Synchronization detection grid connection method under non-power-cut operation

Abstract

The method comprises the following steps: S1, according to a power supply relation between a generator side and a power grid side, carrying out synchronization detection on a low-voltage transformer area power grid and a power generation vehicle until the low-voltage transformer area power grid and the power generation vehicle meet a quasi-synchronization condition; s2, judging whether the power grid has sudden fault power loss or not, if so, performing independent power supply on the load by the generator car in a non-grid-connected manner, and then performing S3, and if not, performing grid-connected power supply on the load by the low-voltage transformer area power grid and the generator car; s3, judging whether the power grid returns to normal or not, if so, performing grid-connected power supply on the load by the low-voltage transformer area power grid and the generator car, and completing power protection; if not, continuously judging whether the power grid returns to normal or not, and keeping the power generation vehicle to independently supply power to the load in a non-grid-connected manner; according to the invention, the grid-connected and off-grid opportunity is calculated according to the relation between the grid-side power supply and the generator-side power supply, smooth transition of grid connection is ensured, seamless switching is carried out on the power supply of the user when power failure occurs, and the power utilization stability and continuity of the user are ensured.

Description

Technical Field

[0001] The invention relates to the technical field of power grid switching, in particular to a synchronization detection and grid connection method under power outage operation. Background Art

[0002] With the development of economy and society and the improvement of people's living standards, power users have higher and higher requirements for the continuity and reliability of power supply systems. In particular, some major events and important conference venues have more urgent needs for continuous power supply, and are very sensitive to power outages, even short-term power outages. The social impact caused by power outages has long been highly valued by power supply companies. For some planned maintenance, such as low-voltage distribution network for user access, defect handling, equipment inspection, maintenance, accident handling, and upper-level power grid maintenance operations, there are some non-stop fault handling solutions that can minimize the user's power outage experience. However, for some situations such as line tripping caused by unpredictable unplanned accidents, it is still impossible to achieve seamless switching of user power supply, and it is impossible to meet the demands of some special users for 100% non-stop power outage. The existing technology uses a synchronous grid-connected algorithm to realize the parallel operation of the generator and the power grid, and realizes power protection and capacity expansion without power outage or disconnects the power supply of the power grid for maintenance. This technology has the problem that when the generator and the power grid are running in parallel, if the power grid fails, the faulty power grid cannot be quickly cut off, resulting in power protection failure. Summary of the invention

[0003] The present invention solves the problem that the prior art cannot achieve seamless switching of user power supplies and cannot meet the continuity of user power consumption. A method for checking synchronization and connecting to the grid under non-stop power supply operation is proposed. The timing of connecting to and disconnecting from the grid is calculated according to the power supply relationship between the grid side and the generator side to ensure a smooth transition of the grid connection. When a power outage occurs, the user power supply is seamlessly switched to ensure the stability and continuity of user power consumption.

[0004] In order to achieve the above objectives, the following technical solutions are proposed: A method for checking synchronization and connecting to the grid under non-power-off operation comprises the following steps: S1: According to the power supply relationship between the generator side and the grid side, the low-voltage grid and the generator car are synchronized until the low-voltage grid and the generator car meet the quasi-synchronization conditions; S2: Determine whether the grid has a sudden power failure. If so, the generator truck is not connected to the grid to supply power to the load separately, and then proceed to S3. If not, the low-voltage grid and the generator truck are connected to the grid to supply power to the load. S3: Determine whether the power grid has returned to normal. If so, the low-voltage substation power grid and the power generation vehicle are connected to the grid to supply power to the load, and power supply is completed; if not, continue to determine whether the power grid has returned to normal, and keep the power generation vehicle off-grid to supply power to the load separately.

[0005] The present invention mainly comprises the following steps: S1: According to the power supply relationship between the grid side and the generator side, the generator car and the low-voltage grid are synchronized until the generator car and the low-voltage grid meet the quasi-synchronization condition; S2: Perform grid fault detection to determine whether the low-voltage grid has a sudden power failure. If not, the generator car and the low-voltage grid are connected to the grid to supply power to the load. If so, isolate the faulty grid and use the generator car to independently supply power to the load without being connected to the grid, and then proceed to S3. S3: Real-time monitoring of the grid status to determine whether the grid has returned to normal. If not, the generator truck is kept off-grid to supply power to the load and continue to determine whether the grid has returned to normal. The determination process of whether the grid has returned to normal is consistent with the synchronization check process. When the low-voltage grid and the generator truck are in quasi-synchronization, the grid is considered to have returned to normal.

[0006] The present invention can quickly detect whether there is a sudden power failure in the power grid when the power grid is running. When a sudden power failure occurs in the power grid, the user load is seamlessly switched to the power generation vehicle to ensure uninterrupted power supply for the user; after the power grid resumes normal power supply, the grid connection operation can be automatically performed again to restore the initial state. The synchronous short-term grid connection and rapid switching between the power generation vehicle and the power grid are realized, thereby realizing the closed-loop power transfer operation, thereby reducing the safety hazards such as excessive current impact and circuit breaker tripping caused by the grid connection operation of the generator and the power grid. The present invention can be used for ordinary residential users, and can also be used for power protection in important places, such as important international conferences, sports events, exhibitions, etc. Compared with the current general organizational and technical power supply protection (i.e. the organization conducts emergency repairs and handling of possible major hidden dangers and accidents in advance, eliminates various hidden dangers, and improves measures and plans; the technology generally adopts measures such as pre-inspection of power supply and distribution lines and power supply facilities, and modification of dispatch strategies by the power dispatch center, and some power supply equipment needs to be mobilized, such as bypass operation vehicles, mobile box transformers, and mobile emergency power supply vehicles for protection), it can eliminate possible power accidents to the greatest extent, prevent power outages caused by line failures, etc., and enable power outages caused by special circumstances to be restored as soon as possible, thus reducing the power outage time as much as possible and reducing the impact caused by the power outage. To a certain extent, it can meet the user's demand to minimize the power outage time when a power outage occurs.

[0007] Preferably, the process of determining whether a sudden fault and power outage occurs in the power grid includes first determining whether a momentary drop occurs in the voltage data on the power grid side. If so, a sudden fault and power outage occurs in the power grid. If not, the load side current change is collected, and the grid side current change and the generator side current change are collected at the same time to determine whether the grid side current change and the generator side current change are caused by the load side current change. If so, no operation is performed. If not, it is considered that a sudden fault and power outage occurs in the power grid.

[0008] The process of judging whether a sudden fault or power outage occurs in the power grid of the present invention includes: S21, obtaining grid-side voltage data, and determining whether the grid-side voltage data has a transient drop, if so, it is considered that a sudden fault has occurred in the grid, if not, proceeding to S22; S22, collect the load side current change, grid side current change and generator side current change, and judge whether the generator side current change and grid side current change are caused by the load side current change through the load side current change, grid side current change and generator side current change. If not, it is considered that there is a sudden fault and power failure in the grid. If so, no operation is performed.

[0009] Preferably, the method of determining whether a sudden drop in grid-side voltage data occurs specifically comprises the following steps: collecting grid-side voltage data, and if the drop value of the grid-side voltage data reaches a threshold within a set time, it is considered that a sudden drop occurs and there is a sudden power failure in the grid.

[0010] S21 of the present invention specifically includes the following steps: obtaining grid-side voltage data, determining whether the grid-side voltage data drops to a threshold value within time t1, if so, it is considered that a transient drop occurs in the grid-side voltage data, and a sudden power failure occurs in the grid; if not, proceed to S22.

[0011] Preferably, before judging whether the grid-side current variation and the generator-side current variation are caused by the load-side current variation, the method further includes judging whether there is a sudden fault and power failure in the grid according to the current variation trend.

[0012] The present invention is provided with a pre-judgment step before judging whether the generator side current variation and the grid side current variation are caused by the load side current variation, and the pre-judgment step is to judge whether there is a sudden fault power failure in the grid according to the current variation trend. The pre-judgment step of the current variation trend can improve the accuracy of the sudden fault power failure judgment, and at the same time avoid frequent judgments on whether the generator side current variation and the grid side current variation are caused by the load side current variation, thereby improving the operation efficiency.

[0013] Preferably, judging whether there is a sudden fault power outage in the power grid according to the current change trend includes: Determine whether the load side current change reaches the threshold. If not, do not perform any operation. If so, determine whether the generator side current increases. If not, do not perform any operation. If so, determine whether the grid side current increases. If so, determine whether the grid side current and generator side current changes are caused by load changes. If not, there is a sudden fault in the grid and power outage. If so, do not perform any operation.

[0014] Preferably, when the power grid needs maintenance, the power grid maintenance plan is obtained, the power grid and generator voltage signals are sampled, the sampled voltage signals are analyzed, and when the voltage signals meet the quasi-synchronous conditions, an uninterrupted power transfer is performed from the power grid side to the generator vehicle side; after the power grid side completes the maintenance plan, the power grid and generator voltage signals are sampled, the sampled voltage signals are analyzed, and when the voltage signals meet the quasi-synchronous conditions, an uninterrupted power transfer is performed from the generator vehicle side to the power grid side.

[0015] The present invention can realize quasi-synchronous and non-grid-connected synchronous switching between the low-voltage area power grid and the power generation vehicle according to the power grid maintenance plan. When the power grid needs maintenance, first obtain the power grid maintenance plan, then sample the voltage signals of the generator and the power grid, and then compare and analyze the sampled voltage signals. When the voltage signal meets the quasi-synchronous condition, perform non-stop power conversion from the power grid side to the power generation vehicle side; after the power grid side completes the maintenance plan, sample the voltage signals of the generator and the power grid, and analyze the sampled voltage signals again. When the voltage signal meets the quasi-synchronous condition, perform non-stop power conversion from the power generation vehicle side to the power grid side.

[0016] The present invention can basically handle the faults without power outages in some planned maintenance, which can minimize the power outage experience of users, but it cannot guarantee the continuity of users 100%. The equipment or scheme that can achieve 100% power supply guarantee can calmly deal with planned and unplanned power outage accidents. When a power outage occurs, the user's power supply is seamlessly switched to ensure the continuity of the user's power supply. Therefore, the present invention has two types: maintenance mode (off-grid operation mode) and power protection mode (grid-connected operation mode). The power generation vehicle can be operated off-grid or grid-connected; the off-grid operation mode is mainly for planned power outages, meeting the quasi-synchronous and non-grid-connected synchronous switching of the low-voltage power grid and the power generation vehicle, and making the device widely used in various low-voltage distribution and transformation areas for seamless connection and power supply guarantee; the grid-connected operation mode is mainly for unplanned abnormal power outages that may occur in important power consumption occasions. During normal operation, the power generation vehicle is connected to the grid for operation. When the power grid fails, the user load is seamlessly switched to the power generation vehicle to ensure the uninterrupted power supply of the user; after the power grid resumes normal power supply, the grid-connected operation can be automatically performed again to restore the initial state.

[0017] Preferably, the power supply relationship between the grid side and the generator side includes: power supply phase sequence between the grid side and the generator side, power supply frequency between the grid side and the generator side, voltage deviation between the grid side and the generator side, and power supply phase difference between the grid side and the generator side.

[0018] The power supply relationship between the generator side and the grid side of the present invention includes the power supply phase sequence, power supply frequency, voltage deviation and phase difference between the motor side and the grid side.

[0019] Preferably, the specific steps of the synchronization check are as follows: when the power phase sequence on the grid side and the generator side is consistent and the voltage deviation is less than the voltage deviation percentage and the power frequency deviation is less than the frequency threshold and the power phase difference is 0, it is considered that the low-voltage substation grid and the generator vehicle are in quasi-synchronization.

[0020] The specific steps of the inspection phase of the present invention are as follows: S11, collecting real-time voltage values ​​on the grid side and the generator side; S12, determine whether the power phase sequence of the grid side and the generator side is consistent, if so, proceed to S13, if not, proceed to S16; S13, determine whether the voltage deviation of the grid side and the generator side is less than 5%, if so, proceed to S14, if not, proceed to S16; S14, determine whether the power frequency deviation of the grid side and the generator side is less than 0.1HZ, if so, proceed to S15, if not, proceed to S16; S15, determine whether the power phase difference between the grid side and the generator side is 0, if so, it is considered that the low-voltage grid and the generator vehicle are in quasi-synchronous state, if not, proceed to S16; S16, it is considered that the low-voltage substation power grid and the generator vehicle are not in quasi-synchronous state and do not meet the grid-connected operation conditions.

[0021] Preferably, the voltage deviation percentage is 5%, and the frequency threshold is 0.1 Hz.

[0022] Preferably, the process of judging whether the power grid has returned to normal is consistent with the synchronization checking process, and when the low-voltage substation power grid and the power generation vehicle are in quasi-synchronization, it is considered that the power grid has returned to normal.

[0023] The beneficial effects of the present invention are as follows: the present invention can quickly detect whether there is a sudden power outage in the power grid when the power grid is running. When a sudden power outage occurs in the power grid, the user load is seamlessly switched to the power generation vehicle to ensure uninterrupted power supply to the user; after the power grid resumes normal power supply, the grid-connected operation can be automatically performed again to restore the initial state. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a flow chart of the method of the present invention.

[0025] Figure 2 The present invention is a flow chart for judging power failure caused by sudden fault in power grid.

[0026] Figure 3 It is a flow chart of the inspection process of the present invention.

[0027] Figure 4 It is a planned maintenance flow chart of the present invention. DETAILED DESCRIPTION

[0028] Embodiment 1: This embodiment provides a method for checking synchronization and connecting to the grid under non-stop operation. Figure 1 , including the following steps: S1: According to the power supply relationship between the grid side and the generator side, the generator car and the low-voltage grid are synchronized until the generator car and the low-voltage grid meet the quasi-synchronization condition; S2: Perform grid fault detection to determine whether the low-voltage grid has a sudden power failure. If not, the generator car and the low-voltage grid are connected to the grid to supply power to the load. If so, isolate the faulty grid and use the generator car to independently supply power to the load without being connected to the grid, and then proceed to S3. refer to Figure 2 The process of judging whether a sudden power failure occurs in the power grid of the present invention includes: S21, obtaining grid-side voltage data, and determining whether the grid-side voltage data has a momentary drop, if so, it is considered that the grid has a sudden fault and power outage, if not, proceed to S22; S21 of the present invention specifically includes the following steps: obtaining grid-side voltage data, and determining whether the drop value of the grid-side voltage data within time t1 reaches a threshold, if so, it is considered that the grid-side voltage data has a momentary drop, and the grid has a sudden fault and power outage, if not, proceed to S22.

[0029] S22, collect the load side current change, grid side current change and generator side current change, and judge whether the generator side current change and grid side current change are caused by the load side current change through the load side current change, grid side current change and generator side current change. If not, it is considered that there is a sudden fault and power failure in the grid. If so, no operation is performed.

[0030] S3: Real-time monitoring of the grid status to determine whether the grid has returned to normal. If not, the generator truck is kept off-grid to supply power to the load and continue to determine whether the grid has returned to normal. The determination process of whether the grid has returned to normal is consistent with the synchronization check process. When the low-voltage grid and the generator truck are in quasi-synchronization, the grid is considered to have returned to normal.

[0031] The present invention can quickly detect whether there is a sudden power failure in the power grid when the power grid is running. When a sudden power failure occurs in the power grid, the user load is seamlessly switched to the power generation vehicle to ensure uninterrupted power supply for the user; after the power grid resumes normal power supply, the grid connection operation can be automatically performed again to restore the initial state. The synchronous short-term grid connection and rapid switching between the power generation vehicle and the power grid are realized, thereby realizing the closed-loop power transfer operation, thereby reducing the safety hazards such as excessive current impact and circuit breaker tripping caused by the grid connection operation of the generator and the power grid. The present invention can be used for ordinary residential users, and can also be used for power protection in important places, such as important international conferences, sports events, exhibitions, etc. Compared with the current general organizational and technical power supply protection (i.e. the organization conducts emergency repairs and handling of possible major hidden dangers and accidents in advance, eliminates various hidden dangers, and improves measures and plans; the technology generally adopts measures such as pre-inspection of power supply and distribution lines and power supply facilities, and modification of dispatch strategies by the power dispatch center, and some power supply equipment needs to be mobilized, such as bypass operation vehicles, mobile box transformers, and mobile emergency power supply vehicles for protection), it can eliminate possible power accidents to the greatest extent, prevent power outages caused by line failures, etc., and enable power outages caused by special circumstances to be restored as soon as possible, thus reducing the power outage time as much as possible and reducing the impact caused by the power outage. To a certain extent, it can meet the user's demand to minimize the power outage time when a power outage occurs.

[0032] The present invention can realize quasi-synchronous and non-grid-connected synchronous switching between the low-voltage area power grid and the power generation vehicle according to the power grid maintenance plan. Figure 4 When the power grid needs maintenance, first obtain the power grid maintenance plan, then sample the generator and power grid voltage signals, and then compare and analyze the sampled voltage signals. When the voltage signal meets the quasi-synchronous condition, perform non-stop power transfer from the power grid side to the generator car side. After the maintenance plan is completed on the power grid side, sample the generator and power grid voltage signals, and then analyze the sampled voltage signals. When the voltage signal meets the quasi-synchronous condition, perform non-stop power transfer from the generator car to the power grid side.

[0033] The present invention can basically handle the faults without power outages in some planned maintenance, which can minimize the power outage experience of users, but it cannot guarantee the continuity of users 100%. The equipment or scheme that can achieve 100% power supply guarantee can calmly deal with planned and unplanned power outage accidents. When a power outage occurs, the user's power supply is seamlessly switched to ensure the continuity of the user's power supply. Therefore, the present invention has two types: maintenance mode (off-grid operation mode) and power protection mode (grid-connected operation mode). The power generation vehicle can be operated off-grid or grid-connected; the off-grid operation mode is mainly for planned power outages, meeting the quasi-synchronous and non-grid-connected synchronous switching of the low-voltage power grid and the power generation vehicle, and making the device widely used in various low-voltage distribution and transformation areas for seamless connection and power supply guarantee; the grid-connected operation mode is mainly for unplanned abnormal power outages that may occur in important power consumption occasions. During normal operation, the power generation vehicle is connected to the grid for operation. When the power grid fails, the user load is seamlessly switched to the power generation vehicle to ensure the uninterrupted power supply of the user; after the power grid resumes normal power supply, the grid-connected operation can be automatically performed again to restore the initial state.

[0034] Embodiment 2: This embodiment optimizes S22 on the basis of embodiment 1, and proposes a synchronization detection and grid connection method under non-stop operation. Figure 1 , including the following steps: S1: According to the power supply relationship between the grid side and the generator side, the generator car and the low-voltage grid are synchronized until the generator car and the low-voltage grid meet the quasi-synchronization condition; S2: Perform grid fault detection to determine whether the low-voltage grid has a sudden power failure. If not, the generator car and the low-voltage grid are connected to the grid to supply power to the load. If so, isolate the faulty grid and use the generator car to independently supply power to the load without being connected to the grid, and then proceed to S3. refer to Figure 2 The process of judging whether a sudden power failure occurs in the power grid of the present invention includes: S21, obtaining grid-side voltage data, and determining whether the grid-side voltage data has a momentary drop, if so, it is considered that the grid has a sudden fault and power outage, if not, proceed to S22; S21 of the present invention specifically includes the following steps: obtaining grid-side voltage data, and determining whether the drop value of the grid-side voltage data within time t1 reaches a threshold, if so, it is considered that the grid-side voltage data has a momentary drop, and the grid has a sudden fault and power outage, if not, proceed to S22.

[0035] S22, collect the load side current change, grid side current change and generator side current change, and judge whether the generator side current change and grid side current change are caused by the load side current change through the load side current change, grid side current change and generator side current change. If not, it is considered that there is a sudden fault and power failure in the grid. If so, no operation is performed.

[0036] The present invention is provided with a pre-judgment step before judging whether the generator side current variation and the grid side current variation are caused by the load side current variation, and the pre-judgment step is to judge whether there is a sudden fault power failure in the grid according to the current variation trend. The pre-judgment step of the current variation trend can improve the accuracy of the sudden fault power failure judgment, and at the same time avoid frequent judgments on whether the generator side current variation and the grid side current variation are caused by the load side current variation, thereby improving the operation efficiency.

[0037] refer to Figure 2 The specific steps of judging whether there is a sudden fault power outage in the power grid according to the current change trend of the present invention include: S221, determine whether the load side current change reaches a set threshold, if so, proceed to S222, if not, proceed to S224; S222, judging whether the generator side current has increased according to the change in the generator side current, if so, proceed to S223, if not, proceed to S224; S223, judging whether the grid-side current has increased according to the grid-side current change, and if so, judging whether the generator-side current change and the grid-side current change are caused by the load-side current change, and if not, proceeding to S224; S224, no operation is performed.

[0038] S3: Real-time monitoring of the grid status to determine whether the grid has returned to normal. If not, the generator truck is kept off-grid to supply power to the load and continue to determine whether the grid has returned to normal. The determination process of whether the grid has returned to normal is consistent with the synchronization check process. When the low-voltage grid and the generator truck are in quasi-synchronization, the grid is considered to have returned to normal.

[0039] The present invention can quickly detect whether there is a sudden power failure in the power grid when the power grid is running. When a sudden power failure occurs in the power grid, the user load is seamlessly switched to the power generation vehicle to ensure uninterrupted power supply for the user; after the power grid resumes normal power supply, the grid connection operation can be automatically performed again to restore the initial state. The synchronous short-term grid connection and rapid switching between the power generation vehicle and the power grid are realized, thereby realizing the closed-loop power transfer operation, thereby reducing the safety hazards such as excessive current impact and circuit breaker tripping caused by the grid connection operation of the generator and the power grid. The present invention can be used for ordinary residential users, and can also be used for power protection in important places, such as important international conferences, sports events, exhibitions, etc. Compared with the current general organizational and technical power supply protection (i.e. the organization conducts emergency repairs and handling of possible major hidden dangers and accidents in advance, eliminates various hidden dangers, and improves measures and plans; the technology generally adopts measures such as pre-inspection of power supply and distribution lines and power supply facilities, and modification of dispatch strategies by the power dispatch center, and some power supply equipment needs to be mobilized, such as bypass operation vehicles, mobile box transformers, and mobile emergency power supply vehicles for protection), it can eliminate possible power accidents to the greatest extent, prevent power outages caused by line failures, etc., and enable power outages caused by special circumstances to be restored as soon as possible, thus reducing the power outage time as much as possible and reducing the impact caused by the power outage. To a certain extent, it can meet the user's demand to minimize the power outage time when a power outage occurs.

[0040] The present invention can realize quasi-synchronous and non-grid-connected synchronous switching between the low-voltage area power grid and the power generation vehicle according to the power grid maintenance plan. When the power grid needs maintenance, first obtain the power grid maintenance plan, then sample the voltage signals of the generator and the power grid, and then compare and analyze the sampled voltage signals. When the voltage signal meets the quasi-synchronous condition, perform non-stop power conversion from the power grid side to the power generation vehicle side; after the power grid side completes the maintenance plan, sample the voltage signals of the generator and the power grid, and analyze the sampled voltage signals again. When the voltage signal meets the quasi-synchronous condition, perform non-stop power conversion from the power generation vehicle side to the power grid side.

[0041] The present invention can basically handle the faults without power outages in some planned maintenance, which can minimize the power outage experience of users, but it cannot guarantee the continuity of users 100%. The equipment or scheme that can achieve 100% power supply guarantee can calmly deal with planned and unplanned power outage accidents. When a power outage occurs, the user's power supply is seamlessly switched to ensure the continuity of the user's power supply. Therefore, the present invention has two types: maintenance mode (off-grid operation mode) and power protection mode (grid-connected operation mode). The power generation vehicle can be operated off-grid or grid-connected; the off-grid operation mode is mainly for planned power outages, meeting the quasi-synchronous and non-grid-connected synchronous switching of the low-voltage power grid and the power generation vehicle, and making the device widely used in various low-voltage distribution and transformation areas for seamless connection and power supply guarantee; the grid-connected operation mode is mainly for unplanned abnormal power outages that may occur in important power consumption occasions. During normal operation, the power generation vehicle is connected to the grid for operation. When the power grid fails, the user load is seamlessly switched to the power generation vehicle to ensure the uninterrupted power supply of the user; after the power grid resumes normal power supply, the grid-connected operation can be automatically performed again to restore the initial state.

[0042] Embodiment 3: This embodiment optimizes the synchronization check step based on the embodiment 2, and proposes a synchronization check grid connection method under non-stop operation. Figure 1 , including the following steps: S1: According to the power supply relationship between the grid side and the generator side, the power supply relationship between the generator side and the grid side of the present invention includes the power supply phase sequence, power supply frequency, voltage deviation and phase difference between the motor side and the grid side. Synchronize the generator car with the low-voltage grid until the generator car and the low-voltage grid meet the quasi-synchronization condition; refer to Figure 3 The specific steps of the inspection phase of the present invention are as follows: S11, collecting real-time voltage values ​​on the grid side and the generator side; S12, determine whether the power phase sequence of the grid side and the generator side is consistent, if so, proceed to S13, if not, proceed to S16; S13, determine whether the voltage deviation of the grid side and the generator side is less than 5%, if so, proceed to S14, if not, proceed to S16; S14, determine whether the power frequency deviation of the grid side and the generator side is less than 0.1HZ, if so, proceed to S15, if not, proceed to S16; S15, determine whether the power phase difference between the grid side and the generator side is 0, if so, it is considered that the low-voltage grid and the generator vehicle are in quasi-synchronous state, if not, proceed to S16; S16, it is considered that the low-voltage substation power grid and the generator vehicle are not in quasi-synchronous state and do not meet the grid-connected operation conditions.

[0043] S2: Perform grid fault detection to determine whether the low-voltage grid has a sudden power failure. If not, the generator car and the low-voltage grid are connected to the grid to supply power to the load. If so, isolate the faulty grid and use the generator car to independently supply power to the load without being connected to the grid, and then proceed to S3. refer to Figure 2 The process of judging whether a sudden power failure occurs in the power grid of the present invention includes: S21, obtaining grid-side voltage data, and determining whether the grid-side voltage data has a momentary drop, if so, it is considered that the grid has a sudden fault and power outage, if not, proceed to S22; S21 of the present invention specifically includes the following steps: obtaining grid-side voltage data, and determining whether the drop value of the grid-side voltage data within time t1 reaches a threshold, if so, it is considered that the grid-side voltage data has a momentary drop, and the grid has a sudden fault and power outage, if not, proceed to S22.

[0044] S22, collect the load side current change, grid side current change and generator side current change, and judge whether the generator side current change and grid side current change are caused by the load side current change through the load side current change, grid side current change and generator side current change. If not, it is considered that there is a sudden fault and power failure in the grid. If so, no operation is performed.

[0045] The present invention is provided with a pre-judgment step before judging whether the generator side current variation and the grid side current variation are caused by the load side current variation, and the pre-judgment step is to judge whether there is a sudden fault power failure in the grid according to the current variation trend. The pre-judgment step of the current variation trend can improve the accuracy of the sudden fault power failure judgment, and at the same time avoid frequent judgments on whether the generator side current variation and the grid side current variation are caused by the load side current variation, thereby improving the operation efficiency.

[0046] refer to Figure 2 The specific steps of judging whether there is a sudden fault power outage in the power grid according to the current change trend of the present invention include: S221, determine whether the load side current change reaches a set threshold, if so, proceed to S222, if not, proceed to S224; S222, judging whether the generator side current has increased according to the change in the generator side current, if so, proceed to S223, if not, proceed to S224; S223, judging whether the grid-side current has increased according to the grid-side current change, and if so, judging whether the generator-side current change and the grid-side current change are caused by the load-side current change, and if not, proceeding to S224; S224, no operation is performed.

[0047] S3: Real-time monitoring of the grid status to determine whether the grid has returned to normal. If not, the generator truck is kept off-grid to supply power to the load and continue to determine whether the grid has returned to normal. The determination process of whether the grid has returned to normal is consistent with the synchronization check process. When the low-voltage grid and the generator truck are in quasi-synchronization, the grid is considered to have returned to normal.

[0048] The present invention can quickly detect whether there is a sudden power failure in the power grid when the power grid is running. When a sudden power failure occurs in the power grid, the user load is seamlessly switched to the power generation vehicle to ensure uninterrupted power supply for the user; after the power grid resumes normal power supply, the grid connection operation can be automatically performed again to restore the initial state. The synchronous short-term grid connection and rapid switching between the power generation vehicle and the power grid are realized, thereby realizing the closed-loop power transfer operation, thereby reducing the safety hazards such as excessive current impact and circuit breaker tripping caused by the grid connection operation of the generator and the power grid. The present invention can be used for ordinary residential users, and can also be used for power protection in important places, such as important international conferences, sports events, exhibitions, etc. Compared with the current general organizational and technical power supply protection (i.e. the organization conducts emergency repairs and handling of possible major hidden dangers and accidents in advance, eliminates various hidden dangers, and improves measures and plans; the technology generally adopts measures such as pre-inspection of power supply and distribution lines and power supply facilities, and modification of dispatch strategies by the power dispatch center, and some power supply equipment needs to be mobilized, such as bypass operation vehicles, mobile box transformers, and mobile emergency power supply vehicles for protection), it can eliminate possible power accidents to the greatest extent, prevent power outages caused by line failures, etc., and enable power outages caused by special circumstances to be restored as soon as possible, thus reducing the power outage time as much as possible and reducing the impact caused by the power outage. To a certain extent, it can meet the user's demand to minimize the power outage time when a power outage occurs.

[0049] The present invention can realize quasi-synchronous and non-grid-connected synchronous switching between the low-voltage area power grid and the power generation vehicle according to the power grid maintenance plan. When the power grid needs maintenance, first obtain the power grid maintenance plan, then sample the voltage signals of the generator and the power grid, and then compare and analyze the sampled voltage signals. When the voltage signal meets the quasi-synchronous condition, perform non-stop power conversion from the power grid side to the power generation vehicle side; after the power grid side completes the maintenance plan, sample the voltage signals of the generator and the power grid, and analyze the sampled voltage signals again. When the voltage signal meets the quasi-synchronous condition, perform non-stop power conversion from the power generation vehicle side to the power grid side.

[0050] The present invention can basically handle the faults without power outages in some planned maintenance, which can minimize the power outage experience of users, but it cannot guarantee the continuity of users 100%. The equipment or scheme that can achieve 100% power supply guarantee can calmly deal with planned and unplanned power outage accidents. When a power outage occurs, the user's power supply is seamlessly switched to ensure the continuity of the user's power supply. Therefore, the present invention has two types: maintenance mode (off-grid operation mode) and power protection mode (grid-connected operation mode). The power generation vehicle can be operated off-grid or grid-connected; the off-grid operation mode is mainly for planned power outages, meeting the quasi-synchronous and non-grid-connected synchronous switching of the low-voltage power grid and the power generation vehicle, and making the device widely used in various low-voltage distribution and transformation areas for seamless connection and power supply guarantee; the grid-connected operation mode is mainly for unplanned abnormal power outages that may occur in important power consumption occasions. During normal operation, the power generation vehicle is connected to the grid for operation. When the power grid fails, the user load is seamlessly switched to the power generation vehicle to ensure the uninterrupted power supply of the user; after the power grid resumes normal power supply, the grid-connected operation can be automatically performed again to restore the initial state.

Claims

1. A method for checking synchronization and connecting to the grid without power outage, characterized in that: The following steps are involved: S1: According to the power supply relationship between the generator side and the grid side, the low-voltage grid and the generator car are synchronized until the low-voltage grid and the generator car meet the quasi-synchronization conditions; S2: Determine whether the grid has a sudden power failure. If so, the generator truck is not connected to the grid to supply power to the load separately, and then proceed to S3. If not, the low-voltage grid and the generator truck are connected to the grid to supply power to the load. S3: Determine whether the power grid has returned to normal. If so, the low-voltage substation power grid and the power generation vehicle are connected to the grid to supply power to the load, and power supply is completed; if not, continue to determine whether the power grid has returned to normal, and keep the power generation vehicle off-grid to supply power to the load separately.

2. The method for checking synchronization and connecting to the grid under non-stop operation according to claim 1 is characterized in that: The process of determining whether a sudden fault and power outage occurs in the power grid includes first determining whether a momentary drop occurs in the voltage data on the power grid side. If so, a sudden fault and power outage occurs in the power grid. If not, a load-side current change is collected, and at the same time, the grid-side current change and the generator-side current change are collected to determine whether the grid-side current change and the generator-side current change are caused by the load-side current change. If so, no operation is performed. If not, it is considered that a sudden fault and power outage occurs in the power grid.

3. The method for checking synchronization and connecting to the grid under non-stop operation according to claim 2 is characterized in that: The method of determining whether a sudden drop in grid voltage data occurs specifically includes the following steps: collecting grid voltage data; if the grid voltage data drops by a value that reaches a threshold within a set time, it is considered that a sudden drop has occurred and the grid has a sudden fault and power outage.

4. The method for checking synchronization and connecting to the grid under non-stop operation according to claim 2 is characterized in that: Before determining whether the grid-side current variation and the generator-side current variation are caused by the load-side current variation, the method further includes determining whether there is a sudden fault power failure in the grid according to the current variation trend.

5. The method for checking synchronization and connecting to the grid under non-stop operation according to claim 4 is characterized in that: The method of judging whether there is a sudden fault power outage in the power grid according to the current change trend includes: Determine whether the load side current change reaches the threshold. If not, do not perform any operation. If so, determine whether the generator side current increases. If not, do not perform any operation. If so, determine whether the grid side current increases. If so, determine whether the grid side current and generator side current changes are caused by load changes. If not, there is a sudden fault in the grid and power outage. If so, do not perform any operation.

6. The method for checking synchronization and connecting to the grid under non-stop operation according to claim 1 is characterized in that: When the power grid needs maintenance, the power grid maintenance plan is obtained, the power grid and generator voltage signals are sampled, the sampled voltage signals are analyzed, and when the voltage signals meet the quasi-synchronous conditions, an uninterrupted power transfer is performed from the power grid side to the generator side. After the power grid side completes the maintenance plan, the power grid and generator voltage signals are sampled, the sampled voltage signals are analyzed, and when the voltage signals meet the quasi-synchronous conditions, an uninterrupted power transfer is performed from the generator side to the power grid side.

7. A method for checking synchronization and connecting to the grid under non-stop operation according to any one of claims 1 to 6, characterized in that: The power supply relationship between the grid side and the generator side includes: the power supply phase sequence between the grid side and the generator side, the power supply frequency between the grid side and the generator side, the voltage deviation between the grid side and the generator side, and the power supply phase difference between the grid side and the generator side.

8. The method for checking synchronization and connecting to the grid under non-stop operation according to claim 7 is characterized in that: The specific steps of the synchronization check are as follows: when the power phase sequence on the grid side and the generator side is consistent and the voltage deviation is less than the voltage deviation percentage and the power frequency deviation is less than the frequency threshold and the power phase difference is 0, it is considered that the low-voltage substation grid and the generator car are in quasi-synchronization.

9. The method for checking synchronization and connecting to the grid under non-stop operation according to claim 8 is characterized in that: The voltage deviation percentage is 5%, and the frequency threshold is 0.1 Hz.

10. The method for checking synchronization and connecting to the grid under non-stop operation according to claim 8 is characterized in that: The process of judging whether the power grid has returned to normal is consistent with the synchronization checking process. When the low-voltage substation power grid and the power generation vehicle are in quasi-synchronization, it is considered that the power grid has returned to normal.

Images