Adaptive zero-crossing adjustment method and system for transformer with multiple windings wound in parallel

Abstract

The invention discloses a self-adaptive zero-crossing adjustment method and system for a transformer with multiple windings wound in parallel, and solves the problems that in the prior art, a zero-crossing adjustment algorithm of the transformer is slow in adjustment rate and the loss of the transformer is large. Calculating the load rate of the transformer winding according to the current in the secondary winding and the rated current of the secondary side of the transformer; the secondary winding is operated according to the load rate of the secondary winding of the transformer, and a switching signal of a power electronic switch on the corresponding secondary winding is changed according to the operation; and if the switching signal in the step S2 is changed, judging whether the current in the secondary winding of the transformer crosses zero or not through the real-time current and a zero-crossing algorithm, and executing the operation corresponding to the switching signal. The method can effectively and rapidly adapt to the change after the fluctuation of the power grid load, reduces the loss of each winding of the transformer under long-time operation, guarantees the power supply quality of the power grid, and reduces the equipment cost and the maintenance cost.

Description

Technical Field

[0001] This invention relates to the field of electrical equipment and power system automation technology, and in particular to an adaptive zero-crossing regulation method and system for transformers with multiple windings connected in parallel. Background Technology

[0002] Currently, energy conservation and emission reduction are global economic development trends. Due to its massive size and widespread distribution, the power grid undoubtedly consumes a large amount of energy and generates considerable pollution. Therefore, under this trend, the power grid has become a crucial target for energy conservation and emission reduction. A lack of awareness of energy conservation and environmental protection in power grid planning and operation may lead to insufficient consideration of energy-saving and environmental factors in power grid design. The biggest problem with the power grid in these aspects is the significant losses during operation, such as transmission line losses and substation losses. Simultaneously, insufficient demand-side response, a lack of effective incentive mechanisms and demand-side management measures, and inflexible load management during peak and off-peak periods also result in significant resource depletion and waste. Therefore, technological advancements and intelligent management are needed to improve the efficiency of power grid operation.

[0003] Electricity undergoes multiple voltage step-up and step-down transformations from power plants to users via power transformers. Due to the large number and capacity of transformers, transformer losses are substantial. Reducing transformer losses by just 1% could save billions of kilowatt-hours of electricity annually, making research into the economic efficiency and high-efficiency operation of transformers crucial. However, existing transformer zero-crossing regulation algorithms have slow adjustment rates, failing to adapt to grid changes. Furthermore, the circulating current problem caused by parameter asymmetry in transformer windings during parallel operation remains unresolved, making grid quality susceptible to degradation. Summary of the Invention

[0004] The purpose of this invention is to solve the problems of slow adjustment rate and high transformer loss in the existing transformer zero-crossing adjustment algorithm. It provides an adaptive zero-crossing adjustment method and system for transformers with multiple windings in parallel winding. This method can effectively and quickly adapt to changes in grid load after fluctuations, reduce the loss of each winding of the transformer under long-term operation, ensure the power supply quality of the grid, and reduce equipment and maintenance costs.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: An adaptive zero-crossing adjustment method for a transformer with multiple windings connected in parallel, characterized by comprising the following steps: S1: Real-time acquisition of the current in the secondary winding of the transformer, and calculation of the load rate of the transformer winding based on the current in the secondary winding and the rated current of the transformer secondary winding; S2: The secondary winding is operated according to the load rate of the secondary winding of the transformer, and the switching signal of the power electronic switch on the corresponding secondary winding changes according to the operation; S3: If the switching signal changes in step S2, determine whether the current in the secondary winding of the transformer has crossed zero at this time by using real-time current and zero-crossing algorithm, and execute the operation corresponding to the switching signal.

[0006] By determining the economic operating range of the transformer; judging the load rate of the transformer secondary winding in real time according to the fluctuation of the grid load; determining the switching signal g of the power electronic switch based on the load rate of the secondary winding; judging whether the switching signal g has changed; if it has not changed, the judgment continues; if the switching signal g has changed, judging whether the current in the secondary winding has crossed zero; if the current has crossed zero, the operation corresponding to g is executed; otherwise, the judgment continues until the next current zero crossing point, and the operation corresponding to g is executed. This method is low-cost, highly reliable, and simple to implement, and can effectively and quickly adapt to changes in grid load and perform corresponding adjustment operations, thus keeping the distribution transformer within its economic operating range for a long time. It reduces the losses of each winding of the transformer under long-term operation, ensures the consistency of parameters of each winding, effectively reduces the circulating current problem caused by parameter asymmetry in the windings when the transformer windings are connected in parallel, ensures power supply quality over a long period, reduces transformer losses, is simple to implement, and has low hardware requirements.

[0007] Preferably, step S2 includes: if the load rate is less than 30%, disconnecting one winding and the switching signal becomes 0; if the load rate is greater than 80%, connecting a secondary winding in parallel and the switching signal becomes 1; if the load rate is between 30% and 80%, no operation is performed and the switching signal remains unchanged.

[0008] Preferably, in step S4, if the current in the secondary winding of the transformer crosses zero, the operation corresponding to the switching signal at this time is executed; if the current in the secondary winding of the transformer does not cross zero, the current signal and the zero-crossing algorithm are used to continuously determine until the next nearest current zero-crossing point, and then the operation corresponding to the switching signal is executed.

[0009] Preferably, the operating time of each parallel winding in each phase winding of the secondary side is recorded. If the operating time of a certain winding is greater than the operating time of other windings, then the winding is temporarily not used and other windings with shorter operating times are used instead. If the operating time of a certain winding is less than the operating time of other windings, then other windings are temporarily not used and the winding with shorter operating time is used instead.

[0010] Preferably, determining whether the current has crossed zero based on the real-time current and zero-crossing adjustment algorithm includes: judging the magnitude of the real-time current value and zero within a fixed time interval; if the judgment results of two adjacent time intervals are opposite, then the current has crossed zero.

[0011] Preferably, the operation corresponding to the execution switch signal includes: if the switch signal is 1, the corresponding switch is closed; if the switch signal is 0, the corresponding switch is open.

[0012] Preferably, the switching of a transformer with multiple windings in parallel includes switching from single winding to dual windings in parallel operation and switching from dual windings in parallel operation to single winding operation.

[0013] An adaptive zero-crossing regulation system for a multi-winding parallel-wound transformer includes: a transformer based on multi-winding parallel-wound, the transformer being connected to a real-time data acquisition unit for real-time acquisition of the current of the secondary winding of the transformer, the real-time data acquisition unit being connected to a central processing unit for processing the input data according to an algorithm and issuing control signals, and the central processing unit being connected to a power electronic switch for controlling the switching of the secondary winding.

[0014] Preferably, the central processing unit controls the multiple windings connected in parallel on the secondary side of the three-phase distribution transformer to be put into operation at the same time.

[0015] Preferably, the central processing unit compares the real-time secondary current acquired by the real-time data acquisition unit with the rated secondary current to obtain the real-time load rate of the secondary winding, and compares the load rate with the switching point specified inside the central processing unit to perform automatic switching.

[0016] Therefore, the present invention has the following beneficial effects: 1. Multiple windings connected in parallel on each phase of the secondary side can employ a transformer adaptive zero-crossing adjustment method to ensure that each winding is put into operation at approximately the same time, thereby reducing losses in each winding of the transformer under long-term operation. This allows the parameters of each winding in each phase to maintain a high degree of consistency after long-term operation, effectively reducing circulating current problems caused by parameter asymmetry in the windings during parallel operation, ensuring power supply quality under long-term operating conditions, and reducing transformer losses.

[0017] 2. It can effectively and quickly adapt to changes in power grid load and carry out corresponding adjustment operations, keeping the distribution transformer within the economic operating range for a long time, achieving fully automated adjustment, which is simple and easy to implement; it only requires one transformer and multiple parallel windings, greatly reducing equipment and maintenance costs, and has high economic efficiency. Attached Figure Description

[0018] Figure 1 This is a flowchart illustrating the overall steps of the adaptive zero-crossing adjustment method for a transformer with multiple windings connected in parallel, as described in Example 1.

[0019] Figure 2 This is a flowchart of the adaptive adjustment algorithm in Example 1.

[0020] Figure 3 This is a flowchart of the current zero-crossing switching algorithm in Example 1.

[0021] Figure 4 This is a schematic diagram of the topology of a distribution transformer with multiple windings connected in parallel in this invention.

[0022] Figure 5 This is the transformer efficiency curve fitted in Example 3.

[0023] Figure 6 This is a schematic diagram illustrating the current change in the secondary winding of the transformer when switching from single-winding operation to dual-winding parallel operation using the transformer adaptive zero-crossing adjustment method in Example 3.

[0024] Figure 7 This is a schematic diagram illustrating the current change in the secondary winding of the transformer when switching from single-winding operation to parallel operation of two windings without employing the transformer adaptive zero-crossing adjustment method, as shown in Example 3.

[0025] Figure 8 This is a schematic diagram illustrating the current change in the secondary winding of the transformer when switching from parallel operation of two windings to single winding operation without using the transformer adaptive zero-crossing adjustment method, as shown in Example 3.

[0026] Figure 9 This is a schematic diagram illustrating the current change in the secondary winding of the transformer when switching from parallel operation of two windings to single winding operation without using the transformer adaptive zero-crossing adjustment method, as shown in Example 3. Detailed Implementation

[0027] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0028] Example 1: This embodiment provides an adaptive zero-crossing adjustment method for a transformer with multiple windings connected in parallel, such as... Figure 1 As shown, the operation process is as follows: Step 1, the current in the secondary winding of the transformer is collected in real time, and the load rate of the transformer winding is calculated based on the current in the secondary winding and the rated current of the transformer secondary winding; Step 2, the secondary winding is operated according to the load rate of the transformer secondary winding, and the switching signal of the power electronic switch on the corresponding secondary winding changes according to the operation; Step 3, if the switching signal changes in Step 2, the current in the secondary winding of the transformer is determined to be zero-crossing at this time by real-time current and zero-crossing algorithm, and the operation corresponding to the switching signal is executed.

[0029] The adaptive zero-crossing regulation method for multi-winding parallel-wound transformers provided in this embodiment determines the transformer's economic operating range; it judges the load rate of the transformer's secondary winding in real time according to fluctuations in grid load; it determines the switching signal g of the power electronic switch based on the secondary winding load rate; it judges whether the switching signal g has changed; if it has not changed, it continues to judge; if the switching signal g has changed, it judges whether the current in the secondary winding has crossed zero; if the current has crossed zero, it executes the operation corresponding to g; otherwise, it continues to judge until the next current zero-crossing point, and then executes the operation corresponding to g. This method is low-cost, highly reliable, simple and easy to implement, and can effectively and quickly adapt to changes in grid load and perform corresponding adjustment operations, thereby keeping the distribution transformer within its economic operating range for a long time.

[0030] The following examples and specific application scenarios further illustrate the technical solution and effects of the present invention. The following examples are explanations of the present invention, but the present invention is not limited to the following examples.

[0031] Electricity undergoes multiple voltage step-up and step-down transformations from power plants to users via power transformers. Although existing transformers are highly efficient, their overall losses remain substantial due to the large number and capacity of installed units. Statistics show that in my country, transformer losses account for approximately 10% of the total power generation, and about 70% of the losses in medium- and low-voltage power grids, which account for 60%-65% of total grid losses, are attributable to power transformers. Reducing transformer losses by just 1% could save billions of kilowatt-hours of electricity annually. These figures underscore the crucial need for research into the economic efficiency and high-efficiency operation of transformers.

[0032] To address the issues of transformer losses and efficient operation, distribution transformers with capacity regulation functions, also known as adjustable-capacity transformers, can dynamically adjust their capacity according to system load conditions. This reduces transformer losses and ensures the transformer always operates at a high efficiency. Therefore, research on adjustable-capacity transformers has become one of the focal points of distribution transformer research in recent years. To date, the development of adjustable-capacity transformers has gone through several main stages: off-load adjustable-capacity and off-load voltage regulating distribution transformers; on-load adjustable-capacity and off-load voltage regulating distribution transformers; and automatic adjustable-capacity and automatic voltage regulating distribution transformers.

[0033] Therefore, based on the structure and principle of adaptive load-adjustable distribution transformers, this embodiment provides an adaptive zero-crossing regulation method for transformers with multiple windings in parallel. The aim is to provide an adaptive zero-crossing regulation algorithm for distribution transformers based on multiple windings in parallel, which can effectively and quickly adapt to changes in grid load and perform corresponding adjustment operations, thereby keeping the distribution transformer within its economic operating range for extended periods. This reduces losses in each winding of the transformer during long-term operation, ensures the consistency of parameters for each winding, effectively reduces circulating current problems caused by parameter asymmetry in the windings during parallel operation, guarantees power supply quality over long periods, reduces transformer losses, is simple to implement, and has low hardware requirements.

[0034] The adaptive zero-crossing adjustment method for transformers with multiple parallel windings specifically includes the following steps: Step 1: Real-time acquisition of the current in the secondary winding of the transformer, and calculation of the load rate of the transformer winding based on the current in the secondary winding and the rated current of the transformer secondary winding.

[0035] In the normal operation of a distribution transformer based on multi-winding parallel windings, changes in grid load can cause the load rate of the transformer's secondary winding to fall below 30% or rise above 80%, placing the transformer in a light or heavy load state. Under these conditions, the transformer efficiency is low and losses are significant. Real-time acquisition of the transformer's secondary winding current can effectively and quickly capture current changes following fluctuations in grid load.

[0036] This embodiment takes the case where each phase of the transformer secondary side has two windings as an example: Based on the measured current i2 in the secondary winding and the rated current I of the transformer secondary winding. 2N The load factor (efficiency) η of the transformer winding is calculated as follows:

[0037] Step 2: Operate the secondary winding according to the load rate of the transformer secondary winding, and the switching signal of the power electronic switch on the corresponding secondary winding changes according to the operation.

[0038] An adaptive adjustment algorithm is used to determine the necessary operations for the secondary winding based on the calculated load rate η of the transformer winding.

[0039] The specific steps of the adaptive adjustment algorithm are as follows: Figure 2 As shown: If the load rate is less than 30%, one transformer secondary winding needs to be disconnected, and the switching signal g of the power electronic switch on the corresponding transformer secondary winding will become 0. If the load rate is >80%, a transformer secondary winding needs to be connected in parallel, and the switching signal g of the power electronic switch on the corresponding transformer secondary winding becomes 1. If 30% ≤ load rate ≤ 80%, the switching signal g of the power electronic switch on the secondary winding of the transformer remains unchanged.

[0040] Expressed as a formula:

[0041] If each phase of the transformer secondary side has multiple windings, then if the load rate is less than 30%, the number of windings that need to be disconnected is calculated, and a disconnect signal is sent to the corresponding winding switch; if the load rate is greater than 80%, the number of windings that need to be connected is calculated, and an open signal is sent to the corresponding winding switch; otherwise, the switch signal remains unchanged.

[0042] Step 3: If the switching signal in step 2 changes, determine whether the current in the secondary winding of the transformer has crossed zero using real-time current and zero-crossing algorithms, and execute the operation corresponding to the switching signal.

[0043] When the load rate on the secondary side of the transformer changes, the zero-crossing switching algorithm needs to be used to perform the corresponding operation through the switching signal g.

[0044] like Figure 4 As shown, first determine whether the switch signal g changed in the second step. If the switch signal g did not change, return to the second step and continue to determine whether the switch signal changed; if the switch signal g changed, execute the subsequent steps.

[0045] When the switching signal g changes, the system uses real-time current and a zero-crossing algorithm to determine whether the current in the transformer's secondary winding has crossed zero. If the current in the secondary winding has crossed zero, the operation corresponding to the switching signal g is executed. If the current in the secondary winding has not crossed zero, the system continues to determine zero-crossing using the current signal and the zero-crossing algorithm until the next nearest zero-crossing point, at which point the operation corresponding to the switching signal g is executed again. This further enables the switching of the secondary winding of the distribution transformer, achieving economical operation.

[0046] Furthermore, since the current waveform is a sine wave, the zero-crossing algorithm determines the magnitude of the real-time current value relative to 0 within a fixed short time interval. If two adjacent judgments are opposite, then the current crosses zero.

[0047] The operation corresponding to the switch signal g is as follows: if the switch signal is 1, the corresponding switch is closed; if the switch signal is 0, the corresponding switch is open.

[0048] Based on the above steps, it is possible to simultaneously control the operating time of each winding in the parallel windings of the secondary side of a three-phase distribution transformer to be approximately the same. This is achieved by recording the operating time of each parallel winding in the secondary side of each phase in the zero-crossing adjustment algorithm. Since the effect of operating any one of the parallel windings in the same phase is the same, when comparing the operating times of each winding, if it is found that the operating time of some windings is much longer than that of other windings (i.e., greater than the preset first threshold), then that winding is temporarily not used and other windings with shorter operating times are used instead. Conversely, if it is found that the operating time of some windings is much shorter than that of other windings (i.e., less than the preset second threshold), then other windings are temporarily not used and the winding with shorter operating time is used instead.

[0049] The adaptive zero-crossing adjustment method for a transformer with multiple windings connected in parallel, provided in this embodiment, has the following beneficial effects: (1) The adaptive zero-crossing adjustment method of the multi-winding parallel winding transformer provided in this embodiment can effectively and quickly adapt to the changes in the power grid load after fluctuations occur, and perform corresponding adjustment operations, so that the distribution transformer is in the economic operating range for a long time, realizing fully automated adjustment, which is simple and easy to implement.

[0050] (2) Compared with the traditional three-phase transformer topology, the multi-winding parallel winding three-phase distribution transformer topology proposed in this embodiment allows the control algorithm to ensure that the multiple windings connected in parallel on each phase of the secondary side are put into operation at approximately the same time, thereby reducing the losses of each winding of the transformer under long-term operation. This ensures that the parameters of each winding in each phase can maintain a high degree of consistency after long-term operation, effectively reducing the circulating current problem caused by parameter asymmetry in the windings during parallel operation, ensuring the power supply quality of the power grid under long-term operation conditions, and reducing transformer losses.

[0051] (3) The adaptive zero-crossing adjustment algorithm for distribution transformers based on multi-winding parallel winding proposed in this embodiment requires only one transformer and multiple parallel windings, which greatly reduces equipment and maintenance costs and has high economic efficiency compared to the traditional multi-transformer parallel operation mode.

[0052] Example 2: This embodiment provides an adaptive zero-crossing adjustment system for a transformer with multiple windings connected in parallel, used to execute an adaptive zero-crossing adjustment method for a transformer with multiple windings connected in parallel as described in Embodiment 1.

[0053] Specifically: The adaptive zero-crossing regulation algorithm for distribution transformers based on multi-winding parallel winding is implemented through an adaptive zero-crossing regulation system for multi-winding parallel winding transformers. The adaptive zero-crossing regulation system includes: a distribution transformer based on multi-winding parallel winding, a real-time data acquisition unit, a current sampling circuit, a current sensor, a power electronic switch, a communication unit, and a central processing unit. The distribution transformer is connected to the current sensor and the current sampling circuit, respectively. The current sensor and the current sampling circuit are connected to the real-time data acquisition unit. The real-time data acquisition unit and the central processing unit are connected through the communication unit. The central processing unit is connected to the power electronic switch.

[0054] The topology of a distribution transformer with multiple windings connected in parallel is as follows: Figure 4 As shown.

[0055] Furthermore, the real-time data acquisition unit is used to acquire the current of the secondary winding of the transformer in real time. The current sampling circuit and current sensor are used to measure the transformer current and then transmit it to the real-time data acquisition unit. The communication unit is used to transmit signals in real time. The central processing unit is responsible for processing the input data according to the algorithm and issuing control signals. The power electronic switch is responsible for controlling the switching operation of the secondary winding.

[0056] When the adaptive zero-crossing regulation system of a multi-winding parallel-wound transformer is working, the current sampling circuit and current sensor measure the current in the secondary winding of the transformer and transmit it to the real-time data acquisition unit. The real-time data acquisition unit sends the acquired real-time current data to the central processing unit through the communication unit. The central processing unit has the rated current of the secondary winding of the transformer stored in its memory. The central processing unit calculates the load rate of the secondary winding of the transformer based on the ratio of the real-time current to the rated current.

[0057] Meanwhile, the central processing unit contains an algorithm that can determine the operation required for the secondary winding of the transformer based on the calculated load rate of the transformer winding, and send control commands to the power electronic switch. The power electronic switch then controls the secondary winding of the transformer to perform the corresponding operation according to the control commands.

[0058] Simultaneously, because the secondary winding has been operated on, the switching signals of the corresponding power electronic switches on the winding also change accordingly. When the switching signal changes, the central processing unit (CPU) uses its internally stored zero-crossing algorithm, combined with the real-time current received by the CPU, to determine whether the current in the transformer's secondary winding has crossed zero. If the current crosses zero, the CPU executes the operation corresponding to the switching signal. This achieves the switching of the secondary winding of the distribution transformer, enabling economical operation.

[0059] Example 3: This embodiment provides an adaptive zero-crossing adjustment method for a transformer with multiple windings connected in parallel. By applying it to a specific application scenario, the adaptive zero-crossing adjustment method for a transformer with multiple windings connected in parallel in Embodiment 1 is simulated and verified.

[0060] Specifically: In this embodiment, an adaptive zero-crossing adjustment method for a multi-winding parallel-wound transformer is described, specifically for adaptive zero-crossing adjustment of a distribution transformer based on multi-winding parallel-wound. The basic parameters of the multi-winding parallel-wound distribution transformer are: rated capacity S... N =630KVA, rated frequency f N =50Hz, primary-secondary ratio k =10KV / 400V.

[0061] During simulation verification, the transformer conditions were: grid frequency of 50Hz and one electrical cycle of 0.02s. When switching from single-winding to dual-winding parallel operation, the load on the single-winding transformer decreased from 45% to 29% at 0.1s. After the load decreased by 0.1s, an adaptive zero-crossing adjustment algorithm was applied at both the current zero-crossing and non-zero-crossing points. When switching from dual-winding parallel operation to single-winding operation, the load on each winding of the transformer increased from 45% to 81% at 0.1s. After the load increased by 0.1s, an adaptive zero-crossing adjustment algorithm was applied at both the current zero-crossing and non-zero-crossing points.

[0062] The simulated transformer controls the switching operation of the windings via power electronic switches, and the fitted transformer efficiency curve is as follows: Figure 5 As shown.

[0063] Its zero-crossing adjustment algorithm includes the following steps: Step 1: Use a current sensor to measure the current in the secondary winding of the transformer and use a real-time data acquisition unit to collect the data in real time.

[0064] Step 2: Taking the case where each phase of the transformer secondary side has two windings as an example: Based on the measured current i2 in the secondary winding and the rated current I of the transformer secondary winding. 2N The calculated load factor (efficiency) η of the transformer winding is:

[0065] Step 3: Based on the calculated load factor η of the transformer winding, determine the operation required for the secondary winding. If η < 30%, one winding needs to be disconnected, and the switching signal g of the corresponding power electronic switch on the winding becomes 0; if η > 80%, one winding needs to be connected in parallel, and the switching signal g of the corresponding power electronic switch on the winding becomes 1; otherwise, the switching signal g of the power electronic switch on the secondary winding remains unchanged.

[0066] Step 4: When the load rate on the secondary side of the transformer changes, corresponding operations need to be performed via the switching signal g. First, determine whether the switching signal g changed in Step 3. If g does not change, continue to Step 4; if g changes, proceed to Step 5.

[0067] Step 5: When the switch signal g changes, the current in the transformer secondary winding is determined to be zero-crossing using real-time current and a zero-crossing algorithm. Since the current waveform is sinusoidal, the zero-crossing algorithm compares the real-time current value with zero within a fixed short time interval. If two adjacent comparisons result in opposite values, the current has crossed zero. If the current in the transformer secondary winding is exactly zero-crossing, the operation corresponding to the switch signal g is executed: if the switch signal is 1, the corresponding switch is closed; if the switch signal is 0, the corresponding switch is open. If the current in the transformer secondary winding is not zero-crossing, the current signal and the zero-crossing algorithm are used to continuously determine whether the current has crossed zero-crossing, and then the operation corresponding to the switch signal g is executed again.

[0068] An adaptive algorithm is used to calculate the load rate of the transformer secondary winding in real time to determine whether a corresponding switching operation is needed. The adaptive algorithm involves collecting the transformer secondary current value in real time, comparing it to the rated secondary current, and obtaining the percentage as the real-time load rate η of the secondary winding. This percentage is then compared with the switching point specified in step three to achieve automatic switching. When the grid load changes, the output switching signal g is adjusted accordingly, and it is determined whether g has changed. After the switching signal g changes, a zero-crossing adjustment algorithm is used to ensure that the switching operation corresponding to g is performed only at the zero-crossing point of the winding current, thus implementing a simple, easy-to-implement, computationally inefficient, robust, and economical adaptive zero-crossing control strategy.

[0069] When the simulated transformer switches from single-winding to dual-winding parallel operation, the load on the single winding decreases from 45% to 29% at 0.1s; when switching from dual-winding parallel operation to single-winding operation, the load on both windings increases from 45% to 81% at 0.1s.

[0070] The simulation results are as follows Figures 6-9 As shown, where, Figure 6 In the case where each phase of the transformer secondary side has two windings, when switching from single-winding operation to parallel operation of two windings, the current change in the transformer secondary winding is observed when the switching signal g changes at the current zero-crossing point and non-zero-crossing point, respectively, using the adaptive zero-crossing adjustment method (algorithm) provided in this embodiment. Figure 7When the transformer secondary winding has two windings per phase, and the operation changes from single-winding to parallel operation of two windings, the current changes in the transformer secondary winding without using the adaptive zero-crossing adjustment method provided in this embodiment are analyzed when the switching signal g changes at the current zero-crossing point and non-zero-crossing point. Figure 8 When the transformer secondary side has two windings per phase, and the operation changes from parallel operation of two windings to single winding operation, the current change in the transformer secondary winding is observed when the switching signal g changes at the current zero-crossing point and non-zero-crossing point, respectively, using the adaptive zero-crossing adjustment method provided in this embodiment. Figure 9 When the transformer secondary winding has two windings per phase, and the operation changes from parallel operation of two windings to single winding operation, the current changes in the transformer secondary winding without using the adaptive zero-crossing adjustment method provided in this embodiment are analyzed when the switching signal g changes at the current zero-crossing point and non-zero-crossing point.

[0071] according to Figures 6-9 As shown, during the transition between single-winding operation and dual-winding parallel operation, when the switching signal g changes at the current zero-crossing point and non-zero-crossing point, the current changes in the secondary winding of the transformer are compared with those without the adaptive zero-crossing adjustment method provided in this embodiment. It can be found that the adaptive zero-crossing adjustment method provided in this embodiment has a good control effect, realizing adaptive zero-crossing adjustment of the distribution transformer based on multi-winding parallel winding, thereby ensuring the power supply quality of the power grid under long-term operating conditions, reducing transformer losses and power grid costs, and improving the economy and automation of system operation.

[0072] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way. Other variations and modifications are possible without departing from the technical solutions described in the claims.

Claims

1. A method for adaptive zero-crossing adjustment of a transformer with multiple windings connected in parallel, characterized in that, include: S1: Real-time acquisition of the current in the secondary winding of the transformer, and calculation of the load rate of the transformer winding based on the current in the secondary winding and the rated current of the transformer secondary winding; S2: The secondary winding is operated according to the load rate of the secondary winding of the transformer, and the switching signal of the power electronic switch on the corresponding secondary winding changes according to the operation; S3: If the switching signal changes in step S2, determine whether the current in the secondary winding of the transformer has crossed zero at this time by using real-time current and zero-crossing algorithm, and execute the operation corresponding to the switching signal.

2. The adaptive zero-crossing adjustment method for a multi-winding parallel-wound transformer according to claim 1, characterized in that, Step S2 includes: if the load rate is less than 30%, disconnect one winding and the switch signal becomes 0; if the load rate is greater than 80%, connect a secondary winding in parallel and the switch signal becomes 1; if the load rate is between 30% and 80%, no operation is performed and the switch signal remains unchanged.

3. The adaptive zero-crossing adjustment method for a multi-winding parallel-wound transformer according to claim 1, characterized in that, In step S4, if the current in the secondary winding of the transformer crosses zero, the operation corresponding to the switching signal at this time is executed; if the current in the secondary winding of the transformer does not cross zero, the current signal and the zero-crossing algorithm are used to continuously determine until the next nearest current zero-crossing point, and then the operation corresponding to the switching signal is executed.

4. The adaptive zero-crossing adjustment method for a multi-winding parallel-wound transformer according to claim 1, 2, or 3, characterized in that, Record the operating time of each parallel winding in each phase of the secondary winding. If the operating time of a certain winding is greater than the operating time of other windings, then the winding is temporarily not used and other windings with shorter operating times are used instead. If the operating time of a certain winding is less than the operating time of other windings, then other windings are temporarily not used and the winding with shorter operating time is used instead.

5. A method for adaptive zero-crossing adjustment of a multi-winding parallel-wound transformer according to claim 1, 2, or 3, characterized in that, Determining whether the current has crossed zero based on the real-time current and zero-crossing adjustment algorithm includes: comparing the real-time current value with zero within a fixed time interval; if the results of two adjacent time intervals are opposite, then the current has crossed zero.

6. The adaptive zero-crossing adjustment method for a multi-winding parallel-wound transformer according to claim 1 or 3, characterized in that, The operation corresponding to the execution switch signal includes: if the switch signal is 1, the corresponding switch is closed; if the switch signal is 0, the corresponding switch is open.

7. A method for adaptive zero-crossing adjustment of a multi-winding parallel-wound transformer according to claim 1, 2, or 3, characterized in that, Switching of transformers with multiple windings in parallel includes switching from single-winding operation to dual-winding parallel operation and switching from dual-winding parallel operation to single-winding operation.

8. An adaptive zero-crossing adjustment system for a multi-winding parallel-wound transformer, employing the adaptive zero-crossing adjustment method for a multi-winding parallel-wound transformer as described in any one of claims 1-7, characterized in that, The transformer includes a transformer based on parallel winding of multiple windings. The transformer is connected to a real-time data acquisition unit that collects the current of the secondary winding in real time. The real-time data acquisition unit is connected to a central processing unit that processes the input data according to an algorithm and issues control signals. The central processing unit is connected to a power electronic switch that controls the switching of the secondary winding.

9. The adaptive zero-crossing adjustment system for a multi-winding parallel-wound transformer according to claim 8, characterized in that, The central processing unit controls the operation of the multiple windings connected in parallel on the secondary side of the three-phase distribution transformer with multiple windings to be put into operation at the same time.

10. A transformer adaptive zero-crossing adjustment system with multiple windings connected in parallel, as described in claim 8 or 9, characterized in that, The central processing unit compares the real-time secondary current acquired by the real-time data acquisition unit with the rated secondary current to obtain the real-time load rate of the secondary winding. It then compares the load rate with the switching point specified inside the central processing unit to perform automatic switching.

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