Power system voltage control method and device based on dynamic and steady state collaborative correction

Abstract

The invention provides a power system voltage control method and device based on dynamic steady state collaborative correction, and the method comprises the steps: building an electromagnetic transient model for a preset voltage node in electromagnetic transient simulation software PSCAD, simplifying a power grid with the electrical distance to a target region exceeding a preset distance into a dynamic Thevenin equivalent model, initializing load flow calculation in the BPA to obtain a dynamic-steady state hybrid model; updating dynamic Thevenin equivalent parameters of the power system in real time according to the data of the phasor measurement unit of the power system, and synchronizing the dynamic Thevenin equivalent parameters to the BPA; based on the dynamic-steady state hybrid model, the transient overvoltage of the power system is suppressed within the time shorter than the first preset duration, and the steady state voltage of the power system is optimized within the time shorter than the second preset duration in combination with wide-area coordination control, so that the parameter bidirectional correction of the dynamic and steady state models is realized, and the head end voltage prediction error is reduced. And the voltage control robustness is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of power system simulation control, and particularly to a power system voltage control method and device based on dynamic-steady state collaborative correction. Background Art

[0002] With the rapid development of modern power systems, ultra-high voltage (UHV) transmission technology has been widely applied because it can achieve large-capacity and long-distance power transmission. However, during the operation of UHV lines, load shedding may occur, which can have a significant impact on the steady-state voltage of the lines. Load shedding refers to the sudden disappearance of the load on a transmission line due to reasons such as fault removal or sudden load reduction. When load shedding occurs on a UHV line, the capacitive effect of the line will cause the line voltage to rise rapidly, possibly exceeding the insulation withstand level of the equipment, thereby damaging the equipment and even leading to system voltage instability and large-scale power outages in severe cases. Therefore, accurately predicting and controlling the change trend of the voltage at the line head after load shedding is crucial for ensuring the safe and stable operation of the power system.

[0003] Currently, the commonly used methods for controlling the voltage of the bus at the line head are mainly the linear calculation method or the power flow calculation method. Among them, the linear calculation method performs Thevenin equivalent modeling of the power grid based on the Power Systems Computer Aided Design (PSCAD) software, and determines the control value of the head voltage by calculating the voltage difference before and after tripping; while the power flow calculation method relies on the power flow simulation of the Berkeley Power Analysis (BPA) software for steady-state power flow calculation of the power system, and checks the head voltage by adjusting reactive power compensation equipment. However, there are many problems with these two methods in voltage pre-control calculation. For example, the dynamic and steady-state models are disjointed. The Thevenin equivalent model ignores the dynamic response of generator excitation regulation and reactive power compensation equipment, resulting in a low predicted value of the head voltage under heavy load; while the BPA power flow calculation relies on steady-state assumptions, may overestimate the system's reactive power regulation ability, and cannot capture the risk of transient overvoltage. Summary of the Invention

[0004] The present invention provides a power system voltage control method and device based on dynamic-steady state collaborative correction to solve the technical problem of low accuracy in voltage control in the existing power system.

[0005] On the one hand, the present invention provides a power system voltage control method based on dynamic-steady state collaborative correction, including: An electromagnetic transient model is established for the preset voltage nodes in the power system electromagnetic transient simulation software PSCAD. The power grid with an electrical distance exceeding the preset distance from the target area is simplified into a dynamic Thevenin equivalent model. The power flow calculation is initialized in BPA, the generators are set as PV nodes, the loads are set as PQ nodes, and the parameters of the reactive power compensation equipment are configured to obtain a dynamic-steady state hybrid model; The dynamic Thevenin equivalent parameters of the power system are updated in real time according to the data of the power system phasor measurement unit and synchronized to BPA; Based on the dynamic-steady state hybrid model, the transient overvoltage of the power system is suppressed within a time less than the first preset duration, and the steady-state voltage of the power system is optimized within a time less than the second preset duration in combination with wide-area coordinated control; Based on the dynamic-steady state hybrid model, the control effect of the power system is verified, and the control strategy is adaptively adjusted according to the actual situation of the power system.

[0006] According to a power system voltage control method based on dynamic steady-state collaborative correction provided by the present invention, an electromagnetic transient model is established for preset voltage nodes in the power system electromagnetic transient simulation software PSCAD, and the power grid with an electrical distance exceeding the preset distance from the target area is simplified into a dynamic Thevenin equivalent model, including: Calculate the sensitivity of the voltage of each voltage node in the power system to the power change, and analyze the topological structure of the power system. Based on the sensitivity and topological structure, obtain the preset voltage nodes; Configure the model parameters of the electromagnetic transient model based on the parameter file of BPA to make the model parameters consistent with the BPA steady-state data; For the power grid with an electrical distance exceeding the preset distance from the target area, use the short-circuit capacity method or the N-1 fault scanning method to calculate the equivalent impedance and equivalent voltage source to obtain a dynamic Thevenin equivalent model.

[0007] According to a power system voltage control method based on dynamic steady-state collaborative correction provided by the present invention, calculate the sensitivity of the voltage of each voltage node in the power system to the power change, and analyze the topological structure of the power system. Based on the sensitivity and topological structure, obtain the preset voltage nodes, including: Calculate the ratio of the voltage of each voltage node in the power system to the corresponding power as the sensitivity; Sort the sensitivities from small to large; According to the sorting, select the voltage nodes corresponding to the preset number of sensitivities, and the voltage nodes located in the backbone network, new energy collection points and load centers in the topological structure as the preset voltage nodes.

[0008] According to a power system voltage control method based on dynamic steady-state collaborative correction provided by the present invention, the short-circuit capacity method is used to calculate the equivalent impedance, including: Based on the power flow calculation results, the short-circuit capacity is obtained; Calculate the ratio of the square of the grid-connected point voltage to the short-circuit capacity as the equivalent impedance; Use the N-1 fault scanning method to calculate the equivalent impedance, including: Simulate a three-phase short-circuit fault at a preset node in PSCAD to obtain the fault current; Calculate the ratio of the pre-fault voltage to the fault current as the equivalent impedance.

[0009] According to a power system voltage control method based on dynamic-steady state collaborative correction provided by the present invention, the dynamic Thevenin equivalent parameters of the power system are updated in real time according to the phasor measurement unit data of the power system and synchronized to BPA, including: Sample the preset nodes in the power system to obtain the sampled data of voltage and current; Preprocess the sampled data; Based on the preprocessed sampled data, use the sensitivity method to update the dynamic Thevenin equivalent parameters in real time; Synchronize the updated dynamic Thevenin equivalent parameters to BPA through the data interface.

[0010] According to a power system voltage control method based on dynamic-steady state collaborative correction provided by the present invention, use the sensitivity method to update the dynamic Thevenin equivalent parameters in real time, including: Use the sensitivity method to compare the voltage change and current change between the current cycle and the previous cycle; Determine the ratio of the voltage change to the current change as the impedance change; Based on the impedance change, the smoothing coefficient of the impedance change, and the equivalent impedance of the previous cycle, obtain the updated equivalent impedance; Based on the updated equivalent impedance, the current value and voltage value of the current cycle, obtain the updated voltage value.

[0011] According to a power system voltage control method based on dynamic-steady state collaborative correction provided by the present invention, the impedance change is expressed by the following formula: ; Where, is the impedance change, is the voltage value of the previous cycle, is the current value of the previous cycle, k represents the cycle, is the voltage value of the current cycle, is the current value of the current cycle; The updated equivalent impedance is expressed by the following formula: ; is the updated equivalent impedance, is the equivalent impedance of the previous cycle, is the smoothing coefficient.

[0012] According to a power system voltage control method based on dynamic-steady state collaborative correction provided by the present invention, the updated dynamic Thevenin equivalent parameters are synchronized to BPA through a data interface, including: Call the interface of BPA through a Python script to synchronize the updated dynamic Thevenin equivalent parameters to BPA; If the parameter impedance change rate and the voltage source phase change reach the set threshold after BPA is updated, then perform a power flow recalculation; Read the generator voltage setting value and reactive power compensation instruction output by BPA and send them back to PSCAD.

[0013] According to a power system voltage control method based on dynamic-steady state collaborative correction provided by the present invention, suppress the transient overvoltage of the power system within a time less than the first preset duration, including: When it is detected that the transient overvoltage peak exceeds the first preset voltage threshold or the voltage change rate exceeds the preset change threshold, calculate the reactive power output according to the preset proportional gain, integral gain and reserved safety margin to quickly respond and suppress the transient overvoltage; When the steady-state voltage deviation exceeds the second preset voltage threshold and the duration exceeds the first preset duration threshold, adjust the step size according to the preset ratio. If the number of adjustments reaches the preset number within the preset time period, start the locking condition; Combine wide-area coordinated control to optimize the steady-state voltage of the power system within a time less than the second preset duration, including: Calculate the reactive power sensitivity of each generator to the voltage at the head end, select the two units with the highest sensitivity, and adjust the excitation voltage instruction according to the voltage deviation and the preset proportional gain of the automatic voltage regulator; When the voltage is lower than the third preset voltage threshold, the duration exceeds the second preset duration, and all reactive power resources have been exhausted, shed loads according to the priority and gradient.

[0014] On the other hand, the present invention also provides a power system voltage control device based on dynamic-steady state collaborative correction, including: A dynamic-steady state module for establishing an electromagnetic transient model for preset voltage nodes in the power system electromagnetic transient simulation software PSCAD, simplifying the power grid with an electrical distance to the target area exceeding the preset distance into a dynamic Thevenin equivalent model, and initializing the power flow calculation in BPA, setting the generator as a PV node, the load as a PQ node, and configuring the parameters of reactive power compensation equipment to obtain a dynamic-steady state hybrid model; The parameter update module is used to update the dynamic Thevenin equivalent parameters of the power system in real time according to the phasor measurement unit data of the power system and synchronize them to BPA; The voltage hierarchical control module is used to suppress the transient overvoltage of the power system within a time less than the first preset duration based on the dynamic-steady-state hybrid model, and optimize the steady-state voltage of the power system within a time less than the second preset duration in combination with wide-area coordinated control; The verification module is used to verify the control effect of the power system based on the dynamic-steady-state hybrid model and adaptively adjust the control strategy according to the actual situation of the power system.

[0015] The power system voltage control method and device based on dynamic steady-state collaborative correction provided by the present invention establish an electromagnetic transient model for preset voltage nodes in the power system electromagnetic transient simulation software PSCAD, simplify the power grid whose electrical distance to the target area exceeds the preset distance into a dynamic Thevenin equivalent model, and initialize the power flow calculation in BPA to obtain a dynamic-steady-state hybrid model; update the dynamic Thevenin equivalent parameters of the power system in real time according to the phasor measurement unit data of the power system and synchronize them to BPA; suppress the transient overvoltage of the power system within a time less than the first preset duration based on the dynamic-steady-state hybrid model, and optimize the steady-state voltage of the power system within a time less than the second preset duration in combination with wide-area coordinated control; realize the two-way correction of the parameters of the dynamic (PSCAD) and steady-state (BPA) models through the dynamic Thevenin parameter update and the hybrid simulation framework, reduce the prediction error of the head-end voltage, and improve the voltage control robustness in combination with transient overvoltage suppression and steady-state reactive power optimization, supporting the high-proportion new energy access scenario. Description of the Drawings

[0016] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0017] Figure 1 It is a schematic flowchart of the power system voltage control method based on dynamic steady-state collaborative correction provided by the embodiments of the present invention; Figure 2 It is a schematic diagram of the power grid structure of the power system provided by the embodiments of the present invention; Figure 3 It is a schematic structural diagram of the power system voltage control device based on dynamic steady-state collaborative correction provided by the embodiments of the present invention; Figure 4 It is a schematic structural diagram of the electronic device provided by the embodiments of the present invention. Detailed Embodiments

[0018] To make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions in the present invention will be clearly and completely described below with reference to the accompanying drawings in the present invention. Apparently, the described embodiments are some but not all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present invention without making creative efforts belong to the scope of protection of the present invention.

[0019] Figure 1 It is a schematic flow chart of a power system voltage control method based on dynamic steady-state collaborative correction provided by an embodiment of the present invention.

[0020] See Figure 1 , the power system voltage control method based on dynamic steady-state collaborative correction may include the following steps 101 to 104.

[0021] Step 101: Establish an electromagnetic transient model for a preset voltage node in the power system electromagnetic transient simulation software PSCAD, simplify the power grid whose electrical distance to the target area exceeds a preset distance into a dynamic Thevenin equivalent model, and initialize the power flow calculation in BPA, set the generator as a PV node, the load as a PQ node, and configure the parameters of the reactive power compensation device to obtain a dynamic-steady state hybrid model.

[0022] In this step, in the power system power flow calculation, a PV node refers to a node with a given voltage amplitude and active power, usually used to represent a generator node. A PQ node refers to a node with a given active power and reactive power, usually used to represent a load node. The power grid whose electrical distance to the target area exceeds the preset distance can also be called the remote power grid. The preset voltage node generally can refer to the head and tail generators and new energy power stations, etc. While establishing an electromagnetic transient model for the preset voltage node, the dynamic characteristics can also be retained. For example, the excitation regulation and fan control, etc. can be retained. The parameters of the reactive power compensation device can refer to the reactive power output range, response speed, and control mode, etc. The parameter configuration of the electromagnetic transient model can be consistent with the data in the corresponding BPA and can be configured according to the parameter file in BPA.

[0023] When configuring BPA, the initial Thevenin parameters (such as the initial Thevenin equivalent voltage and the initial Thevenin equivalent impedance) can be exported from PSCAD to format the BPA cards. Set the generators as PV buses (voltage control mode), and SVC / SVG as PQ buses (reactive power output adjustable), and define the transformer tap adjustment step (such as ±1.25%). Transmit data (Thevenin equivalent voltage and voltage source parameters) in real time through PMU to generate dynamically updated (Thevenin equivalent voltage and voltage source parameters) parameters. It is also possible to verify the matching between the initial power of the generator and the power flow at the dynamic level to avoid simulation divergence; perform BPA power flow iteration at the static level to ensure the consistency between the Thevenin equivalent and the system power balance. Before the first power flow calculation, at least 3 iterations need to be performed in BPA to ensure the matching between the Thevenin equivalent voltage and the generator setting value.

[0024] Establish an electromagnetic transient model for the preset voltage buses in the power system electromagnetic transient simulation software PSCAD, and simplify the power grid whose electrical distance to the target area exceeds the preset distance into a dynamic Thevenin equivalent model, which may include: Calculate the sensitivity of the voltage of each voltage bus in the power system to the change of power (such as active power and reactive power), and analyze the topology of the power system. Based on the sensitivity and topology, obtain the preset voltage buses; Configure the model parameters of the electromagnetic transient model based on the parameter file of BPA to make the model parameters consistent with the BPA steady-state data; For the power grid whose electrical distance to the target area exceeds the preset distance, calculate the equivalent impedance and equivalent voltage source using the short-circuit capacity method or the N-1 fault scanning method to obtain the dynamic Thevenin equivalent model.

[0025] Calculate the sensitivity of the voltage of each voltage bus in the power system to the change of power, and analyze the topology of the power system. Based on the sensitivity and topology, obtain the preset voltage buses, which may include: Calculate the ratio of the voltage of each voltage bus in the power system to the corresponding power as the sensitivity; Sort the sensitivities from small to large; According to the sorting, select the voltage buses corresponding to the preset number of sensitivities, and the voltage buses located in the backbone network, new energy collection points and load centers in the topology (such as 500 kV hub substations, grid connection points of wind farms) as the preset voltage buses.

[0026] Among them, the preset quantity can be set. For example, it can be set to the top 10%. The backbone network is the core part of the power system. It is responsible for transmitting electricity from the power plant to each load center and substation. The backbone network usually consists of high-voltage transmission lines. The new energy collection point refers to the location where the electricity of multiple new energy power plants (such as wind farms, photovoltaic power plants) is collected to a node and the electricity is transmitted to the backbone power grid through this node. The load center refers to the area or node with a large electricity demand in the power system, usually the city center, industrial area or large commercial area.

[0027] The equivalent impedance is calculated by the short-circuit capacity method, including: Based on the power flow calculation results, the short-circuit capacity is obtained; Calculate the ratio of the square of the grid connection point voltage to the short-circuit capacity as the equivalent impedance. Specifically, it is shown in the following formula (1): (1); Where, is the short-circuit capacity of the system, is the grid connection point voltage, is the equivalent impedance.

[0028] The equivalent impedance is calculated by the N-1 fault scanning method, including: Simulate the three-phase short-circuit fault of the preset node (such as the point of common coupling, i.e., PCC) in PSCAD to obtain the fault current; Calculate the ratio of the voltage before the fault to the fault current as the equivalent impedance. Specifically, it is shown in the following formula (2): (2); Where, is the fault current, is the voltage before the fault.

[0029] The calculation method of the equivalent voltage source is shown in the following formula (3): (3); Where, is the base current, is the equivalent voltage source. The calculation of the base current is shown in the following formula (4): (4); Where, is the base power, is the base voltage.

[0030] Step 102: Update the dynamic Thevenin equivalent parameters of the power system in real time according to the phasor measurement unit data of the power system and synchronize them to BPA.

[0031] Step 102 may specifically include: Sample preset nodes in the power system to obtain sampling data of voltage and current; Preprocess the sampling data; Based on the preprocessed sampling data, use the sensitivity method to update the dynamic Thevenin equivalent parameters in real time; Synchronize the updated dynamic Thevenin equivalent parameters to BPA through the data interface.

[0032] Among them, the phasor measurement unit (PMU) layout principle is generally: Key monitoring points (preset nodes): the head bus (control voltage node), the grid connection point of the new energy power station, and both ends of the main transmission line.

[0033] Redundant configuration: Dual PMUs (primary and standby mode) are configured for key nodes, the sampling rate ≥ 4 kHz, and the time synchronization accuracy ≤ 1 μs (based on the IEEE 1588 protocol).

[0034] Among them, the preprocessing mainly includes data filtering and abnormal data processing. Data filtering may specifically include: FIR low-pass filtering: The cut-off frequency is 100 Hz to eliminate high-frequency noise (such as switch harmonics); Recursive average filtering: The window width is 10 ms (40 sampling points) to smooth transient disturbances.

[0035] Abnormal data processing may mainly include: If the voltage mutation rate is greater than 10 kV, mark it as fault data and switch to the standby PMU; If the data is continuously lost for more than 5 ms, enable linear interpolation compensation.

[0036] Step 103: Based on the dynamic-steady state hybrid model, suppress the power system transient overvoltage within a time less than the first preset duration, and optimize the power system steady-state voltage within a time less than the second preset duration in combination with wide-area coordinated control.

[0037] Step 104: Based on the dynamic-steady state hybrid model, verify the power system control effect and adaptively adjust the control strategy according to the actual situation of the power system.

[0038] In this embodiment, an electromagnetic transient model is established for the preset voltage node in the power system electromagnetic transient simulation software PSCAD. The power grid with an electrical distance exceeding the preset distance from the target area is simplified into a dynamic Thevenin equivalent model, and the power flow calculation is initialized in BPA to obtain a dynamic-steady state hybrid model. The dynamic Thevenin equivalent parameters of the power system are updated in real time according to the data of the power system phasor measurement unit and synchronized to BPA. Based on the dynamic-steady state hybrid model, the transient overvoltage of the power system is suppressed within a time less than the first preset duration, and the steady-state voltage of the power system is optimized within a time less than the second preset duration in combination with wide-area coordinated control. Through the dynamic Thevenin parameter update and the hybrid simulation framework, the two-way correction of the parameters of the dynamic (PSCAD) and steady-state (BPA) models is realized, the prediction error of the head-end voltage is reduced, and the voltage control robustness is improved in combination with transient overvoltage suppression and steady-state reactive power optimization, supporting high-proportion new energy access scenarios.

[0039] In one embodiment of this specification, the sensitivity method is used to update the dynamic Thevenin equivalent parameters in real time, including: Using the sensitivity method to compare the voltage change and current change between the current cycle and the previous cycle; Determine the ratio of the voltage change and current change as the impedance change; Based on the impedance change, the smoothing coefficient of the impedance change, and the equivalent impedance of the previous cycle, obtain the updated equivalent impedance; Based on the updated equivalent impedance, the current value and voltage value of the current cycle, obtain the updated voltage value.

[0040] In this embodiment, by comparing the voltage and current changes between the current cycle and the previous cycle, the impedance change is determined, so as to more accurately update the equivalent impedance and voltage value. Based on the impedance change and the smoothing coefficient, the equivalent impedance is dynamically adjusted, enabling the system to adapt to the real-time changes of the power system.

[0041] In one embodiment of this specification, the impedance change is represented by the following formula (5): (5); Wherein, is the impedance change, is the voltage value of the previous cycle, is the current value of the previous cycle, k represents the cycle, is the voltage value of the current cycle, is the current value of the current cycle; The updated equivalent impedance is represented by the following formula (6): (6); Wherein, is the updated equivalent impedance, is the equivalent impedance of the previous cycle, is the smoothing coefficient.

[0042] In addition, the updated voltage source can be expressed as , as shown in the following formula (7): (7).

[0043] In this embodiment, generally, in a high-noise scenario (such as near a wind farm), takes a value of 0.2, and in a steady scenario, takes a value of 0.5. By providing specific mathematical formulas to calculate the impedance change amount and update the equivalent impedance, the accurate update of the dynamic Thevenin equivalent parameters of the power system can be realized, which can improve the accuracy of the power system model, make it more conform to the actual operation conditions, and further enhance the reliability and effectiveness of the power system voltage control.

[0044] In an embodiment of this specification, the updated dynamic Thevenin equivalent parameters are synchronized to BPA through a data interface, including: Calling the interface of BPA through a Python script to synchronize the updated dynamic Thevenin equivalent parameters to BPA; If the impedance change rate and the voltage source phase change after the BPA update reach the set threshold, then a power flow recalculation is performed; Read the generator voltage setting value and reactive power compensation instruction output by BPA and send them back to PSCAD.

[0045] In this embodiment, the real-time synchronization between the dynamic Thevenin equivalent parameters of the power system and the BPA software is realized through an automated data interface, ensuring the consistency between the power system simulation and the actual operation data, helping to improve the accuracy of the power flow calculation, and thus optimizing the voltage control and overall performance of the power system. Synchronize the updated dynamic Thevenin equivalent parameters to BPA. For example, for the Thevenin bus voltage, directly modify the VM (equivalent voltage source) field in the.dat file; for the equivalent line parameters, update the R field (resistance value of the equivalent line) and the X field (reactance value of the equivalent line).

[0046] If the impedance change rate and the voltage source phase change after the BPA update reach the set threshold, then a power flow recalculation is performed. For example, the set threshold of the impedance change rate can be 5%, and the threshold of the voltage source phase change can be 2 degrees. The power flow recalculation generally can include active power iterative calculation (such as ), reactive power iterative calculation ( ), and convergence judgment ( p.u.) and other processes. is the change amount of active power, is the admittance matrix of the power system, is the change in the phase angle of the node voltage, is the change in reactive power, and e is the base of the natural logarithm.

[0047] In this embodiment, after being transmitted back to PSCAD, a closed-loop verification and fault tolerance mechanism can also be executed so that the multiple verification and rollback strategies ensure the system reliability in extreme scenarios.

[0048] The verification rules are as follows: Dynamic layer verification: If the absolute value of the difference between the updated Thevenin equivalent voltage source and the voltage source in the previous cycle is greater than a specified threshold (such as 0.05 per unit (p.u.)), it is determined that the parameter is abnormal. In the case of parameter abnormality, the system will trigger the historical data rollback mechanism to restore to the previous state to ensure the stability of the system; Steady-state layer verification: If the BPA power flow iteration times are greater than 50 times and still do not converge, it is determined that the model is mismatched and switched to the full dynamic simulation mode.

[0049] The fault tolerance strategies are as follows: Data rollback: Keep the parameter history of the last 10 cycles and automatically roll back to the nearest valid state when abnormal; Model degradation: If the verification fails continuously for 3 times, close the parameter update function, fix the Thevenin parameters and give an alarm.

[0050] In an embodiment of this specification, suppressing the transient overvoltage of the power system within a time less than the first preset duration (such as 10 ms) includes: When detecting that the transient overvoltage peak value (which can be expressed as ) exceeds the first preset voltage threshold (which can be expressed as ) or the voltage change rate exceeds the preset change threshold (such as ), calculate the reactive power output according to the preset proportional gain, integral gain and reserved safety margin to quickly respond and suppress the transient overvoltage; the calculation process of the reactive power output is shown in the following formula (8): (8); Among them, is the reactive power output, is the proportional gain, is the integral gain, is the reserved safety margin, t represents time, is the reference voltage; When the steady-state voltage deviation exceeds the second preset voltage threshold (such as ), and when the duration exceeds the first preset duration threshold (e.g., 30 s), the step size is adjusted according to a preset ratio (e.g., ±1.25% (±6.25 kV for the 500 kV system)). If the number of adjustments reaches the preset number (e.g., 3 times) within a preset time period (e.g., 10 minutes), the blocking condition is activated (the action is paused and an alarm is issued).

[0051] Optimize the steady-state voltage of the power system within a time less than the second preset duration (e.g., 100 ms) in combination with wide-area coordinated control (generator excitation adjustment, load shedding), including: Calculate the reactive power sensitivity of each generator to the head-end voltage, select the two generators with the highest sensitivity, and adjust the excitation voltage command according to the voltage deviation and the preset proportional gain of the automatic voltage regulator; specifically, the excitation voltage command can be as shown in the following formula (9): (9); Wherein, is the new excitation voltage command, which controls the DC voltage output by the generator excitation system; is the current excitation voltage value, which reflects the real-time state of the generator excitation system; is the voltage deviation, usually the difference between the measured voltage and the reference voltage; is the proportional gain of the automatic voltage regulator, which determines the excitation response speed and sensitivity, generally taking 0.1 to 0.3 p.u. / kV.

[0052] When the voltage is lower than the third preset voltage threshold (e.g., 0.9 p.u.), the duration exceeds the second preset duration (e.g., 5 s), and all reactive power resources have been exhausted, load shedding is performed according to the priority and gradient.

[0053] In this embodiment, the second preset duration is greater than the first preset duration. The priority is generally set such that non-critical loads (such as commercial electricity) are prior to industrial loads. The gradient is generally set to cut 5% of the total load each time, with an interval of 10 s. By adopting the strategy of suppressing transient overvoltage and optimizing steady-state voltage within different preset durations, and by quickly responding to transient overvoltage and combining wide-area coordinated control to optimize steady-state voltage, the voltage stability and control accuracy of the power system can be effectively improved, thereby enhancing the reliability and security of the system. The above various thresholds can be set according to the actual situation and are not specifically limited here.

[0054] After that, the control effect can also be evaluated. For example, dynamic layer verification can be performed as follows: If the voltage after control does not enter the target range, secondary adjustment is triggered; Evaluation index: Transient overshoot rate . Wherein, is the peak value of the transient overvoltage, is the steady-state voltage value.

[0055] Steady-state layer verification can also be performed. After the power flow converges, check the node voltage over-limit situation. If there is an over-limit, reallocate the reactive power output.

[0056] In addition to evaluating the control effect, an adaptive PID coefficient can also be performed.

[0057] In some other embodiments of this specification, based on the dynamic-steady-state hybrid model, verify the control effect of the power system, and adaptively adjust the control strategy according to the actual situation of the power system, which may include building a simulation verification platform and hardware deployment. Among them, building the simulation verification platform includes: (1), Software tool integration: Dynamic simulation: PSCAD 4.6 + custom component library (synchronous machine, STATCOM, wind power model, etc.); Steady-state calculation: BPA 4.2 + Python interface (call bpa_api.dll for parameter injection); Coordinated control: MATLAB / Simulink to implement FPGA logic simulation; (2), Hardware-in-the-loop (HIL): Real-time simulator: RT-LAB OP4500 (step size 50μs), connected to the actual SVC controller (such as ABB PCS6000); Communication protocol: IEC 61850-9-2 LE (sampled values) and GOOSE (control instructions).

[0058] Hardware deployment may include: Control terminal installation: FPGA board: Xilinx Kintex-7 XC7K325T, deploy the impedance calculation logic; Communication module: Hirschmann MACH4002 switch (supporting IEEE 1588 PTP).

[0059] On-site wiring specifications: PMU voltage / current input: Use shielded twisted pair (cross-sectional area ≥2.5mm²), grounding resistance <1Ω; GOOSE outlet: Fiber optic interface (LC type), transmission delay <2ms.

[0060] The present invention will be introduced below through a specific example. An actual new energy collection area power grid is as Figure 2As shown in the figure. Initial state: All 7 wind farms are operating at full capacity. The active power flow of the double-circuit 500 kV DLS~CKS line is 3,042 MW. The voltage at the DLS substation, U1 = 520.3 kV, and the voltage at the CKS substation, U2 = 519.4 kV. At 0.2 s, one of the 500 kV DLS~CKS lines is taken out of service for maintenance, and a load shedding occurs on the CKS side of the second 500 kV DLS~CKS line.

[0061] Traditional electromagnetic transient modeling method: Based on the PSCAD software, the 500 kV BZ substation, 500 kV CKS substation, 500 kV DLS substation, 500 kV WC substation, and 500 kV HT substation are selected as equivalent points for Thevenin equivalent. The Bergeron model is used for the lines between the equivalent points, and the new energy power stations are all equivalent in the BZ substation.

[0062] If the traditional method is adopted, load shedding operations are carried out on the CKS side of the 500 kV DLS~CKS line in the PSCAD Thevenin equivalent model and the BPA power flow software respectively. After load shedding, the voltage at the end of the line exceeds the 550 kV specified by the dispatcher, and the voltage of the DLS bus at the head end of the line needs to be pre-controlled. As the power flow of the 500 kV DLS~CKS line decreases, the control voltages of the DLS bus at the head end of the line calculated in the PSCAD and BPA power flow software are shown in Table 1 below.

[0063] Table 1

[0064] It can be seen from the above calculation results that in the PSCAD calculation, the heavier the power flow of the line, the lower the control voltage of the head-end bus after load shedding at the end. In the BPA power flow calculation, the heavier the power flow of the line, the higher the control voltage of the head-end bus after load shedding at the end, and there is a contradiction between the two.

[0065] Using the method of the present invention, key nodes are first selected for detailed modeling in PSCAD, mainly including new energy power stations involved in the grid. A detailed doubly-fed wind turbine model needs to be used, and the STATCOM / SVC configured in the new energy power station also needs to be detailedly modeled in PSCAD.

[0066] Then import the BPA initial power flow results (.dat file) and configure the PMU virtual sampling points (the head-end DLS bus and the new energy grid-connected point BZ substation). At t = 0.2 s, trigger load shedding, and the action duration is t = 0.1 s. Export from PSCAD every 5 ms ( , ), update the BPA card through a Python script. If the BPA converges, read the new voltage source and transmit it back to PSCAD. By using the method of the present invention, as the power flow of the 500 kV DLS~CKS line decreases, the control voltage of the DLS bus at the line head calculated in PSCAD is shown in Table 2 below, and the above problems can be avoided.

[0067] Table 2

[0068] Based on the same general inventive concept, the present invention also protects a power system voltage control device based on dynamic-steady state collaborative correction, as Figure 3 shown Figure 3 is a schematic structural diagram of the power system voltage control device based on dynamic-steady state collaborative correction provided by an embodiment of the present invention. The power system voltage control device based on dynamic-steady state collaborative correction provided by the present invention will be described below. The power system voltage control device based on dynamic-steady state collaborative correction described below can be mutually corresponded and referred to the power system voltage control method based on dynamic-steady state collaborative correction described above.

[0069] The power system voltage control device based on dynamic-steady state collaborative correction includes a dynamic-steady state module 301, a parameter update module 302, a voltage hierarchical control module 303, and a verification module 304.

[0070] The dynamic-steady state module 301 is used to establish an electromagnetic transient model for a preset voltage node in the power system electromagnetic transient simulation software PSCAD, simplify the power grid whose electrical distance to the target area exceeds the preset distance into a dynamic Thevenin equivalent model, and initialize the power flow calculation in BPA, set the generator as a PV node, the load as a PQ node, and configure the parameters of reactive power compensation equipment to obtain a dynamic-steady state hybrid model; The parameter update module 302 is used to update the dynamic Thevenin equivalent parameters of the power system in real time according to the data of the power system phasor measurement unit and synchronize them to BPA; The voltage hierarchical control module 303 is used to suppress the transient overvoltage of the power system within a time less than the first preset duration based on the dynamic-steady state hybrid model, and optimize the steady-state voltage of the power system within a time less than the second preset duration in combination with wide-area coordinated control; The verification module 304 is used to verify the control effect of the power system based on the dynamic-steady state hybrid model, and adaptively adjust the control strategy according to the actual situation of the power system.

[0071] Figure 4 is a schematic structural diagram of the electronic device provided by an embodiment of the present invention.

[0072] As Figure 4As shown, the electronic device may include: a processor 410, a communications interface 420, a memory 430, and a communication bus 440. Among them, the processor 410, the communications interface 420, and the memory 430 communicate with each other through the communication bus 440. The processor 410 may call the logical instructions in the memory 430 to execute the power system voltage control method based on dynamic steady-state collaborative correction.

[0073] In addition, when the logical instructions in the above-mentioned memory 430 are implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or a part of this technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in various embodiments of the present invention. The foregoing storage medium includes: various media such as USB flash drives, mobile hard disks, read-only memories (ROMs), random access memories (RAMs), magnetic disks, or optical discs that can store program codes.

[0074] On the other hand, the present invention also provides a computer program product. The computer program product includes a computer program that can be stored on a non-transitory computer-readable storage medium. When the computer program is executed by a processor, the computer can execute the power system voltage control method based on dynamic steady-state collaborative correction provided by the above-mentioned various methods.

[0075] On yet another aspect, the present invention also provides a non-transitory computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, it is implemented to execute the power system voltage control method based on dynamic steady-state collaborative correction provided by the above-mentioned various methods.

[0076] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place, or may be distributed to multiple network units. Some or all of the modules can be selected according to actual needs to achieve the purpose of the solution of this embodiment. A person of ordinary skill in the art can understand and implement it without creative labor.

[0077] Through the description of the above embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus a necessary general hardware platform, and of course, it can also be implemented by hardware. Based on such an understanding, the essence of the above technical solution, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to enable a computer device (which can be a personal computer, server, or network device, etc.) to execute the methods described in each embodiment or some parts of the embodiments.

[0078] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A power system voltage control method based on dynamic steady-state collaborative correction, characterized in that, Including: Establish an electromagnetic transient model for the preset voltage nodes in the power system electromagnetic transient simulation software PSCAD, simplify the power grid whose electrical distance to the target area exceeds the preset distance into a dynamic Thevenin equivalent model, initialize the power flow calculation in BPA, set the generators as PV nodes, the loads as PQ nodes, and configure the parameters of the reactive power compensation equipment to obtain a dynamic-steady state hybrid model; Update the dynamic Thevenin equivalent parameters of the power system in real time according to the phasor measurement unit data of the power system and synchronize them to BPA; Based on the dynamic-steady state hybrid model, suppress the transient overvoltage of the power system within a time less than the first preset duration, and optimize the steady-state voltage of the power system within a time less than the second preset duration in combination with wide-area coordinated control; Based on the dynamic-steady state hybrid model, verify the control effect of the power system and adaptively adjust the control strategy according to the actual situation of the power system.

2. The method for controlling the voltage of a power system based on dynamic steady-state collaborative correction according to claim 1, wherein, Establish an electromagnetic transient model for the preset voltage nodes in the power system electromagnetic transient simulation software PSCAD, simplify the power grid whose electrical distance to the target area exceeds the preset distance into a dynamic Thevenin equivalent model, including: Calculate the sensitivity of the voltage of each voltage node in the power system to the power change, and analyze the topological structure of the power system. Based on the sensitivity and topological structure, obtain the preset voltage nodes; Configure the model parameters of the electromagnetic transient model based on the parameter file of BPA to make the model parameters consistent with the BPA steady-state data; For the power grid whose electrical distance to the target area exceeds the preset distance, use the short-circuit capacity method or the N-1 fault scanning method to calculate the equivalent impedance and the equivalent voltage source to obtain the dynamic Thevenin equivalent model.

3. The method for voltage control of a power system based on dynamic steady-state collaborative correction according to claim 2, wherein Calculate the sensitivity of the voltage of each voltage node in the power system to the power change, and analyze the topological structure of the power system. Based on the sensitivity and topological structure, obtain the preset voltage nodes, including: Calculate the ratio of the voltage of each voltage node in the power system to the corresponding power as the sensitivity; Sort the sensitivities from small to large; According to the sorting, select the voltage nodes corresponding to the preset number of sensitivities, and the voltage nodes located in the backbone network, new energy collection points and load centers in the topological structure as the preset voltage nodes.

4. The method for controlling the voltage of a power system based on dynamic steady-state collaborative correction according to claim 2, characterized in that, Use the short-circuit capacity method to calculate the equivalent impedance, including: Based on the power flow calculation results, obtain the short-circuit capacity; Calculate the ratio of the square of the grid-connected point voltage to the short-circuit capacity as the equivalent impedance; Use the N-1 fault scanning method to calculate the equivalent impedance, including: Simulate the three-phase short-circuit fault of the preset node in PSCAD to obtain the fault current; Calculate the ratio of the voltage before the fault to the fault current as the equivalent impedance.

5. The voltage control method for a power system based on dynamic steady-state collaborative correction according to claim 1, characterized in that Update the dynamic Thevenin equivalent parameters of the power system in real time according to the phasor measurement unit data of the power system and synchronize them to BPA, including: Sample the preset nodes in the power system to obtain the sampled data of voltage and current; Preprocess the sampled data; Based on the preprocessed sampled data, use the sensitivity method to update the dynamic Thevenin equivalent parameters in real time; Synchronize the updated dynamic Thevenin equivalent parameters to BPA through the data interface.

6. The voltage control method for a power system based on dynamic steady-state collaborative correction according to claim 5, wherein Use the sensitivity method to update the dynamic Thevenin equivalent parameters in real time, including: Compare the voltage change and current change between the current cycle and the previous cycle using the sensitivity method; Determine the ratio of the voltage change to the current change as the impedance change; Based on the impedance change, the smoothing coefficient of the impedance change, and the equivalent impedance of the previous cycle, obtain the updated equivalent impedance; Based on the updated equivalent impedance, the current value, and the voltage value of the current cycle, obtain the updated voltage value.

7. The method for voltage control of a power system based on dynamic steady-state collaborative correction according to claim 6, characterized in that The impedance change is expressed by the following formula: ； Among them, is the impedance change amount, is the voltage value of the previous cycle, is the current value of the previous cycle, k represents the cycle, is the voltage value of the current cycle, is the current value of the current cycle; The updated equivalent impedance is expressed by the following formula: ； is the updated equivalent impedance, is the equivalent impedance of the previous cycle, is the smoothing coefficient.

8. The voltage control method for a power system based on dynamic steady-state collaborative correction according to claim 5, characterized in that, Synchronize the updated dynamic Thevenin equivalent parameters to BPA through the data interface, including: Call the interface of BPA through a Python script to synchronize the updated dynamic Thevenin equivalent parameters to BPA; If the impedance change rate and the voltage source phase change after the BPA update reach the set threshold, perform a power flow recalculation; Read the generator voltage setting value and reactive power compensation instruction output by BPA and send them back to PSCAD.

9. The method for controlling the voltage of a power system based on dynamic steady-state collaborative correction according to claim 1, wherein Suppress the power system transient overvoltage within a time less than the first preset duration, including: When it is detected that the transient overvoltage peak exceeds the first preset voltage threshold or the voltage change rate exceeds the preset change threshold, calculate the reactive power output according to the preset proportional gain, integral gain, and reserved safety margin to quickly respond and suppress the transient overvoltage; When the steady-state voltage deviation exceeds the second preset voltage threshold and the duration exceeds the first preset duration threshold, adjust the step size according to the preset ratio. If the number of adjustments reaches the preset number within the preset time period, start the locking condition; Optimize the steady-state voltage of the power system within a time less than the second preset duration in combination with wide-area coordinated control, including: Calculate the reactive power sensitivity of each generator to the voltage at the head end, select the two generators with the highest sensitivity, and adjust the excitation voltage instruction according to the voltage deviation and the preset proportional gain of the automatic voltage regulator; When the voltage is lower than the third preset voltage threshold, the duration exceeds the second preset duration, and all reactive power resources have been exhausted, shed loads according to the priority and gradient.

10. A power system voltage control device based on dynamic steady-state collaborative correction, characterized in that, Including: A dynamic steady-state module for establishing an electromagnetic transient model for preset voltage nodes in the power system electromagnetic transient simulation software PSCAD, simplifying the power grid whose electrical distance to the target area exceeds the preset distance into a dynamic Thevenin equivalent model, initializing the power flow calculation in BPA, setting the generator as a PV node, the load as a PQ node, and configuring the parameters of reactive power compensation equipment to obtain a dynamic-steady hybrid model; A parameter update module for updating the dynamic Thevenin equivalent parameters of the power system in real time according to the data of the power system phasor measurement unit and synchronizing them to BPA; A voltage hierarchical control module for suppressing the power system transient overvoltage within a time less than the first preset duration based on the dynamic-steady hybrid model, and optimizing the steady-state voltage of the power system within a time less than the second preset duration in combination with wide-area coordinated control; A verification module for verifying the control effect of the power system based on the dynamic-steady hybrid model and adaptively adjusting the control strategy according to the actual situation of the power system.

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