Flexible distribution transformer structure and optimization control method thereof
By staggering the power angles of the load voltage and the grid-side voltage in the flexible distribution transformer and adopting a five-winding structure and optimized control method, the high copper loss problem of the flexible distribution transformer when in the same phase is solved, achieving minimum loss and efficient operation, and being suitable for voltage regulation of new distribution networks.
Patent Information
- Application Number
- CN202510959167.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-11
- Publication Date
- 2025-09-26
AI Technical Summary
When the load voltage of the existing flexible distribution transformer is in phase with the grid-side voltage, the output current of the parallel-side converter is maximized, copper loss increases, overall efficiency decreases, and minimum loss operation cannot be achieved.
By staggering the load voltage and the grid-side voltage by an optimal power angle, a five-winding structure and optimized control method are adopted, including a main transformer, an isolation transformer, an energy-taking converter and a voltage-regulated converter, combined with DC capacitors, and the control parameters are optimized to achieve minimum loss.
The flexible distribution transformer reduces operating losses, improves equipment efficiency and reliability on the basis of unity power factor control and load voltage stability, and is suitable for voltage regulation in new distribution networks.
Smart Images
Figure CN120710011A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of electric power system electrical equipment, and in particular to a flexible distribution transformer structure and an optimization control method thereof. Background Art
[0002] Flexible distribution transformers combine the technical advantages of traditional distribution transformers and power electronic converters. By integrating the power electronic converter with the power transformer, the inexpensive and reliable conventional electromagnetic power transformer performs full power conversion, while the converter, which only accounts for approximately 10% of the transformer's capacity, provides rapid and continuous regulation. Flexible distribution transformers offer advantages such as arc-free switching, flexible control, and fast response. They can meet the voltage regulation requirements of new distribution networks and are a key trend in the development of next-generation electrical equipment.
[0003] A hybrid flexible transformer, formed by combining a traditional power transformer with a series-parallel converter, combines the control functions of both parallel and series converters. It can regulate both the current of the input grid and the voltage of the output, enabling comprehensive management of power quality and multifunctional control of the power system. In existing control strategies, when the load voltage is controlled to be in phase with the grid voltage, the compensation voltage output by the series-side converter reaches a minimum, and the iron loss of the series-coupled transformer is theoretically minimized. However, at this time, the output current of the parallel-side converter reaches a maximum, resulting in high copper loss in the circuit containing the parallel-side converter. Having the load voltage in phase with the grid voltage is not conducive to improving the overall efficiency of the flexible transformer. Summary of the Invention
[0004] The technical problem to be solved by the present invention is to provide a flexible distribution transformer structure and an optimization control method thereof, which staggers the load voltage and the grid-side voltage by an optimal power angle, enables the flexible distribution transformer to operate in the minimum loss mode, realizes power angle optimization control, and thus reduces its operating loss.
[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is: a flexible distribution transformer structure, including a main transformer , isolation transformer , energy-taking converter , voltage control converter and five windings , main transformer High voltage side primary winding Use delta connection and connect to the power grid; main transformer Low voltage side secondary winding The star connection with neutral point grounding is adopted, the winding side is connected to the load, and the neutral point side is connected to the voltage control converter. Through an isolation transformer Series connection; Isolation transformer The primary winding With the main transformer Low voltage side secondary winding The neutral point side of the isolation transformer is connected; The secondary winding With voltage regulation converter Connected to; main transformer Low voltage side tertiary winding Use star connection with neutral point grounding and connect with energy converter Parallel; voltage-regulated converters and energy-extraction converters Coupling through DC capacitors; energy-taking converter Used to maintain DC capacitor voltage stability, voltage regulation converter Used to invert a voltage with freely adjustable amplitude and phase angle.
[0006] An optimization control method for a flexible distribution transformer structure comprises the following steps: S1: Obtaining configuration parameters of the flexible distribution transformer; S2: Acquire electrical parameters of the target line controlled by the flexible distribution transformer; S3: Calculating control parameters of the flexible distribution transformer according to the configuration parameters and electrical parameters; S4: Outputting the regulated voltage of the flexible distribution transformer to complete the optimized control of the flexible distribution transformer.
[0007] Preferably, the configuration parameters include: the turns ratio of the primary winding to the secondary winding of the main transformer, the turns ratio of the primary winding to the tertiary winding of the transformer, the turns ratio of the secondary winding to the tertiary winding of the transformer, the turns ratio of the primary winding to the secondary winding of the isolation transformer, the resistance of the tertiary winding of the main transformer, the excitation resistance of the isolation transformer, and the centralized equivalent resistance of the voltage-controlled converter.
[0008] Preferably, the electrical parameters include: the node input voltage of the target line, the node input current of the target line, the node input phase angle of the target line, the primary side rated voltage of the main transformer, the grid side rated voltage, the grid side voltage coefficient, and the preset target output voltage of the target line.
[0009] Preferably, the control parameters include: a d-axis component of a voltage reference signal injected into a target line, a q-axis component of a voltage reference signal injected into a target line, and a control voltage that a control converter of the flexible distribution transformer should output.
[0010] Preferably, step S3 includes the following steps: S31: Determine parameters related to operating losses in the flexible power distribution transformer; S32: Determine the relationship between the control parameters of the flexible distribution transformer and the variable loss related parameters; S33: Determine control parameters of the flexible distribution transformer.
[0011] Preferably, the step S31 is specifically as follows: The overall loss includes copper loss and iron loss. Among them, iron loss includes The iron loss is recorded as ,and The iron loss is recorded as ; Copper loss includes 、 The copper loss of the circuit is recorded as ,and The copper loss of the circuit is recorded as ,as well as The copper loss of the circuit is recorded as ,and The copper loss of the circuit is recorded as Assuming three-phase symmetry, the total loss of the flexible distribution transformer is ,but ; (1) ; (2) Where, for Wirewound resistor; for The concentrated equivalent resistance; express The magnetizing resistance of the three-phase circuit is symmetrical, so the subscripts of the three-phase quantities can be omitted.
[0012] The basic operating requirement of the flexible distribution transformer is to compensate the grid side to unity power factor and control the load voltage to the rated voltage. Under certain steady-state conditions, are fixed, so is approximately fixed, and and Needs to be optimized.
[0013] Let the variable loss of the flexible distribution transformer be ,but ; (3) In the formula, the fixed quantity can be considered as a constant. is an equivalent constant; From formula (3), we can get that the parameters related to variable loss are: the current of the tertiary winding of the main transformer , the voltage of the primary winding of the isolation transformer , Main transformer tertiary winding resistance , the excitation resistance of the isolation transformer and the concentrated equivalent resistance of the voltage-regulated converter .
[0014] Preferably, the specific steps of step S32 are as follows: 1) Calculate the transformer winding: neglect and According to the principle of magnetic potential balance, the excitation current can be obtained as follows: ; (4) Where, They are The effective value phasor of is the number of turns of 5 windings; Will The variables in side, and will The variables in On the other hand, formula (4) can be transformed into: ; (5) 2) Determine the relationship between load voltage, grid voltage and parameters related to variable losses: According to the circuit principle, we can get: (6) 3) According to the actual operation of the distribution transformer, the parameter conversion conditions are obtained: After the flexible distribution transformer enters the steady-state condition, is controlled to an amplitude equal to its rated voltage The sine wave, at this time middle Rated voltage Approximately the grid-side rated voltage Equal, that is ,but Rated voltage ; The active power input from the grid side of the flexible distribution transformer must be equal to the active power absorbed by its load, so the following formula holds: ; (7) Available ; (8) The variables in formula (6) are converted to Side, then ; (9) During normal operation of the flexible distribution transformer, Often around its rated value Up and down fluctuations, thus ; (10) Where, is the grid-side voltage fluctuation coefficient; 4) Complete and Parameter conversion: According to the cosine theorem, we can get ; (11) ; (12) Combining equations (5), (8) and (11), we can get ; (13) Equations (12) and (13) show that under certain steady-state conditions, and Only by the power angle Decide.
[0015] Preferably, the step S33 is specifically as follows: Substituting equations (11) and (12) into equation (3), we can obtain: ; (14) Will The working state of is called the minimum loss mode of the flexible distribution transformer; Can be launched The calculation formula is as follows: ; (15) From formula (15), the control parameters of the flexible distribution voltage regulator in S3 are: , the configuration parameters of the flexible distribution transformer described in S1 and the electrical parameters of the target line controlled by the flexible distribution transformer described in S2 can both be determined.
[0016] Preferably, in S4, the specific steps of outputting the regulated voltage of the flexible distribution transformer are as follows: S41: According to , the reference signal of the flexible distribution transformer load voltage control system is obtained, specifically: , ; S42: Based on The control loop feeds back the load voltage , and then through coordinate transformation we get and ; S43: In the synchronous coordinate system, the SPVW modulation signal is calculated using the PI controller; S44: Apply the SPVW modulation signal to ,use Real-time adjustments Output compensation voltage ,make and Real-time tracking of a given reference signal and , to offset the load voltage Fluctuations and asymmetry can be controlled to achieve load voltage control.
[0017] The present invention provides a flexible distribution transformer structure and an optimization control method thereof, which has the following beneficial effects: 1. The power angle optimization control strategy can achieve unity power factor control of grid-side current and stable load voltage control, thereby minimizing losses in the flexible distribution transformer and improving equipment operation efficiency. 2. The structure combines the advantages of traditional distribution transformers and power electronic converters. Conventional electromagnetic power transformers are responsible for full power conversion, while converters, which only account for about 10% of the capacity, are responsible for rapid and continuous regulation. This balances low cost, high reliability, and flexible regulation capabilities, meeting the voltage regulation requirements of new distribution networks. 3. By analyzing and optimizing parameters related to losses (copper loss and iron loss), the relationship between control parameters and variable losses was clarified, and precise control of losses was achieved, which is conducive to the efficient and low-carbon operation of equipment and is of great significance to the stable and reliable operation of new power systems. BRIEF DESCRIPTION OF THE DRAWINGS
[0018] The present invention will be further described below with reference to the accompanying drawings and embodiments: Figure 1 It is a structural schematic diagram of the present invention; Figure 2 is a flow chart of the method of the present invention; Figure 3 is a phasor relationship diagram of the flexible distribution transformer of the present invention; Figure 4 This is a block diagram of the control structure of the voltage regulation converter of the flexible distribution transformer of the present invention. DETAILED DESCRIPTION
[0019] like Figure 1 As shown, a flexible distribution transformer structure includes a main transformer , isolation transformer , energy-taking converter , voltage control converter and five windings , main transformer High voltage side primary winding Use delta connection and connect to the power grid; main transformer Low voltage side secondary winding The star connection with neutral point grounding is adopted, the winding side is connected to the load, and the neutral point side is connected to the voltage control converter. Through an isolation transformer Series connection; Isolation transformer The primary winding With the main transformer Low voltage side secondary winding The neutral point side is connected to the isolation transformer The secondary winding With voltage regulation converter Connected to; main transformer Low voltage side tertiary winding Use star connection with neutral point grounding and connect with energy converter Parallel; voltage-regulated converters and energy-extraction converters Coupling through DC capacitors; energy-taking converter Used to maintain DC capacitor voltage stability, voltage regulation converter Used to invert a voltage with freely adjustable amplitude and phase angle.
[0020] like Figure 2 As shown, a method for optimizing and controlling a flexible distribution transformer structure includes the following steps: S1: Obtaining configuration parameters of the flexible distribution transformer; S2: Acquire electrical parameters of the target line controlled by the flexible distribution transformer; S3: Calculating control parameters of the flexible distribution transformer according to the configuration parameters and electrical parameters; S4: Outputting the regulated voltage of the flexible distribution transformer to complete the optimized control of the flexible distribution transformer.
[0021] Preferably, the configuration parameters include: the turns ratio of the primary winding to the secondary winding of the main transformer, the turns ratio of the primary winding to the tertiary winding of the transformer, the turns ratio of the secondary winding to the tertiary winding of the transformer, the turns ratio of the primary winding to the secondary winding of the isolation transformer, the resistance of the tertiary winding of the main transformer, the excitation resistance of the isolation transformer, and the centralized equivalent resistance of the voltage-controlled converter.
[0022] Preferably, the electrical parameters include: the node input voltage of the target line, the node input current of the target line, the node input phase angle of the target line, the primary side rated voltage of the main transformer, the grid side rated voltage, the grid side voltage coefficient, and the preset target output voltage of the target line.
[0023] Preferably, the control parameters include: a d-axis component of a voltage reference signal injected into a target line, a q-axis component of a voltage reference signal injected into a target line, and a control voltage that a control converter of the flexible distribution transformer should output.
[0024] Preferably, step S3 includes the following steps: S31: Determine parameters related to operating losses in the flexible power distribution transformer; S32: Determine the relationship between the control parameters of the flexible distribution transformer and the variable loss related parameters; S33: Determine control parameters of the flexible distribution transformer.
[0025] Preferably, the step S31 is specifically as follows: The overall loss includes copper loss and iron loss; among them, iron loss includes The iron loss is recorded as ,and The iron loss is recorded as ; Copper loss includes 、 The copper loss of the circuit is recorded as ,and The copper loss of the circuit is recorded as ,as well as The copper loss of the circuit is recorded as ,and The copper loss of the circuit is recorded as Assuming three-phase symmetry, the total loss of the flexible distribution transformer is ,but ; (1) ; (2) Where, for Wirewound resistor; for The concentrated equivalent resistance; express The magnetizing resistance of the three-phase circuit is symmetrical, so the subscripts of the three-phase quantities can be omitted.
[0026] The basic operating requirement of the flexible distribution transformer is to compensate the grid side to unity power factor and control the load voltage to the rated voltage. Under certain steady-state conditions, are fixed, so is approximately fixed, and and Needs to be optimized.
[0027] Let the variable loss of the flexible distribution transformer be ,but ; (3) In the formula, the fixed quantity can be considered as a constant. is an equivalent constant; From formula (3), we can get that the parameters related to variable loss are: the current of the tertiary winding of the main transformer , the voltage of the primary winding of the isolation transformer , Main transformer tertiary winding resistance , the excitation resistance of the isolation transformer and the concentrated equivalent resistance of the voltage-regulated converter .
[0028] The current of the main transformer's tertiary winding The voltage of the primary winding of the isolation transformer The present invention performs parameter conversion according to the actual operation of the distribution transformer.
[0029] Preferably, the specific steps of step S32 are as follows: 1) Calculate the transformer winding: neglect and According to the principle of magnetic potential balance, the excitation current can be obtained as follows: ; (4) Where, They are The effective value phasor of is the number of turns of 5 windings; Will The variables in side, and will The variables in the On the other hand, formula (4) can be transformed into: ; (5) 2) Determine the relationship between load voltage, grid voltage and parameters related to variable losses: According to the circuit principle, we can get: (6) definition is the phase angle at which the load current leads the load voltage, is the power angle of the grid voltage lagging the load voltage. Taking the load voltage as the reference phasor, the phasor relationship between the voltage and current of the flexible distribution transformer under steady-state operation is as follows: Figure 3 shown.
[0030] 3) According to the actual operation of the distribution transformer, the parameter conversion conditions are obtained: After the flexible distribution transformer enters the steady-state condition, is controlled to an amplitude equal to its rated voltage The sine wave, at this time middle Rated voltage Approximately the grid-side rated voltage Equal, that is ,but Rated voltage ; The active power input from the grid side of the flexible distribution transformer must be equal to the active power absorbed by its load, so the following formula holds: ; (7) Available ; (8) The variables in formula (6) are converted to Side, then ; (9) During normal operation of the flexible distribution transformer, Often around its rated value Up and down fluctuations, thus ; (10) Where, is the grid-side voltage fluctuation coefficient; 4) Complete and Parameter conversion: According to the cosine theorem, we can get ; (11) ; (12) Combining equations (5), (8) and (11), we can get ; (13) Equations (12) and (13) show that under certain steady-state conditions, and Only by the power angle Decide.
[0031] Preferably, the step S33 is specifically as follows: Substituting equations (11) and (12) into equation (3), we can obtain: ; (14) Will The working state of is called the minimum loss mode of the flexible distribution transformer; Can be launched The calculation formula is as follows: ; (15) From formula (15), the control parameters of the flexible distribution voltage regulator in S3 are: , the configuration parameters of the flexible distribution transformer described in S1 and the electrical parameters of the target line controlled by the flexible distribution transformer described in S2 can both be determined.
[0032] In S4, the voltage regulation function of the flexible distribution transformer mainly relies on Output compensation voltage accomplish, The control strategy of Figure 4 shown.
[0033] Preferably, in S4, the specific steps of outputting the regulated voltage of the flexible distribution transformer are as follows: S41: According to , the reference signal of the flexible distribution transformer load voltage control system is obtained, specifically: , ; S42: Based on The control loop feeds back the load voltage , and then through coordinate transformation we get and ; S43: In the synchronous coordinate system, the SPVW modulation signal is calculated using the PI controller; S44: Apply the SPVW modulation signal to ,use Real-time adjustments Output compensation voltage ,make and Real-time tracking of a given reference signal and , to offset the load voltage Fluctuations and asymmetry can be controlled to achieve load voltage control.
[0034] As the core equipment of the power system, the flexible transformation and loss reduction of the transformer have a profound impact on the efficient, low-carbon and flexible operation of the new power system. With its advantages of fast, continuous and flexible voltage regulation, the flexible distribution transformer has become a key equipment to support the access of a high proportion of renewable energy and the upgrade of the distribution network. Accurately analyzing its loss characteristics and optimizing the operation strategy based on this is of great significance to improving equipment efficiency, extending life and ensuring system reliability. The present invention proposes a configuration scheme and optimization control method for a flexible distribution transformer. By adopting the power angle optimization control strategy proposed in the present invention, the flexible distribution transformer can achieve minimum loss on the basis of achieving unity power factor control of grid-side current and stable control of load voltage.
[0035] The above embodiments are merely preferred technical solutions of the present invention and should not be construed as limiting the present invention. The scope of protection of the present invention shall be the technical solutions set forth in the claims, including equivalent alternatives to the technical features of the technical solutions set forth in the claims. In other words, equivalent alternatives and improvements within this scope are also within the scope of protection of the present invention.
Claims
1. A flexible distribution transformer structure, characterized in that: Including main transformer , isolation transformer , energy-taking converter , voltage control converter and five windings , main transformer High voltage side primary winding Use delta connection and connect to the power grid; main transformer Low voltage side secondary winding The star connection with neutral point grounding is adopted, the winding side is connected to the load, and the neutral point side is connected to the voltage control converter. Through an isolation transformer Series connection; Isolation transformer The primary winding With the main transformer Low voltage side secondary winding The neutral point side is connected to the isolation transformer The secondary winding With voltage regulation converter Connected to; main transformer Low voltage side tertiary winding Use star connection with neutral point grounding and connect with energy converter Parallel; voltage-regulated converters and energy-extraction converters Coupling through DC capacitors; energy-taking converter Used to maintain DC capacitor voltage stability, voltage regulation converter Used to invert a voltage with freely adjustable amplitude and phase angle.
2. The optimization control method for a flexible distribution transformer structure according to claim 1, characterized in that: The following steps are involved: S1: Obtaining configuration parameters of the flexible distribution transformer; S2: Acquire electrical parameters of the target line controlled by the flexible distribution transformer; S3: Calculating control parameters of the flexible distribution transformer according to the configuration parameters and electrical parameters; S4: Outputting the regulated voltage of the flexible distribution transformer to complete the optimized control of the flexible distribution transformer.
3. The optimization control method for a flexible distribution transformer structure according to claim 2, characterized in that: The configuration parameters include: the turns ratio of the primary winding to the secondary winding of the main transformer, the turns ratio of the primary winding to the tertiary winding of the transformer, the turns ratio of the secondary winding to the tertiary winding of the transformer, the turns ratio of the primary winding to the secondary winding of the isolation transformer, the resistance of the tertiary winding of the main transformer, the excitation resistance of the isolation transformer, and the centralized equivalent resistance of the voltage-controlled converter.
4. The optimization control method for a flexible distribution transformer structure according to claim 2, characterized in that: The electrical parameters include: node input voltage of the target line, node input current of the target line, node input phase angle of the target line, primary side rated voltage of the main transformer, grid side rated voltage, grid side voltage coefficient, and preset target output voltage of the target line.
5. The optimization control method for a flexible distribution transformer structure according to claim 2, characterized in that: The control parameters include: a d-axis component of a voltage reference signal injected into a target line, a q-axis component of a voltage reference signal injected into a target line, and a regulated voltage that should be output by a regulated converter of the flexible distribution transformer.
6. The optimization control method for a flexible distribution transformer structure according to claim 5, characterized in that: The step S3 comprises the following steps: S31: Determine parameters related to operating losses in the flexible power distribution transformer; S32: Determine the relationship between the control parameters of the flexible distribution transformer and the variable loss related parameters; S33: Determine control parameters of the flexible distribution transformer.
7. The optimization control method for a flexible distribution transformer structure according to claim 6, characterized in that: The step S31 is specifically as follows: The overall loss includes copper loss and iron loss; among them, iron loss includes The iron loss is recorded as ,and The iron loss is recorded as ; Copper loss includes 、 The copper loss of the circuit is recorded as ,and The copper loss of the circuit is recorded as ,as well as The copper loss of the circuit is recorded as ,and The copper loss of the circuit is recorded as Assuming three-phase symmetry, the total loss of the flexible distribution transformer is ,but ；（1） ；（2） Where, for Wirewound resistor; for The concentrated equivalent resistance; express The exciting resistance; Let the variable loss of the flexible distribution transformer be ,but ；（3） In the formula, the fixed quantity can be considered as a constant. is an equivalent constant; From formula (3), we can get that the parameters related to variable loss are: the current of the tertiary winding of the main transformer , the voltage of the primary winding of the isolation transformer , Main transformer tertiary winding resistance , the excitation resistance of the isolation transformer and the concentrated equivalent resistance of the voltage-regulated converter .
8. The optimization control method for a flexible distribution transformer structure according to claim 7, characterized in that: The specific steps of step S32 are as follows: 1) Calculate the transformer winding: neglect and According to the principle of magnetic potential balance, the excitation current can be obtained as follows: ；（4） Where, They are The effective value phasor of is the number of turns of 5 windings; Will The variables in the side, and will The variables in the On the other hand, formula (4) can be transformed into: ；（5） 2) Determine the relationship between load voltage, grid voltage and parameters related to variable losses: According to the circuit principle, we can get: （6） 3) According to the actual operation of the distribution transformer, the parameter conversion conditions are obtained: After the flexible distribution transformer enters the steady-state condition, is controlled to an amplitude equal to its rated voltage The sine wave, at this time middle Rated voltage Approximately the grid-side rated voltage Equal, that is ,but Rated voltage ; The active power input from the grid side of the flexible distribution transformer must be equal to the active power absorbed by its load, so the following formula holds: ；（7） Available ；（8） The variables in formula (6) are converted to Side, then ； （9） During normal operation of the flexible distribution transformer, Often around its rated value Up and down fluctuations, thus ； （10） Where, is the grid-side voltage fluctuation coefficient; 4) Complete and Parameter conversion: According to the cosine theorem, we can get ；（11） ；（12） Combining equations (5), (8) and (11), we can get ； （13） Equations (12) and (13) show that under certain steady-state conditions, and Only by the power angle Decide.
9. The optimization control method for a flexible distribution transformer structure according to claim 8, characterized in that: The step S33 is specifically as follows: Substituting equations (11) and (12) into equation (3), we can obtain: ； （14） Will The working state of is called the minimum loss mode of the flexible distribution transformer; Can be launched The calculation formula is as follows: ； （15） From formula (15), the control parameters of the flexible distribution voltage regulator in S3 are: , the configuration parameters of the flexible distribution transformer described in S1 and the electrical parameters of the target line controlled by the flexible distribution transformer described in S2 can both be determined.
10. The optimization control method for a flexible distribution transformer structure according to claim 9, characterized in that: In S4, the specific steps of outputting the regulated voltage of the flexible distribution transformer are as follows: S41: According to , the reference signal of the flexible distribution transformer load voltage control system is obtained, specifically: , ; S42: Based on The control loop feeds back the load voltage , and then through coordinate transformation we get and ; S43: In the synchronous coordinate system, the SPVW modulation signal is calculated using the PI controller; S44: Apply the SPVW modulation signal to ,use Real-time adjustments Output compensation voltage ,make and Real-time tracking of a given reference signal and , to offset the load voltage Fluctuations and asymmetry can be controlled to achieve load voltage control.