Flexible regulation and control method and system for terminal voltage of transformer area power grid

Abstract

The invention provides a platform area power grid tail end voltage flexible regulation and control method and system. The method comprises the steps that a sampling module measures common coupling point voltage at the tail end of a platform area power grid; the impedance calculation unit obtains load end impedance; the current calculation unit calculates the current of the common coupling point through the voltage of the common coupling point and the impedance of the load end; the current resolving unit is used for resolving the common coupling point current into negative-sequence current and zero-sequence current; the compensation current unit calculates a compensation current component required for maintaining the stability of the voltage at the tail end of the transformer area power grid through the negative-sequence current and the zero-sequence current; the PWM unit generates a compensation current control signal; and the IGBT module outputs compensation current to the common coupling point. When three phases are unbalanced, the first disturbance generation circuit accurately injects a disturbance signal to effectively regulate and control the voltage at the tail end of a power grid in a transformer area; and the second disturbance generation circuit analyzes the stability of the tail end of the station area power grid by using coordinate transformation and a PI controller.

Description

Technical Field

[0001] This invention relates to the field of power system voltage regulation technology, and in particular to a method and system for flexible voltage regulation at the end of a distribution network. Background Technology

[0002] In modern power grids, the large-scale integration of distributed generation and the presence of numerous nonlinear loads have led to problems such as voltage fluctuations, voltage deviations, and three-phase imbalances at the end of the distribution network. These issues not only affect the normal operation of power equipment and reduce its lifespan, but may also cause a decline in power quality, resulting in inconvenience for users.

[0003] To determine the voltage status at the end of a distribution network, a specific disturbance signal is typically injected into the distribution area, and the electrical response of the area is monitored and analyzed after the disturbance signal is injected. In the prior art, patent application CN120527947A provides a control method and system for improving the accuracy of SVG disturbance signal generation. The key technical point is that the attenuation of the disturbance signal caused by the SVG DC voltage control is calculated by an observer, and after phase compensation, it is superimposed with the DC voltage setpoint as the outer loop input of the voltage controller. The difference between this input and the DC voltage feedback is then used to obtain the outer loop output of the voltage controller, which is superimposed with the command current disturbance signal as the inner loop input of the current controller. The inner loop current controller, along with PWM modulation commands, controls the SVG operation. This significantly reduces the influence of the DC voltage outer loop on the actual current disturbance signal, enabling the SVG to still output an accurate actual current disturbance signal when command current disturbance signals of various frequencies are injected.

[0004] However, the aforementioned SVG disturbance signal, obtained through a dq-axis decoupling control algorithm, injects disturbance signals into the d-axis and q-axis components respectively. After PI closed-loop control, it is inversely transformed into a three-phase signal and then converted into a PWM signal for control, suitable for three-phase balanced applications. However, for the three-phase imbalance that frequently occurs at the end of the distribution network, the dq-axis decoupling control algorithm, due to its inherent limitations, cannot fully consider the asymmetry between the three phases. This leads to significant deviations in the control of three-phase voltage and current, potentially causing inaccurate control of the voltage or current of a single phase, further exacerbating the three-phase imbalance. Furthermore, this algorithm requires complex calculations and adjustments to the d-axis and q-axis components when handling three-phase imbalance. The calculation process is cumbersome, has poor real-time performance, and struggles to quickly respond to dynamic changes in the voltage at the end of the distribution network, thus affecting the accuracy of the assessment of the voltage status at the end of the distribution network.

[0005] Furthermore, existing voltage regulation devices typically use current transformers to collect current signals to achieve voltage regulation. However, in practical applications, current transformers have a certain measurement error compared to voltage transformers, especially under low current conditions, where the measurement error is more pronounced. In addition, the installation and maintenance costs of current transformers are higher, increasing the overall operating cost and workload. Summary of the Invention

[0006] The purpose of this invention is to provide a method and system for flexible voltage regulation at the end of a distribution network. This method and system can complete voltage regulation at the end of the distribution network by sampling only the three-phase AC voltage, effectively solving the problem of inaccurate judgment of the voltage status at the end of the distribution network under three-phase imbalance in the prior art, and realizing precise regulation of the voltage at the end of the distribution network.

[0007] The specific technology of this application is: a method for flexible voltage regulation at the end of a power grid in a distribution area, the method comprising the following steps: The sampling module measures the voltage at the common coupling point at the end of the power grid in the distribution area. ; The impedance calculation unit obtains the load impedance. ; The current calculation unit uses the voltage at the common coupling point. and the load terminal impedance Calculate the current at the point of common coupling. The common coupling point current ; The current calculation unit calculates the current at the common coupling point. Decompose negative sequence current and zero-sequence current ; The compensation current unit passes through the negative sequence current. and the zero-sequence current Calculate the compensation current component required to maintain voltage stability at the end of the distribution network. The PWM unit generates a compensation current control signal based on the compensation current component to control the IGBT module to output compensation current to the common coupling point.

[0008] Furthermore, the method also includes the following steps: The disturbance generation unit injects a current disturbance signal into the common coupling point. ; The sampling module measures the common coupling point in the current disturbance signal. Voltage change under action ; The impedance calculation unit calculates the impedance based on the voltage change. and the random current disturbance signal Calculate the load impedance The load terminal impedance .

[0009] Furthermore, the disturbance generation unit includes a first disturbance generation circuit, which comprises a phase-locked loop circuit, a voltage control circuit, a disturbance injection circuit, and a current control circuit. The phase-locked loop circuit includes a phase-locked loop (PLL), and the PLL circuit receives the voltage at the common coupling point. Phase angle at the end of the power grid in the output area ; The voltage control circuit includes a first subtractor, a first PI controller, and an inverse PARK converter module. The voltage control circuit receives DC-side voltage. DC side reference voltage Phase angle at the end of the power grid in the distribution area Output current command for phase a outer loop b-phase outer loop output current command and c-phase outer loop output current command ; The disturbance injection circuit includes a disturbance signal input module, a second subtractor, a third subtractor, and a fourth subtractor. The disturbance injection circuit receives the phase angle at the end of the power grid in the distribution area. Phase a outer loop output current command b-phase outer loop output current command and c-phase outer loop output current command Output the command for the intermediate disturbance current of phase a. b-phase intermediate disturbance current command Inter-phase disturbance current command ; The current control circuit includes a first PR controller, a second PR controller, a third PR controller, a fifth subtractor, a sixth subtractor, a seventh subtractor, a first adder, a second adder, and a third adder. The current control circuit receives a command for the intermediate disturbance current of phase a. b-phase intermediate disturbance current command c-phase intermediate disturbance current command Phase a current at the end of the distribution network Phase b current at the end of the distribution network c-phase current at the end of the distribution network Phase a voltage at the end of the distribution network Phase b voltage at the end of the distribution network c-phase voltage at the end of the distribution network Output the first disturbance current control signal.

[0010] Furthermore, the voltage control circuit adjusts the input voltage based on the DC-side reference voltage of the first subtractor. and DC side voltage Calculated voltage fluctuation The voltage fluctuation The a-phase outer loop output current command is obtained after regulation by the first PI controller and transformation by the inverse PARK converter module. b-phase outer loop output current command and c-phase outer loop output current command ; The disturbance injection circuit commands the outer loop output current of phase a. and the perturbation current command for phase a The input to the second subtractor is used to obtain the command for the intermediate disturbance current of phase a. The b-phase outer loop output current command and phase b disturbance current given command The input to the third subtractor is used to obtain the command for the intermediate disturbance current of phase b. The c-phase outer loop output current command and c-phase disturbance current command The input to the fourth subtractor is used to obtain the command for the intermediate disturbance current of phase c. ; The current control circuit gives a command to the intermediate disturbance current of phase a. and the a-phase current at the end of the distribution network The input to the fifth subtractor yields the phase a disturbance current. The command is given to the intermediate disturbance current of phase b. and the b-phase current at the end of the distribution network The input to the sixth subtractor yields the phase b disturbance current. The command is given to the intermediate disturbance current of phase c. c-phase current at the end of the distribution network The input to the seventh subtractor yields the c-phase disturbance current. ; The current control circuit will control the phase a disturbance current. b-phase disturbance current and c-phase disturbance current The voltage is input to the first PR controller, the second PR controller, and the third PR controller respectively, and then converted into the a-phase disturbance voltage. b-phase disturbance voltage and c-phase disturbance voltage The current control circuit will control the phase a disturbance voltage. and the voltage of phase a at the end of the power grid in the distribution area The input is given to the first adder to convert the phase b disturbance voltage. and the B-phase voltage at the end of the power grid in the distribution area The input is given to the second adder to convert the c-phase disturbance voltage. and the C-phase voltage at the end of the power grid in the distribution area The signal is input to the third adder and superimposed to generate the first disturbance current control signal.

[0011] Furthermore, the disturbance generation unit further includes: The second disturbance generation circuit includes a PARK conversion module and a disturbance compensation circuit. The PARK conversion module receives the command for the phase a disturbance current. The b-phase disturbance current command and the given command for the c-phase disturbance current This is then converted into a d-axis disturbance current command in a two-phase rotating coordinate system. and q-axis disturbance current command ; The disturbance compensation circuit includes an eighth subtractor, a ninth subtractor, a fourth and a fifth adder, a second PI controller, a third PI controller, a sixth adder, and a seventh adder. The disturbance compensation circuit receives the d-axis disturbance current command output by the PARK converter module. and the q-axis disturbance current command Output the second disturbance current control signal.

[0012] Furthermore, the disturbance compensation circuit will direct the d-axis disturbance current. Output current command of the outer loop of the d-axis The input to the eighth subtractor yields the d-axis current deviation, which is then used to input the q-axis disturbance current command. and q-axis outer loop output current command The q-axis current deviation is obtained by inputting it into the ninth subtractor. The d-axis current deviation is compared with the actual d-axis current. The input is fed to the fourth adder for superposition to generate the superimposed d-axis current signal; The q-axis current deviation is compared with the actual q-axis current. The signal is input to the fifth adder for superposition to generate the superimposed q-axis current signal; The superimposed d-axis current signal and the superimposed q-axis current signal are respectively input to the second PI controller and the third PI controller for adjustment to obtain the d-axis adjustment amount and the q-axis adjustment amount; The actual current of the d-axis and q-axis actual current Through the phase angle of the power grid terminal in the transformer area Decoupling is performed to obtain the d-axis decoupling current and the q-axis decoupling current; The d-axis decoupling current and the d-axis adjustment amount are input to the sixth adder and superimposed to obtain the d-axis control amount; the q-axis decoupling current and the q-axis adjustment amount are input to the seventh adder and superimposed to obtain the q-axis control amount. The d-axis control quantity and the d-axis adjustment voltage The input is superimposed on the sixth adder to obtain the d-axis control voltage, and the q-axis control quantity is combined with the q-axis adjustment voltage. The inputs are superimposed on the seventh adder to obtain the q-axis control voltage, and the d-axis control voltage and the q-axis control voltage are used as the second disturbance current control signal.

[0013] Furthermore, the first disturbance current generated by the first disturbance generation circuit is used to regulate the voltage at the end of the power grid in the distribution area, and the second disturbance current generated by the second disturbance generation circuit is used to analyze the stability of the end of the power grid in the distribution area.

[0014] Furthermore, the first disturbance generation circuit and the second disturbance generation circuit are controlled by a three-phase balance judgment module. The three-phase balance judgment module monitors the three-phase voltage at the common coupling point and determines whether the common coupling point meets the three-phase balance condition. The three-phase balance judgment module will issue different control commands to the first disturbance generation circuit and the second disturbance generation circuit according to the degree and type of imbalance. When the three phases at the common coupling point are unbalanced, the three-phase balance judgment module controls the first disturbance generation circuit to operate, and regulates the end of the power grid in the distribution area through the first disturbance current to restore the balance of the three-phase voltage. When the three phases at the common coupling point are in balance, the three-phase balance judgment module controls the second disturbance generation circuit to work and uses the second disturbance current to perform stability analysis on the end of the power grid in the distribution area.

[0015] Furthermore, the stability analysis of the distribution network terminal using the second disturbance current includes: The second disturbance current is injected into the end of the power grid of the distribution area, and the voltage and current response of the output port of the power grid end are measured to calculate the external impedance characteristics of the power grid end. The external impedance characteristics are compared with a preset stable impedance range to determine the stability of the power grid end.

[0016] On the other hand, this application provides a flexible voltage regulation system for the end of a distribution grid, characterized in that the system includes at least one processor and a memory, wherein the memory stores instructions that, when executed by at least one processor, implement the steps of any of the above methods.

[0017] The beneficial technical effects of this application are as follows: The flexible voltage regulation method and system for the end of the distribution grid provided in this application effectively solves the problem of inaccurate judgment of the voltage status at the end of the distribution grid under three-phase imbalance in the existing technology.

[0018] The first and second disturbance generation circuits in the disturbance generation unit are designed for the three-phase balanced and three-phase unbalanced states at the end of the distribution network, respectively. The first disturbance generation circuit can accurately inject disturbance signals under three-phase unbalanced conditions to effectively regulate the voltage at the end of the distribution network; the second disturbance generation circuit uses coordinate transformation and a PI controller to analyze the stability of the end of the distribution network under three-phase balanced conditions.

[0019] On the other hand, the flexible voltage regulation device at the end of the transformer substation in this application adopts a current-free sampling design. It only needs to measure the voltage at the common coupling point to calculate the compensation current component required to maintain voltage stability, thus completing the voltage regulation process. This not only avoids the measurement errors and increased costs associated with current transformers but also simplifies the system structure. Attached Figure Description

[0020] Figure 1 This is a flowchart of the flexible voltage regulation method at the end of the distribution network in this application; Figure 2 This is a schematic diagram of the flexible voltage regulation method at the end of the distribution network in this application; Figure 3 This is a schematic diagram of the disturbance generation unit of this application; Figure 4 This is a schematic diagram of the structure of an embodiment of the disturbance generation unit of this application; Figure 5 This is a schematic diagram of an embodiment of the disturbance generation unit of this application; Figure 6 This is a schematic diagram of an embodiment of the disturbance generation unit of this application; Figure 7 This is a schematic diagram of the flexible voltage regulation device at the end of the distribution network in this application; Figure 8 This is a schematic diagram of the flexible voltage regulation system at the end of the distribution network in this application; Detailed Implementation

[0021] In this application, the "transformer distribution area" refers to the area in a power system where the low-voltage side of a transformer directly supplies power; it is the basic unit of power distribution. Within this area, electricity is output from the low-voltage side of the transformer, passes through a series of distribution lines and equipment, and is ultimately delivered to various power users.

[0022] Due to the wide coverage and diverse types of electrical equipment in the distribution area, the load characteristics of the area exhibit strong randomness and volatility. Different users have significantly different electricity demands at different times. For example, residential users experience a substantial increase in electricity load during peak evening hours due to the use of air conditioning, lighting, and other equipment; while industrial users may concentrate their electricity consumption at specific times according to their production plans. This load uncertainty makes the voltage at the end of the distribution area's power grid prone to fluctuations.

[0023] To determine the voltage status at the end of the power grid in a distribution area, a specific disturbance signal is usually injected into the distribution area, and the electrical response of the distribution area is monitored and analyzed after the disturbance signal is injected.

[0024] In the prior art, patent application CN120527947A discloses a control method and system for improving the accuracy of SVG disturbance signal generation. The key technical point is that the attenuation of the disturbance signal caused by the SVG DC voltage control is calculated by an observer, and after phase compensation, it is superimposed with the DC voltage setpoint as the outer loop input of the voltage controller. The difference between this input and the DC voltage feedback is then used to obtain the outer loop output of the voltage controller, which is superimposed with the command current disturbance signal as the inner loop input of the current controller. The inner loop current controller, along with PWM modulation commands, controls the SVG operation. This significantly reduces the influence of the DC voltage outer loop on the actual current disturbance signal, enabling the SVG to still output an accurate actual current disturbance signal when command current disturbance signals of various frequencies are injected.

[0025] However, the aforementioned SVG disturbance signal is generated through a dq-axis decoupling control algorithm, which injects disturbance signals into the d-axis and q-axis components respectively. After PI closed-loop control, the disturbance signal is inversely transformed into a three-phase signal and then converted into a PWM signal for control. This is suitable for three-phase balanced applications. However, in situations where three-phase imbalance frequently occurs at the end of a distribution network, the dq-axis decoupling control algorithm struggles to accurately control the three-phase voltage and current. This results in the injected disturbance signal failing to accurately reflect the actual voltage condition, thus affecting the accuracy of the assessment of the voltage condition at the end of the distribution network.

[0026] To address the above problems, in some embodiments, such as Figure 1 and Figure 2 As shown, this application provides a method for flexible voltage regulation at the end of a distribution network, the method comprising the following steps: The sampling module measures the voltage at the common coupling point at the end of the power grid in the distribution area. ; The common coupling point should be selected as close as possible to the load side at the end of the distribution network to more accurately reflect the actual voltage situation at the end. When selecting the common coupling point, multiple factors need to be considered, such as the geographical distribution of the distribution area, load type, and distribution density. For distribution areas with a large geographical area, common coupling points can be selected in each area according to the load characteristics of different regions to ensure comprehensive monitoring of the voltage situation at the end of the entire distribution area. At the same time, the common coupling point should be selected in a location that is easy to measure and maintain, avoiding areas with strong electromagnetic interference or potential safety hazards.

[0027] Obtain the load impedance ; Load impedance This can be calculated by comprehensively analyzing information such as historical load operating data. Firstly, by analyzing long-term load operating data, we can understand the impedance variation patterns of the load under different time periods and operating conditions. For example, for some industrial loads, their impedance values ​​will differ significantly between peak and off-peak production periods. By modeling this historical data, we can obtain a mathematical model of how the load impedance changes with time and operating conditions.

[0028] By inputting a specific moment, the load impedance at that moment can be roughly estimated. .

[0029] For example, analyzing the operating data of a certain transformer substation over the past year reveals that its impedance value remains relatively stable during daytime production hours, while it rises significantly during nighttime rest periods. Using this data, a linear model of impedance variation over time is established, where a specific time interval is input. At that time, the load impedance can be estimated based on this model. .

[0030] Through the voltage at the common coupling point and the load terminal impedance Calculate the current at the point of common coupling. The common coupling point current ; The current calculation unit calculates the current at the common coupling point. Decompose negative sequence current and zero-sequence current ; Due to the common coupling point current Decompose negative sequence current and zero-sequence current The process specifically includes: First, the current at the common coupling point... Perform a coordinate transformation to convert from a three-phase stationary coordinate system to a two-phase rotating coordinate system.

[0031] By filtering and analyzing the current in a two-phase rotating coordinate system, the frequency and phase characteristics related to the negative sequence component are identified. A bandpass filter is used to filter out the signal corresponding to the frequency of the negative sequence current. The filtered signal is then transformed back to a three-phase stationary coordinate system through an inverse transform, thereby obtaining the accurate negative sequence current. .

[0032] Because zero-sequence current has the same amplitude and phase in a three-phase system, its behavior in a two-phase rotating coordinate system exhibits unique characteristics. By summing the three-phase currents, if a zero-sequence current exists, the summation result will not be zero. Utilizing this characteristic, the summed three-phase currents are processed and filtered to remove other interference signals, ultimately yielding the zero-sequence current. .

[0033] The above-mentioned current at the common coupling point Decompose negative sequence current and zero-sequence current The process is disclosed in the prior art, so it will not be described in detail in this application.

[0034] The compensation current unit passes through the negative sequence current. and the zero-sequence current Calculate the compensation current component required to maintain voltage stability at the end of the power grid in the aforementioned distribution area; In this step, the compensation current unit is supplied with the negative sequence current. and the zero-sequence current The specific process of calculating the compensation current component required to maintain voltage stability at the end of the power grid in the aforementioned distribution area can be summarized as follows: For the negative sequence current and the zero-sequence current The inverted current component is obtained, which is equal in magnitude but opposite in direction to the negative-sequence and zero-sequence currents. Then, based on circuit principles and voltage stability requirements, the coefficients of the inverted current component are adjusted and calculated.

[0035] Next, based on the calculated adjusted current components and combined with the actual power grid operating parameters, the final compensation current components are further determined.

[0036] Similarly, this step is also a publicly available technology, so it will not be described in detail in this application.

[0037] The PWM unit generates a compensation current control signal based on the compensation current component to control the IGBT module to output compensation current to the common coupling point.

[0038] In these embodiments, only the voltage at the common coupling point needs to be measured to calculate the compensation current component required to maintain voltage stability, without the need for a current transformer. This process not only avoids the high cost and installation difficulties associated with current transformers but also makes voltage regulation more precise and flexible. For example, in the event of a sudden load change, this method can quickly calculate the new compensation current component based on the measured voltage and estimated load impedance, adjusting the voltage in a timely manner to ensure the stability of the voltage at the end of the distribution network.

[0039] In some embodiments, to obtain the load impedance more accurately Obtain the load impedance Includes the following steps: The disturbance generation unit injects a current disturbance signal into the common coupling point. ; The sampling module measures the common coupling point in the current disturbance signal. Voltage change under action ; When measuring voltage change At that time, it is necessary to measure Voltage at time and Voltage at time The voltage change is obtained by subtracting the two. In the calculation Voltage change at time Then, through current disturbance signal and Voltage change at time Then, it can be done through the formula Calculate Constant load impedance .

[0040] The impedance calculation unit calculates the impedance based on the voltage change. and the random current disturbance signal Calculate the load impedance The load terminal impedance .

[0041] In these embodiments, the load-side impedance calculated using this method more closely reflects actual operating conditions and has higher accuracy. This is because in actual transformer substations, load characteristics constantly change with time, environment, and other factors. By injecting random current disturbance signals and measuring voltage changes to calculate impedance, these changes can be captured in real time, resulting in a more accurate load-side impedance value at the current moment. Based on this accurate load-side impedance value, the common coupling point current is subsequently calculated. At the same time, the calculation will be more accurate. Accurate load current calculation lays the foundation for subsequent calculations of the negative sequence current. and zero-sequence current This provides a reliable data foundation, which in turn makes the calculated compensation current component required to maintain the voltage stability of the common coupling point more accurate.

[0042] In some embodiments, such as Figure 3 As shown, the disturbance generation unit includes a first disturbance generation circuit, which comprises a phase-locked loop circuit, a voltage control circuit, a disturbance injection circuit, and a current control circuit. The phase-locked loop circuit includes a phase-locked loop (PLL), and the PLL circuit receives the voltage at the common coupling point. Phase angle at the end of the power grid in the output area ; The disturbance injection circuit includes a disturbance signal input module, a second subtractor, a third subtractor, and a fourth subtractor. The disturbance injection circuit receives the phase angle at the end of the power grid in the distribution area. Output phase a disturbance current command b-phase disturbance current command and c-phase disturbance current command ; The voltage control circuit includes a first subtractor, a first PI controller, and an inverse PARK converter module. The voltage control circuit receives DC-side voltage. and DC side reference voltage Output current command for phase a outer loop b-phase outer loop output current command and c-phase outer loop output current command ; The current control circuit includes a first PR controller, a second PR controller, a third PR controller, a fifth subtractor, a sixth subtractor, a seventh subtractor, a first adder, a second adder, and a third adder. The current control circuit receives a command for the intermediate disturbance current of phase a. b-phase intermediate disturbance current command Inter-phase disturbance current command Output the first disturbance current control signal.

[0043] In these embodiments, the first disturbance generation circuit obtains the real-time phase angle θ of the power grid through a phase-locked loop (PLL), which can accurately track the phase change of the power grid voltage and ensure that the generated disturbance current command is synchronized with the power grid voltage.

[0044] The disturbance signal input module generates disturbance current input commands based on the real-time phase angle θ of the power grid. These commands can be dynamically adjusted according to the real-time state of the power grid. Under different load conditions and power grid conditions, the disturbance current input commands can adapt to changes, making the injected disturbance signals more targeted.

[0045] Specifically, the voltage control circuit is based on the DC-side reference voltage input to the first subtractor. and DC side voltage Calculation of voltage fluctuation The voltage fluctuation The a-phase outer loop output current command is obtained after regulation by the first PI controller and transformation by the inverse PARK converter module. b-phase outer loop output current command and c-phase outer loop output current command ; The output current command of the outer loop of phase a and the given command for the disturbance current of phase a The input to the second subtractor is used to obtain the command for the intermediate disturbance current of phase a. The outer loop output current command of b and the given command for the phase b disturbance current The input to the third subtractor is used to obtain the command for the intermediate disturbance current of phase b. The c-phase outer loop output current command and the given command for the c-phase disturbance current The input to the fourth subtractor is used to obtain the command for the intermediate disturbance current of phase c. ; The command is given to the intermediate disturbance current of phase a. and the a-phase current at the end of the distribution network The disturbance current is obtained by inputting it into the fifth subtractor. The command is given to the intermediate disturbance current of phase b. and the b-phase current at the end of the distribution network The disturbance current is obtained by inputting it into the sixth subtractor. The command is given to the intermediate disturbance current of phase c. c-phase current at the end of the distribution network The input to the seventh subtractor yields the c-phase disturbance current. ; The disturbance current of phase a b-phase disturbance current and c-phase disturbance current The voltage is input to the first PR controller, the second PR controller, and the third PR controller respectively, and then converted into the a-phase disturbance voltage. b-phase disturbance voltage and c-phase disturbance voltage ; The disturbance voltage of phase a and the voltage of phase a at the end of the power grid in the distribution area The input is given to the first adder to convert the phase b disturbance voltage. and the B-phase voltage at the end of the power grid in the distribution area The input is given to the second adder to convert the c-phase disturbance voltage. and the C-phase voltage at the end of the power grid in the distribution area The signal is input to the third adder and superimposed to generate the first disturbance current control signal.

[0046] The first disturbance current injected through the first disturbance generation circuit can more accurately reflect the actual voltage condition at the end of a three-phase unbalanced distribution network. Compared with the traditional dq-axis decoupling control algorithm, this method is not affected by three-phase imbalance and can provide a more reliable basis for subsequent calculation of the common coupling point current, decomposition of negative sequence current and zero sequence current, and calculation of compensation current components. This allows for more effective flexible regulation of the voltage at the end of the distribution network and ensures the stability of the voltage at the end of the distribution network.

[0047] In some embodiments, such as Figure 4 As shown, the disturbance generation unit further includes: A second disturbance generation circuit is used to generate a second disturbance current. The second disturbance generation circuit includes a PARK conversion module, which receives a disturbance current generation command generated by the disturbance signal input module. , and This is then converted into a d-axis disturbance current command in a two-phase rotating coordinate system. and q-axis disturbance current command ; The d-axis disturbance current command and the q-axis disturbance current command Respectively compared with the actual current along the d-axis and q-axis actual current By comparing the two, the d-axis current deviation and the q-axis current deviation are obtained. The d-axis current deviation and the q-axis current deviation are respectively input to the second PI controller and the third PI controller for adjustment to obtain the adjusted d-axis adjustment and q-axis adjustment; The actual current of the d-axis and q-axis actual current The d-axis current and q-axis current are obtained by decoupling through the real-time phase angle θ of the power grid. The decoupled d-axis current and q-axis current are added to the adjusted d-axis adjustment amount and q-axis adjustment amount, respectively, to obtain the d-axis control amount and q-axis control amount; The d-axis control quantity and the q-axis control quantity are respectively compared with the d-axis adjustment voltage. and q-axis adjustable voltage The commands are superimposed to obtain the superimposed d-axis adjustment commands and q-axis adjustment commands.

[0048] In these embodiments, under the three-phase balanced state at the end of the distribution network, the second disturbance generation circuit converts the disturbance current command into d-axis and q-axis disturbance current commands in a two-phase rotating coordinate system through the PARK transformation module. This coordinate transformation simplifies the analysis of the three-phase system to a two-phase system, facilitating subsequent control and calculation. By comparing the d-axis and q-axis disturbance current commands with the actual current, the current deviation is obtained, and then adjusted using the second and third PI controllers, enabling precise control of the d-axis and q-axis currents.

[0049] The actual d-axis current and q-axis current are decoupled using the real-time phase angle θ of the power grid, making the control of the d-axis and q-axis independent, avoiding mutual interference and improving control accuracy. The decoupled current is added to the regulation quantity to obtain the control quantity, and then superimposed with the regulation voltage to obtain the regulation command. This operation can dynamically adjust the control parameters according to the real-time state of the power grid, making the injected second disturbance current more in line with actual needs.

[0050] In some embodiments, such as Figure 5 As shown, to make the generated second disturbance current more accurate, the second disturbance generation circuit also includes a disturbance compensation circuit. The disturbance compensation circuit receives the d-axis disturbance current command and the q-axis disturbance current command output by the PARK conversion module, performs compensation processing on the d-axis disturbance current command and the q-axis disturbance current command to generate d-axis compensation voltage and q-axis compensation voltage, and compares the d-axis compensation voltage and the q-axis compensation voltage with the DC-side DC voltage reference value. Compared with the actual DC voltage value The difference values ​​are summed and then input into the first PI controller.

[0051] In these embodiments, the disturbance compensation circuit further optimizes the performance of the second disturbance generation circuit. By compensating the d-axis and q-axis disturbance current commands, d-axis and q-axis compensated voltages that better reflect actual grid conditions can be generated. These compensated voltages are then superimposed on the difference between the DC-side DC voltage reference value and the actual DC voltage value and input to the first PI controller. This allows the first PI controller to comprehensively consider the compensation information of the disturbance current command when adjusting the DC-side voltage, thereby maintaining the stability of the DC-side voltage more accurately.

[0052] In some embodiments, the first disturbance current generated by the first disturbance generation circuit is used to regulate the voltage at the end of the power grid in the distribution area, and the second disturbance current generated by the second disturbance generation circuit is used to analyze the stability of the end of the power grid in the distribution area.

[0053] Specifically, after the first disturbance current is injected into the point of common coupling (PCC), it will cause changes in the PCC voltage and current. By monitoring and analyzing these changes, the compensation current component required to maintain the stability of the PCC voltage can be calculated. Then, the IGBT module can be controlled by the PWM unit to output the compensation current, thereby achieving effective regulation of the voltage at the end of the distribution network.

[0054] The second disturbance current focuses on analyzing the stability of the distribution network's end points. When the second disturbance current is injected into the distribution network's end points, it triggers a series of electrical responses. By analyzing these responses and observing parameters such as the amplitude, frequency, and duration of voltage fluctuations, the stability of the distribution network's end points can be assessed. If, after the injection of the second disturbance current, the voltage fluctuations are large and last for a long time, it indicates poor stability at the distribution network's end points, and further adjustments to system parameters or other measures may be needed to improve stability.

[0055] In some embodiments, such as Figure 6 and Figure 7 As shown, the first disturbance generation circuit and the second disturbance generation circuit are controlled by a three-phase balance judgment module. The three-phase balance judgment module monitors the three-phase voltage at the common coupling point in real time and determines whether the common coupling point is balanced. When an imbalance occurs in the three-phase system, the three-phase balance judgment module will issue different control commands to the first disturbance generation circuit and the second disturbance generation circuit according to the degree and type of imbalance. When the three-phase voltage is unbalanced, the three-phase balance judgment module controls the first disturbance generation circuit to work, and regulates the voltage at the end of the power grid in the distribution area through the first disturbance current in order to restore the balance of the three-phase voltage. When the three-phase voltages are balanced, the three-phase balance judgment module controls the second disturbance generation circuit to work, and uses the second disturbance current to analyze the stability of the power grid terminal in the distribution area.

[0056] In practical applications, these two types of disturbance current signals can be flexibly applied according to the specific conditions of the distribution area. For distribution areas with frequent voltage fluctuations, the injection intensity of the first disturbance current can be increased to adjust the voltage more promptly. For distribution areas with poor stability, the information reflected by the second disturbance current can be focused on, and targeted measures can be taken to enhance the stability of the distribution area. At the same time, intelligent monitoring systems can be used to collect and analyze the data generated by these two disturbance current signals in real time, providing strong support for the operation and management of the distribution area and ensuring the stable and reliable supply of voltage at the end of the power grid.

[0057] At the end of a three-phase balanced distribution network, the second disturbance current generated by the second disturbance generation circuit can cooperate with the first disturbance current generated by the first disturbance generation circuit. The first disturbance current can accurately reflect the actual voltage condition under three-phase imbalance, while the second disturbance current can achieve precise current control under three-phase balance. The combination of the two can further improve the accuracy of judging the voltage condition at the end of the distribution network and the effectiveness of voltage regulation.

[0058] In summary, this flexible voltage regulation method for the end of a distribution network based on disturbance current signals achieves stable voltage regulation and accurate analysis of system stability by accurately acquiring load impedance, designing a reasonable disturbance current generation circuit, and employing effective control strategies. It overcomes the limitations of traditional methods under three-phase imbalance conditions, dynamically adjusting control parameters according to the real-time state of the power grid, thus improving the accuracy of voltage regulation and the reliability of the system. In practical applications, combined with an intelligent monitoring system, real-time analysis of the data generated by the two disturbance current signals provides comprehensive and accurate information for the operation and management of the distribution network, helping power departments to promptly identify and resolve problems and ensure the power quality for end users. With the continuous development of the power system and the increasing demands of users for power quality, this method has broad application prospects and promotional value, and is expected to be applied and optimized in more distribution network areas, further improving the overall operating efficiency and stability of the power system.

[0059] like Figure 8 As shown, this application also provides a flexible voltage regulation system for the end of a distribution grid. The system includes at least one processor, a memory, and an input device. The input device is used to obtain input from the outside. The memory stores instructions. When the instructions are executed by at least one processor, the steps of the method described in the method embodiment are implemented.

[0060] The embodiments and functional operations of the subject matter described in this specification can be implemented in the following ways: digital electronic circuits, tangibly implemented computer software or firmware, computer hardware, including the structures disclosed in this specification and their equivalents, or combinations thereof. Embodiments of the subject matter described in this specification can be implemented as one or more computer programs, that is, one or more modules of computer program instructions encoded on one or more tangible non-transitory program carriers, for execution by a data processing device or to control the operation of the data processing device.

[0061] Alternatively or additionally, program instructions may be encoded on artificially generated propagation signals, such as machine-generated electrical, optical, or electromagnetic signals, which are then generated as coded information to be transmitted to an appropriate receiver device executed by data processing equipment. The computer storage medium may be a machine-readable storage device, a machine-readable storage substrate, a random or serial access memory device, or one or more combinations of the above.

[0062] While this specification contains numerous specific implementation details, these should not be construed as limiting the scope of any invention or the scope of the claims, but rather as descriptions of features that can embody specific embodiments of a particular invention. Specific features described in this specification within the context of an independent embodiment may also be implemented in combination with a single embodiment. Conversely, various features described within the context of a single embodiment may also be implemented independently in multiple embodiments, or in any suitable sub-combination. Furthermore, while features may be described for combination and even initially claimed in this way, one or more features from a claimed combination may be removed from that combination in some cases, and the claimed combination may be redirected to a sub-combination or a variation thereof.

Claims

1. A method for flexible voltage regulation at the end of a distribution network, characterized in that, The method includes the following steps: The sampling module measures the voltage at the common coupling point at the end of the power grid in the distribution area. ; The impedance calculation unit obtains the load impedance. ; The current calculation unit uses the voltage at the common coupling point. and the load terminal impedance Calculate the current at the point of common coupling. ,in ; The current calculation unit calculates the current at the common coupling point. Decompose into negative sequence current and zero-sequence current ; The compensation current unit passes through the negative sequence current. and the zero-sequence current Calculate the compensation current component required to maintain voltage stability at the end of the power grid in the aforementioned distribution area; The PWM unit generates a compensation current control signal based on the compensation current component. The IGBT module outputs a compensation current to the common coupling point according to the compensation current control signal.

2. The method for flexible voltage regulation at the end of a distribution network as described in claim 1, characterized in that, The method further includes the following steps: The disturbance generation unit injects a current disturbance signal into the common coupling point. ; The sampling module measures the common coupling point in the current disturbance signal. Voltage change under action ; The impedance calculation unit calculates the voltage change based on the voltage change. and the current disturbance signal Calculate the load terminal impedance ,in .

3. The method for flexible voltage regulation at the end of a distribution network as described in claim 2, characterized in that, The disturbance generation unit includes a first disturbance generation circuit, which includes a phase-locked loop circuit, a voltage control circuit, a disturbance injection circuit, and a current control circuit. The phase-locked loop circuit includes a phase-locked loop (PLL), and the PLL circuit receives the voltage at the common coupling point. Phase angle at the end of the power grid in the output area ; The voltage control circuit includes a first subtractor, a first PI controller, and an inverse PARK converter module. The voltage control circuit receives DC-side voltage. DC side reference voltage Phase angle at the end of the power grid in the distribution area Output current command for phase a outer loop b-phase outer loop output current command and c-phase outer loop output current command ; The disturbance injection circuit includes a disturbance signal input module, a second subtractor, a third subtractor, and a fourth subtractor. The disturbance injection circuit receives the phase angle at the end of the power grid in the distribution area. The outer loop output current command of phase a The b-phase outer loop output current command and the c-phase outer loop output current command Output the intermediate disturbance current command of phase a. b-phase intermediate disturbance current command Inter-phase disturbance current command ; The current control circuit includes a first PR controller, a second PR controller, a third PR controller, a fifth subtractor, a sixth subtractor, a seventh subtractor, a first adder, a second adder, and a third adder. The current control circuit receives the commanded intermediate disturbance current of phase a. The command for the intermediate disturbance current of phase b. The command for the intermediate disturbance current of phase c. Phase a current at the end of the distribution network Phase b current at the end of the distribution network c-phase current at the end of the distribution network Phase a voltage at the end of the distribution network Phase b voltage at the end of the distribution network c-phase voltage at the end of the distribution network Output the first disturbance current control signal.

4. The method for flexible voltage regulation at the end of a distribution network as described in claim 3, characterized in that, The voltage control circuit is based on the DC-side reference voltage input to the first subtractor. and the DC side voltage Calculated voltage fluctuation The voltage fluctuation The outer loop output current command of phase a is obtained after adjustment by the first PI controller and transformation by the inverse PARK converter module. The b-phase outer loop output current command and the c-phase outer loop output current command ; The disturbance injection circuit commands the outer loop output current of phase a. and the perturbation current command for phase a The input to the second subtractor is used to obtain the command for the intermediate disturbance current of phase a. The b-phase outer loop output current command and phase b disturbance current given command The input to the third subtractor is used to obtain the command for the intermediate disturbance current of phase b. The c-phase outer loop output current command and c-phase disturbance current command The input to the fourth subtractor is used to obtain the command for the intermediate disturbance current of phase c. ; The current control circuit gives a command to the intermediate disturbance current of phase a. and the a-phase current at the end of the power grid in the aforementioned distribution area The input to the fifth subtractor yields the phase a disturbance current. The command is given to the intermediate disturbance current of phase b. and the b-phase current at the end of the power grid in the aforementioned distribution area The input to the sixth subtractor yields the phase b disturbance current. The command is given to the intermediate disturbance current of phase c. and the c-phase current at the end of the power grid in the aforementioned distribution area The c-phase disturbance current is obtained by inputting it into the seventh subtractor. ; The current control circuit will control the phase a disturbance current. The b-phase disturbance current and the c-phase disturbance current The voltage is input to the first PR controller, the second PR controller, and the third PR controller respectively, and then adjusted to convert it into phase a disturbance voltage. b-phase disturbance voltage and c-phase disturbance voltage ; The current control circuit will control the phase a disturbance voltage. and the phase a voltage at the end of the power grid in the aforementioned distribution area The input is given to the first adder to convert the b-phase disturbance voltage. and the b-phase voltage at the end of the power grid in the aforementioned distribution area The input is given to the second adder to convert the c-phase disturbance voltage. and the c-phase voltage at the end of the power grid in the aforementioned distribution area The signal is input to the third adder and superimposed to generate the first disturbance current control signal.

5. The method for flexible voltage regulation at the end of a distribution network as described in claim 4, characterized in that, The disturbance generation unit further includes: The second disturbance generation circuit includes a PARK conversion module and a disturbance compensation circuit. The PARK conversion module receives the command for the phase a disturbance current. The b-phase disturbance current command and the given command for the c-phase disturbance current This is then converted into a d-axis disturbance current command in a two-phase rotating coordinate system. and q-axis disturbance current command ; The disturbance compensation circuit includes an eighth subtractor, a ninth subtractor, a fourth and a fifth adder, a second PI controller, a third PI controller, a sixth adder, and a seventh adder. The disturbance compensation circuit receives the d-axis disturbance current command output by the PARK converter module. and the q-axis disturbance current command Output the second disturbance current control signal.

6. The method for flexible voltage regulation at the end of a distribution network as described in claim 5, characterized in that, The disturbance compensation circuit will command the d-axis disturbance current. Output current command of the outer loop of the d-axis The input to the eighth subtractor yields the d-axis current deviation, which is then used to input the q-axis disturbance current command. and q-axis outer loop output current command The q-axis current deviation is obtained by inputting it into the ninth subtractor. The d-axis current deviation is compared with the actual d-axis current. The input is fed into the fourth adder to generate a superimposed d-axis current signal; The q-axis current deviation is compared with the actual q-axis current. The input is fed into the fifth adder to generate a superimposed q-axis current signal; The superimposed d-axis current signal and the superimposed q-axis current signal are respectively input to the second PI controller and the third PI controller for adjustment to obtain the d-axis adjustment amount and the q-axis adjustment amount; The actual current of the d-axis and q-axis actual current Through the phase angle of the power grid terminal in the transformer area Decoupling is performed to obtain the d-axis decoupling current and the q-axis decoupling current; The d-axis decoupling current and the d-axis adjustment amount are input to the sixth adder and superimposed to obtain the d-axis control amount; the q-axis decoupling current and the q-axis adjustment amount are input to the seventh adder and superimposed to obtain the q-axis control amount. The d-axis control quantity and the d-axis adjustment voltage The input is superimposed on the sixth adder to obtain the d-axis control voltage, and the q-axis control quantity is combined with the q-axis adjustment voltage. The inputs are superimposed on the seventh adder to obtain the q-axis control voltage, and the d-axis control voltage and the q-axis control voltage are used as the second disturbance current control signal.

7. The method for flexible voltage regulation at the end of a distribution network as described in claim 6, characterized in that, The first disturbance current generated by the first disturbance generation circuit is used to regulate the voltage at the end of the power grid in the distribution area, and the second disturbance current generated by the second disturbance generation circuit is used to analyze the stability of the end of the power grid in the distribution area.

8. The method for flexible voltage regulation at the end of a distribution network as described in claim 7, characterized in that, The first disturbance generation circuit and the second disturbance generation circuit are controlled by a three-phase balance judgment module. The three-phase balance judgment module monitors the three-phase voltage at the common coupling point and determines whether the common coupling point meets the three-phase balance condition. The three-phase balance judgment module issues different control commands to the first disturbance generation circuit and the second disturbance generation circuit according to the degree and type of imbalance. When the three phases at the common coupling point are unbalanced, the three-phase balance judgment module controls the first disturbance generation circuit to operate, and regulates the end of the power grid in the distribution area through the first disturbance current to restore the balance of the three-phase voltage. When the three phases at the common coupling point are in balance, the three-phase balance judgment module controls the second disturbance generation circuit to work and uses the second disturbance current to perform stability analysis on the end of the power grid in the distribution area.

9. The method for flexible voltage regulation at the end of a distribution network as described in claim 8, characterized in that, The stability analysis of the distribution network terminal using the second disturbance current includes: The second disturbance current is injected into the end of the power grid of the distribution area, the voltage and current response of the output port of the end of the power grid of the distribution area are measured, and the external impedance characteristics of the end of the power grid of the distribution area are calculated. The stability of the power grid terminal in the distribution area is determined by comparing the external impedance characteristics with a preset stable impedance range.

10. A flexible voltage regulation system for the end of a distribution network, characterized in that, The system includes at least one processor and a memory storing instructions that, when executed by the at least one processor, perform the steps of the method according to any one of claims 1-9.

Images