User-side phase-splitting on-site reactive power compensation device and method based on low-voltage power line high-speed carrier communication

Abstract

The present application relates to the technical field of reactive power compensation, and particularly relates to a user-side phase-divided on-site reactive power compensation device and method based on low-voltage power line high-speed carrier communication, which comprises: one end of a fuse is connected with a bus inside the device, and the other end is connected with an output end of a capacitor bank for compensation; a voltage and current sampling module is used for collecting bus voltage and current connected with the device, and an output end of the voltage and current sampling module is connected with an input end of a microprocessor to transmit collected voltage and current sampling information to the microprocessor; an output end of the microprocessor is connected with an input end of the capacitor, the microprocessor controls capacitor code combination and switching of the intelligent capacitor to realize automatic control of reactive power compensation; and a communication module communicates with a remote fusion terminal and other reactive power compensation devices. The seventeen-zone map of the present application considers relatively special shock zones and buffer zones, and different control strategies are set in the zones from those in other zones, so that the service life of related equipment is relatively improved.

Description

Technical Field

[0001] This invention relates to the field of reactive power compensation technology, specifically to a user-side phase-by-phase local reactive power compensation device and method based on high-speed carrier communication of low-voltage power lines. Background Technology

[0002] With the development of power systems, power quality has an increasingly significant impact on grid users. Power factor is a crucial indicator for measuring power quality in power systems, and reactive power compensation is often necessary to improve it. Reactive power compensation technology not only maintains grid voltage at a normal level, thereby reducing system losses, but also ensures the safe and stable operation of the power system. Currently, reactive power compensation in power distribution areas is typically performed on the power source side. Users with a capacity of less than 200 kilowatts generally do not install reactive power compensation devices. Therefore, when such users exist in a distribution area, reactive power compensation only at the transformer side is insufficient to meet line loss standards. For these users, on-site reactive power compensation at the user side is urgently needed to reduce line losses.

[0003] Currently, reactive power compensation on the user side is often achieved by installing three-phase fixed / dynamic switching capacitors. This method has the following drawbacks: 1. It lacks intelligent dynamic response capabilities and cannot automatically adjust the line loss power of the distribution lines based on external environmental factors. This results in a relatively fixed and singular reactive power compensation analysis method for low-voltage distribution networks, failing to effectively monitor the reactive power compensation needs of the low-voltage distribution network and further hindering the achievement of dynamic, efficient, and intelligent reactive power compensation effects. 2. It cannot precisely adjust for single-phase reactive power demand, thus failing to solve the problem of three-phase load imbalance. Over time, this will shorten the lifespan of power equipment and cause greater losses. Traditional reactive power compensation methods have a significant impact on the line loss indicators of the distribution area, making it difficult to meet assessment requirements.

[0004] The nine-zone reactive power compensation diagram is a strategy for integrated voltage and reactive power control in substations. The diagram divides the voltage-reactive power plane into nine zones based on the upper and lower limits of voltage and reactive power. The control strategy of the nine-zone diagram involves taking different adjustment measures according to the current operating zone, with the goal of adjusting the operating point to zone 0 (normal operating zone). The advantages of the nine-zone diagram method are its simplicity, ease of implementation, and applicability to various operating scenarios.

[0005] For example, Chinese invention patent CN117691692A discloses a method for optimizing the reactive power and voltage control of a regional power grid that takes into account the consumption of new energy sources. This method ensures that voltage and reactive power do not exceed limits by using tap changers to step up and down and by switching reactive power compensation devices. The steps of this method include: 1) collecting real-time voltage and reactive power data of the low-voltage distribution network; 2) obtaining a nine-zone map of the low-voltage distribution network; 3) obtaining a capacitor switching configuration table; 4) comparing the collected real-time voltage and reactive power data with the upper / lower limits of voltage and reactive power in the nine-zone map to determine the coordinates of the current system operating point in the nine-zone map; 5) matching the coordinates of the operating point with the area identifiers in the capacitor switching configuration table to determine the corresponding switching control method and execute it. However, this method still has some shortcomings, such as not considering the coupling relationship between voltage and reactive power regulation, which may lead to oscillation and frequent device operation. Moreover, the method provided by this patent needs to be used when uniform reactive power compensation is measured in transformers, which is not suitable for reactive power compensation for distributed users. Therefore, it is necessary to invent a reactive power compensation method that is more in line with the actual load conditions.

[0006] In addition, current user-side reactive power compensators have many communication problems, such as:

[0007] 1. Traditional communication methods have low speeds, often only at the kbps level, which cannot meet the requirements of power equipment for transmitting large amounts of data.

[0008] 2. Traditional communication standards do not take into account the complexity of power system environments, the presence of interference, and the long communication distances, and therefore cannot be fully applied to complex power system environments.

[0009] 3. In traditional communication methods, reactive power compensation devices on each user side are often independent, and multiple reactive power compensation devices and the fusion terminal adopt a star topology. Although this topology is simple, information exchange between reactive power compensation devices must go through the fusion terminal, and communication delays will result in insufficient dynamic response capabilities.

[0010] In conclusion, it is essential to use a communication method that is suitable for the domestic power system environment and can improve the interconnection capability between reactive power compensation devices. Summary of the Invention

[0011] Purpose of the invention: This invention provides a user-side phase-by-phase local reactive power compensation device based on high-speed carrier communication of low-voltage power lines, which solves the problem that traditional reactive power compensation devices lack dynamic response and are prone to overcompensation leading to increased line losses. At the same time, this invention also discloses a user-side phase-by-phase local reactive power compensation method based on high-speed carrier communication of low-voltage power lines.

[0012] Technical solution: In a first aspect, the present invention provides a user-side phase-by-phase local reactive power compensation device based on low-voltage power line high-speed carrier communication. The device includes: a microprocessor, a voltage and current sampling module, a capacitor, a communication module, and a fuse.

[0013] One end of the fuse is connected to the internal busbar of the device, and the other end is connected to the output terminal of the compensation capacitor bank.

[0014] The voltage and current sampling module is used to collect the bus voltage and current connected to the device. The output terminal of the voltage and current sampling module is connected to the input terminal of the microprocessor and transmits the collected voltage and current sampling information to the microprocessor.

[0015] The microprocessor is used to acquire the sampled voltage and sampled current output by the voltage and current sampling module, and obtain the phase current I of each phase. A ,I B ,I C and the phase voltage U of each phase A U B U C Phase angle Power factor PF A PF B PF C Thus, the reactive power Q of each of the three phases can be calculated. A Q B Q C The microprocessor is also used to acquire the operating status of the capacitor, including the capacitor encoding status, real-time output of reactive power, remaining capacity, temperature, and operating voltage, and to control the operating mode of the smart capacitor according to the operating status.

[0016] The output terminal of the microprocessor is connected to the input terminal of the capacitor. The microprocessor controls the capacitor encoding combination and switching of the smart capacitor to realize automatic control of reactive power compensation.

[0017] The capacitor is connected to the internal busbar of the device. The capacitor includes multiple groups, which can simultaneously compensate for the three phases, or compensate for one or two phases individually.

[0018] The communication module is used to communicate with remote fusion terminals and other reactive power compensation devices.

[0019] On the other hand, the present invention also provides a user-side phase-by-phase local reactive power compensation method based on low-voltage power line high-speed carrier communication. This method is applied in the aforementioned compensation device and specifically includes:

[0020] The capacitor switching method is initially determined using the constructed seventeen-zone reactive power compensation diagram. The construction process of the seventeen-zone reactive power compensation diagram includes:

[0021] Establish a coordinate system with reactive power as the horizontal axis and phase voltage as the vertical axis, and set the lower limit of reactive power Q. min upper limit of reactive power Q max Phase voltage upper limit U max Phase voltage lower limit U min By setting the boundaries respectively, a nine-zone diagram of reactive power compensation is obtained;

[0022] Based on the aforementioned nine-zone diagram, and according to the lower limit of reactive power Q min upper limit of reactive power Q max Phase voltage upper limit U max Phase voltage lower limit U min The minimum step size ΔQ of reactive power input to the capacitor and the minimum step size ΔU of reactive power compensation voltage are used to obtain the upper limit buffer boundary U of the phase voltage. max +ΔU, Phase voltage lower limit buffer boundary U min -ΔU, reactive power upper limit buffer boundary Q max +ΔQ and reactive power lower limit buffer boundary Q min -ΔQ, combining the above boundary with the nine-zone diagram, yields a thirteen-zone diagram with a buffer for reactive power compensation;

[0023] Based on the lower limit of reactive power Q min upper limit of reactive power Q max Phase voltage upper limit U max Phase voltage lower limit U min The minimum step size ΔQ for reactive power input to the capacitor and the minimum step size ΔU for reactive power compensation voltage are used to obtain the critical lower limit Q of reactive power. min +ΔQ, Critical Upper Limit of Reactive Power Q max -ΔQ, critical lower limit of phase voltage U min +ΔU and critical upper limit of phase voltage U max -ΔU, which is used as a new boundary and combined with the thirteen-zone map to obtain the seventeen-zone map;

[0024] Based on the seventeen-zone diagram, the operating status of each zone and the control strategy for the capacitors are obtained, thereby obtaining the operating mode of each phase and the required reactive power.

[0025] Furthermore, including:

[0026] The seventeen-zone map specifically includes:

[0027] Zone 0: Featured region:

[0028] Zone 1: Featured Region:

[0029] Zone 2: Featured Area:

[0030] Zone 3: Featured Area:

[0031] Zone 4: Featured Areas: And remove the parts that overlap with zone 10;

[0032] Zone 5: Featured Areas:

[0033] Zone 6: Featured Areas:

[0034] Zone 7: Featured Areas:

[0035] Zone 8: Featured Areas: And remove the parts that overlap with area 12;

[0036] Zone 9: Featured Areas:

[0037] Zone 10: Featured region;

[0038] Area 11: Characteristic Regions:

[0039] Zone 12: Featured Areas:

[0040] Zone 13: Featured Areas:

[0041] Zone 14: Featured Areas:

[0042] Zone 15: Featured Areas:

[0043] 16th District: Featured Areas:

[0044] Furthermore, including:

[0045] The thirteen-zone diagram with buffer zone is based on the traditional nine-zone diagram for reactive power compensation, combined with: U = U max +ΔU、U=U min -ΔU、Q=Q min -ΔQ and Q=Q max The result obtained from +ΔQ includes:

[0046] The buffer zone is because in the actual system, the reactive power Q and voltage U change in real time with the load. The system state will move back and forth near the boundary of the nine-zone diagram, forming an oscillation zone where reactive power compensation cannot be performed immediately. The corresponding buffer zones in the seventeen-zone diagram are zones 9, 10, 11, and 12.

[0047] Furthermore, including:

[0048] The process of obtaining the operating status of each region and the control strategy of the capacitor based on the seventeen-region diagram, thereby obtaining the operating mode of each phase and the required reactive power, specifically includes:

[0049] Define the real-time low-voltage distribution area voltage as U, the real-time reactive power as Q, and the system rated voltage as U. n The current system time is t, the reactive power compensation device collects the system status at time t0, the line reactance is X, and Q is defined when the capacitor is switched on. 补 Q < 0, when the capacitor is switched 补 >0, thus the following operating states and control strategies are obtained based on the relationship between voltage and reactive power changes: switching strategy and the magnitude of reactive power Q to be switched. 补 for:

[0050] Zone 0: Operating status: Phase voltage normal, reactive power normal; Control strategy: No action.

[0051] Q 补 =0;

[0052] Zone 1: Operating status: Phase voltage exceeds upper limit; reactive power is within normal range; Control strategy: Disconnect capacitors;

[0053]

[0054] Zone 2: Operating status: Phase voltage exceeds the upper limit, reactive power exceeds the upper limit; Control strategy: No action.

[0055] Q 补 =0;

[0056] Zone 3: Operating status: Phase voltage normal, reactive power exceeds upper limit; Control strategy: Activate capacitors.

[0057] Q 补 =Q max -Q;

[0058] Zone 4: Operating status: The lower the phase voltage, the higher the reactive power; Control strategy: Connect capacitors.

[0059]

[0060] Zone 5: Operating Status: Phase voltage is below the lower limit, indicating normal power; Control Strategy: Activate capacitors.

[0061]

[0062] Zone 6: Operating status: Phase voltage below the lower limit, reactive power exceeding the lower limit; Control strategy: No action.

[0063] Q 补 =0;

[0064] Zone 7: Operating status: Phase voltage normal, reactive power exceeds lower limit; Control strategy: Disconnect capacitors.

[0065] Q 补 =Q min -Q;

[0066] Zone 8: Operating status: Phase voltage increases towards the upper limit, reactive power decreases towards the lower limit; Control strategy: Disconnect capacitors.

[0067]

[0068] Zone 9: Operating status; Phase voltage exceeds the upper limit, but does not exceed the phase voltage upper limit buffer boundary; reactive power is normal. Control strategy: No operation is performed within the buffer time ΔT; if the zone remains open after ΔT, the capacitor is disconnected.

[0069]

[0070] Zone 10: Operating status; phase voltage is normal, reactive power exceeds the upper limit, but does not exceed the reactive power upper limit buffer boundary; control strategy: no operation is performed within the buffer time ΔT; if the zone remains open after ΔT, the capacitor is switched on.

[0071]

[0072] Zone 11: Operating status; phase voltage is below the lower limit, but not exceeding the phase voltage lower limit buffer boundary, and reactive power is normal. Control strategy: No operation is performed within the buffer time ΔT. If the zone remains open after ΔT, the capacitor is switched on.

[0073]

[0074] Zone 12: Operating status; phase voltage is normal, reactive power is below the lower limit, but has not exceeded the reactive power lower limit buffer boundary. Control strategy: No operation is performed within the buffer time ΔT; if the zone remains after ΔT, the capacitor is disconnected.

[0075]

[0076] Zones 13, 14, 15, and 16: The system is in the oscillation zone; no reactive power compensation operation will be performed.

[0077] Q 补 =0.

[0078] Furthermore, the method also includes:

[0079] The phase compensation 27-zone diagram is determined based on the amount of reactive power required for each phase and the capacitor switching method; thus, the reactive power compensation control strategy of the entire three-phase system is determined based on the phase compensation 27-zone diagram.

[0080] Based on the reactive power compensation control strategy and the requirement of prioritizing the power factor of the phase with the larger result calculated by the decision priority model, the final reactive power compensation strategy is obtained, and the switching interval of the capacitor during reactive power compensation is set. The reactive power compensation strategy includes: the switching action of each phase, the size of the switching capacitor, and the switching interval.

[0081] Based on the final reactive power compensation strategy, a capacitor switching command is issued to the smart capacitor.

[0082] Furthermore, including:

[0083] The determination of the 27-zone phase compensation diagram based on the required reactive power of each phase and the capacitor switching method includes:

[0084] Based on the concept of reactive power compensation, a three-dimensional rectangular coordinate system xyz is established. The three coordinate axes xyz represent the reactive power compensation required for the three phases of the line, respectively. Points in the coordinate system (Q...) A补 Q B补 Q C补 () represents the amount of reactive power that needs to be added or removed in the corresponding control strategy of each phase in the seventeen-zone diagram, based on point (Q) A补 Q B补 Q C补 The regions enclosed by the three coordinate axes are named from smallest to largest as follows: Zone 0 to Zone 26.

[0085] Furthermore, including:

[0086] The reactive power compensation strategy for the entire three-phase system determined based on the 27-zone phase compensation diagram includes:

[0087] Zone 0: No capacitor switching is required for any of the three phases;

[0088] Zones 1-3: The capacitor is cut off in one phase, and the other two phases are not operated;

[0089] Zones 4 to 6: One phase is connected to a capacitor, and the other two phases are not operated.

[0090] Zones 7-9: Two phases have their capacitors removed, and the remaining phase is not operated.

[0091] Zones 10-12: Two phases are connected to capacitors, and the remaining phase is not operated;

[0092] Zones 13 to 18: One phase has a capacitor connected, one phase has a capacitor disconnected, and the remaining phase is not operated.

[0093] Zones 19-21: Two phases have their capacitors disconnected, and the remaining phase has its capacitor connected.

[0094] Zones 22-24: Two phases have capacitors connected, and the remaining phase has its capacitor disconnected;

[0095] Zone 25: Capacitors are removed from all three phases;

[0096] Zone 26: All three phases are connected to capacitors;

[0097] Expressed using constraint equations:

[0098]

[0099]

[0100] Furthermore, including:

[0101] The step of calculating the capacitor switching interval during reactive power compensation, based on the reactive power compensation control strategy and the power factor requirement of the largest phase calculated by the priority decision-making model, yields the final reactive power compensation strategy, including:

[0102] For a three-phase unbalanced system, the formula for calculating the total power factor is:

[0103] Define the total power factor of the system PF 总 Q n Taking the partial derivative yields In the formula, S 总 The total apparent power of the system,

[0104] As can be seen from the above formula, the greater the change in reactive power, the higher the power factor improvement. Therefore, the phase with the largest current reactive power will have a higher priority for reactive power compensation than other phases.

[0105] Define the n-phase power factor as PF. n PF n With Q n The relationship is Calculate PF 总 For PF n The gradient is obtained It can be inferred that prioritizing compensation for phases with low power factor and high active power will maximize the improvement in the overall system power factor. Furthermore, it can be concluded that the higher the active power of a phase, the greater the improvement in power factor for the same power factor.n For PF 总 The impact is more significant.

[0106] Therefore, it can be seen that both the active and reactive power of each phase affect the effectiveness of reactive power compensation. The decision priority model for the n-phase is defined as Γ. n =αP n +β|Q n Let α and β be the influence weights of active and reactive power in reactive power compensation, respectively, and α + β = 1. As previously deduced, the magnitude of reactive power in a single-phase compensation phase does not affect the rate of increase in the system power factor, while the larger the active power in that phase, the faster the power factor increases. Therefore, a weight of α = 0.6 and β = 0.4 is used here for priority determination.

[0107] Therefore, the three-phase compensation should be based on the decision priority model Γ. n To perform reactive power compensation sequentially, priority should be given to increasing Γ. n The power factor of the larger phase. Therefore, it should be prioritized according to the priority model Γ. n Capacitor switching is performed from largest to smallest, prioritizing the satisfaction of Γ. n The reactive power demand of the larger phase. Similarly, if the residual reactive power of two phases needs to be used, Γ should be used first. n The smaller phase has less residual reactive power, so that the power factor can be improved as much as possible.

[0108] If the remaining capacity of the reactive power compensation device is insufficient to meet the reactive power compensation demand of a certain phase, and it is necessary to draw remaining reactive power from the other two phases that are not in operation, then Γ should be used first. n The residual reactive power of a smaller phase is used to ensure that its impact on the system power factor is minimized. The residual reactive power refers to the following: for a phase in zone 0 of the reactive power compensation diagram, removing this amount of reactive power will cause the phase's state to just fail to meet the voltage or reactive power requirements; that is, the system state will be at the boundary of zone 0 after removing the residual reactive power. If the phase's state remains in zone 0 after removing all the reactive power currently in operation for that phase, then the removable reactive power for that phase is the amount of reactive power currently in operation for that phase.

[0109] Specifically:

[0110] Zone 0: No reactive power compensation will be provided;

[0111] Zones 1-3: Assuming phase A requires capacitor disconnection, the remaining two phases remain inactive; according to Q... A补 If the removable capacitance cannot meet Q, then... A补 If all capacitors connected to phase A are disconnected, phases B and C will not operate.

[0112] Zones 4-6: Assume phase A requires capacitor input, the remaining two phases do not operate, and Γ B >ΓC First, satisfy Q. A补 If the remaining capacity used by the reactive power compensation device cannot meet Q A补 Then, the remaining reactive power in phases C and B will be deactivated sequentially, thus satisfying Q. A补 ;

[0113] Zones 7-9: Capacitors in phases A and B are removed, according to Q. A补 Q B补 Remove the capacitors in phases A and B respectively. If the removable capacitance cannot meet Q... A补 Or Q B补 If so, all connected capacitors in phase A or phase B will be disconnected; phase C will not operate.

[0114] Zones 10-12: Assume phases A and B require capacitors and Γ A >Γ B Prioritize meeting the reactive power demand of phase A (Q). A补 Then, the reactive power demand Q of phase B is satisfied. B补 If the remaining capacity available to the reactive power compensation device during this process cannot meet the demand, then the remaining reactive power of phase C will be withdrawn, so as to make the phase requiring compensation meet the power factor requirements as much as possible.

[0115] Zones 13-18: Assuming phase A needs to disconnect the capacitor, phase B needs to connect the capacitor, and phase C does not operate; priority is given to Q. A补 If the removable capacitance cannot meet Q, then... A补 Then, disconnect all capacitors connected to phase A, and then add the disconnected capacitors back to the remaining capacity; subsequently, connect capacitors to phase B, trying to satisfy Q as much as possible. B补 If the available remaining capacity of the reactive power compensation device cannot meet Q... B补 If phase demand is required, the remaining reactive power of phase C will be added to the calculation, and phase B compensation will continue.

[0116] Zones 19-21: Assume phases A and B have their capacitors removed, and phase C has its capacitor connected; remove the capacitors from phases A and B respectively to satisfy Q. A补 Q B补 If the resectable volume cannot meet Q A补 Or Q B补 If all connected capacitors in the corresponding phase are disconnected, the disconnected capacitors are added to the remaining capacity for reactive power compensation in phase C, first satisfying Q. C补 ;

[0117] Zones 22-24: Assume capacitors are connected to phases A and B and Γ A >Γ B Phase C capacitor cut-off; priority given to Q C补 If the removable capacitance cannot meet Q, then... C补Then, all connected capacitors in phase C are disconnected, and the disconnected capacitors are added back to the remaining capacity; subsequently, the reactive power demand Q of phase A is prioritized. A补 Connect the capacitor to meet the reactive power demand Q of phase B. B补 Investment;

[0118] Zone 25: Capacitors are removed from all three phases;

[0119] Zone 26: Assumption of three-phase capacitors Γ A >Γ B >Γ C Reactive power compensation is performed sequentially in the order of A, B, and C.

[0120] Furthermore, including:

[0121] The switching interval Δt is set to In the formula, t s The amount of reactive power Q required for a one-time input 补 The oscillation time of the subsequent system, N is the Q provided by the reactive power compensation device. 补 The number of capacitor banks required, and the amount of reactive power Q required for the one-time connection. 补 Set the capacitor capacity to the minimum step size.

[0122] Beneficial effects: Compared with the prior art, the present invention has the following advantages:

[0123] First, based on the existing nine-zone diagram, the present invention constructs a thirteen-zone diagram and a seventeen-zone diagram. The seventeen-zone diagram of the present invention considers the relatively special oscillation zone and buffer zone, and sets a different control strategy than other zones in this zone, thereby reducing the operating frequency of the reactive power compensation device and relatively improving the life of related equipment.

[0124] Secondly, based on the constructed seventeen-zone diagram, this invention sets corresponding control strategies for each zone, including the amount of reactive power that needs to be compensated, thereby ensuring the stability of each zone and effectively achieving real-time balance of reactive power, ensuring that the overall system voltage is maintained at a normal level. The reactive power that needs to be compensated calculated here is for the overall three-phase strategy.

[0125] Finally, to achieve the most accurate compensation possible, this invention proposes constructing a 27-zone diagram. This 27-zone diagram is based on the overall compensation amount of the three phases, calculating the compensation component for each phase. During the three-phase compensation process, to ensure a high power factor and minimize the impact on the power factor, a system total power factor and decision priority model are constructed, and the three-phase compensation is based on the decision priority model Γ. n To perform reactive power compensation sequentially, priority should be given to increasing Γ. n The power factor of the large phase. Therefore, it should be prioritized according to the priority model Γ. nCapacitor switching is performed from largest to smallest, prioritizing the satisfaction of Γ. n The reactive power demand of the larger phase. Similarly, if the residual reactive power of two phases needs to be used, Γ should be used first. n The smaller phase's residual reactive power is used to ensure the power factor is maximized. If the residual capacity of the reactive power compensation device is insufficient to meet the reactive power compensation needs of a particular phase, and it is necessary to draw residual reactive power from the other two phases that are not in operation, then Γ should be used first. n The residual reactive power of the smallest phase is minimized to ensure that its impact on the system power factor is as small as possible;

[0126] Therefore, based on the above description, this application responds to the operation of the three phases separately for the compensation components of the three phases. Adhering to the principle of maximizing the power factor while minimizing the impact on the power factor, it compensates each phase as accurately as possible, thereby avoiding overcompensation or undercompensation. This not only improves the power factor but also avoids frequent switching of capacitors. At the same time, this invention improves the dynamic response capability of the system by using a network of multiple devices, ensuring system stability and greatly reducing economic losses. Attached Figure Description

[0127] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0128] Figure 1 This is a schematic diagram of the internal structure of the user-side phase-by-phase local reactive power compensation device based on low-voltage power line high-speed carrier communication proposed in this invention.

[0129] Figure 2 This is a schematic diagram of the system connection of the user-side phase-by-phase local reactive power compensation device based on low-voltage power line high-speed carrier communication proposed in this invention.

[0130] Figure 3 This is a diagram of reactive power compensation in seventeen zones corresponding to the user-side phase-by-phase local reactive power compensation method based on low-voltage power line high-speed carrier communication proposed in this invention.

[0131] Figure 4 This is a schematic diagram showing the locations of zones 12, 15, 18, and 9 in the phase-by-phase local reactive power compensation method for user-side high-speed power line carrier communication proposed in this invention.

[0132] Figure 5This is a schematic diagram showing the locations of zones 16, 7, 10, and 13 in the phase-by-phase local reactive power compensation method for user-side high-speed power line carrier communication proposed in this invention.

[0133] Figure 6 The present invention proposes a user-side phase-by-phase local reactive power compensation method based on low-voltage power line high-speed carrier communication, which includes schematic diagrams of zones 14, 8, 11, and 17 in the 27-zone diagram.

[0134] Figure 7 This is a schematic diagram of the phase compensation 27-zone structure of the user-side phase-by-phase local reactive power compensation method based on low-voltage power line high-speed carrier communication proposed in this invention.

[0135] Figure 8 This is a simplified equivalent circuit diagram of the reactive power compensation method for user-side phase-by-phase local reactive power compensation based on low-voltage power line high-speed carrier communication proposed in this invention.

[0136] Figure 9 This is a flowchart of the user-side phase-by-phase local reactive power compensation method based on low-voltage power line high-speed carrier communication proposed in this invention. Detailed Implementation

[0137] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0138] like Figure 1 As shown, the present invention provides a user-side phase-by-phase local reactive power compensation device based on low-voltage power line high-speed carrier communication. The device includes: a microprocessor, a voltage and current sampling module, a capacitor, a communication module, and a fuse.

[0139] One end of the fuse is connected to the internal busbar of the device, and the other end is connected to the output terminal of the compensation capacitor bank.

[0140] The voltage and current sampling module is used to collect the bus voltage and current connected to the device. The output terminal of the voltage and current sampling module is connected to the input terminal of the microprocessor and transmits the collected voltage and current sampling information to the microprocessor.

[0141] The microprocessor is used to acquire the sampled voltage and sampled current output by the voltage and current sampling module, and obtain the phase current I of each phase. A ,I B ,I C and the phase voltage U of each phaseA U B U C Phase angle Power factor PF A PF B PF C Therefore, the reactive power Q of each of the three phases can be calculated. A Q B Q C The microprocessor is also used to acquire the operating status of the capacitor, including the capacitor encoding status, real-time output of reactive power, remaining capacity, temperature, and operating voltage, and to control the operating mode of the smart capacitor according to the operating status.

[0142] The output terminal of the microprocessor is connected to the input terminal of the capacitor. The microprocessor controls the capacitor encoding combination and switching of the smart capacitor to realize automatic control of reactive power compensation.

[0143] The capacitor is connected to the internal busbar of the device. The capacitor includes multiple groups, which can simultaneously compensate for the three phases, or compensate for one or two phases individually.

[0144] In this embodiment, as Figure 2 As shown, the intelligent low-voltage high-capacity capacitor is connected to the internal busbar of the reactive power compensation device. The intelligent low-voltage high-capacity capacitor contains six capacitor groups with capacities of 16KVar, 16KVar, 16KVar, 8KVar, 4KVar, and 2KVar respectively. These capacitors can be freely encoded and combined to output a maximum reactive power of 62Kvar. The reactive power output step size of the intelligent capacitor is 2KVar, allowing for simultaneous reactive power compensation for all three phases, compensation for a single phase or two phases, or simultaneous and individual compensation. Furthermore, the number of capacitor groups and the capacity of the intelligent low-voltage high-capacity capacitor can be replaced or expanded according to actual needs, achieving a site-specific effect.

[0145] The communication module is used to communicate with remote fusion terminals and other reactive power compensation devices.

[0146] Specifically, in this embodiment, the low-voltage power line high-speed carrier communication module is used to communicate with the remote fusion terminal and other reactive power compensation devices in the communication area. Multiple reactive power compensation devices form a network with the remote fusion terminal, transmitting the operating status of the smart capacitor, the operating status of the reactive power compensation device's microprocessor, and bus information to the remote fusion terminal at a transmission speed of up to 2Mbps. When a reactive power compensation device malfunctions or cannot meet the current reactive power compensation demand, capacitors can be promptly dispatched from other reactive power compensation devices to meet the demand. Furthermore, when it is necessary to expand the user's reactive power compensation device capacity, a device with a capacity matching the deficit can be directly connected in parallel at the same location. The old device and the new device form a master-slave relationship through low-voltage power line high-speed carrier communication. This method can reduce expansion costs, and using a master-slave mode can avoid two devices detecting low power factors simultaneously, leading to overcompensation, and then simultaneously disconnecting capacitors, causing repeated system oscillations. This communication method improves information transmission rate, enhances system stability, and improves the dynamic capability of reactive power compensation.

[0147] On the other hand, such as Figure 9 As shown, this invention also provides a user-side phase-by-phase local reactive power compensation method based on low-voltage power line high-speed carrier communication. This method is applied in the aforementioned compensation device to control the reactive power output of the reactive power compensation device to achieve reactive power compensation. Specifically, it includes the following steps:

[0148] Step 1: Use the constructed reactive power compensation seventeen-zone diagram to make a preliminary judgment on the capacitor switching method.

[0149] In this embodiment, the construction process of the reactive power compensation seventeen-zone diagram includes:

[0150] First, establish a coordinate system with reactive power as the horizontal axis and phase voltage as the vertical axis, and set the lower limit of reactive power Q. min upper limit of reactive power Q max Phase voltage upper limit U max Phase voltage lower limit U min The traditional nine-zone reactive power compensation diagram is obtained by setting the boundaries for each zone. Based on the nine-zone diagram, the upper limit buffer boundary U of the phase voltage is obtained according to the minimum voltage step size ΔU for minimum compensation under reactive power. max +ΔU, Phase voltage lower limit buffer boundary U min -ΔU, reactive power upper limit buffer boundary Q max +ΔQ and reactive power lower limit buffer boundary Q min -ΔQ, combined with the original nine-zone diagram, yields a thirteen-zone diagram with a buffer for reactive power compensation.

[0151] The thirteen-zone map specifically includes:

[0152] Zone 0: Featured region:

[0153] Zone 1: Featured Region:

[0154] Zone 2: Featured Area:

[0155] Zone 3: Featured Area:

[0156] Zone 4: Featured Areas: And remove the parts that overlap with zone 10;

[0157] Zone 5: Featured Areas:

[0158] Zone 6: Featured Areas:

[0159] Zone 7: Featured Areas:

[0160] Zone 8: Featured Areas: And remove the parts that overlap with area 12;

[0161] Zone 9: Featured Areas:

[0162] Zone 10: Featured region;

[0163] Area 11: Characteristic Regions:

[0164] Zone 12: Featured Areas:

[0165] like Figure 3 As shown, based on the above thirteen-zone diagram, this embodiment constructs a seventeen-zone diagram. The principle of construction is: the minimum step size of the reactive power input by the reactive power compensation capacitor is ΔQ, and the power loss formula can be used to calculate... The minimum voltage step size ΔU corresponding to the minimum reactive power compensation is obtained.

[0166] Based on the lower limit of reactive power Q min upper limit of reactive power Q max Phase voltage upper limit U max Phase voltage lower limit U min The minimum step size ΔQ for reactive power input to the capacitor and the minimum step size ΔU for reactive power compensation voltage are used to obtain the critical lower limit Q of reactive power. min +ΔQ, Critical Upper Limit of Reactive Power Q max -ΔQ, critical lower limit of phase voltage U min +ΔU and critical upper limit of phase voltage U max-ΔU, the new boundary is combined with the original 13-zone map to obtain new 13, 14, 15 and 16 zones, thus forming a 17-zone map.

[0167] That is, the seventeen-zone diagram in this embodiment is obtained by considering the minimum step size ΔQ of the reactive power input to the capacitor and the minimum step size ΔU of the voltage for minimum reactive power compensation based on the thirteen-zone diagram. Specifically:

[0168] Zone 13: Featured Areas:

[0169] Zone 14: Featured Areas:

[0170] Zone 15: Featured Areas:

[0171] 16th District: Featured Areas:

[0172] Step S2: Obtain the operating status of each region and the control strategy for the capacitor based on the seventeen-zone diagram, thereby obtaining the operating mode of each phase and the required reactive power.

[0173] When the system reactive power Q is greater than 0, according to the voltage loss formula:

[0174] In this equation, R represents the line resistance, and X represents the line reactance, the values ​​of which are determined by the transmission line parameters. According to the equation, when the system reactive power is greater than zero, reducing the system reactive power will increase the system voltage; that is, when the system reactive power is greater than 0, adding capacitors to the system will increase the voltage. Similarly, when the system reactive power Q is less than 0, removing capacitors will cause the system voltage to decrease. Ultimately, the relationship between system reactive power and system voltage can be derived: a decrease in reactive power leads to a rise in voltage, and a rise in reactive power leads to a fall in voltage; that is, adding capacitors will increase the system voltage, and removing them will decrease the system voltage.

[0175] Before describing the above steps in detail, it is necessary to confirm that, in this embodiment, the formula for calculating the total compensation capacitor capacity required by the reactive power compensation method is as follows:

[0176] Q 补 =P[tan(cos -1 PF)-tan(cos -1 PF target )], where PF target The target power factor.

[0177] Define the real-time low-voltage distribution area voltage as U, the real-time reactive power as Q, and the system rated voltage as U. nThe current system time is t, the reactive power compensation device collects the system status at time t0, the line reactance is X, and Q is defined when the capacitor is switched on. 补 <0, Q when switching capacitors 补 >0, thus the following operating state and control strategy are obtained based on the relationship between voltage and reactive power changes: switching strategy and the magnitude of reactive power Q that needs to be switched. 补 for:

[0178] Zone 0: Operating status: Phase voltage normal, reactive power normal; Control strategy: No action.

[0179] Q 补 =0.

[0180] Zone 1: Operating status: Phase voltage exceeds upper limit; reactive power is within normal range; Control strategy: Disconnect capacitors;

[0181]

[0182] Zone 2: Operating status: Phase voltage exceeds the upper limit, reactive power exceeds the upper limit; Control strategy: No action.

[0183] Q 补 =0;

[0184] Zone 3: Operating status: Phase voltage normal, reactive power exceeds upper limit; Control strategy: Activate capacitors.

[0185] Q 补 =Q max -Q;

[0186] Zone 4: Operating status: The lower the phase voltage, the higher the reactive power; Control strategy: Connect capacitors.

[0187]

[0188] Zone 5: Operating Status: Phase voltage is below the lower limit, indicating normal power; Control Strategy: Activate capacitors.

[0189]

[0190] Zone 6: Operating status: Phase voltage below the lower limit, reactive power exceeding the lower limit; Control strategy: No action.

[0191] Q 补 =0;

[0192] Zone 7: Operating status: Phase voltage normal, reactive power exceeds lower limit; Control strategy: Disconnect capacitors.

[0193] Q 补 =Q min -Q;

[0194] Zone 8: Operating status: Phase voltage increases towards the upper limit, reactive power decreases towards the lower limit; Control strategy: Disconnect capacitors.

[0195]

[0196] Zone 9: Operating status; phase voltage exceeds the upper limit, but does not exceed the phase voltage upper limit buffer boundary, reactive power is normal. Control strategy: No operation is performed within the buffer time ΔT; if the zone remains open after ΔT, the capacitor is disconnected.

[0197]

[0198] Zone 10: Operating status; phase voltage is normal, reactive power exceeds the upper limit, but does not exceed the reactive power upper limit buffer boundary. Control strategy: No operation is performed within the buffer time ΔT; if the zone remains open after ΔT, the capacitor is switched on.

[0199]

[0200] Zone 11: Operating status; phase voltage is below the lower limit, but not exceeding the phase voltage lower limit buffer boundary, and reactive power is normal. Control strategy: No operation is performed within the buffer time ΔT. If the zone remains open after ΔT, the capacitor is switched on.

[0201]

[0202] Zone 12: Operating status; phase voltage is normal, reactive power is below the lower limit, but has not exceeded the reactive power lower limit buffer boundary. Control strategy: No operation is performed within the buffer time ΔT; if the zone remains after ΔT, the capacitor is disconnected.

[0203]

[0204] Zones 13, 14, 15, and 16: The system is in the oscillation zone; no reactive power compensation operation will be performed.

[0205] Q 补 =0.

[0206] As mentioned above, traditional partition boundaries are clear straight lines. However, in actual systems, reactive power Q and voltage U change in real time with load variations, and the system state may fluctuate around these boundaries. In this case, if reactive power compensation is implemented every time the system state crosses the boundary and enters a region requiring compensation, the reactive power compensation device will frequently switch on and off, potentially causing the system state to oscillate around the boundaries. Therefore, when the system state is in these regions, reactive power compensation is not performed immediately. Instead, a buffer time ΔT is waited, and if the system remains within the same buffer zone, reactive power compensation is then performed. These regions are thus named oscillation buffer zones, corresponding to zones 9, 10, 11, and 12 in the seventeen-zone diagram.

[0207] As mentioned above, voltage and reactive power changes have minimum step sizes ΔU and ΔQ. Based on the relationship between voltage and reactive power changes, it can be deduced that when the system is in zones 13, 14, 15, or 16, switching capacitors with minimum step sizes will cause the system to enter another zone requiring compensation. Furthermore, the capacitor switching strategy in the new zone is opposite to that of the original zone, or no capacitor switching operation is performed in that zone. That is, the system will still be in a state requiring reactive power compensation. Performing reactive power compensation on systems in these zones would cause the control algorithm to repeatedly switch capacitors, resulting in system oscillations and reduced equipment lifespan. Therefore, when the system is in zones 13, 14, 15, or 16, no reactive power compensation operation will be performed, and the corresponding Q... 补 All are 0.

[0208] The specific locations of the seventeenth zone diagram in this embodiment include:

[0209] Zone 0: Featured region:

[0210] Zone 1: Featured Region:

[0211] Zone 2: Featured Area:

[0212] Zone 3: Featured Area:

[0213] Zone 4: Featured Areas: And remove the parts that overlap with zone 10;

[0214] Zone 5: Featured Areas:

[0215] Zone 6: Featured Areas:

[0216] Zone 7: Featured Areas:

[0217] Zone 8: Featured Areas: And remove the parts that overlap with area 12;

[0218] Zone 9: Featured Areas:

[0219] Zone 10: Featured region;

[0220] Area 11: Characteristic Regions:

[0221] Zone 12: Featured Areas:

[0222] Zone 13: Featured Areas:

[0223] Zone 14: Featured Areas:

[0224] Zone 15: Featured Areas:

[0225] 16th District: Featured Areas:

[0226] Step S3: Determine the phase compensation 27-zone diagram based on the reactive power required for each phase and the capacitor switching method.

[0227] In this embodiment, residual reactive power Q is introduced. An Q Bn Q Cn The term "residual reactive power" refers to the following: For a phase in zone 0 of the reactive power compensation zone 17 diagram, removing this amount of reactive power would cause the phase's state to just fall short of the voltage or reactive power requirements, meaning the system state exceeds the range of zone 0. If the phase's state remains in zone 0 after removing all the reactive power currently in operation for that phase, then the removable reactive power for that phase is equal to the amount of reactive power currently in operation for that phase.

[0228] The boundary of region 0 is represented on the seventeen-region map as follows:

[0229] U = U max U = U min (Q mim <Q<Q max ), Q = Q max Q = Q min (U min <U<U max The four line segments represented by ) indicate that when the remaining capacitance of the reactive power compensation capacitor in this device is insufficient to meet the reactive power input of this phase, the remaining reactive power of other phases can be used to meet the reactive power compensation requirements of this phase.

[0230] Based on the concept of reactive power compensation, a three-dimensional rectangular coordinate system xyz is established. The three coordinate axes xyz represent the reactive power compensation required for the three phases of the line, respectively. Points in the coordinate system (Q...) A补 Q B补 Q C补 The numbers () represent the amount of reactive power that needs to be added or removed in the corresponding control strategy for each phase in the 17-zone diagram. Since the space is divided by the ABC axes, it can be considered as being divided into "8 zones, 12 surfaces, 6 lines, and 1 point". These zones are named from smallest to largest as: Zone 0 to Zone 26, such as... Figure 4 , Figure 5 , Figure 6 , Figure 7As shown in the diagram, this diagram is named the Phase-by-Phase Compensation 27-Zone Diagram. The Phase-by-Phase Compensation 27-Zone Diagram visually illustrates the reactive power required for each phase. Depending on the region of the system, it clearly indicates the reactive power compensation method required for the entire three-phase circuit.

[0231] Therefore, in this embodiment, the reactive power compensation strategy for the entire three-phase system is determined based on the 27-zone phase compensation diagram, including:

[0232] Zone 0: No capacitor switching is required for any of the three phases;

[0233] Zones 1-3: The capacitor is cut off in one phase, and the other two phases are not operated;

[0234] Zones 4 to 6: One phase is connected to a capacitor, and the other two phases are not operated.

[0235] Zones 7-9: Two phases have their capacitors removed, and the remaining phase is not operated.

[0236] Zones 10-12: Two phases are connected to capacitors, and the remaining phase is not operated;

[0237] Zones 13 to 18: One phase has a capacitor connected, one phase has a capacitor disconnected, and the remaining phase is not operated.

[0238] Zones 19-21: Two phases have their capacitors disconnected, and the remaining phase has its capacitor connected.

[0239] Zones 22-24: Two phases have capacitors connected, and the remaining phase has its capacitor disconnected;

[0240] Zone 25: Capacitors are removed from all three phases;

[0241] Zone 26: All three phases are connected to capacitors;

[0242] Expressed using constraint equations:

[0243]

[0244]

[0245] Step S4: Determine the reactive power compensation control strategy for the entire three-phase system based on the phase compensation 27-zone diagram;

[0246] Step S5: Based on the reactive power compensation control strategy and the requirement to prioritize improving the power factor of the phase with the largest active power, calculate the switching interval of the capacitor during reactive power compensation to obtain the final reactive power compensation strategy. The reactive power compensation strategy includes: the switching action of each phase, the size of the switching capacitor, and the switching interval.

[0247] In this embodiment, for a three-phase unbalanced system, the total power factor of the system is defined. PF总 Q n Taking the partial derivative yields In the formula S 总 The total apparent power of the system, It can be seen that the greater the change in reactive power, the higher the power factor improvement. Therefore, the phase with the largest current reactive power will have a higher priority for reactive power compensation than other phases.

[0248] Define the n-phase power factor as PF. n PF n With Q n The relationship is Calculate PF 总 For PF n The gradient is obtained It can be inferred that prioritizing compensation for phases with low power factor and high active power will maximize the improvement in the overall system power factor. Furthermore, it can be concluded that the higher the active power of a phase, the greater the improvement in power factor for the same power factor. n For PF 总 The impact is more significant.

[0249] Therefore, it can be seen that both the active and reactive power of each phase affect the effectiveness of reactive power compensation. The decision priority model for the n-phase is defined as Γ. n =αP n +β|Q n Let α and β be the influence weights of active and reactive power in reactive power compensation, respectively, and α + β = 1. As previously deduced, the magnitude of reactive power in a single-phase compensation phase does not affect the rate of increase in the system power factor, while the larger the active power in that phase, the faster the power factor increases. Therefore, a weight of α = 0.6 and β = 0.4 is used here for priority determination.

[0250] Therefore, the three-phase compensation should be based on the decision priority model Γ. n To perform reactive power compensation sequentially, priority should be given to increasing Γ. n The power factor of the larger phase. Therefore, it should be prioritized according to the priority model Γ. n Capacitor switching is performed from largest to smallest, prioritizing the satisfaction of Γ. n The reactive power demand of the larger phase. Similarly, if the residual reactive power of two phases needs to be used, Γ should be used first. n The smaller phase has less residual reactive power, so that the power factor can be improved as much as possible.

[0251] If the remaining capacity of the reactive power compensation device is insufficient to meet the reactive power compensation demand of a certain phase, and it is necessary to draw remaining reactive power from the other two phases that are not in operation, then Γ should be used first. nThe residual reactive power of a smaller phase is used to ensure that its impact on the system power factor is minimized. The residual reactive power refers to the following: for a phase in zone 0 of the reactive power compensation diagram, removing this amount of reactive power will cause the phase's state to just fail to meet the voltage or reactive power requirements; that is, the system state will be at the boundary of zone 0 after removing the residual reactive power. If the phase's state remains in zone 0 after removing all the reactive power currently in operation for that phase, then the removable reactive power for that phase is the amount of reactive power currently in operation for that phase.

[0252] Zone 0: No reactive power compensation will be provided;

[0253] Zones 1-3: Assuming phase A requires capacitor disconnection, the remaining two phases remain inactive; according to Q... A补 If the removable capacitance cannot meet Q, then... A补 If all capacitors connected to phase A are disconnected, phases B and C will not operate.

[0254] Zones 4-6: Assume phase A requires capacitor input, the remaining two phases do not operate, and Γ B >Γ C ; satisfy Q as much as possible A补 If the remaining capacity available from the reactive power compensation device cannot meet Q A补 Then, the remaining reactive power in phases C and B will be deactivated sequentially to satisfy Q as much as possible. A补 ;

[0255] Zones 7-9: Capacitors in phases A and B are removed, according to Q. A补 Q B补 Remove the capacitors in phases A and B respectively. If the removable capacitance cannot meet Q... A补 Or Q B补 If so, all connected capacitors in phase A or phase B will be disconnected; phase C will not operate.

[0256] Zones 10-12: Assume phases A and B require capacitors and Γ A >Γ B Prioritize meeting the reactive power demand of phase A (Q). A补 Then, the reactive power demand Q of phase B is satisfied. B补 If the remaining capacity available to the reactive power compensation device during this process cannot meet the demand, then the remaining reactive power of phase C will be withdrawn, so as to make the phase requiring compensation meet the power factor requirements as much as possible.

[0257] Zones 13-18: Assuming phase A needs to disconnect the capacitor, phase B needs to connect the capacitor, and phase C does not operate; priority is given to Q. A补 If the removable capacitance cannot meet Q, then... A补 Then, disconnect all capacitors connected to phase A, and then add the disconnected capacitors back to the remaining capacity; subsequently, connect capacitors to phase B, trying to satisfy Q as much as possible. B补If the available remaining capacity of the reactive power compensation device cannot meet Q... B补 If phase demand is required, the remaining reactive power of phase C will be added to the calculation, and phase B compensation will continue.

[0258] Zones 19-21: Assume phases A and B have their capacitors removed, and phase C has its capacitor connected; remove the capacitors from phases A and B respectively to satisfy Q. A补 Q B补 If the resectable volume cannot meet Q A补 Or Q B补 If all connected capacitors in the corresponding phase are disconnected, the disconnected capacitors are added to the remaining capacity for C-phase reactive power compensation, to satisfy Q as much as possible. C补 ;

[0259] Zones 22-24: Assume capacitors are connected to phases A and B and Γ A >Γ B Phase C capacitor cut-off; priority given to Q C补 If the removable capacitance cannot meet Q, then... C补 Then, all connected capacitors in phase C are disconnected, and the disconnected capacitors are added back to the remaining capacity; subsequently, the reactive power demand Q of phase A is prioritized. A补 Connect the capacitor to meet the reactive power demand Q of phase B. B补 Investment;

[0260] Zone 25: Capacitors are removed from all three phases;

[0261] Zone 26: Assumption of three-phase capacitors Γ A >Γ B >Γ C Reactive power compensation is performed sequentially in the order of A, B, and C.

[0262] In this embodiment, "meeting the power factor requirement as much as possible" means that if the power factor requirement of a phase can be met, reactive power compensation will be performed as needed; if the power factor requirement of a phase cannot be met, capacitors will be disconnected or connected as much as possible.

[0263] The above-mentioned switching interval Δt is set as follows: In the formula, t s The amount of reactive power Q required for a one-time input 补 The oscillation time of the subsequent system, N is the Q provided by the reactive power compensation device. 补 The number of capacitor banks required is determined to improve system stability.

[0264] Furthermore, for ease of analysis, the single-phase circuit implementing reactive power compensation can be simplified as follows: Figure 8 The diagram shows the equivalent circuit containing only resistors, capacitors, inductors, and an AC power source. According to Kirchhoff's voltage law and basic circuit theory, the state equation of the equivalent circuit is: In the state equation, L is the equivalent inductance of the circuit, R is the equivalent resistance of the user load, C is the parallel capacitor used for reactive power compensation, u is the voltage across the load, and U S Let be the equivalent source voltage. This is a second-order differential equation with characteristic roots as follows:

[0265] In the formula, Represents the damping coefficient. Representing the natural frequency, the solution to this equation can be categorized into three cases based on the relationship between α and ω0: overdamped (α > ω0), critically damped (α = ω0), and underdamped (α < ω0). This indicates that when a capacitor is suddenly connected to the circuit, the voltage and current in the circuit will fluctuate after reaching a steady state. This is related to circuit overshoot. Fluctuation time in, The damping ratio of the circuit

[0266] The above relationships show that an excessively large single-phase capacitor input leads to a smaller damping ratio, resulting in increased overshoot and a longer oscillation time. Conversely, a larger damping ratio results in smaller circuit overshoot and a shorter oscillation time. Therefore, reducing the size of the single-phase capacitor input can reduce system voltage and current fluctuations. For this invention, the reactive power provided by the minimum single-phase capacitor input is fixed. Therefore, to reduce the system voltage and current oscillation time, this invention sets the single-phase reactive power input size as the capacitor capacity with the minimum step size.

[0267] Step S6: Issue capacitor switching commands to the smart capacitors according to the final reactive power compensation strategy.

[0268] Furthermore, during the operation of the reactive power compensation device in this embodiment, a low-voltage power line high-speed carrier communication module is used for communication to transmit real-time data to a remote fusion terminal. If there are multiple reactive power compensation devices described in this invention in the same area, multiple reactive power compensation devices can form a network. When a reactive power compensation device cannot meet the reactive power compensation needs of its users, reactive power capacity can be scheduled from other idle devices for compensation.

[0269] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0270] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0271] Obviously, those skilled in the art can make various modifications and variations to the embodiments of the present invention without departing from the spirit and scope of the embodiments of the present invention. Thus, if these modifications and variations to the embodiments of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention also intends to include these modifications and variations.

Claims

1. A user-side phase-by-phase local reactive power compensation method based on low-voltage power line high-speed carrier communication, characterized in that, This method is applied in a compensation device, which includes: a microprocessor, a voltage and current sampling module, a capacitor, a communication module, and a fuse; One end of the fuse is connected to the internal busbar of the device, and the other end is connected to the output terminal of the compensation capacitor bank. The voltage and current sampling module is used to collect the bus voltage and current connected to the device. The output terminal of the voltage and current sampling module is connected to the input terminal of the microprocessor and transmits the collected voltage and current sampling information to the microprocessor. The microprocessor is used to acquire the sampled voltage and sampled current output by the voltage and current sampling module, and obtain the phase current of each phase. and the phase voltage of each phase Phase angle Power factor This allows for the calculation of the reactive power of each of the three phases. The microprocessor is also used to acquire the operating status of the capacitor, including the capacitor encoding status, real-time output of reactive power, remaining capacity, temperature, and operating voltage, and to control the operating mode of the smart capacitor according to the operating status. The output terminal of the microprocessor is connected to the input terminal of the capacitor. The microprocessor controls the capacitor encoding combination and switching of the smart capacitor to realize automatic control of reactive power compensation. The capacitor is connected to the internal busbar of the device. The capacitor includes multiple groups, which can simultaneously compensate for the three phases, or compensate for one or two phases individually. The communication module is used to communicate with remote fusion terminals and other reactive power compensation devices. The compensation method specifically includes: The capacitor switching method is initially determined using the constructed seventeen-zone reactive power compensation diagram. The construction process of the seventeen-zone reactive power compensation diagram includes: Establish a coordinate system with reactive power as the horizontal axis and phase voltage as the vertical axis, and set the lower limit of reactive power. upper limit of reactive power Phase voltage upper limit Phase voltage lower limit By setting the boundaries respectively, a nine-zone diagram of reactive power compensation is obtained; Based on the aforementioned nine-zone diagram and the lower limit of reactive power upper limit of reactive power Phase voltage upper limit Phase voltage lower limit The minimum step size of reactive power input to the capacitor Minimum voltage step size for minimum reactive power compensation Obtain the upper limit buffer boundary of phase voltage Phase voltage lower limit buffer boundary Reactive power upper limit buffer boundary and reactive power lower limit buffer boundary The above boundaries are combined with the nine-zone diagram to obtain a thirteen-zone diagram with a buffer zone for reactive power compensation. Based on the lower limit of reactive power respectively upper limit of reactive power Phase voltage upper limit Phase voltage lower limit The minimum step size of reactive power input to the capacitor Minimum voltage step size for minimum reactive power compensation Obtain the critical lower limit of reactive power Critical upper limit of reactive power Phase voltage critical lower limit Phase voltage critical upper limit This is used as a new boundary and combined with the thirteen-zone map to obtain the seventeen-zone map; Based on the seventeen-zone diagram, the operating status of each zone and the control strategy for the capacitors are obtained, thereby obtaining the operating mode of each phase and the required reactive power.

2. The compensation method according to claim 1, characterized in that, The seventeen-zone map specifically includes the following areas and the corresponding ranges of the feature areas: Zone 0: Feature Area: ; Zone 1 Feature region: Zone 2 Feature region: ; Zone 3 Feature region: ; Zone 4: Featured Areas: And remove the parts that overlap with zone 10; Zone 5: Featured Areas: ; Zone 6: Featured Areas: ; Zone 7: Featured Areas: ; Zone 8: Featured Areas: And remove the parts that overlap with area 12; Zone 9: Featured Areas: ; Zone 10: Featured Areas: ; Area 11: Characteristic Regions: ; Zone 12: Featured Areas: ; Zone 13: Featured Areas: ; Zone 14: Featured Areas: ; Zone 15: Featured Areas: ; 16th District: Featured Areas: .

3. The compensation method according to claim 2, characterized in that, The thirteen-zone reactive power compensation diagram with buffer zone is based on the nine-zone reactive power compensation diagram and combines the following: , , and The results include: The buffer zone is formed because the reactive power Q and voltage U in the actual system change in real time with the load, and the system state will move back and forth near the boundary of the nine-zone diagram, forming an oscillation zone where reactive power compensation cannot be performed immediately. The corresponding buffer zones in the seventeen-zone diagram are zones 9, 10, 11 and 12.

4. The compensation method according to claim 3, characterized in that, The process of obtaining the operating status of each region and the control strategy of the capacitor based on the seventeen-region diagram, thereby obtaining the operating mode of each phase and the required reactive power, specifically includes: Define the real-time low-voltage distribution area voltage as U, the real-time reactive power as Q, and the system rated voltage as... The current system time is t The reactive power compensation device collects the system status at all times. The line reactance is X, and the definition of capacitor connection is as follows: When cutting capacitors Based on the relationship between voltage and reactive power changes, the following operating states and control strategies are derived: switching strategies and the magnitude of reactive power to be switched. for: Zone 0: Operating status: Phase voltage normal, reactive power normal; Control strategy: No action. ; Zone 1: Operating status: Phase voltage exceeds upper limit; reactive power is within normal range; Control strategy: Disconnect capacitors; Zone 2: Operating status: Phase voltage exceeds the upper limit, reactive power exceeds the upper limit; Control strategy: No action; ; Zone 3: Operating status: Phase voltage normal, reactive power exceeds upper limit; Control strategy: Activate capacitors. ; Zone 4: Operating status: The lower the phase voltage, the higher the reactive power; Control strategy: Connect capacitors. ; Zone 5: Operating Status: Phase voltage is below the lower limit, indicating normal power; Control Strategy: Activate capacitors. ; Zone 6: Operating status: Phase voltage below the lower limit, reactive power exceeding the lower limit; Control strategy: No action. ; Zone 7: Operating status: Phase voltage normal, reactive power exceeds lower limit; Control strategy: Disconnect capacitors. ; Zone 8: Operating status: Phase voltage increases towards the upper limit, reactive power decreases towards the lower limit; Control strategy: Disconnect capacitors. ; Zone 9: Operating status; Phase voltage exceeds the upper limit, but does not exceed the phase voltage upper limit buffer boundary; reactive power is normal; control strategy: buffer time. No operation is performed inside, if If the capacitor remains in that area, it should be removed. ; Zone 10: Operating status; phase voltage is normal, reactive power exceeds the upper limit, but does not exceed the reactive power upper limit buffer boundary; control strategy: buffer time. No operation is performed inside, if Afterwards, while still in that area, a capacitor was inserted. Zone 11: Operating status; Phase voltage is below the lower limit, but not exceeding the lower limit buffer boundary; reactive power is normal; Control strategy: Buffer time No operation is performed inside, if The capacitor was then inserted while the area remained in that region. Zone 12: Operating status; Phase voltage is normal, reactive power is below the lower limit, but has not exceeded the reactive power lower limit buffer boundary; Control strategy: Buffer time No operation is performed inside, if If the capacitor remains in the same area, it should be removed. ; Zones 13, 14, 15, and 16: The system is in the oscillation zone; no reactive power compensation operation will be performed. .

5. The compensation method according to claim 1, characterized in that, The method also includes: The phase compensation 27-zone diagram is determined based on the amount of reactive power required for each phase and the capacitor switching method; thus, the reactive power compensation control strategy of the entire three-phase system is determined based on the phase compensation 27-zone diagram. Based on the reactive power compensation control strategy and the requirement of prioritizing the power factor of the phase with the larger result calculated by the decision priority model, the final reactive power compensation strategy is obtained, and the switching interval of the capacitor during reactive power compensation is set. The reactive power compensation strategy includes: the switching action of each phase, the order of switching capacitors, the size of the switching capacitors, and the switching interval. Based on the final reactive power compensation strategy, a capacitor switching command is issued to the smart capacitor.

6. The compensation method according to claim 5, characterized in that, The determination of the 27-zone phase compensation diagram based on the required reactive power of each phase and the capacitor switching method includes: A three-dimensional rectangular coordinate system is established based on the concept of division and complementation. xyz Three coordinate axes xyz These represent the reactive power compensation required for the three phases of the line, and the points in the coordinate system ( ) represents the amount of reactive power that needs to be added or removed in the corresponding control strategy of each phase in the seventeen-zone diagram, based on point ( The regions enclosed by the three coordinate axes are named from smallest to largest as follows: Zone 0 to Zone 26.

7. The compensation method according to claim 6, characterized in that, The reactive power compensation strategy for the entire three-phase system determined based on the 27-zone phase compensation diagram includes: Zone 0: No capacitor switching is required for any of the three phases; Zones 1-3: The capacitor of one phase is cut off, and the other two phases are not operated; Zones 4-6: One phase is connected to a capacitor, and the other two phases are not operated. Zones 7-9: Two phases have their capacitors removed, and the remaining phase is not operated. Zones 10-12: Two phases are connected to capacitors, and the remaining phase is not operated; Zones 13-18: One phase has a capacitor connected, one phase has a capacitor disconnected, and the remaining phase is not operated. Zones 19-21: Two phases have their capacitors disconnected, and the remaining phase has its capacitor connected. Zones 22-24: Two phases have capacitors connected, and the remaining phase has its capacitor disconnected; Zone 25: Capacitors are removed from all three phases; Zone 26: All three phases are connected to capacitors; Expressed using constraint equations: .

8. The compensation method according to claim 7, characterized in that, The final reactive power compensation strategy is obtained by combining the reactive power compensation control strategy with the power factor requirement of the largest phase calculated by the priority decision-making model, including: For a three-phase unbalanced system, the total power factor of the system is defined. , right Taking the partial derivative yields In the formula, The total apparent power of the system, The greater the change in reactive power, the higher the power factor will improve. Therefore, the phase with the largest current reactive power will have a higher priority for reactive power compensation than other phases. Definition of the first Phase power factor , and The relationship is ,calculate right The gradient is obtained This leads to the conclusion that prioritizing compensation for phases with low power factor and high active power maximizes the improvement in the overall system power factor. Furthermore, it is concluded that the higher the active power of a phase, the greater the improvement for the same power factor. right The impact is more significant, among which, ; Therefore, it can be seen that both the active and reactive power at each stage affect the effectiveness of reactive power compensation. (Definition) n The decision priority model for phases is , and These are the influence weights of active power and reactive power in reactive power compensation, respectively. Since the magnitude of reactive power in a single-phase compensation phase does not affect the rate at which the system power factor improves, while the larger the active power in that phase, the faster the power factor improves. Therefore, the three-phase division is supplemented by a decision priority model. To perform reactive power compensation sequentially, priority should be given to improving [the efficiency / performance]. The power factor of the large phase, according to the priority model Capacitor switching is performed from largest to smallest, prioritizing those needs. Similarly, for the large phase's reactive power demand, if the residual reactive power of two phases needs to be used, priority should be given to using it. The smaller phase has less residual reactive power, so as to ensure that the power factor is maximized. If the remaining capacity of the reactive power compensation device is insufficient to meet the reactive power compensation demand of a certain phase, and it is necessary to draw remaining reactive power from the other two phases that are not in operation, priority should be given to using the remaining reactive power from those two phases. The remaining reactive power of a smaller phase refers to the following: For a phase in zone 0 of the reactive power compensation zone 17 diagram, removing this amount of reactive power will cause the phase state to just fail to meet the voltage or reactive power requirements, that is, the system state will be at the boundary of zone 0 after removing the remaining reactive power; if the phase state is still in zone 0 after removing all the reactive power invested in the phase, then the removable reactive power of the phase is the amount of reactive power currently invested in the phase. Specifically: Zone 0: No reactive power compensation will be provided; Zones 1-3: Assuming phase A requires capacitor disconnection, the remaining two phases remain inactive; according to... Disconnect capacitors if the disconnectable capacitance is insufficient. If all capacitors connected to phase A are disconnected, phases B and C will not operate. Zones 4-6: Assume phase A requires capacitor input, the remaining two phases do not operate, and First, satisfy If the remaining capacity used by the reactive power compensation device cannot meet the requirements Then, the remaining reactive power in phases C and B will be deactivated sequentially, thus satisfying the requirement. ; Zones 7-9: Capacitors in phases A and B are removed, according to... , Disconnect the capacitors in phases A and B respectively. If the disconnectable capacity is insufficient... or If so, all connected capacitors in phase A or phase B will be disconnected; phase C will not operate. Zones 10-12: Assume phases A and B require capacitors to be connected and Prioritize meeting the reactive power demand of phase A. Then, the reactive power requirements of phase B are met. If the remaining capacity available to the reactive power compensation device during this process cannot meet the demand, then the remaining reactive power of phase C will be withdrawn, so as to make the phase requiring compensation meet the power factor requirements as much as possible. Zones 13-18: Assuming phase A needs to disconnect the capacitor, phase B needs to connect the capacitor, and phase C does not operate; priority is given to... If the resectable volume cannot meet the requirements Then, all capacitors connected to phase A are disconnected, and the disconnected capacitors are added back to the remaining capacity; subsequently, capacitors are connected to phase B, as much as possible to meet the requirements. If the remaining capacity available for the reactive power compensation device is insufficient... If phase demand is required, the remaining reactive power of phase C will be added to the calculation, and phase B compensation will continue. Zones 19-21: Assume phases A and B have their capacitors removed, and phase C has its capacitor connected; remove the capacitors from phases A and B respectively to meet the following requirements. , If the resectable volume cannot meet the requirements or If all connected capacitors in the corresponding phase are disconnected, the disconnected capacitors are added to the remaining capacity for reactive power compensation in phase C, first satisfying the following conditions: ; Zones 22-24: Assume capacitors are connected in phases A and B and... Phase C capacitor cut-off; priority should be given to... Disconnect capacitors if the disconnectable capacitance is insufficient. Then, all connected capacitors in phase C are disconnected, and the disconnected capacitors are added to the remaining capacity; subsequently, the reactive power demand of phase A is prioritized. Connect the capacitor to meet the reactive power requirements of phase B. Investment; Zone 25: Capacitors are removed from all three phases; Zone 26: Assumption of capacitors connected in all three phases Reactive power compensation is performed sequentially in the order of A, B, and C.

9. The compensation method according to claim 8, characterized in that, The switching interval Set as In the formula, The amount of reactive power required for a one-time input The oscillation time of the subsequent system Provide reactive power compensation devices The number of capacitor banks required, and the amount of reactive power required for the one-time installation. Set the capacitor capacity to the minimum step size.

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