Rapid phase-change switch device for three-phase imbalance treatment
By combining solid-state intelligent phase commutation switch and stationary synchronous compensator in the three-phase imbalance management fast phase commutation switch device, automatic balance distribution of three-phase loads and online self-learning control are achieved, and transformer overload caused by three-phase imbalance is solved. and voltage instability issues improve power quality and the service life of distribution transformers.
Patent Information
- Application Number
- CN202411283661.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-13
- Publication Date
- 2025-01-10
AI Technical Summary
The existing technology cannot effectively solve the problem of three-phase imbalance, resulting in overload operation of transformers, increased power loss, unstable voltage, affecting the quality of power, and low and unsustainable phase regulation efficiency.
A three-phase imbalance management fast phase exchange switch device is designed, including the main controller and the intelligent phase exchange switch box, which adopts solid-state intelligent phase exchange switch and a stationary synchronous compensator to automatically generate the optimal load by collecting load current data in real time. Configuration instructions to realize automatic balanced distribution of loads, and use the online self-learning control system to optimize phase commutation operations to reduce three-phase imbalance.
The stability of load power supply is achieved, the line loss and tripping outage rate is reduced, the life of the transformer is extended, the voltage quality and system voltage stability is improved, the distribution quality is improved, and the line loss of low-voltage distribution transformers is reduced.
Smart Images
Figure CN119298115A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of three-phase unbalance control, and in particular relates to a three-phase unbalance control fast phase-changing switch device. Background Art
[0002] Three-phase load balance is the basis of safe power supply. With the continuous increase in electricity demand, the three-phase imbalance problem of distribution transformers has become one of the common power quality problems in low-voltage distribution networks. The unreasonable distribution of three-phase loads makes the transformer in an asymmetric operating state, increasing the power loss of the distribution transformer and the power loss of the line, shortening the service life of the distribution transformer, and even causing the transformer to burn out; when the three-phase load is seriously asymmetric, the neutral point position will shift, the line voltage drop and power loss will increase greatly, and single-phase users connected to the heavy-load phase are prone to low voltage, dim lights, reduced electrical efficiency, and other problems; while users connected to the light-load phase are prone to low voltage, dim lights, reduced electrical efficiency, and other problems. Single-phase users of the phase are prone to high voltage, which may cause insulation breakdown of electrical appliances, shorten the service life of electrical appliances or damage electrical appliances. Therefore, only three-phase load balance can ensure the power quality of users. For three-phase unbalanced regulation, manual phase adjustment is often used. The efficiency of manual phase adjustment is low, and power outages need to be carried out in the substation area, affecting the electricity consumption of residential users. Moreover, due to the uncertainty of user electricity consumption, manual phase adjustment cannot be performed frequently, and the effect is very unsatisfactory. Therefore, it is very necessary to provide a three-phase unbalanced control fast phase-changing switch device that can improve voltage quality, stabilize system voltage, reduce line loss, and solve the problem of transformer overload operation. Summary of the invention
[0003] The purpose of the present invention is to overcome the deficiencies of the prior art and to provide a three-phase unbalanced control fast phase-changing switch device which can improve voltage quality, stabilize system voltage, reduce line loss and solve the problem of transformer overload operation.
[0004] The purpose of the present invention is achieved as follows: a three-phase unbalanced control fast phase-changing switch device, which includes a main controller and a plurality of intelligent phase-changing switch boxes and a main station. The intelligent phase-changing switch box includes a control platform for realizing comprehensive analysis of collected data and issuing optimal phase-changing operations and a phase-changing switch for realizing current data collection and phase-changing operations. The phase-changing switch is a solid-state intelligent phase-changing switch, including a three-phase solid-state switch, a current sensor, a DSP controller, a drive protection device and a communication device.
[0005] The solid-state intelligent phase-changing switch is connected to a three-phase power supply, adopts a three-phase input and single-phase output mode, connects a single-phase load to one phase of the three-phase power supply, and quickly switches the load between phases A, B, and C when necessary.
[0006] The three-phase solid-state switch is a semi-controlled solid-state switch, including an anti-parallel thyristor module and a magnetic latching relay, wherein the anti-parallel thyristor module is composed of two anti-parallel thyristors.
[0007] The main controller collects the load current of the substation in real time and uploads it to the main station cloud. The main station cloud automatically generates and sends the optimal three-phase load configuration instructions to the intelligent phase-changing switch box according to the capacity of the substation transformer and the severity of the imbalance, so that the load is distributed as evenly as possible to the three phases, reducing the three-phase imbalance; the intelligent phase-changing switch box receives the instructions issued by the main controller and implements intelligent phase-changing operations, and can give priority to adjusting the phase-changing switch closest to the extreme value of the line imbalance.
[0008] The three-phase unbalance control fast phase-changing switch device also includes a static synchronous compensator that is simultaneously incorporated into the distribution network with the intelligent phase-changing switch box to control the three-phase imbalance of the distribution network. The intelligent phase-changing switch makes a large adjustment to the three-phase imbalance, and then the imbalance in the line is controlled by the static synchronous compensator to minimize the three-phase imbalance as much as possible.
[0009] The static synchronous compensator adopts a STATCOM whose main circuit structure is a split capacitor topology structure.
[0010] A commutation control method for a three-phase unbalance management fast commutation switch device based on self-learning control is implemented by using the three-phase unbalance management fast commutation switch device as described above. The control method comprises the following steps:
[0011] Step 1: Calculate the average value k and maximum value I of the three-phase current of the branch according to the three-phase current of the branch max , minimum value I min , the phase corresponding to the maximum value, the phase corresponding to the minimum value, and the upper deviation value Δx;
[0012] Step 2: According to the phase corresponding to the maximum value obtained above, find the switches corresponding to the phase in the branch, and obtain their three-phase current values and switch addresses, and put them into two arrays;
[0013] Step 3: Calculate the three-phase unbalance;
[0014] Step 4: Subtract the upper deviation value from the current of the switch obtained in turn. If the difference is greater than the set threshold, save their difference and continue to poll other switches. If the current of the subsequent switch and the upper deviation value are greater than the threshold and the difference is less than the previously saved difference, replace them. After polling all branch switches, a switch can be selected.
[0015] Step 5: Find the switch whose current is closest to the upper deviation value through the above, then use the difference between the original deviation value and the current value of the switch as the new deviation value, and set the current value of the switch to the upper deviation value plus 1 (to ensure that it will not be re-read and selected during the next recursion);
[0016] Step 6: Return to step 4 and continue to poll all branch switches until the difference between the upper deviation value and all switch current values is less than the set threshold. Then the polling of the branch switches is completed, and the number of switches to be switched, the addresses of all switches, the current phase of the switches, and the phase to be switched to can be obtained.
[0017] Step 7: Starting from multi-objective optimization and adjustment, based on the data collected by the three-phase unbalanced fast-changing switch device and its own equipment status, an online self-learning control system is introduced to learn the content of the network, covering the status and information of the current transformer in the substation, the voltage and current of each branch, the status of each switch, the historical imbalance adjustment method and the characteristics of the historical load, to achieve autonomous control of the controller.
[0018] The calculation of the three-phase imbalance in step 3 is specifically as follows: each current collected by the phase-changing switch, I1,...,I n , the controller collects the total current at the distribution transformer outlet, and then sorts them by the total current of each phase, from large to small, they are x, y, z, and calculate the total average value: Δx=xk, Δy=yk, Δz=zk, wherein the upper deviation Δx is greater than zero, and the lower deviation Δz is less than zero.
[0019] The multi-objective optimization adjustment of the online self-learning control system in step 7 includes low imbalance and short imbalance time, few switching actions, long equipment life and no risk of permanent power outage.
[0020] Beneficial effects of the present invention: The present invention is a three-phase unbalanced fast phase-changing switch device. During use, the main controller of the present invention can collect the load current of the substation in real time, and automatically generate and send the optimal three-phase load configuration instruction according to the capacity of the substation transformer and the severity of the imbalance; the intelligent phase-changing switch box of the present invention receives the instruction issued by the main controller and realizes the intelligent phase-changing operation, and can preferentially adjust the phase-changing switch closest to the extreme value of the line imbalance; the present invention ensures that the on-load phase-changing does not interrupt the power supply, there is no voltage drop, no inrush current, and no phase short circuit risk, and the loss of the phase-changing switch itself should be small, and the phase-changing switch meets the setting of the phase-changing constraint reduction, ensuring flexible functions, achieving energy saving and loss reduction, improving the terminal voltage, and reducing the tripping and power outage rate, thereby improving the voltage quality, stabilizing the system voltage, improving the distribution quality, and improving the power use environment; it can reduce the substation line loss of the low-voltage distribution transformer, increase the power sales revenue of the power supply company, and at the same time solve the problems of transformer overload operation caused by three-phase imbalance, and extend the life of the transformer; the present invention has the advantages of improving voltage quality, stabilizing the system voltage, reducing line loss, and solving the problem of transformer overload operation. BRIEF DESCRIPTION OF THE DRAWINGS
[0021] Figure 1 It is a schematic diagram of the present invention.
[0022] Figure 2 It is the wiring diagram of the present invention.
[0023] Figure 3 It is a schematic diagram of the topological structure of the phase-changing switch box of the present invention.
[0024] Figure 4 It is a schematic diagram of the structure of the phase-changing switch box of the present invention.
[0025] Figure 5 It is a schematic diagram of the topological structure of the solid-state intelligent phase-changing switch of the present invention.
[0026] Figure 6 It is a structural schematic diagram of the solid-state intelligent phase-changing switch of the present invention.
[0027] Figure 7 It is the flow chart of the commutation instruction of the present invention.
[0028] Figure 8 It is a schematic diagram of the STATCOM split capacitor topology structure of the present invention.
[0029] Fig. 9 It is the working principle diagram of STATCOM of the present invention.
[0030] Fig.10 This is a block diagram of the online self-learning control principle of the present invention.
[0031] Fig.11 This is a diagram of the three-phase unbalanced commutation switch control method of the present invention. DETAILED DESCRIPTION
[0032] The present invention will be further described below in conjunction with the accompanying drawings.
[0033] Example 1
[0034] like Figure 1-11 As shown, a three-phase unbalanced control fast phase-changing switch device includes a main controller and several intelligent phase-changing switch boxes and a main station. The intelligent phase-changing switch box includes a control platform for realizing comprehensive analysis of collected data and issuing optimal phase-changing operations and a phase-changing switch for realizing current data collection and phase-changing operations. Figure 4 As shown, since the data analysis and command issuance of the control platform are based on local information, the communication link can be omitted, which greatly improves the real-time and reliability of three-phase unbalanced control; the phase-changing switch is a solid-state intelligent phase-changing switch, including a three-phase solid-state switch, a current sensor, a DSP controller, a drive protection device and a communication device.
[0035] The solid-state intelligent phase-changing switch is connected to a three-phase power supply, adopts a three-phase input and single-phase output mode, connects a single-phase load to one phase of the three-phase power supply, and quickly switches the load between phases A, B, and C when necessary.
[0036] The three-phase solid-state switch adopts a semi-controlled solid-state switch, including an anti-parallel thyristor module (that is, the semi-controlled solid-state switch uses two thyristors, and the two thyristors are connected in anti-parallel, and the conduction characteristics of the thyristor are utilized. Only when the anode and the cathode are subjected to a forward voltage drop, a positive trigger pulse is applied to the gate to trigger conduction; when shutting down, only the trigger pulse of the gate needs to be turned off, and the thyristor will be naturally shut down in a short time by utilizing the zero-crossing shutdown characteristics of the thyristor, so as to realize forward and reverse conduction) and a magnetic latching relay, wherein the anti-parallel thyristor module is composed of two anti-parallel thyristors; Figure 6 It is the structural diagram of a three-phase solid-state switch, where VS is an anti-parallel thyristor module, each thyristor conducts only the positive half cycle or the negative half cycle of the AC, and the conduction of one cycle is completed by two thyristors alternately; KM is a magnetic latching relay; Figure 7 This is a flow chart of the cloud sending instructions to the smart phase-changing switch.
[0037] The main controller calculates the degree of imbalance in real time according to the branch current size of each group of phase-changing switch boxes. If the action conditions are met, the conduction phase of each switch box is intelligently adjusted through wireless communication or power carrier communication to ensure the dynamic balance of the three-phase load. The intelligent phase-changing switch box adopts a composite switch structure of parallel anti-parallel thyristor contactors. The phase-changing process is non-stop, impact-free, fast switching speed, easy to expand and maintenance-free; that is, when the switch control board integrated on the control platform inside the phase-changing switch box receives a command from the main controller through wireless or carrier, it first opens the contactor of the current phase, then touches the thyristor of the current phase, and then removes the thyristor trigger signal. When the current is overcurrent, the thyristor of the target phase is triggered, and the contactor of the target phase is closed to complete the normal phase-changing operation. Figure 3 shown.
[0038] In this embodiment, the three-phase unbalance optimization model is established: the three-phase unbalance is mainly the three-phase current unbalance, which can be divided into two sub-functions for solution: ① the minimum value of the current unbalance; ② the minimum value of the number of commutation times;
[0039] ① Minimum value of current imbalance: Assume that there are N phase-changing switches installed on the branch, each phase-changing switch is connected to a number of user loads, and the current collected by each phase-changing switch is i1, i2, ..., i N-1 ,i N , we can get the current vector I of the commutation switch as: I=[i1,i2,...,i N-1 ,i N ], where i n is the current value collected by the nth commutation switch (n=1,2,...,N); let column vector k be the switch state vector, and use k to represent the phase connected by the commutation switch: Then we can get a 3×N switch state matrix K: K=[k1,k2,k3,...,k N ], where k n is the nth phase-changing switch state vector (n=1,2,...,N); then the three-phase currents of branch A, B, and C are: In the formula, I A ,I B ,I C is the current value of the three phases A, B and C. According to the definition of three-phase imbalance, the three-phase imbalance ρ of this branch is: The function α1 to be solved is: α1 = min(ρ);
[0040] ② Minimum number of commutation times: The number of commutation times of the solid-state intelligent commutation switch can be calculated by whether the value of the corresponding column vector k in the switch state matrix K changes. Let d be the switch change factor, and the switch change matrix D can be obtained as: D = [d1, d2, ..., d N-1,d N ], where d n is the nth phase-changing switch change factor (n=1,2,...,N); Assume that the initial value of the switch change factor d is all 0. If the column vector k of the switch state matrix m A change has occurred, that is, a phase change operation has been performed, then the corresponding switch change factor d is calculated m is 1; hence the number of commutation times σ is: The function α2 to be solved is: α2 = min(σ);
[0041] Solution of three-phase unbalanced optimization model: The optimization model established in the present invention is a discrete nonlinear optimization model, which is solved by particle swarm algorithm. The iterative formula of particle swarm algorithm is as follows: id =wv id +c1r1(p id -x id )+c2r2(p gd -x id ), x id =x id +v id , where c1 and c2 are learning factors; r1 and r2 are random numbers between 0 and 1; v id is the d-th dimension component of the flight velocity vector of iterated particle i; x id is the d-th dimension of the position vector of iterated particle i; w is the inertia weight; p id is the local extremum of iterated particle i in d dimension; p gd is the global extremum of iterated particle i in dimension d;
[0042] The state of a single commutation switch can only be [1,0,0]. T , [0,1,0] T or [0,0,1] T To represent the connection to phase A, phase B and phase C respectively; in order to simplify the calculation, 1, 2, and 3 are used to represent the connection to phase A, phase B, and phase C respectively, and the switching state matrix of the commutation switch is also simplified from the 3×N matrix K to the 1×N row phase quantity K′;
[0043] Particle swarm optimization is generally used to solve the problem of finding the optimal value of a continuous function. The optimal solution is generally not an integer. In order to solve this problem, the continuous function needs to be discretized. Each dimension ranges from 0 to 3 and is divided into three continuous intervals [0,1], (1,2], (2,3]. The number in the interval takes the maximum value of the interval. [0,1] takes 1, that is, connecting phase A; (1,2] takes 2, that is, connecting phase B; (2,3] takes 3, that is, connecting phase C.
[0044] The present invention is a three-phase unbalance management fast phase-changing switch device. During use, the main controller of the present invention can collect the load current of the substation in real time, and automatically generate and send the optimal three-phase load configuration instruction according to the capacity of the substation transformer and the severity of the imbalance; the intelligent phase-changing switch box of the present invention receives the instruction issued by the main controller and realizes the intelligent phase-changing operation, and can preferentially adjust the phase-changing switch closest to the extreme value of the line imbalance; the main controller SVG module of the present invention controls the capacity of the capacitor and the inductor by detecting the current and voltage in the power grid. By adjusting the capacity, the SVG can compensate for the reactive power in the power grid and improve the stability and reliability of the power grid. The SVG maintains the power supply by adjusting the capacity of the capacitor and the inductor at high speed. The steady-state voltage and frequency of the grid can adjust larger capacitors and sensor capacities; the phase-changing switch module can accurately control the phase and amplitude of the current and voltage to help control the current and voltage in the circuit. Through the mutual cooperation of SVG and the phase-changing switch module, the three-phase unbalanced current in the circuit can be effectively managed, thereby improving the voltage quality, stabilizing the system voltage, improving the power distribution quality, and improving the power use environment; it can reduce the line loss of the low-voltage distribution transformer in the substation, increase the power sales revenue of the power supply company, and solve the problems of transformer overload operation caused by three-phase imbalance, thereby extending the life of the transformer; the present invention has the advantages of improving voltage quality, stabilizing system voltage, reducing line loss, and solving transformer overload operation.
[0045] Example 2
[0046] like Figure 1-11 As shown, a three-phase unbalanced control fast phase-changing switch device includes a main controller and several intelligent phase-changing switch boxes and a main station. The intelligent phase-changing switch box includes a control platform for realizing comprehensive analysis of collected data and issuing optimal phase-changing operations and a phase-changing switch for realizing current data collection and phase-changing operations. The phase-changing switch is a solid-state intelligent phase-changing switch, including a three-phase solid-state switch, a current sensor, a DSP controller, a drive protection device and a communication device.
[0047] The main controller collects the load current of the substation in real time and uploads it to the main station cloud. The main station cloud automatically generates and sends the optimal three-phase load configuration instructions to the intelligent phase-changing switch box according to the capacity of the substation transformer and the severity of the imbalance, so that the load is distributed as evenly as possible to the three phases, reducing the three-phase imbalance; the intelligent phase-changing switch box receives the instructions issued by the main controller and implements intelligent phase-changing operations, and can give priority to adjusting the phase-changing switch closest to the extreme value of the line imbalance.
[0048] The three-phase unbalance control fast phase-changing switch device also includes a static synchronous compensator that is simultaneously incorporated into the distribution network with the intelligent phase-changing switch box to control the three-phase imbalance of the distribution network. The intelligent phase-changing switch makes a large adjustment to the three-phase imbalance, and then the imbalance in the line is controlled by the static synchronous compensator to minimize the three-phase imbalance as much as possible.
[0049] The static synchronous compensator adopts a STATCOM whose main circuit structure is a split capacitor topology structure.
[0050] In this embodiment, ① three-phase imbalance calculation: the three-phase imbalance at the public access point in the distribution network cannot have a negative sequence voltage (current) greater than 2% for a long time, and cannot exceed 4% for a short time. ; The present invention takes current imbalance as an example, and adopts the following method: subtract the maximum phase current value from the minimum phase current value in the three-phase current, divide the difference by the average value of the three-phase current, and multiply it by 100%: Where, ε is the three-phase current unbalance; I max is the maximum phase current value; I min is the minimum phase current value; I A ,I B ,I C are the current values of each phase respectively; I av is the average value of three-phase current;
[0051] ② In a three-phase four-wire circuit, a STATCOM with a split capacitor structure can form a zero-sequence path to compensate for the zero-sequence component of the current in the line. Therefore, the present invention adopts a split capacitor topology as the main circuit structure. Figure 8 In, L1, L2, L3, L n Respectively represent the inductance in each circuit, U dc Represents the capacitor voltage on the DC side; the working principle of STATCOM is as follows Fig. 9 As shown, the current signal i in the three-phase circuit is detected by the current transformer sa 、i sb 、i sc The current signal that needs to be compensated is obtained by calculation, and the obtained current signal is processed in a series of ways, and the inverter generates a current i of the corresponding magnitude. a 、i b 、i c Send it to the three-phase circuit, so as to achieve the control of three-phase imbalance problem and compensation of reactive current; Fig. 9 in i sa 、i sb 、i sc They represent the distribution network current, i La 、i Lb 、i Lc They represent the load current, ia 、i b 、i c represents the compensation current of STATCOM, i N 、i n is the neutral current;
[0052] ③STATCOM compensation current detection and DC side voltage stability control method: three-phase four-wire system p -i q The command current detection method uses a phase-locked loop and a sine-cosine generator to obtain a sine-cosine signal in phase with the A-phase voltage of the power grid, so as to eliminate the influence of voltage distortion on the detection result; since the main difference between the three-phase four-wire system and the three-phase three-wire system is the existence of zero-sequence current on the neutral line of the three-phase four-wire system, the command current detection methods used for the two different systems are also different. The traditional command current detection method of the three-phase four-wire system is to first separate the zero-sequence current from the three-phase current, and then use i p -i q The detection method extracts negative sequence current and reactive current;
[0053] Among them, e a Refers to the grid voltage, i a 、i b 、i c Refers to the three-phase load current, which passes through C 32 and C T Transformation to obtain the active current component i p , and then pass through a low-pass filter to obtain i p The DC component i p , then C 23 and Perform inverse transformation to obtain the three-phase fundamental positive sequence current component i af 、i bf 、i cf ; C 32 and C 23 Refers to Clark transform and its inverse transform, C T and Refers to Park transform and its inverse transform, i α and i β The three-phase load current passes through C 32 The current in the αβ coordinate obtained by transformation, i ah 、i bh 、i ch is the final output current;
[0054] Clark transformation and Park transformation: Before the transformation, the αβ coordinate system is established and the three-phase current i a 、i b 、i cPerform αβ transformation to get From the above formula, we can know that the three-phase current i a 、i b 、i c The current i obtained after Clark transformation α and i β There is no longer a zero-sequence component in the system, but since the proportional-integral controller tracks the DC reference signal better, it is necessary to transform the stationary αβ coordinate system into a rotating dq coordinate system based on the Cark transformation, namely the Park transformation. The active current component i can be obtained through the Park transformation. p and reactive current component i q : The active current component i obtained by Park transformation p and reactive current component i q Through low-pass filters, the DC component i is extracted Lp and i Lq After that, the fundamental current component i is obtained through Park inverse transform and Clark transform. Laf 、i Lbf 、i Lcf ; When STATCOM performs unbalanced compensation on the three-phase four-wire line, for the fundamental negative sequence component, the instantaneous power generated by the device is not zero, which will cause the DC side voltage to fluctuate. At the same time, for the STATCOM with a split capacitor structure, the zero-sequence compensation current generated by the device will cause the voltage values of the upper and lower capacitors to be unequal when passing through the DC side capacitor neutral line; therefore, in order to make the STATCOM with a split capacitor structure work normally and stably, it is necessary to ensure the stability of its DC side voltage and maintain the voltage values of the upper and lower capacitors equal;
[0055] DC side voltage stabilization: The common method for stabilizing the DC side capacitor voltage is the PI control method, which is to make a difference between the voltage in the line and the reference voltage, pass the difference through the PI controller, and use the output signal of the PI controller as the active current regulation signal of the STATCOM, and then superimpose it on the instantaneous active current to keep the DC side capacitor voltage stable;
[0056] DC side capacitor voltage balancing: The commonly used method for DC side capacitor voltage balancing is to make the difference between the compensation current actually output by STATCOM and the compensation current obtained through calculation, and pass the difference through a PI controller, so that the output signal of the PI controller is used as the DC bias component of the zero-sequence current, and this component is superimposed on the command current to generate a compensation current, so as to maintain the voltage of the two capacitors on the DC side equal.
[0057] The present invention is a three-phase unbalanced fast phase-changing switch device. During use, the main controller of the present invention can collect the load current of the substation in real time, and automatically generate and send the optimal three-phase load configuration instruction according to the capacity of the substation transformer and the severity of the imbalance; the intelligent phase-changing switch box of the present invention receives the instruction sent by the main controller and realizes the intelligent phase-changing operation, and can preferentially adjust the phase-changing switch closest to the extreme value of the line imbalance; the present invention adopts the method of combining the intelligent phase-changing switch with the STATCOM, firstly, the load in the line is roughly evenly distributed through the intelligent phase-changing switch, and then the reactive current in the line is compensated through the STATCOM to achieve the purpose of three-phase balance, thereby improving the voltage quality, stabilizing the system voltage, improving the power distribution quality, and improving the power use environment; it can reduce the substation line loss of the low-voltage distribution transformer, increase the power sales revenue of the power supply company, and at the same time solve the problems of transformer overload operation caused by three-phase imbalance, and extend the life of the transformer; the present invention has the advantages of improving voltage quality, stabilizing the system voltage, reducing line loss, and solving the problem of transformer overload operation.
[0058] Example 3
[0059] like Figure 1-11 As shown, a commutation control method of a three-phase unbalance management fast commutation switch device based on self-learning control is implemented by using the three-phase unbalance management fast commutation switch device as described above, and the control method includes the following steps:
[0060] Step 1: Calculate the average value k and maximum value I of the three-phase current of the branch according to the three-phase current of the branch max , minimum value I min , the phase corresponding to the maximum value, the phase corresponding to the minimum value, and the upper deviation value Δx;
[0061] Step 2: According to the phase corresponding to the maximum value obtained above, find the switches corresponding to the phase in the branch, and obtain their three-phase current values and switch addresses, and put them into two arrays;
[0062] Step 3: Calculate the three-phase unbalance;
[0063] Step 4: Subtract the upper deviation value from the current of the switch obtained in turn. If the difference is greater than the set threshold, save their difference and continue to poll other switches. If the current of the subsequent switch and the upper deviation value are greater than the threshold and the difference is less than the previously saved difference, replace them. After polling all branch switches, a switch can be selected.
[0064] Step 5: Find the switch whose current is closest to the upper deviation value through the above, then use the difference between the original deviation value and the current value of the switch as the new deviation value, and set the current value of the switch to the upper deviation value plus 1 (to ensure that it will not be re-read and selected during the next recursion);
[0065] Step 6: Return to step 4 and continue to poll all branch switches until the difference between the upper deviation value and all switch current values is less than the set threshold. Then the polling of the branch switches is completed, and the number of switches to be switched, the addresses of all switches, the current phase of the switches, and the phase to be switched to can be obtained.
[0066] Step 7: Starting from multi-objective optimization and adjustment, based on the data collected by the three-phase unbalanced fast-changing switch device and its own equipment status, an online self-learning control system is introduced to learn the content of the network, covering the status and information of the current transformer in the substation, the voltage and current of each branch, the status of each switch, the adjustment method of the historical imbalance degree and the characteristics of the historical load, so as to realize the autonomous control of the controller, such as Fig.11 shown.
[0067] In this embodiment, the self-learning control has four main functions: search, recognition, memory and reasoning; on this basis, it is divided into two categories: online self-learning control system and offline self-learning control system; the present invention adopts the online self-learning system, the principle of the online self-learning system is as follows Fig.10 As shown, R is the reference input; u is the control action; and Y is the output response.
[0068] The calculation of the three-phase imbalance in step 3 is specifically as follows: each current collected by the phase-changing switch, I1,...,I n , the controller collects the total current at the distribution transformer outlet, and then sorts them by the total current of each phase, from large to small, they are x, y, z, and calculate the total average value: Δx=xk, Δy=yk, Δz=zk, wherein the upper deviation Δx is greater than zero, and the lower deviation Δz is less than zero.
[0069] The multi-objective optimization adjustment of the online self-learning control system in step 7 includes low imbalance and short imbalance time, few switching actions, long equipment life and no risk of permanent power outage.
[0070] The present invention is a three-phase unbalance control fast phase-changing switch device. During use, the main controller of the present invention can collect the load current of the substation in real time, and automatically generate and send the optimal three-phase load configuration instruction according to the capacity of the substation transformer and the severity of the imbalance; the intelligent phase-changing switch box of the present invention receives the instruction sent by the main controller and realizes intelligent phase-changing operation, and can give priority to adjusting the phase-changing switch closest to the extreme value of the line imbalance; the present invention considers the control of three-phase imbalance problems from both the distribution side and the line side, effectively adjusts the line imbalance and the imbalance problems on the distribution network side, and at the same time, the remaining energy of SVG can be used for reactive power compensation and harmonic control, effectively alleviating the distribution pressure, effectively improving the output of the distribution transformer, slowing down the aging of the line, extending the service life of the equipment, reducing the power maintenance work, and ensuring the safety of users' electricity use; the present invention has the advantages of improving voltage quality, stabilizing system voltage, reducing line loss, and solving the overload operation of transformers.
Claims
1. A three-phase unbalanced control fast phase-changing switch device, which includes a main controller and several intelligent phase-changing switch boxes and a main station, and is characterized by: The intelligent phase-changing switch box includes a control platform for realizing comprehensive analysis of collected data and issuing optimal phase-changing operations and a phase-changing switch for realizing current data collection and phase-changing operations. The phase-changing switch is a solid-state intelligent phase-changing switch, including a three-phase solid-state switch, a current sensor, a DSP controller, a drive protection device and a communication device.
2. The three-phase unbalance control fast phase-changing switch device according to claim 1, characterized in that: The solid-state intelligent phase-changing switch is connected to a three-phase power supply, adopts a three-phase input and single-phase output mode, connects a single-phase load to one phase of the three-phase power supply, and quickly switches the load between phases A, B, and C when necessary.
3. The three-phase unbalance control fast phase-changing switch device according to claim 2, characterized in that: The three-phase solid-state switch adopts a semi-controlled solid-state switch, including an anti-parallel thyristor module and a magnetic latching relay; wherein the anti-parallel thyristor module is composed of two anti-parallel thyristors.
4. The three-phase unbalance control fast phase-changing switch device according to claim 3, characterized in that: The main controller collects the load current of the substation in real time and uploads it to the main station cloud. The main station cloud automatically generates and sends the optimal three-phase load configuration instructions to the intelligent phase-changing switch box according to the capacity of the substation transformer and the severity of the imbalance; the intelligent phase-changing switch box receives the instructions issued by the main controller and implements intelligent phase-changing operations, and can give priority to adjusting the phase-changing switch closest to the extreme value of the line imbalance.
5. The three-phase unbalance control fast phase-changing switch device according to claim 1, characterized in that: It also includes a static synchronous compensator that is simultaneously incorporated into the distribution network with the intelligent phase-changing switch box to control the three-phase imbalance of the distribution network. The intelligent phase-changing switch makes a large adjustment to the three-phase imbalance, and then the imbalance in the line is controlled by the static synchronous compensator.
6. The three-phase unbalance control fast phase-changing switch device according to claim 5, characterized in that: The static synchronous compensator adopts a STATCOM whose main circuit structure is a split capacitor topology structure.
7. A commutation control method for a three-phase unbalance management fast commutation switch device based on self-learning control, implemented by using the three-phase unbalance management fast commutation switch device according to any one of claims 1 to 6, characterized in that: The following steps are involved: Step 1: Calculate the average value k and maximum value I of the three-phase current of the branch according to the three-phase current of the branch max , minimum value I min , the phase corresponding to the maximum value, the phase corresponding to the minimum value, and the upper deviation value Δx; Step 2: According to the phase corresponding to the maximum value obtained in step 1, find the switches corresponding to the phase in the branch, and obtain their three-phase current values and switch addresses, and put them into two arrays; Step 3: Calculate the three-phase unbalance; Step 4: Subtract the upper deviation value from the current of the switch obtained in turn. If the difference is greater than the set threshold, save their difference and continue to poll other switches. If the current of the subsequent switch and the upper deviation value are greater than the threshold and the difference is less than the previously saved difference, replace them. After polling all branch switches, a switch can be selected. Step 5: Find the switch whose current is closest to the upper deviation value through the above, then use the difference between the original deviation value and the current value of the switch as the new deviation value, and set the current value of the switch to the upper deviation value plus 1; Step 6: Return to step 4 and continue to poll all branch switches until the difference between the upper deviation value and all switch current values is less than the set threshold. Then the polling of the branch switches is completed, and the number of switches to be switched, the addresses of all switches, the current phase of the switches, and the phase to be switched to can be obtained. Step 7: Starting from multi-objective optimization and adjustment, based on the data collected by the three-phase unbalanced fast-changing switch device and its own equipment status, an online self-learning control system is introduced to learn the content of the network, covering the status and information of the current transformer in the substation, the voltage and current of each branch, the status of each switch, the historical imbalance adjustment method and the characteristics of the historical load, to achieve autonomous control of the controller.
8. The commutation control method of a three-phase unbalance management fast commutation switch device based on self-learning control as claimed in claim 7, characterized in that: The calculation of the three-phase imbalance in step 3 is specifically as follows: each current collected by the phase-changing switch, I1,...,I n , the controller collects the total current at the distribution transformer outlet, and then sorts them by the total current of each phase, from large to small, they are x, y, z, and calculate the total average value: Δx=xk, Δy=yk, Δz=zk, wherein the upper deviation Δx is greater than zero, and the lower deviation Δz is less than zero.
9. The commutation control method of a three-phase unbalance management fast commutation switch device based on self-learning control as claimed in claim 7, characterized in that: The multi-objective optimization adjustment of the online self-learning control system in step 7 includes low imbalance and short imbalance time, few switching actions, long equipment life and no risk of permanent power outage.