Control method and system for substation 10kV side spare power automatic throw-in

Abstract

The application discloses a control method and system of a substation 10-kilovolt side spare power automatic throw-in under a distributed photovoltaic wide access, and belongs to the technical field of substation automatic control. According to five interval conditions of 10-kilovolt bus voltage U<50%UN, 50%UN<=U<85%UN, 85%UN<=U<110%UN, 110%UN<=U<135%UN and 135%UN<=U, and considering the frequency condition 47.5Hz<=f<=50.2Hz under the condition of having voltage, the corresponding power spare automatic throw-in is carried out. The application perfects the current running spare power automatic throw-in criterion and action logic, adapts to the development of a new type of "active" bidirectional interactive power distribution network, and meets the characteristics of pure power load access of a 10-kilovolt line customer, multi-level and wide-range access of distributed photovoltaic, and random and unstable output. The application maximally reduces the influence on power consumption and power generation of customers (power consumption customers and power generation customers).

Description

Technical Field

[0001] The present invention relates to a control method and system for a 10 kV side standby automatic switching of a substation, and more particularly to a control method and system for a 10 kV side standby automatic switching of a substation under widespread access of distributed photovoltaics, belonging to the technical field of substation automatic control. Background Art

[0002] With the development of new power systems, distributed photovoltaics are widely connected in large quantities, including (1) 220V and 380V are widely connected to distribution stations and customer distribution rooms; (2) 10kV T-connected to 10kV distribution lines and 10kV busbars in customer distribution rooms; (3) 10kV dedicated lines connected to 10kV intervals in substations (in order to improve the utilization efficiency of distribution network resources, this situation will become less and less common). In addition to connecting to the loads of existing power users, the 10kV outgoing lines of substations are also facing the situation of 220V and 380V photovoltaics connected to distribution stations and customer distribution rooms, and 10kV photovoltaic T-connected to 10kV lines and 10kV busbars in customer distribution rooms. This period is also mixed with distributed wind power, energy storage, etc., which are randomly distributed.

[0003] In order to improve the power supply reliability of the 10kV distribution network, a backup automatic switching device is installed in the substation to realize automatic switching of the backup power supply. The backup automatic switching logic and related protection of the 10kV backup automatic switching device of a conventional substation generally include: (1) backup automatic switching mode 1: power supply 1 is the main supply. When power supply 1 fails, power supply 2 is automatically switched; (2) backup automatic switching mode 2: power supply 2 is the main supply. When power supply 2 fails, power supply 1 is automatically switched; (3) backup automatic switching mode 3: power supplies 1 and 2 are respectively the main supply. When power supply 1 fails, the automatic switching is carried out in sections; (4) backup automatic switching mode 4: power supplies 1 and 2 are respectively the main supply. When power supply 2 fails, the automatic switching is carried out in sections; (5) overload shedding (two rounds): the closing action of backup automatic switching mode 1 and 3 starts the overload shedding function of power supply 2, and the closing action of backup automatic switching mode 2 and 4 starts the overload shedding function of power supply 1; (6) overcurrent acceleration protection (stage 1): the overcurrent can be switched in and out by re-voltage, and the protection is accelerated after the automatic switching is carried out in sections; (7) zero sequence acceleration protection (stage 1): the protection is accelerated after the automatic switching is carried out in sections.

[0004] The judgment criteria for the backup automatic switching logic and related protection of the 10kV backup automatic switching device of a conventional substation generally include: (1) judging whether there is voltage or no voltage based on the voltage of the two busbars; (2) judging the backup automatic switching action logic based on the trip position nodes of power source 1, power source 2 and section switch; (3) judging that the power switch has tripped based on the current of one phase of the two power supply lines, and at the same time preventing the backup automatic switching from malfunctioning due to a three-phase disconnection of the PT. In addition, there are two conditions for locking the backup automatic switching, including: (1) executing manual trip locking of the backup automatic switching (or connecting the manual trip contact to the main locking input terminal of the backup automatic switching device) based on the closed position signals of power source 1, power source 2 and section switch; (2) locking the section switch backup automatic switching based on the main backup protection action of 1# and 2# main transformers.

[0005] The automatic switching device also features a configurable tripping output, typically used to disconnect 10kV lines connected to busbars I and II, which are connected to smaller power sources, and to reduce overloads. Furthermore, to improve power supply quality, power supply departments are currently minimizing the impact of power outages on customers and the impact on electricity sales to distributed generation customers.

[0006] From the above analysis, it can be seen that the 10kV standby automatic switching device in the substation has four major deficiencies: (1) It is not compatible with the development of distributed photovoltaic power sources. Energy security is related to the overall economic and social development, and my country's photovoltaic products have formed a strong competitiveness in the international market. The current standby automatic switching logic treats the 10kV line with distributed photovoltaic power as a small power source. When a fault occurs in the power grid, the small power source is first connected and quickly isolated from the power grid. After the 10kV busbar is tested to be without pressure, the standby power switching instruction is finally executed. This standby automatic switching logic cannot reflect the superiority of distributed power supply safety and flexible power supply. (2) Lack of selectivity and "mis-cutting" of customer power lines. The current distributed photovoltaic access situation and development trend faced by the 10kV outgoing line of the substation is that in addition to the original pure power load, there are also photovoltaic power source point access types such as indoor 220V, area 380V, and 10kV line T-connection, showing the characteristics of multi-level, wide range, random distribution, and unstable output. If the backup and automatic switching logic treats these 10kV outgoing lines as small power sources, the original customer load will be "mistakenly tripped", reducing the customer's power supply reliability and worsening the power consumption perception. (3) Lack of adaptability, some criteria are invalid. One of the important criteria in the current backup and automatic switching logic is "detection of no pressure". With the widespread access of distributed power sources, this criterion is no longer applicable and comprehensive, and is not compatible with the development of the new distribution network. (4) The criteria are not comprehensive. On the one hand, with the widespread access of distributed power sources, the new 10kV distribution network has transformed from a traditional "passive" one-way radiation network to an "active" two-way interactive system. On the other hand, as far as distributed photovoltaic power sources are concerned, there are three types of states: "no light, no power generation", "sufficient sunlight, causing power to be fed back to the substation", and the intermediate transition process between the two. The current criteria do not take these into account. Summary of the Invention

[0007] In order to solve the above problems, the present invention proposes a control method and system for the 10kV side standby automatic switching of substations under the condition of widespread access of distributed photovoltaics, which can improve the current standby automatic switching judgment criteria and action logic and adapt to the development of new "active" bidirectional interactive distribution networks.

[0008] The technical solution adopted by the present invention to solve the technical problem is:

[0009] In a first aspect, an embodiment of the present invention provides a method for controlling a 10 kV side standby automatic switching of a substation under distributed photovoltaic widespread access, comprising the following steps:

[0010] Step 1: When the incoming line switch of the 1# main transformer or the 2# main transformer is tripped and the current is 0, or the section switch is tripped and the section current is 0, obtain the bus voltage U and perform the standby automatic switching operation;

[0011] Step 2: If 85% UN≤U<110% UN, execute the synchronization check and automatic switching, and UN is the rated voltage; if the frequency f exceeds the range of 47.5Hz-50.2Hz, go to step 4;

[0012] Step 3: If 50% UN ≤ U < 85% UN, cut off the appropriate load-carrying line (power-carrying line) based on power calculation, and continue within 2 seconds until 85% UN ≤ U < 110% UN is satisfied, then go to step 2; if the state of 50% UN ≤ U < 85% UN lasts for more than 2 seconds, cut off all 10kV power-carrying lines on the corresponding busbars of the 1# and 2# main transformers, and perform the normal no-voltage standby automatic re-start operation;

[0013] In step 4, if U < 50% UN, based on power calculation, the appropriate load-carrying line is disconnected within 0.2s until 50% UN ≤ U < 85% UN, 85% UN ≤ U < 110% UN, or 85% UN ≤ U < 110% UN is met step by step, and then the process goes to step 2. If the U < 50% UN state lasts for more than 0.2s, all 10kV power-carrying lines on the corresponding busbars of the 1# and 2# main transformers are disconnected, and the normal no-voltage standby automatic re-transfer logic is executed.

[0014] In step 5, if 110% UN ≤ U < 135% UN, the appropriate power transmission line is disconnected based on power calculation, and the process continues for 2 seconds until 85% UN ≤ U < 110% UN, then the process goes to step 2. If the state of 110% UN ≤ U < 135% UN lasts for more than 2 seconds, all 10kV power transmission lines on the corresponding busbars of the 1# and 2# main transformers are disconnected, and the normal no-voltage standby automatic re-transfer logic is executed.

[0015] In step 6, if 135% UN≤U, the appropriate power transmission line is cut off after power calculation, and within 0.2s, it is gradually satisfied that 110% UN≤U<135%, 85% UN≤U<110% UN, or 85% UN≤U<110% UN is directly satisfied, and then go to step 2; if the 135% UN≤U state lasts for more than 0.2s, all the 10kV power transmission lines on the corresponding busbars of the 1# main transformer and the 2# main transformer are cut off, and the normal no-voltage standby automatic re-transfer logic is executed.

[0016] As a possible implementation of this embodiment, the execution of the automatic switching of the test equipment includes:

[0017] Determine whether the high-voltage side voltage of the 1# and 2# main transformers is synchronized with the low-voltage busbar;

[0018] The synchronization check and standby automatic switching is carried out, and the synchronization check and standby automatic switching is divided into the first standby automatic switching mode, the second standby automatic switching mode, the third standby automatic switching mode and the fourth standby automatic switching mode according to the different main and standby power supplies.

[0019] As a possible implementation of this embodiment, determining whether the high-voltage side voltages of the 1# main transformer and the 2# main transformer are synchronized with the low-voltage bus includes:

[0020] If the high-voltage side voltage of the 1# and 2# main transformers is synchronized with the low-voltage bus, the high-voltage side voltage of the 1# and 2# main transformers is converted into the low-voltage side voltage by the transformation ratio and phase angle, and the voltage amplitudes and phase angles of the two are compared. When the voltage amplitude difference ≤ the amplitude difference setting value and the voltage phase angle difference ≤ the phase angle difference setting value, the synchronization check succeeds and the synchronization closing conditions are met. Otherwise, the synchronization check fails.

[0021] If the synchronization check delay time t does not meet the synchronization check conditions within the set time, the synchronization check fails;

[0022] If the sectionalizing switch is automatically switched on and the low-voltage busbars of the 1# main transformer and the 2# main transformer are synchronized, the transformation ratio and phase angle conversion will not be performed.

[0023] As a possible implementation of this embodiment, the first standby automatic switching mode is that the 1# main transformer is the primary supply. When the 1# main transformer loses power, the 2# main transformer is automatically switched. The incoming lines of the 1# main transformer or the 2# main transformer are respectively power supply 1 or power supply 2, and their corresponding switches are respectively 1DL / 1DL-high or 2DL / 2DL-high. The currents of 1DL / 1DL-high and 2DL / 2DL-high are respectively I1 and I2. The section switch is 3DL, and its current is I3. The high-voltage side voltages of the 1# main transformer and the 2# main transformer are respectively UL1 and UL2, and the measured low-voltage side bus voltages of the 1# main transformer and the 2# main transformer are respectively U1 and U2.

[0024] The specific process of the first automatic standby start-up method is as follows:

[0025] (1) The charging condition is the same as the conventional standby automatic transfer logic. The discharging condition is different from the conventional standby automatic transfer logic. The detection of no voltage on the high-voltage side of the 2# main transformer UL2 is used as a necessary discharging condition.

[0026] (2) When charging is completed, if the conditions of "1DL / 1DL-high trip, in the open position", "I1 < power supply 1 no-current set value", "UL2 has pressure", and "related soft pressure plate and control word of standby automatic transfer are put into use" are all met, the standby automatic transfer is started; after the delay Tt1, the power supply 1 switch 1DL is tripped. After confirming that 1DL has tripped, after the delay Th2, at the same time 85% UN≤U2<110% UN, the "UL2 and U2 synchronization check" judgment is carried out, and the synchronous closing conditions are met, and the power supply 2 switch is closed;

[0027] (3) When charging is completed, if 3DL is tripped and there is no current, and the conditions of "UL2 has pressure" and "the related soft pressure plate and control word of the standby automatic transfer are put into operation" are met, the standby automatic transfer is started; after the delay Tt1, the section switch 3DL is tripped; after confirming that 3DL has tripped, all 10kV lines that send power on the low-voltage side bus of the 1# main transformer are cut off to prevent the formation of an island through the low-voltage side bus of the 1# main transformer; after the delay Th2, at the same time, 85% UN≤U2<110% UN is judged as "UL2 and U2 synchronization check", and the synchronous closing conditions are met, and the power supply 2 switch is closed;

[0028] (4) When charging is completed, if the backup protection of the 1# main transformer is activated and the conditions "I1 < power supply 1 no-current setting value" and "UL2 has pressure" and "the backup automatic switch-on related soft pressure plate and control word are activated" are met, the backup automatic switch-on is started; after a delay of Tt1, the section switch 3DL is tripped; after confirming that 3DL has tripped, all 10kV lines that send power on the low-voltage side bus of the 1# main transformer are cut off to prevent the formation of an island through the low-voltage side bus of the 1# main transformer; after a delay of Th2, and at the same time 85% UN≤U2<110% UN, the "UL2 and U2 synchronization check" judgment is performed, and the synchronous closing conditions are met, and the power supply 2 switch is closed.

[0029] As a possible implementation of this embodiment, the second standby automatic switching mode is that the 2# main transformer is the main supply. When the 2# main transformer loses power, the 1# main transformer is automatically switched. The specific standby automatic switching process of the second standby automatic switching mode is similar to that of the first standby automatic switching mode.

[0030] As a possible implementation of this embodiment, the third standby automatic switching mode is that the 1# main transformer and the 2# main transformer are respectively the main supply. When the 1# main transformer loses power, the section switch 3DL is automatically switched. The specific standby automatic switching process of the third standby automatic switching mode is as follows:

[0031] (1) The charging conditions are the same as those of the conventional standby automatic transfer logic. The discharging conditions are different from those of the conventional standby automatic transfer logic, except for the condition that U1 and U2 have no voltage.

[0032] (2) When charging is completed, if the conditions of "1DL / 1DL-high trip, in the open position", "I1 < power supply 1 no-current set value", and "spare automatic switch related soft pressure plate and control word input" are met, the spare automatic switch is started; after the delay Tt1, the power supply 1 switch 1DL is tripped; after confirming that 1DL has tripped, after the delay Th3, at the same time, 85% UN≤U2<110% UN is used to perform the "U2 and U1 synchronization check" judgment, and the synchronous closing conditions are met, and the section switch is closed.

[0033] As a possible implementation of this embodiment, the fourth standby automatic switching mode is that the 1# main transformer and the 2# main transformer are respectively the main supply, and when the 2# main transformer loses power, the section switch 3DL is automatically switched; the specific standby automatic switching process of the fourth standby automatic switching mode is similar to that of the third standby automatic switching mode.

[0034] As a possible implementation of this embodiment, after closing the sectionalizing switch, it is opened for 3 seconds to start the sectionalizing automatic post-closing acceleration protection.

[0035] As a possible implementation of this embodiment, the acceleration protection includes overcurrent acceleration protection and zero-sequence acceleration protection, wherein the overcurrent acceleration protection can be selected to be locked by re-pressure.

[0036] As a possible implementation of this embodiment, after the backup automatic switching is successful, if the automatic switching power supply capacity is insufficient, overload shedding is performed;

[0037] The overload shedding includes forward overload shedding and reverse overload shedding.

[0038] The forward overload shedding has the same action logic as the conventional standby automatic transfer logic, i.e., it cuts off a portion of the secondary loads; the reverse overload shedding cuts off a portion of the distributed photovoltaic lines agreed upon in the previous agreement to ensure that the transformer does not overload by reverse power transmission.

[0039] As a possible implementation of this embodiment, the upward power transmission line refers to a line where power is directed to a bus, and the downward power transmission line refers to a line where power is directed to a line.

[0040] In the second aspect, an embodiment of the present invention provides a 10 kV side standby automatic start-up system for a substation under widespread distributed photovoltaic access, including a hardware connection framework and software standby automatic start-up action logic; the hardware connection framework includes a cable transmission network and an optical fiber transmission network; the software standby automatic start-up action logic includes a functional module of a standby automatic start-up device and based on five interval conditions of bus voltage U<50%UN, 50%UN≤U<85%UN, 85%UN≤U<110%UN, 110%UN≤U<135%UN, 135%UN≤U and considering the frequency condition of 47.5Hz≤f≤50.2Hz under pressure, the standby automatic start-up logic is divided into synchronous standby automatic start-up and traditional no-pressure standby start-up logic.

[0041] As a possible implementation method of this embodiment, the cable transmission network is a standby automatic switching device that collects the position status information of the incoming line switches 1DL / 1DL-high, 2DL / 2DL-high and 10 kV section switch 3DL of the 1# main transformer and the 2# main transformer through cable connections and their corresponding currents I1, I2, I3, the 10 kV I bus and II bus voltages, and the high-voltage side voltages UL1 and UL2 of the 1# main transformer and the 2# main transformer; the optical fiber transmission network is a standby automatic switching device that collects the current, voltage or power of each 10 kV outgoing line of the I bus and the II bus through optical fiber connections, and the multi-in-one devices of each outgoing line of the I bus are collected to the optical switch of the I bus, and the multi-in-one devices of each outgoing line of the II bus are collected to the optical switch of the II bus; the optical switches of the I bus and the II bus are each connected to the standby automatic switching device through an optical fiber.

[0042] As a possible implementation of this embodiment, the functional modules of the standby automatic switching device include a state quantity identification module, a power calculation and direction identification module, a synchronization detection module, a frequency identification module, a standby switching logic judgment and action module, and a segmented acceleration module;

[0043] The state quantity identification module is used to identify the operating state of the system by accessing the position information of the 1# main transformer, the 2# main transformer incoming line switches 1DL / 1DL-high, 2DL / 2DL-high and the section switch 3DL of the standby automatic transfer device, as well as the current information of the 1# main transformer, the 2# main transformer and the section switch, to prepare for the action logic execution of the four standby automatic transfer modes of power supply standby automatic transfer and section standby automatic transfer;

[0044] The power calculation and direction identification module is used to calculate the power of each interval by using the current and voltage of each 10 kV outgoing line interval of the backup automatic switching device connected via optical fiber, and to determine whether the corresponding interval is sending power upward or downward based on the power direction; upward power refers to power directed to the bus, and downward power refers to power directed to the line;

[0045] The synchronization check module is used to detect whether the voltage amplitude and phase angle of the power supply line voltage and the 10 kV bus voltage meet the synchronization closing requirements in the power supply standby automatic switching mode;

[0046] The frequency identification module is used to determine whether the frequency of the 10 kV bus to be closed meets the frequency requirement, that is, 47.5 Hz ≤ f ≤ 50.2 Hz, after the original power supply switch is disconnected and before the standby automatic switch is closed;

[0047] The standby logic judgment and action module is used to control the 10kV side standby automatic switching of the substation under the condition of widespread access of distributed photovoltaics;

[0048] The post-segment acceleration module is used for overcurrent protection after the segment switch is closed.

[0049] As a possible implementation of this embodiment, the functional module of the standby automatic switching device is specifically used to:

[0050] (1) Condition 1 judgment and its action logic: If it is within the range of 85% UN ≤ U < 110% UN, the synchronization check and automatic switching are executed; if it is outside the range of 47.5Hz-50.2Hz, the process is transferred to "Condition 3 judgment and its action logic";

[0051] (2) Condition 2 judgment and its action logic: within the range of 50% UN ≤ U < 85% UN, the appropriate downlink load line is cut off according to power calculation, and within 2 seconds, until 85% UN ≤ U < 110% UN is satisfied, the process of "Condition 1 judgment and its action logic" is transferred to; if the state of 50% UN ≤ U < 85% UN lasts for more than 2 seconds, all uplink power 10 kV lines on busbars I and II are cut off, and the normal no-voltage standby automatic re-transfer logic is executed;

[0052] (3) Condition 3 judgment and its action logic: Within the range of U < 50% UN, the appropriate downlink load line is cut off after power calculation, and within 0.2s, the conditions of 50% UN ≤ U < 85% UN, 85% UN ≤ U < 110% UN, or 85% UN ≤ U < 110% UN are met step by step, and then the process of "Condition 1 judgment and its action logic" is transferred to; if the U < 50% UN state lasts for more than 0.2s, all uplink power 10kV lines on busbars I and II are cut off, and the normal no-voltage standby automatic re-transfer logic is executed;

[0053] (4) Condition 4 judgment and its action logic: Within the range of 110% UN ≤ U < 135% UN, the appropriate power transmission line is cut off after power calculation, and within 2 seconds, the state of 85% UN ≤ U < 110% UN is satisfied, and then the process of "Condition 1 judgment and its action logic" is transferred to; if the state of 110% UN ≤ U < 135% UN lasts for more than 2 seconds, all power transmission 10 kV lines on busbars I and II are cut off, and the normal no-voltage standby automatic re-transfer logic is executed;

[0054] (5) Judgment of condition 5 and its action logic: within the range of 135% UN≤U, the appropriate power transmission line is cut off after power calculation, and within 0.2s, it is gradually satisfied that 110% UN≤U<135%, 85% UN≤U<110% UN, or 85% UN≤U<110% UN is directly satisfied, and then the process of "judgment of condition 1 and its action logic" is entered; if the 135% UN≤U state lasts for more than 0.2s, all the 10kV power transmission lines on bus I and bus II are cut off, and the normal no-voltage standby automatic re-transfer logic is executed.

[0055] The technical solution of the embodiment of the present invention can have the following beneficial effects:

[0056] The present invention is used for the 10 kV side standby automatic switching action logic method of substations supplying power to 10 kV distribution networks, such as 110 kV and 220 kV, under the conditions of widespread distributed photovoltaic access, especially when 220 V and 380 V household power is widely accessed to distribution stations and customer distribution rooms. The present invention improves the currently used standby automatic switching judgment criteria and action logic, adapts to the development of new "active" bidirectional interactive distribution networks, and meets the characteristics of pure power load access of customers on 10 kV lines of substations, multi-level and wide-range access of distributed photovoltaics, and its randomness and unstable output. The present invention minimizes the impact on electricity consumption and power generation of customers (including electricity users and power generation customers).

[0057] The present invention prioritizes safety, ensuring customer electricity availability, and distributed photovoltaic grid-connected power generation. Compared to existing backup and automatic switching logic methods, the present invention has the following advantages:

[0058] (1) Accurately select the optimal combination of cut-off lines. Conventional 10kV lines for automatic switching are pre-selected. The present invention can accurately select the optimal cut-off scheme based on the power flow size and direction of each 10kV line, eliminating the need for manual pre-selection. In addition, in new power systems, the line load size and power flow direction are dynamically changing, and manual pre-selection of cut-off lines has inherent limitations.

[0059] (2) Realize automatic switching of standby switches without power outage. Conventional automatic switching of standby switches is based on the judgment of no-voltage state, while the present invention judges based on the switch position state and the network topology without current, thus realizing automatic switching of standby switches when detecting synchronization and automatic switching of standby switches when detecting no-voltage state.

[0060] (3) Strong adaptability. The present invention can adaptively complete the standby automatic switching operation regardless of whether the 10kV outgoing line of the substation is connected to distributed photovoltaics, at which level (distributed access, centralized access with a public transformer, centralized access with a dedicated transformer), at which voltage level the photovoltaics are connected (220V, 380V, 10kV), and regardless of the size of the photovoltaic access capacity.

[0061] (4) Good compatibility with existing backup automatic switching devices. Similar to conventional backup automatic switching devices, the current and switch status of power supply 1, power supply 2 and the segments, the voltage of bus I and bus II, and the command issuance of trip switches 1DL (or 1DL-high), 2DL (or 2DL-high), and 3DL are still connected by cables. The signal source, transmission method, and access method of the backup automatic switching device are the same.

[0062] (5) Simple access to new functions. The difference from conventional backup automatic switching devices is that only two optical fiber access ports are added, that is, the transmission of telemetry, telesignaling, and remote control of the 10 kV outgoing line interval is connected through optical fiber links. The current, voltage, power, switch status, and trip and close commands of each 10 kV outgoing line interval are completed through two optical switches and two optical cables, which simplifies the access structure. It overcomes the shortcomings of the method of connecting all distributed photovoltaic access point information to the backup automatic switching device, such as wide range, multiple levels, random distribution, complex structure, and high implementation difficulty.

[0063] (6) The present invention is in line with the development trend of new power systems and is consistent with the development of distributed photovoltaic power sources. It fully considers the transformation of the new 10kV distribution network from the traditional "passive" one-way radiation network to the "active" two-way interactive system. It is consistent with the "three states of distributed photovoltaic power sources: 'no light, no power generation', 'sufficient sunlight, causing power to be fed back to the substation', and the intermediate transition process between the two." BRIEF DESCRIPTION OF THE DRAWINGS

[0064] Figure 1 This is a flow chart showing a method for controlling 10 kV side backup automatic switching of a substation under widespread access of distributed photovoltaic power generation according to an exemplary embodiment;

[0065] Figure 2 This is a diagram illustrating an example of a 10 kV main wiring and outgoing line structure of a distribution network substation according to an exemplary embodiment;

[0066] Figure 3 This is a physical connection diagram of a 10 kV side backup automatic switching system of a substation under distributed photovoltaic wide access according to an exemplary embodiment;

[0067] Figure 4 This is a functional module diagram of a standby automatic start-up device according to an exemplary embodiment;

[0068] Figure 5 This is a general flow chart of a backup automatic start logic according to an exemplary embodiment;

[0069] Figure 6 is a logic flow chart of a detection period according to an exemplary embodiment;

[0070] Figure 7 This is an action logic diagram of a standby automatic start mode 1 and a standby automatic start mode 2 according to an exemplary embodiment;

[0071] Figure 8 This is an action logic diagram of a standby automatic start mode 3 and a standby automatic start mode 4 according to an exemplary embodiment;

[0072] Figure 9 The figure is a logic diagram showing an overload reduction action of power supply 1 and power supply 2 according to an exemplary embodiment. DETAILED DESCRIPTION

[0073] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0074] In order to clearly illustrate the technical features of this solution, the present invention is described in detail below through specific implementation methods and in conjunction with the accompanying drawings. The disclosure below provides many different embodiments or examples for realizing different structures of the present invention. In order to simplify the disclosure of the present invention, the components and settings of specific examples are described below. In addition, the present invention may repeat reference numbers and / or letters in different examples. This repetition is for the purpose of simplicity and clarity and does not itself indicate the relationship between the various embodiments and / or settings discussed. It should be noted that the components illustrated in the accompanying drawings are not necessarily drawn to scale. The present invention omits descriptions of well-known components and processing technologies and processes to avoid unnecessary limitations on the present invention.

[0075] like Figure 1 As shown, an embodiment of the present invention provides a control method for 10 kV side standby automatic switching of a substation under distributed photovoltaic wide access, including the following steps:

[0076] Step 1: When the incoming line switch of the 1# main transformer or the 2# main transformer is tripped and the current is 0, or the section switch is tripped and the section current is 0, obtain the bus voltage U and perform the standby automatic switching operation;

[0077] Step 2: If 85% UN≤U<110% UN, execute the synchronization check and automatic switching, and UN is the rated voltage; if the frequency f exceeds the range of 47.5Hz-50.2Hz, go to step 4;

[0078] Step 3: If 50% UN ≤ U < 85% UN, cut off the appropriate load-carrying line based on power calculation, and continue within 2 seconds until 85% UN ≤ U < 110% UN is satisfied, then proceed to Step 2. If the 50% UN ≤ U < 85% UN state lasts for more than 2 seconds, cut off all 10kV power-carrying lines on the busbars corresponding to the 1# and 2# main transformers, and perform the normal no-voltage standby automatic re-transfer operation.

[0079] In step 4, if U < 50% UN, based on power calculation, the appropriate load-carrying line is disconnected within 0.2s until 50% UN ≤ U < 85% UN, 85% UN ≤ U < 110% UN, or 85% UN ≤ U < 110% UN is met step by step, and then the process goes to step 2. If the U < 50% UN state lasts for more than 0.2s, all 10kV power-carrying lines on the corresponding busbars of the 1# and 2# main transformers are disconnected, and the normal no-voltage standby automatic re-transfer logic is executed.

[0080] In step 5, if 110% UN ≤ U < 135% UN, the appropriate power transmission line is disconnected based on power calculation, and the process continues for 2 seconds until 85% UN ≤ U < 110% UN, then the process goes to step 2. If the state of 110% UN ≤ U < 135% UN lasts for more than 2 seconds, all 10kV power transmission lines on the corresponding busbars of the 1# and 2# main transformers are disconnected, and the normal no-voltage standby automatic re-transfer logic is executed.

[0081] In step 6, if 135% UN≤U, the appropriate power transmission line is cut off after power calculation, and within 0.2s, it is gradually satisfied that 110% UN≤U<135%, 85% UN≤U<110% UN, or 85% UN≤U<110% UN is directly satisfied, and then go to step 2; if the 135% UN≤U state lasts for more than 0.2s, all the 10kV power transmission lines on the corresponding busbars of the 1# main transformer and the 2# main transformer are cut off, and the normal no-voltage standby automatic re-transfer logic is executed.

[0082] As a possible implementation of this embodiment, the execution of the automatic switching of the test equipment includes:

[0083] Determine whether the high-voltage side voltage of the 1# and 2# main transformers is synchronized with the low-voltage busbar;

[0084] The synchronization check and standby automatic switching is carried out, and the synchronization check and standby automatic switching is divided into the first standby automatic switching mode, the second standby automatic switching mode, the third standby automatic switching mode and the fourth standby automatic switching mode according to the different main and standby power supplies.

[0085] As a possible implementation of this embodiment, determining whether the high-voltage side voltages of the 1# main transformer and the 2# main transformer are synchronized with the low-voltage bus includes:

[0086] If the high-voltage side voltage of the 1# and 2# main transformers is synchronized with the low-voltage bus, the high-voltage side voltage of the 1# and 2# main transformers is converted into the low-voltage side voltage by the transformation ratio and phase angle, and the voltage amplitudes and phase angles of the two are compared. When the voltage amplitude difference ≤ the amplitude difference setting value and the voltage phase angle difference ≤ the phase angle difference setting value, the synchronization check succeeds and the synchronization closing conditions are met. Otherwise, the synchronization check fails.

[0087] If the synchronization check delay time t does not meet the synchronization check conditions within the set time, the synchronization check fails;

[0088] If the sectionalizing switch is automatically switched on and the low-voltage busbars of the 1# main transformer and the 2# main transformer are synchronized, the transformation ratio and phase angle conversion will not be performed.

[0089] As a possible implementation of this embodiment, the first standby automatic switching mode is that the 1# main transformer is the primary supply. When the 1# main transformer loses power, the 2# main transformer is automatically switched. The incoming lines of the 1# main transformer or the 2# main transformer are respectively power supply 1 or power supply 2, and their corresponding switches are respectively 1DL / 1DL-high or 2DL / 2DL-high. The currents of 1DL / 1DL-high and 2DL / 2DL-high are respectively I1 and I2. The section switch is 3DL, and its current is I3. The high-voltage side voltages of the 1# main transformer and the 2# main transformer are respectively UL1 and UL2, and the measured low-voltage side bus voltages of the 1# main transformer and the 2# main transformer are respectively U1 and U2.

[0090] The specific process of the first automatic standby start-up method is as follows:

[0091] (1) The charging condition is the same as the conventional standby automatic transfer logic. The discharging condition is different from the conventional standby automatic transfer logic. The detection of no voltage on the high-voltage side of the 2# main transformer UL2 is used as a necessary discharging condition.

[0092] (2) When charging is completed, if the conditions of "1DL / 1DL-high trip, in the open position", "I1 < power supply 1 no-current set value", "UL2 has pressure", and "related soft pressure plate and control word of standby automatic transfer are put into use" are all met, the standby automatic transfer is started; after the delay Tt1, the power supply 1 switch 1DL is tripped. After confirming that 1DL has tripped, after the delay Th2, at the same time 85% UN≤U2<110% UN, the "UL2 and U2 synchronization check" judgment is carried out, and the synchronous closing conditions are met, and the power supply 2 switch is closed;

[0093] (3) When charging is completed, if 3DL is tripped and there is no current, and the conditions of "UL2 has pressure" and "the related soft pressure plate and control word of the standby automatic transfer are put into operation" are met, the standby automatic transfer is started; after the delay Tt1, the section switch 3DL is tripped; after confirming that 3DL has tripped, all 10kV lines that send power on the low-voltage side bus of the 1# main transformer are cut off to prevent the formation of an island through the low-voltage side bus of the 1# main transformer; after the delay Th2, at the same time, 85% UN≤U2<110% UN is judged as "UL2 and U2 synchronization check", and the synchronous closing conditions are met, and the power supply 2 switch is closed;

[0094] (4) When charging is completed, if the backup protection of the 1# main transformer is activated and the conditions "I1 < power supply 1 no-current setting value" and "UL2 has pressure" and "the backup automatic switch-on related soft pressure plate and control word are activated" are met, the backup automatic switch-on is started; after a delay of Tt1, the section switch 3DL is tripped; after confirming that 3DL has tripped, all 10kV lines that send power on the low-voltage side bus of the 1# main transformer are cut off to prevent the formation of an island through the low-voltage side bus of the 1# main transformer; after a delay of Th2, and at the same time 85% UN≤U2<110% UN, the "UL2 and U2 synchronization check" judgment is performed, and the synchronous closing conditions are met, and the power supply 2 switch is closed.

[0095] As a possible implementation of this embodiment, the second standby automatic switching mode is that the 2# main transformer is the main supply. When the 2# main transformer loses power, the 1# main transformer is automatically switched. The specific standby automatic switching process of the second standby automatic switching mode is similar to that of the first standby automatic switching mode.

[0096] As a possible implementation of this embodiment, the third standby automatic switching mode is that the 1# main transformer and the 2# main transformer are respectively the main supply. When the 1# main transformer loses power, the section switch 3DL is automatically switched. The specific standby automatic switching process of the third standby automatic switching mode is as follows:

[0097] (1) The charging conditions are the same as those of the conventional standby automatic transfer logic. The discharging conditions are different from those of the conventional standby automatic transfer logic, except for the condition that U1 and U2 have no voltage.

[0098] (2) When charging is completed, if the conditions of "1DL / 1DL-high trip, in the open position", "I1 < power supply 1 no-current set value", and "spare automatic switch related soft pressure plate and control word input" are met, the spare automatic switch is started; after the delay Tt1, the power supply 1 switch 1DL is tripped; after confirming that 1DL has tripped, after the delay Th3, at the same time, 85% UN≤U2<110% UN is used to perform the "U2 and U1 synchronization check" judgment, and the synchronous closing conditions are met, and the section switch is closed.

[0099] As a possible implementation of this embodiment, the fourth standby automatic switching mode is that the 1# main transformer and the 2# main transformer are respectively the main supply, and when the 2# main transformer loses power, the section switch 3DL is automatically switched; the specific standby automatic switching process of the fourth standby automatic switching mode is similar to that of the third standby automatic switching mode.

[0100] As a possible implementation of this embodiment, after closing the sectionalizing switch, it is opened for 3 seconds to start the sectionalizing automatic post-closing acceleration protection.

[0101] As a possible implementation of this embodiment, the acceleration protection includes overcurrent acceleration protection and zero-sequence acceleration protection, wherein the overcurrent acceleration protection can be selected to be locked by re-pressure.

[0102] As a possible implementation of this embodiment, after the backup automatic switching is successful, if the automatic switching power supply capacity is insufficient, overload shedding is performed;

[0103] The overload shedding includes forward overload shedding and reverse overload shedding.

[0104] The forward overload shedding has the same action logic as the conventional standby automatic transfer logic, i.e., it cuts off a portion of the secondary loads; the reverse overload shedding cuts off a portion of the distributed photovoltaic lines agreed upon in the previous agreement to ensure that the transformer does not overload by reverse power transmission.

[0105] As a possible implementation of this embodiment, the upward power transmission line refers to a line where power is directed to a bus, and the downward power transmission line refers to a line where power is directed to a line.

[0106] An embodiment of the present invention provides a 10 kV side standby automatic transfer system for a substation with widespread distributed photovoltaic access, comprising a hardware connection framework and software standby automatic transfer action logic; the hardware connection framework comprises a cable transmission network and an optical fiber transmission network; the software standby automatic transfer action logic comprises a functional module of a standby automatic transfer device and, based on five interval conditions of bus voltage U<50%UN, 50%UN≤U<85%UN, 85%UN≤U<110%UN, 110%UN≤U<135%UN, 135%UN≤U and considering the frequency condition of 47.5Hz≤f≤50.2Hz under pressure, divides the standby automatic transfer logic into synchronous standby automatic transfer and traditional no-pressure standby transfer logic.

[0107] The clues and development trend of 10kV distribution network, such as Figure 2 As shown in the figure, in addition to connecting to conventional customer loads, the 10 kV outgoing line of the 110 kV substation can also provide distributed photovoltaic access in three ways: decentralized access (380V, 220V), centralized access via a public transformer (380V), and centralized access via a dedicated transformer (10kV). In addition, it also includes dedicated line access for small power sources (10kV) and dedicated line access for customers (10kV).

[0108] like Figure 2 As shown, the present invention is directed to a new type of distribution network substation 10 kV main wiring and outgoing line structure example diagram, which is also one of the applicable scenarios targeted by the present invention. Power supply 1, power supply 2, I bus and 10 kV outgoing line, II bus and 10 kV outgoing line. Power supply 1 includes 1# main transformer, 1# main transformer 110 kV incoming line and its PT (collecting voltage UL1), 1# main transformer 10 kV incoming line and its CT (collecting current I1), 1# main transformer 110 kV incoming line switch 1DL-high, 1# main transformer 10 kV incoming line switch 1DL, and power supply 2 is similar to power supply 1. Busbar I includes common 10kV outgoing lines 1-1, 1-2, ..., and 1-n (which account for the vast majority of outgoing lines) and 10kV dedicated lines (for some outgoing lines). Common 10kV outgoing lines connect to two types of loads: customer loads and photovoltaic power sources. PV power sources are divided into three tiers: centralized access via dedicated transformers (10kV), centralized access via public transformers (380V), and decentralized access (380V and 220V). These are interspersed among customer loads. 10kV dedicated lines are divided into dedicated lines for small power sources and dedicated lines for large customers. Busbar II is similar to Busbar I. Between Busbars I and II are section switches 3DL and section transformers (collecting current I3).

[0109] Figure 3This is a diagram of the physical connection relationship of the system of the present invention, which includes two categories. One category is cable connection, through which the standby automatic switching device collects the position status information of the 10 (110) kV incoming line switch 1DL (or 1DL-high), 2DL (or 2DL-high) and 10 kV section switch 3DL of the 1# and 2# main transformers and their corresponding I1, I2, I3 currents, 10 kV I bus and I bus voltages, and the high-voltage side voltages UL1 and UL2 of the 1# and 2# main transformers; the other category is optical fiber connection, through which the current, voltage or power of each 10 kV outgoing line of the I bus and II bus are collected, and the multi-in-one devices of each outgoing line of the I bus are collected to the optical switch of the I bus, and the multi-in-one devices of each outgoing line of the II bus are collected to the optical switch of the II bus. The optical switches of the I bus and II bus are each connected to the standby automatic switching device through one optical fiber. Note: An all-in-one device for 10 kV lines refers to a device that integrates protection, measurement, monitoring, and control functions. It is suitable for routine sampling and routine tripping in smart substations, and requires SV output or process-layer GOOSE input and output (Q / GDW10766-2015).

[0110] Figure 4 It is a functional module diagram of the standby automatic switching device, including state quantity identification, power calculation and direction identification, synchronization check, frequency identification, standby switching logic judgment and action, and acceleration after segmentation.

[0111] (1) The state quantity identification module is to identify the operating state of the system by accessing the position information of the 1# and 2# main transformer 10 (110) kV incoming line (power source 1 or power source 2) switches 1DL (or 1DL-high), 2DL (or 2DL-high) and section switch 3DL of the standby automatic transfer device, as well as the current information of power sources 1 and 2 and flowing through the section switch, so as to prepare for the action logic execution of the four standby automatic transfer modes of power supply standby automatic transfer and section standby automatic transfer.

[0112] (2) The power calculation and direction identification module calculates the power of each 10kV outgoing line bay connected to the backup automatic switching device via optical fiber, using the current and voltage. It also determines whether the corresponding bay is sending power upstream or downstream based on the power direction. Power directed toward the busbar is sending power upstream, while power directed toward the line is sending power downstream.

[0113] (3) The synchronization check module is used to check whether the voltage amplitude and phase angle of the power supply line voltage and the 10 kV bus voltage meet the synchronization closing requirements in the power supply standby automatic switching mode.

[0114] (4) The frequency identification module refers to whether the frequency of the 10 kV bus to be closed meets the frequency requirement, that is, 47.5 Hz ≤ f ≤ 50.2 Hz, after the original power supply switch is disconnected and before the standby automatic switch is closed.

[0115] (5) The standby automatic start logic judgment and action module refers to the overall standby automatic start logic process and the action logic of the four modes of standby automatic start. Please refer to the subsequent description of this patent for details.

[0116] (6) The post-segment acceleration module refers to the overcurrent protection function taken to prevent the segment from closing due to faults under the two types of segment backup automatic switching modes.

[0117] Figure 5 This is the overall flow chart of the backup automatic transfer logic. Based on the five interval conditions of bus voltage U < 50% UN, 50% UN ≤ U < 85% UN, 85% UN ≤ U < 110% UN, 110% UN ≤ U < 135% UN, and 135% UN ≤ U, and considering the frequency condition of 47.5Hz ≤ f ≤ 50.2Hz under pressure, the present invention divides the backup automatic transfer logic into synchronous backup automatic transfer and traditional no-pressure backup automatic transfer logic. Among them, UN is the rated voltage of the low-voltage side (10 kV) busbars of the 1# and 2# main transformers, U (U1 for busbar I and U2 for busbar II) is the measured voltage of the low-voltage side busbar, and f is the measured frequency of the low-voltage side (10 kV) busbar. When the 1# or 2# main transformer 10 (110) kV incoming line (power source 1 or power source 2) switch 1DL (or 1DL-high) or 2DL (or 1DL-high) is tripped (TWJ1 or TWJ2=0) and the power source 1 or 2 current is 0 (I1, I2=0), or the section switch 3DL is tripped (TWJ=0) and the section current is 0 (I3=0), after the standby automatic transfer is started, it enters the following 5 interval conditions and their action logic.

[0118] (1) Condition 1 and its action logic: If the frequency is within the range of 85% UN ≤ U < 110% UN, the system executes the synchronization check and automatic switching. If the frequency exceeds the range of 47.5Hz-50.2Hz, the system proceeds to condition 3. According to technical standards, when the frequency at the grid connection point of the photovoltaic power generation system exceeds the range of 47.5Hz-50.2Hz, the photovoltaic system should stop supplying power to the grid within 0.2s.

[0119] (2) Condition 2 and its action logic: Within the range of 50% UN ≤ U < 85% UN, the appropriate downlink load line is disconnected based on power calculations until 85% UN ≤ U < 110% UN is satisfied within 2 seconds, at which point the process proceeds to "Condition 1 and its action logic." If the 50% UN ≤ U < 85% UN condition persists for more than 2 seconds, all uplink 10 kV power lines on busbars I and II are disconnected, and the normal no-voltage standby automatic re-connection logic is executed. According to technical standards, when 50% UN ≤ U < 85% UN, the photovoltaic power generation system should be tripped within 2 seconds.

[0120] (3) Condition 3 and its action logic: Within the range of U < 50% UN, the appropriate downlink load line is disconnected based on power calculations. Within 0.2s, the process continues until 50% UN ≤ U < 85% UN, 85% UN ≤ U < 110% UN, or 85% UN ≤ U < 110% UN is met step by step. The process then proceeds to "Condition 1 and its action logic." If the U < 50% UN state persists for more than 0.2s, all uplink 10kV power lines on busbars I and II are disconnected, and the conventional no-voltage standby automatic re-transfer logic is executed. According to technical standards, when U < 50% UN, the photovoltaic power generation system should be disconnected within 0.2s. During this transition period, the process may proceed to "Condition 2 and its action logic."

[0121] (4) Condition 4 and its action logic: Within the range of 110% UN ≤ U < 135% UN, the appropriate uplink power line is disconnected based on power calculation until 85% UN ≤ U < 110% UN is satisfied within 2 seconds, at which point the process proceeds to "Condition 1 and its action logic." If the 110% UN ≤ U < 135% UN state persists for more than 2 seconds, all uplink power 10 kV lines on busbars I and II are disconnected, and the normal no-voltage standby automatic re-connection logic is executed. According to technical standards, when 110% UN ≤ U < 135% UN, the PV system should be tripped within 2 seconds.

[0122] (5) Condition 5 and its action logic: Within the range of 135% UN≤U, the appropriate uplink power line is disconnected based on power calculation. Within 0.2s, the process continues until 110% UN≤U<135%, 85% UN≤U<110% UN, or 85% UN≤U<110% UN is met step by step. The process then proceeds to "Condition 1 and its action logic." If the 135% UN≤U state persists for more than 0.2s, all uplink power 10kV lines on busbars I and II are disconnected, and the conventional no-voltage standby automatic re-transfer logic is executed. According to technical standards, when 135% UN≤U, the photovoltaic power generation system should be disconnected within 0.2s. During the transition period, the process may proceed to "Condition 4 and its action logic."

[0123] Figure 6 This is a flow chart of the synchronization check logic. The synchronization check logic is as follows: if the high-voltage side voltages UL1 and UL2 of the 1# and 2# main transformers are synchronized with the low-voltage busbar, the high-voltage side voltages UL1 and UL2 of the main transformers need to be converted to the low-voltage side voltages of the main transformers by using the transformation ratio and phase angle (generally set to 10 kV and perform the corresponding 30° star angle transformation). Then, the voltage amplitudes and phase angles of the two are compared. When they meet the synchronous closing conditions of "voltage amplitude difference ≤ amplitude difference fixed value" and "voltage phase angle difference ≤ phase angle difference fixed value", the synchronization check is successful and the synchronous closing conditions are met. Otherwise, the synchronization check fails. The synchronization check delay time t can be adjusted. If the synchronization check conditions are not met within the set time, the synchronization check fails. If the sectionalizing switch is automatically closed, the synchronization check between the two sections of the low-voltage busbar (U1 and U2) does not require transformation ratio and phase angle conversion.

[0124] The automatic switching logic of the present invention complements and improves the conventional automatic switching logic, including conventional automatic switching logic and synchronous automatic switching logic. Figure 1 The substation low-voltage main wiring is shown, and the main transformer synchronization and standby automatic switching are introduced as follows.

[0125] Figure 7 This is the action logic diagram of standby automatic transfer mode 1 (first standby automatic transfer mode) and standby automatic transfer mode 2 (second standby automatic transfer mode). The action logic of standby automatic transfer mode 1 (power supply 1 is the main supply, when power supply 1 fails, power supply 2 is automatically transferred) is as follows:

[0126] (1) The charging condition is the same as the conventional standby automatic transfer logic. The discharging condition is different from the conventional standby automatic transfer logic. The detection of no voltage on the high-voltage side of the 2# main transformer UL2 should be taken as a necessary discharging condition.

[0127] (2) When charging is complete, if the conditions "1DL (or 1DL-high) trips, in the open position", "I1 < power supply 1 no-current set value", "UL2 has pressure", and "the backup automatic switch-related soft pressure plate and control word are enabled" are all met, the system starts; after a delay of Tt1, the power supply 1 switch (1DL) is tripped. After confirming that 1DL has tripped, after a delay of Th2, the system continues with "condition 1 and its action logic (85% UN ≤ U2 < 110% UN)" to perform "synchronization check of UL2 and U2". If the synchronous closing conditions are met, the power supply 2 switch is closed.

[0128] (3) When charging is completed, if the section trips secretly, that is, 3DL trips and there is no current, and the conditions of "UL2 has pressure" and "the related soft pressure plate and control word of the backup automatic switch are put into operation" are met, it will start; after a delay of Tt1, the section switch (3DL) will trip. After confirming that 3DL has tripped, all 10kV lines on the I bus that send power are cut off to prevent the formation of an island through the I bus. After a delay of Th2, "Condition 1 and its action logic (85% UN≤U2<110% UN)" are connected at the same time to perform "UL2 and U2 synchronization check". If the synchronous closing conditions are met, the power supply 2 switch will be closed.

[0129] (4) When charging is completed, if the backup protection of the 1# main transformer is activated and the conditions "I1 < power supply 1 no-current setting value" are met, and the conditions "UL2 has pressure" and "the backup automatic switching related soft pressure plate and control word are enabled" are met, then it will start; after a delay of Tt1, the section switch (3DL) will be tripped. After confirming that 3DL has tripped, all 10kV lines on the I bus that send power are cut off to prevent the formation of an island through the I bus. After a delay of Th2, "condition 1 and its action logic (85% UN≤U2<110% UN)" are connected at the same time to perform "UL2 and U2 synchronization check", and the synchronous closing conditions are met, and the power supply 2 switch is closed.

[0130] The action logic of backup automatic transfer mode 2 (power supply 2 is the main supply, when power supply 2 fails, power supply 1 is automatically transferred) is similar to that of backup automatic transfer mode 1.

[0131] Figure 8 This is the action logic diagram of standby automatic transfer mode 3 (the third standby automatic transfer mode) and standby automatic transfer mode 4 (the fourth standby automatic transfer mode). The action logic of standby automatic transfer mode 3 (power supplies 1 and 2 are respectively the main supply, and when power supply 1 fails, automatic transfer is divided into sections) is as follows:

[0132] (1) The charging condition is the same as the conventional standby automatic transfer logic. The discharging condition is different from the conventional standby automatic transfer logic, and the condition of judging that U1 and U2 have no voltage should be removed.

[0133] (2) When charging is completed, if the conditions "1DL (or 1DL-high) trips, in the open position", "I1 < power supply 1 no-current setting", and "the related soft pressure plate and control word of the standby automatic transfer are enabled" are all met, the circuit breaker starts; after a delay of Tt1, the power supply 1 switch (1DL) is tripped. After confirming that 1DL has tripped, after a delay of Th3, the circuit breaker is connected to "condition 1 and its action logic (85% UN ≤ U2 < 110% UN)" and the "U2 and U1 synchronization check" is carried out. If the synchronous closing conditions are met, the sectionalizer is closed.

[0134] The operation process of standby automatic transfer mode 4 (power supplies 1 and 2 are the main supplies respectively, and when power supply 2 fails, automatic transfer is divided into sections) is similar to that of standby automatic transfer mode 3.

[0135] After the backup automatic transfer mode 3 or 4 is closed, it is opened for 3s to start the accelerated protection after the segmented automatic transfer, which includes overcurrent accelerated protection and zero-sequence accelerated protection. The overcurrent accelerated protection can be selected to be locked after re-pressure.

[0136] Figure 9 This is the logic diagram for overload shedding for Power Sources 1 and 2. After the backup power source is successfully switched on, if the backup power source capacity is insufficient, the "overload shedding" function is activated. This "overload shedding" function operates in two directions: forward overload shedding, which follows the same logic as conventional backup power source switching, removing some secondary loads. Reverse overload shedding, however, involves removing a portion of the previously agreed distributed PV lines to prevent the transformer from overloading by reverse power transmission, thus ensuring the safety of grid equipment. Two rounds of overload shedding in each direction minimize the impact on customer electricity consumption and PV power generation.

[0137] The present invention is applicable to the low-voltage side power supply standby automatic switching device of 220 kV, 110 kV and 35 kV substations that are directly connected to customer power loads and photovoltaic power generation, and is also applicable to the power supply standby automatic switching device of 10 kV and 6 kV switch stations that are directly connected to customer power loads and photovoltaic power generation.

[0138] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered by the scope of protection of the claims of the present invention.

Claims

1. A control method for 10kV side standby automatic switching of a substation, characterized in that: The following steps are involved: Step 1: When the incoming line switch of the 1# main transformer or the 2# main transformer is tripped and the current is 0, or the section switch is tripped and the section current is 0, obtain the bus voltage U and perform the standby automatic switching operation; Step 2: If 85% UN≤U<110% UN, execute the synchronization check and automatic switching, and UN is the rated voltage; if the frequency f exceeds the range of 47.5Hz-50.2Hz, go to step 4; In step 3, if 50% UN ≤ U < 85% UN, the appropriate downlink power line is disconnected based on power calculation, and the process continues for 2 seconds until 85% UN ≤ U < 110% UN is satisfied, then the process goes to step 2. If the state of 50% UN ≤ U < 85% UN lasts for more than 2 seconds, all uplink power lines on the corresponding busbars of the 1# and 2# main transformers are disconnected, and the normal no-voltage standby automatic re-transfer operation is performed. In step 4, if U < 50% UN, the appropriate downlink power line is disconnected based on power calculation. This process continues for 0.2 seconds until the conditions of 50% UN ≤ U < 85% UN, 85% UN ≤ U < 110% UN, or 85% UN ≤ U < 110% UN are met step by step. Then, the process goes to step 2. If the U < 50% UN state persists for more than 0.2 seconds, all uplink power lines on the corresponding buses of the 1# and 2# main transformers are disconnected, and the normal no-voltage standby automatic re-transfer logic is executed. In step 5, if 110% UN ≤ U < 135% UN, the appropriate power transmission line is disconnected based on power calculation, and the process continues for 2 seconds until 85% UN ≤ U < 110% UN, then the process goes to step 2. If the state of 110% UN ≤ U < 135% UN lasts for more than 2 seconds, all power transmission lines on the corresponding busbars of the 1# and 2# main transformers are disconnected, and the normal no-voltage standby automatic re-transfer logic is executed. In step 6, if 135% UN≤U, the appropriate power transmission line is cut off after power calculation, and the conditions are gradually met within 0.2s until 110% UN≤U<135%, 85% UN≤U<110%UN, or 85% UN≤U<110%UN is directly met, and then the process goes to step 2. If the 135% UN≤U state lasts for more than 0.2s, all power transmission lines on the corresponding busbars of the 1# and 2# main transformers are cut off, and the normal no-voltage standby automatic re-transfer logic is executed.

2. The control method for 10 kV side standby automatic switching of a substation according to claim 1, characterized in that: The execution of the inspection and preparation for automatic investment includes: Determine whether the high-voltage side voltage of the 1# and 2# main transformers is synchronized with the low-voltage busbar; The synchronization check and standby automatic switching is carried out, and the synchronization check and standby automatic switching is divided into the first standby automatic switching mode, the second standby automatic switching mode, the third standby automatic switching mode and the fourth standby automatic switching mode according to the different main and standby power supplies.

3. The control method for 10 kV side standby automatic switching of a substation according to claim 2, characterized in that: The determination of whether the high-voltage side voltages of the 1# main transformer and the 2# main transformer are synchronized with the low-voltage bus includes: If the high-voltage side voltage of the 1# and 2# main transformers is synchronized with the low-voltage bus, the high-voltage side voltage of the 1# and 2# main transformers is converted into the low-voltage side voltage by the transformation ratio and phase angle, and the voltage amplitudes and phase angles of the two are compared. When the voltage amplitude difference ≤ the amplitude difference setting value and the voltage phase angle difference ≤ the phase angle difference setting value, the synchronization check succeeds and the synchronization closing conditions are met. Otherwise, the synchronization check fails. If the synchronization check delay time t does not meet the synchronization check conditions within the set time, the synchronization check fails; If the sectionalizing switch is automatically switched on and the low-voltage busbars of the 1# main transformer and the 2# main transformer are synchronized, the transformation ratio and phase angle conversion will not be performed.

4. The control method for 10 kV side standby automatic switching of a substation according to claim 3, characterized in that: The first standby automatic switching mode is that the 1# main transformer is the main supply. When the 1# main transformer loses power, the 2# main transformer is automatically switched. The incoming lines of the 1# main transformer or the 2# main transformer are power supply 1 or power supply 2 respectively, and the corresponding switches are 1DL / 1DL-high or 2DL / 2DL-high respectively. The currents of 1DL / 1DL-high and 2DL / 2DL-high are I1 and I2 respectively. The section switch is 3DL, and its current is I3. The high-voltage side voltages of the 1# main transformer and the 2# main transformer are UL1 and UL2 respectively, and the measured low-voltage side bus voltages of the 1# main transformer and the 2# main transformer are U1 and U2 respectively. The specific process of the first automatic standby start-up method is as follows: (1) The charging condition is the same as the conventional standby automatic transfer logic. The discharging condition is different from the conventional standby automatic transfer logic. The detection of no voltage on the high-voltage side of the 2# main transformer UL2 is used as a necessary discharging condition. (2) When charging is completed, if the conditions "1DL / 1DL-high trip, in the open position", "I1 < power supply 1 no-current set value", "UL2 has pressure", and "related soft pressure plate and control word of standby automatic transfer are put into use" are all met, the standby automatic transfer is started; after the delay Tt1, the power supply 1 switch 1DL is tripped. After confirming that 1DL has tripped, after the delay Th2, at the same time 85%UN≤U2<110%UN, the "UL2 and U2 synchronization check" judgment is carried out, and the synchronous closing conditions are met, and the power supply 2 switch is closed; (3) When charging is completed, if 3DL is tripped and there is no current, and the conditions of "UL2 has pressure" and "the related soft pressure plate and control word of the backup automatic transfer are put into operation" are met, the backup automatic transfer is started; after the delay Tt1, the section switch 3DL is tripped; after confirming that 3DL has tripped, all 10kV lines that send power to the low-voltage side bus of the 1# main transformer are cut off to prevent the formation of an island on the low-voltage side bus of the 1# main transformer; after the delay Th2, at the same time, 85%UN≤U2<110%UN is used to judge the "UL2 and U2 synchronization", and the synchronous closing conditions are met, and the power supply 2 switch is closed; (4) When charging is completed, if the backup protection of the 1# main transformer is on and the conditions "I1 < power supply 1 no-current set value" are met, and the conditions "UL2 has pressure" and "the backup automatic switch-on related soft pressure plate and control word are put into operation" are met, the backup automatic switch-on is started; after the delay Tt1, the section switch 3DL is tripped; after confirming that 3DL has tripped, all 10kV lines that send power on the low-voltage side bus of the 1# main transformer are cut off to prevent the formation of an island through the low-voltage side bus of the 1# main transformer; after the delay Th2, at the same time, 85%UN≤U2<110%UN is judged to "check the synchronization of UL2 and U2", and the synchronous closing conditions are met, and the power supply 2 switch is closed.

5. The control method for 10 kV side standby automatic switching of a substation according to claim 4, characterized in that: The second standby automatic transfer mode is that the 2# main transformer is the main supply. When the 2# main transformer loses power, the 1# main transformer is automatically transferred. The specific standby automatic transfer process of the second standby automatic transfer mode is similar to that of the first standby automatic transfer mode.

6. The control method for 10 kV side standby automatic switching of a substation according to claim 4, characterized in that: The third standby automatic switching mode is that the 1# main transformer and the 2# main transformer are respectively the main supply. When the 1# main transformer loses power, the section switch 3DL is automatically switched. The specific standby automatic switching process of the third standby automatic switching mode is as follows: (1) The charging conditions are the same as those of the conventional standby automatic transfer logic. The discharging conditions are different from those of the conventional standby automatic transfer logic, except for the condition that U1 and U2 have no voltage. (2) When charging is completed, if the conditions "1DL / 1DL-high trip, in the open position", "I1 < power supply 1 no-current set value", and "spare automatic start-up related soft pressure plate and control word input" are all met, the spare automatic start-up is started; After the delay Tt1, the power supply 1 switch 1DL is tripped. After confirming that 1DL has tripped, after the delay Th3, and at the same time 85%UN≤U2<110%UN, the "U2 and U1 synchronization check" judgment is performed, and the synchronous closing conditions are met, and the section switch is closed.

7. The control method for 10 kV side standby automatic switching of a substation according to claim 6, characterized in that: The fourth standby automatic switching mode is that 1# main transformer and 2# main transformer are respectively the main supply, and when 2# main transformer loses power, the section switch 3DL is automatically switched; the specific standby automatic switching process of the fourth standby automatic switching mode is similar to that of the third standby automatic switching mode.

8. The control method for 10 kV side standby automatic switching of a substation according to claim 6 or 7, characterized in that: After closing the section switch, open it for 3s to start the accelerated protection after the section is automatically switched on.

9. The control method for 10 kV side standby automatic switching of a substation according to claim 8, characterized in that: The acceleration protection includes overcurrent acceleration protection and zero-sequence acceleration protection, wherein the overcurrent acceleration protection can be selected to be locked by re-pressure.

10. The control method for 10 kV side standby automatic switching of a substation according to any one of claims 4 to 7, characterized in that: After the backup power supply is successfully switched on, if the capacity of the automatic switching power supply is insufficient, overload shedding will be performed; The overload shedding includes forward overload shedding and reverse overload shedding.

11. The control method for 10 kV side standby automatic switching of a substation according to any one of claims 1 to 7, characterized in that: The upward power transmission line refers to a line that directs power to the bus, and the downward power transmission line refers to a line that directs power to the line.

12. A 10 kV side standby automatic switching system for a substation, characterized in that: A control method for implementing the 10 kV side standby automatic transfer of a substation as described in any one of claims 1 to 11, comprising a hardware connection framework and software standby automatic transfer action logic; the hardware connection framework comprises a cable transmission network and an optical fiber transmission network; the software standby automatic transfer action logic comprises a functional module of a standby automatic transfer device and, based on five interval conditions of bus voltage U<50%UN, 50%UN≤U<85%UN, 85%UN≤U<110%UN, 110%UN≤U<135%UN and 135%UN≤U and considering the frequency condition 47.5Hz≤f≤50.2Hz under pressure, divides the standby automatic transfer logic into synchronous standby automatic transfer and traditional no-pressure standby transfer logic.

13. The 10 kV side standby automatic switching system of a substation according to claim 12, characterized in that: The cable transmission network is a standby automatic switching device that collects the position status information of the incoming line switches 1DL / 1DL-high, 2DL / 2DL-high and 10 kV section switch 3DL of the 1# main transformer and the 2# main transformer through cable connections, as well as the corresponding currents I1, I2, I3, the 10 kV I bus and II bus voltages, and the high-voltage side voltages UL1 and UL2 of the 1# main transformer and the 2# main transformer; the optical fiber transmission network is a standby automatic switching device that collects the current, voltage or power of each 10 kV outgoing line of the I bus and the II bus through optical fiber connections, and the multi-in-one devices of each outgoing line of the I bus are collected to the optical switch of the I bus, and the multi-in-one devices of each outgoing line of the II bus are collected to the optical switch of the II bus; the optical switches of the I bus and the II bus are each connected to the standby automatic switching device through an optical fiber.

14. The 10 kV side standby automatic switching system of a substation according to claim 12, characterized in that: The functional modules of the standby automatic switching device include a state quantity identification module, a power calculation and direction identification module, a synchronization detection module, a frequency identification module, a standby automatic switching logic judgment and action module, and a segmented acceleration module; The state quantity identification module is used to identify the operating state of the system by accessing the position information of the 1# main transformer, the 2# main transformer incoming line switches 1DL / 1DL-high, 2DL / 2DL-high and the section switch 3DL of the standby automatic transfer device, as well as the current information of the 1# main transformer, the 2# main transformer and the section switch, to prepare for the action logic execution of the four standby automatic transfer modes of power supply standby automatic transfer and section standby automatic transfer; The power calculation and direction identification module is used to calculate the power of each interval by using the current and voltage of each 10 kV outgoing line interval of the backup automatic switching device connected via optical fiber, and to determine whether the corresponding interval is sending power upward or downward based on the power direction; upward power refers to power directed to the bus, and downward power refers to power directed to the line; The synchronization check module is used to detect whether the voltage amplitude and phase angle of the power supply line voltage and the 10 kV bus voltage meet the synchronization closing requirements in the power supply standby automatic switching mode; The frequency identification module is used to determine whether the frequency of the 10 kV bus to be closed meets the frequency requirement, that is, 47.5 Hz ≤ f ≤ 50.2 Hz, after the original power supply switch is disconnected and before the standby automatic switch is closed; The standby automatic switching logic judgment and action module is used to control the standby automatic switching of the 10 kV side of the substation; The post-segment acceleration module is used for overcurrent protection after the segment switch is closed.

15. The 10 kV side standby automatic switching system of a substation according to claim 14, characterized in that: The functional modules of the standby automatic switching device are specifically used for: (1) Condition 1 judgment and its action logic: If it is within the range of 85% UN ≤ U < 110% UN, execute the synchronization check and automatic switching; if it exceeds the range of 47.5Hz-50.2Hz, go to the "Condition 3 judgment and its action logic" process; (2) Condition 2 judgment and its action logic: within the range of 50% UN ≤ U < 85% UN, the appropriate downlink power line is cut off after power calculation, and within 2 seconds, until 85% UN ≤ U < 110% UN is satisfied, then the process of "Condition 1 judgment and its action logic" is entered; if the state of 50% UN ≤ U < 85% UN lasts for more than 2 seconds, all uplink power 10 kV lines on busbars I and II are cut off, and the normal no-voltage standby automatic re-transfer logic is executed; (3) Condition 3 judgment and its action logic: within the range of U < 50% UN, the appropriate downlink power line is cut off after power calculation, and within 0.2s, it is gradually satisfied that 50% UN ≤ U < 85% UN, 85% UN ≤ U < 110% UN, or directly satisfied that 85% UN ≤ U < 110% UN, and then the process of "Condition 1 judgment and its action logic" is transferred; If the U<50%UN state lasts for more than 0.2s, all 10kV power transmission lines on busbars I and II will be disconnected, and the normal no-voltage standby automatic retransmission logic will be executed; (4) Condition 4 judgment and its action logic: within the range of 110% UN≤U<135% UN, the appropriate power transmission line is cut off after power calculation, and within 2 seconds, until 85% UN≤U<110% UN is satisfied, then the process of "Condition 1 judgment and its action logic" is entered; if the state of 110% UN≤U<135% UN lasts for more than 2 seconds, all 10 kV power transmission lines on busbars I and II are cut off, and the normal no-voltage standby automatic re-transfer logic is executed; (5) Judgment of condition 5 and its action logic: within the range of 135% UN≤U, the appropriate power transmission line is cut off after power calculation, and within 0.2s, it is gradually satisfied that 110% UN≤U<135%, 85% UN≤U<110%UN or 85% UN≤U<110%UN is directly satisfied, and then the process of "judgment of condition 1 and its action logic" is entered; if the 135% UN≤U state lasts for more than 0.2s, all the 10kV power transmission lines on busbars I and II are cut off, and the normal no-voltage standby automatic re-transfer logic is executed.

16. The 10 kV side standby automatic switching system of a substation according to claim 15, characterized in that: The process of checking the synchronization and automatic switching of the backup power supply adopts the control method of the 10 kV side backup automatic switching of the substation as described in any one of claims 2 to 7.

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