Abstract:When the modular multilevel converter (MMC) arms do not have redundant sub-modules, the fault of the sub-modules decreases the output voltage capability of the faulty phase, which leads to the unbalanced output line voltage of the MMC. In order to restore the post-fault output line voltage characteristics of the no-redundant MMC and improve the utilization rate of the non-faulty arm's sub-modules, a sub-module fault-tolerant control strategy which is suitable for non-redundant MMC is proposed based on neutral point transfer (NT) and direct current component injection (DCCI) control. The fault-tolerant strategy adjusts the phase angle of the three-phase voltage through NT control for ensuring the balance of the output line voltage. In addition, a three-stage optimal DCCI amplitude calculation method is proposed. Compared with the existing methods, the optimal amplitude DCCI further improves the utilization rate of the non-faulty arm's sub-modules and increases the output line voltage amplitude. A three-phase MMC simulation model based on the PSCAD/EMTDC platform is built, and the effectiveness of the proposed no-redundant fault-tolerant control strategy is verified through the simulation results.

Abstract:Modular multilevel converter (MMC) has been widely used in wind power system. The design of insulated gate bipolar transistor (IGBT) directly affects the performance of the system. Because of the lack of theoretical guidance in the design and selection of IGBT modules, there is a phenomenon of cost wasting which is caused by a large margin selection. Based on this, a customized design method for IGBT based on dual objective optimization is proposed. Firstly, the cost and loss of the IGBT are taken as the goals of the optimization. Combined with the annual operating conditions of wind power generation system, IGBT loss is evaluated according to the probability distribution of wind speed. Then, the Pareto front is obtained by dual-objective particle swarm optimization algorithm. Finally, customized design for IGBT module and discrete components are used to design the converter. The results show that the proposed design method reduces the cost of the device and takes into account the loss and reliability of the converter at the same time.

Abstract:The onshore power system which is suitable for environmental protection needs and replaces diesel generators on board is booming. The high temperature rise of modular multilevel rectifier applied to the onshore power system reduces its operating reliability, and the loss is an important parameter to reflect the temperature rise. Ignoring other loss factors of rectifiers, a simplified model is established for the loss of switching devices, and a temperature rise analysis model of modular multilevel converter (MMC) rectifier half-bridge sub-module switching devices is established in combination with the principle of electro-thermal conversion, so as to determine the relationship between temperature rise and switch device loss. Based on the established loss and temperature rise model, the influence of carrier phase shift and nearest level approach modulation on the temperature rise of the switching device is simulated and analyzed, which is consistent with the verification under practical engineering conditions. The results show that the temperature rise of switching devices is smaller under the carrier phase shift modulation mode, and the mode of modulation is able to be used in the actual engineering to suppress the temperature rise to a certain extent. The temperature rise model constructed can provide a model basis for the follow-up study of other temperature rise suppression measures, and can verify the effectiveness of temperature rise suppression measures.

Abstract:In order to check the stress and operation reliability of modular multilevel converter valve, a new operation test topology and control method of modular multilevel converter valve is proposed under the condition of gradually increasing sub module voltage of high voltage and large capacity flexible DC converter valve. Firstly, the stress analysis of typical operation condition of the flexible DC converter valve is carried out. Secondly, combined with stress analysis, a new operation test topology of modular multilevel converter valve is proposed, and the mathematical model of the test topology is established, and its operation mechanism is expounded. At the same time, combined with the symmetry of the control parameters, the DC component in the control variables is eliminated in real time. Finally, the simulation model is built and verified. The results show that the new operation test topology and control method of modular multilevel converter valve are correct and effective. The proposed test topology reduces the voltage demand of DC test power supply, and its control method simplifies the control of test circuit.

Abstract:In the true bipolar modular multilevel converter based high voltage direct current (MMC-HVDC) systems, the probability of occurrence of the single-phase-to-ground faults at the valve-side is arguably low, but it may cause serious overvoltage on the direct current (DC) side. The overvoltage characteristics and generation mechanism is studied when a single-phase-to-ground fault occurs on the valve-side of the MMC in HVDC systems. Firstly, the charging and discharging circuits of the sub-module capacitors for each phase are given before and after blocking. The generation mechanism of the overvoltage of the arm and healthy pole line is investigated then. Finally, simulations are performed based on Xiamen two-terminal HVDC grid to verify the accuracy of the mechanism, and the effect of the blocking delay on the overvoltage is simulated and analyzed. The results show that the increase in the voltage of the arm, the healthy pole line and the metallic return line are caused by the charging and discharging of the distributed capacitances in DC lines. Besides, the shorter the blocking time, the lower the overvoltage amplitude.

Abstract:The hybrid cascaded ultra-high voltage direct current (UHVDC) system of line-commutated converter (LCC) and modular multilevel converter (MMC) in series at receiving end provides a more economical, flexible and fast transmission mode for UHVDC transmission. Based on the existing coordinated control strategy of DC power grid, the coordinated control strategy among MMC valve groups is analyzed and studied, and five coordinated control strategies are considered. Then, with PSCAD/EMTDC, the response characteristics of the above five strategies subjected to different faults are simulated respectively, including sending-end AC fault, DC line fault, receiving-end LCC AC fault, receiving-end MMC1 AC fault and MMC1 immediately shutdown and exit. Finally, based on the simulation results, the applicability of the above five coordinated control strategies is compared and analyzed. The simulation results show that strategy 1 and strategy 3 ride through effectively under various faults. Strategies 2, 4, and 5 suffer from different degrees of power reversal under DC line fault, and the measures should be taken to restrain the power reversal.

Abstract:Single-line to ground fault occurring on the grid side causes certain drops in alternating current (AC) voltage. At this time, the modular multilevel converter (MMC) system is able to achieve low voltage ride-through under fault with the injection of reactive current. However, the grounding impedance affects the topology of the whole system, thus leading to couplings among the sequence networks. Therefore, modeling and stability analysis of MMC system is of vital significance in this case. The equivalent model of MMC AC system disturbed by single-line to ground fault is established, and the process of fault ride-through with the mixed injection of dual-sequence reactive current is analyzed. Then, based on internal dynamic characteristics of sub-module capacitor voltage and arm current of MMC, the small signal model is established. The influence of impedance parameters and current couplings on small signal stability of MMC are analyzed by using the root-locus method on the basis of system instability mechanism. Finally, a 21-level MMC simulation model is built in PSCAD/EMTDC and the simulation results show that the decrease of the grid impedance or the increase of the ground impedance makes the system tend to be unstable. And the injection of negative sequence reactive current expands the stable region of positive sequence reactive current.

Abstract:Based on two retired cross-linked polyethylene (XLPE) cables with different service years and a spare cable, the changes in dielectric properties of XLPE from different positions of cable insulation are studied. The XLPE samples are sliced from the cables, and the dielectric spectra are measured at eight temperature points located between 50℃ and 250℃, respectively. The results show that the spectra of complex dielectric constant for XLPE at super-high temperature exhibits regular change with frequency. Then, the electrical conductivity and peak frequency of the relaxation peak decrease firstly and inversely increase with the cable service year, which can be good index to show the changes in dielectric properties of cables. The difference in the activation energy corresponding to the peak frequency of the relaxation peak and the central angle corresponding to the Cole-Cole plots at different insulation positions of the same cable decrease firstly and inversely increase with the cable service year, which can well reveal the difference in dielectric properties of the different positions from the same cable. The variation in dielectric property of each sample at super-high temperature with its service year can be used as an effective method to evaluate the insulation status of XLPE cable.

Abstract:Compared with AC distribution network, many problems should be solved in DC distribution network, such as fault current limiting, fault current blocking and power quality control. In order to reduce the number of equipment in DC system, a multi-functional fault current controller topology based on LCL structure is proposed, which has the capacity for fault current limiting, fault current blocking and voltage regulation. On account of the topology structure, the operation principle of LCL structure under different working objectives is studied, and the multiplexing process of filtering and limiting current of LCL structure is clarified. A fast detection method of fault current is also proposed. By matching the threshold value of voltage change rate and current change rate at different positions of current limiting device, the fast judgment of bipolar fault, single pole fault and high resistance fault are realized. Finally, the system simulation model is built to verify the validity of multi-functional of the fault current controller topology, and the rapidity of fault current detection.

Abstract:The dynamic impact effect is not considered in the design of the suspension spanning frame in previous work. In order to explore the impact resistance law of the suspension spanning frame under different engineering parameters, the impact simulation model of the ultra high molecular weight polyethylene (UHMWPE) rope used in the load-bearing cable of the suspension spanning frame is established in this paper. The influence of different engineering parameters on the impact resistance of the suspension spanning frame under accident conditions of broken wire and running wire is studied. Research results show that the minimum error between the dynamic simulation based on truss element and the experiment is 0.67%. The simulation results show that the impact load of broken wire on the suspension spanning frame is about 2~3 times that of the running wire due to the appearance of the traction plate. The impact load of the suspension spanning frame increases with the height of the fall wires, but the law of the change has some randomness. The sag changed is 4~4.5 m. Besides, the safety factor of the middle cable and the insulation net is smaller than other parts of the suspension spanning frame. The linear density and the traction plate mass of the 1 250 mm² conductor is larger than that of the 630 mm² conductor. Therefore, the 1 250 mm² conductor has larger impact on the suspension spanning frame.

Abstract:The voltage recovery of commutation bus on the rectifier side in AC/DC system always leads to the increases of DC current, thus resulting in the inverter commutation failure. In order to solve this problem, the CIGRE HVDC benchmark model is firstly taken as an example to analyze the control characteristics of control system on the inverter side during voltage recovery. The main reason of commutation failure is that the value of output current error control is small and rapidly reduces due to the large and fast increase of DC current after the control mode is switched from constant current control to constant extinction angle control. The extinction angle is small and always affected by the voltage recovery of commutation bus on the rectifier side, so that a control method is proposed to increase the extinction angle by improving the current error controller. Finally, the CIGRE HVDC benchmark model is used in PSCAD/EMTDC electromagnetic transient simulation software to verify the effectiveness of the proposed method. The simulation results show that the proposed method effectively suppresses the commutation failure caused by the voltage recovery of commutation bus on the rectifier side.

Abstract:The calculation of the induced voltage and current of the double circuit cable-overhead hybrid line is the key to the selection of the grounding switch during the maintenance. The metal sheath of the cable has the function of electrostatic shielding on the wire core, and has different electromagnetic shielding effect on the wire core according to the different grounding mode of the sheath. Therefore, the calculation of induced voltage and current between the cable circuits is different from that of overhead lines. The electromagnetic induction of the operation line to the maintenance line is studied for the typical 220 kV double circuit cable-overhead hybrid line. Firstly, according to the electromagnetic coupling, the calculation formula of the induced voltage and current of the hybrid line is derived. Secondly, the simulation model is built to analyze the influence of the length proportion of the cable section on the induced voltage and current, the influence of the three grounding modes of the cable sheath(single terminal grounding, double terminal grounding and cross interconnection terminal grounding on the induced current), and the influence of the equivalent grounding resistance of the grounding switch on the induced current. The results can provide a theoretical reference for the selection of grounding switches in hybrid line.

Abstract:The AC algorithm solves the power flow equations by iterations, which is computationally infeasible to the online security analysis of power systems. A fast load flow calculation method is proposed based on a convolutional neural network (CNN). As to the offline training stage, the proposed method extracts inputs (initial feature maps) based on the changes in operating conditions and topologies. In abundant training samples, the CNN and maps the nonlinear relationship between the extracted feature maps and the targeted load flow results. When it comes to the online applications, the proposed method directly calculates the feature map and delivers the load flow results based on the CNN trained offline. As is indicated in the N-2 load flow simulations of four typical IEEE systems, the generalization capability is guaranteed. Compared with the AC algorithm, the proposed method accelerates the power flow computation by eighty times. The accuracy is enhanced by nearly one order of magnitude, compared with that of the traditional artificial neural network (ANN).

Abstract:With the development of power grid scale and the increase of load, the difference of reactive voltage in different regions is enhancing, and the problem of voltage stability in the center region of the load is increasingly prominent, while high voltage and reactive power surplus are likely to occur in some periods in the lighter load region. It is urgent to comprehensively evaluate the reactive voltage status in multiple regions of the power grid, so as to provide data support for the coordinated control of global reactive power and the interaction between regions. In view of this, an evaluation method based on fuzzy C-means clustering (FCM) and dynamic time warping (DTW) is proposed. In this method, FCM is used to fuzzy cluster the index data of multiple time sections to form the cluster center and extract the average characteristics of the samples. At the same time, DTW is used for pattern recognition of the cluster center data and the reference samples, which can evaluate the voltage support ability of multiple time sections. Taking a typical power grid as an example, the effectiveness of the proposed evaluation method is verified.

Abstract:The commutation failure of high voltage direct current (HVDC) transmission system has a huge power impact on the AC system. It is necessary to accurately detect the commutation failure of the HVDC to take targeted safety and stability control measures. At present, the stability control device which has already been used in engineering identifies the commutation failure of HVDC depending on the signal of DC control and protection system. When DC control system crashes or the channel with stability control device is abnormal, the stability control device dose not operate correctly. The characteristics of electrical quantities under the condition of DC commutation failure and its identification principle are studied, while the criteria and applicability of DC control and protection system commutation failure protection are introduced. Then, the criteria of commutation failure, continuous commutation failure and multi DC simultaneous commutation failure identification are put forward, which are suitable for safety and stability control. The real time digital system (RTDS) test results based on the actual control and protection system of Bin-Jin HVDC show that the proposed criteria can accurately judge the commutation failure of DC system, the frequency and time interval of continuous commutation failure according to the requirements of safety and stability control.

Abstract:Network topology optimization which is a new technology improves the distribution of system power flow and system safety and economy by changing the network topology dynamically during the power system operation. Aiming at the problems of poor flexibility and low computation efficiency in the existing static and dynamic network topology optimization methods, a semi-dynamic network topology optimization method is proposed in this paper. Based on this method, the auxiliary optimization of power system operation mode is carried out. Firstly, the advantages and disadvantages of current static and dynamic network topology optimization methods are described, and then a semi-dynamic network topology optimization method is proposed. Secondly, on the basis of static, dynamic, and semi-dynamic network topology optimization methods, a general form of auxiliary optimization model of day-ahead power system operation is constructed. By using linearization technology, the proposed dynamic economic dispatch model is transformed into a mixed integer linear programming problem. Finally, test results of the IEEE 14 bus system and IEEE 118 bus system demonstrate that the proposed method achieves the coordination both the power system operation flexibility and computation efficiency.

Abstract:It is difficult to predict accurately the bus load by traditional point prediction methods due to the violent fluctuation of some industrial bus load. A day-ahead interval prediction model of bus load based on the combination of convolutional neural network (CNN) and quantile regression long short-term memory (QRLSTM) is proposed in this paper. Firstly, the denoising auto-encoder is used to obtain the historical load data by de-noising the high frequency fluctuation of industrial load power. Then a one-dimensional CNN network encapsulated by time distribution layer is used to extract load features to improve the learning efficiency of the whole model. Finally, the QRLSTM model with attention mechanism is established for feature learning, and the load interval prediction results under different quantiles are calculated. The day-ahead interval prediction results of bus load are obtained by an industrial 220 kV bus and a commercial-residential 220 kV bus. The results show that the proposed prediction method has generally larger interval coverage, smaller interval mean width, smaller interval cumulative deviation and higher prediction effectiveness than the conventional quantile regression method.

Abstract:The soft open point (SOP) using the back to back power converter can flexibly, fast and accurately regulate the power flow among the adjacent feeders by implementing the multi-targets control including nodes voltages and network losses and also has the capability to isolate the fault and recover the power supply. However, the range of power restoration is strictly limited by the SOP capacity. A hybrid soft open point system with a partial scale back to back converter and a load switch parallel connected is proposed. The power flow and voltage distribution could be regulated by the back to back converter as usual. And the load switch could realize power recovery for all the customer interruption under the fault condition. Moreover, the back to back converter can flexibly regulate the power flow through the load switch and help realize the zero current turning off of the load switch, which can effectively extend the working life of the load switch and reduce the equipment cost. Furthermore, the performance of the proposed hybrid SOP is verified by the simulation results.

Abstract:Spatial load forecasting is of great significance for distribution network planning and construction. In order to improve the accuracy of distribution network spatial load forecasting, a distribution network spatial load forecasting method based on entropy weight method and grey relational analysis-extreme learning machine (GRA-ELM) is proposed. Firstly, the districts in the planning area are seperated according to the nature of land use. The influencing factors of different types of load are analyzed, and the index system of spatial load density is established. Secondly, the entropy weight method is used to distribute the weight of load density index for different types of load. Then, GRA is used to select the training samples which are similar to the load density index of the plot to be tested. Finally, the samples are brought into the extreme learning machine (ELM) model after the parameters are optimized by particle swarm optimization (PSO), and the prediction results are obtained. The performance of the proposed method is verified by an example and the results show that the proposed spatial load forecasting method has high accuracy than other methods does.

Abstract:Dielectric loss is one of the important indexes to evaluate the insulation state of power cables. As the current emerging detection voltage, the oscillating wave voltage has a good equivalence with the power frequency AC voltage, and has a wide range of applications in the field of partial discharge detection. However, the dielectric loss measurement has not been carried out in depth, which has limitations for the integrated detection of insulation status. In order to solve the problem of current limitations, a cable dielectric loss measurement method based on the oscillating wave test technology is proposed. During each operation of the oscillating wave test system, the voltage or voltage-current data of the cable sample are collected, and then the waveform parametersare extracted through data post-processing to obtain accurate dielectric loss. At the same time, the two measurement methods are compared and the field error is analyzed, and the dielectric loss angle measurement method based on the oscillating wave voltage and current waveform has high accuracy and practicability, and a method to solve the problem of zero drift is proposed. Finally, simulation and experimental results verify the feasibility and effectiveness of the method.

Abstract:In order to realize the localization of high voltage direct current (HVDC) cable insulating materials, the insulating materials of HVDC flexible cable with the high carry capacity (90℃ of the working temperature) are prepared by nano filler doping method in this paper. The key parameters including space charge, resistivity, DC breakdown strength are investigated, and the results are compared with that of HVAC insulating materials and external HVDC insulating materials. It is found that the developed insulating materials have good space charge suppression performance at 20℃ and high temperature (90℃), and the electric field distortion ratio is less than 5%. Comparing to the two other materials, its resistivity increases by 10 times and the resistivity temperature coefficient decreases by 1/3 at high temperature, so it decreases the insulation heat loss and fits to the design of the cable system. Its DC breakdown strength at high temperature is 1.27~1.6 times as much as that of the two other materials. The research shows that the materials are suitable for the insulation of HVDC flexible cable with the working temperature of 90℃ for its perfect electrical performance.

Abstract:Insulators which are widely used in all aspects of the power system play an important role in ensuring the safe and stable operation of the power grid. Existing methods are only able to identify obvious defects such as self-explosion missing and foreign objects, and cannot deal with local damage, cracks and other situations. In response to the above problems, an insulator defect detection method based on enhanced feature pyramid and deformable convolution is proposed. On the basis of the original high and low feature fusion, an enhanced bottom-up path is added, which improves the information transfer between high and low feature maps, and realizes the effective extraction of local defect features. The introduction of deformable convolution, adaptively changes local sampling points, reduces the impact of background interference, and further improves the applicability of the model. Comparative experiments using insulator images collect in multiple scenes show that the proposed method achieves greater detection accuracy improvements on different basic networks, and can be widely used in various insulator application scenarios such as substations and high-voltage transmission lines.

Abstract:The linear phase-shifting transformer has the advantages of simple structure and realize equal shifting at any angle, and it is widely used in multiple superimposed inverter systems. However, it is easy for linear phase-shifting transformer to lead an end effect, which affects the working performance of the transformer itself. First of all, on the basis of the principle of magnetic circuit similarity, it is analyzed the similarity of the iron core magnetic circuit between the linear motor and the rotating motor in this paper. Secondly, it is obtained the value of output current harmonic content and system efficiency with changing the effective air gap length. Finally, it is analyzed the influence on the leakage flux at the end of the transformer by adding a magnetic isolation material to the side teeth. The simulation results show that it effectively weakens the influence of the side effect and improves the application performance of the linear phase-shifting transformer by the reasonable selection of effective air gap length and the addition of magnetic isolation materials.

Abstract:With the continuous improvement of electrochemical energy storage technology in power systems, the safety of electrochemical energy storage technology has received more and more attention. It takes the lithium iron phosphate battery module (8.8 kW·h, 25.6 V, 344 A·h) for energy storage as the research object, and conducts three constant current overcharge tests with different magnifications (0.4C, 0.5C, 1C) to study its advantages. The thermal runaway characteristics of overcharge under different charging rate conditions are supplemented by starccm+ software for thermal field simulation calculations. The experimental results show that the battery module catches fire under 0.5C (172 A) and 1C (344 A), and the fire-starting time decreases as the charging rate increased. Charging rate has a great influence on the thermal runaway behavior of lithium iron phosphate battery modules. With the increase of charging rate, the thermal runaway maximum temperature and peak voltage increase, and the overcharge process time decreases with the increase of charging rate. Under different charging rates, the charge voltage when the first battery safety valve opens are 1.7 times of the rated voltage, which is further regarded as a warning parameter for battery thermal runaway. A reference for the safety improvement of lithium iron phosphate batteries for energy storage and the battery management system (BMS) for the safety management of overcharge faults is provided.

Abstract:With the growth of power demand and the increase of environmental protection requirements, the use of SF₆ gas is gradually limited. SF₆ mixed gas reduces the amount of SF₆ gas to a certain extent and has been used in electrical equipment. The insulation change caused by SF₆ mixed gas leakage in 220 kV gas insulated switchgears (GIS) is studied. By changing a small amount of pressure and mixing ratio, the insulation performance change of the mixed gas is explored, and the influence law of pressure and mixing ratio factors on the breakdown voltage of power frequency is analyzed. The insulation strength curves of mixed gases in different proportions at each pressure are obtained, so as to obtain the air supplement strategy to ensure the safe and stable operation of the equipment. It is found that the breakdown voltage of mixed gas changes with the increase of pressure and mixing ratio, and the nonlinear degree increases, and the boundary values of mixing ratio and pressure for safe operation of equipment are obtained. The study can provide operation and maintenance procedures and technical standards for SF₆/N₂ mixed gas insulation equipment. At the same time, it lays the foundation for the development of mixed gas detection technical standards.

Abstract:Due to the poor elasticity of the existing transmission line tower materials, and the difficulty of applying the body structure to the geographical characteristics of the goaf, an optimization method of transmission line tower design for goaf is proposed. Firstly, a method of transmission line tower topology optimization is proposed. By choosing appropriate tower support form, edge form, inner layer number and redundancy number, the optimal tower structure is obtained. Then, fiber reinforced composite (FRP) is used to replace the traditional pole tower material to design the cross arm, so as to ensure that the pole tower is in the elastic working state and improve its bearing capacity. Finally, based on the back-tracking search algorithm (BSA), the optimization problem of tower topology is solved. Under the constraints of stress and displacement, the optimization of tower size, shape and topology is realized. Based on the finite element program developed in Matlab, the performance of the proposed method is demonstrated. The results show that compared with other methods, the structure weight of the proposed method is significantly reduced, and the structure is more elastic, which is suitable for the practical application of goaf.

Abstract:Image recognition of transmission line is an important part in the automatic inspection process of power equipment. For the problems of traditional line detection methods that requine manual design of target features and poor generalization ability, an image recognition method for transmission line based on deep convolutional network (DeepLab v3+) is presented. Firstly, the DeepLab v3+ network model is applied to realize the preliminary segmentation of the lines. This model can automatically learn line features by multi-layer convolutions, and merge the low-level detailed features with the high-level semantic features through a decoder structure to improve the accuracy of line pixel segmentation. Secondly, in order to refine the segmentation results, the improved minimum point pair method and length threshold method for removing broken and pseudo lines are proposed. Finally, an eight-direction search method is used to extract and number each line. The experimental result shows that the proposed method can better extract lines in the transmission line image.

Abstract:In order to evaluate the frequency recovery capability of AC/DC hybrid power grid after fault accurately and quantitatively, a frequency resilience evaluation method for receiving-end power grid with multi-high voltage direct current (HVDC) feed-in is proposed. Firstly, electromechanical transient simulations are carried out under different HVDC blocking faults so that the frequency variation of power grid is obtained. Then, the area between the frequency change curve and the constant frequency curve during the primary frequency regulation is calculated to evaluate the frequency resilience of the power grid. In this way, the mapping relationship between various DC blocking faults and frequency resilience index is established successfully. Proposed method not only can evaluate the frequency resilience of multi-HVDC feed-in power grid, but also can analyze the effect of different measures on improving frequency stability. In the end, taking the actual East China power grid as an example. The adaptability of the proposed index to evaluate the frequency stability of power grid is analyzed. The stability improvement effect of various measures such as increasing gas turbine is quantitatively tested. The results show that the proposed frequency resilience evaluation method is effective and correct, which can effectively guide the planning and operation of the actual power grid.