Temporary intelligent power distribution cabinet with layered three-phase balanced hardware for construction site

Abstract

The application discloses a construction site temporary intelligent power distribution cabinet with layered three-phase balance hardware and belongs to the technical field of construction site temporary power distribution and power quality treatment. The power distribution cabinet comprises a construction site mobile protection cabinet body, a total road three-phase acquisition unit, an impact load double-dimensional hardware identification unit, a four-bridge-arm SVG active fast balance branch, a multi-grade inter-phase capacitor passive coarse adjustment branch, a compensation quantity non-disturbance handover control unit and an edge intelligent master control unit. Short-time impact imbalance and continuous imbalance are distinguished through double-threshold comparison, state maintenance and duration determination, short-time impact is compensated by the four-bridge-arm SVG, and the inter-phase capacitor coarse adjustment is enabled after continuous imbalance is confirmed; the SVG output is synchronously adjusted when the inter-phase capacitor branch is put into or withdrawn from, compensation quantity smooth handover is realized, and negative sequence current, zero sequence current and N-line current are adjusted, so that the capacitor frequent switching and compensation fluctuation are reduced, and the balance and operation stability of the temporary power distribution are improved.

Description

Technical Field

[0001] This invention belongs to the field of temporary power distribution and power quality management technology at construction sites. Specifically, it relates to a temporary intelligent power distribution cabinet for construction sites with layered three-phase balancing hardware, and more particularly to a temporary intelligent power distribution cabinet for construction sites using a three-phase four-wire temporary power supply system, which achieves dynamic balancing of three-phase loads through impact load identification, active rapid compensation and passive hierarchical compensation. Background Technology

[0002] Construction sites typically use three-phase four-wire temporary power supply systems to power AC welding machines, vibrating equipment, cutting equipment, hand-held power tools, lighting equipment, and motor-driven construction equipment. Due to the dispersed locations of construction equipment, a high proportion of single-phase loads, and the randomness of start-up and shutdown, uneven distribution of the A, B, and C phases is prone to occur. Especially during welding arc initiation and motor startup, the three-phase current may experience sudden increases or decreases in a short period. Furthermore, when multiple single-phase devices continuously operate on a single phase, a persistent three-phase load imbalance can result. This three-phase load imbalance not only increases the current and line losses in some phases but can also generate significant zero-sequence current and neutral (N) line current in a three-phase four-wire system, causing problems such as N line temperature rise.

[0003] To address the issues of three-phase imbalance and reactive power compensation, existing technologies have proposed technical solutions combining active and passive compensation. For example, patent document CN207625296U discloses a three-phase imbalance adjustment device for electrical loads that combines active and passive compensation, using a capacitor compensation branch and an IGBT active compensation branch to jointly adjust the three-phase imbalance; patent document CN104466990A discloses a dynamic reactive power compensation system combining TSC and SVG, using TSC for graded coarse compensation and SVG for continuous fine compensation; patent document CN102684203A discloses a dynamic reactive power compensation control method using SVG and TSC, prioritizing rapid compensation by SVG during instantaneous load changes and controlling the grouping of TSCs according to load changes. Therefore, the overall technical approach of using a combination of SVG and graded capacitors for dynamic compensation has been applied in existing technologies.

[0004] However, load changes at construction sites exhibit significant random impact characteristics. While both short-term impact imbalances caused by welding machine arc ignition and motor startup, and persistent imbalances resulting from long-term concentrated equipment operation, manifest as increased negative-sequence current imbalance, their durations and suitable compensation methods differ. If capacitor branch switching is controlled solely based on whether a single three-phase imbalance index exceeds a set threshold, short-term impacts can easily cause frequent capacitor branch trips; conversely, simply increasing the switching delay time may cause the SVG (Static Var Generator) to bear a large compensation capacity for an extended period under persistent imbalance conditions. Therefore, existing combined compensation methods still struggle to balance rapid response to short-term impacts with stable compensation for persistent imbalances.

[0005] Furthermore, when the SVG has already output a certain amount of compensation, directly connecting or disconnecting a capacitor bank can easily cause the active and passive compensation amounts to overlap or fall short at the moment of switching, resulting in a step increase in the total compensation amount and secondary fluctuations in the three-phase current. For three-phase four-wire power supply systems, simply using inter-phase capacitors for compensation is insufficient to effectively handle the zero-sequence current and neutral current generated by single-phase unbalanced loads.

[0006] Therefore, existing technologies still need to address the following technical issues: how to jointly determine the amplitude and duration of three-phase imbalance in the context of alternating short-term impact loads and continuous steady-state loads at construction sites, so that short-term impacts are responded to by fast active compensation branches, while continuous imbalances are compensated by passive compensation branches for steady-state compensation; at the same time, a smooth compensation quantity connection relationship should be established between active and passive compensation branches to reduce secondary fluctuations caused by branch switching, while also taking into account the management of negative sequence current, zero sequence current, and neutral line current in a three-phase four-wire system. Summary of the Invention

[0007] To address the challenges in effectively distinguishing between short-term and sustained imbalances in existing temporary power distribution systems at construction sites, the susceptibility of multi-phase capacitor passive coarse adjustment branches to frequent switching due to instantaneous load fluctuations, the tendency for compensation step jumps to occur during switching between four-arm SVG active fast balancing branches and multi-phase capacitor passive coarse adjustment branches, and the difficulty in coordinating the management of negative sequence current, zero sequence current, and neutral line current in three-phase four-wire power supply systems, this invention provides a construction site temporary intelligent power distribution cabinet with layered three-phase balancing hardware. This distribution cabinet identifies the amplitude and duration of three-phase imbalance. Based on the identification results, it implements hierarchical coordinated control of the four-arm SVG active fast balancing branch and the multi-stage phase-to-phase capacitor passive coarse adjustment branch. This ensures that short-term impact imbalances are prioritized for dynamic compensation by the four-arm SVG active fast balancing branch. Once a sustained imbalance reaches a set condition, the multi-stage phase-to-phase capacitor passive coarse adjustment branch takes over steady-state compensation. Furthermore, it coordinates and adjusts the compensation output of the four-arm SVG active fast balancing branch during the connection or disconnection of the phase-to-phase capacitor branch to reduce abrupt changes in compensation caused by connections between different compensation branches. Simultaneously, the four-arm SVG active fast balancing branch dynamically compensates for negative-sequence and zero-sequence currents, thereby improving the stability of three-phase load balancing under random load fluctuations at the construction site and reducing the operational impact caused by frequent switching of the neutral line current and phase-to-phase capacitor branches.

[0008] The technical solution adopted in this invention is as follows: A temporary intelligent power distribution cabinet for construction sites with layered three-phase balancing hardware includes a mobile protective cabinet for construction sites, a main incoming line protection unit, a main three-phase acquisition unit, a multi-branch power distribution unit, and an edge intelligent main control unit. It also includes a dual-dimensional hardware identification unit for impact loads and a layered three-phase balancing control module. The output side of the main line incoming protection unit is connected to the A-phase busbar, B-phase busbar, C-phase busbar and N-line busbar respectively. The main three-phase acquisition unit is set on the output side of the main line incoming protection unit to acquire the voltage and current of A-phase, B-phase, C-phase and N-line current, and is connected to the edge intelligent main control unit. The impact load dual-dimensional hardware identification unit includes a first comparator, a second comparator, an RS flip-flop, and a duration determination circuit. The first comparator is used to output a set signal to the set terminal of the RS flip-flop when the negative sequence current imbalance reaches the first action threshold. The second comparator adopts the opposite comparison polarity to the first comparator and is used to output a reset signal to the reset terminal of the RS flip-flop when the negative sequence current imbalance drops to the second recovery threshold. The second recovery threshold is lower than the first action threshold. The layered three-phase equalization control module includes a four-arm SVG active fast equalization branch, a multi-stage phase-to-phase capacitor passive coarse adjustment branch, and a compensation quantity disturbance-free transfer control unit. The AC side of the four-arm SVG active fast equalization branch is connected to the A-phase busbar, B-phase busbar, C-phase busbar, and N-line busbar, respectively. The multi-stage phase-to-phase capacitor passive coarse adjustment branch is connected between the A-phase busbar, B-phase busbar, and C-phase busbar. The set output of the RS flip-flop forms two control paths. The first path is connected to the fast compensation enable terminal of the four-bridge arm SVG active fast equalization branch, and the second path is connected to the switching enable terminal of the multi-stage phase-to-phase capacitor passive coarse adjustment branch via the duration determination circuit. The duration determination circuit determines the duration for which the RS flip-flop is continuously set. If the continuous set time of the RS flip-flop has not reached the set duration, the new switching lockout of the multi-stage phase-to-phase capacitor passive coarse adjustment branch is maintained. After the continuous set time of the RS flip-flop has reached the set duration, the new switching lockout of the multi-stage phase-to-phase capacitor passive coarse adjustment branch is released, and the duration determination restarts after the RS flip-flop is reset. Each phase-to-phase capacitor branch of the multi-stage phase-to-phase capacitor passive coarse adjustment branch is equipped with a branch current sensor. The detection output terminal of the branch current sensor is connected to the edge intelligent main control unit. The edge intelligent main control unit determines the actual capacitive compensation amount undertaken by the phase-to-phase capacitor branch based on the phase-to-phase voltage and the actual current of the phase-to-phase capacitor branch. The compensation quantity seamless handover control unit is connected to the four-arm SVG active fast balancing branch and the multi-stage phase-to-phase capacitor passive coarse adjustment branch, respectively. It adjusts the compensation output of the four-arm SVG active fast balancing branch according to the actual capacitive compensation amount established or disappeared during the phase-to-phase capacitor connection or disconnection. When the phase-to-phase capacitor is connected, the compensation output of the four-arm SVG active fast balancing branch is reduced accordingly. When the phase-to-phase capacitor is disconnected, the four-arm SVG active fast balancing branch takes over the capacitor compensation amount to be disappeared.

[0009] Furthermore, the interior of the mobile protective cabinet at the construction site is equipped with a main inlet and acquisition area, a layered three-phase balanced control area, and branch output areas along the height direction; The main line incoming protection unit and the main line three-phase acquisition unit are installed in the main line incoming and acquisition area. The four-bridge arm SVG active fast balancing branch and the multi-stage phase-to-phase capacitor passive coarse adjustment branch are installed in the layered three-phase balancing control area. The multi-circuit branch power distribution unit is installed in the branch output area. The three-phase balanced control area is equipped with an independent balanced compartment. The four-bridge SVG active fast balanced branch and the multi-stage phase-to-phase capacitor passive coarse adjustment branch are set in the independent balanced compartment. The mobile protective cabinet for construction sites is equipped with a waterproof and dustproof door, and the bottom of the cabinet is equipped with a drainage channel and self-locking casters or adjustable feet.

[0010] Furthermore, the three-phase acquisition unit includes three phase current sensors respectively installed on the A-phase, B-phase and C-phase main conductors, an N-line current sensor installed on the N-line main conductor, and voltage sampling terminals respectively connected to the A-phase busbar, B-phase busbar and C-phase busbar; The edge intelligent master control unit performs symmetrical component decomposition based on the fundamental current phasors of phases A, B, and C. The positive-sequence current phasors, negative-sequence current phasors, and zero-sequence current phasors are determined according to the following formulas: ; ; ; in, , and These represent the fundamental current phasors of phases A, B, and C, respectively. Represents the positive sequence current phasor; Represents the negative sequence current phasor; Represents the zero-sequence current phasor; express Rotation operator, satisfying: ; in, Represents the imaginary unit; Negative sequence current unbalance is denoted as And determine according to the following formula: ; The edge intelligent main control unit converts the negative sequence current imbalance through a digital-to-analog converter circuit. Convert to unbalanced analog voltage: ; in, This represents the analog voltage representing the unbalance input to the first and second comparators, respectively. This represents the proportional conversion gain between the negative sequence current imbalance and the unbalanced analog voltage; the digital-to-analog converter circuit is either a DAC circuit or consists of a PWM output terminal and a low-pass filter circuit.

[0011] Furthermore, let the first action threshold be... The second recovery threshold is And satisfy: ; The analog reference voltage corresponding to the first action threshold is: ; The analog reference voltage corresponding to the second recovery threshold is: ; The first comparator is in The set signal is output to the set terminal of the RS flip-flop; The second comparator is in The timer outputs a reset signal to the reset terminal of the RS flip-flop; Let the logic state of the output of the RS flip-flop be... ,but: hour: ; hour: ; when hour: ; in, Indicates the current state of the RS trigger. This indicates the state of the RS trigger before the current time.

[0012] Furthermore, the duration determination circuit includes an RC integral delay branch, a threshold comparison section, and a discharge reset branch. The RC integral delay branch is connected between the set output terminal of the RS flip-flop and the switching enable terminal of the passive coarse adjustment branch of the multi-stage phase-to-phase capacitor. When the RS flip-flop remains in the set state, the capacitor voltage in the RC integral delay branch changes according to the following formula: ; when When the threshold comparison section outputs a continuous imbalance confirmation signal, the corresponding set duration is: ; in, This indicates that the continuous set time of the RS flip-flop is... The capacitor voltage of the RC integral delay branch; This represents the charging voltage of the RC integral delay branch; Indicates the delay resistor; Indicates the delay capacitor; This indicates the trigger voltage for confirming continuous imbalance; This indicates the set duration that distinguishes between short-term shock imbalance and sustained imbalance; When the RS flip-flop receives a reset signal, the discharge reset branch discharges the delay capacitor and clears the current continuous set time. The threshold comparison section is composed of the threshold comparison structure inside the NE555 timer, or it is composed of an independent threshold comparator.

[0013] Furthermore, the four-arm SVG active fast equalization branch includes the A-phase arm, B-phase arm, C-phase arm, neutral arm, DC bus capacitor, AC side filter inductor, power switching devices, power switch drive circuit and SVG controller. Phase A arm, phase B arm, and phase C arm are connected to phase A busbar, phase B busbar, and phase C busbar respectively via corresponding AC side filter inductors; the neutral arm is connected to the N busbar. The SVG controller generates A-phase, B-phase, C-phase, and neutral line compensation current commands based on the three-phase load current, where: ; ; ; ; in, , , These represent the instantaneous load currents of phases A, B, and C, respectively. , , These represent the expected instantaneous currents on the power supply side for phases A, B, and C, respectively. , , These represent the compensation current commands for phase A, phase B, and phase C bridge arms, respectively. This indicates the compensation current command for the neutral line arm; The four-arm SVG active fast equalization branch is configured to undertake short-time impulse compensation, negative sequence current compensation, zero sequence current compensation, and residual dynamic compensation after the switching of the multi-stage phase-to-phase capacitor passive coarse adjustment branch.

[0014] Furthermore, the multi-stage interphase capacitor passive coarse adjustment branch includes the AB interphase capacitor group, the BC interphase capacitor group, and the CA interphase capacitor group. The AB phase-to-phase capacitor bank is connected between the A phase busbar and the B phase busbar, the BC phase-to-phase capacitor bank is connected between the B phase busbar and the C phase busbar, and the CA phase-to-phase capacitor bank is connected between the C phase busbar and the A phase busbar. Each phase-to-phase capacitor bank includes multiple phase-to-phase capacitor branches with different capacities that can be switched independently. Each phase-to-phase capacitor branch is connected in series with a branch protection device and a zero-inrush-current thyristor composite switch. Each phase-to-phase capacitor bank has , and Three phase-to-phase capacitor branches with nominal capacitance levels; The interphase capacitor branches corresponding to the same nominal capacity level in the AB, BC, and CA interphase capacitor groups can be synchronously controlled according to the three-phase symmetrical coarse adjustment requirements. The multi-stage passive coarse adjustment branches of the interphase capacitors are used to bear the steady-state reactive power compensation base value under continuous imbalance conditions.

[0015] Furthermore, the edge intelligent main control unit determines the total active power of the load. Total reactive power of the load and target power factor Determine the target steady-state reactive power compensation amount: ; in: ; This represents the target steady-state reactive power compensation amount; This represents the total active power of the load; This indicates the total reactive power of the load; Indicates the target power factor; Indicates the target power factor angle; Let the total allowable compensation capacity set of the multi-phase inter-capacitor passive coarse adjustment branch be . Selected passive coarse adjustment compensation capacity Determined according to the following formula: ; make: ; The remaining reactive power compensation requirement is: ; in, It is handled by the four-bridge arm SVG active fast equalization branch.

[0016] Furthermore, each interphase capacitor branch is equipped with a branch current sensor, and the detection output terminal of the branch current sensor is connected to the edge intelligent main control unit. The edge intelligent main control unit determines the actual capacitive compensation amount of the corresponding interphase capacitor branch based on the interphase voltage and the actual current of the interphase capacitor branch. for For interphase capacitor branches, the actual capacitive compensation amount is determined according to the following formula: ; in, express Actual capacitive compensation amount for interphase capacitor branches; express Effective value of phase-to-phase voltage; express Effective value of interphase capacitor branch current; express The phase difference between the phase-to-phase voltage and the fundamental current of the phase-to-phase capacitor branch; The sum of the capacitive compensation amounts of each phase-to-phase capacitor branch actually implemented is denoted as: The compensation amount seamless handover control unit determines the residual reactive power compensation command of the four-arm SVG active fast equalization branch according to the following formula: ; in, Indicates time Reactive power compensation command for the four-arm SVG active fast equalization branch; Indicates time The target steady-state reactive power compensation; Indicates time The actual capacitive compensation amount undertaken by the passive coarse adjustment branch of the multi-phase capacitor; During the connection or disconnection of phase-to-phase capacitors, the transfer factor is determined according to the following formula: ; in, Indicates the start time of the compensation handover; Indicates the preset handover time; Indicates the variable Limited to to Amplitude limiting function within the range; When the phase-to-phase capacitor is engaged, the feedforward handover command of the four-arm SVG active fast equalization branch satisfies: ; When the interphase capacitors are deactivated, the feedforward handover command of the four-arm SVG active fast equalization branch satisfies: ; in, This indicates the feedforward handover command for the four-arm SVG active fast equalization branch; This indicates the SVG reactive power compensation command prior to the start of the handover. This indicates the compensation capacity corresponding to the phase-to-phase capacitors to be put into or taken out. After the interphase capacitors are actually connected or disconnected, then according to Feedback correction is performed on the compensation output of the active fast equalization branch of the four-bridge arm SVG.

[0017] Furthermore, it also includes a graded leakage current protection unit, a temperature monitoring and protection unit, and a remote communication alarm unit; The graded leakage current protection unit includes a main circuit residual current detection component and multiple branch circuit residual current detection components corresponding to each branch of the multi-circuit power distribution unit. The main circuit residual current detection component includes a zero-sequence current transformer installed in the main circuit. The four main circuit working conductors, A-phase, B-phase, C-phase and N-line, all pass through the main circuit zero-sequence current transformer, while the PE protection conductor does not pass through. Each branch circuit residual current detection component includes a zero-sequence current transformer installed in the corresponding branch circuit. The working conductors of each branch circuit all pass through the corresponding zero-sequence current transformer. The temperature monitoring and protection unit includes multiple temperature sensors respectively located in the four-bridge arm SVG active fast equalization branch, the multi-stage phase-to-phase capacitor passive coarse adjustment branch, the N-line busbar, and inside the cabinet. The edge intelligent main control unit is connected to each zero-sequence current transformer, each temperature sensor and remote communication alarm unit, and outputs early warning signals or protection control signals based on the detected residual current, neutral line current and temperature. The remote communication alarm unit includes a wireless communication module for transmitting information on three-phase current, negative sequence current imbalance, neutral line current, four-arm SVG compensation status, capacitor level, temperature status, and leakage status.

[0018] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention uses a first comparator, a second comparator, an RS flip-flop, and a duration determination circuit to jointly identify the amplitude and duration of three-phase unbalance. When the negative sequence current imbalance reaches a first action threshold, the first comparator sets the RS flip-flop and immediately enables the four-arm SVG active fast equalization branch, while simultaneously initiating the duration determination. If the RS flip-flop remains set for less than the set duration, the multi-phase interphase capacitor passive coarse adjustment branch remains locked for new switching. Only after the RS flip-flop remains set for the set duration is the new switching lockout of the multi-phase interphase capacitor passive coarse adjustment branch released. This allows for the differentiation between short-term impact imbalances such as welding machine arc ignition and motor startup and continuous imbalances, reducing frequent switching of capacitor branches caused by short-term impact loads.

[0019] 2. This invention employs a four-arm SVG active fast balancing branch and a multi-stage phase-to-phase capacitor passive coarse adjustment branch to form a layered three-phase balancing structure. The four-arm SVG active fast balancing branch is responsible for short-term impact, negative sequence current, zero sequence current, and the remaining dynamic compensation after passive coarse adjustment. The multi-stage phase-to-phase capacitor passive coarse adjustment branch is responsible for the steady-state reactive power compensation base value under continuous imbalance conditions. This combines the fast dynamic compensation capability with the large-capacity steady-state compensation capability, which can adapt to the power consumption conditions of random start-stop and frequent fluctuations of loads at construction sites.

[0020] 3. This invention sets up a compensation quantity seamless handover control unit and adjusts the compensation output of the four-arm SVG according to the actual capacitive compensation amount undertaken by the interphase capacitor branch. When the interphase capacitor is engaged, the compensation output of the four-arm SVG is synchronously reduced according to the actual compensation amount established by the interphase capacitor; before the interphase capacitor is disengaged, the four-arm SVG first pre-handles the compensation amount corresponding to the capacitor to be disengaged, and after the interphase capacitor is disengaged, it continues to correct the SVG output according to the actual compensation amount feedback, so that the active compensation amount and the passive compensation amount remain continuous during the branch handover process, reducing the compensation amount step and the secondary fluctuation of the three-phase current caused by the engagement or disengagement of the capacitor.

[0021] 4. The four-arm SVG active fast balancing branch of the present invention is connected to the A-phase busbar, B-phase busbar, C-phase busbar and N-line busbar respectively. It compensates for the three-phase imbalance and residual dynamic quantity through the three phase arms and outputs zero-sequence compensation current using the neutral line arm. Therefore, it can not only improve the negative sequence current imbalance, but also dynamically adjust the zero-sequence current in the three-phase four-wire construction power supply system, which is beneficial to reduce the N-line current on the power supply side and its long-term overcurrent and temperature rise risks.

[0022] 5. This invention employs a dual-threshold hysteresis judgment structure with a first action threshold and a second recovery threshold, and uses an RS flip-flop to maintain the abnormal imbalance state. When the negative sequence current imbalance is between the first action threshold and the second recovery threshold, the RS flip-flop maintains the previous logic state, thereby reducing the repeated start-stop of the compensation branch caused by the fluctuation of the negative sequence current imbalance near the threshold. At the same time, the duration determination circuit forms an independent time enable constraint for the passive coarse adjustment branch, further improving the anti-interference capability of the compensation control under random impact conditions at the construction site.

[0023] 6. This invention integrates three-phase data acquisition, negative-sequence and zero-sequence component calculation, layered three-phase balancing, leakage current detection, neutral line current monitoring, and temperature monitoring into a single temporary intelligent power distribution cabinet at the construction site. It also centrally monitors three-phase current, unbalanced state, SVG compensation state, capacitor switching state, neutral line current, leakage current state, and temperature state through an edge intelligent main control unit and a remote communication alarm unit, which is beneficial for achieving the integration of three-phase balancing regulation and construction temporary power safety monitoring.

[0024] 7. The four-arm SVG active fast balancing branch and the multi-stage phase-to-phase capacitor passive coarse adjustment branch of the present invention are set in an independent balancing compartment inside the cabinet. Combined with the cabinet's waterproof and dustproof structure, drainage and flow guiding structure, and movable or lifting support structure, the impact of dust, water vapor and cabinet transfer vibration on the operation of balancing devices at the construction site can be reduced, and the adaptability of the distribution cabinet to the temporary power supply environment at the construction site can be improved. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the embodiments are briefly described below. It should be understood that the following drawings are only used to illustrate the technical solutions of the present invention and do not constitute a limitation on the scope of protection of the present invention.

[0026] Figure 1 This is a schematic diagram illustrating the overall structure and functional composition of a temporary intelligent power distribution cabinet for construction sites with layered three-phase balancing hardware according to the present invention. Figure 2 This is a schematic diagram showing the internal layout of the mobile protective cabinet for construction sites and the installation positions of its main components. Figure 3 This is a schematic diagram showing the signal transmission relationship between the three-phase acquisition unit, the edge intelligent main control unit, and the two-dimensional hardware identification unit for impact load in this invention. Figure 4 This is a schematic diagram of the circuit principle of the dual threshold comparison, RS state holding and duration determination of the dual-dimensional hardware identification unit for impact load of the present invention. Figure 5 This is a schematic diagram of the connection structure between the four-arm SVG active fast equalization branch of the present invention and the A-phase busbar, B-phase busbar, C-phase busbar and N-line busbar; Figure 6 This is a schematic diagram showing the structure of the passive coarse adjustment branch of the multi-stage interphase capacitors of the present invention and the connection relationship of the interphase capacitor groups AB, BC, and CA. Figure 7 This is a schematic diagram of the two-dimensional identification and hierarchical compensation control process for short-term impact imbalance and continuous imbalance of the present invention. Figure 8 This is a schematic diagram illustrating the seamless handover of compensation amounts between the four-arm SVG active fast balancing branch and the multi-stage passive coarse adjustment branch of the interphase capacitors during the phase-to-phase capacitor connection and disconnection process of the present invention. Figure 8 (a) is a schematic diagram of the seamless handover of compensation during the connection of the phase-to-phase capacitor branch. Figure 8 (b) is a schematic diagram of the seamless handover of compensation during the phase-to-phase capacitor branch disconnection process; Figure 9 This is a schematic diagram showing the overall connection and operation control of the present invention when applied to a temporary 8-channel intelligent power distribution cabinet in a building construction project. Detailed Implementation

[0027] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the following embodiments are used to illustrate the structural composition, installation location, connection relationship, control logic, working principle, and technical effects of the present invention, and are not intended to limit the scope of protection of the present invention. Without departing from the technical concept of the present invention, those skilled in the art can make adaptive adjustments to the cabinet size, current sensor transformation ratio, SVG rated capacity, capacitor branch capacity, action threshold, recovery threshold, duration threshold, and communication method according to the temporary power supply capacity of the construction site, the type of electrical equipment, the number of branches, the degree of three-phase load imbalance, and the site environment.

[0028] For ease of explanation, the three phase lines of the three-phase four-wire power supply at the construction site are defined as phase A, phase B, and phase C, respectively, and the neutral line is defined as the N line; the corresponding conductive busbars in the distribution cabinet are defined as phase A busbar, phase B busbar, phase C busbar, and N line busbar, respectively.

[0029] like Figure 1As shown, this embodiment provides a temporary intelligent power distribution cabinet for construction sites with layered three-phase balancing hardware, mainly used in... A three-phase four-wire temporary power supply system can supply power to AC welding machines, vibrating equipment, cutting equipment, hand-held power tools, lighting equipment, motor equipment and other construction loads.

[0030] The temporary intelligent power distribution cabinet at the construction site includes a mobile protective cabinet, a main line incoming protection unit, a main line three-phase acquisition unit, a layered three-phase balancing control module, a dual-dimensional hardware identification unit for impact loads, an edge intelligent main control unit, a graded leakage protection unit, a temperature monitoring and protection unit, a remote communication alarm unit, and a multi-circuit power distribution unit.

[0031] The layered three-phase equalization control module includes a four-arm SVG active fast equalization branch, a multi-stage phase-to-phase capacitor passive coarse adjustment branch, and a compensation quantity disturbance-free handover control unit.

[0032] The core control mechanism of this embodiment does not simply combine the four-arm SVG active fast balancing branch with the multi-stage phase-to-phase capacitor passive coarse adjustment branch. Instead, it first uses a dual-dimensional hardware identification unit for impact load to jointly identify the amplitude and duration of the three-phase imbalance state. Then, based on the identification results, it determines the intervention timing of the four-arm SVG active fast balancing branch and the multi-stage phase-to-phase capacitor passive coarse adjustment branch. When the phase-to-phase capacitor branch is engaged or disengaged, the output of the four-arm SVG active fast balancing branch is synchronously adjusted according to the actual capacitive compensation amount established or disappeared by the phase-to-phase capacitor branch, so that a continuous control relationship is formed between the active compensation amount and the passive compensation amount.

[0033] I. Mobile protective cabinet for construction sites: like Figure 2 As shown, the mobile protective cabinet for construction sites is a vertical enclosed cabinet structure, including the cabinet shell, cabinet door, internal mounting plate, busbar mounting frame, low-voltage mounting frame, and bottom support structure.

[0034] The cabinet shell is preferably made of steel plate, and a waterproof and dustproof sealing structure is set between the cabinet door and the cabinet body to reduce the entry of dust, water vapor and mud splashes into the cabinet body at the construction site.

[0035] The cabinet is divided along its height into a main inlet and acquisition area, a layered three-phase balanced control area, and a branch output area.

[0036] The main circuit incoming line and data acquisition area are located at the top of the cabinet. The main circuit incoming line protection unit and the main circuit three-phase data acquisition unit are installed in this area, so that after the external three-phase four-wire power supply enters the cabinet, it first passes through the main circuit protection and then the main circuit electrical parameters are acquired.

[0037] The layered three-phase balancing control area is located in the middle of the cabinet and has an independent balancing compartment. The four-arm SVG active fast balancing branch and the multi-stage interphase capacitor passive coarse adjustment branch are installed in the independent balancing compartment. The independent balancing compartment is physically isolated from the low-voltage control area where the edge intelligent main control unit, the impact load dual-dimensional hardware identification unit, and the remote communication alarm unit are located, in order to reduce the impact of heat and electromagnetic interference generated by SVG power devices, interphase capacitors, and thyristor composite switches on the low-voltage control devices.

[0038] The temperature monitoring and protection unit is located inside the cabinet, with its temperature sensors deployed on the SVG power module, multi-phase capacitors, thyristor composite switch, N busbar, and the cabinet's environmental monitoring location.

[0039] The multi-circuit power distribution unit is installed in the branch output area at the bottom of the cabinet.

[0040] The cabinet is equipped with a drainage channel at the bottom and self-locking casters or adjustable feet. The distribution cabinet is moved using the casters and secured at the work location using the self-locking mechanism or adjustable feet.

[0041] II. Main incoming line protection unit and power supply connection relationship: The three-phase four-wire power supply at the construction site consists of phase A, phase B, phase C, and neutral (N) wires.

[0042] Phase A, phase B, and phase C are first connected to the main incoming line protection unit, and then connected to the A-phase busbar, B-phase busbar, and C-phase busbar respectively; the N-line is connected to the N-line busbar.

[0043] The main incoming line protection unit may include a main molded case circuit breaker, a short-circuit protection structure, an overload protection structure, and a surge protection structure.

[0044] The A-phase busbar, B-phase busbar, C-phase busbar, and N-line busbar provide the electrical connection foundation for the multi-path distribution unit and the hierarchical three-phase equalization control module, respectively.

[0045] The four-arm SVG active fast equalization branch is connected in parallel to the A-phase busbar, B-phase busbar, C-phase busbar and N-line busbar respectively.

[0046] The multi-phase interphase capacitor passive coarse adjustment branch is connected between phase A busbar and phase B busbar, phase B busbar and phase C busbar, and phase C busbar and phase A busbar respectively.

[0047] III. Three-phase data acquisition unit for main circuit: like Figure 3As shown, the three-phase acquisition unit of the main line is installed on the output side of the main line incoming line protection unit, including A-phase current sensor, B-phase current sensor, C-phase current sensor, N-line current sensor, A-phase voltage sampling terminal, B-phase voltage sampling terminal, C-phase voltage sampling terminal, signal conditioning circuit and analog-to-digital conversion circuit.

[0048] The phase A current sensor is installed on the phase A main conductor, the phase B current sensor is installed on the phase B main conductor, the phase C current sensor is installed on the phase C main conductor, and the neutral line current sensor is installed separately on the neutral line main conductor.

[0049] The three voltage sampling terminals are connected to the A-phase busbar, the B-phase busbar, and the C-phase busbar, respectively.

[0050] This yields the three-phase instantaneous voltage: ; And the three-phase load current and the neutral line current: ; in, Representing time respectively The instantaneous voltages of phases A, B, and C; Representing time respectively The instantaneous load currents of phases A, B, and C; This represents the instantaneous current in the N-line.

[0051] The edge intelligent main control unit calculates the effective value of the three-phase current based on the sampled data: ; ; ; in, These represent the effective values ​​of the three-phase currents A, B, and C, respectively. Indicates the calculation period; Indicates the start time of the calculation window.

[0052] for Temporary power supply for construction, one fundamental frequency period is One or more complete power frequency cycles can be used as the basic calculation window.

[0053] IV. Calculation of Positive Sequence, Negative Sequence, and Zero Sequence Currents: The edge intelligent main control unit obtains the three-phase fundamental current phasors of A, B, and C through digital filtering, discrete Fourier transform, or other fundamental frequency extraction methods: ; definition Rotation operator: ; Accordingly: ; in, express Rotation operator, It represents the imaginary unit.

[0054] The positive sequence current phasor is: ; The negative sequence current phasor is: ; The zero-sequence current phasor is: ; in, Represents the positive sequence current phasor. Represents the negative sequence current phasor. This represents the zero-sequence current phasor.

[0055] This embodiment employs negative sequence current imbalance. As the main amplitude input of the two-dimensional hardware identification unit for impact load: ; in, This represents the magnitude of the negative sequence current phasor. This represents the magnitude of the positive sequence current phasor.

[0056] It can also calculate the zero-sequence current ratio: ; in, This indicates the proportion of zero-sequence current.

[0057] Based on the node current relationships in a three-phase four-wire circuit: ; Combining the definition of zero-order components, we get: ; Therefore, the zero-sequence load current can form the operating current through the N-line. In this embodiment, the neutral line arm in the four-arm SVG is used to form an independent zero-sequence compensation path.

[0058] V. Connection between imbalance calculation results and hardware identification unit: See also Figure 3 Negative sequence current imbalance Digital calculations are performed by the edge intelligent master control unit, while the first and second comparators operate using hardware comparison. Therefore, an unbalanced digital-to-analog conversion circuit is set between the edge intelligent master control unit and the two comparators.

[0059] The digital-to-analog converter circuit can use a DAC, or it can use a PWM output combined with a low-pass filter circuit to form a signal-to-analog converter. Corresponding analog voltage:

[0060] in, This represents the analog voltage indicating the imbalance between the input first comparator and the second comparator; Indicates the proportional conversion gain; Dimensionless values ​​are used when performing proportional conversions.

[0061] This leads to: The signal chain.

[0062] This setting ensures that the eligibility for intervention of the multi-phase inter-capacitor passive coarse adjustment branch is not only controlled by the software calculation results, but also constrained by independent hardware amplitude and duration determination.

[0063] VI. Dual threshold comparison and RS state maintenance: like Figure 4 As shown, the impact load dual-dimensional hardware identification unit includes a first comparator, a second comparator, an RS flip-flop, a duration determination circuit, and a discharge reset branch.

[0064] Let the first action threshold be The second recovery threshold is And satisfy: ; The corresponding analog reference voltages are as follows: ; ; The first comparator uses and Compare, and in: The set input S of the time-directed RS flip-flop outputs a valid set signal.

[0065] The second comparator uses the opposite comparison polarity to the first comparator, i.e., to restore the reference voltage. Analog voltage with unbalance According to the second comparator: It is connected in a way that outputs a valid reset signal, and its output terminal is connected to the reset terminal R of the RS flip-flop.

[0066] Let the logic state of the output of the RS flip-flop be... ,but: when: hour: The RS flip-flop is set. when: hour: RS flip-flop reset; when: hour: ; in, This indicates the current state of the RS trigger. This indicates the state of the RS trigger prior to the current time. Therefore, a hysteresis interval is formed between the first action threshold and the second recovery threshold.

[0067] In a preferred embodiment: ; ; When the negative sequence current imbalance reaches When the RS flip-flop is set, it remains set even if the negative sequence current imbalance decreases to [value missing]. In between, the RS flip-flop remains in its previous set state; only when the negative sequence current imbalance further decreases to The RS trigger is reset only when the following conditions are met:

[0068] By maintaining this state relationship, it is possible to avoid repeated switching of the equalization control caused by fluctuations in the negative sequence current imbalance around the first action threshold and the second recovery threshold.

[0069] VII. Duration determination and two-dimensional hardware identification: See also Figure 4 The set output of the RS flip-flop forms two control paths.

[0070] The first path is directly connected to the fast compensation enable terminal of the active fast equalization branch of the four-arm SVG. Therefore, once the RS flip-flop is set, the four-arm SVG can enter the fast compensation state.

[0071] The second path connects to the duration determination circuit, which in turn connects to the switching enable terminal of the passive coarse adjustment branch of the multi-phase inter-capacitor circuit.

[0072] Duration in this embodiment This refers to the duration for which the RS flip-flop remains in the set state, not just the negative sequence current imbalance. Continuously exceeding the first action threshold The time.

[0073] Therefore, when: Furthermore, if the RS flip-flop has already been set, the RS flip-flop remains unchanged: ; The duration determination continues to accumulate; only when: The duration accumulation is cleared only after the RS flip-flop is reset.

[0074] The duration determination circuit includes an RC integral delay branch, a threshold comparison section, and a discharge reset branch.

[0075] When the RS flip-flop remains continuously set, the capacitor voltage in the RC integral delay branch satisfies: ; in, This indicates that the continuous set time of the RS flip-flop is... The delay capacitor voltage at that time; Indicates the charging voltage; Indicates the delay resistor; This indicates the delay capacitor.

[0076] when: At that time, the threshold comparison section outputs a continuous imbalance confirmation signal.

[0077] The corresponding set duration is: ; in, This indicates the trigger voltage for confirming continuous imbalance; This indicates the set duration that distinguishes between short-term impact imbalance and sustained imbalance. This is achieved by matching the delay resistor. Delay capacitor Charging voltage and the trigger voltage for confirming continuous imbalance The set duration can be set according to the duration characteristics of the impact load at the construction site. .

[0078] In implementations using the NE555 timer, the duration determination can be achieved by using the threshold comparison structure inside the NE555 in conjunction with an RC delay network; alternatively, a separate threshold comparator can be used in conjunction with an RC integral delay branch to determine the duration.

[0079] When the RS flip-flop receives a reset signal, the discharge reset branch causes the delay capacitor to discharge rapidly, resulting in: Thus, the full duration accumulation restarts after the RS trigger is re-set.

[0080] Therefore, this embodiment uses the duration for which the RS flip-flop remains in the set state as the duration criterion. When the RS flip-flop is in the set state and its continuous set time... Reaching the set duration At that time, that is:

[0081] and:

[0082] The duration determination circuit outputs a continuous imbalance confirmation signal. The persistent imbalance confirmation signal Simultaneously, it serves as the switching enable signal for the passive coarse adjustment branch of the multi-phase interphase capacitor; when the persistent imbalance has not yet been confirmed. When the persistent imbalance is confirmed, .

[0083] when: If the RS flip-flop was already in the set state, the RS flip-flop will remain set for a continuous set time. Continue accumulating; only when: The duration accumulation is only cleared after the RS flip-flop is reset.

[0084] This forms a two-dimensional hardware identification process of "amplitude determination + state maintenance + duration confirmation".

[0085] 8. Hardware interlocking of passive coarse adjustment branch: The edge intelligent master control unit can generate software switching commands for each phase capacitor branch according to the steady-state reactive power compensation requirements, but the software switching commands do not directly drive the zero-inrush current thyristor composite switch.

[0086] Let the first The software switching command for each phase-to-phase capacitor branch is: The duration determination circuit outputs a continuous imbalance confirmation signal as follows: The persistent imbalance confirmation signal Simultaneously, it serves as the switching enable signal for the passive coarse adjustment branch of the multi-phase interphase capacitor; when temperature, leakage current, and power device status all meet the safe operating conditions, it generates a safety permission signal. Then it will eventually be sent to the first... The permissible signal for the switching of the interphase capacitor branch must satisfy: ; in, It represents the logical AND.

[0087] When the persistent imbalance has not yet been confirmed: ; therefore: ; Even if the edge intelligent master control unit believes that there is a large reactive power compensation requirement based on instantaneous calculation results, it cannot add new phase-to-phase capacitor branches.

[0088] When persistent imbalance is confirmed: ; At this point, the passive coarse adjustment branch of the multi-phase capacitor becomes eligible for switching. Whether the specific phase capacitor branch is activated is still determined by the corresponding software switching command. and safety permission signals To be determined jointly.

[0089] This structure allows the eligibility of the passive coarse adjustment branch of the multi-phase capacitor to be constrained by independent hardware duration conditions, rather than relying entirely on the software delay program of the edge intelligent master control unit.

[0090] 9. Four-arm SVG active fast equalization branch: like Figure 5 As shown, the four-bridge SVG active fast balancing branch is located in an independent balancing compartment in the middle of the cabinet, including the A-phase bridge arm, B-phase bridge arm, C-phase bridge arm, neutral line bridge arm, DC bus capacitor, A-phase AC side filter inductor, B-phase AC side filter inductor, C-phase AC side filter inductor, power switching devices, power switch drive circuit, and SVG controller.

[0091] Phase A bridge arm is connected to Phase A busbar via Phase A AC side filter inductor; Phase B bridge arm is connected to Phase B busbar via Phase B AC side filter inductor; Phase C bridge arm is connected to Phase C busbar via Phase C AC side filter inductor; Neutral bridge arm is connected to N busbar.

[0092] The AC output points of phase A, phase B, and phase C bridge arms are independent of each other, and the AC output point of the neutral bridge arm is independently connected to the N-line busbar.

[0093] Power switching devices can be IGBTs or other fully controllable power semiconductor devices that meet the requirements of rated voltage, rated current and switching frequency.

[0094] The three phase bridge arms are used to form the three-phase compensation currents A, B, and C, while the neutral bridge arm is used to form an independent zero-sequence compensation current path.

[0095] 10. SVG compensation current calculation and DC bus closed-loop: The total active power of the load is: ; The effective value of the average phase voltage of the three phases is: ; in, These represent the effective values ​​of the phase voltages of phases A, B, and C, respectively.

[0096] The SVG controller obtains the fundamental phase angle of the power grid through a phase-locked loop. .

[0097] Assume the actual DC bus voltage is The target DC bus voltage is Then the DC bus voltage error is: ; The active power correction for maintaining DC bus energy balance is obtained using PI control: ; in, Indicates the proportionality coefficient; This represents the integral coefficient.

[0098] The actual active power command is: ; The expected effective value of the balanced active current per phase is: ; Therefore, the instantaneous current on the three-phase desired power supply side is obtained: ; ; ; The compensation current commands for the three phase bridge arms are as follows: ; ; ; The neutral bridge arm compensation current command is as follows: ; By outputting unbalanced compensation current through the three phase bridge arms A, B, and C, and zero-sequence compensation current through the neutral bridge arm, the three-phase currents on the power supply side can be made more symmetrical, and the degree of zero-sequence current transmission to the upstream power supply side can be reduced.

[0099] The SVG controller further enables the actual compensation current to track the corresponding compensation current command through current closed-loop, and generates drive pulses for the power switching devices through PWM modulation.

[0100] When the instantaneous compensation demand exceeds the rated capacity of the SVG, the compensation current command is limited.

[0101] Define the compensation current command vector: ; Let the maximum allowable compensation current of SVG be ,when: hour: ; in, This indicates the compensation current command after limiting.

[0102] Preferably, when the SVG capacity is insufficient, the compensation capacity required for negative-sequence and zero-sequence governance is reserved first, and then the output priority of the pure reactive power compensation part is reduced.

[0103] XI. Passive coarse adjustment branch with multi-stage interphase capacitors: like Figure 6 As shown, the multi-stage interphase capacitor passive coarse adjustment branch includes the AB interphase capacitor group, the BC interphase capacitor group, and the CA interphase capacitor group.

[0104] The AB phase-to-phase capacitor bank is connected between the A-phase busbar and the B-phase busbar; the BC phase-to-phase capacitor bank is connected between the B-phase busbar and the C-phase busbar; and the CA phase-to-phase capacitor bank is connected between the C-phase busbar and the A-phase busbar.

[0105] Each phase-to-phase capacitor bank is equipped with multiple phase-to-phase capacitor branches of different capacities that can be switched independently. Each phase-to-phase capacitor branch is connected in series with a branch protection device and a zero-inrush-current thyristor composite switch.

[0106] In this embodiment, each phase-to-phase capacitor bank is provided with , and Three phase-to-phase capacitor branches with nominal capacity ratings.

[0107] Preferably, the interphase capacitor branches corresponding to the same nominal capacitance level in the three interphase capacitor groups AB, BC and CA are synchronously controlled according to the three-phase symmetrical coarse adjustment requirements, so as to reduce the introduction of new negative sequence components by the asymmetrical passive compensation itself.

[0108] The embodiment referred to as , and The nominal capacity level of the phase-to-phase capacitor branch is used to indicate the actual passive compensation of the system. The total passive compensation of the actual system is determined by summing the compensation amounts of each phase-to-phase capacitor branch that are currently in operation.

[0109] For the The theoretical compensation capacity of each phase-to-phase capacitor branch is: ; in, Indicates the first The reactive power compensation capacity of each phase-to-phase capacitor branch; Indicates the corresponding capacitance; This represents the effective value of the line voltage across the two ends of the phase-to-phase capacitor branch; Represent the angular frequency of the power grid, and satisfy: ; in, Indicates the power grid frequency.

[0110] The passive coarse adjustment branch of the multi-phase capacitor mainly undertakes the steady-state reactive power compensation base value under continuous imbalance. The negative sequence compensation, zero sequence compensation, fast dynamic compensation and the remaining compensation between discrete capacitor positions are continued to be undertaken by the four-bridge arm SVG active fast balancing branch.

[0111] 12. Steady-state compensation requirements and gear selection: The duration determination circuit outputs a continuous imbalance confirmation signal. ,and Subsequently, the passive coarse adjustment branch of the multi-phase capacitors is eligible for new switching; the edge intelligent main control unit further determines the capacity level or capacity combination of the phase capacitors to be put into operation based on the steady-state reactive power compensation requirements.

[0112] The edge intelligent main control unit calculates the total active power of the load. Total reactive power ,in: ; Let the target power factor be The corresponding target power factor angle is: ; The target steady-state reactive power compensation is: ; in, This represents the system's target steady-state reactive power compensation.

[0113] Let the total allowable compensation capacity set of the multi-phase inter-capacitor passive coarse adjustment branch be . The selected passive coarse adjustment compensation capacity is denoted as The amount shall be determined according to the principle of not exceeding the target steady-state reactive power compensation: ; therefore: ; The remaining compensation requirement is: ; in, This indicates the remaining reactive power compensation that will continue to be borne by the four-arm SVG active fast balancing branch.

[0114] By using the above-mentioned gear selection method, the phase-to-phase capacitor branch can avoid entering a state of obvious overcompensation in order to pursue the closest to the target steady-state reactive power compensation amount, and the continuous adjustable feature of the four-arm SVG active fast equalization branch can be used to make up for the remaining compensation amount between the discrete capacity levels of the phase-to-phase capacitor branch.

[0115] Thirteen, Uninterrupted handover of compensation: like Figure 8 As shown, the non-disruptive handover process of the compensation quantity includes the process of connecting the phase-to-phase capacitor branch and the process of disconnecting the phase-to-phase capacitor branch. Figure 8 (a) illustrates the compensation transfer relationship during the connection process of the interphase capacitor branch. Figure 8 (b) illustrates the compensation transfer relationship during the phase-to-phase capacitor branch exit process. The compensation transfer control unit is connected to the four-arm SVG active fast equalization branch and the multi-stage phase-to-phase capacitor passive coarse adjustment branch, respectively.

[0116] In this embodiment, the phase-to-phase capacitors are discrete switching elements, and the capacitance itself does not change continuously. The continuous adjustment in the seamless handover mainly occurs on the SVG compensation command side.

[0117] Each phase-to-phase capacitor branch is equipped with a branch current sensor. The detection output terminal of the branch current sensor is connected to the edge intelligent main control unit. The edge intelligent main control unit calculates the actual capacitive compensation amount borne by the phase-to-phase capacitor branch based on the corresponding phase-to-phase voltage and the actual current of the phase-to-phase capacitor branch.

[0118] To avoid ambiguity caused by different reactive power symbols, this embodiment stipulates that the capacitive compensation capacity provided to the load shall be a positive value.

[0119] For the XY phase-to-phase capacitor branch: ; in, This indicates the amount of capacitive reactive power compensation actually undertaken by the XY phase-to-phase capacitor branch; This indicates the effective value of the corresponding phase-to-phase voltage; This indicates the effective value of the current in the corresponding capacitor branch; This represents the phase difference between the phase-to-phase voltage and the fundamental current of the capacitor branch.

[0120] The sum of the compensation amounts actually borne by all the interphase capacitor branches is denoted as: ; The reactive power compensation command for the four-arm SVG active fast equalization branch is determined according to the following formula: ; in, Indicates time SVG reactive power compensation instructions; Indicates time The target steady-state reactive power compensation; Indicates time The sum of the actual capacitive compensation amount undertaken by each phase-to-phase capacitor branch actually put into operation.

[0121] thus: The total compensation should be kept as continuous as possible during the connection and disconnection of the capacitor branch.

[0122] Phase-to-phase capacitor branch connection process: like Figure 8 As shown in (a), during the connection of the interphase capacitor branch, the target steady-state reactive power compensation is... The value remains essentially unchanged. Let the equivalent compensation capacity of the interphase capacitor branch to be implemented be... ,in, This indicates the start time of compensation handover, that is, the moment when the compensation handover control unit begins to adjust the SVG reactive power compensation command of the four-arm SVG active fast equalization branch and prepares to engage the phase-to-phase capacitor branch. This indicates the moment when the actual capacitive compensation amount reaches the corresponding activation state after the phase-to-phase capacitor branch is activated, and the handover of this compensation amount is completed. and During the corresponding handover process, as the actual capacitive compensation of the phase-to-phase capacitor branch is gradually established, the active fast equalization branch of the four-arm SVG reduces the reactive power compensation command of the SVG accordingly, so that the sum of the reactive power compensation of the SVG and the actual capacitive compensation of the phase-to-phase capacitor branch is kept as consistent as possible with the target steady-state reactive power compensation.

[0123] Let the preset handover time be Define the SVG handover adjustment factor: ; in, This indicates the progress of the handover and adjustment of SVG compensation instructions; Indicates the variable Limited to Within the range.

[0124] The feedforward SVG compensation instruction for the input process is: ; in, This indicates the SVG reactive power compensation command before the start of the compensation handover.

[0125] Here This only indicates the adjustment process of the SVG compensation command, and does not mean that the interphase capacitance increases continuously from zero to... .

[0126] The phase-to-phase capacitors are still discretely switched on by the zero-current thyristor composite switch at the zero-crossing moment when the switching conditions are met.

[0127] After the interphase capacitors are connected, the results are based on actual testing: Real-time utilization: ; Feedback correction is applied to the SVG feedforward output.

[0128] This forms a two-layered connection: "feedforward prediction of the capacity to be put into use + feedback correction of the actual compensation amount of the capacitor".

[0129] Interphase capacitor branch disconnection process: like Figure 8 As shown in (b), during the phase-to-phase capacitor branch disconnection process, the target steady-state reactive power compensation is... The basic structure remains unchanged. When a phase-to-phase capacitor branch needs to be disconnected, the four-arm SVG active fast equalization branch first enters a short-term pre-management state. Before the actual compensation amount of the phase-to-phase capacitor branch is disconnected, the SVG reactive power compensation command is increased, so that the SVG pre-bears the compensation amount corresponding to the phase-to-phase capacitor branch to be disconnected.

[0130] Figure 8 In (b), Indicates the start time of SVG pre-takeover. Indicates the completion time of the phase-to-phase capacitor branch exit; in to During the corresponding handover phase, the four-arm SVG active fast equalization branch gradually establishes the compensation amount corresponding to the phase-to-phase capacitor branch to be withdrawn, so as to reduce the compensation gap caused by the withdrawal of the phase-to-phase capacitor branch.

[0131] ; Then, the corresponding capacitor branch is controlled to exit at an appropriate zero-crossing moment.

[0132] Within a short transition window near the point where the capacitor branch exits, the SVG establishes an output corresponding to the soon-to-disappear capacitor compensation amount; after the interphase capacitor exits, it then follows: ; Make real-time corrections.

[0133] This reduces the compensation gap caused by the direct withdrawal of the capacitor and avoids the SVG and the capacitor repeatedly bearing the same compensation amount for a long period of time.

[0134] XIV. Multi-path branch power distribution unit: The multi-circuit power distribution unit is located at the bottom of the cabinet.

[0135] Each branch circuit includes at least a branch circuit breaker, a branch residual current device, and an output terminal.

[0136] Single-phase construction equipment can be connected to AN, BN, or CN circuits, while three-phase construction equipment can be connected to ABC three-phase circuits.

[0137] In one implementation, eight branch outputs can be set, or the number of branch outputs can be increased or decreased according to the actual needs of the construction site.

[0138] 15. Graded leakage current protection and residual current detection: The graded leakage current protection unit is a complete functional unit, including a main circuit residual current detection component and multiple branch circuit residual current detection components corresponding to each branch circuit.

[0139] The main circuit residual current detection component includes a zero-sequence current transformer installed on the main circuit. The four main circuit working conductors, namely phase A, phase B, phase C, and line N, all pass through the zero-sequence current transformer, while the PE protection conductor does not pass through the zero-sequence current transformer.

[0140] Each branch residual current detection component includes a zero-sequence current transformer installed on the corresponding branch. All working conductors of the corresponding branch pass through the corresponding zero-sequence current transformer, while the PE protection conductor does not pass through.

[0141] For a smart distribution cabinet with 8 outputs, the graded leakage current protection unit includes one main circuit residual current detection position and eight branch circuit residual current detection positions.

[0142] The detection output terminals of each zero-sequence current transformer are connected to the edge intelligent main control unit.

[0143] In this embodiment, the "zero-sequence current" used for three-phase balance calculation and the "residual current" used for leakage protection belong to different detection objects.

[0144] For a three-phase four-wire protection circuit: ; Under normal circumstances: ; Even if there is a normal operating current on the N line caused by the imbalance of the three-phase load, as long as the operating current returns normally through the A, B, C and N lines, the residual current will still be close to zero.

[0145] When a ground leak occurs: ; Therefore, the graded leakage protection unit will not directly identify the normal neutral line operating current caused by three-phase imbalance as leakage current.

[0146] Let the first The effective value of the residual current in the circuit is .when: When: Output leakage current warning; when: At that time, corresponding protective actions will be executed. Among them, Indicates the leakage current warning threshold; This indicates the threshold for leakage current protection to operate, and it must satisfy the following conditions: .

[0147] XVI. Temperature monitoring and remote communication: The temperature monitoring and protection unit includes multiple temperature sensors, which are respectively located near the SVG power module, near the multi-phase capacitors, near the thyristor composite switch, the N busbar, and in the cabinet environment area.

[0148] Specifically, an independent temperature sensor can be installed on the N-line busbar.

[0149] Let the effective value of the N-line current be... The N-line current warning threshold is The temperature of the N-line busbar is The temperature warning threshold for the N-line is .when: ,and: When the set time is reached, the edge intelligent main control unit outputs a combined overcurrent and overheat alarm for the N-line.

[0150] When the SVG power module, multi-phase capacitors, or thyristor composite switches reach the corresponding protection temperature, the edge intelligent main control unit can perform SVG current limiting, prohibit the addition of new capacitor switching, capacitor range exit, or hierarchical three-phase equalization control module shutdown protection.

[0151] The remote communication alarm unit is installed in the low-voltage area of ​​the cabinet and is connected to the edge intelligent main control unit.

[0152] The remote communication alarm unit can use 4G, 5G or other wireless communication modules and can send three-phase current, negative sequence current imbalance, zero sequence current ratio, neutral line current, SVG compensation status, capacitor switching position, SVG temperature, capacitor temperature, neutral line temperature, leakage status of the main circuit and each branch circuit, and fault information to the construction management terminal.

[0153] The working principle of this temporary intelligent power distribution cabinet with layered three-phase balancing hardware on the construction site is as follows: like Figure 7 As shown, the present invention operates according to the control process of three-phase unbalance amplitude identification, RS state maintenance, duration confirmation, and active-passive hierarchical compensation.

[0154] construction site The three-phase four-wire power supply enters the A-phase busbar, B-phase busbar, C-phase busbar and N-line busbar through the main incoming line protection unit, and then supplies power to the construction equipment through the multi-circuit distribution unit.

[0155] The main circuit three-phase acquisition unit continuously acquires three-phase voltage, three-phase current and neutral line current.

[0156] The edge intelligent main control unit calculates the imbalance of positive-sequence current, negative-sequence current, zero-sequence current, and negative-sequence current. and will Convert to analog quantity Input impact load two-dimensional hardware identification unit.

[0157] 1. Normal state: When the RS flip-flop is in the reset state, that is, the condition has not yet been met: The positioning event, or the imbalance that occurred previously, has decreased to: When the reset is completed, the system is in normal condition.

[0158] The four-arm SVG active fast equalization branch maintains a low-amplitude adjustment based on the remaining dynamic compensation requirements, while the multi-stage phase-to-phase capacitor passive coarse adjustment branch maintains the current stable setting.

[0159] 2. Short-term shocks or unconfirmed imbalances: When the welding machine starts an arc, the motor starts, or multiple loads are connected simultaneously: When the first comparator is activated, it immediately sets the RS flip-flop. One output of the RS flip-flop immediately enables the four-arm SVG active fast equalization branch, enabling it to quickly compensate for negative sequence, zero sequence, and dynamic reactive components; the other output simultaneously starts the duration determination.

[0160] The time during which the RS flip-flop remains in the set state satisfies At that time, the signal for confirmation of continuous imbalance is: The passive coarse adjustment branch of the multi-phase capacitor maintains the newly added switching lockout.

[0161] If during this period: The RS flip-flop remains set, and the four-arm SVG continues to compensate rapidly, with a continuous set time. Continue to accumulate.

[0162] if: Then the second comparator resets the RS flip-flop, the RC delay capacitor discharges rapidly, and the cumulative set time for this continuous operation is cleared to zero.

[0163] Therefore, short-duration impact loads such as short-term arc ignition of welding machines and motor start-up can be preferentially borne by the four-bridge SVG active fast balancing branch, without directly causing new investment in the interphase capacitor branch.

[0164] 3. Persistent state of imbalance: After the RS flip-flop is set, as long as it is not due to: The reset, and the RS flip-flop remains in the set state for the duration of: The duration determination circuit outputs a continuous imbalance confirmation signal: This unlocks the new switching blocking of the multi-phase-to-phase capacitor passive coarse adjustment branch, enabling it to switch on and off. The edge intelligent main control unit selects the appropriate capacity level or combination for passive coarse adjustment based on the steady-state reactive power compensation requirements. The multi-phase-to-phase capacitor passive coarse adjustment branch undertakes the continuous steady-state reactive power compensation base value, while the four-arm SVG active fast balancing branch continues to undertake negative sequence compensation, zero sequence compensation, capacitor discrete range residual compensation, and fast dynamic compensation.

[0165] 4. Handover of active-to-passive compensation quantities: When the interphase capacitors are connected, the four-arm SVG performs feedforward unloading based on the capacity to be connected, and then adjusts the output according to the actual compensation of the interphase capacitors after the connection is established. Provide feedback and make corrections.

[0166] When the phase-to-phase capacitors are deactivated, the four-arm SVG first enters a short-time pre-control state, and then controls the corresponding phase-to-phase capacitors to deactivate at an appropriate zero-crossing moment.

[0167] Therefore: Try to maintain continuity during the capacitor connection and disconnection process.

[0168] 5. Recovering Status: when: When the time is reached, the RS trigger is reset, and the duration determination is cleared to zero.

[0169] The four-arm SVG continues to compensate for the remaining negative sequence, zero sequence, and dynamic compensation needs. The multi-stage interphase capacitor passive coarse adjustment branch maintains the existing stage according to the new steady-state reactive power demand or exits step by step according to the non-disruptive exit method.

[0170] The first core point of this embodiment is the construction of a two-dimensional hardware identification chain for impact loads, consisting of "dual threshold amplitude judgment + RS state maintenance + duration confirmation".

[0171] The state relationship is as follows: ; ; .

[0172] After the RS flip-flop is set, the duration for which it remains in the set state is further determined. Has the set duration been reached? .when: At that time, the four-bridge arm SVG active fast equalization branch performs fast compensation, and the multi-stage phase-to-phase capacitor passive coarse adjustment branch maintains the newly added switching blocking; when: When the duration determination circuit outputs a continuous imbalance confirmation signal, it allows the passive coarse adjustment branch of the multi-phase capacitor to intervene in the steady-state coarse adjustment.

[0173] This control method can maintain the fast response capability of the four-arm SVG while reducing the frequent switching of phase capacitor branches caused by short-term impacts such as welding machine arc initiation and motor start-up.

[0174] The second key point is the clear layering of compensation tasks between the four-arm SVG and the multi-stage phase capacitors.

[0175] The multi-stage interphase capacitors mainly provide the steady-state reactive power compensation base value under continuous imbalance conditions; the four-arm SVG mainly provides short-time impact compensation, negative sequence compensation, zero sequence compensation, capacitor discrete stage residual compensation, and fast dynamic compensation.

[0176] In particular, by connecting the N-line busbar through the neutral line bridge arm, an independent path is provided for the zero-sequence compensation current, making it more suitable for three-phase four-wire temporary power distribution systems where a large number of single-phase construction loads are randomly connected.

[0177] The third core aspect of this invention lies in establishing a feedback-based, disturbance-free handover relationship between discrete capacitors and continuous SVG (Static Var Generator): ; This control relationship does not assume that the interphase capacitance can continuously change its capacity. Instead, it detects the actual amount of compensation established or lost by the interphase capacitance and then adjusts the amount of compensation undertaken by the SVG synchronously.

[0178] Therefore, the SVG reduces the corresponding compensation amount based on the actual increase in the interphase capacitor compensation. When the interphase capacitor is removed, resulting in a decrease in the actual compensation amount, the SVG will take over the management to reduce the repeated compensation, compensation gap, and secondary fluctuations in three-phase current caused by direct capacitor switching.

[0179] In summary, the following is formed: The complete technology chain.

[0180] Compared with general compensation methods that simply combine active compensation and capacitor compensation, this technology chain differs not only in the composition of compensation devices, but also in the hardware determination method for the eligibility of multi-stage phase-to-phase capacitor passive coarse adjustment branches, the division of compensation responsibilities between the four-arm SVG active fast equalization branch and the multi-stage phase-to-phase capacitor passive coarse adjustment branch, and the handover control method based on the actual compensation amount during the discrete switching of phase-to-phase capacitor branches.

[0181] Application examples: like Figure 9 As shown, to further illustrate the specific application of the present invention under temporary power supply conditions at a construction site, the above-mentioned temporary intelligent power distribution cabinet with layered three-phase balancing hardware was applied to a three-phase four-wire temporary power supply system of a building construction project and configured as a temporary 8-channel intelligent power distribution cabinet.

[0182] The cabinet adopts The cabinet features a double-layer steel plate structure, with a layered three-phase balanced control area equipped with an independent balanced compartment featuring a sealed dustproof structure. The bottom of the cabinet is fitted with a drainage channel and four sets of self-locking casters.

[0183] The three-phase acquisition unit uses three-phase current transformers to acquire the A, B, and C phase currents of the main circuit. The current transformer ratio is... .

[0184] The rated compensation current of the four-arm SVG active fast equalization branch is: The dynamic response time is .

[0185] Multi-stage interphase capacitor passive coarse adjustment branch setting , and Three capacity levels, each phase-to-phase capacitor branch is equipped with a zero-inrush-current thyristor composite switch.

[0186] The impact load dual-dimensional hardware identification unit uses an LM393 dual voltage comparator to compare the action threshold and recovery threshold, and uses RS state hold logic and an NE555 timer in conjunction with an RC delay network to determine the duration.

[0187] The first action threshold is: ; The second recovery threshold is: ; The duration is set as follows: ; in, This indicates the set duration required for the RS trigger to remain in the set state to meet the continuous imbalance confirmation condition.

[0188] when: When the RS trigger is set, the four-bridge arm SVG quickly engages and begins to accumulate duration.

[0189] when: If the RS flip-flop has already been set, it will remain set and continue to accumulate the duration.

[0190] Only when: The RS flip-flop is reset only when the current duration is cleared.

[0191] When the RS flip-flop is continuously held at the set position until When the duration determination circuit outputs a continuous imbalance confirmation signal, it allows the passive coarse adjustment branch of the multi-phase capacitor to adjust the capacitor level according to the steady-state compensation requirements.

[0192] The over-temperature protection threshold of the layered three-phase equalization control module is set to... When the detected temperature reaches or exceeds When necessary, the edge intelligent main control unit will implement SVG current limiting, prohibit the addition of new capacitors, exit the capacitor level, or shut down the layered three-phase equalization control module for protection.

[0193] The target for negative sequence current imbalance control is set as follows: ; Records of 30 consecutive days of operation at the site show that, prior to the adoption of the distribution cabinet of this invention, the negative sequence current imbalance of traditional temporary distribution cabinets without three-phase balancing function was significantly reduced. Usually The maximum current of the N line reaches After adopting the distribution cabinet of this invention, under steady-state operating conditions, the negative sequence current imbalance is reduced. Stable at The maximum current of the N-line decreased to .

[0194] To further evaluate the compensation effect of the multi-stage passive coarse adjustment method compared to the single-stage large-capacity direct switching method, a comparative experiment was conducted under the same load conditions. The negative sequence current imbalance was measured in the initial experimental state. Approximately Subsequently, the negative sequence current imbalance is caused by load changes. Step up to .

[0195] The first control method uses multiple phase-to-phase capacitors, adjusting them in stages from small to large capacity according to compensation requirements. The second control method uses a single large-capacity phase-to-phase capacitor, applied all at once. Test results show that the maximum overshoot of the multi-stage tiered adjustment method is 2.3%, while the maximum overshoot of the single-stage large-capacity capacitor application method is 7.8%, with a difference of 5.5% between the two methods. These results indicate that under the same load step conditions in this application example, multi-stage tiered coarse adjustment can reduce the compensation step caused by a single large-capacity capacitor application.

[0196] Therefore, this invention does not simply aim to reduce the number of capacitor actions during a single steady-state adjustment process. Instead, it first avoids meaningless capacitor switching caused by a large number of short-term impacts through two-dimensional hardware identification of impact loads. After confirming the formation of a continuous imbalance, it then uses phase-to-phase capacitors of different capacity levels for steady-state stratified coarse adjustment. The four-arm SVG handles short-term impacts, negative sequence, zero sequence, and residual dynamic compensation. At the same time, it performs non-disruptive handover of compensation during the phase-to-phase capacitor connection and disconnection process, thereby taking into account the rapid response to short-term impacts, steady-state compensation for continuous imbalances, and the smoothness of the capacitor switching process.

[0197] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A temporary intelligent power distribution cabinet for construction sites with layered three-phase balancing hardware, comprising a mobile protective cabinet for construction sites, a main incoming line protection unit, a main three-phase acquisition unit, a multi-path branch power distribution unit, and an edge intelligent main control unit, characterized in that: It also includes a two-dimensional hardware identification unit for impact loads and a layered three-phase balance control module; The output side of the main line incoming protection unit is connected to the A-phase busbar, B-phase busbar, C-phase busbar and N-line busbar respectively. The main three-phase acquisition unit is set on the output side of the main line incoming protection unit to acquire the voltage and current of A-phase, B-phase, C-phase and N-line current, and is connected to the edge intelligent main control unit. The impact load dual-dimensional hardware identification unit includes a first comparator, a second comparator, an RS flip-flop, and a duration determination circuit. The first comparator is used to output a set signal to the set terminal of the RS flip-flop when the negative sequence current imbalance reaches the first action threshold. The second comparator adopts the opposite comparison polarity to the first comparator and is used to output a reset signal to the reset terminal of the RS flip-flop when the negative sequence current imbalance drops to the second recovery threshold. The second recovery threshold is lower than the first action threshold. The layered three-phase equalization control module includes a four-arm SVG active fast equalization branch, a multi-stage phase-to-phase capacitor passive coarse adjustment branch, and a compensation quantity disturbance-free transfer control unit. The AC side of the four-arm SVG active fast equalization branch is connected to the A-phase busbar, B-phase busbar, C-phase busbar, and N-line busbar, respectively. The multi-stage phase-to-phase capacitor passive coarse adjustment branch is connected between the A-phase busbar, B-phase busbar, and C-phase busbar. The set output of the RS flip-flop forms two control paths. The first path is connected to the fast compensation enable terminal of the four-bridge arm SVG active fast equalization branch, and the second path is connected to the switching enable terminal of the multi-stage phase-to-phase capacitor passive coarse adjustment branch via the duration determination circuit. The duration determination circuit determines the duration for which the RS flip-flop is continuously set. If the continuous set time of the RS flip-flop has not reached the set duration, the new switching lockout of the multi-stage phase-to-phase capacitor passive coarse adjustment branch is maintained. After the continuous set time of the RS flip-flop has reached the set duration, the new switching lockout of the multi-stage phase-to-phase capacitor passive coarse adjustment branch is released, and the duration determination restarts after the RS flip-flop is reset. Each phase-to-phase capacitor branch of the multi-stage phase-to-phase capacitor passive coarse adjustment branch is equipped with a branch current sensor. The detection output terminal of the branch current sensor is connected to the edge intelligent main control unit. The edge intelligent main control unit determines the actual capacitive compensation amount undertaken by the phase-to-phase capacitor branch based on the phase-to-phase voltage and the actual current of the phase-to-phase capacitor branch. The compensation quantity seamless handover control unit is connected to the four-arm SVG active fast balancing branch and the multi-stage phase-to-phase capacitor passive coarse adjustment branch, respectively. It adjusts the compensation output of the four-arm SVG active fast balancing branch according to the actual capacitive compensation amount established or disappeared during the phase-to-phase capacitor connection or disconnection. When the phase-to-phase capacitor is connected, the compensation output of the four-arm SVG active fast balancing branch is reduced accordingly. When the phase-to-phase capacitor is disconnected, the four-arm SVG active fast balancing branch takes over the capacitor compensation amount to be disappeared.

2. The temporary intelligent power distribution cabinet for construction sites with layered three-phase balancing hardware according to claim 1, characterized in that: The interior of the mobile protective cabinet at the construction site is equipped with a main inlet and acquisition area, a layered three-phase balanced control area, and a branch output area along the height direction. The main line incoming protection unit and the main line three-phase acquisition unit are installed in the main line incoming and acquisition area. The four-bridge arm SVG active fast balancing branch and the multi-stage phase-to-phase capacitor passive coarse adjustment branch are installed in the layered three-phase balancing control area. The multi-circuit branch power distribution unit is installed in the branch output area. The three-phase balanced control area is equipped with an independent balanced compartment. The four-bridge SVG active fast balanced branch and the multi-stage phase-to-phase capacitor passive coarse adjustment branch are set in the independent balanced compartment. The mobile protective cabinet for construction sites is equipped with a waterproof and dustproof door, and the bottom of the cabinet is equipped with a drainage channel and self-locking casters or adjustable feet.

3. The temporary intelligent power distribution cabinet for construction sites with layered three-phase balancing hardware according to claim 1, characterized in that: The three-phase acquisition unit includes three phase current sensors respectively installed on the A-phase, B-phase and C-phase main conductors, an N-line current sensor installed on the N-line main conductor, and voltage sampling terminals respectively connected to the A-phase busbar, B-phase busbar and C-phase busbar; The edge intelligent master control unit performs symmetrical component decomposition based on the fundamental current phasors of phases A, B, and C. The positive-sequence current phasors, negative-sequence current phasors, and zero-sequence current phasors are determined according to the following formulas: ； ； ； in, , and These represent the fundamental current phasors of phases A, B, and C, respectively. Represents the positive sequence current phasor; Represents the negative sequence current phasor; Represents the zero-sequence current phasor; express Rotation operator, satisfying: ； in, Represents the imaginary unit; Negative sequence current unbalance is denoted as And determine according to the following formula: ； The edge intelligent main control unit converts the negative sequence current imbalance through a digital-to-analog converter circuit. Convert to unbalanced analog voltage: ； in, This represents the analog voltage representing the unbalance input to the first and second comparators, respectively. This represents the proportional conversion gain between the negative sequence current imbalance and the unbalanced analog voltage; the digital-to-analog converter circuit is either a DAC circuit or consists of a PWM output terminal and a low-pass filter circuit.

4. The temporary intelligent power distribution cabinet for construction sites with layered three-phase balancing hardware according to claim 3, characterized in that: Let the first action threshold be The second recovery threshold is And satisfy: ; The analog reference voltage corresponding to the first action threshold is: ; The analog reference voltage corresponding to the second recovery threshold is: ; The first comparator is in The set signal is output to the set terminal of the RS flip-flop; The second comparator is in The timer outputs a reset signal to the reset terminal of the RS flip-flop; Let the logic state of the output of the RS flip-flop be... ,but: hour: ; hour: ; when hour: ; in, Indicates the current state of the RS trigger. This indicates the state of the RS trigger before the current time.

5. The temporary intelligent power distribution cabinet for construction sites with layered three-phase balancing hardware according to claim 4, characterized in that: The duration determination circuit includes an RC integral delay branch, a threshold comparison section, and a discharge reset branch. The RC integral delay branch is connected between the set output of the RS flip-flop and the switching enable terminal of the passive coarse adjustment branch of the multi-stage phase-to-phase capacitor. When the RS flip-flop remains in the set state, the capacitor voltage in the RC integral delay branch changes according to the following formula: ； when When the threshold comparison section outputs a continuous imbalance confirmation signal, the corresponding set duration is: ； in, This indicates that the continuous set time of the RS flip-flop is... The capacitor voltage of the RC integral delay branch; This represents the charging voltage of the RC integral delay branch; Indicates the delay resistor; Indicates the delay capacitor; This indicates the trigger voltage for confirming continuous imbalance; This indicates the set duration that distinguishes between short-term shock imbalance and sustained imbalance; When the RS flip-flop receives a reset signal, the discharge reset branch discharges the delay capacitor and clears the current continuous set time. The threshold comparison section is composed of the threshold comparison structure inside the NE555 timer, or it is composed of an independent threshold comparator.

6. The temporary intelligent power distribution cabinet for construction sites with layered three-phase balancing hardware according to claim 1, characterized in that: The four-arm SVG active fast equalization branch includes the A-phase bridge arm, B-phase bridge arm, C-phase bridge arm, neutral line bridge arm, DC bus capacitor, AC side filter inductor, power switching devices, power switch drive circuit and SVG controller. Phase A arm, phase B arm, and phase C arm are connected to phase A busbar, phase B busbar, and phase C busbar respectively via corresponding AC side filter inductors; the neutral arm is connected to the N busbar. The SVG controller generates A-phase, B-phase, C-phase, and neutral line compensation current commands based on the three-phase load current, where: ； ； ； ； in, , , These represent the instantaneous load currents of phases A, B, and C, respectively. , , These represent the expected instantaneous currents on the power supply side for phases A, B, and C, respectively. , , These represent the compensation current commands for phase A, phase B, and phase C bridge arms, respectively. This indicates the compensation current command for the neutral line arm; The four-arm SVG active fast equalization branch is configured to undertake short-time impulse compensation, negative sequence current compensation, zero sequence current compensation, and residual dynamic compensation after the switching of the multi-stage phase-to-phase capacitor passive coarse adjustment branch.

7. The temporary intelligent power distribution cabinet for construction sites with layered three-phase balancing hardware according to claim 1, characterized in that: The multi-stage phase-to-phase capacitor passive coarse adjustment branch includes the AB phase-to-phase capacitor group, the BC phase-to-phase capacitor group, and the CA phase-to-phase capacitor group. The AB phase-to-phase capacitor bank is connected between the A phase busbar and the B phase busbar, the BC phase-to-phase capacitor bank is connected between the B phase busbar and the C phase busbar, and the CA phase-to-phase capacitor bank is connected between the C phase busbar and the A phase busbar. Each phase-to-phase capacitor bank includes multiple phase-to-phase capacitor branches with different capacities that can be switched independently. Each phase-to-phase capacitor branch is connected in series with a branch protection device and a zero-inrush-current thyristor composite switch. Each phase-to-phase capacitor bank has , and Three phase-to-phase capacitor branches with nominal capacitance levels; The interphase capacitor branches corresponding to the same nominal capacity level in the AB, BC, and CA interphase capacitor groups can be synchronously controlled according to the three-phase symmetrical coarse adjustment requirements. The multi-stage passive coarse adjustment branches of the interphase capacitors are used to bear the steady-state reactive power compensation base value under continuous imbalance conditions.

8. The temporary intelligent power distribution cabinet for construction sites with layered three-phase balancing hardware according to claim 7, characterized in that: The edge intelligent main control unit is based on the total active power of the load. Total reactive power of the load and target power factor Determine the target steady-state reactive power compensation amount: ； in: ； This represents the target steady-state reactive power compensation amount; This represents the total active power of the load; This indicates the total reactive power of the load; Indicates the target power factor; Indicates the target power factor angle; Let the total allowable compensation capacity set of the multi-phase inter-capacitor passive coarse adjustment branch be . Selected passive coarse adjustment compensation capacity Determined according to the following formula: ； make: ； The remaining reactive power compensation requirement is: ； in, It is handled by the four-bridge arm SVG active fast equalization branch.

9. The temporary intelligent power distribution cabinet for construction sites with layered three-phase balancing hardware according to claim 8, characterized in that: Each phase-to-phase capacitor branch is equipped with a branch current sensor. The detection output terminal of the branch current sensor is connected to the edge intelligent main control unit. The edge intelligent main control unit determines the actual capacitive compensation amount of the corresponding phase-to-phase capacitor branch based on the phase-to-phase voltage and the actual current of the phase-to-phase capacitor branch. for For interphase capacitor branches, the actual capacitive compensation amount is determined according to the following formula: ； in, express Actual capacitive compensation amount for interphase capacitor branches; express Effective value of phase-to-phase voltage; express Effective value of interphase capacitor branch current; express The phase difference between the phase-to-phase voltage and the fundamental current of the phase-to-phase capacitor branch; The sum of the capacitive compensation amounts of each phase-to-phase capacitor branch actually implemented is denoted as: The compensation amount seamless handover control unit determines the residual reactive power compensation command of the four-arm SVG active fast equalization branch according to the following formula: ； in, Indicates time Reactive power compensation command for the four-arm SVG active fast equalization branch; Indicates time The target steady-state reactive power compensation; Indicates time The actual capacitive compensation amount undertaken by the passive coarse adjustment branch of the multi-phase capacitor; During the connection or disconnection of phase-to-phase capacitors, the transfer factor is determined according to the following formula: ； in, Indicates the start time of the compensation handover; Indicates the preset handover time; Indicates the variable Limited to to Amplitude limiting function within the range; When the phase-to-phase capacitor is engaged, the feedforward handover command of the four-arm SVG active fast equalization branch satisfies: ； When the interphase capacitors are deactivated, the feedforward handover command of the four-arm SVG active fast equalization branch satisfies: ； in, This indicates the feedforward handover command for the four-arm SVG active fast equalization branch; This indicates the SVG reactive power compensation command prior to the start of the handover. This indicates the compensation capacity corresponding to the phase-to-phase capacitors to be put into or taken out. After the interphase capacitors are actually connected or disconnected, then according to Feedback correction is performed on the compensation output of the active fast equalization branch of the four-bridge arm SVG.

10. The temporary intelligent power distribution cabinet for construction sites with layered three-phase balancing hardware according to claim 1, characterized in that: It also includes a graded leakage current protection unit, a temperature monitoring and protection unit, and a remote communication alarm unit; The graded leakage current protection unit includes a main circuit residual current detection component and multiple branch circuit residual current detection components corresponding to each branch of the multi-circuit power distribution unit. The main circuit residual current detection component includes a zero-sequence current transformer installed in the main circuit. The four main circuit working conductors, A-phase, B-phase, C-phase and N-line, all pass through the main circuit zero-sequence current transformer, while the PE protection conductor does not pass through. Each branch circuit residual current detection component includes a zero-sequence current transformer installed in the corresponding branch circuit. The working conductors of each branch circuit all pass through the corresponding zero-sequence current transformer. The temperature monitoring and protection unit includes multiple temperature sensors respectively located in the four-bridge arm SVG active fast equalization branch, the multi-stage phase-to-phase capacitor passive coarse adjustment branch, the N-line busbar, and inside the cabinet. The edge intelligent main control unit is connected to each zero-sequence current transformer, each temperature sensor and remote communication alarm unit, and outputs early warning signals or protection control signals based on the detected residual current, neutral line current and temperature. The remote communication alarm unit includes a wireless communication module for transmitting information on three-phase current, negative sequence current imbalance, neutral line current, four-arm SVG compensation status, capacitor level, temperature status, and leakage status.

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