
step 2-10: when the control protection equipment monitors that the rising amplitude of the system voltage is large, the change rate du/dt of the voltage along with the time exceeds a fixed value, and meanwhile, the reactive power of the outgoing line is judged to be positive, the control protection equipment immediately acts to jump off all incoming lines on the corresponding low-voltage bus.
It is worth mentioning that, in order to improve the response speed, the steps 2-3 to 2-10 may be executed in parallel. The protection method is particularly suitable for being used in a power grid side energy storage power station with dual attributes of power and load, the modified hardware cost (increased CT of corresponding branches) is low, and the workload of software program modification is small.
It should be noted that the technical problems in the background art discovered in the present invention are not easy, and after a detailed analysis of the defects in the prior art, the present invention provides a method for protecting the frequency and voltage of a power grid side energy storage power station, wherein an active and reactive blocking function output by the energy storage station is introduced in a frequency and voltage protection logic by introducing a three-phase alternating current into a frequency and voltage protection device, so that more frequency and voltage protection is triggered by a protection system and acts correctly in time, and the protection method with the introduced active and reactive blocking function is particularly suitable for a power grid side energy storage power station with dual attributes of power and load.
Finally, the description is as follows: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (5)
1. A frequency and voltage protection method for a power grid side energy storage power station is characterized by comprising the following steps:
step 1: introducing a three-phase current of a grid connection point into control protection equipment;
step 2: modifying the frequency voltage protection action logic of the control protection equipment, calculating the magnitude and direction of active power and reactive power of a line according to the three-phase current of the grid-connected point, and judging that the active power output by the energy storage station to the system is negative before the action due to low frequency; before the action due to high frequency, the energy storage station needs to judge that the active power output to the system is positive; before the system operates due to low voltage, the energy storage station needs to judge that the reactive power output to the system is negative; before the action due to high voltage, the energy storage station needs to judge that the reactive power output to the system is positive; the detailed steps of step 2 include:
step 2-1: modifying a program in the control protection equipment, and increasing the calculation of the active power and the calculation of the reactive power of the outgoing line;
step 2-2: the outgoing line power direction is specified, when the energy storage power station outputs active/reactive power to the power system, the active/reactive power of the outgoing line is judged to be positive, otherwise, the active/reactive power of the outgoing line is judged to be negative;
step 2-3: when the control protection equipment monitors that the system frequency is low, and simultaneously judges that the active power of the outlet wire is negative, the outlet wire jumping switch is operated in turns, and the frequency of the support system is recovered;
step 2-4: when the control protection equipment monitors that the frequency drop amplitude of the system is large, the change rate df/dt of the frequency along with the time exceeds a fixed value, and meanwhile, the active power of the outgoing line is judged to be negative, the control protection equipment immediately acts to jump off all incoming lines on the corresponding low-voltage bus;
step 2-5: when the control protection equipment monitors that the system frequency is higher, and simultaneously judges that the active power of the outgoing line is positive, the outgoing line jumping switch is operated in turns, and the frequency of the system is restored;
step 2-6: when the control protection equipment monitors that the rising amplitude of the system frequency is large, the change rate df/dt of the frequency along with the time exceeds a fixed value, and meanwhile, the active power of the outgoing line is judged to be positive, the control protection equipment immediately acts to jump off all incoming lines on the corresponding low-voltage bus;
step 2-7: when the control protection equipment monitors that the system voltage is low, and simultaneously judges that the reactive power of the outlet wire is negative, the outlet wire jumping switch is operated in turns to support the system voltage recovery;
step 2-8: when the control protection equipment monitors that the voltage drop amplitude of the system is large, the change rate du/dt of the voltage along with the time exceeds a fixed value, and meanwhile, the reactive power of the outgoing line is judged to be negative, the control protection equipment immediately acts to trip off all incoming lines on the corresponding low-voltage bus;
step 2-9: when the control protection equipment monitors that the system voltage is higher, and simultaneously judges that the reactive power of the outgoing line is positive, the outgoing line is tripped into the line switch by the action of the control protection equipment in turns, and the voltage of the system is supported to be recovered;
step 2-10: when the control protection equipment monitors that the rising amplitude of the system voltage is large, the change rate du/dt of the voltage along with the time exceeds a fixed value, and meanwhile, the reactive power of the outgoing line is judged to be positive, the control protection equipment immediately acts to jump off all incoming lines on the corresponding low-voltage bus.
2. The frequency-voltage protection method according to claim 1, wherein the detailed steps of step 1 include:
step 1-1: expanding the capacity of a sampling board card of the frequency-voltage protection equipment to enable the sampling board card to support at least one grid-connected point three-phase voltage and one grid-connected point three-phase current sampling capacity;
step 1-2: modifying the sampling display of the frequency-voltage protection equipment, and increasing the amplitude and phase display, active and reactive vector display of the three-phase current of the outgoing line grid-connected point on the basis of the original analog quantity display;
step 1-3: a connecting line between a low-voltage bus of the energy storage station and an electric power system is defined as an outgoing line, and a connecting line between the low-voltage bus of the energy storage station and an in-station energy storage converter is defined as an incoming line;
step 1-4: connecting the grid-connected point three-phase current of each outgoing line into a control protection device, and if the outgoing line switch cabinet is provided with a standby independent protection level CT winding, connecting the CT winding into the control protection device by laying a cable; if the standby independent protection CT winding does not exist, switching from other screen cabinets is considered, but the secondary load of the current loop is ensured to meet the requirement on the premise;
step 1-5: the grid side battery energy storage power station is composed of a plurality of energy storage converters, each energy storage converter is distributed to different low-voltage bus sections in the station, each bus section is provided with independent frequency and voltage protection equipment, and when three-phase currents of grid-connected points are accessed, power calculation and action measure errors caused by confusion of the three-phase currents of different outgoing lines are avoided.
3. The frequency-voltage protection method according to claim 1, wherein the steps 2-3 to 2-10 are performed in parallel with each other.
4. The utility model provides a power grid side energy storage power station frequency voltage protection system which characterized in that includes:
at least one processor; and
at least one memory communicatively coupled to the processor, wherein:
the memory stores program instructions executable by the processor, the processor invoking the program instructions to enable performance of the frequency voltage protection method of any one of claims 1 to 3.
5. A non-transitory computer-readable storage medium storing computer instructions for causing a computer to perform the frequency-voltage protection method according to any one of claims 1 to 3.
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