Abstract:直流输电换相失败抵御能力提升新技术

Abstract:Aiming at the problem of subsequent commutation failure during the fault recovery period after the first commutation failure of high voltage direct current system,the recovery process is divided into the first commutation failure (stage 1),the beginning of system recovery (stage 2),and the current deviation control (stage 3) based on the action logic of direct current (DC) system control link in this study. It could be found that excessive recovery of DC current will lead to subsequent commutation failure during the stage 3. On this basis,an improved strategy of voltage dependent current order limiter (VDCOL) is advanced,which uses instantaneous voltage to detect the voltage amplitude of commutation bus in real time. The minimum current instruction value of the VDCOL is dynamically adjusted in accordance with the commutation bus voltage after the alternating current (AC) faults,so as to achieve the purpose of suppressing subsequent commutation failures. Finally,the effectiveness of this strategy is proved to suppress subsequent commutation failures under different failure conditions by the simulation results based on the CIGRE benchmark model.

Abstract:Subsequent commutation failure of the high voltage direct current (HVDC) transmission system has a seriously negative impact on the stable operation of the AC-DC hybrid power grid. To reduce the probability of subsequent commutation failure,an adaptive control method for adjusting the power recovery rate of the DC system is proposed in this paper,which combines the power recovery rate of the DC system during the recovery process after the first commutation failure with the severity of AC failure. Firstly,the law of the electric quantity change during the fault recovery process and the factors affecting the subsequent commutation failure are analyzed. Secondly,according to the power recovery rate and the AC voltage drop,the trigger angle of the inverter side during the fault is dynamically adjusted by the proposed control strategy to increase the commutation margin,thereby suppressing the subsequent commutation failure for HVDC. Finally,the control method is simulated and verified based on the CIGRE benchmark model of HVDC. The results show that the proposed control method can adjust the compensation size of compensating trigger angle adaptively according to the voltage drop and DC power recovery characteristics,thereby improving the commutation margin to suppress subsequent commutation failures and speeding up the HVDC system failure recovery.

Abstract:For the wide application of high voltage direct current (HVDC) transmission engineering,the continuous commutation failure of line commutated converter HVDC (LCC-HVDC) has a seriously negative impact on the stable operation of the power system. Therefore,in order to mitigate the continuous commutation failure of LCC-HVDC in hybrid multi-feed HVDC system,from the perspective of increasing the LCC-HVDC commutation voltage,a coordinated control strategy for hybrid multi-infeed HVDC systems is proposed in this paper. According to the real-time reactive power shortage of the conventional DC,the reactive power and active power of voltage source converter HVDC (VSC-HVDC) output are dynamically adjusted by this strategy,thereby changing the transient stable operating point of VSC-HVDC. Through the coordinated control of this strategy,the continuous commutation failure of LCC-HVDC is suppressed and the transmission capacity of the active power of the DC transmission system is greatly improved. Finally,a simulation model of the hybrid dual-infeed HVDC system is built in PSCAD/EMTDC,and the effectiveness of the coordinated control strategy is verified.

Abstract:Aiming at the problem of large inrush current when the commutation fails in the hybrid direct current (DC) transmission system,the relationship between the inrush current amplitude and the voltage source converter (VSC) is firstly derived. The number of submodule invested by VSC is a key parameter to determine the inrush current when the commutation fails. Then,the main factors affecting the commutation capability of the line commutated converter (LCC) are studied,and a commutation failure suppression strategy based on active current limiting is proposed. The DC disturbance amount and the accurate current (AC) disturbance coefficient are added to the VSC modulation wave,thereby changing the switching mode of the submodule and suppressing the peak value and rising speed of the commutation failure impulse current. Finally,the simulation model of the hybrid DC transmission system at both ends is built in Matlab/Simulink to verify the effectiveness of the proposed strategy in the event of different degrees of voltage drop faults on the AC side of the inverter station. The results show that the proposed strategy limits the inrush current and reduces the current stress of the bridge arm,thus effectively preventing continuous commutation failure.

Abstract:Constant extinction angle control based on prediction is a basic control strategy of inverter in line-commutated converter high-voltage direct current (HVDC) system. However,system commutation failure suppression ability and system recovery are determined by the proportionality coefficient in the current error control. To clarify the influence mechanism and propose countermeasures,the function of current error controller is analyzed based on the basic control strategy. Then the influence mechanism of proportional coefficient in current error controller is studied at both the initial stage of fault and fault recovery stage. It can be concluded that the mitigation effect of commutation failure would perform worse if the proportion coefficient of current error control is set to positive. Nevertheless,the recovery performance of the HVDC system would be better. Based on this a novel adaptive current error control is proposed,which can quickly identify the system state through detection modules and output an appropriate proportional coefficient to take into account the commutation failure suppression ability and recovery process of the system. Finally,high-voltage direct current test model is built based on PSCAD/EMTDC,and the correctness of the theoretical analysis and the effectiveness of the proposed countermeasures are verified by simulation test.

Abstract:Various barriers attached to the transmission line pose a huge threat to the safe and stable operation of the power grid. Traditional barrier removal methods either have safety hazards or consume high energy,and most of them require power outage. With the advantage of high energy and good collimation,laser can be used to shoot down foreign bodies or melt ice without contact from a distance. Therefore,the application status and development of laser barrier removal technology in power grid are sum up. Firstly,the principles of removing different types of barriers such as foreign bodies,ice and tree barriers using laser are summarized. Secondly,the features of several lasers which are commonly used in barriers removal areas are compared. Finally,the effect of some parameters such as laser wavelength,laser power and spot diameter on barrier removal efficiency are analyzed. The safety threshold of power density and irradiation time when lasers irradiate transmission line and insulators are also studied. Laser barrier removal technology is widely used to remove foreign bodies hanging on the lines,but removing ice,tree barriers or other barriers are limited by the removing efficiency and cost. These are still need to be further developed. The related researches and applications of this technology are reviewed in this paper,which can provide a reference for technical personnel in the field of electrical engineering technology.

Abstract:Multi-station integration realizes the optimal usage of multiple energy by integrating the functions of substations,photovoltaic power stations,charging stations and other stations,but the location evaluation needs to take into account the influence factors. In the location evaluation weight design,it is difficult to design characteristic indices and common indices for each single station. The common indexes have different degrees of influence on each single site. To solve the problem,a method for the construction of multi-station integration location evaluation index system is designed. Also,the integration of each single station indices is realized. At the same time,the combination weight calculation method based on the analytic hierarchy process and multi-station index system is designed. Firstly,the weights of all indices are calculated for all single stations. Then the weights of the single station are designed. Finally,two weights are combined to get the combination weights of all indices. The fuzzy comprehensive evaluation method is used to score each index of the candidate sites,and the optimal site is selected after a comprehensive evaluation considering the weight. The effectiveness of the proposed evaluation system and method is verified by an example.

Abstract:In this paper,the control characteristic of cascaded hybrid high voltage direct current (HVDC) system is studied. The influence mechanism of modular multilevel converter (MMC) inverters to the whole hybrid HVDC are investigated,and the complete voltage-current characteristic curves of the hybrid HVDC are obtained in droop control modes. Compared with the master-slave control,MMCs in droop control have ability to control both DC voltage and DC power,and the power reverse transmission will not occur. However,MMCs in droop control cannot control DC voltage accurately. Thus,an adaptive droop control strategy of cascaded hybrid HVDC system is proposed. The droop curve can be moved in real time adaptively according to DC current,which avoid the fluctuations of DC voltage due to the change of DC current. Finally,the simulation results verify the effectiveness of the proposed strategy based on PSCAD/EMTDC. This strategy can adjust the droop curves adaptively and realize accurate control of DC voltage in hybrid HVDC system,which improves the stability of the hybrid HVDC system.

Abstract:The wide application of distributed energy storage has effectively solved many problems caused by large-scale distributed generation (DG) access to the distribution network and the rapid increase of load on the planning and operation of the power grid. Distributed energy storage has the characteristics of fast power throughput,high control accuracy,flexible installation,and multi-subject benefits,which can effectively ensure the safety and stability of power supply in the distribution network. The development status of distributed energy storage is sorted out. The advantages and disadvantages of distributed energy storage application modes at home and abroad are analyzed in recent years according to its access location on the DG side,the medium and low voltage distribution network side,the user and the microgrid side. Various mathematical models and optimization algorithms for the optimal configuration of distributed energy storage are compared and analyzed in terms of its location and capacity. Combined with the problems existing in the configuration process of distributed energy storage,the development trend of distributed energy storage is prospected.

Abstract:In view of the accommodation problem of large-scale wind power integration,a robust unit commitment optimization method considering demand response and pumped storage units is proposed. On the one hand,the mathematical model considering the operation characteristics of demand response and pumped storage units is established to improve the flexibility of system operation through collaborative optimization. On the other hand,the uncertain set considering the uncertain budget is used to describe the random fluctuation characteristics of wind power. Considering the system operation constraints and robust feasibility constraints,a robust unit commitment model is constructed by adopting the rescheduling strategy based on an affine compensation mechanism to minimize the system operation cost. Furthermore,the robust optimization model is converted into a certainty mathematical programming problem according to the duality principle,and the correctness and effectiveness of the proposed method are verified by numerical test results on the modified IEEE 39-bus test system.

Abstract:As the installed capacity of wind power generation is increasing continuously,analysis of the impacts on the voltage stability of power system during and after faults is important for the stable operation of power systems. An integral-integral estimate based method is proposed,which is equivalent to the concept of input-to-state stability (ISS),to perform quantitative voltage stability analysis for the power system integrated with doubly fed induction generators (DFIG)-based wind turbine. The advantage of integral-integral estimate is that the fluctuation information of external disturbances on the time scale can be considered. Firstly,according to the quantitative assessment results of subsystems,a system level quantitative stability assessment method based is proposed on small gain theory. Then,the voltage stability of power system integrated with DFIG is analyzed based on the proposed approach. Time-domain simulation on a power system integrated with a DFIG-based wind turbine verifies the accuracy of the proposed method.

Abstract:Voltage sags are unavoidable and seriously harmful to sensitive loads. Reasonable configuration of limited monitors can reduce monitoring costs,provide data support for voltage sag management and reduction of voltage sag hazards. Therefore,the optimal configuration of voltage sag monitors is important. Aiming at the traditional method that ignores the inconsistency of the degree of voltage sag damage in different areas,a joint optimal configuration model of voltage sag monitor considering the monitoring reliability of sag sensitive area and the location of phasor measurement unit (PMU) is proposed. Considering the considerable sag as the constraint condition,the minimum number of monitors and the widest coverage of the sag sensitive area are used as the goals to form an optimized configuration model. In this model,the PMU is configured to assist in monitoring voltage sags. In addition,the Zeroin method is used to improve the accuracy of the exposed area calculation. The IEEE 30-bus system is used in simulation to prove that the difficulty of balancing the monitoring cost with the monitoring capability of sensitive areas is overcome by the proposed method. The proposed method can ensure the minimum number of monitors and high redundancy coverage of sensitive loads,thus the economic benefits.

Abstract:In order to make full use of marine renewable energy such as waves and tidal power generations,an optimal allocation method of marine energy power generation resources with the objective of optimal absorption rate is proposed for the island power grid. Firstly,Gaussian mixture model (GMM) is used to describe the random fluctuation of marine energy generation and generate the output scene. Secondly,the optimal allocation model of marine energy power generation resources for island power grid is constructed with the objective of optimal marine energy absorption rate. Then,the permeability,absorption rate and source-load matching degree are comprehensively analyzed to obtain the optimal allocation scheme. Finally,based on actual island load,wave and tidal current data,an example of optimal allocation of marine energy power resources is built,and the value range of permeability constraint in optimal allocation of resources is analyzed. The results show that the source-load matching degree increases at first and then decreases under different permeability constraints. Within the range of the optimal permeability constraint,there are little difference and same trend between the optimal configuration results of the GMM and the measured data scenes,which verify the effectiveness of the GMM to generate marine energy output scenes.

Abstract:DC fault current limiter (FCL) is a key device for suppressing DC short-circuit fault currents,which is important in AC/DC hybrid grid. In this paper,topology of a multifunctional modular DC FCL is proposed,which consists of multiple series-connected power electronic modules. On the basis of analyzing its working mechanism,three functions of fault current limit,energy release and DC grid voltage support are realized. The operation mechanism of the multifunctional modular DC FCL is analyzed in detail. A typical configuration scheme is presented for its application in AC-DC hybrid grid. The design of control strategy is completed for the three functional corresponding operation modes. In order to verify the effectiveness of the topology and control strategy,a multi-case simulation model is constructed in Matlab/Simulink. The simulation results show that the proposed modular DC FCL topology and control strategy satisfy the requirements for fault current limiting applications under various fault conditions in AC/DC hybrid grid.

Abstract:The capacity optimization and allocation of hybrid microgrid with multiple distributed generations is an important aspect of microgrid design. The capacity allocation problem of the integrated microgrid system involving wind farm,photovoltaic power station and hydrogen production-hydrogen storage-power generation system is studied in this paper. Firstly,three investors of wind power,photovoltaic and hydrogen generation-hydrogen storage-power generation system are established,and the optimal allocation model of wind-photovoltaic-hydrogen microgrid capacity based on non-cooperative game is established with the goal of maximizing the profit of each investor. Secondly,considering economic factors such as investment cost,operation and maintenance cost,power purchase and sale cost,wind and light abandonment penalties and load interruption penalties of each game player,the capacity allocation of participants in the game is optimized individually using the particle swarm algorithm. Meanwhile,the Nash equilibrium point that maximizes the revenue of each game player is determined. Finally,the wind speed and light intensity data of a typical month in the region of Xinjiang is used for the arithmetic analysis of the microgrid capacity configuration. The results show that the model can ensure the reliability of power supply with relatively low monthly integrated cost and realize the reasonable allocation of microgrid system capacity.

Abstract:The impact of carbon trading policies is rarely considered in the current optimal operation strategy of integrated micro-energy network system. For this reason,a optimization operation model of hybrid energy storage micro-energy network that takes into account the cost of carbon emissions is proposed in this paper. The model first combines source-load-storage and energy conversion devices for an integrated micro-energy network system configuration,and establishes an optimial objective function considering carbon allowances according to the implementation scheme for carbon emission allowance allocation. The simulation is then carried out on the basis of data from a certain region,and the results of the optimised operation of the system to meet the minimum cost of carbon emissions are obtained by using Gurobi. The results of the calculation examples show that the free carbon emission allowance can reduce the operating cost of the integrated micro-energy network system and affect the system operation strategy. The model proposed in this paper can reflect the impact of carbon emission cost factors on energy consumption structure,and provide reference and basis for the configuration and operation of the energy structure of the integrated micro-energy network system.

Abstract:Due to the limited rated power of individual power electronic transformer (PET),many PETs are always connected in parallel in practice. High-order harmonic interactions occur when PETs are in operation,resulting in a rise in the amplitude of the output high-order harmonics. Thereby,the power quality is influenced. The safety of PETs is also threatened by the high-order harmonics. In order to control the switching harmonics among the parallel PETs,a pulse width modulation (PWM) synchronization strategy based on the mixed information which is the combination of cloud signals and edge signals is proposed in this article. The basic idea has two parts. Firstly,the PWM synchronization is realized according to the cloud signals when the communication system works well. Secondly,the realization of PWM synchronization is switched to edge signals during the communication faults. It is proved that the high-precision and high-reliability can be guaranteed by the proposed strategy. The high-order harmonics can be coordinated-controlled well. Doing so,the interaction of high-order harmonics among PETs can be eliminated. The proposed strategy can be easily implemented due to limited requirement of additional hardware. With using the proposed strategy,the power quality and the reliability of PET can be improved.

Abstract:In cable fire test,a fire source is essential for the fire performance evaluation. Most of the existing fire sources for power cable are based on chemical fuel,which is unable to represent the cable fire caused by fault arc. Therefore,to simulate the ignition of power cable by fault arc,a fire source based on electrical arc is developed in this work. Firstly,the induced voltage on the metal armor layer is theoretically analyzed when the 110 kV cable has the ground wire stolen or the cross interconnection wires on both sides are stolen. Voltages can reach thousands of volts. Secondly,the pre-breakdown voltage and sustained voltage of the metal-to-ground arc in power cable and the Jacob's Ladder arc are compared. It is found that the breakdown characteristics of both arcs are similar for applied ac voltage with frequencies of 50 Hz and 20 kHz. Thirdly,a fire source based on Jacob's Ladder arc is proposed for the ignition of power cables. Experimental results show that the 110 kV cable can be successfully ignited by this fire source,and the flame is able to spread both vertically and horizontally. Finally,the conclusion is that the high frequency Jacob's Ladder arc can simulate the characteristics of the fault arc and effectively ignite the 110 kV cable.

Abstract:Surface flashover is an important accident threating the safe operation of gas-insulated switchgear (GIS). Non-invasive surface potential measurement for flashover test device with finger-shape electrodes is proposed,and the feasibility of this device is analyzed by finite element software. The results show that non-invasive measurement error is 2.42% under simulation parameter settings in this paper. Surface potential of epoxy with nano-SiO₂ mass fraction of 2% is measured using this device and the ascending applied voltage step is 0.5 kV/5 min. When the applied voltage is unable to induce flashover phenomenon,Maxwell-Wagner interface polarization caused by nanoparticle addition causes surface potential decay process. When the applied voltage approaches flashover voltage,surface potential presents periodic rise phenomenon in the decay process and the frequency of rise phenomenon becomes faster as the applied voltage higher. Periodic rise phenomenon in surface potential decay process before flashover can be used as a signal for predicting surface flashover. Fluctuation of surface potential in the continuous flashover process is smaller than that of intermittent flashover and the interval between adjacent flashover becomes shorter,which is related to the fact that surface burning path in the continuous flashover is prone to flashover. Surface potential measurement of DC flashover provides guidance for flashover prevention and flashover severity evaluation.

Abstract:Partial dampness is the initial stage in the bushing damp process,so the effective diagnosis of partial dampness can avoid the further development of the damp. The partial damp diagnosis method of bushing based on the frequency domain spectroscopy (FDS) is proposed in this paper. Firstly,oil-paper insulation samples with different moisture content are prepared,and partial damped samples are formed through combination. Then the FDS characteristics are obtained. The results show that partial distribution of moisture leads to oil-paper insulation interfaces with different moisture content,and the interface relaxation polarization loss peak is introduced in the FDS curves. The greater the degree of partial dampness in the radial direction,the greater the amplitude of the loss peak,and it moves to the high frequency direction. The effectiveness of the diagnosis of partial dampness of bushing based on the characteristics of the interface relaxation polarization loss peak is verified by the simulation model of the transformer bushing. It shows that a new method for early fault warning and diagnosis of the transformer bushing is provided.

Abstract:To solve the problem of traditional pollution detection methods on the prevention and control of pollution flashover of transmission line insulators,the non-contact and high-resolution hyperspectral technology is used to study the on-line pollution detection technology. At the same time,an insulator pollution level identification technology based on wavelet packet energy spectrum feature optimization is proposed to effectively extract the spectral features reflecting the pollution degree and weaken the influence of redundancy and interference information. Firstly,the spectral images of insulator samples with different pollution levels are segmented to extract the spectral mean curve of pixels in uniform pollution area. Secondly,the difference of light intensity uniformity and environmental noise of different images are preprocessed,and the differentiability among different pollution levels is improved by logarithmic transformation. Thirdly,the feature extraction of wavelet packet energy spectrum is performed on the preprocessed spectral lines. Finally,a pollution level recognition model based on the proposed features and support vector machines (SVM) is established. The experimental results show that the SVM pollution level recognition model based on wavelet energy spectrum features achieves 99.8%,and it has higher recognition accuracy than full band data or principal component analysis (PCA) feature data does.

Abstract:Microgrid system contains a variety of distributed generations. In order to reduce the power generation cost of the microgrid,it is necessary to apply an optimization algorithm to dispatch the microgrid. It is prone to fall into local optimum by traditional optimization algorithms when solving microgrid scheduling,resulting in a decrease in convergence speed. Therefore,based on the sparrow search algorithm (SSA),a reverse mutation sparrow search algorithm (RMSSA) is proposed. Firstly,the reverse learning strategy and adaptive t-distribution variation are used to expand the optimization range of SSA,so as to improve the diversity of the population and the search ability of SSA. Then,a microgrid optimization scheduling model aiming at the lowest comprehensive operating cost is established. Constraints such as constant power balance,charge and discharge rate,ramp rate,are used to solve the optimal scheduling model of the microgrid by using RMSSA. The comparative simulation results show that the proposed algorithm has good global search ability. The algorithm is superior to the original sparrow search algorithm,gray wolf algorithm and bat algorithm in terms of convergence speed,optimization accuracy and stability,and it brings comprehesive benefits to the microgrid.

Abstract:To solve the problem of slow response and low accuracy in the traditional image recognition method of transmission line target inspection,an improved faster-region convolutional neural network (Faster-RCNN) deep learning recognition algorithm is proposed. In this paper,the image features are extracted by zeiler and fergus net (ZFnet) and the ZFnet model parameters are reset to obtain more target details. Then,the Faster-RCNN is used to detect the target. The target candidate box is generated by the sub-network region proposal model and the parameters are tuned by the fast-region convolutional neural network (Fast-RCNN). In addition,the refining stage is introduced into the output part of the Faster-RCNN to increase the refinement of classification and regression of the target features. And then the multiple bounding boxes with the target are combined to achieve accurate classification and coordinate positioning. The results of the experiments show that the improved Faster-RCNN algorithm can effectively identify the transmission line equipment and its defects. The overall recognition rate of the method could reach 93.5% within 1 s of the response time. Compared with the image recognition and the deep learning such as single shot multibox detector (SSD) and you only look once (YOLO),the proposed algorithm improves the identification accuracy and response speed of power equipment,and has certain advantages in intelligent inspection of transmission lines.

Abstract:The establishment of failure risk assessment on the secondary system in smart substation can help power gird company timely arrange maintenance when the failure risk of equipment accumulates to a certain extent,thus effectively preventing systematic failure. In this paper,a probabilistic failure model is established through Weibull probability distribution function from a perspective of reliability engineering. According to the type tests and various daily operation statistics of secondary equipment,the regression equation calculated by the average rank method and least square estimation can obtain the model parameter estimation. By doing so,the equipment failure model close to the real operation condition can be obtained. Moreover,the relationship between the failures of the secondary system and a single equipment is established through the fault tree. Therefore,the risk probability distribution function of top event in secondary system can be calculated quantitatively,which can provide auxiliary decision for risk warning and state overhaul. Finally,it is verified by the numerical results that the proposed secondary equipment failure model can provide a reference for accurate time arrangement for system maintenance.

Abstract:Linear flux-switching permanent magnet (LFSPM) machines have high power density and simple robust stator structure,which shows significant potential in long stroke applications. However,linear motors are required to have high thrust density and low thrust ripple in many applications. Therefore,the research on the issues causing the thrust force ripple and corresponding suppression methods are important means to enhance the application potential of the LFSPM machines. Through the finite element analysis (FEA) method,the end effect of LFSPM machine is improved by using different structures of the additional teeth,and the end force is reduced. Based on this,different thrust ripple reduction methods are employed and compared to suppress different thrust ripple components of the LFSPM machine. In the process of comparison,a step (staggered tooth) displacement selection method is given. It shows that each structure can reduce the thrust force ripple while taking into account the average output thrust force. FEA verifies the universality of the proposed method,and it can be used in LFSPM machines with different structures to reduce the thrust force ripple while taking into account the average output thrust.

Abstract:As the transformer top oil temperature is affected by many factors such as weather conditions and tidal current loads,it is difficult to improve the forecasting accuracy. To solve this problem,a method of transformer top oil temperature forecasting based on similar day and similar hour is proposed,which is to further select the similar hour corresponding to each hour of the day to be forecast within the similar days,and then use the similar hour to forecast transformer top oil temperature. Firstly,K-means clustering based on meteorological factors and the principle of'near big,far small' are used to select similar days from the historical samples. On the basis of the definition and description of similar hour,the calculation steps of the oil temperature forecasting method are given by using back propagation (BP) neural network and linear weighted method,which is applied to top oil temperature forecasting of a ultra-high voltage main transformer in Jiangsu. Finally,the results show that the proposed method has high accuracy on forecasting top transformer oil temperature,which verifies its feasibility and validity.

Abstract:Generator inertia is an essential parameter in the analysis of frequency characteristics of power system and its online applications. The inertia of a generator can be identified in real time based on ambient active power and frequency signals measured while the generator is in routine operation. However,due to data quality defects of field measurements,the results of inertia identification are poor when applying existing algorithms to actual data. To solve this problem,the a priori variance of inertia identification results is defined based on spectral analysis and system identification theory. The a priori variance is calculated by three steps:reference system estimation,model parameter variance estimation and inertia variance estimation. The segments of ambient data are evaluated and selected before identification,which improves the accuracy of inertia identification. Data evaluation and selection results based on simulation data and field measurements verify the proposed method. The results show that the data segments with smaller a priori variance have higher accuracy of inertia identification.

Abstract:Aiming at the problems of tower inclination,cable fracture caused by geological collapse in goaf,and the existing transmission line sag and temperature monitoring rely too much on sensors,a transmission line sag temperature estimation method based on improved machine learning is proposed. Firstly,the sag temperature image data of the line is obtained by using the intelligent camera and sensor installed on the line. Secondly,the data is transmitted to the supervisory control and data acquisition (SCADA) based on remote wireless communication. The sag of the transmission line is estimated based on genetic support vector machine (GA-SVM) algorithm,while the temperature of the transmission line is estimated by genetic Elman (GA-Elman) neural network algorithm to accurately track the state of the transmission line. Finally,the simulation platform is built to analyze and verify the proposed method. The experimental results show that the proposed method can quickly obtain the monitoring data in complex environment. The accuracy of sag temperature estimation is better than the comparison methods.

Abstract:The regional integrated energy system (RIES) is an effective network with sufficient utilization of multi-energy. Its economic evaluation is important. Aiming at the incomplete economic assessment indexes of the RIES and the index weight aggregation influenced by subjective factors,the structure of the RIES is analyzed,and RIES economic evaluation index system is established. Then,an improved minimum cross-entropy which can reflect the internal relationship between subjective and objective weights is proposed to improve the rationality of index weight integration. The investment schemes for the RIES are sorted and the optimal one is selected by a multi-criteria evaluation ranking method of technique for order preference by similarity to ideal solution (TOPSIS) combined with rank-sum ratio (RSR). Finally,the economic benefit of different system composition schemes of an industrial park is evaluated as an example. The results show the practicability of the proposed method,which can provide the effective economic benefit evaluation for planning and renovation of RIES.

Abstract:The output of wind and solar power stations is intermittent and fluctuating,but their complementarity can be fully realized with reasonable wind-solar capacity ratio. The inaccurate theoretical power calculation of power station affects the extraction of true features of wind and solar,and then leads to large capacity matching error. The model-generator method commonly used in theoretical power calculation of new energy power stations is improved in this study. The abnormal data are firstly identified and reconstructed,and then the abnormal model-generators are identified and updated. Furthermore,according to the actual operation of non-model-generators,the dynamic information window is selected. By using the measured power of model-generator and non-model-generator in the dynamic information window,the non-model-generators are grouped and the scale coefficient of each group of non-model-generator is dynamically identified,and thus the theoretical power of new energy power stations is calculated. Based on the calculation of historical theoretical power for many years,the characteristics of new energy power stations are analyzed. The random output scenario is simulated accordingly,and the optimization method of wind-solar capacity ratio based on the risk of source-load mismatching is established. The accuracy of the improved model-generator method is verified by examples. By using this method,the improved theoretical power data of wind farm and photovoltaic power stations in a certain area of northwest China are obtained,and the optimal ratio of wind-solar capacity in this area is optimized. The improved model machine method proposed in this paper can effectively improve the calculation accuracy of theoretical power of new energy power stations,and the optimal ratio of wind-solar capacity calculated based on this method can provide reference for wind-solar power generation capacity of regional power grid.