CN113054633B - Time-limited current quick-break protection fixed value optimization method for power distribution network access of energy storage power station - Google Patents

Time-limited current quick-break protection fixed value optimization method for power distribution network access of energy storage power station Download PDF

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CN113054633B
CN113054633B CN201911383387.2A CN201911383387A CN113054633B CN 113054633 B CN113054633 B CN 113054633B CN 201911383387 A CN201911383387 A CN 201911383387A CN 113054633 B CN113054633 B CN 113054633B
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王宝华
邓雨捷
蒋海峰
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Nanjing University of Science and Technology
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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
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    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
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    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
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Abstract

The invention discloses a time-limited current quick-break protection fixed value optimization method for an energy storage power station to be connected into a power distribution network. The method comprises the following steps: firstly, defining critical current, farthest short-circuit current and standard current, and calculating the critical current according to parameters of a power distribution network and the maximum limit value of output current of an energy storage power station; then comparing the magnitude relation between the critical current and the farthest short-circuit current, and judging whether the short-circuit current output by the energy storage power station reaches the maximum current limit or not; and finally, determining an optimization factor alpha according to whether the output short-circuit current of the energy storage power station reaches the limit or not, and optimizing the time-limited current quick-break protection fixed value of the upstream line of the access point of the energy storage power station. The invention can act in three working states of charging, standby and discharging of the energy storage power station without limiting the access capacity and the access position of the energy storage power station, and has strong applicability and high reliability.

Description

Time-limited current quick-break protection fixed value optimization method for power distribution network access of energy storage power station
Technical Field
The invention belongs to the field of distribution automation, and particularly relates to a time-limited current quick-break protection fixed value optimization method for an energy storage power station to be connected into a power distribution network.
Background
With the continuous development of power systems, energy problems are also continuously highlighted, renewable energy sources are gradually popularized and applied in a distributed power supply mode, the industrial structure of power energy sources is improved, and meanwhile the centralized power supply pattern of a traditional power system is changed. However, no matter the power is generated by a large-capacity and high-parameter unit, the power is supplied by a traditional power generation mode of a large power grid through ultrahigh-voltage and long-distance power transmission, or is supplied by a new renewable energy source mode which has small capacity and is distributed dispersedly, and the power supply mode is not matched with an energy storage system.
Typical application scenarios of the energy storage system include a centralized new energy + energy storage system, a power supply side frequency modulation energy storage system, a power grid side energy storage system, a distributed and micro-grid energy storage system, and a user side application system. In recent years, energy storage power stations are applied more and more widely in power distribution systems due to the effects of peak clipping, valley filling, power supply stability improvement and the like, and a new problem is brought to the safe operation of a power distribution network while the power supply structure of the power distribution network is enriched.
The relay protection of the power distribution network is designed on the basis of the characteristics of a radioactive structure and single power supply of the power distribution network, three-section current protection is mainly used, the power distribution network is changed from single power supply to multi-power supply by the access of an energy storage power station, the energy storage power station is different from a conventional power supply, the fault characteristics of the energy storage power station are greatly influenced by a control strategy of the energy storage power station, and particularly for the time-limited current quick-break protection fixed value setting of an upstream line of an access point of the energy storage power station, if a conventional fixed value setting mode is adopted, the sensitivity of the protection is reduced, the phenomenon of refusal occurs, and the power supply safety of the power distribution network is threatened.
Disclosure of Invention
The invention aims to provide a time-limited current flow rate outage protection fixed value optimization method for accessing an energy storage power station into a power distribution network, which is high in applicability and reliability.
The technical solution for realizing the purpose of the invention is as follows: a time-limited current quick-break protection fixed value optimization method for an energy storage power station to be connected to a power distribution network comprises the following steps:
step 1, constructing an equivalent model of an energy storage power station, defining critical current, farthest short-circuit current and standard current, and calculating the critical current according to parameters of a power distribution network and a maximum limit value of output current of the energy storage power station;
step 2, comparing the magnitude relation between the critical current and the farthest short-circuit current, and judging whether the short-circuit current output by the energy storage power station reaches the maximum current limit or not;
and 3, determining an optimization factor alpha according to whether the output short-circuit current of the energy storage power station reaches the limit or not, and optimizing the time-limited current quick-break protection fixed value of the upstream line of the access point of the energy storage power station.
Further, the construction of the equivalent model of the energy storage power station in the step 1 specifically includes the following steps:
according to the control strategy and the working characteristics of the energy storage power station adopting constant power control, the establishment of an energy storage power station equivalent model is as follows:
Figure BDA0002342845540000021
in the formula, S N Rated power for energy storage power stations, E G For power station outlet of energy storageOral phase voltage, I G For outputting phase currents of energy-storing power stations, I N And the rated phase current of the energy storage power station is obtained.
Further, the critical current, the farthest short-circuit current and the standard current are defined in step 1, which are as follows:
the critical current is defined as: setting I N The rated current of the energy storage power station is the rated current of the energy storage power station, and when the output current of the energy storage power station just reaches the maximum current limit, namely 2 times of the rated current 2I N The current flowing through the upstream line protection of the access point of the energy storage power station has the calculation formula as follows:
Figure BDA0002342845540000022
in the formula I 1 ' is critical current, E is rated phase voltage of energy storage power station, Z S Is the system supply impedance, Z 1 The impedance of an upstream line of an access point of the energy storage power station;
the farthest short circuit current is defined as: when the short-circuit fault occurs at the end of the protection range of the time-limited current quick-break protection of the upstream line of the access point of the energy storage power station, the current flows through the protection of the upstream line of the access point of the energy storage power station;
the current to standard is defined as: when time-limited current quick-break protection sensitivity just meets the requirements, the fixed value of the time-limited current quick-break protection of the upstream line of the access point of the energy storage power station is calculated by the following formula:
Figure BDA0002342845540000023
in the formula I D To meet the current standard, I 1m For the current, K, flowing through the protection of the upstream line of the access point of the energy storage power station during the two-phase short circuit at the end of the upstream line of the access point of the energy storage power station sen To meet the required sensitivity.
Further, the magnitude relationship between the critical current and the farthest short-circuit current in step 2 is compared to determine whether the short-circuit current output by the energy storage station reaches the maximum current limit, specifically as follows:
step 2.1, defining a point k as a short-circuit point corresponding to critical current, and calculating the impedance between the point k and the head end of the downstream line of the access point of the energy storage power station according to the formula:
Figure BDA0002342845540000031
in the formula, Z 2 The impedance of a downstream line of an access point of the energy storage power station is beta' which is a constant;
calculating beta 'according to the formula, wherein if the beta' is more than or equal to 1, the output current of the energy storage power station must reach the limit; if beta' is less than 1, entering the step 2.2;
step 2.2, setting the farthest short-circuit current to be smaller than the critical current, and then calculating the farthest short-circuit current according to the following formula:
Figure BDA0002342845540000032
in the above formula, I 1 β is a constant for the farthest short circuit current;
substituting beta' as beta into the formula to calculate the farthest short circuit current I ″) 1 Then the farthest short-circuit current I ″, is measured 1 And critical current I 1 'comparison, if I' is still satisfied 1 ＜I 1 If not, the output current of the energy storage power station is not limited; if I ″) 1 ≥I 1 And if yes, the output current of the energy storage power station reaches the limit.
Further, in step 3, an optimization factor α is determined according to whether the output short-circuit current of the energy storage power station reaches a limit, and a time-limited current quick-break protection fixed value of an upstream line of an access point of the energy storage power station is optimized, specifically as follows:
step 3.1, defining the h point as a short-circuit point corresponding to the standard current, and then calculating the impedance between the h point and the head end of the downstream line of the access point of the energy storage power station according to the following formula:
Figure BDA0002342845540000033
in the formula, S N For rated capacity, beta, of energy-storage power stations D Is a constant;
step 3.2, determining an optimization factor alpha according to whether the output current of the energy storage power station reaches the limit, and calculating a current quick-break protection fixed value of a downstream line of an access point of the energy storage power station:
Figure BDA0002342845540000041
in the formula (I), the compound is shown in the specification,
Figure BDA0002342845540000042
the current quick-break protection constant value of the downstream line of the access point of the energy storage power station is obtained,
Figure BDA0002342845540000043
the current quick-break protection reliability coefficient is obtained;
Figure BDA0002342845540000044
the current is a time-limited current quick-break protection reliability coefficient;
step 3.3, optimizing a time-limited current quick-break protection fixed value of an upstream line of an access point of the energy storage power station, wherein the formula is as follows:
Figure BDA0002342845540000045
in the formula (I), the compound is shown in the specification,
Figure BDA0002342845540000046
and (4) setting a protection value for the time-limited current quick-break of the upstream line of the access point of the energy storage power station.
Compared with the prior art, the invention has the remarkable advantages that: (1) the protection scheme is optimized from the viewpoint of modifying the protection constant value, the access capacity and the access position of the energy storage power station are not limited by the protection requirement, and the applicability is strong; and (2) the control strategy and the working characteristics of the energy storage power station are comprehensively considered, and an equivalent model of the energy storage power station is constructed, so that the improved protection can reliably act in three working states of charging, standby and discharging of the energy storage power station, and the reliability is high.
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Fig. 1 is a flow schematic diagram of a time-limited current quick-break protection fixed value optimization method for accessing an energy storage power station to a power distribution network.
Fig. 2 is a block diagram of the overall structure of a PQ-controlled energy storage plant according to the present invention.
Fig. 3 is a topological structure diagram of a power distribution network typically including an energy storage power station in accordance with the present invention.
FIG. 4 is an equivalent circuit diagram of the energy storage power station access point downstream line short circuit.
Fig. 5 is an overall flow chart of the time-limited current quick-break protection fixed value optimization of the upstream line of the energy storage power station.
Detailed Description
The invention discloses a time-limited current quick-break protection fixed value optimization method for an energy storage power station to be connected to a power distribution network, which comprises the following steps of:
step 1, constructing an equivalent model of an energy storage power station, defining critical current, farthest short-circuit current and standard current, and calculating the critical current according to parameters of a power distribution network and a maximum limit value of output current of the energy storage power station;
step 2, comparing the magnitude relation between the critical current and the farthest short-circuit current, and judging whether the short-circuit current output by the energy storage power station reaches the maximum current limit or not;
and 3, determining an optimization factor alpha according to whether the output short-circuit current of the energy storage power station reaches the limit or not, and optimizing the time-limited current quick-break protection fixed value of the upstream line of the access point of the energy storage power station.
Further, the construction of the equivalent model of the energy storage power station in the step 1 specifically includes the following steps:
according to the control strategy and the working characteristics of the energy storage power station adopting constant power control, the establishment of an energy storage power station equivalent model is as follows:
Figure BDA0002342845540000051
in the formula, S N Rated power for energy storage power stations, E G For energy-storage power stationsOutlet phase voltage, I G For the output phase current of the energy-storing power station, I N And the rated phase current of the energy storage power station is obtained.
Further, the critical current, the farthest short-circuit current and the standard current are defined in step 1, which are as follows:
the critical current is defined as: setting I N The rated current of the energy storage power station is the rated current of the energy storage power station, and when the output current of the energy storage power station just reaches the maximum current limit, namely 2 times of the rated current 2I N The current flowing through the upstream line protection of the access point of the energy storage power station has the calculation formula as follows:
Figure BDA0002342845540000052
in the formula I 1 ' is critical current, E is rated phase voltage of energy storage power station, Z S Is the system supply impedance, Z 1 The impedance of an upstream line of an access point of the energy storage power station;
the definition of the farthest short-circuit current is: when the end of the protection range of the time-limited current quick-break protection of the upstream line of the access point of the energy storage power station has a short-circuit fault, the current flows through the protection of the upstream line of the access point of the energy storage power station;
the current to standard is defined as: when time-limited current quick-break protection sensitivity just meets the requirements, the fixed value of the time-limited current quick-break protection of the upstream line of the access point of the energy storage power station is calculated by the following formula:
Figure BDA0002342845540000053
in the formula I D To meet the current standard, I 1m For the current, K, flowing through the protection of the upstream line of the access point of the energy storage power station during the two-phase short circuit at the end of the upstream line of the access point of the energy storage power station sen The value is 1.3 to meet the required sensitivity.
Further, the magnitude relation between the critical current and the farthest short-circuit current in step 2 is compared, and whether the output short-circuit current of the energy storage power station reaches the maximum current limit is judged, specifically as follows:
step 2.1, defining a point k as a short-circuit point corresponding to critical current, and calculating the impedance between the point k and the head end of the downstream line of the access point of the energy storage power station according to the following formula:
Figure BDA0002342845540000061
in the formula, Z 2 The impedance of a downstream line of an access point of the energy storage power station is beta' which is a constant;
calculating beta 'according to the formula, wherein if the beta' is more than or equal to 1, the output current of the energy storage power station must reach the limit; if beta' is less than 1, entering the step 2.2;
step 2.2, setting the farthest short-circuit current to be smaller than the critical current, and then calculating the farthest short-circuit current according to the following formula:
Figure BDA0002342845540000062
in the formula, I 1 β is a constant for the farthest short circuit current;
substituting beta' as beta into the formula to calculate the farthest short circuit current I ″) 1 Then the farthest short-circuit current I ″, is measured 1 And critical current I 1 'comparison, if I' is still satisfied 1 ＜I 1 ', the output current of the energy storage power station does not reach the limit; if I ″) 1 ≥I 1 And if yes, the output current of the energy storage power station reaches the limit.
Further, in step 3, an optimization factor α is determined according to whether the output short-circuit current of the energy storage power station reaches a limit, and a time-limited current quick-break protection fixed value of an upstream line of an access point of the energy storage power station is optimized, specifically as follows:
step 3.1, defining the h point as a short-circuit point corresponding to the standard current, and then calculating the impedance between the h point and the head end of the downstream line of the access point of the energy storage power station according to the following formula:
Figure BDA0002342845540000063
in the formula，S N For rated capacity, beta, of energy-storage power stations D Is a constant;
step 3.2, determining an optimization factor alpha according to whether the output current of the energy storage power station reaches the limit, and calculating a current quick-break protection fixed value of a downstream line of an access point of the energy storage power station:
Figure BDA0002342845540000071
in the formula (I), the compound is shown in the specification,
Figure BDA0002342845540000072
the current quick-break protection constant value is set for the current of the downstream line of the access point of the energy storage power station,
Figure BDA0002342845540000073
the value of the current quick-break protection reliability coefficient is 1.2;
Figure BDA0002342845540000074
the value of the time-limited current quick-break protection reliability coefficient is 1.25;
step 3.3, optimizing a time-limited current quick-break protection fixed value of an upstream line of an access point of the energy storage power station, wherein the formula is as follows:
Figure BDA0002342845540000075
in the formula (I), the compound is shown in the specification,
Figure BDA0002342845540000076
and the fixed value is protected for the time-limited current quick-break of the upstream line of the access point of the energy storage power station.
The invention is described in further detail below with reference to the figures and the specific embodiments.
Examples
With reference to fig. 1, the invention relates to a time-limited current quick-break protection fixed value optimization method for an energy storage power station to be connected to a power distribution network, which comprises the following steps:
step 1, constructing an equivalent model of an energy storage power station, defining critical current, farthest short-circuit current and standard current, and calculating the critical current according to parameters of a power distribution network and a maximum limit value of output current of the energy storage power station, wherein the method specifically comprises the following steps:
the fault characteristics of the energy storage power station depend on the control strategy of the inverter, and the generally adopted control strategy is constant power control (PQ control), and the overall structure diagram of the PQ controlled energy storage power station is shown in fig. 2. The energy storage power station under the PQ control can be regarded as a constant power output power supply, the active power and the reactive power of the power station can track reference signals in real time, the active power and the reactive power are controlled in a decoupling mode, the current is controlled in a PI mode, and the output is kept constant. Voltage and current in an abc coordinate system in a power grid are converted through abc/dq to obtain d-axis and Q-axis components, and the voltage and current components in the dq coordinate system are used for calculating to obtain measured values of active power P and reactive power Q. The active power and the reactive power reference value P are compared ref 、Q ref Comparing with the actual measured values of the active power and the reactive power to obtain active and reactive deviation, and generating a current reference value I under a current dq coordinate system through a PI (proportional-integral) controller L.ref Comparing with the actual measured value to generate a voltage reference value u obtained by a PI link under a dq coordinate system ref The pulse width modulation control circuit is used for controlling an SPWM (sine pulse width modulator) to generate trigger pulses to obtain a driving signal of the inverter, so that the aim of controlling the inverter to output constant power is fulfilled. The output current of the energy storage power station is limited to be less than 2 times of the rated current by the output current of the inverter, when the output current does not reach the maximum output current, the energy storage power station maintains the output power S unchanged, and when the outlet voltage is reduced, the output current is increased. When the output current of the energy storage power station reaches the maximum current limit, the output power also decreases along with the reduction of the voltage at the outlet. The working states of energy storage power stations are generally divided into three types: charging, discharging and standby. The working characteristic of the energy storage power station is equivalent to a load in the charging state, and according to the characteristics, the energy storage power station equivalent model in the discharging state is established as follows:
Figure BDA0002342845540000081
in the formula, S N Rated power for energy storage power stations, E G For the outlet phase voltage of the energy storage station, I G For the output phase current of the energy-storing power station, I N And the rated phase current of the energy storage power station is obtained.
Further, a topological diagram of a power distribution network of a typical power station with energy storage is constructed, as shown in fig. 3, due to the radiation-shaped structure of the power distribution network, any power distribution network can be equivalent to a typical power distribution network topology through the impedance series-parallel connection principle (equivalent line to equivalent impedance). For time-limited current quick-break protection of an upstream line of an access point of an energy storage power station, the setting principle is a current quick-break protection constant value which avoids a lower-level line, namely
Figure BDA0002342845540000082
In the formula (I), the compound is shown in the specification,
Figure BDA0002342845540000083
the method is characterized in that a fixed value is protected for time-limited current quick-break of an upstream line of an access point of an energy storage power station,
Figure BDA0002342845540000084
the current quick-break protection constant value is set for the current of the downstream line of the access point of the energy storage power station,
Figure BDA0002342845540000085
the reliability coefficient of the current protection II section is 1.25.
Because the power distribution network becomes a multi-source network after the energy storage power station is accessed, the current value measured by the upstream line protection part of the access point of the energy storage power station is smaller than the current value measured by the downstream line protection part of the access point of the energy storage power station, if the setting mode is still used, the sensitivity of the time-limited current quick-break protection of the upstream line of the access point of the energy storage power station is reduced, and the failure condition occurs.
Further, according to the exemplary topology shown in fig. 3, an equivalent circuit diagram of the fault occurring on the downstream line of the access point of the energy storage power station can be obtained, as shown in fig. 4, where β is a percentage value of the impedance between the short circuit point and the head end of the downstream line of the access point of the energy storage power station to the total impedance of the downstream line of the access point of the energy storage power station, and the following equations are derived from the equivalent circuit shown in fig. 4.
Further, a critical current, a farthest short circuit current and a standard current are defined as follows:
the critical current is defined as: setting I N The rated current of the energy storage power station is the rated current of the energy storage power station, and when the output current of the energy storage power station just reaches the maximum current limit, namely 2 times of the rated current 2I N The current flowing through the upstream line protection of the access point of the energy storage power station has the calculation formula as follows:
Figure BDA0002342845540000091
in the formula I 1 ' is critical current, E is rated phase voltage of energy storage power station, and Z S Is the system supply impedance, Z 1 The impedance of an upstream line of an access point of the energy storage power station; defining k point as critical current corresponding short circuit point, obviously, when the short circuit point is positioned at the downstream of the critical short circuit point k, the short circuit current provided by the energy storage power station is less than 2I N (ii) a When the short-circuit point is positioned at the upper stream of the critical short-circuit point k, the improved short-circuit current of the energy storage power station is equal to 2I N 。
The definition of the farthest short-circuit current is: when the short-circuit fault occurs at the end of the protection range of the time-limited current quick-break protection of the upstream line of the access point of the energy storage power station, the current flows through the protection of the upstream line of the access point of the energy storage power station; defining j point as the short-circuit point corresponding to the farthest short-circuit current, when the farthest short-circuit current is less than the critical current, the j point at the end of the protection range is at the downstream of the critical short-circuit point k, and the short-circuit current provided by the energy storage power station is less than 2I N (ii) a When the farthest short-circuit current is larger than the critical current, the j point at the tail end of the protection range is at the upstream of the critical short-circuit point k, and the short-circuit current increased by the energy storage power station is equal to 2I N Therefore, the optimization is divided into two cases.
The current to standard is defined as: when time-limited current quick-break protection sensitivity just meets the requirements, the fixed value of the time-limited current quick-break protection of the upstream line of the access point of the energy storage power station is calculated by the following formula:
Figure BDA0002342845540000092
in the formula I D To meet the current standard, I 1m For the current, K, flowing through the protection of the upstream line of the access point of the energy storage power station during the two-phase short circuit at the end of the upstream line of the access point of the energy storage power station sen The value is 1.3 to meet the required sensitivity.
Step 2, comparing the magnitude relation between the critical current and the farthest short-circuit current, and judging whether the short-circuit current output by the energy storage power station reaches the maximum current limit, wherein the method specifically comprises the following steps:
step 2.1, defining a point k as a short-circuit point corresponding to critical current, and calculating the impedance between the point k and the head end of the downstream line of the access point of the energy storage power station according to the formula:
Figure BDA0002342845540000093
in the formula, Z 2 The impedance of a downstream line of an access point of the energy storage power station is beta', and is a constant;
calculating beta 'according to the formula, wherein if the beta' is more than or equal to 1, the output current of the energy storage power station must reach the limit; if the beta' is less than 1, entering the step 2.2;
step 2.2, setting the farthest short-circuit current to be smaller than the critical current, and then calculating the farthest short-circuit current according to the following formula:
Figure BDA0002342845540000101
in the formula, I 1 β is a constant for the farthest short circuit current;
substituting beta' as beta into the formula to calculate the farthest short circuit current I ″) 1 Then the farthest short-circuit current I ″, is measured 1 And critical current I 1 'comparison, if I' is still satisfied 1 ＜I 1 If not, the output current of the energy storage power station is not limited; if I ″) 1 ≥I 1 ', then output current of energy storage power stationThe limit is reached.
Step 3, determining an optimization factor alpha according to whether the output short-circuit current of the energy storage power station reaches a limit, and optimizing a time-limited current quick-break protection fixed value of an upstream line of an access point of the energy storage power station, wherein the time-limited current quick-break protection fixed value is as follows by combining with a graph 5:
step 3.1, defining the h point as a short-circuit point corresponding to the standard current, and then calculating the impedance between the h point and the head end of the downstream line of the access point of the energy storage power station according to the following formula:
Figure BDA0002342845540000102
in the formula, S N For rated capacity, beta, of energy-storage power stations D Is a constant, can be solved to beta according to the above formula D ；
Step 3.2, determining an optimization factor alpha according to whether the output current of the energy storage power station reaches the limit, and calculating a current quick-break protection fixed value of a downstream line of an access point of the energy storage power station:
when the output current of the energy storage power station is not limited, according to the formula:
Figure BDA0002342845540000103
get beta D The upper limit of an optimization factor alpha obtained by solving the farthest short-circuit current is smaller, so that the protection sensitivity is favorably increased, the farthest short-circuit current corresponds to the tail end of a protection range of the limited-time current flow outage protection of an upstream line of an access point of the energy storage power station, the value of the farthest short-circuit current is equal to an actual setting value, and in order to ensure the sensitivity requirement, the optimized fixed value needs to be smaller than beta at the moment D The setting formula after introducing the optimization factor alpha of the corresponding farthest short circuit current value is as follows:
Figure BDA0002342845540000111
this time is:
Figure BDA0002342845540000112
when the energy storage power station is in a charging or standby state, a downstream line of an access point of the energy storage power station fails, short-circuit current provided by the energy storage power station is 0, the time-limited current quick-break protection fixed value of the upstream line of the access point of the energy storage power station is modified according to the process, and under the condition, the protection range of the quick-break protection device may exceed the current quick-break protection of the downstream line of the access point of the energy storage power station, so that misoperation is caused. The current quick-break protection setting value of the downstream line of the access point of the energy storage power station when the energy storage power station is in a charging or standby state is as follows:
Figure BDA0002342845540000113
therefore, the protection setting value of the current II section at the protection 1 is not less than the protection setting value of the current I section at the protection 2 when the energy storage power station is in a charging or standby state, namely
Figure BDA0002342845540000114
Then there are:
Figure BDA0002342845540000115
in order to ensure sensitivity and selectivity at the same time, the optimization factor takes the intermediate value of the upper and lower limits, namely:
Figure BDA0002342845540000116
combining a current quick-break protection fixed value setting formula of a downstream line of an access point of the energy storage power station when the output current of the energy storage power station is not up to the limit:
Figure BDA0002342845540000117
in the above formula
Figure BDA0002342845540000118
The value of the current quick-break protection reliability coefficient is 1.2;
step 3.3, optimizing a time-limited current quick-break protection fixed value of an upstream line of an access point of the energy storage power station, wherein the formula is as follows:
Figure BDA0002342845540000121
when the output current of the energy storage power station reaches the limit, according to the formula:
Figure BDA0002342845540000122
get beta D The corresponding farthest short-circuit current is similar to the situation that the output current of the energy storage power station does not reach the limit, and the upper limit of an optimization factor alpha can be obtained:
Figure BDA0002342845540000123
in order to ensure the selectivity of protection, the misoperation prevention when the energy storage power station is in a standby or charging state needs to be considered, and the setting principle here is similar to the situation that the output current of the energy storage power station does not reach the limit, and the following steps are included:
Figure BDA0002342845540000124
in order to ensure sensitivity and selectivity at the same time, the optimization factor takes the intermediate value of the upper and lower limits, namely:
Figure BDA0002342845540000125
combining a current quick-break protection fixed value setting formula of a downstream line of an access point of the energy storage power station when the output current of the energy storage power station is not up to the limit:
Figure BDA0002342845540000126
can be obtained by the following formula:
Figure BDA0002342845540000127
and obtaining an optimized setting value when the output current of the energy storage power station reaches the limit.
The time-limited current quick-break protection of the upstream line of the access point of the energy storage power station after the fixed value optimization can ensure that no false action or refusal action occurs under each working state of the energy storage power station, and the action can be reliably performed.
Taking two actual power distribution network parameters as an example, the protection fixed value of the power distribution network parameters is optimized by adopting the process, and the power distribution network parameters are shown in the following table 1:
TABLE 1
Figure BDA0002342845540000131
The optimization results are shown in table 2 below:
TABLE 2
Figure BDA0002342845540000132
The optimization result shows that for 2 power distribution networks, after the energy storage power stations are accessed, the sensitivity of the time-limited current quick-break protection of the upstream line of the access point of the energy storage power station obtained according to the original setting mode can not meet the requirements.

Claims (2)

1. A time-limited current quick-break protection fixed value optimization method for an energy storage power station to be connected to a power distribution network is characterized by comprising the following steps:
step 1, constructing an equivalent model of an energy storage power station, defining critical current, farthest short-circuit current and standard current, and calculating the critical current according to parameters of a power distribution network and the maximum limit value of output current of the energy storage power station;
step 2, comparing the magnitude relation between the critical current and the farthest short-circuit current, and judging whether the output short-circuit current of the energy storage power station reaches the maximum current limit or not;
step 3, determining an optimization factor alpha according to whether the output short-circuit current of the energy storage power station reaches a limit, and optimizing a time-limited current quick-break protection fixed value of an upstream line of an access point of the energy storage power station;
the construction of the equivalent model of the energy storage power station in the step 1 specifically comprises the following steps:
according to the control strategy and the working characteristics of the energy storage power station adopting constant power control, the establishment of an energy storage power station equivalent model is as follows:
Figure FDA0003690889050000011
in the formula, S N Rated power for energy storage power stations, E G For the outlet phase voltage of the energy storage station, I G For the output phase current of the energy-storing power station, I N Rated current for the energy storage power station;
defining critical current, farthest short circuit current and standard current in the step 1, specifically as follows:
the critical current is defined as: setting I N The rated current of the energy storage power station is the rated current of the energy storage power station, and when the output current of the energy storage power station just reaches the maximum current limit, namely 2 times of the rated current 2I N The current flowing through the upstream line protection of the access point of the energy storage power station is calculated by the following formula:
Figure FDA0003690889050000012
in formula (II)' 1 Is critical current, E is rated phase voltage of energy storage power station, Z S Is the system supply impedance, Z 1 The impedance of an upstream line of an access point of the energy storage power station;
the definition of the farthest short-circuit current is: when the short-circuit fault occurs at the end of the protection range of the time-limited current quick-break protection of the upstream line of the access point of the energy storage power station, the current flows through the protection of the upstream line of the access point of the energy storage power station;
the current to standard is defined as: when the sensitivity of the time-limited current quick-break protection just meets the requirement, the fixed value of the time-limited current quick-break protection of the upstream line of the access point of the energy storage power station is calculated by the following formula:
Figure FDA0003690889050000013
in the formula I D To meet the current standard, I 1m For the current, K, flowing through the protection of the upstream line of the access point of the energy storage station in the event of a two-phase short circuit at the end of the upstream line of the access point of the energy storage station sen To meet the required sensitivity;
comparing the magnitude relation between the critical current and the farthest short-circuit current, and judging whether the short-circuit current output by the energy storage power station reaches the maximum current limit, wherein the method specifically comprises the following steps:
step 2.1, defining k point as a critical current corresponding short circuit point, and impedance beta' Z between the k point and the head end of the downstream line of the access point of the energy storage power station 2 The calculation formula is as follows:
Figure FDA0003690889050000014
in the formula, Z 2 The impedance of a downstream line of an access point of the energy storage power station is beta' which is a constant;
calculating beta 'according to the formula, wherein if the beta' is more than or equal to 1, the output current of the energy storage power station must reach the limit; if beta' is less than 1, entering a step 2.2;
step 2.2, setting the farthest short-circuit current to be smaller than the critical current, and then calculating the farthest short-circuit current according to the following formula:
Figure FDA0003690889050000021
in the formula, I 1 β is a constant for the farthest short circuit current;
substituting beta' as beta into the formula to calculate the farthest short circuit current I ″) 1 Then the farthest short-circuit current I ″, is measured 1 And critical current I' 1 Comparing, if I ″' is still satisfied 1 ＜I′ 1 If the output current of the energy storage power station does not reach the limit; if I ″) 1 ≥I′ 1 And the output current of the energy storage power station reaches the limit.
2. The method for optimizing the time-limited current quick-break protection fixed value of the energy storage power station to be connected to the power distribution network according to claim 1, wherein an optimization factor alpha is determined according to whether the short-circuit current output by the energy storage power station reaches a limit or not, and the time-limited current quick-break protection fixed value of an upstream line of an access point of the energy storage power station is optimized, specifically as follows:
step 3.1, defining the h point as a short-circuit point corresponding to the standard current, and then impedance beta between the h point and the head end of the downstream line of the access point of the energy storage power station D Z 2 The calculation formula is as follows:
Figure FDA0003690889050000022
in the formula, S N For rated capacity, beta, of energy-storage power stations D Is a constant;
step 3.2, determining an optimization factor alpha according to whether the output current of the energy storage power station reaches the limit, and calculating a current quick-break protection fixed value of a downstream line of an access point of the energy storage power station:
Figure FDA0003690889050000023
in the formula (I), the compound is shown in the specification,
Figure FDA0003690889050000031
the current quick-break protection constant value is set for the current of the downstream line of the access point of the energy storage power station,
Figure FDA0003690889050000032
the current quick-break protection reliability coefficient is obtained;
Figure FDA0003690889050000033
the current is a time-limited current quick-break protection reliable coefficient;
step 3.3, optimizing a time-limited current quick-break protection fixed value of an upstream line of an access point of the energy storage power station, wherein the formula is as follows:
Figure FDA0003690889050000034
in the formula (I), the compound is shown in the specification,
Figure FDA0003690889050000035
and the fixed value is protected for the time-limited current quick-break of the upstream line of the access point of the energy storage power station.
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Publication number Priority date Publication date Assignee Title
CN106684834A (en) * 2015-11-10 2017-05-17 中国电力科学研究院 Adaptive current protection system and method for power distribution network
CN107706893A (en) * 2017-10-31 2018-02-16 广东电网有限责任公司惠州供电局 A kind of computational methods of DG accesses distribution optimum capacity
WO2018129842A1 (en) * 2017-01-10 2018-07-19 华北电力大学 Pilot protection method for transmission line of new energy station based on current waveform similarity
WO2018167306A1 (en) * 2017-03-16 2018-09-20 Naval Group System for supplying electrical energy to an on-board network of a submarine

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN106684834A (en) * 2015-11-10 2017-05-17 中国电力科学研究院 Adaptive current protection system and method for power distribution network
WO2018129842A1 (en) * 2017-01-10 2018-07-19 华北电力大学 Pilot protection method for transmission line of new energy station based on current waveform similarity
WO2018167306A1 (en) * 2017-03-16 2018-09-20 Naval Group System for supplying electrical energy to an on-board network of a submarine
CN107706893A (en) * 2017-10-31 2018-02-16 广东电网有限责任公司惠州供电局 A kind of computational methods of DG accesses distribution optimum capacity

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