An adaptive series impedance compensation method considering bidirectional power flow characteristics

Abstract

The application discloses a kind of self-adapting series impedance compensation methods considering bidirectional power flow characteristics, belong to distribution network voltage control technical field, including: real-time acquisition line voltage signal and current signal of point of common coupling, the active power and reactive power of line are calculated;According to active power and reactive power, the virtual impedance compensation amount needed to be inserted in is calculated;According to the flow direction of active power, the direction of power flow is determined, and the positive and negative polarity of virtual impedance compensation amount is determined according to the direction of power flow;Dip voltage is determined based on virtual impedance compensation amount, and voltage compensation is carried out.The application not only solves the steady-state voltage bidirectional out-of-limit problem caused by distributed power power reverse sending, but also ensures the accurate stability of distribution network terminal voltage.

Description

Technical Field

[0001] This invention belongs to the field of distribution network voltage control technology, specifically relating to an adaptive series impedance compensation method that considers bidirectional power flow characteristics. Background Technology

[0002] As the penetration rate of distributed photovoltaic and wind power and other new energy sources in distribution networks continues to rise, the distribution network is gradually evolving from a traditional unidirectional radial network into an active distribution network with multi-source characteristics. This structural change brings significant bidirectional power flow characteristics: when the output of distributed power sources exceeds the local load, power backflow causes the voltage at the feeder end to rise; while during periods of insufficient sunlight or peak load, forward power flow causes voltage drop. In particular, in medium and low voltage distribution networks, the line impedance exhibits a high resistance ratio, making the voltage extremely sensitive to fluctuations in active power, and relying solely on reactive power regulation is often inefficient.

[0003] Traditional voltage management methods have significant limitations in addressing these challenges. OLTC (on-load tapchanger) is limited by the number of mechanical switching operations and response speed, making it difficult to handle frequent voltage fluctuations on the order of minutes or even seconds caused by the randomness of renewable energy output. While parallel-type reactive power compensation devices such as SVG (Static Var Generator) and D-STATCOM (Distributed Static Synchronous Compensator) have faster response speeds, in high-impedance-ratio lines, due to the dominant role of line resistance, regulating voltage solely through reactive power injection is inefficient and often fails to effectively suppress voltage exceedance issues caused by active power backfeeding. Furthermore, existing series-type voltage compensation devices, such as DVRs (Dynamic Voltage Restorers), while capable of directly injecting voltage vectors, are generally designed for voltage sags or protection of specific sensitive loads under unidirectional power flow. They lack the ability to adapt to bidirectional power flow conditions in distribution networks and cannot dynamically adjust impedance characteristics according to changes in power flow direction. Consequently, they are unable to achieve the expected mitigation effect when dealing with the steady-state voltage bidirectional over-limit problem caused by the integration of high-penetration renewable energy sources. Summary of the Invention

[0004] To address the aforementioned problems in the prior art, this invention provides an adaptive series impedance compensation method considering bidirectional power flow characteristics. The technical problem to be solved by this invention is achieved through the following technical solution:

[0005] This invention provides an adaptive series impedance compensation method considering bidirectional power flow characteristics, comprising:

[0006] Real-time acquisition of voltage and current signals at the common connection point in the line, and calculation of the active and reactive power of the line;

[0007] Calculate the amount of virtual impedance compensation that needs to be inserted based on the active power and the reactive power.

[0008] The power flow direction is determined based on the direction of active power flow, and the positive and negative polarities of the virtual impedance compensation amount are determined based on the power flow direction.

[0009] The longitudinal component of the voltage drop is determined based on the virtual impedance compensation amount, and voltage compensation is performed.

[0010] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0011] (1) This invention provides an adaptive series impedance compensation method that considers bidirectional power flow characteristics. By real-time acquisition of voltage and current signals at the common connection point in the line, the active power and reactive power of the line are calculated. Then, the power flow direction is identified based on the active power, and the positive and negative polarities of the virtual impedance compensation amount are configured accordingly: under positive power flow conditions, it exhibits negative impedance characteristics to compensate for voltage drop, and under reverse power flow conditions, it exhibits positive impedance characteristics to suppress voltage rise, thereby solving the problem of bidirectional over-limit of steady-state voltage caused by the reverse power flow of distributed power sources.

[0012] (2) This invention overcomes the shortcomings of the existing linear anti-droop control in terms of adaptability in the full operating range by constructing a nonlinear correction term that includes a quadratic correction term and a triangular correction term. The quadratic correction term can accurately fit the nonlinear voltage drop characteristics of the light load area, and the triangular correction term can effectively smooth the voltage ripple caused by power fluctuations, so that the compensation voltage curve is highly consistent with the ideal curve, ensuring the accurate and stable voltage at the end of the distribution network, and achieving the purpose of improving power quality and system robustness.

[0013] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0014] Figure 1 This is a schematic flowchart of an adaptive series impedance compensation method considering bidirectional power flow characteristics provided in an embodiment of the present invention.

[0015] Figure 2 This is a graph showing the variation of the voltage at the end of the distribution network with the cross-sectional area of ​​the line under different line cross-sectional areas, provided by an embodiment of the present invention.

[0016] Figure 3 This is a graph showing the variation of impedance factor with line cross-sectional area under different power factors, provided by an embodiment of the present invention.

[0017] Figure 4This is a schematic diagram of the power grid impedance model provided in an embodiment of the present invention;

[0018] Figure 5 It is a curve of voltage-load change before and after compensation using a virtual impedance control method based on the anti-droop coefficient;

[0019] Figure 6 This is a waveform diagram of the line end voltage before adding virtual impedance compensation under the forward power flow condition provided in the embodiments of the present invention;

[0020] Figure 7 This is a line-end voltage waveform diagram after adding virtual impedance compensation under forward power flow conditions provided in an embodiment of the present invention.

[0021] Figure 8 This is a waveform diagram of the line end voltage before adding virtual impedance compensation under reverse power flow conditions provided in this embodiment of the invention.

[0022] Figure 9 This is a waveform diagram of the line end voltage after adding virtual impedance compensation under reverse power flow conditions provided in an embodiment of the present invention.

[0023] Figure 10 It shows the curves of voltage drop before voltage compensation and the compensation voltage calculated using different methods as a function of load. Detailed Implementation

[0024] The present invention will be further described in detail below with reference to specific embodiments, but the implementation of the present invention is not limited thereto.

[0025] Figure 1 This is a schematic flowchart of an adaptive series impedance compensation method considering bidirectional power flow characteristics provided in an embodiment of the present invention. Figure 1 As shown, this embodiment of the invention provides an adaptive series impedance compensation method considering bidirectional power flow characteristics, comprising:

[0026] S1. Real-time acquisition of voltage and current signals at the common connection point in the line, and calculation of the active and reactive power of the line.

[0027] In this embodiment, the point of common coupling (PCC) refers to the electrical connection interface between the distributed generation equipment and the distribution network. The voltage and current signals of the PCC are synchronously collected at a preset sampling frequency, and the active and reactive power transmitted by the line are calculated based on the instantaneous power theory.

[0028] S2. Calculate the amount of virtual impedance compensation that needs to be inserted based on the active power and reactive power.

[0029] Specifically, the formula for calculating the voltage at the end of the line is as follows:

[0030] ;

[0031] In the formula, Represents the power factor angle. Indicates the apparent power of the line. Indicates the length of the line. Represents the resistance per unit length of the circuit. Represents the reactance per unit length of the line. Indicates the rated terminal voltage. This represents the voltage at the end of the line. Clearly, factors such as line cross-sectional area, apparent power, power factor, and line length all affect the voltage drop across the line.

[0032] Next, we will first analyze the impact of line apparent power on the voltage at the end of the distribution network. Figure 2 This is a graph showing the variation of the voltage at the end of the distribution network with the line cross-sectional area under different line cross-sectional areas, as provided in an embodiment of the present invention. Figure 2 As shown, the horizontal axis represents the cross-sectional area of ​​the line, and the vertical axis represents the voltage at the end of the line and the power factor of the connected load. Rated terminal voltage Line apparent power Selecting 10kVA, 20kVA, 30kVA, and 40kVA respectively, since the complex form of apparent power is... ,in, The imaginary unit, , These represent active power and reactive power, respectively. Changes in either will cause a voltage drop through the line impedance, thus affecting different power flows. , Combinations can affect the voltage at the end of the distribution network.

[0033] Next, the impact of the power factor of the connected load on the voltage at the end of the distribution network is analyzed. The impedance factor is defined. , Indicates the line resistance. This indicates the line inductance. Figure 3 This is a graph showing the variation of impedance factor with line cross-sectional area under different power factors, provided by an embodiment of the present invention. The horizontal axis represents the line cross-sectional area, and the vertical axis represents the impedance factor and power factor. Choosing values ​​of 0.92, 0.96, and 0.98 respectively, it is clear that when the power factor angle... When the impedance factor changes This will change accordingly, thus affecting the voltage loss characteristics of the line.

[0034] Based on the above analysis, it can be seen that line impedance (negatively correlated with line cross-sectional area) and load power (depending on apparent power and power factor) jointly affect line voltage drop.

[0035] In existing technologies, a virtual impedance control method based on the anti-droop coefficient is used for voltage compensation. The virtual resistance compensation amount and virtual reactance compensation amount that need to be inserted in series are expressed as follows:

[0036] ;

[0037] ;

[0038] in, The anti-droop coefficient represents the amount of virtual resistance compensation. The anti-droop coefficient represents the amount of virtual reactance compensation. , These represent active power and reactive power, respectively. , These represent the virtual resistance compensation and virtual reactance compensation calculated using existing virtual impedance control methods based on the anti-droop coefficient, respectively. Therefore, by collecting the active and reactive power of the lines and applying anti-droop control, the required virtual impedance compensation for different lines can be obtained, thereby improving the terminal voltage of the distribution network.

[0039] Optionally, the anti-droop coefficients of the virtual resistance compensation and virtual reactance compensation can be calculated using the following formulas:

[0040] ;

[0041] ;

[0042] In the formula, , These represent the active power and reactive power when the voltage at the end of the line drops by 10% relative to the rated voltage.

[0043] It can be seen that the core assumption of existing virtual impedance control methods based on the anti-droop coefficient is that the line voltage drop has a simple linear relationship with the change in active power / reactive power. However, in actual distribution networks, load characteristics such as nonlinear loads, skin effect, and contact resistance can cause the impedance to exhibit nonlinear characteristics, causing the relationship between voltage drop and active power / reactive power to deviate from the linear assumption.

[0044] To overcome the limitations of existing technologies, this embodiment reveals the essential laws governing voltage drop through a nonlinear model of grid impedance. Figure 4 This is a schematic diagram of the power grid impedance model provided in an embodiment of the present invention. Please refer to [link / reference]. Figure 4 The total impedance of the line is:

[0045] ;

[0046] In the formula, This represents the effective value of the load impedance. Indicates the total impedance. Indicates the line resistance. Indicates line inductance. The imaginary unit, It represents the power factor angle.

[0047] Line current Represented as:

[0048] .

[0049] active power of the line and reactive power They are represented as follows:

[0050] ;

[0051] ;

[0052] From this, the voltage drop can be obtained. The formula is:

[0053] ;

[0054] It should be noted that the voltage drop Refers to the longitudinal component of the difference between the rated voltage of the line and the voltage at the end of the line. This indicates the voltage at the end of the line.

[0055] Furthermore, the above equation can be expressed as follows using voltage division:

[0056] .

[0057] Impedance comprises resistive and reactive components. The resistive component impedes the flow of current and consumes energy, which is converted into heat. The reactive component, generated by inductance or capacitance, temporarily stores and releases energy but does not consume energy. It can be seen that the total impedance and current of a circuit depend not only on the resistance of the circuit itself. and reactance It is also affected by the load impedance. Z and power factor angle The dynamic impact; at the same time, the voltage drop at the end of the line. It is determined by all the variables mentioned above. , , , , There is no independent and direct linear correspondence between them; instead, they exhibit a highly coupled nonlinear state.

[0058] After a load is connected, the equivalent impedance increases nonlinearly due to the contact resistance of the line joints and the skin effect of the transformer windings, resulting in insufficient compensation in the existing linear compensation method. Figure 5 This is a graph showing the voltage-load changes before and after compensation using a virtual impedance control method based on the anti-droop coefficient. For example... Figure 5 As shown, curve a represents the change in line-end voltage with load, and curve b represents the line-end voltage after compensation using the existing virtual impedance control method based on the anti-droop coefficient. It can be seen that the existing compensation method exhibits undercompensation across the entire operating range, resulting in a lower line-end voltage, especially severe in lightly loaded areas. The root cause of this mismatch across the entire operating range lies in the fact that a simple linear model cannot capture and adapt to the complex nonlinear dynamic characteristics of distribution network lines, thus failing to provide accurate and stable voltage support throughout the entire operating range.

[0059] To solve the above problems, this embodiment calculates the required virtual impedance compensation amount according to the following steps:

[0060] S201. Calculate the basic virtual resistance compensation amount based on the active power and the anti-droop coefficient of the virtual resistance compensation amount:

[0061] ;

[0062] In the formula, The anti-droop coefficient represents the amount of virtual resistance compensation. Indicates active power. This represents the basic virtual resistance compensation amount. , , , These represent the active power and reactive power when the voltage at the end of the line drops by 10% relative to the rated voltage.

[0063] Calculate the basic virtual reactance compensation amount based on the reactive power and the anti-droop coefficient of the virtual reactance compensation amount:

[0064] ;

[0065] In the formula, The anti-droop coefficient represents the amount of virtual reactance compensation. Indicates reactive power. This represents the basic virtual reactance compensation amount.

[0066] S202. Perform nonlinear corrections on the basic virtual resistance compensation and the basic virtual reactance compensation respectively to obtain the virtual resistance compensation and virtual reactance compensation that need to be inserted.

[0067] On the one hand, the first nonlinear correction term Multiply by the basic virtual resistance compensation amount to obtain the virtual resistance compensation amount that needs to be inserted in series. The first nonlinear correction term Based on the fundamental compensation gain constant The second-order correction term based on the active power load rate and the triangular correction term based on active power Composition, represented as:

[0068]

[0069] in,

[0070] ;

[0071] ;

[0072] ;

[0073] ;

[0074] ;

[0075] In the formula, This is a preset constant used to control the voltage compensation amplitude. Represents the power factor angle. Indicates the power factor of the connected load. This represents the active power when the voltage at the end of the line drops by 10% relative to the rated voltage. Used to compensate for the inherent voltage drop of distribution network lines, ensuring that the distribution network lines always have positive voltage support capability under all operating conditions.

[0076] On the other hand, the second nonlinear correction term Multiply by the basic virtual reactance compensation amount to obtain the virtual reactance compensation amount that needs to be inserted in series. The second nonlinear correction term Based on the fundamental compensation gain constant The second-order correction term based on the reactive power load rate and the triangular correction term based on reactive power Composition, represented as:

[0077]

[0078] in,

[0079] ;

[0080] ;

[0081] ;

[0082] ;

[0083] ;

[0084] In the formula, This is a preset constant used to control the voltage compensation amplitude. This represents the reactive power when the voltage at the end of the line drops by 10% relative to the rated voltage.

[0085] In steps S201~S202, and As a quadratic function, it facilitates fitting the nonlinear loss characteristics of power lines, and has the following main functions: Firstly, / along with / The squared change can accurately offset this high-order nonlinear voltage drop, solving the problem of severe undercompensation under light loads, while the compensation strength can be weakened as the load increases; secondly, and The curvature of the function is controlled to ensure that the compensation voltage has a smooth and continuous derivative, avoiding abrupt changes in the compensation method and guaranteeing the smoothness of the control process. Thirdly, considering that the power factor of the line affects the voltage drop, and that distributed power sources, due to output fluctuations and differences in reactive power regulation capabilities, are prone to continuous changes in the overall power factor at the end of the line, the secondary correction term of the active power load rate can be dynamically adjusted based on the current power factor. and the second-order correction term for reactive power load rate coefficient of the quadratic term The value of .

[0086] Triangular correction term based on active power and the triangular correction term based on reactive power Each component consists of a linear component and a sinusoidal component, designed to suppress fluctuations caused by distributed generation. The linear component provides a linearly decreasing adjustment trend with increasing load, ensuring that the compensation strength gradually weakens as the load increases. Since distributed generation such as photovoltaics is often accompanied by periodic power fluctuations or specific harmonics, this causes the line impedance to exhibit periodic slight changes. Therefore, a sinusoidal component is introduced, and by superimposing an anti-phase component with the same frequency as the interference, the voltage ripple caused by power factor changes can be effectively smoothed, thus completing a periodic fine correction. This design method can better fit the non-ideal voltage fluctuations caused by distributed loads, harmonics, or imperfect linearity in actual power lines, thereby further improving the consistency between the actual compensation voltage and the ideal compensation voltage in the intermediate load range on the basis of overall nonlinear compensation.

[0087] S3. Determine the power flow direction based on the direction of active power flow, and determine the positive and negative polarities of the virtual impedance compensation amount based on the power flow direction.

[0088] In this embodiment, when the active power When the current condition is determined to be a positive power flow condition, meaning the grid is supplying power to the load, the voltage drop will occur. Since the voltage at the end is lower than the voltage at the beginning, the virtual impedance compensation is configured with a negative polarity to generate a reverse voltage rise to offset the inherent voltage drop of the line; when the active power When the current condition is determined to be reverse power flow, the voltage drop occurs. Since the voltage at the end is higher than the voltage at the beginning, the virtual impedance compensation needs to be configured with positive polarity to increase line damping and suppress voltage rise.

[0089] It should be noted that "the direction of active power flow" actually refers to the net effective direction of active power transmission. The determination is based on the positive or negative sign of the active power. When the active power calculated according to the reference direction is positive, it means that the energy flows in the positive direction of the reference direction; conversely, when it is negative, it means that the energy flows in the opposite direction of the reference direction.

[0090] S4. Determine the voltage drop based on the virtual impedance compensation amount and perform voltage compensation.

[0091] Specifically, step S4 includes:

[0092] S401, The amount of virtual resistance compensation required to be inserted in series. and virtual reactance compensation Calculate the voltage drop:

[0093] ;

[0094] In the formula, Indicates active power. Indicates reactive power. Indicates the voltage at the end of the line. Indicates the line resistance. Indicates the line reactance. This indicates the voltage drop.

[0095] S402, Based on the drop voltage Perform voltage compensation.

[0096] In this embodiment, to avoid applying an excessively large first nonlinear correction term under light load conditions... Second nonlinear correction term This leads to overcompensation, and the directly calculated virtual impedance compensation is subject to measurement noise, load changes, and system transients, exhibiting frequent fluctuations. Optionally, based on the drop voltage... Before performing voltage compensation, the following steps are also included:

[0097] judge Is it greater than the preset range, such as the rated terminal voltage? 1%; if so, then based on the drop voltage. Determine the synchronization signal :

[0098] ;

[0099] In the formula, , This indicates the preset number of fine-tuning attempts.

[0100] If synchronization signal Then, the virtual impedance compensation amount is increased by the first preset step size; if the synchronization signal Then the virtual impedance compensation amount is reduced according to the second preset step size.

[0101] Calculate the sag voltage based on the fine-tuned virtual impedance compensation. and return the judgment. The process continues until the preset number of fine-tuning steps is reached, checking if the number of steps exceeds the preset range. ,or Less than or equal to the preset range.

[0102] The adaptive series impedance compensation method considering bidirectional power flow characteristics provided by this invention will be further illustrated below through simulation experiments.

[0103] Specifically, a simulation model is built using the SIMULINK simulation tool in the MATLAB environment, and the rated terminal voltage is set. The power factor of the connected load A 30kW load is connected at 0s, switches to a 40kW load after 0.6s, and switches to a 50kW load after 1.2s. The line impedance is set to... .

[0104] First, we simulate a positive power flow condition. Figure 6 This is a waveform diagram of the line end voltage before adding virtual impedance compensation under forward power flow conditions, provided in an embodiment of the present invention. Figure 7 This is a waveform diagram of the line-end voltage under forward power flow conditions with added virtual impedance compensation, provided in an embodiment of the present invention. The horizontal axis represents simulation time, and the vertical axis represents the line-end voltage. Figure 6 As can be seen, in the initial stage of the simulation (0~0.6s), the voltage at the end of the circuit is 297.5V. As the simulation time increases, the voltage at the end of the circuit drops to 293V (0.6s~1.2s), and then drops to 288V in the later stage of the simulation (after 1.2s). Figure 7 As shown, the line-end voltage is compensated to 310V in the first 0-0.6s, to 310.7V in the first 0.6-1.2s, and to 311V after 1.2s. Clearly, under forward power flow conditions, the adaptive series impedance compensation method provided by this invention can effectively improve the line-end voltage of the distribution network.

[0105] Next, we simulated the reverse power flow condition. Figure 8 This is a waveform diagram of the line end voltage before adding virtual impedance compensation under reverse power flow conditions, provided in an embodiment of the present invention. Figure 9 This is a waveform diagram of the line-end voltage under reverse power flow conditions with added virtual impedance compensation, provided in an embodiment of the present invention. The horizontal axis represents simulation time, and the vertical axis represents the line-end voltage. It should be noted that under reverse power flow conditions, the power flow direction is opposite to the voltage drop direction, resulting in the line-end voltage being higher than the rated voltage at the beginning, causing a voltage rise phenomenon. Figure 8 As can be seen, in the initial stage of the simulation (0~0.6s), the voltage at the end of the circuit rises to 323.5V. Between 0.6s and 1.2s, the voltage further increases to 328V, and in the later stage of the simulation (after 1.2s), it reaches 333V. Clearly, Figure 8 This clearly demonstrates the problem of voltage exceeding limits due to reverse power flow causing a continuous rise. For example... Figure 9 As shown, after adding virtual impedance compensation, the voltage at the end of the circuit is stably controlled around 311V throughout the entire simulation cycle, with a smooth waveform, effectively suppressing the voltage rise caused by power backfeed. In other words, under reverse power flow conditions, the adaptive series impedance compensation method provided by this invention can effectively suppress the voltage rise at the end of the line, and stably adjust the voltage at the end of the line that exceeds the limit due to power backfeed to a safe operating range, significantly improving the voltage quality at the end of the distribution network.

[0106] Furthermore, Figure 10 These are graphs showing the voltage drop before voltage compensation and the compensation voltage calculated using different methods as a function of load. For example... Figure 10 As shown, under forward power flow conditions, the adaptive series impedance compensation method provided by this invention and the existing virtual impedance control method based on the anti-droop coefficient are used to compensate the terminal voltage, respectively. Curve a represents the voltage drop before virtual impedance compensation as a function of load; curve c represents the terminal voltage compensated using the adaptive series impedance compensation method provided by this invention as a function of load; and curve b represents the terminal voltage compensated using the existing virtual impedance control method based on the anti-droop coefficient as a function of load. It can be seen that the existing virtual impedance control method based on the anti-droop coefficient (curve b) exhibits significant voltage deviation across the entire load range and displays a single linear characteristic, failing to adapt to the nonlinear voltage drop of actual lines. In contrast, the compensation voltage calculated using the adaptive series impedance compensation method provided by this invention (curve c) achieves a high degree of fit with the voltage drop corresponding to curve a, i.e., the ideal compensation voltage, with a smooth and closely following trajectory.

[0107] Table 1 shows a comparative analysis of the tracking accuracy and error of the compensation voltage under different load conditions:

[0108] Table 1

[0109]

[0110] As shown in Table 1, the present invention improves the voltage tracking accuracy by 85.7%, 95.0%, and 100.0% under light load (30kW), medium load (40kW), and heavy load (50kW) conditions, respectively, achieving zero-error tracking of the ideal value, especially in the high load region. This significant improvement is attributed to the first nonlinear correction term in the present invention. Second nonlinear correction term The inherent nonlinear adaptive structure: through a constant term The second-order correction term with active power load rate Triangular correction term based on active power and constant terms With the quadratic correction term based on reactive power load rate Triangular correction term based on reactive power The synergistic effect of these technologies enables dynamic sensing and precise compensation of complex voltage drop characteristics under different operating conditions.

[0111] As can be seen from the above embodiments, the beneficial effects of the present invention are as follows:

[0112] (1) This invention provides an adaptive series impedance compensation method that considers bidirectional power flow characteristics. By real-time acquisition of voltage and current signals at the common connection point in the line, the active power and reactive power of the line are calculated. Then, the power flow direction is identified based on the active power, and the positive and negative polarities of the virtual impedance compensation amount are configured accordingly: under positive power flow conditions, it exhibits negative impedance characteristics to compensate for voltage drop, and under reverse power flow conditions, it exhibits positive impedance characteristics to suppress voltage rise, thereby solving the problem of bidirectional over-limit of steady-state voltage caused by the reverse power flow of distributed power sources.

[0113] (2) This invention overcomes the shortcomings of the existing linear anti-droop control in terms of adaptability in the full operating range by constructing a nonlinear correction term that includes a quadratic correction term and a triangular correction term. The quadratic correction term can accurately fit the nonlinear voltage drop characteristics of the light load area, and the triangular correction term can effectively smooth the voltage ripple caused by power fluctuations, so that the compensation voltage curve is highly consistent with the ideal curve, ensuring the accurate and stable voltage at the end of the distribution network, and achieving the purpose of improving power quality and system robustness.

[0114] In the description of this invention, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0115] The use of terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples" indicates that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. In addition, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0116] Although this application has been described herein in conjunction with various embodiments, those skilled in the art, by reviewing the accompanying drawings, disclosure, and appended claims, can understand and implement other variations of the disclosed embodiments in carrying out the claimed application. The above description is a further detailed explanation of the invention in conjunction with specific preferred embodiments, and it should not be construed that the specific implementation of the invention is limited to these descriptions. For those skilled in the art, several simple deductions or substitutions can be made without departing from the concept of the invention, and all such deductions or substitutions should be considered within the scope of protection of the invention.

Claims

1. An adaptive series impedance compensation method considering bidirectional power flow characteristics, characterized in that, include: Real-time acquisition of voltage and current signals at the common connection point in the line, and calculation of the active and reactive power of the line; Calculate the amount of virtual impedance compensation that needs to be inserted based on the active power and the reactive power. The power flow direction is determined based on the direction of active power flow, and the positive and negative polarities of the virtual impedance compensation amount are determined based on the power flow direction. The voltage drop is determined based on the virtual impedance compensation amount, and voltage compensation is performed. The virtual impedance compensation includes virtual resistance compensation and virtual reactance compensation. The step of calculating the virtual impedance compensation amount to be inserted based on the active power and the reactive power includes: calculating the basic virtual resistance compensation amount based on the active power and the anti-droop coefficient of the virtual resistance compensation amount; calculating the basic virtual reactance compensation amount based on the reactive power and the anti-droop coefficient of the virtual reactance compensation amount; and performing nonlinear correction on the basic virtual resistance compensation amount and the basic virtual reactance compensation amount respectively to obtain the virtual resistance compensation amount and the virtual reactance compensation amount to be inserted. The steps of performing nonlinear corrections on the basic virtual resistance compensation and the basic virtual reactance compensation to obtain the virtual resistance compensation and virtual reactance compensation to be inserted in series include: multiplying the first nonlinear correction term by the basic virtual resistance compensation to obtain the virtual resistance compensation to be inserted in series. The first nonlinear correction term is determined by the basic compensation gain constant. The second-order correction term based on the active power load rate and the triangular correction term based on active power Composition: Multiply the second nonlinear correction term by the basic virtual reactance compensation amount to obtain the virtual reactance compensation amount that needs to be inserted. The second nonlinear correction term is determined by the basic compensation gain constant. The second-order correction term based on the reactive power load rate and the triangular correction term based on reactive power constitute; The first nonlinear correction term is expressed as: ； in, ； ； ； ； ； In the formula, This is a preset constant used to control the voltage compensation amplitude. Represents the power factor angle. Indicates the power factor of the connected load. This represents the active power when the voltage at the end of the line drops by 10% relative to the rated voltage. The second nonlinear correction term is expressed as: ； in, ； ； ； ； ； In the formula, This is a preset constant used to control the voltage compensation amplitude. This represents the reactive power when the voltage at the end of the line drops by 10% relative to the rated voltage.

2. The adaptive series impedance compensation method considering bidirectional power flow characteristics according to claim 1, characterized in that, The basic virtual resistance compensation amount is calculated using the following formula: ； In the formula, The anti-droop coefficient represents the virtual resistance compensation amount. Indicates active power. This represents the basic virtual resistance compensation amount.

3. The adaptive series impedance compensation method considering bidirectional power flow characteristics according to claim 2, characterized in that, The basic virtual reactance compensation amount is calculated according to the following formula: ； In the formula, This represents the anti-droop coefficient of the virtual reactance compensation amount. Indicates reactive power. This represents the basic virtual reactance compensation amount.

4. The adaptive series impedance compensation method considering bidirectional power flow characteristics according to claim 1, characterized in that, The steps of determining the power flow direction based on the direction of active power flow and determining the positive and negative polarities of the virtual impedance compensation amount based on the power flow direction include: When active power When the current power flow condition is determined to be positive, the virtual impedance compensation amount is configured to have negative polarity characteristics. When active power When the current condition is determined to be reverse power flow, the virtual impedance compensation amount is configured to have positive polarity characteristics. The positive polarity of the virtual impedance compensation is used to increase the equivalent impedance of the line to suppress voltage rise during reverse power flow conditions, while the negative polarity of the virtual impedance compensation is used to offset the line impedance to compensate for voltage drop during forward power flow conditions.

5. The adaptive series impedance compensation method considering bidirectional power flow characteristics according to claim 1, characterized in that, The steps of determining the voltage drop based on the virtual impedance compensation amount and performing voltage compensation include: The amount of virtual resistance compensation required to be inserted in series and virtual reactance compensation Calculate the voltage drop: ； In the formula, Indicates active power. Indicates reactive power. Indicates the voltage at the end of the line. Indicates the line resistance. Indicates the line reactance. Indicates voltage drop; According to the voltage drop Perform voltage compensation.

6. The adaptive series impedance compensation method considering bidirectional power flow characteristics according to claim 5, characterized in that, According to the voltage drop Before performing voltage compensation, the following steps are also included: judge Is it greater than the preset range? If so, then according to the aforementioned drop voltage Determine the synchronization signal : ； In the formula, , Indicates the preset number of fine-tuning steps; If synchronization signal Then, the virtual impedance compensation amount is increased by the first preset step size; if the synchronization signal Then the virtual impedance compensation amount is reduced according to the second preset step size; Calculate the sag voltage based on the fine-tuned virtual impedance compensation. and return the judgment. The process continues until the preset number of fine-tuning steps is reached, checking if the number of steps exceeds the preset range. ,or Less than or equal to the preset range.

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