Solid-state distribution transformer control system and method for improving distributed power supply access

Abstract

The invention relates to the field of transformer control, and discloses a solid-state distribution transformer control system and method for improving access of a distributed power supply, which are used for solving the problem that original controller parameters are not representative due to access change of the distributed power supply when the solid-state distribution transformer is controlled. The method comprises the following steps: constructing a solid-state distribution transformer with a multi-port power regulation capability, setting initial control parameters, obtaining equivalent impedance influenced data, evaluating according to the equivalent impedance influenced data to obtain an equivalent impedance change index, judging whether the equivalent impedance is changed according to the equivalent impedance change index, and if the equivalent impedance is judged to be changed, judging whether the equivalent impedance is changed or not. If yes, dynamically correcting the initial control parameter according to the equivalent impedance change index to obtain an actual control parameter, and adjusting the output of the solid-state transformer according to the actual control parameter, thereby effectively improving the accuracy of transformer control and the reliability of energy supply.

Description

Technical Field

[0001] The present invention relates to the field of transformer control, and more particularly to a solid-state distribution transformer control system and method for improving the access of distributed power sources. Background Art

[0002] With the large-scale development of renewable energy, distributed power sources are gradually widely connected to the distribution network. To achieve the flexible access and efficient energy utilization of distributed power sources, as a new generation of power electronic transformer equipment, solid-state distribution transformers are widely used in scenarios such as regional distribution networks, microgrids, and campus energy systems. Solid-state distribution transformers integrate functions such as high-frequency voltage transformation, voltage regulation, and energy flow control. They not only have the ability to stabilize voltage but also support two-way power flow regulation and power decoupling, becoming one of the core equipments to support the access of a high proportion of distributed power sources.

[0003] To improve its control accuracy and system stability, existing technologies usually adopt a control parameter configuration method based on a static topology model. In this type of method, when the system is initially deployed, parameters such as the grid topology structure, line impedance, and cable length are pre-calibrated, and the controller parameters are fixed at specific set values to meet the steady-state control objectives in the set scenarios.

[0004] However, the above technologies have at least the following technical problems:

[0005] In the actual operating environment, the distribution network structure where the solid-state distribution transformer is located usually has high dynamics, typically manifested as the frequent access and withdrawal of distributed power sources, changes in cable length, switching of power access positions, and feeder topology reconstruction. These factors will directly change the equivalent impedance of the local network, resulting in the mismatch between the adjustment amount obtained by the internal controller of the solid-state distribution transformer based on the static controller parameters and the actual system state. This not only reduces the accuracy of voltage regulation and power control but may even cause problems such as power oscillation, power quality fluctuation, false touch protection, or abnormal disconnection of distributed power sources, seriously affecting the system stability and power supply reliability. Summary of the Invention

[0006] To overcome the above defects of the prior art, the present invention provides a solid-state distribution transformer control system and method for improving the access of distributed power sources to solve the problems existing in the above background art.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] A control system for a solid-state distribution transformer that improves the access of distributed power sources. The system includes: a solid-state distribution transformer construction module for constructing a solid-state distribution transformer with multi-port power regulation capabilities and setting initial control parameters for the solid-state distribution transformer; an equivalent impedance change evaluation module for obtaining data affected by the equivalent impedance, where the data affected by the equivalent impedance includes the actual output voltage sequence, the actual output current sequence, the reference target voltage sequence, the controller output quantity sequence, and the actual output power sequence, evaluating the equivalent impedance change index based on the data affected by the equivalent impedance, and determining whether the equivalent impedance has changed based on the equivalent impedance change index; a controller parameter dynamic adjustment module that, if it determines that the equivalent impedance has changed, dynamically corrects the initial control parameters according to the equivalent impedance change index to obtain the actual control parameters; a power quality guarantee and regulation execution module for adjusting the output of the solid-state transformer according to the actual control parameters; and a data upload and remote monitoring module for uploading the control parameter adjustment records and real-time operation status data to a database.

[0009] Preferably, the steps for constructing a solid-state distribution transformer with multi-port power regulation capabilities are as follows: construct a traditional double-winding power frequency transformer, where the double windings include a high-voltage side winding and a low-voltage side winding; connect a front-end converter to the high-voltage side group of the power frequency transformer and a rear-end converter to the low-voltage side group of the power frequency transformer to construct a three-phase four-leg structure; connect the DC sides of the front-end converter and the rear-end converter to form a common DC link and lead out a low-voltage DC port to form a three-port structure with a high-voltage AC input terminal, a low-voltage AC output terminal, and a low-voltage DC output terminal, thereby completing the construction of a solid-state distribution transformer with multi-port power regulation capabilities.

[0010] Preferably, the steps for obtaining the equivalent impedance change index are as follows: set a detection time window, perform periodic sampling within the detection time window, set the sampling frequency, and calculate the total number of sampling points based on the time window and the sampling frequency. Obtain the actual output voltage sequence and the actual output current sequence of the transformer within the detection time window, and evaluate the electrical response influence coefficient based on the output voltage sequence and the output current sequence; obtain the reference target voltage sequence and the controller output quantity sequence within the detection time window, and evaluate the control feedback influence coefficient based on the reference target voltage sequence, the actual output voltage sequence, and the controller output quantity sequence; obtain the actual output power sequence within the detection time window, and evaluate the behavior pattern influence coefficient based on the actual output power sequence and the actual output voltage sequence; normalize the electrical response influence coefficient, the control feedback influence coefficient, and the behavior pattern influence coefficient, and evaluate the equivalent impedance change index based on the normalized electrical response influence coefficient, control feedback influence coefficient, and behavior pattern influence coefficient. The specific obtaining steps are as follows: ; where is expressed as the equivalent impedance change index. is expressed as the electrical response influence coefficient after normalization processing, is expressed as the control feedback influence coefficient after normalization processing, is expressed as the behavior pattern influence coefficient after normalization processing, , , are expressed as the weight coefficient of the electrical response influence coefficient after normalization processing, the weight coefficient of the control feedback influence coefficient after normalization processing, and the weight coefficient of the behavior pattern influence coefficient after normalization processing.

[0011] Preferably, the step of obtaining the electrical response influence coefficient is as follows: within the detection time window, calculate the voltage mean value, current mean value, voltage standard deviation, and current standard deviation within the set time window according to the actual output voltage sequence and the actual output current sequence; calculate the ratio of the voltage standard deviation to the voltage mean value to obtain the voltage variation coefficient, and calculate the ratio of the current standard deviation to the current mean value to obtain the current variation coefficient; calculate the mean value after adding the voltage variation coefficient and the current variation coefficient to obtain the electrical response influence coefficient.

[0012] Preferably, the step of obtaining the control feedback influence coefficient is as follows: subtract the actual output voltage value in the actual output voltage sequence from the reference target voltage value in the reference target voltage sequence to obtain the voltage deviation value at each sampling point, calculate the ratio of the voltage deviation value to the reference target voltage value to obtain the residual deviation rate at each sampling point, and calculate the mean value of the residual deviation rate at each sampling point to obtain the normalized residual deviation rate; calculate the controller output mean value according to the controller output quantity sequence, calculate the ratio of the controller output mean value to the voltage deviation mean value and take the absolute value to obtain the residual misguidance rate; perform standardization processing on the two sets of sampling data in the reference target voltage sequence and the actual output voltage sequence respectively; use the enumeration method to shift one of the sets of data forward or backward by different numbers of time points one by one, calculate the matching degree, i.e., the cross-correlation value, between the two sets of standardized data at each translation position, and select the number of translation points corresponding to the maximum cross-correlation value, denoted as the cross-correlation peak delay points; calculate the ratio of the cross-correlation peak delay points to the total number of sampling points to obtain the residual lag rate; calculate the control feedback influence coefficient according to the normalized residual deviation rate, the residual misguidance rate, and the residual lag rate.

[0013] Preferably, the step of obtaining the behavior pattern influence coefficient is as follows: obtain the number of times the power change direction reverses according to the actual output power sequence, denoted as the power reversal times, calculate the ratio of the power reversal times to the total number of sampling points to obtain the reverse jump rate; set a voltage threshold window, obtain the number of times the output voltage value exceeds the voltage threshold window range within the detection time window, denoted as the out-of-bounds times, calculate the ratio of the out-of-bounds times to the total number of sampling points to obtain the out-of-bounds rate; calculate the actual output power change value and the actual output voltage change value between two adjacent sampling points according to the actual output power sequence and the actual output voltage sequence; calculate the relative change amplitude of the actual output power and the relative change amplitude of the actual output voltage at each sampling point respectively according to the actual output power change value and the actual output voltage change value between two adjacent sampling points; add the relative change amplitude of the actual output power and the relative change amplitude of the actual output voltage to obtain the instantaneous total fluctuation amplitude at each sampling point, and average the instantaneous total fluctuation amplitudes at all times to obtain the average behavior volatility; calculate the behavior pattern influence coefficient according to the reverse jump rate, the out-of-bounds rate and the average behavior volatility.

[0014] Preferably, the step of determining whether the equivalent impedance changes according to the equivalent impedance change index is as follows: compare the equivalent impedance change index with the change threshold. If the equivalent impedance change index is greater than or equal to the change threshold, it is determined that the equivalent impedance has changed; if the equivalent impedance change index is less than the change threshold, it is determined that the equivalent impedance has not changed.

[0015] Preferably, the step of dynamically correcting the initial control parameters according to the equivalent impedance change index to obtain the actual control parameters is as follows: obtain the average value of the effective voltage value and the average value of the effective current value within the detection time window, calculate the ratio of the average value of the effective voltage value to the average value of the effective current value to obtain the current equivalent impedance estimation value, obtain the output current value in real time, and calculate the product of the real-time output current value and the current equivalent impedance estimation value to obtain the voltage feedforward compensation amount; obtain the initial resistance value of the solid-state distribution transformer, calculate the ratio of the difference between the current equivalent impedance estimation value and the initial resistance value to the initial resistance value to obtain the resistance change rate; if the resistance change rate is greater than 0, it is determined that the resistance has increased, and calculate the ratio of the change threshold to the equivalent impedance change index; if the resistance change rate is less than 0, it is determined that the resistance has decreased, and calculate the ratio of the equivalent impedance change index to the change threshold; if the resistance change rate is equal to 0, it is determined that the resistance has not changed, and the initial control parameters are not corrected; calculate the product of the initial control parameters and the correction factor to obtain the actual control parameters.

[0016] Preferably, the step of adjusting the output of the solid-state transformer according to the actual control parameters is as follows: according to the actual control parameters, based on the target set value, construct a control reference signal, and collect the operation state data of the current solid-state distribution transformer in real time; calculate the difference between the currently collected operation state data and the reference signal to obtain a deviation signal, input the deviation into a PI controller to obtain a PI control output; synthesize the PI control output and the voltage feed-forward compensation amount to obtain a final control instruction; adjust the output of the solid-state transformer according to the final control instruction.

[0017] Preferably, the control method for a solid-state distribution transformer for enhancing the access of distributed power sources includes the following steps: Step 1: Construct a solid-state distribution transformer with multi-port power regulation capabilities and set the initial control parameters of the solid-state distribution transformer; Step 2: Obtain the data affected by the equivalent impedance, where the data affected by the equivalent impedance includes the actual output voltage sequence, the actual output current sequence, the reference target voltage sequence, the controller output quantity sequence, and the actual output power sequence, evaluate the equivalent impedance change index based on the data affected by the equivalent impedance, and determine whether the equivalent impedance has changed according to the equivalent impedance change index; Step 3: If it is determined that the equivalent impedance has changed, dynamically correct the initial control parameters according to the equivalent impedance change index to obtain the actual control parameters; Step 4: Adjust the output of the solid-state transformer according to the actual control parameters; Step 5: Upload the control parameter adjustment records and the real-time operation state data to the database.

[0018] The technical effects and advantages of the present invention:

[0019] Construct a solid-state distribution transformer with multi-port power regulation capabilities, set the initial control parameters, obtain the data affected by the equivalent impedance, evaluate the equivalent impedance change index based on the data affected by the equivalent impedance, determine whether the equivalent impedance has changed according to the equivalent impedance change index, if it is determined that the equivalent impedance has changed, dynamically correct the initial control parameters according to the equivalent impedance change index to obtain the actual control parameters, and adjust the output of the solid-state transformer according to the actual control parameters, effectively improving the accuracy of transformer control and the reliability of power supply. Description of the Drawings

[0020] Figure 1 It is a structural diagram of a control system for a solid-state distribution transformer for enhancing the access of distributed power sources provided by an embodiment of the present application.

[0021] Figure 2 It is a flowchart of a control method for a solid-state distribution transformer for enhancing the access of distributed power sources provided by an embodiment of the present application. Detailed Embodiments

[0022] The technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the present invention. In addition, the forms of the various structures described in the following embodiments are merely examples, and the solid-state distribution transformer control system and method for enhancing the access of distributed power sources involved in the present invention are not limited to the various structures described in the following embodiments. All other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0023] The present invention provides a solid-state distribution transformer control system for enhancing the access of distributed power sources, as Figure 1 shown, the system includes:

[0024] A solid-state distribution transformer construction module, configured to construct a solid-state distribution transformer with multi-port power regulation capabilities, and set the initial control parameters of the solid-state distribution transformer for supporting subsequent dynamic control and impedance identification functions;

[0025] The control parameters include voltage closed-loop PI gain, power regulation coefficient, feed-forward compensation term, etc., and are used to construct the basic control model of the system controller, providing a control starting point for subsequent identification of impedance changes and adaptive parameter adjustment.

[0026] In this embodiment, it should be specifically noted that the steps for constructing a solid-state distribution transformer with multi-port power regulation capabilities are as follows:

[0027] First, a traditional double-winding power frequency transformer is constructed as an electrical isolation unit for energy transmission. The double winding includes a high-voltage side winding and a low-voltage side winding, providing a stable basic voltage transformation function for the subsequent power electronic modules. This power frequency transformer is responsible for both the preliminary transformation of the voltage level and the energy isolation between the high and low voltage ends, providing physical support for multi-port regulation;

[0028] The front-end converter FEC is connected to the high-voltage side group of the power frequency transformer, adopting a three-phase four-wire system structure as a voltage regulation and stabilization module. The FEC is used to detect and compensate the voltage fluctuations and imbalances of the grid high-voltage bus, and as an actively controllable voltage source output unit, providing voltage support capabilities for the low-voltage side;

[0029] The back-end converter BEC is connected to the low-voltage side group of the power frequency transformer to construct a three-phase four-leg structure to support power quality regulation functions such as harmonic compensation, reactive power compensation, and zero-sequence compensation. At the same time, the BEC has bi-directional power regulation capabilities and can be linked with energy storage systems, DC loads, etc. to achieve smooth regulation of the fluctuations after the access of distributed power sources;

[0030] Connect the DC sides of the front-end converter and the back-end converter to form a common DC link, and lead out a low-voltage DC port to form a three-port structure with a high-voltage AC input terminal, a low-voltage AC output terminal, and a low-voltage DC output terminal, thereby completing the construction of a solid-state distribution transformer with multi-port power regulation capabilities.

[0031] An equivalent impedance change evaluation module for obtaining data affected by the equivalent impedance, where the data affected by the equivalent impedance includes the actual output voltage sequence, the actual output current sequence, the reference target voltage sequence, the controller output quantity sequence, and the actual output power sequence, evaluating the equivalent impedance change index based on the data affected by the equivalent impedance, and determining whether the equivalent impedance has changed according to the equivalent impedance change index;

[0032] In this embodiment, it should be specifically noted that the steps for obtaining the equivalent impedance change index are as follows:

[0033] Set a detection time window, perform periodic sampling within the detection time window, set the sampling frequency, and calculate the total number of sampling points based on the time window and the sampling frequency, obtain the actual output voltage sequence and the actual output current sequence of the transformer within the detection time window, and evaluate the electrical response influence coefficient based on the output voltage sequence and the output current sequence;

[0034] Obtain the reference target voltage sequence and the controller output quantity sequence within the detection time window, and evaluate the control feedback influence coefficient based on the reference target voltage sequence, the actual output voltage sequence, and the controller output quantity sequence;

[0035] Obtain the actual output power sequence within the detection time window, and evaluate the behavior pattern influence coefficient based on the actual output power sequence and the actual output voltage sequence;

[0036] Normalize the electrical response influence coefficient, the control feedback influence coefficient, and the behavior pattern influence coefficient, and evaluate the equivalent impedance change index based on the normalized electrical response influence coefficient, the control feedback influence coefficient, and the behavior pattern influence coefficient. The specific obtaining steps are as follows:

[0037] ;

[0038] In the formula, is expressed as the equivalent impedance change index, is expressed as the normalized electrical response influence coefficient. The change of the equivalent impedance will affect the stability and controllability of the electrical quantity against external disturbances, thus significantly increasing the variation coefficient of the voltage and current within the sampling window. By monitoring the relative fluctuation degree of the electrical response, it can be used as an important basis for judging the impedance change trend. Therefore, the higher this coefficient, the greater the possibility that the system impedance deviates from the initial state, ultimately driving the equivalent impedance change index to rise. Denoted as the control feedback influence coefficient after normalization processing. When the equivalent impedance of the system changes, the original control parameters will be difficult to accurately guide the voltage response, resulting in an increase in the deviation between the target voltage and the actual output, a weakening of the controller output's ability to guide errors, and an obvious lag in the response. These phenomena will increase indicators such as the normalization deviation, misguidance rate, and lag rate, and ultimately increase the control feedback influence coefficient. Therefore, the higher this coefficient, the worse the dynamic adaptability of the control closed-loop system, indicating that the system operating state has significantly deviated from the set impedance condition, thus reflecting a greater possibility of equivalent impedance change. Denoted as the behavior pattern influence coefficient after normalization processing. The change in equivalent impedance will disrupt the original load stability and voltage regulation balance, leading to frequent reversals of power changes, an increase in the number of voltage boundary crossings, and an exacerbation of the fluctuation amplitude per unit time, thus showing an enhanced instability in behavioral characteristics. The behavior pattern influence coefficient formed by comprehensively evaluating the reverse jump rate, boundary crossing rate, and average behavior volatility can be used as a sensitive response quantity to impedance changes at the system behavior level. The higher the coefficient, the more the system has deviated from the original operating state, and the greater the possibility of impedance change. 、 、 Denoted as the weight coefficient of the electrical response influence coefficient after normalization processing, the weight coefficient of the control feedback influence coefficient after normalization processing, and the weight coefficient of the behavior pattern influence coefficient after normalization processing, and For example 、 、 Can be 0.3, 0.4, 0.3. 、 、 Obtained through the analytic hierarchy process. The analytic hierarchy process is a multi-criteria decision-making method used to quantitatively assign weights to the importance among multiple evaluation factors by constructing a judgment matrix and performing a consistency test. In the present invention, for the three dimensions of the electrical response influence coefficient, the control feedback influence coefficient, and the behavior pattern influence coefficient, first, experts or historical operation data are used to give the relative importance evaluation between pairwise factors to construct a third-order pairwise comparison judgment matrix; then, the maximum eigenvector of the matrix is solved by the eigenvalue method to obtain the weight coefficients of each influence factor, and a consistency ratio check is performed to ensure reasonable judgment logic, thereby providing a reliable weight basis for the weighted fusion of the equivalent impedance change index.

[0039] In this embodiment, it should be specifically noted that the steps for obtaining the electrical response influence coefficient are as follows:

[0040] Within the detection time window, calculate the voltage mean, current mean, voltage standard deviation, and current standard deviation within the set time window according to the actual output voltage sequence and the actual output current sequence.

[0041] Calculate the ratio of the standard deviation of voltage to the mean value of voltage to obtain the voltage variation coefficient, and calculate the ratio of the standard deviation of current to the mean value of current to obtain the current variation coefficient;

[0042] After adding the voltage variation coefficient and the current variation coefficient, calculate the mean value to obtain the electrical response influence coefficient.

[0043] By calculating the voltage variation coefficient and the current variation coefficient, the influence of dimension can be eliminated, making the degree of fluctuation comparable; then taking the average of the two can comprehensively reflect the dynamic stability of the system in two dimensions of voltage control and current load response. This method has a simple structure, clear parameter sources, and high sensitivity, and can effectively identify the volatility of electrical response without additional adjustment factors.

[0044] In this embodiment, it should be specifically noted that the steps for obtaining the control feedback influence coefficient are as follows:

[0045] Subtract the actual output voltage value in the actual output voltage sequence from the reference target voltage value in the reference target voltage sequence to obtain the voltage deviation value at each sampling point. Calculate the ratio of the voltage deviation value to the reference target voltage value to obtain the residual deviation rate at each sampling point. Calculate the mean value of the residual deviation rate at each sampling point to obtain the normalized residual deviation rate, which represents the matching degree;

[0046] Calculate the mean value of the controller output according to the controller output quantity sequence. Calculate the ratio of the mean value of the controller output to the mean value of the voltage deviation and take the absolute value to obtain the residual misguidance rate;

[0047] Perform standardization processing on the two sets of sampling data in the reference target voltage sequence and the actual output voltage sequence respectively, so that their mean values are 0 and the degree of fluctuation is the same, thereby eliminating the influence of the amplitude difference of the data itself on the matching result;

[0048] Use the enumeration method to try to shift one of the sets of data forward or backward by different numbers of time points one by one. Calculate the matching degree, that is, the cross-correlation value, between the two sets of standardized data at each shifted position. Select the number of shifted points corresponding to the maximum cross-correlation value and record it as the cross-correlation peak delay points, which is used to reflect whether there is an obvious time lag in the control response;

[0049] The enumeration method is an exhaustive search strategy used to sequentially try all possible time offsets within a preset range and gradually align the two time series. This method can comprehensively cover all feasible alignment situations and ensure capturing the optimal time correspondence relationship between the two series.

[0050] Calculate the ratio of the cross-correlation peak delay points to the total number of sampling points to obtain the residual lag rate;

[0051] The control feedback influence coefficient is calculated based on the normalized residual deviation rate, residual misguidance rate, and residual lag rate. The specific acquisition steps are as follows:

[0052] ;

[0053] In the formula, represents the control feedback influence coefficient, represents the normalized residual deviation rate, represents the residual misguidance rate, represents the residual lag rate.

[0054] The relative error between the control target and the actual output is evaluated through the normalized residual deviation rate. The guiding effect of the controller output on the error direction is quantified through the residual misguidance rate. The structural delay of the control response is revealed through the residual lag rate. This multi-dimensional fusion evaluation mechanism avoids relying on a single index, effectively improves the sensitivity and discriminability to problems such as feedback deviation, ontology maladjustment, and dynamic lag, provides a more accurate basis for dynamically correcting control parameters, and enhances the system's adaptive regulation ability to distributed power disturbances.

[0055] In this embodiment, it should be specifically noted that the acquisition steps of the behavior pattern influence coefficient are as follows:

[0056] The number of times the power change direction reverses is obtained from the actual output power sequence, denoted as the power reversal number. The power reversal number is divided by the total number of sampling points to calculate the reverse jump rate;

[0057] "The power change direction reverses" means that in three consecutive sampling points, the change trend of the output power changes from rising to falling, or from falling to rising. Specifically, if the power at a certain moment is on an upward trend relative to the previous moment and then changes to a downward trend at the next moment, or vice versa, it is regarded as a reversal of the change direction. This phenomenon usually reflects the instability of the system load behavior or the discontinuity of the control response. The more the number of reversals, the more frequent the power fluctuations, which helps to measure the dynamic complexity of the operating state.

[0058] Set the voltage threshold window , where is the nominal voltage. The number of times the output voltage value exceeds the voltage threshold window range within the detection time window is obtained, denoted as the out-of-bounds number. The out-of-bounds number is divided by the total number of sampling points to calculate the out-of-bounds rate;

[0059] The nominal voltage refers to the target output voltage value designed for the solid-state distribution transformer under rated operating conditions, which is usually preset by the system design specifications or operating standards and serves as a reference value for evaluating voltage deviation and stability. By comparing with the nominal voltage, the number of voltage overlimit times can be effectively identified, reflecting the voltage regulation ability of the system under load disturbances or control fluctuations.

[0060] According to the actual output power sequence and the actual output voltage sequence, the change value of the actual output power and the change value of the actual output voltage between two adjacent sampling points are calculated;

[0061] According to the change value of the actual output power and the change value of the actual output voltage between two adjacent sampling points, the relative change amplitude of the actual output power and the relative change amplitude of the actual output voltage at each sampling point are calculated respectively. The relative change amplitude is expressed as the ratio of the change value between two consecutive sampling points to the value at the previous time point, reflecting the change intensity under the unit reference;

[0062] The relative change amplitude of the actual output power and the relative change amplitude of the actual output voltage are added together to obtain the instantaneous total fluctuation amplitude at each sampling point, and the average value of the instantaneous total fluctuation amplitudes at all times is calculated to obtain the average behavior volatility;

[0063] The behavior pattern influence coefficient is calculated according to the reverse jump rate, the overstep rate, and the average behavior volatility. The specific obtaining steps are as follows:

[0064] ;

[0065] In the formula, is expressed as the behavior pattern influence coefficient, is expressed as the reverse jump rate, is expressed as the overstep rate, is expressed as the average behavior volatility.

[0066] The reverse jump rate can identify the frequent reversals of the system power behavior, reflecting the non-stationarity of load disturbances or control switches; the overstep rate is used to evaluate the frequency of the voltage exceeding the safe operating range, reflecting the voltage regulation ability; the average behavior volatility quantitatively reflects the comprehensive fluctuation amplitude of power and voltage, revealing the severity of the operating state. This method integrates three types of indicators: trend change, overlimit characteristics, and instantaneous disturbance, constructing a multi-dimensional, unitless, and physically meaningful system behavior evaluation mechanism, which is conducive to improving the recognition accuracy of the equivalent impedance change trend under complex operating conditions and the response timeliness of control strategy adjustment.

[0067] In this embodiment, it should be specifically noted that the steps for determining whether the equivalent impedance changes according to the equivalent impedance change index are as follows:

[0068] Compare the equivalent impedance change index with the change threshold. If the equivalent impedance change index is greater than or equal to the change threshold, it is determined that the equivalent impedance has changed; if the equivalent impedance change index is less than the change threshold, it is determined that the equivalent impedance has not changed. The change threshold is obtained through an adaptive threshold method, which is a method for dynamically adjusting the decision threshold based on the system operating state, aiming to improve the sensitivity and robustness of the decision mechanism to the change amplitude under different working conditions. In this embodiment, the change threshold is not fixedly set, but is adjusted in real time according to the distribution characteristics of the equivalent impedance change index in the historical operation data, combined with the current working conditions (such as load level, number of connected power supplies, network topology state, etc.). The specific method can use the mean and standard deviation of the change index within a sliding time window for statistical analysis, or introduce an empirical coefficient to construct a threshold correction function, so as to generate a dynamic threshold with time variability and context adaptability, making the decision logic still have strong accuracy and anti-interference ability when facing different complex operating environments.

[0069] Controller parameter dynamic adjustment module. If it is determined that the equivalent impedance has changed, the initial control parameters are dynamically corrected according to the equivalent impedance change index to obtain the actual control parameters, so as to achieve an adaptive control response to the impedance change environment;

[0070] In this embodiment, it should be specifically noted that the steps for dynamically correcting the initial control parameters according to the equivalent impedance change index to obtain the actual control parameters are as follows:

[0071] Set a detection time window, obtain the mean value of the effective voltage value and the mean value of the effective current value within the detection time window, calculate the ratio of the mean value of the effective voltage value to the mean value of the effective current value to obtain the current equivalent impedance estimation value, obtain the real-time output current value in real time, and calculate the product of the real-time output current value and the current equivalent impedance estimation value to obtain the voltage feedforward compensation amount. It should be noted that the detection time window can be 2S or 5S. The mean value of the effective voltage value refers to the arithmetic mean of the effective voltage value sequence collected from the output terminal of the solid-state distribution transformer, and the mean value of the effective current value refers to the arithmetic mean of the effective current value sequence collected from the output current channel of the solid-state distribution transformer;

[0072] Obtain the initial resistance value of the solid-state distribution transformer, calculate the ratio of the difference between the current equivalent impedance estimation value and the initial resistance value to the initial resistance value to obtain the resistance change rate;

[0073] If the resistance change rate is greater than 0, it is determined that the resistance has increased. Calculate the ratio of the change threshold to the equivalent impedance change index to obtain the correction factor. The specific obtaining steps are as follows:

[0074] ;

[0075] In the formula, is expressed as the correction factor, is denoted as the change threshold is denoted as the equivalent impedance change index. When the impedance change rate is greater than 0, it indicates that the system impedance increases, and the absorption ability of the load equivalent to the power supply output weakens, resulting in a limited transmission path for the output action of the controller. At this time, if the original control parameters are maintained, it may cause over-regulation, slow system response, or reduced stability margin. Therefore, the control parameters need to be appropriately adjusted to reduce the adjustment strength to improve the system robustness;

[0076] If the impedance change rate is less than 0, it is determined that the impedance becomes smaller, and the equivalent impedance change index is calculated by taking the ratio with the change threshold to obtain the correction factor. The specific acquisition steps are as follows:

[0077] ;

[0078] In the formula, is denoted as the correction factor is denoted as the change threshold is denoted as the equivalent impedance change index. When the impedance change rate is less than 0, it indicates that the system impedance decreases, the load response enhances, and the output of the controller is more likely to cause rapid changes in the system state. If the adjustment ability is not enhanced, it may lead to overshoot or dynamic error. Therefore, the control parameters should be adjusted to increase to improve the control accuracy and response ability to achieve a fast and accurate adjustment effect;

[0079] If the impedance change rate is equal to 0, it is determined that the impedance has no change, and the initial control parameters are not corrected;

[0080] The initial control parameters are multiplied by the correction factor to obtain the actual control parameters.

[0081] In this embodiment, the design strategy of "judging impedance change twice" is adopted to balance the sensitivity of change triggering and the accuracy of control adjustment. The first time is to construct an equivalent impedance change index, integrate multi-source features such as electrical response, control feedback, and behavior patterns, and comprehensively evaluate whether there is an impedance adaptation offset in the system, playing a role in early warning and suppressing false triggering;

[0082] The second time is to calculate the impedance change rate to accurately judge the change direction and amplitude of the impedance, and guide whether the control parameters are increased, decreased, or remain unchanged. This double-layer judgment mechanism enables the system to not only sensitively capture potential non-explicit disturbances but also avoid mis-regulation caused by instantaneous fluctuations, thereby realizing high-reliability and high-adaptability controller self-adaptive optimization.

[0083] The power quality guarantee and regulation execution module is used to adjust the output of the solid-state transformer according to the actual control parameters to achieve multi-dimensional regulation functions such as active power, reactive power, voltage, and frequency, and is also responsible for regulating tasks such as maintaining the voltage stability of the access area, suppressing power oscillation, and guiding the power flow direction;

[0084] In this embodiment, it should be specifically noted that the steps for adjusting the output of the solid-state transformer according to the actual control parameters are as follows:

[0085] According to the corrected actual control parameters, based on the target set values, such as the target output voltage, active power, and reactive power, etc., construct a control reference signal, and collect the operation state data of the current solid-state distribution transformer in real time. The operation state data includes state parameters such as output voltage, output current, active power, and reactive power, etc., for subsequent comparison and feedback during the control execution process;

[0086] Calculate the difference between the currently collected real-time operation state data and the reference signal to obtain a deviation signal. The reference signal is the target output index value set during the operation of the solid-state transformer. Input the deviation into the PI controller to obtain the PI control output;

[0087] The PI controller is a classic closed-loop feedback control algorithm, which includes two parts: proportional and integral. It is used to generate adjustment instructions according to the magnitude and cumulative trend of the current deviation, so as to achieve fast and stable tracking of the target quantity. This controller is widely used in automatic adjustment scenarios of electrical energy parameters such as voltage, current, and power, and has the characteristics of fast response speed and small steady-state error.

[0088] Synthesize the PI control output and the voltage feedforward compensation amount to obtain the final control instruction;

[0089] Adjust the output of the solid-state transformer according to the final control instruction to achieve coordinated adjustment of parameters such as active power, reactive power, output voltage, and output frequency on the output side of the transformer. By dynamically adjusting the PWM duty cycle and phase, complete the power quality guarantee on the load side, including functions such as voltage stability, frequency control, and power factor improvement;

[0090] After the regulation is executed, collect the output state parameters of the transformer again to form a closed-loop feedback. At the same time, record the control parameters, deviation amount, adjustment instruction, and execution result of this round for use by the data upload and remote monitoring module, for historical trend analysis and control effect evaluation.

[0091] The data upload and remote monitoring module is used to upload the control parameter adjustment records and real-time operation state data to the database for operation and maintenance personnel to view and perform policy intervention.

[0092] This module can upload the parameter adjustment records of the controller and the real-time operation state data of the solid-state distribution transformer to the remote database for operation and maintenance personnel to view in real time, perform historical backtracking and trend analysis, so as to achieve early warning of abnormal states, dynamic optimization of policy parameters, and support functions such as centralized operation and maintenance, distributed regulation, and remote diagnosis, greatly improving the intelligent management level and operation and maintenance efficiency of the system.

[0093] In this embodiment, it should be specifically noted that the control method of the solid-state distribution transformer for promoting the access of distributed power sources is as follows Figure 2 shown, including the following steps:

[0094] Step 1: Construct a solid-state distribution transformer with multi-port power regulation capabilities and set the initial control parameters of the solid-state distribution transformer to support subsequent dynamic control and impedance identification functions;

[0095] Step 2: Obtain the data affected by the equivalent impedance. The data affected by the equivalent impedance includes the actual output voltage sequence, the actual output current sequence, the reference target voltage sequence, the controller output quantity sequence, and the actual output power sequence. Evaluate the equivalent impedance change index based on the data affected by the equivalent impedance, and determine whether the equivalent impedance has changed according to the equivalent impedance change index;

[0096] Step 3: If it is determined that the equivalent impedance has changed, dynamically correct the initial control parameters according to the equivalent impedance change index to obtain the actual control parameters, and achieve an adaptive control response to the impedance change environment;

[0097] Step 4: Adjust the output of the solid-state transformer according to the actual control parameters to achieve multi-dimensional regulation functions such as active power, reactive power, voltage, and frequency, and at the same time be responsible for regulating tasks such as maintaining the voltage stability of the access area, suppressing power oscillations, and guiding the power flow direction;

[0098] Step 5: Upload the control parameter adjustment records and real-time operation status data to the database for operation and maintenance personnel to view and perform policy interventions.

[0099] Finally: The above is only the preferred embodiment of the present invention and is not used to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

[0100] The above is only the specific implementation manner of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art within the technical scope disclosed in the present application can easily think of changes or replacements, which should all be covered within the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claimed rights.

Claims

1. A solid-state distribution transformer control system for improving the access of distributed power sources, characterized in that, The system includes: A solid-state distribution transformer construction module for constructing a solid-state distribution transformer with multi-port power regulation capabilities and setting the initial control parameters of the solid-state distribution transformer; An equivalent impedance change evaluation module for obtaining data affected by the equivalent impedance. The data affected by the equivalent impedance includes the actual output voltage sequence, the actual output current sequence, the reference target voltage sequence, the controller output quantity sequence, and the actual output power sequence. The equivalent impedance change index is evaluated based on the data affected by the equivalent impedance, and it is determined whether the equivalent impedance has changed according to the equivalent impedance change index; A controller parameter dynamic adjustment module. If it is determined that the equivalent impedance has changed, the initial control parameters are dynamically corrected according to the equivalent impedance change index to obtain the actual control parameters; A power quality guarantee and regulation execution module for adjusting the output of the solid-state transformer according to the actual control parameters; A data upload and remote monitoring module for uploading the control parameter adjustment records and real-time operation status data to the database.

2. The solid-state distribution transformer control system for improving the access of distributed power sources according to claim 1, characterized in that: The steps of constructing a solid-state distribution transformer with multi-port power regulation capabilities are as follows: Construct a traditional two-winding power-frequency transformer. The two windings include a high-voltage side winding and a low-voltage side winding; Connect a front-end converter to the high-voltage side group of the power-frequency transformer and connect a rear-end converter to the low-voltage side group of the power-frequency transformer to construct a three-phase four-arm structure; Connect the DC sides of the front-end converter and the rear-end converter to form a common DC link, and lead out a low-voltage DC port to form a three-port structure with a high-voltage AC input terminal, a low-voltage AC output terminal, and a low-voltage DC output terminal. Thus, the construction of a solid-state distribution transformer with multi-port power regulation capabilities is completed.

3. The solid-state distribution transformer control system for promoting the access of distributed power sources according to claim 1, wherein The steps of obtaining the equivalent impedance change index are as follows: Set a detection time window, perform periodic sampling within the detection time window, set the sampling frequency, and calculate the total number of sampling points according to the time window and the sampling frequency. Obtain the actual output voltage sequence and the actual output current sequence of the transformer within the detection time window, and evaluate the electrical response influence coefficient based on the output voltage sequence and the output current sequence; Obtain the reference target voltage sequence and the controller output quantity sequence within the detection time window, and evaluate the control feedback influence coefficient based on the reference target voltage sequence, the actual output voltage sequence, and the controller output quantity sequence; Obtain the actual output power sequence within the detection time window, and evaluate the behavior pattern influence coefficient based on the actual output power sequence and the actual output voltage sequence; Normalize the electrical response influence coefficient, the control feedback influence coefficient, and the behavior pattern influence coefficient, and evaluate the equivalent impedance change index based on the normalized electrical response influence coefficient, the control feedback influence coefficient, and the behavior pattern influence coefficient. The specific obtaining steps are as follows: ； In the formula, is expressed as the equivalent impedance change index, is expressed as the electrical response influence coefficient after normalization, is expressed as the control feedback influence coefficient after normalization, is expressed as the behavior pattern influence coefficient after normalization, , , are expressed as the weight coefficient of the electrical response influence coefficient after normalization, the weight coefficient of the control feedback influence coefficient after normalization, and the weight coefficient of the behavior pattern influence coefficient after normalization.

4. The solid-state distribution transformer control system for enhancing the access of distributed power sources according to claim 3, characterized in that, The steps of obtaining the electrical response influence coefficient are as follows: Within the detection time window, calculate the voltage mean value, current mean value, voltage standard deviation, and current standard deviation within the set time window according to the actual output voltage sequence and the actual output current sequence; Calculate the ratio of the voltage standard deviation to the voltage mean value to obtain the voltage variation coefficient, and calculate the ratio of the current standard deviation to the current mean value to obtain the current variation coefficient; Add the voltage variation coefficient and the current variation coefficient, and then calculate the mean value to obtain the electrical response influence coefficient.

5. The solid-state distribution transformer control system for enhancing the access of distributed power sources according to claim 3, characterized in that: The steps for obtaining the control feedback influence coefficient are as follows: Subtract the actual output voltage value in the actual output voltage sequence from the reference target voltage value in the reference target voltage sequence to obtain the voltage deviation value at each sampling point. Calculate the ratio of the voltage deviation value to the reference target voltage value to obtain the residual deviation rate at each sampling point. Calculate the mean value of the residual deviation rate at each sampling point to obtain the normalized residual deviation rate. Calculate the mean value of the controller output according to the controller output quantity sequence. Calculate the ratio of the mean value of the controller output to the mean value of the voltage deviation and take the absolute value to obtain the residual misguidance rate. Perform standardization processing on the two sets of sampling data in the reference target voltage sequence and the actual output voltage sequence respectively. Use the enumeration method to shift one of the sets of data forward or backward by different numbers of time points one by one. Calculate the matching degree, that is, the cross-correlation value, between the two sets of standardized data at each shifted position. Select the number of shifted points corresponding to the maximum cross-correlation value and record it as the cross-correlation peak delay points. Calculate the ratio of the cross-correlation peak delay points to the total number of sampling points to obtain the residual lag rate. Calculate the control feedback influence coefficient according to the normalized residual deviation rate, the residual misguidance rate, and the residual lag rate.

6. The solid-state distribution transformer control system for enhancing the access of distributed power sources according to claim 3, wherein: The steps for obtaining the behavior pattern influence coefficient are as follows: Obtain the number of times the power change direction is reversed according to the actual output power sequence, and record it as the power reversal times. Calculate the ratio of the power reversal times to the total number of sampling points to obtain the reverse jump rate. Set a voltage threshold window, and obtain the number of times the output voltage value exceeds the voltage threshold window range within the detection time window, and record it as the out-of-bounds times. Calculate the ratio of the out-of-bounds times to the total number of sampling points to obtain the out-of-bounds rate. According to the actual output power sequence and the actual output voltage sequence, calculate the actual output power change value and the actual output voltage change value between two adjacent sampling points. According to the actual output power change value and the actual output voltage change value between two adjacent sampling points, calculate the relative change amplitude of the actual output power and the relative change amplitude of the actual output voltage at each sampling point respectively. Add the relative change amplitude of the actual output power and the relative change amplitude of the actual output voltage to obtain the instantaneous total fluctuation amplitude at each sampling point, and calculate the average value of the instantaneous total fluctuation amplitude at all times to obtain the average behavior volatility. Calculate the behavior pattern influence coefficient according to the reverse jump rate, the out-of-bounds rate, and the average behavior volatility.

7. The solid-state distribution transformer control system for enhancing the access of distributed power sources according to claim 1, wherein: The steps for determining whether the equivalent impedance has changed according to the equivalent impedance change index are as follows: Compare the equivalent impedance change index with the change threshold. If the equivalent impedance change index is greater than or equal to the change threshold, it is determined that the equivalent impedance has changed; if the equivalent impedance change index is less than the change threshold, it is determined that the equivalent impedance has not changed.

8. The solid-state distribution transformer control system for enhancing the access of distributed power sources according to claim 1, wherein: The steps for dynamically correcting the initial control parameters according to the equivalent impedance change index to obtain the actual control parameters are as follows: Obtain the average value of the effective voltage and the average value of the effective current within the detection time window, calculate the ratio of the average value of the effective voltage to the average value of the effective current to obtain the current estimated value of the equivalent impedance, obtain the output current value in real time, and calculate the product of the real-time output current value and the current estimated value of the equivalent impedance to obtain the voltage feedforward compensation amount; Obtain the initial resistance value of the solid-state distribution transformer, calculate the ratio of the current estimated value of the equivalent impedance minus the initial resistance value to the initial resistance value to obtain the resistance change rate; If the resistance change rate is greater than 0, it is determined that the resistance increases, and calculate the ratio of the change threshold to the equivalent impedance change index; If the resistance change rate is less than 0, it is determined that the resistance decreases, and calculate the ratio of the equivalent impedance change index to the change threshold; If the resistance change rate is equal to 0, it is determined that the resistance has no change, and the initial control parameters are not corrected; Calculate the product of the initial control parameters and the correction factor to obtain the actual control parameters.

9. The solid-state distribution transformer control system for enhancing the access of distributed power sources according to claim 8, characterized in that: The step of adjusting the output of the solid-state transformer according to the actual control parameters is as follows: Based on the actual control parameters and the target set value, construct a control reference signal, and collect the operation status data of the current solid-state distribution transformer in real time; Calculate the difference between the currently collected real-time operation status data and the reference signal to obtain a deviation signal, and input the deviation into the PI controller to obtain the PI control output; Synthesize the PI control output and the voltage feedforward compensation amount to obtain the final control instruction; Adjust the output of the solid-state transformer according to the final control instruction.

10. A control method for a solid-state distribution transformer for improving the access of distributed power sources, which is used to implement the solid-state distribution transformer control system for improving the access of distributed power sources according to any one of claims 1-9, characterized in that: It includes the following steps: Step 1: Construct a solid-state distribution transformer with multi-port power regulation ability, and set the initial control parameters of the solid-state distribution transformer; Step 2: Obtain the data affected by the equivalent impedance. The data affected by the equivalent impedance includes the actual output voltage sequence, the actual output current sequence, the reference target voltage sequence, the controller output quantity sequence, and the actual output power sequence. Evaluate the equivalent impedance change index based on the data affected by the equivalent impedance, and determine whether the equivalent impedance has changed according to the equivalent impedance change index; Step 3: If it is determined that the equivalent impedance has changed, dynamically correct the initial control parameters according to the equivalent impedance change index to obtain the actual control parameters; Step 4: Adjust the output of the solid-state transformer according to the actual control parameters; Step 5: Upload the control parameter adjustment record and the real-time operation status data to the database.

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