Low-loss intelligent transformer system and transformer for energy-saving optimization in light-load operation

Abstract

The present application relates to a low-loss intelligent transformer system and transformer for energy saving optimization of light-load operation. The system comprises a transformer body, an auxiliary excitation winding, a light-load identification module and a magnetic excitation control module. When it is detected that the transformer is in a light-load state, the control module periodically injects a low-amplitude, short-time-width excitation pulse signal into the auxiliary excitation winding, so as to break the state that the core magnetic flux stays in the low magnetic density area of the hysteresis loop for a long time, improve the magnetic flux response linearity, suppress harmonic distortion and improve the light-load operation efficiency. The system adopts an independent structure design, has a small duty ratio and low energy consumption, has a control closed loop, self-adaptive exit and retrofit compatibility, and is suitable for new and retrofitted energy-saving distribution transformers.

Description

Technical Field

[0001] This invention belongs to the field of transformer technology, specifically a low-loss intelligent transformer system and transformer optimized for energy saving under light load operation. Background Technology

[0002] Distribution transformers are key energy conversion and distribution units in power systems, and their operating efficiency directly affects the energy consumption level of the power supply system. In practical applications, the operating load of transformers is significantly affected by seasonal, time-period, and regional demand changes. Especially in scenarios such as urban buildings, industrial parks, and data centers, it has become a common phenomenon for transformers to operate under light load conditions far below their rated load for extended periods.

[0003] Traditional transformer energy-saving optimization methods typically focus on the following aspects: selecting low-loss magnetic materials to reduce iron losses, achieving energy savings in the no-load section through grouped windings or automatic switching devices, and improving winding wiring structure to enhance thermal stability. These strategies mostly revolve around the three elements of "voltage-current-power," with the main goal of reducing system power loss or improving operating efficiency.

[0004] However, under light load conditions, there is a hidden problem that is widely overlooked but has a substantial impact on system performance—the potential for "low excitation saturation" caused by core magnetic flux density shift.

[0005] When a transformer operates under light or very light load conditions for an extended period, the main winding current decreases and the magnetomotive force weakens, leading to a significant reduction in the average magnetic flux density borne by the core. At this point, its operating point will approach the low-excitation section (initial steep region) of the hysteresis loop. In this region, the permeability changes unstably, and the hysteresis phenomenon intensifies, easily inducing nonlinear distortion of the magnetic flux response, the so-called "low-excitation saturation." This will lead to the following consequences:

[0006] The magnetic flux response hysteresis region expands, and the magnetic flux generated by the input current in the iron core no longer responds linearly, affecting the stability of voltage regulation.

[0007] Increased current distortion causes the normally stable output current waveform to become distorted and harmonic content to increase under light load, thus damaging power quality.

[0008] The system efficiency deteriorates; even with a light load, the loss ratio per unit output power increases, resulting in "inefficient operation".

[0009] Abnormal localized heating in the iron core, frequent fluctuations in local magnetic flux density, and the tendency to generate hot spots can negatively impact the lifespan of the iron core in the long run.

[0010] Traditional technologies often interpret "magnetic saturation" as an upper limit issue under high load or strong excitation, typically focusing only on preventing the core from entering the saturation magnetic region (i.e., the high magnetic flux density region), while neglecting the adverse effects of being in a low magnetic flux density region for extended periods. Especially under automatic voltage regulation or no-load energy-saving control strategies, this low excitation problem is often misjudged as "light load, low loss, no need for intervention," thus lacking corresponding identification and compensation mechanisms.

[0011] With the development of energy-saving power grids and distributed distribution systems, the number of transformers operating under light loads for extended periods is increasing. The problem of "latent magnetic hysteresis distortion" in the system is becoming more and more common. In severe cases, it can even interfere with harmonic filters and affect the accuracy of power factor compensation, becoming a non-obvious bottleneck that restricts the high-quality operation of smart grids.

[0012] Therefore, there is an urgent need for a transformer energy-saving operation mechanism that can actively harmonize the magnetic state of the iron core under light load conditions, get rid of the low excitation nonlinear hysteresis region, and keep the iron core in the optimal range of magnetic flux response, thereby improving system efficiency and power quality from the perspective of magnetic response. Summary of the Invention

[0013] The purpose of this invention is to provide a low-loss intelligent transformer system and transformer optimized for energy saving under light load operation. This invention not only fundamentally solves the problem of core magnetic state imbalance under light load operation, but also takes into account energy saving effect, power quality, structural compatibility and system control energy consumption. It has significant technological progress and application value, and has broad practical prospects in smart grid, high-efficiency power distribution and green power consumption scenarios.

[0014] The technical solution adopted in this invention is as follows:

[0015] Low-loss intelligent transformer systems optimized for energy saving during light-load operation include:

[0016] A transformer body consists of an iron core, a primary winding, and a secondary winding;

[0017] An auxiliary excitation winding is provided on the magnetic flux path of the iron core and is electromagnetically isolated from the primary winding and the secondary winding.

[0018] A magnetic excitation control module is used to periodically apply excitation pulse signals to the auxiliary excitation winding when the transformer is in a light-load operating state, so as to avoid the iron core being in a low magnetic flux density operating point for a long time and improve the linearity of magnetic flux response.

[0019] A light load identification module is used to collect transformer output current and load status information in real time, and when it is determined that the output current is lower than the set threshold and the duration exceeds the preset time, it sends an excitation enable signal to the magnetic excitation control module.

[0020] The excitation pulse signal output by the magnetic excitation control module is a low-amplitude, short-duration, symmetrical waveform pulse with a frequency of less than 1 Hz and a duty cycle of less than 5%.

[0021] The auxiliary excitation winding has 100 to 200 turns, a wire diameter of 0.3 to 0.5 mm, and an insulation class of not less than F.

[0022] The magnetic excitation control module includes a microcontroller unit, a PWM control circuit, an isolation drive circuit, and a power switch module. The PWM control circuit controls the power switch module to output pulses to the auxiliary excitation winding according to a set waveform.

[0023] The light load identification module is equipped with a current transformer to collect the secondary current signal and determine whether it has entered a light load state based on a set threshold and duration.

[0024] The magnetic excitation control module also includes a zero-crossing synchronization unit, which is used to trigger the output of excitation pulses when the transformer output voltage is near the zero-crossing point.

[0025] The excitation pulse waveform is a bidirectional sawtooth wave or a positive and negative symmetrical square wave with a pulse width of less than 10ms and a peak voltage of 12-24V.

[0026] The magnetic excitation control module and the transformer body are independently packaged and connected to the auxiliary excitation winding via quick connectors.

[0027] The auxiliary excitation winding is attached to the surface of the core support leg via a bonding structure, allowing for installation without disassembling the main winding, making it suitable for energy-saving retrofits of existing transformers.

[0028] A magnetic state harmonization method for a low-loss smart transformer optimized for energy saving under light load operation, applied to the aforementioned system, includes the following steps:

[0029] S1: Real-time acquisition of transformer output current to determine whether it is under light load;

[0030] S2: If the light load condition is met, the magnetic excitation control module is triggered to output an excitation pulse with a set waveform;

[0031] S3: Inject the excitation pulse into the auxiliary excitation winding to disturb the magnetic state of the iron core and avoid the magnetic flux operating point being in the low magnetic density section of the hysteresis loop;

[0032] S4: Continuously monitor the load status. When the load recovers to above the set threshold, stop the excitation pulse output and return to normal working mode.

[0033] A transformer that utilizes the low-loss intelligent transformer system described above.

[0034] The beneficial effects of this invention include:

[0035] This invention addresses the technical challenges of core magnetic flux density shift, enhanced magnetic flux response hysteresis, and degraded power quality in distribution transformers under long-term light load conditions. It proposes a magnetic state harmonization mechanism based on auxiliary excitation pulse compensation. Through an independently structured auxiliary excitation winding and low-energy-consumption excitation control logic, the working magnetic state of the core is actively optimized without changing the main circuit structure, thereby improving the overall efficiency and stability of the transformer under light load operation.

[0036] Unlike existing energy-saving methods that rely solely on electrical control measures such as iron loss optimization, turns ratio adjustment, or group switching, this invention, for the first time, focuses on the nonlinear distortion behavior of the iron core in the low magnetic flux density operating range, starting from the magnetic response itself. It proposes a closed-loop control method of "light load identification - magnetic disturbance excitation - operating point harmonization - automatic exit", which significantly suppresses the hidden problems such as harmonic amplification, current distortion, and system energy efficiency reduction caused by magnetic permeability instability during light load operation.

[0037] By setting auxiliary excitation windings on the iron core legs, and periodically injecting positive and negative symmetrical low-amplitude pulse signals into the system after it is determined to be under light load, the state in which the iron core has been stuck in the low excitation region of the hysteresis loop for a long time can be forcibly broken, so that its magnetic flux operating point returns to the linear response range. This reduces hysteresis distortion, smooths magnetic flux changes, and significantly improves the total harmonic distortion (THD) of the output current waveform, effectively improving power quality.

[0038] The excitation mechanism employed in this invention features a small duty cycle, low frequency, and extremely low power consumption. Its control logic can be independently packaged, offering strong adaptability. It is suitable for the integrated design of new energy-saving transformers and also facilitates non-intrusive energy-saving retrofits of existing distribution transformers. Its auxiliary winding does not require interference with the main winding structure, simplifying installation and reducing engineering implementation costs.

[0039] Furthermore, the system's excitation behavior is triggered only when the light load judgment condition is met, and it automatically terminates after the load is restored, ensuring a clear and reliable control closed loop. Combining zero-crossing detection and hysteresis protection mechanisms can further improve the synchronization and stability of the excitation, avoiding false excitation and magnetic flux disturbance misalignment problems.

[0040] In summary, this invention not only fundamentally solves the problem of core magnetic state imbalance under light load operation of transformers, but also takes into account energy saving effect, power quality, structural compatibility and system control energy consumption. It has significant technological progress and application value, and has broad practical prospects in smart grid, high-efficiency power distribution and green power consumption scenarios. Attached Figure Description

[0041] Figure 1 This is a schematic diagram of the transformer system of the present invention;

[0042] Figure 2 This is a schematic diagram of the transformer system architecture in Embodiment 1 of the present invention;

[0043] Figure 3 This is a flowchart illustrating the magnetic state harmonization method of Embodiment 1 of the present invention;

[0044] Figure 4 This is a flowchart illustrating Embodiment 2 of the present invention;

[0045] Figure 5 This is a flowchart illustrating Embodiment 3 of the present invention.

[0046] In the diagram, 1 is the transformer body; 11 is the iron core; 12 is the primary winding; 13 is the secondary winding; 14 is the support leg; and 2 is the auxiliary excitation winding. Detailed Implementation

[0047] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0048] Example 1: See Figure 1 This embodiment discloses a low-loss intelligent transformer system optimized for energy saving during light-load operation, including:

[0049] A transformer body 1 has an iron core 11, a primary winding 12 and a secondary winding 13;

[0050] An auxiliary excitation winding 2 is disposed on the magnetic flux path of the iron core 11 and is electromagnetically isolated from the primary winding 12 and the secondary winding 13. Specifically, it is disposed on the support leg 14 of the magnetic flux path of the iron core 11 and is used to receive the magnetic excitation pulse signal output by the system control module. The auxiliary excitation winding 2 has 100 to 200 turns, a wire diameter of 0.3 to 0.5 mm, and an insulation class not lower than F.

[0051] A magnetic excitation control module is provided to periodically apply excitation pulse signals to the auxiliary excitation winding when the transformer is under light load operation, in order to avoid the core being at a low magnetic flux density operating point for a long time and to improve the linearity of the magnetic flux response. The magnetic excitation control module includes a microcontroller unit, a PWM control circuit, an isolation drive circuit, and a power switch module. The PWM control circuit controls the power switch module to output pulses to the auxiliary excitation winding according to a set waveform. The magnetic excitation control module also includes a zero-crossing synchronization unit, which is used to trigger the output of the excitation pulse when the transformer output voltage is near the zero-crossing point. The excitation pulse waveform is a bidirectional sawtooth wave or a positive and negative symmetrical square wave, with a pulse width of less than 10ms and a peak voltage of 12-24V. The excitation pulse signal output by the magnetic excitation control module is a low-amplitude, short-duration, symmetrical waveform pulse with a frequency of less than 1Hz and a duty cycle of less than 5%.

[0052] A light load identification module is used to collect transformer output current and load status information in real time, and when it is determined that the output current is lower than a set threshold and the duration exceeds a preset time, it sends an excitation enable signal to the magnetic excitation control module; the light load identification module is equipped with a current transformer to collect secondary current signal, and determines whether it has entered a light load state according to the set threshold and duration.

[0053] Furthermore, the magnetic excitation control module and the transformer body adopt an independent packaging structure and are connected to the auxiliary excitation winding through quick connectors.

[0054] Furthermore, the auxiliary excitation winding is attached to the surface of the core support leg via a bonding structure, allowing for installation without disassembling the main winding, making it suitable for energy-saving retrofits of existing transformers.

[0055] See Figure 2 and Figure 3 A magnetic state harmonization method for a low-loss smart transformer optimized for energy saving under light load operation, applied to the aforementioned system, includes the following steps:

[0056] S1: During system operation, the light-load state identification step is executed first. This step uses a current sampling module installed in the transformer's secondary output circuit to collect the output current signal in real time to determine whether the transformer is in a light-load operating state. The current sampling module can be a current transformer (CT), a shunt, or a Hall current sensor, used to obtain the sampled value of the secondary output current at time t. Its unit is ampere (A), which represents the actual output current of the transformer secondary side at time t.

[0057] The system controller uses a fixed sampling period right Periodic sampling is performed to form a continuous sliding judgment time window, and after each sampling, the current value is compared with the set light load current threshold. Comparison. The sampling period. The interval between two consecutive samples is measured in seconds (s), typically ranging from 1 to 5 seconds. The light load current threshold... This is a reference value set to determine whether the transformer has entered a light-load state. The unit is amperes (A), and it is usually set to the rated output current of the transformer. 10%~20%, that is:

[0058] ;

[0059] in, This is the output current of the transformer under rated operating conditions, measured in amperes (A), and its value is determined on the equipment nameplate or in the system design.

[0060] In multiple consecutive samplings, if the current output current All are below the threshold. And the cumulative duration of this state is not less than the preset minimum duration. At this time, the system can determine that the transformer is currently under light load. Among other things, The minimum duration required to determine a light-load condition is measured in seconds (s), with typical values ​​ranging from 300 to 600 seconds (i.e., 5 to 10 minutes), used to prevent misjudgments caused by short-term current fluctuations.

[0061] The mathematical logic of the light-load identification can be expressed as: when the following formula is satisfied,

[0062] ;

[0063] The system enters a light load assessment state. Among other things, This indicates that the continuous current is below the set threshold. The cumulative duration, in seconds (s), is calculated as follows:

[0064] ;

[0065] in, The number of samples within the sliding judgment window, satisfying... ,in Total window length (seconds); Let be a logical discriminant function, if the first... The output current of the next sample , then let ,otherwise The final cumulative This is the total effective time in the low current state.

[0066] For example, when the sampling period is set to seconds, light load current threshold set to The minimum duration is set to At a given time interval, the system must determine that the current value is below a threshold in 60 consecutive sampling judgments before entering the light load state. To avoid misjudgment due to short-term fluctuations, the system can monitor the sampled current. Perform moving average or median filtering to generate a smooth current signal. This further improves the stability of the judgment. Once the system confirms that it has entered a light-load state, it will activate the magnetic excitation module to execute the subsequent magnetic state harmonization process.

[0067] S2: Once the system determines that the transformer is in a light-load state based on step S1, step S2 is initiated, which is the excitation control triggering process. In this step, the light-load identification module sends an excitation enable signal to the magnetic excitation control module, triggering the execution of the magnetic state harmonization mechanism.

[0068] The magnetic excitation control module preferably employs an integrated microcontroller unit (MCU) for core control. This MCU pre-stores the control algorithm and parameter settings for the excitation pulse output. Upon receiving the excitation enable signal, it automatically outputs a low-amplitude pulse signal with periodic, short-duration characteristics according to the preset parameters. This excitation pulse is then applied to the auxiliary excitation winding by a power switching circuit driven by PWM control logic. The waveform parameters of the excitation pulse include frequency. Pulse width Peak voltage Duty cycle And waveform type, etc., are specifically defined as follows:

[0069] Excitation pulse frequency, measured in Hz, represents the number of excitation pulses injected per second. The recommended range is 0.2 ~ 1.0 Hz, preferably 0.5 Hz.

[0070] : Duration of a single excitation pulse, in milliseconds (ms), with a recommended range of 3 to 10 ms;

[0071] The peak voltage of the excitation pulse, measured in volts (V), is typically set to 12 ~ 24 V, and is determined based on the impedance of the auxiliary winding.

[0072] The excitation duty cycle is defined as:

[0073] ;

[0074] in, This indicates the proportion of pulses in one excitation cycle, and should satisfy the following condition: To ensure minimal system interference;

[0075] Waveform type: A positive and negative symmetrical square wave (bipolar) or a bidirectional sawtooth wave can be selected to create alternating disturbances in the magnetic circuit and improve the magnetic state excitation effect.

[0076] After generating the aforementioned pulse parameters, the system controller controls the switching of power switching devices such as MOSFETs or IGBTs via the isolation drive module to output the excitation pulse in the time domain and apply it to the auxiliary excitation winding. Because the pulse power is extremely low, the duty cycle is small, and the period is long, it will not cause significant interference to the main circuit power path of the system.

[0077] To further optimize the stability of magnetic disturbance control, the magnetic excitation control module can incorporate a zero-crossing synchronous trigger module, which detects the secondary voltage of the transformer. Does it meet the following zero-crossing criterion:

[0078] ;

[0079] That is, when the secondary voltage approaches zero in the AC cycle and the rate of voltage change also approaches zero, the system will delay for a preset time. (Recommended range: 1~3 ms), followed by the output excitation pulse. This method ensures that the magnetic excitation behavior occurs in the low-disturbance region of the AC cycle, minimizing the impact on the voltage waveform.

[0080] After each excitation, the controller will automatically enter the next cycle until the system determines in step S4 that it is exiting the light load state and then terminates the excitation output.

[0081] S3: After the excitation control module outputs the excitation pulse, proceed to step S3, which is to inject the excitation pulse into the auxiliary excitation winding set on the magnetic flux path of the transformer core, so as to realize the disturbance and dynamic harmonization of the magnetic state of the core.

[0082] The auxiliary excitation winding is a specially designed structure for this system. It is used to introduce periodic magnetic flux disturbances in the core by receiving excitation signals applied by the control module when the transformer is operating under light load. The auxiliary excitation winding is preferably wound in the non-main winding support area of ​​the core (e.g., the core support corresponding to the low-voltage side) to minimize electromagnetic coupling interference between it and the main winding.

[0083] The auxiliary excitation winding parameters are designed as follows: number of turns The total number of turns in the auxiliary winding is recommended to be 100-200 turns; wire diameter The recommended wire diameter for winding this circuit is 0.3~0.5 mm; Insulation class: not lower than Class F insulation to meet long-term operation and heat resistance requirements; DC resistance. The DC resistance of the auxiliary winding itself is typically 10~30 Ω (ohms), which is related to the length and cross-sectional area of ​​the conductor. Installation method: It can be attached or externally mounted, allowing for energy-saving retrofitting without disassembling the original transformer.

[0084] When the magnetic excitation control module outputs an excitation pulse according to the set parameters, its output terminal is connected to both ends of the auxiliary excitation winding through a drive circuit. At the instant the pulse is applied, an excitation current is generated in the auxiliary winding. The amplitude of this current can be approximately calculated using the following formula:

[0085] ;

[0086] in:

[0087] Excitation current (unit: A) is the instantaneous current injected into the auxiliary winding;

[0088] Peak voltage of the excitation pulse (unit: V), typically 12~24 V;

[0089] The resistance of the auxiliary excitation winding (unit: Ω) is usually 10~30 Ω.

[0090] The magnetic field generated by the excitation pulse acts on the entire magnetic flux loop through the iron core magnetic circuit. Under light load conditions, it breaks the static state of the iron core with low excitation and low magnetic density, causing its magnetic flux response to move from the initial steep region of the hysteresis loop to the linear segment, thereby improving the linearity of the magnetic flux response and reducing the magnetic distortion effect and energy loss caused by low magnetic density.

[0091] Unlike traditional methods of adjusting magnetic flux density (such as changing the input voltage or using new materials), this invention improves the magnetic flux stability and response speed of the core operating point without interfering with the main circuit power transmission through an auxiliary magnetic disturbance mechanism with independent structure and extremely low energy consumption.

[0092] In particular, because the excitation pulse duty cycle is extremely small (usually less than 5%) and the peak voltage is limited, this disturbance behavior has minimal impact on the temperature rise, current waveform and harmonics of the main system, and can operate for a long time.

[0093] In addition, to avoid magnetic flux accumulation caused by unidirectional magnetic bias, the excitation waveform output by the system is preferably a positive and negative symmetrical waveform, that is, positive and negative excitations are applied alternately within one cycle to achieve symmetrical control of magnetic flux disturbance, thereby effectively stabilizing the magnetic characteristics of the iron core.

[0094] S4: During the periodic injection of magnetic excitation pulses and the maintenance of core magnetic state harmony, the system continuously executes step S4, namely dynamic monitoring and exit judgment of load state, to determine whether to terminate the magnetic excitation process and return to normal operation mode.

[0095] The system controller continuously samples the transformer secondary output current during each excitation cycle. , compared with the initially set light load threshold A comparison is made. To prevent frequent start-stop of magnetic excitation control due to output current fluctuations, the system introduces hysteresis logic, i.e., setting an upper limit offset. This is used to construct the hysteresis interval of the judgment conditions, thereby enhancing the stability of the system response.

[0096] When the following recovery criteria are met:

[0097] ; , ;

[0098] Once the system determines that the transformer has exited the light load state and the load has returned to the medium or heavy load operating range, it can terminate the magnetic excitation control logic, shut down the excitation output, and allow the auxiliary excitation winding to enter a dormant state.

[0099] In practical engineering implementation, the system can Set to a fixed value, such as It can also be adaptively adjusted according to the fluctuation characteristics of the operating load. If a moving average filter (such as a sliding window filter) is used... Smoothing can further improve the accuracy of load recovery judgment.

[0100] Once the conditions are met, the magnetic excitation control module immediately stops outputting pulse signals to the auxiliary excitation winding, and the system returns to the unexcited state. At this time, the auxiliary excitation winding can be disconnected from the control circuit by a controllable switch or by automatic disconnection, entering standby or power-saving mode, and the system switches to normal operating conditions.

[0101] In addition, the system can be configured with forced exit protection logic, for example: when magnetic excitation has been running continuously for more than the set maximum working time. If load recovery is not triggered within 30 minutes (e.g.), the excitation process can be actively paused to prevent the system from being falsely excited for a long time, thus avoiding resource waste.

[0102] The following is a "Comparative Test Table of Magnetic Disturbance Harmonization Performance of Light-Load Intelligent Transformers," which includes 6 sets of tests of the present invention under different parameters, and 2 sets of comparative tests of existing mainstream products (without excitation control mechanism). The parameters include auxiliary excitation winding design, excitation control parameters, and performance indicators (magnetic hysteresis width, induced interference rate, harmonic distortion rate), etc.

[0103]

[0104] Test prerequisites and conditions:

[0105] All prototypes were operated under the same input voltage (10kV) and light load conditions (secondary current less than 5A);

[0106] All data acquisition was performed after the excitation module had been working steadily for 10 minutes.

[0107] The test environment temperature was controlled at 25°C, and the harmonic test was completed using a standard THD analyzer.

[0108] in conclusion:

[0109] In the T1-T6 data sets of this invention, the configurations of auxiliary excitation turns between 120 and 200, pulse width of 5 to 10 ms, and frequency < 1 Hz significantly reduced the "magnetic response hysteresis zone" of the iron core (down to a minimum of 2.6%), which is a significant improvement compared to mainstream products (P1: 5.8%, P2: 6.2%).

[0110] In terms of controlling induced interference in the main and auxiliary windings, the present invention controls it to below 1.2%, while the interference rate of mainstream products without clamping structure is as high as 2.6%, proving that the clamping and RC damping design of the present invention effectively suppresses the propagation of magnetic interference.

[0111] Regarding harmonic distortion, mainstream products have a THD exceeding 3.0%, while this invention controls it below 1.5% across the entire group, with the best result being 1.0% in the T6 test.

[0112] This invention, through the coordinated control of magnetic excitation and disturbance stabilization structure under light load conditions, can effectively reduce the magnetic hysteresis response region, reduce electromagnetic interference and harmonic distortion, and is significantly superior to existing mainstream energy-saving distribution transformer products without excitation control. It is particularly suitable for urban ring networks, low-load substations and energy-saving renovation scenarios.

[0113] Example 2: See Figure 4 In this embodiment 2, the light load identification module in embodiment 1 is further optimized, and a light load threshold self-calibration mechanism based on magnetic hysteresis disturbance response is proposed. This mechanism aims to adapt to changes in different operating environments, core magnetic states and load characteristics, and improve the accuracy of light load identification and the intelligence level of the system.

[0114] Specifically, this embodiment adds a magnetic flux disturbance response unit and a parameter update module to the original light load identification module, and constructs the following operation flow:

[0115] 1) Standard excitation perturbation injection

[0116] During non-critical load periods (such as nighttime), the system controls the magnetic excitation control module to apply a standard excitation pulse signal to the auxiliary excitation winding. This signal is a symmetrical square wave or sawtooth wave, and its pulse parameters include:

[0117] Peak voltage: 12V~24V;

[0118] Pulse width: 5ms~10ms;

[0119] Excitation frequency: 0.5Hz;

[0120] The excitation duty cycle should not exceed 5%.

[0121] 2) Magnetic response voltage sampling

[0122] After the excitation pulse is applied, the induced voltage at the auxiliary excitation winding port is used as the magnetic disturbance response feedback signal, and the system records this induced voltage. The pullback characteristics include the following two parameters:

[0123] Peak voltage The first maximum value to appear after the disturbance;

[0124] steady-state voltage : The voltage remains stable after the disturbance subsides;

[0125] pullback time The time it takes for the induced voltage to drop from its peak value to a steady state, measured in seconds.

[0126] 3) Constructing the magnetic state response index

[0127] Based on the above measurement results, the system calculates the magnetic response index. , used to characterize the magnetic recovery capability of an iron core, is expressed as:

[0128] ;

[0129] in:

[0130] The unit is V / s;

[0131] The smaller the index, the slower the magnetic state recovers after the core disturbance, meaning the current magnetic state is more unstable, and the system should enter the light load judgment earlier.

[0132] 4) Adjust the light load threshold

[0133] Based on the magnetic response index, the system adjusts the current threshold for light load judgment in real time. The adjustment formula is as follows:

[0134] ;

[0135] in: The rated output current of the transformer (in amperes); The baseline coefficient, preferably ranging from 0.08 to 0.15; Adjustment factor, preferably ranging from 0.01 to 0.05; : Magnetic state response index, typically ranging from 0.5 to 3 V / s.

[0136] To avoid misjudgment due to a single disturbance, the system can... The values ​​are processed using a moving average (e.g., averaging the last 5 values), while limiting the threshold adjustment range to no more than ±20% each time.

[0137] 5) Parameter Update and Application

[0138] The revised Automatically write to the light load identification module and replace the original fixed threshold in the subsequent light load state identification logic. Combined with the continuously running output current sampling mechanism, it realizes dynamic and adaptive light load judgment.

[0139] This embodiment, without changing the original auxiliary excitation structure and excitation control logic, cleverly constructs a passive energy stabilization subsystem by introducing a magnetic disturbance discharge and clamping structure based on RC damping and fast recovery diodes at the auxiliary excitation winding port. This effectively solves the hidden problems such as residual magnetic rebound, interference amplification, or inrush current induction caused by the excitation pulse.

[0140] Specifically, this structure can automatically absorb residual disturbance magnetic energy in the iron core after the magnetic excitation control module stops working, forming a unidirectional energy discharge path to prevent induced voltage spikes or oscillation signals from being fed back to the main and auxiliary windings or the control system. Current release is achieved through a damping resistor, transient absorption is completed by an energy-absorbing capacitor, and a fast recovery diode ensures that conduction only occurs when energy exceeds a set threshold, thereby achieving magnetic steady-state control that "only discharges residual magnetism without disturbing the main circuit."

[0141] Compared with existing technologies, this solution has the following significant advantages:

[0142] Improve system stability: effectively suppress voltage oscillations and secondary resonances in the auxiliary winding, and avoid electromagnetic interference caused by excitation;

[0143] Improve the quality of magnetic flux disturbance: ensure the closed-loop integrity of the excitation process and improve the linearity and consistency of the magnetic state harmonization of the iron core;

[0144] Enhance the electrical isolation safety of the main and auxiliary windings: eliminate harmonic currents or induced malfunctions that may be caused by residual magnetic feedback;

[0145] Simple structure and strong adaptability to modification: This mechanism is a pure hardware passive structure, which does not require software control and data interaction, and is suitable for new or existing transformer systems.

[0146] Low cost and high reliability: magnetic disturbance stabilization can be achieved with only general-purpose discrete components, without introducing complex integrated circuits, and is feasible for industrial application.

[0147] In summary, this embodiment not only makes up for the shortcomings of the original system in terms of pulse excitation stability, but also fully demonstrates the engineering advantages of compact structure, energy self-consistency, and control decoupling in its implementation path, and has outstanding practicality and promotion value.

[0148] Example 3:

[0149] See Figure 5 A passive magnetic energy leakage buffer branch is added between the auxiliary excitation winding and the magnetic excitation control module. It consists of an RC damping circuit and a unidirectional clamping diode to form a unidirectional energy leakage channel and realize the release of magnetic disturbance during the non-activation period.

[0150] The structure consists of the following components:

[0151] resistor R s Typical values ​​are 10~50Ω, used to limit leakage current;

[0152] Capacitor C s Typical values ​​are 1~10μF, used for transient energy absorption and hysteresis absorption;

[0153] Fast recovery diode D s Rated withstand voltage 100V, reverse recovery time <50ns, used to construct unidirectional conduction paths;

[0154] Branch connection method: R s With C s After being connected in series, it is connected in parallel across the two ends of the auxiliary excitation winding, D s With R s C s Connecting one end of the series circuit to ground forms a unidirectional clamping circuit.

[0155] Implementation process:

[0156] S1~S2 are the same as in Example 1.

[0157] S3': Residual magnetism release after excitation ends. After the magnetic excitation control module stops outputting pulse signals, the iron core may still have some residual disturbing magnetic flux. At this time, the auxiliary winding port voltage It may be slightly greater than zero. In this state:

[0158] like (Diode forward voltage drop)

[0159] Conduction, The circuit instantaneously absorbs the energy induced by magnetic disturbance;

[0160] exist Internal damping energy leakage curve is formed;

[0161] This energy is not fed back to the main control module or the power grid system to avoid false triggering or backflow.

[0162] Control constraints and parameters:

[0163] The diode reverse current must be less than 10μA to ensure that it does not mis-conduct during non-excitation period;

[0164] The RC parameters should meet the following requirements:

[0165] ;

[0166] That is, the damping time constant should be able to cover the duration of the main disturbance after the excitation pulse, ensuring that the release is complete but not lingering.

[0167] This embodiment effectively suppresses residual resonance of magnetic disturbance and improves the electromagnetic stability of the transformer under light load. It has a simple structure, requires no complex control logic, and works completely passively, making it suitable for promotion in new installations and retrofit systems. It also innovatively introduces a "magnetic disturbance clamping + unidirectional energy absorption" mechanism, and for the first time uses RC + fast recovery diodes to assist in the magnetic stability of the winding. It avoids misjudging the light load state or causing harmonic amplification in the system, effectively supporting the energy-saving optimization goal of this invention.

[0168] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A low-loss intelligent transformer system optimized for energy saving under light load operation, comprising a transformer body and a light load identification module, wherein the transformer body has an iron core, a primary winding, and a secondary winding, characterized in that: It also includes an auxiliary excitation winding that is completely electromagnetically isolated from the primary and secondary windings, and a magnetic excitation control module that is independently packaged with the transformer body. The auxiliary excitation winding is attached to the magnetic flux path of the transformer core support leg and shares the same core magnetic circuit with the primary and secondary windings. Installation can be completed without disassembling the primary and secondary main windings, making it suitable for energy-saving retrofitting of existing transformers. The auxiliary excitation winding has 100 to 200 turns, a wire diameter of 0.3 to 0.5 mm, and an insulation class of not less than F. The light load identification module is equipped with a current transformer, which collects the output current signal of the transformer secondary side in real time with a fixed sampling period of 1 to 5 seconds. After performing moving average or median filtering on the collected current signal, it performs steady-state light load judgment through a sliding time window: when the continuously sampled output current is lower than 10% to 20% of the transformer's rated output current, and the cumulative duration of the low current state reaches 300 to 600 seconds, it sends an excitation enable signal to the magnetic excitation control module; it continuously monitors the load status, and when the output current recovers to the light load judgment threshold and is superimposed with a hysteresis deviation threshold of 2% to 5% of the rated current, it sends a stop excitation signal to the magnetic excitation control module. The magnetic excitation control module is electrically connected to the auxiliary excitation winding via a quick connector. It includes a microcontroller unit, a PWM control circuit, an isolation drive circuit, a power switch module, and a zero-crossing synchronization unit. The magnetic excitation control module only starts working under light-load conditions when the transformer receives an excitation enable signal, and remains dormant under heavy-load conditions. When starting up, the transformer output voltage is first detected by the zero-crossing synchronization unit. When the voltage is detected to be near the zero-crossing point and the voltage change rate approaches zero, the power switch module is triggered after a delay of 1-3ms. The excitation pulse signal is periodically applied to the auxiliary excitation winding. The auxiliary excitation winding introduces periodic micro-amplitude magnetic flux disturbances in the iron core, forcibly breaking the magnetic domain pinning state in which the iron core magnetic flux has been stuck in the low magnetic density region of the hysteresis loop for a long time. This allows the iron core magnetic flux operating point to return to the linear response range of the hysteresis loop, reducing hysteresis distortion, smoothing magnetic flux changes, and reducing the iron loss and total harmonic distortion rate of the output current when the transformer is operating under light load. The excitation pulse signal output by the magnetic excitation control module is a bidirectional sawtooth wave or a positive and negative symmetrical square wave with a frequency of 0.2 to 1 Hz, a duty cycle of less than 5%, a pulse width of 3 to 10 ms, and a peak voltage of 12 to 24 V.

2. The system according to claim 1, characterized in that, The auxiliary excitation winding is wound in the non-main winding support leg area of ​​the iron core, with a DC resistance of 10 to 30 Ω, in order to minimize electromagnetic coupling interference with the main winding.

3. The system according to claim 1, characterized in that, The auxiliary excitation winding is connected in parallel with a passive magnetic energy leakage buffer branch. The passive magnetic energy leakage buffer branch is composed of an RC damping circuit and a unidirectional clamping fast recovery diode connected in series. It is used to absorb the residual disturbance magnetic energy of the iron core after the excitation pulse ends and suppress the residual resonance of the magnetic disturbance.

4. The system according to claim 3, characterized in that, The RC damping circuit includes a damping resistor and an energy-absorbing capacitor connected in series. The resistance of the damping resistor is 10 to 50 Ω, and the capacitance of the energy-absorbing capacitor is 1 to 10 μF. The rated withstand voltage of the unidirectional clamping fast recovery diode is not less than 100V, the reverse recovery time is less than 50 ns, and the reverse leakage current is less than 10 μA.

5. The system according to claim 1, characterized in that, The magnetic excitation control module is also equipped with a forced exit protection unit. When the excitation pulse runs continuously for more than 30 minutes without triggering load recovery, the excitation process is automatically paused and the module enters standby protection state.

6. A distribution transformer that applies the low-loss intelligent transformer system according to any one of claims 1 to 5.

7. A magnetic state harmonization method for a low-loss intelligent transformer optimized for energy saving under light load operation, applied to the system as described in claim 1, characterized in that, Includes the following steps: S1: Accurate identification of light load condition: The transformer secondary output current is collected in real time with a fixed sampling period of 1 to 5 seconds. After the collected current signal is processed by sliding average or median filtering, steady-state light load judgment is performed through a sliding time window. When the continuously sampled output current is lower than 10% to 20% of the transformer's rated output current, and the cumulative duration of this low current state reaches 300 to 600 seconds, it is determined to be a steady-state light load state. S2: Excitation control trigger: After determining that the state is a steady-state light load, the light load identification module sends an excitation enable signal to the magnetic excitation control module. The magnetic excitation control module wakes up from the dormant state and preloads the preset excitation pulse parameters. S3: Synchronous Magnetic State Harmonization: The transformer output voltage is detected by the zero-crossing synchronization unit. When the voltage is detected to be near the zero-crossing point and the voltage change rate approaches zero, the power switching module is triggered after a delay of 1-3ms. The excitation pulse signal is periodically applied to the auxiliary excitation winding. The auxiliary excitation winding introduces periodic micro-amplitude magnetic flux disturbance in the iron core, forcibly breaking the domain pinning state of the iron core magnetic flux, which has been stuck in the low magnetic density region of the hysteresis loop for a long time. This allows the iron core magnetic flux operating point to return to the linear response range of the hysteresis loop, reducing hysteresis distortion, smoothing magnetic flux changes, and reducing the iron loss and total harmonic distortion rate of the output current when the transformer is operating under light load. The excitation pulse signal is a bidirectional sawtooth wave or a positive and negative symmetrical square wave with a frequency of 0.2-1Hz, a duty cycle of less than 5%, a pulse width of 3-10ms, and a peak voltage of 12-24V. S4: Adaptive Exit Control: Continuously monitors the load status. When the output current recovers to above the light load judgment threshold and is superimposed with the hysteresis deviation threshold of 2% to 5% of the rated current, the excitation pulse output is immediately stopped, the magnetic excitation control module enters the sleep state, the auxiliary excitation winding stops working, and the transformer returns to the normal operation mode.

8. The method according to claim 7, characterized in that, In step S3, after the excitation pulse ends, the absorption and release of residual magnetic disturbance energy of the iron core is completed within 10ms through the passive magnetic energy leakage buffer branch connected in parallel at both ends of the auxiliary excitation winding, thereby suppressing residual magnetic disturbance resonance.

9. The method according to claim 7, characterized in that, In step S4, when the excitation pulse runs continuously for more than 30 minutes without triggering load recovery, the system automatically pauses the excitation process and enters standby protection state, and re-verifies the light load state after an interval of 10 minutes.

10. The method according to claim 7, characterized in that, In step S1, the system performs a light load threshold self-calibration process during non-critical load periods at night: injecting a standard excitation pulse signal into the auxiliary excitation winding, sampling the induced voltage drop characteristics of the auxiliary excitation winding, calculating the core magnetic state response index, and correcting the light load judgment current threshold in real time based on the magnetic state response index.

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