A power balancing method and system for multiple parallel lines of a new energy power grid

Abstract

A power balancing method and system for multiple parallel lines of a new energy power grid, comprising: determining whether each line is overloaded; if overloaded, determining whether the overload is caused by voltage, power, or a combined effect; if the overload is caused by voltage, adjusting reactive power; if the overload is caused by power, determining whether the sum of all remaining capacities is greater than the product of the required transfer power of the overloaded line and a set safety margin; if so, setting the target power of the overloaded line to the line thermal stability limit, and allocating the remaining capacity to the overloaded line according to the comprehensive priority; otherwise, setting the target power to the set minimum allowable power, and cutting off the load from low to high according to the importance of the load; if the overload is caused by a combined effect, first reducing the power of the overloaded line to the target power, and if it is still overloaded at this time, adjusting reactive power. The present invention can perform fast, economical, and reliable power balancing after an overload, and is suitable for the operation requirements of modern complex power grids.

Description

Technical Field

[0001] The present invention relates to the technical field of power grid overload balancing, and in particular to a power balancing method and system for multiple parallel lines of a new energy power grid. Background Art

[0002] In recent years, with the development of society and the economy, a large amount of renewable energy has been connected to the power grid in response to the country's sustainable development strategy. However, due to the significant instability of renewable energy sources such as wind power and photovoltaics, the grid has been continuously expanded to improve power supply reliability, and interconnection between nodes has been strengthened. While this change has increased the flexibility of the grid, it has also significantly increased the complexity of power flow regulation. In particular, power flow control on key interconnection lines has become a key challenge facing the grid. With the expansion of the grid, the problem of power flow distribution on multiple parallel lines has become increasingly urgent and requires further optimization. Such optimization not only improves the economic efficiency of the power system but is also crucial for enhancing system operational reliability. If appropriate control measures are not implemented, uneven power flow distribution is likely to occur, resulting in some lines being overloaded or even overloaded, while others may be underloaded or underutilized.

[0003] In this situation, the equipment and protection devices on the heavily loaded lines are subject to higher requirements, while the equipment on the lightly loaded lines is far below its carrying capacity. In extreme cases, this may cause the receiving end to lose all external power supply and the internal system to collapse due to insufficient power. Summary of the Invention

[0004] In order to solve the deficiencies in the prior art, the present invention provides a method and system for balancing power of multiple parallel lines in a new energy power grid.

[0005] The present invention adopts the following technical solutions.

[0006] A first aspect of the present invention provides a method for balancing power of multiple parallel lines in a new energy power grid, characterized by comprising:

[0007] Combined with the fluctuation of renewable energy output, the overload of each line is determined based on the line voltage and active power. If a line overload exists, it is determined whether the overload is caused by voltage, power, or a combination of these factors.

[0008] If the overload is caused by voltage, the reactive power is adjusted until it is not overloaded; if the overload is caused by power, the power required to be transferred of the overloaded line is calculated, and the remaining capacity, impedance and electrical distance of the remaining non-overloaded lines are obtained to calculate the comprehensive priority of the remaining non-overloaded lines; determine whether the sum of all remaining capacities is greater than the product of the power required to be transferred of the overloaded line and the set safety margin. If so, the target power of the overloaded line is set to the thermal stability limit of the line, and the remaining capacity is allocated to the overloaded line according to the comprehensive priority; otherwise, the target power is set to the set minimum allowable power, and the load is cut off from low to high according to the importance of the load; if the overload is caused by a combined effect, the power of the overloaded line is first reduced to the target power according to the steps for overload caused by power. If it is still overloaded at this time, the reactive power is adjusted until it is not overloaded.

[0009] Preferably, considering the fluctuation of renewable energy output, it is determined whether each line is overloaded based on line voltage and active power, specifically:

[0010] The comprehensive overload index is calculated based on the line voltage and active power. The formula is:

[0011]

[0012] Where, is the comprehensive overload index; is the actual line voltage; is the line rated voltage; is the maximum voltage deviation allowed for the line; is the actual active power of the line; is the thermal stability limit of the line; 、 Weights for power and voltage over-limits are set to account for fluctuations in renewable energy output;

[0013] If the comprehensive overload index is greater than 1, the line is judged to be overloaded.

[0014] Preferably, the weights of power over-limit and voltage over-limit set taking into account the fluctuation of renewable energy output are specifically:

[0015]

[0016] Where, is the slope coefficient, Set between 5-10; The output of new energy fluctuates.

[0017] Preferably, the overload is determined to be caused by voltage, power, or a combination of voltage and power, specifically:

[0018] like The absolute value of is greater than or equal to 1, and Less than 1; it is an overload caused by voltage; if The absolute value of is less than 1, and If it is greater than or equal to 1, it is an overload caused by power action; if The absolute value and If both are greater than or equal to 1, it is an overload caused by the combined effect of voltage and power.

[0019] Preferably, the power to be transferred of the overloaded line is calculated, and the remaining capacity, impedance, and electrical distance of the remaining non-overloaded lines are obtained to calculate the comprehensive priority of the remaining non-overloaded lines, specifically:

[0020] The power to be transferred is the actual active power of the overloaded line minus the line thermal stability limit. The remaining capacity of the remaining non-overloaded lines is equal to the line thermal stability limit of the remaining non-overloaded lines minus the actual active power of the lines.

[0021] Calculate the electrical distances between the remaining non-overloaded lines and the overloaded lines. Normalize the remaining capacity, impedance, and electrical distance of the remaining non-overloaded lines. Take the weighted sum of the normalized remaining capacity, 1 minus the normalized impedance, and 1 minus the normalized electrical distance to obtain a comprehensive priority, where the remaining capacity has the largest weight. Sort the lines in descending order of comprehensive priority.

[0022] Preferably, if the proportion of renewable energy output in the power grid exceeds 30%, the safety margin is set to 1.5 times, otherwise it is set to 1.3 times.

[0023] Preferably, the remaining capacity is allocated to the overloaded lines according to the comprehensive priority, specifically:

[0024] Sort the remaining non-overloaded lines according to their comprehensive priority from highest to lowest, and allocate 70% of the remaining capacity of the remaining non-overloaded lines to the overloaded lines according to this sorting, until the actual power of the overloaded lines drops to the target power of the overloaded lines; if the actual power of the overloaded lines still does not reach the target power of the overloaded lines after the remaining non-overloaded lines of all lines have been allocated, then allocate 30% of the current remaining capacity of the remaining non-overloaded lines to the overloaded lines according to this sorting, until the actual power of the overloaded lines drops to the target power of the overloaded lines or the remaining non-overloaded lines have been allocated this time.

[0025] Preferably, after allocating the remaining capacity to the overloaded line according to the comprehensive priority, an N-1 check is performed. The N-1 check simulates whether the remaining lines are overloaded after any one of the set critical lines is disconnected. If there is an overload, the check fails. The loads are sorted from low to high according to their importance, and the first m loads set are removed in sequence according to the sorting until the target power of the overloaded line is reduced. If the target power of the overloaded line is still not reduced after the first m loads are removed, the target power of the overloaded line is set to the set minimum allowable power, and the unremoved loads continue to be removed according to the sorting.

[0026] Preferably, the minimum allowed power is set to 25% of the line thermal stability limit.

[0027] The second aspect of the present invention provides a power balancing system for multiple parallel lines of a new energy power grid using the method described in the first aspect of the present invention, comprising an overload judgment module, a voltage regulation module, a power regulation module, and a voltage and power joint regulation module, characterized in that:

[0028] Overload judgment module: It is used to judge whether each line is overloaded according to the line voltage and active power in combination with the fluctuation of renewable energy output. If there is a line overload, it is determined whether the overload is caused by voltage, power or a combination of the two.

[0029] Voltage regulation module: used to adjust reactive power until overload is eliminated if the overload is caused by voltage action;

[0030] Power regulation module: If the overload is caused by power effects, it calculates the power required to be transferred on the overloaded line and obtains the remaining capacity, impedance, and electrical distance of the remaining non-overloaded lines to calculate the overall priority of the remaining non-overloaded lines. It determines whether the sum of all remaining capacities is greater than the product of the power required to be transferred on the overloaded line and the set safety margin. If so, the target power of the overloaded line is set to the line thermal stability limit, and the remaining capacity is allocated to the overloaded line based on the overall priority. Otherwise, the target power is set to the set minimum allowable power, and loads are removed from low to high importance.

[0031] Voltage and power joint regulation module: if the overload is caused by the joint action, the power of the overloaded line will be reduced to the target power according to the steps of the overload caused by the power action. If it is still overloaded at this time, the reactive power will be adjusted until it is no longer overloaded.

[0032] The beneficial effect of the present invention is that, compared with the prior art, in the overload identification link, the present invention takes into account the processing volatility of new energy, establishes a voltage-active power joint criterion, and distinguishes between voltage over-limit, power over-limit and mixed overload. For overloads caused by power action, the line priority is calculated based on the remaining capacity, impedance characteristics and electrical distance, the flow distribution is optimized, the overload of local lines is avoided from being transferred to other weak links, and a safety margin is set, which not only prevents the waste of resources caused by direct load shedding, but also retains sufficient buffer capacity to avoid the risk of chain overload caused by power transfer. If the remaining capacity is insufficient, the target power is forced to be reduced to the preset minimum allowable power. This mechanism fundamentally eliminates the risk of system collapse caused by forced power transfer, and at the same time strives for response time for subsequent emergency measures such as load shedding. Therefore, the present invention can perform fast, economical and reliable power balancing after overload, and is suitable for the operation requirements of modern complex power grids. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 The present invention is a flowchart of the method. DETAILED DESCRIPTION

[0034] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. The embodiments described in this application are only part of the embodiments of the present invention, not all of them. Based on the spirit of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0035] like Figure 1 As shown, embodiment 1 of the present invention proposes a power balancing method for multiple parallel lines of a new energy power grid, which is characterized by comprising:

[0036] Combined with the fluctuation of renewable energy output, the overload of each line is determined based on the line voltage and active power. If a line overload exists, it is determined whether the overload is caused by voltage, power, or a combination of these factors.

[0037] If the overload is caused by voltage, the reactive power is adjusted until it is not overloaded; if the overload is caused by power, the power required to be transferred of the overloaded line is calculated, and the remaining capacity, impedance and electrical distance of the remaining non-overloaded lines are obtained to calculate the comprehensive priority of the remaining non-overloaded lines; determine whether the sum of all remaining capacities is greater than the product of the power required to be transferred of the overloaded line and the set safety margin. If so, the target power of the overloaded line is set to the thermal stability limit of the line, and the remaining capacity is allocated to the overloaded line according to the comprehensive priority; otherwise, the target power is set to the set minimum allowable power, and the load is cut off from low to high according to the importance of the load; if the overload is caused by a combined effect, the power of the overloaded line is first reduced to the target power according to the steps for overload caused by power. If it is still overloaded at this time, the reactive power is adjusted until it is not overloaded.

[0038] It should be noted that the reactive power regulation in this embodiment is achieved by absorbing / injecting reactive current from the power grid through the parallel transformer (STATCOM) part of the transformerless power router;

[0039] Combined with the fluctuation of renewable energy output, whether each line is overloaded is determined based on line voltage and active power. Specifically:

[0040] The comprehensive overload index is calculated based on the line voltage and active power. The formula is:

[0041]

[0042] Where, is the comprehensive overload index; is the actual line voltage; is the line rated voltage; is the maximum voltage deviation allowed for the line; is the actual active power of the line; is the thermal stability limit of the line; 、 Weights for power and voltage over-limits are set to account for fluctuations in renewable energy output;

[0043] If the comprehensive overload index is greater than 1, the line is judged to be overloaded.

[0044] The weights of power and voltage over-limits set taking into account the fluctuation of renewable energy output are as follows:

[0045]

[0046] Where, is the slope coefficient, Set between 5-10; The output of new energy fluctuates.

[0047] Determine whether the overload is caused by voltage, power, or a combination of voltage and power. Specifically:

[0048] like The absolute value of is greater than or equal to 1, and Less than 1; it is an overload caused by voltage; if The absolute value of is less than 1, and If it is greater than or equal to 1, it is an overload caused by power action; if The absolute value and If both are greater than or equal to 1, it is an overload caused by the combined effect of voltage and power.

[0049] Calculate the power that needs to be transferred on the overloaded line, and obtain the remaining capacity, impedance, and electrical distance of the remaining non-overloaded lines to calculate the comprehensive priority of the remaining non-overloaded lines. Specifically:

[0050] The power to be transferred is the actual active power of the overloaded line minus the line thermal stability limit. The remaining capacity of the remaining non-overloaded lines is equal to the line thermal stability limit of the remaining non-overloaded lines minus the actual active power of the lines.

[0051] Calculate the electrical distances between the remaining non-overloaded lines and the overloaded lines. Normalize the remaining capacity, impedance, and electrical distance of the remaining non-overloaded lines. Take the weighted sum of the normalized remaining capacity, 1 minus the normalized impedance, and 1 minus the normalized electrical distance to obtain a comprehensive priority, where the remaining capacity has the largest weight. Sort the lines in descending order of comprehensive priority.

[0052] If the proportion of renewable energy output in the power grid exceeds 30%, the safety margin is set to 1.5 times, otherwise it is set to 1.3 times.

[0053] Allocate the remaining capacity to overloaded lines based on the comprehensive priority, specifically:

[0054] Sort the remaining non-overloaded lines according to their comprehensive priority from highest to lowest, and allocate 70% of the remaining capacity of the remaining non-overloaded lines to the overloaded lines according to this sorting, until the actual power of the overloaded lines drops to the target power of the overloaded lines; if the actual power of the overloaded lines still does not reach the target power of the overloaded lines after the remaining non-overloaded lines of all lines have been allocated, then allocate 30% of the current remaining capacity of the remaining non-overloaded lines to the overloaded lines according to this sorting, until the actual power of the overloaded lines drops to the target power of the overloaded lines or the remaining non-overloaded lines have been allocated this time.

[0055] It should be noted that the minimum safety margin in this embodiment is set to 1.3 times, that is, the sum of the remaining capacities is at least greater than 1.3 of the power to be transferred from the overloaded line. After the above two rounds of allocation, under ideal conditions, a total of 79% ( ) of the remaining capacity, 79% of the remaining capacity is at least greater than 1.027 ( ) times the power that needs to be transferred of the overloaded line, so ideally, after the above two rounds of distribution, the actual power of the overloaded line can be reduced to the target power of the overloaded line.

[0056] After allocating the remaining capacity to the overloaded line based on the comprehensive priority, an N-1 check is performed. The N-1 check simulates whether the remaining lines are overloaded after any of the set critical lines is disconnected. If there is an overload, the check fails. The loads are sorted from low to high according to their importance. The first m loads set are removed in sequence according to the order until the target power of the overloaded line is reduced. If the target power of the overloaded line is still not reduced to the target power after the first m loads are removed, the target power of the overloaded line is set to the set minimum allowable power, and the unremoved loads continue to be removed according to the order.

[0057] It should be noted that m is set to 3.

[0058] The minimum allowable power is set to 25% of the line thermal stability limit.

[0059] Embodiment 2 of the present invention provides a power balancing system for multiple parallel lines of a new energy power grid using the method described in Embodiment 1 of the present invention, comprising an overload judgment module, a voltage regulation module, a power regulation module, and a voltage and power joint regulation module, characterized in that:

[0060] Overload judgment module: It is used to judge whether each line is overloaded according to the line voltage and active power in combination with the fluctuation of renewable energy output. If there is a line overload, it is determined whether the overload is caused by voltage, power or a combination of the two.

[0061] Voltage regulation module: used to adjust reactive power until overload is eliminated if the overload is caused by voltage action;

[0062] Power regulation module: If the overload is caused by power effects, it calculates the power required to be transferred on the overloaded line and obtains the remaining capacity, impedance, and electrical distance of the remaining non-overloaded lines to calculate the overall priority of the remaining non-overloaded lines. It determines whether the sum of all remaining capacities is greater than the product of the power required to be transferred on the overloaded line and the set safety margin. If so, the target power of the overloaded line is set to the line thermal stability limit, and the remaining capacity is allocated to the overloaded line based on the overall priority. Otherwise, the target power is set to the set minimum allowable power, and loads are removed from low to high importance.

[0063] Voltage and power joint regulation module: if the overload is caused by the joint action, the power of the overloaded line will be reduced to the target power according to the steps of the overload caused by the power action. If it is still overloaded at this time, the reactive power will be adjusted until it is no longer overloaded.

[0064] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than 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 method for balancing power of multiple parallel lines in a new energy power grid, characterized in that: include: Combined with the fluctuation of renewable energy output, the overload of each line is determined based on the line voltage and active power. If a line overload exists, it is determined whether the overload is caused by voltage, power, or a combination of these factors. The comprehensive overload index is calculated based on the line voltage and active power. The formula is: Where, is the comprehensive overload index; is the actual line voltage; is the line rated voltage; is the maximum voltage deviation allowed for the line; is the actual active power of the line; is the thermal stability limit of the line; 、 Weights for power and voltage over-limits are set to account for fluctuations in renewable energy output; If the comprehensive overload index is greater than 1, the line is judged to be overloaded; If the overload is caused by voltage, the reactive power is adjusted until the overload is eliminated. If the overload is caused by power, the power required to be transferred on the overloaded line is calculated, and the remaining capacity, impedance, and electrical distance of the remaining non-overloaded lines are obtained to calculate the comprehensive priority of the remaining non-overloaded lines. A determination is made as to whether the sum of all remaining capacities is greater than the product of the power required to be transferred on the overloaded line and the set safety margin. If so, the target power of the overloaded line is set to the line thermal stability limit, and the remaining capacity is allocated to the overloaded line based on the comprehensive priority. Otherwise, the target power is set to the set minimum allowable power, and the loads are removed from low to high importance. If the overload is caused by a combined effect, the power of the overloaded line is first reduced to the target power according to the steps for overload caused by power effect. If it is still overloaded at this time, the reactive power is adjusted until it is no longer overloaded.

2. The method for balancing power of multiple parallel lines in a new energy power grid according to claim 1, characterized in that: The weights of power and voltage over-limits set taking into account the fluctuation of renewable energy output are as follows: Where, is the slope coefficient, Set between 5-10; The output of new energy fluctuates.

3. The power balancing method for multiple parallel lines of a new energy power grid according to claim 1, characterized in that: Determine whether the overload is caused by voltage, power, or a combination of voltage and power. Specifically: like The absolute value of is greater than or equal to 1, and Less than 1; it is an overload caused by voltage; if The absolute value of is less than 1, and If it is greater than or equal to 1, it is an overload caused by power action; if The absolute value and If both are greater than or equal to 1, it is an overload caused by the combined effect of voltage and power.

4. The method for balancing power of multiple parallel lines in a new energy power grid according to claim 1, characterized in that: Calculate the power that needs to be transferred on the overloaded line, and obtain the remaining capacity, impedance, and electrical distance of the remaining non-overloaded lines to calculate the comprehensive priority of the remaining non-overloaded lines. Specifically: The power to be transferred is the actual active power of the overloaded line minus the line thermal stability limit. The remaining capacity of the remaining non-overloaded lines is equal to the line thermal stability limit of the remaining non-overloaded lines minus the actual active power of the lines. Calculate the electrical distances between the remaining non-overloaded lines and the overloaded lines; normalize the remaining capacity, impedance, and electrical distance of the remaining non-overloaded lines; The comprehensive priority is obtained by taking the weighted sum of the normalized remaining capacity, 1 minus the normalized impedance, and 1 minus the normalized electrical distance, where the remaining capacity has the largest weight. The systems are sorted from largest to smallest according to the comprehensive priority.

5. The method for balancing power of multiple parallel lines in a new energy power grid according to claim 1, characterized in that: If the proportion of renewable energy output in the power grid exceeds 30%, the safety margin is set to 1.5 times, otherwise it is set to 1.3 times.

6. The method for balancing power of multiple parallel lines in a new energy power grid according to claim 5, characterized in that: Allocate the remaining capacity to overloaded lines based on the comprehensive priority, specifically: Sort the remaining non-overloaded lines according to their comprehensive priority from highest to lowest, and allocate 70% of the remaining capacity of the remaining non-overloaded lines to the overloaded lines according to this sorting, until the actual power of the overloaded lines drops to the target power of the overloaded lines; if the actual power of the overloaded lines still does not reach the target power of the overloaded lines after the remaining non-overloaded lines of all lines have been allocated, then allocate 30% of the current remaining capacity of the remaining non-overloaded lines to the overloaded lines according to this sorting, until the actual power of the overloaded lines drops to the target power of the overloaded lines or the remaining non-overloaded lines have been allocated this time.

7. The method for balancing power of multiple parallel lines in a new energy power grid according to claim 6, characterized in that: After allocating the remaining capacity to the overloaded line based on the comprehensive priority, an N-1 check is performed. The N-1 check simulates whether the remaining lines are overloaded after any of the set critical lines is disconnected. If there is an overload, the check fails. The loads are sorted from low to high according to their importance. The first m loads set are removed in sequence according to the order until the target power of the overloaded line is reduced. If the target power of the overloaded line is still not reduced to the target power after the first m loads are removed, the target power of the overloaded line is set to the set minimum allowable power, and the unremoved loads continue to be removed according to the order.

8. A method for balancing power of multiple parallel lines in a new energy power grid according to any one of claims 1 or 7, characterized in that: The minimum allowable power is set to 25% of the line thermal stability limit.

9. A power balancing system for multiple parallel lines of a new energy power grid using the method according to any one of claims 1 to 8, comprising an overload judgment module, a voltage regulation module, a power regulation module, and a voltage and power joint regulation module, characterized in that: Overload judgment module: It is used to judge whether each line is overloaded according to the line voltage and active power in combination with the fluctuation of renewable energy output. If there is a line overload, it is determined whether the overload is caused by voltage, power or a combination of the two. Voltage regulation module: used to adjust reactive power until overload is eliminated if the overload is caused by voltage action; Power regulation module: If the overload is caused by power effects, it calculates the power required to be transferred on the overloaded line and obtains the remaining capacity, impedance, and electrical distance of the remaining non-overloaded lines to calculate the overall priority of the remaining non-overloaded lines. It determines whether the sum of all remaining capacities is greater than the product of the power required to be transferred on the overloaded line and the set safety margin. If so, the target power of the overloaded line is set to the line thermal stability limit, and the remaining capacity is allocated to the overloaded line based on the overall priority. Otherwise, the target power is set to the set minimum allowable power, and loads are removed from low to high importance. Voltage and power joint regulation module: if the overload is caused by the joint action, the power of the overloaded line will be reduced to the target power according to the steps of the overload caused by the power action. If it is still overloaded at this time, the reactive power will be adjusted until it is no longer overloaded.

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