A power grid stability control system and method coordinating multiple resources

Abstract

The application provides a power grid stability control system and method cooperating with multiple resources, which covers three control modules of frequency, power angle and voltage. The frequency module is responsible for power deviation control of water, fire and wind and light units. The power angle module responds to power angle swing in stages, including strong excitation of water and fire units, low penetration of wind and light units, and adjustment of unit state with voltage recovery. The voltage module evaluates the reactive power demand after the short circuit of the power grid partition, and according to the adequacy of the reactive power source, guides the wind and light units to increase or decrease the reactive current, and the water and fire units to adjust the strong excitation reference value. The system takes control measures according to the actual state of the power grid, and stabilizes the frequency, power angle and voltage in all directions, significantly improves the stability and safety of the power grid.

Description

Technical Field

[0001] This application belongs to the field of multi-resource power grid control, and in particular relates to a coordinated multi-resource power grid stability control system and method. Background Technology

[0002] With the development of modern power systems, the stability and security of power grids have become crucial issues in the power industry. Traditional power grid stability control systems mainly rely on the control of a single resource, such as controlling only hydroelectric and thermal power units or only wind and solar power units. However, with the large-scale integration of new energy sources and the increasing complexity of power grid structures, single-resource control methods are no longer sufficient to meet the stability control requirements of modern power grids. Summary of the Invention

[0003] The purpose of this application is to overcome the deficiencies in the prior art and provide a collaborative multi-resource power grid stability control system and method.

[0004] This application provides a collaborative multi-resource power grid stability control system, including: a frequency control module, a power angle control module, and a voltage control module;

[0005] The frequency control module is used for primary and secondary control of power deviation of hydro-thermal units and wind-solar units.

[0006] The power angle control module divides the power angle swing process into three phases: voltage drop without recovery, voltage recovery but power angle difference not pulled back, and power angle difference pull-back. During the voltage drop without recovery phase, the hydro-thermal turbines enter the forced excitation mode, and the wind and solar turbines adopt a low-voltage strategy. During the voltage recovery but power angle difference not pulled back, the hydro-thermal turbines reduce the forced excitation reference value, and the wind and solar turbines reduce reactive current and restore active power. During the power angle difference pull-back phase, the hydro-thermal turbines exit the forced excitation mode, and the wind and solar turbines restore active power and reactive power returns to its initial value.

[0007] The voltage control module assesses the maximum reactive load demand after a short-circuit fault according to the power grid zone, and determines whether the dynamic reactive power sources deployed in the power grid zone can meet the maximum reactive load demand. For power grid zones with insufficient reactive power sources, the wind and solar turbines increase the reactive current during the low-voltage period and maintain the reactive current after the low-voltage period until the grid voltage recovers, while the hydro-thermal turbines maintain strong excitation until the grid voltage recovers. For power grid zones with sufficient reactive power sources, the wind and solar turbines increase the reactive current during the low-voltage period and reduce the output reactive current after the low-voltage period, while the hydro-thermal turbines maintain a low strong excitation reference value.

[0008] Optionally, the hydro-thermal unit enters the strong excitation mode, including: reaching the excitation peak value according to a preset time.

[0009] Optionally, it also includes: a monitoring module for real-time monitoring of grid frequency, power angle and voltage status, as well as operating parameters of each unit.

[0010] Optionally, the frequency control module is used to perform primary and secondary control of power deviation for hydro-thermal units. When performing primary and secondary control of power deviation for wind and solar units, the hydro-thermal units and the wind and solar units are equivalent to single-unit systems.

[0011] Optionally, it also includes: a human-machine interface for displaying the real-time operating status of the power grid, the execution status of stability control measures, and fault alarm information.

[0012] This application also provides a collaborative multi-resource power grid stability control method, including:

[0013] Frequency control steps: primary and secondary control of power deviation for hydro-thermal units, and primary and secondary control of power deviation for wind and solar units;

[0014] Power angle control steps: The power angle swing process of the power grid is divided into three periods: voltage drop before recovery, voltage recovery but power angle difference not pulled back, and power angle difference pull-back. During the voltage drop before recovery period, the hydro-thermal units are put into strong excitation mode until the excitation peak value is reached according to the preset time, while the wind and solar units adopt low-voltage charging strategy. During the voltage recovery but power angle difference not pulled back, the strong excitation reference value of the hydro-thermal units is reduced, and the reactive current of the wind and solar units is reduced to restore active power. During the power angle difference pull-back period, the hydro-thermal units are taken out of strong excitation mode, while the active power of the wind and solar units is restored and the reactive power is returned to the initial value.

[0015] Voltage control steps: Assess the maximum reactive load demand after a short-circuit fault according to the power grid zone assessment, and determine whether the dynamic reactive power sources deployed in each power grid zone meet the maximum reactive load demand; for power grid zones with insufficient reactive power sources, increase the reactive current during the low-voltage run-through of wind and solar turbines, and maintain the reactive current until the grid voltage recovers after the low-voltage run-through, while keeping the hydro-thermal turbines in a strongly excited state until the grid voltage recovers; for power grid zones with sufficient reactive power sources, increase the reactive current during the low-voltage run-through of wind and solar turbines, and reduce the output reactive current after the low-voltage run-through, while reducing the strongly excited reference value of the hydro-thermal turbines.

[0016] Optionally, the hydro-thermal unit enters the strong excitation mode, including: reaching the excitation peak value according to a preset time.

[0017] Optionally, it also includes: real-time monitoring of grid frequency, power angle and voltage status, as well as operating parameters of each unit.

[0018] Optionally, the frequency control module is used to perform primary and secondary control of power deviation for hydro-thermal units. When performing primary and secondary control of power deviation for wind and solar units, the hydro-thermal units and the wind and solar units are equivalent to single-unit systems.

[0019] Optionally, it also includes: displaying the real-time operating status of the power grid, the implementation status of stability control measures, and fault alarm information through a human-machine interface.

[0020] The beneficial effects of this application are:

[0021] This application provides a collaborative multi-resource power grid stability control system, including: a frequency control module, a power angle control module, and a voltage control module; the frequency control module is used for primary and secondary control of power deviation of hydro-thermal units and wind-solar units; the power angle control module divides the power angle swing process into a voltage dip without recovery period, a voltage recovery but power angle difference not pulled back period, and a power angle difference pull-back period; during the voltage dip without recovery period, the hydro-thermal units enter a forced excitation mode, and the wind-solar units adopt a low-voltage power-off strategy; during the voltage recovery but power angle difference not pulled back period, the hydro-thermal units reduce the forced excitation reference value, and the wind-solar units reduce reactive current to restore active power; during the power angle... During the pullback period, the hydro-thermal turbines exit the forced excitation mode, and the wind and solar turbines restore active power while reactive power returns to its initial value. The voltage control module assesses the maximum reactive load demand after a short-circuit fault according to the grid zone, determining whether the dynamic reactive power sources deployed in the grid zone can meet the maximum reactive load demand. For grid zones with insufficient reactive power sources, the wind and solar turbines increase reactive current during low-voltage ride-through and maintain this reactive current until the grid voltage recovers after low-voltage ride-through, while the hydro-thermal turbines maintain forced excitation until the grid voltage recovers. For grid zones with sufficient reactive power sources, the wind and solar turbines increase reactive current during low-voltage ride-through and reduce output reactive current after low-voltage ride-through, while the hydro-thermal turbines maintain a low forced excitation reference value. This application achieves comprehensive stable control of grid frequency, power angle, and voltage by taking corresponding control measures for the actual operating state of a multi-resource grid, thereby improving the stability and security of the grid. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the collaborative multi-resource power grid stability control system in this application;

[0023] Figure 2 This is a schematic diagram of the multi-resource power grid frequency stabilization control circuit in this application;

[0024] Figure 3 This is a schematic diagram illustrating the principle of the equal area rule in this application;

[0025] Figure 4This is a schematic diagram of power grid power angle stability control in this application;

[0026] Figure 5 This is a schematic diagram of the PV curve of the new energy unit in this application;

[0027] Figure 6 This is a schematic diagram of the power grid voltage stability control in this application. Detailed Implementation

[0028] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it will be understood that various forms of implementation of the present disclosure are possible and should not be limited to the embodiments set forth herein. Rather, the embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0029] Please refer to Figure 1 As shown, a collaborative multi-resource power grid stability control system includes: a frequency control module, a power angle control module, and a voltage control module.

[0030] The frequency control module is used for primary and secondary control of power deviation of hydro-thermal units, and primary and secondary control of power deviation of wind and solar units.

[0031] When studying frequency stability, the time scale is relatively large, governor operation must be considered, and the electromechanical oscillation process between units has ended, with the units in the system oscillating in sync. Therefore, when studying frequency stability, power exchange between units is ignored, and the system is studied as a single-unit system.

[0032] This application uses the Center of Inertia (COI) model to represent system i as a single-machine system, as expressed by the following expression:

[0033]

[0034] Where, Δδ i The equivalent work angle deviation of the center of inertia, Δω i For the equivalent rotational speed deviation of the center of inertia, H i For the equivalent inertia of the center of inertia, ΔP m,i For the equivalent mechanical power deviation at the center of inertia, ΔP e,i For the equivalent electromagnetic power deviation at the center of inertia, D i is the equivalent damping coefficient of the center of inertia.

[0035] Please refer to Figure 2 As shown, grid frequency stability control includes primary and secondary control of hydroelectric and thermal power units, and primary and secondary control of wind and solar power units.

[0036] The effect of primary water and fire control can be expressed as:

[0037]

[0038] Where, ΔP 水火 For power deviation, Δω i For speed deviation, M ki (s) is the transfer function of the prime mover and speed control system of the k-th hydro-thermal unit, R ki This represents the corresponding feedback coefficient.

[0039] The secondary control of water and fire is achieved by a frequency modulator.

[0040] like Figure 2 As shown, B i K is the frequency deviation coefficient. i (s) is the transfer function of the frequency modulator, α ki Let be the adjustment coefficient of the k-th hydroelectric generator unit.

[0041] The primary control effect of wind and solar power can be summarized into two types: inertial support and damping support, represented as follows:

[0042]

[0043] Where, ΔP 风光 For power deviation, Δω i For speed deviation, The supporting inertia provided for wind and solar turbine units. Support damping provided for wind and solar turbine units. This is the time constant for the operation of the wind and solar turbine units.

[0044] The secondary control of wind and solar power is determined by comprehensively considering the characteristics of the system.

[0045] like Figure 2 As shown, γ i This is the adjustment coefficient for wind and solar power units.

[0046] Furthermore, this application also considers the impact of other systems.

[0047] Suppose that system i and system j are connected by a tie line, the power increment on the tie line can be expressed as:

[0048]

[0049] Among them, T ij Let Δf be the coefficient of the corresponding connection line ij. i Let Δf be the frequency of system i. j Let j be the frequency of system j.

[0050] For hydroelectric generating units, the mechanical power is adjusted by the speed control system to achieve the purpose of primary frequency regulation.

[0051] Due to the inherent characteristics of the prime mover, the primary regulation characteristics of hydroelectric generating units are difficult to alter significantly by changing their control strategies and parameters; their behavior remains relatively fixed under electromagnetic power disturbances. The secondary control of hydroelectric generating units is accomplished by a frequency modulator, which proportionally distributes unbalanced power among different units, thereby achieving constant frequency control.

[0052] For wind and solar turbines, their behavior is adjusted according to the needs of the operators.

[0053] Specifically, wind and solar turbines quickly release their reserve capacity to achieve an effect similar to emergency power support. However, due to the difficulty in real-time information collection and considering the unbalanced power distribution between different types of turbines, the primary frequency regulation strategy for wind and solar turbines is virtual synchronization control or droop control.

[0054] Droop control can be viewed as a special case where the inertia is zero in the virtual synchronous control strategy.

[0055] The unbalanced power undertaken by wind and solar turbines in secondary regulation is determined by taking into account the operating characteristics and regulation capabilities of various types of turbines, including hydropower, thermal power, wind power, and solar power, and through optimization methods.

[0056] It should be noted that the inertia, damping, and prime mover parameters of hydroelectric and thermal power units are inherent physical characteristics that cannot be changed, while the inertia and damping parameters of wind and solar power units can be modified manually. Therefore, the various control parameters of wind and solar power units are not static during frequency stabilization control; they are modified according to system operation and actual needs, and may even be adaptively adjusted during dynamic processes.

[0057] The power angle control module divides the power angle swing process into three phases: voltage drop without recovery, voltage recovery but power angle difference not pulled back, and power angle difference pull-back. During the voltage drop without recovery phase, the hydro-thermal turbines enter the forced excitation mode, and the wind and solar turbines adopt a low-voltage strategy. During the voltage recovery but power angle difference not pulled back, the hydro-thermal turbines reduce the forced excitation reference value, and the wind and solar turbines reduce reactive current and restore active power. During the power angle difference pull-back phase, the hydro-thermal turbines exit the forced excitation mode, and the wind and solar turbines restore active power while reactive power returns to its initial value.

[0058] The low-voltage drop strategy refers to the proactive adjustment of inverter control modes by wind, solar, or thermal power units to maintain grid connection and provide dynamic reactive power support when a grid fault causes a short-term, significant voltage drop, rather than passively disconnecting from the grid. The aim is to prevent large-scale disconnection of renewable energy units from exacerbating the risk of grid collapse, while simultaneously assisting in system voltage recovery and power angle stabilization.

[0059] The power angle control is analyzed using the equal area rule.

[0060] A concrete example is an investigation into a three-phase short circuit on bus sys, where the voltage on bus sys is zero during the fault. From this, the generator's output power P during the fault can be deduced. gen =0; while the mechanical power of the generator is equal to the generator's original output power P. gen0 .

[0061] During the fault, the generator output power P gen =0, the accelerating power of the generator is equal to its own input mechanical power P. gen0 .

[0062] Therefore, according to the equation of motion of the generator:

[0063]

[0064] Where M is the inertial time constant of the generator set; t is time; P m P is the mechanical power input to the generator. m =P gen0 ;P e P represents the electromagnetic power output by the generator, which is zero during a fault. D The damping power of the generator is not considered in this application, so it is set to zero.

[0065] The fault clearing time t is derived from the boundary conditions of the generator's equation of motion at the time of the fault. clear generator power angle δ clear The expression is:

[0066]

[0067] like Figure 3 As shown, under the above conditions, the horizontal axis represents the generator power angle δ. gen The vertical axis is P gen / P gen0 ; and the time t for fault clearing clear The corresponding fault clearing angle is δ clear δ h (δ h1 δ h2 ) is the generator output power P after the fault is cleared. gen With generator mechanical power P m =P gen0 The intersection point.

[0068] According to the law of equal area, and the critical time t for fault clearance clear =t cr The corresponding critical fault clearing angle δ clear =δ cr The condition that must be met is that the "acceleration area" equals the "deceleration area", that is:

[0069]

[0070] As the penetration rate of asynchronous power supplies increases, the critical clearing angle and critical clearing time will be affected, and the power angle stability of the system will also be affected.

[0071] Based on the dynamic process after the disturbance occurs, the power angle swing process is divided into three stages: the period when the voltage drops and does not recover, the period when the voltage recovers but the power angle difference does not return to normal, and the period when the power angle difference returns to normal.

[0072] Please refer to Figure 4 As shown, the measures that can be taken for different types of generating units, such as hydropower, thermal power, wind power, and solar power, vary at different stages.

[0073] During voltage dips and the recovery phase, the excitation system of hydro-thermal units enters a forced excitation mode, reaching the excitation peak value within a specified time to rapidly increase reactive power output in an attempt to restore the terminal voltage. Forced excitation effectively increases the terminal voltage of hydro-thermal units, thereby dissipating electromagnetic power and reducing the rate of widening power angle differences between units. Wind and solar turbines, however, trigger low-voltage ride-through control strategies during voltage dips. During low-voltage ride-through, the behavior of wind and solar turbines is not fixed but manually configured. Therefore, operators improve system power angle stability by manually configuring the low-voltage ride-through strategies for wind and solar turbines.

[0074] Generally, there are two control routes for wind and solar turbines during low-voltage periods: one is active current priority, and the other is reactive current priority. Since power angle stability is caused by long lines and heavy loads, reducing the active current of wind and solar turbines during low-voltage periods effectively reduces the active load pressure on the cross-section, while increasing the reactive current of wind and solar turbines during low-voltage periods effectively improves the system voltage level, helping the power angle of hydro-thermal units to recover and stabilize.

[0075] If the hydro-thermal unit continues to operate in forced excitation mode during the period when the voltage recovery power angle difference has not been pulled back, it will lead to overvoltage at the generator terminal.

[0076] Therefore, even if the power angle difference in hydroelectric and thermal power units does not recover, the forced excitation reference value is still adjusted to avoid overvoltage at the turbine terminals. For wind and solar power units, after voltage recovery, their active power returns to normal; however, rapid recovery of active power increases the power flow load on the turbine sections, which is detrimental to system power angle stability. If the active power of wind and solar power units does not recover for an extended period, it will harm the system's frequency stability. Therefore, during the phase where voltage recovers but the power angle difference will return to normal, wind and solar power units slow down the active power recovery and lower the target value of active power. The reactive current of wind and solar power units also decreases; by adjusting the reactive current output, overvoltage at the turbine terminals is avoided.

[0077] After the power angle difference is pulled back, the hydro-thermal units exit the forced excitation mode and resume normal terminal voltage control. At this point, the system's power angle stability is sufficient and is no longer the main factor limiting the cross-sectional power transmission capacity; the wind and solar units resume their own active power. Furthermore, to avoid adverse effects on system frequency stability, the wind and solar units resume their own active power during this stage, while the reactive power returns to its initial value.

[0078] The voltage control module assesses the maximum reactive load demand after a short-circuit fault according to the power grid zone, and determines whether the dynamic reactive power sources deployed in the power grid zone can meet the maximum reactive load demand. For power grid zones with insufficient reactive power sources, the wind and solar turbines increase the reactive current during the low-voltage period and maintain the reactive current after the low-voltage period until the grid voltage recovers, while the hydro-thermal turbines maintain strong excitation until the grid voltage recovers. For power grid zones with sufficient reactive power sources, the wind and solar turbines increase the reactive current during the low-voltage period and reduce the output reactive current after the low-voltage period, while the hydro-thermal turbines maintain a low strong excitation reference value.

[0079] The voltage instability mechanism of a generator-dominated traditional power system is explained using the classic PV curve.

[0080] In the analysis of PV curves, the synchronous machine is treated as a constant voltage source, while the operating mode of new energy units switches as the port bus voltage decreases. Therefore, the existing PV curve analysis results are not applicable to new energy units.

[0081] In this application, when the voltage at the outlet of the new energy unit remains constant, the load power is expressed as a function of system parameters and node voltage:

[0082]

[0083] Among them, P D and Q D These represent the magnitudes of the active and reactive power of the load, respectively. Represents the voltage vector of the load node. This represents the conjugate of the RES output current.

[0084] In the previous formula, ignoring the resistance in the circuit, we get:

[0085]

[0086] Eliminate the variable θ in this formula r get:

[0087]

[0088] Solving this equation yields two solutions for the load node voltage:

[0089]

[0090] The magnitude of the load node voltage in the above formula is obtained under the assumption that the terminal voltage of the new energy unit remains constant.

[0091] If the new energy unit switches to constant current control mode, the output current amplitude of the new energy unit will remain constant, and the load bus voltage will be:

[0092]

[0093] Among them, I lim This is the maximum current limit for new energy generating units.

[0094] like Figure 5 As shown, assuming the power factor of the load is fixed, the voltage amplitude at the load is proportional to the apparent power of the load, which is a straight line passing through zero in the PV diagram.

[0095] In power grids with abundant wind, solar, hydro, and thermal power resources, the coexistence of low and overvoltage is highly likely due to the complex reactive power response characteristics and coupling mechanisms between different types of generating units. Therefore, before implementing voltage stabilization control, it is essential to first determine whether the target bus or area is experiencing low or overvoltage issues.

[0096] The grid voltage stability control in this application includes reactive power margin assessment and discrimination, low voltage control architecture, and overvoltage control architecture.

[0097] The reactive power adequacy assessment and judgment section determines whether the reactive power sources in each area are sufficient when facing power grid faults and dynamic reactive loads.

[0098] If a region has sufficient reactive power, it is prone to overvoltage problems during the recovery process when facing a grid fault. Conversely, if a region has insufficient reactive power, it will experience low voltage problems when facing a grid fault.

[0099] like Figure 6 As shown, different multi-resource control strategies for wind, solar, hydro, and thermal power are adopted to address the problems of low voltage and overvoltage.

[0100] For the assessment and identification of different areas, the maximum demand for reactive power after a short-circuit fault is assessed according to the power grid zoning.

[0101] For assessing the maximum reactive power demand, it is approximated that the reactive power demand of dynamic loads increases at a maximum rate during grid faults, thus calculating the maximum reactive power increment of all loads when a severe grid fault occurs in the area. Based on this, it is determined whether the dynamic reactive power sources deployed in the area can meet the dynamic reactive power load demand under severe fault conditions. If the dynamic reactive power sources are sufficient, the area is prone to overvoltage problems in the initial recovery phase after the fault is cleared. If the dynamic reactive power sources are insufficient, the area is prone to low voltage or even voltage collapse problems after the fault is cleared.

[0102] If a certain area faces a low voltage problem, then the low voltage control system architecture will be activated.

[0103] During a fault, the grid voltage level is low, and wind and solar turbines will initiate a low-voltage ride-through strategy. To accelerate the recovery of grid voltage, wind and solar turbines maximize reactive current during the low-voltage ride-through and maintain this reactive current until the grid voltage level in their area recovers. Meanwhile, hydro-thermal turbines, under the action of their excitation systems, will enter a strong excitation mode during a grid fault and maintain this strong excitation mode after the fault is cleared until the voltage in their area recovers.

[0104] If a certain area faces an overvoltage problem, the overvoltage control system architecture will be activated.

[0105] During a fault, the grid voltage level remains low, and wind and solar turbines activate their low-voltage recovery strategy. Similarly, to accelerate grid voltage recovery, wind and solar turbines maximize reactive current during low-voltage recovery. However, as the voltage in their respective areas increases, the output reactive current of the wind and solar turbines decreases to prevent overvoltage after the fault. Hydro-thermal turbines will still enter forced excitation mode during a fault, but the forced excitation reference value gradually decreases as the voltage level in their respective areas increases to prevent overvoltage after the fault.

[0106] This application also provides a method for coordinated multi-resource power grid stability control, characterized by comprising:

[0107] Frequency control steps: primary and secondary control of power deviation for hydro-thermal units, and primary and secondary control of power deviation for wind and solar units;

[0108] Power angle control steps: The power angle swing process of the power grid is divided into three periods: voltage drop before recovery, voltage recovery but power angle difference not pulled back, and power angle difference pull-back. During the voltage drop before recovery period, the hydro-thermal units are put into strong excitation mode until the excitation peak value is reached according to the preset time, while the wind and solar units adopt low-voltage charging strategy. During the voltage recovery but power angle difference not pulled back, the strong excitation reference value of the hydro-thermal units is reduced, and the reactive current of the wind and solar units is reduced to restore active power. During the power angle difference pull-back period, the hydro-thermal units are taken out of strong excitation mode, while the active power of the wind and solar units is restored and the reactive power is returned to the initial value.

[0109] Voltage control steps: Assess the maximum reactive load demand after a short-circuit fault according to the power grid zone assessment, and determine whether the dynamic reactive power sources deployed in each power grid zone meet the maximum reactive load demand; for power grid zones with insufficient reactive power sources, increase the reactive current during the low-voltage run-through of wind and solar turbines, and maintain the reactive current until the grid voltage recovers after the low-voltage run-through, while keeping the hydro-thermal turbines in a strongly excited state until the grid voltage recovers; for power grid zones with sufficient reactive power sources, increase the reactive current during the low-voltage run-through of wind and solar turbines, and reduce the output reactive current after the low-voltage run-through, while reducing the strongly excited reference value of the hydro-thermal turbines.

[0110] The hydro-thermal unit entering the strong excitation mode includes: reaching the excitation peak value according to a preset time.

[0111] Furthermore, it monitors the grid frequency, power angle, and voltage status in real time, as well as the operating parameters of each generating unit.

[0112] Furthermore, the frequency control module is used for primary and secondary control of power deviation of hydro-thermal units. When performing primary and secondary control of power deviation of wind and solar units, the hydro-thermal units and the wind and solar units are equivalent to single-unit systems.

[0113] Furthermore, it also includes: displaying the real-time operating status of the power grid, the implementation status of stability control measures, and fault alarm information through a human-machine interface.

[0114] The above description of the embodiments is provided to enable those skilled in the art to understand and apply the present invention. It will be apparent to those skilled in the art that various modifications can be made to the above embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made to the present invention by those skilled in the art based on the disclosure thereof should be within the scope of protection of the present invention.

Claims

1. A collaborative multi-resource power grid stability control system, characterized in that, include: Frequency control module, power angle control module, and voltage control module; The frequency control module is used for primary and secondary control of power deviation of hydro-thermal units and wind-solar units. The power angle control module divides the power angle swing process into three phases: voltage drop without recovery, voltage recovery but power angle difference not pulled back, and power angle difference pull-back. During the voltage drop without recovery phase, the hydro-thermal turbines enter the forced excitation mode, and the wind and solar turbines adopt a low-voltage strategy. During the voltage recovery but power angle difference not pulled back, the hydro-thermal turbines reduce the forced excitation reference value, and the wind and solar turbines reduce reactive current and restore active power. During the power angle difference pull-back phase, the hydro-thermal turbines exit the forced excitation mode, and the wind and solar turbines restore active power and reactive power returns to its initial value. The voltage control module assesses the maximum reactive load demand after a short-circuit fault according to the power grid zone, and determines whether the dynamic reactive power sources deployed in the power grid zone can meet the maximum reactive load demand. For the power grid zone with insufficient reactive power sources, the wind and solar turbines increase the reactive current during the low-voltage period and maintain the reactive current after the low-voltage period until the grid voltage recovers, while the hydro-thermal turbines maintain strong excitation until the grid voltage recovers. For the power grid zone with sufficient reactive power sources, the wind and solar turbines increase the reactive current during the low-voltage period and reduce the output reactive current after the low-voltage period, while the hydro-thermal turbines reduce the strong excitation reference value.

2. The collaborative multi-resource power grid stability control system according to claim 1, characterized in that, The hydro-thermal unit enters the strong excitation mode, including: reaching the excitation peak value according to a preset time.

3. The collaborative multi-resource power grid stability control system according to claim 1, characterized in that, Also includes: The monitoring module is used to monitor the grid frequency, power angle, and voltage status in real time, as well as the operating parameters of each generating unit.

4. The collaborative multi-resource power grid stability control system according to claim 1, characterized in that, The frequency control module is used for primary and secondary control of power deviation of hydro-thermal units. When performing primary and secondary control of power deviation of wind and solar units, the hydro-thermal units and the wind and solar units are equivalent to single-unit systems.

5. The collaborative multi-resource power grid stability control system according to claim 1, characterized in that, Also includes: The human-machine interface is used to display the real-time operating status of the power grid, the execution status of stability control measures, and fault alarm information.

6. A method for coordinated multi-resource power grid stability control, characterized in that, include: Frequency control steps: primary and secondary control of power deviation for hydro-thermal units, and primary and secondary control of power deviation for wind and solar units; Power angle control steps: The power angle swing process of the power grid is divided into three periods: voltage drop before recovery, voltage recovery but power angle difference not pulled back, and power angle difference pull-back. During the voltage drop before recovery period, the hydro-thermal units are put into strong excitation mode until the excitation peak value is reached according to the preset time, while the wind and solar units adopt low-voltage push-through strategy. During the voltage recovery but power angle difference not pulled back, the strong excitation reference value of the hydro-thermal units is reduced, and the reactive current of the wind and solar units is reduced to restore active power. During the power angle difference pull-back period, the hydro-thermal units are taken out of the strong excitation mode, while the wind and solar units are restored to active power and the reactive power is returned to the initial value. Voltage control steps: Assess the maximum reactive load demand after a short-circuit fault according to the power grid zone assessment, and determine whether the dynamic reactive power sources deployed in each power grid zone meet the maximum reactive load demand; for power grid zones with insufficient reactive power sources, increase the reactive current during the low-voltage run-through of wind and solar turbines, and maintain the reactive current until the grid voltage recovers after the low-voltage run-through, while keeping the hydro-thermal turbines in a strongly excited state until the grid voltage recovers; for power grid zones with sufficient reactive power sources, increase the reactive current during the low-voltage run-through of wind and solar turbines, and reduce the output reactive current after the low-voltage run-through, while reducing the strongly excited reference value of the hydro-thermal turbines.

7. The method for coordinated multi-resource power grid stability control according to claim 6, characterized in that, The hydro-thermal unit enters the strong excitation mode, including: reaching the excitation peak value according to a preset time.

8. The method for coordinated multi-resource power grid stability control according to claim 6, characterized in that, Also includes: Real-time monitoring of grid frequency, power angle, and voltage status, as well as the operating parameters of each generating unit.

9. The method for coordinated multi-resource power grid stability control according to claim 6, characterized in that, The frequency control step is used to perform primary and secondary control of power deviation for hydro-thermal units. When performing primary and secondary control of power deviation for wind and solar units, the hydro-thermal units and the wind and solar units are equivalent to single-unit systems.

10. The method for coordinated multi-resource power grid stability control according to claim 6, characterized in that, Also includes: The real-time operating status of the power grid, the implementation of stability control measures, and fault alarm information are displayed through a human-machine interface.

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