Table of Content

05 September 2021, Volume 54 Issue 9

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Site Selection Optimization Strategy for Independent Secondary Device Integrated Center Based on Improved Artificial Bee Colony Algorithm

XIONG Xiaoping, HAO Shaolei, SUN Di, LIN Guangyang, LI Hang

2021, 54(9):  1-8.  DOI: 10.11930/j.issn.1004-9649.202007047

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In view of the high cost of land requisition for urban substations and the increasing demand for power supply reliability of distribution networks, a concept of independent secondary device integrated center (ISDIC) is proposed to realize the compactness requirements of substations and improves the performance of the existing distribution network protection schemes. In order to realize the normal protection function between the center and the substations after change of the protection topology, the site selection for the ISDIC is particularly important, and multiple factors should be considered comprehensively. For this reason, an optimal site selection model is built for the ISDIC by combining the conventional substation site selection schemes and the specific center requirements, which mainly considers such three factors as information delay, resident influence and load distribution. Taking the simple topology of a substation in a city’s urban area as an example, the effectiveness of the model is proved. Firstly, the possible interval of the optimal solution is calculated with the improved artificial bee colony algorithm; and then the ISDIC site node that is most suitable for the center is obtained through precise calculations; and finally the practical engineering significance of the model and the superiority of the method are fully illustrated through analyzing the indexes of the optimal node.

Optimal Power Flow Calculation with Improved Crisscross Optimization Algorithm

ZENG Cong, HUANG Qiang, CHEN De, ZHENG Xiaoying, MENG Anbo

2021, 54(9):  9-16.  DOI: 10.11930/j.issn.1004-9649.202006081

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Crisscross optimization algorithm (CSO) has been applied to solve many complex problems in power system and remarkable results have been achieved. On this basis, a faster crisscross optimization algorithm (FCSO) is proposed to solve the optimal power flow problem. In this algorithm, a new operator—the central crossover operator is proposed based on the original double-crossover operator, which alternates with the crossover operator in a certain pattern; each individual in the population performs a crossover operation with the current optimal individual in turn, and then executes a competition operator to selectively move closer to the global optimal individual, thus improving the quality of each iteration and accelerating convergence. The simulation results in an IEEE-118 bus system show that, compared to other swarm intelligence optimization algorithms, the CSO has the advantage of high convergence accuracy and strong stability, while the FCSO can significantly improve the convergence speed and greatly shorten the consuming time without losing the convergence accuracy, which provides more possibilities for applying the CSO to the real-time control of the power grid.

A Short-Term Load Forecasting Method Based on CNN-BiGRU-NN Model

ZENG Youjun, XIAO Xianyong, XU Fangwei, ZHENG Lin

2021, 54(9):  17-23.  DOI: 10.11930/j.issn.1004-9649.202003035

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In order to fully mine the effective information contained in a large number of collected data and improve the accuracy of short-term load forecasting, a short-term load forecasting method is proposed based on a hybrid model of convolutional neural network (CNN), bidirectional gated recurrent unit (BiGRU), and fully connected neural network (NN). The massive historical load data, meteorological information, and date information are taken to construct feature maps according to time sliding windows. Firstly, the CNN is used to extract valid information from the feature maps to construct feature vectors. And then, by taking the feature vectors as the inputs, the BiGRU-NN network is used to make short-term load forecasting. The load data in the test question A of the Ninth National Electrical Mathematics Modeling Contest held in 2016 are taken as an actual computation example, and the experimental results show that this method has higher accuracy in short-term load forecasting than GRU neural network, DNN neural network, and CNN-LSTM neural network.

Active Disturbance Rejection Vector Control for High-Power Asynchronous Motor to Suppress Measurement Noise

ZHOU Xuesong, WANG Chenglong, MA Youjie, WU Boning

2021, 54(9):  24-33.  DOI: 10.11930/j.issn.1004-9649.202004104

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In the process of asynchronous motor vector control, the motor speed information is obtained through the speed measuring devices. Influenced by such factors as interference, quantization errors, and motor operating conditions, the detection elements gives the speed information mixed with noise that needs to be filtered, but the traditional speed filtering method cannot consider both real-time and precision requirements. The linear extended state observer (LESO) has the function of filtering the output signal of the system. The traditional LESO channel is added with filtering to improve the noise suppression ability, and the observer is upgraded to improve the observation ability, thereby improving the contradiction between the system response speed and controller noise suppression. In the frequency domain, the improved linear active disturbance rejection controller is analyzed through the Bode diagram in terms of stability, tracking and anti-disturbance. The theoretical analysis shows that the improved active disturbance rejection controller can reduce the effects of the noise at the controller input and system feedback. The simulation results have verified the effectiveness of the controller in noise suppression.

Online Monitoring and Early Warning Technology for Conductor Aeolian Vibration Considering Characteristic Transient

ZHAO Long, GUO Yulong, ZHENG Tiantang, CAO Wen

2021, 54(9):  34-44.  DOI: 10.11930/j.issn.1004-9649.202103020

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In view of the errors caused by existing conductor vibration monitoring, which measures the conductor aeolian vibration with the average amplitude and frequency per second, this paper proposes an online monitoring and early warning technology for conductor aeolian vibration considering the transient characteristics of vibration. According to the positive piezoelectric effect of piezoelectric materials, a vibration monitoring sensor is designed to measure the acceleration time history curve of the point 89 mm away from the suspension clamp. In order to obtain the instantaneous amplitude and frequency, the intrinsic mode function (IMF) that conforms to the vibration mechanism of the original signals, is obtained using the empirical mode decomposition (EMD) combined with correlation judgment. The instantaneous parameters are extracted using Hilbert transform (HT), and the damage parameters of each element under dynamic bending stress are calculated using instantaneous amplitude and instantaneous frequency. The effectiveness of the proposed method is validated through numerical analysis. A comparative analysis is conducted with vibrating table test, and the results indicate that within the conductor’s effective damage frequency range of 0~60 Hz, the coincidence degree between the fatigue damage parameters obtained by test and the calculated values is more than 86.77%, and the maximum testing error of the main fatigue damage parameters n_i is 8.02% and the average testing error is 0.92%. The comparative analysis shows that the proposed method could provide an effective warning basis for the fatigue life of vibrating conductors.

On-Line Monitoring of HV Transmission Cables Based on A New Criterion Established with Sheath Current

ZHOU Xin, XIA Xiangyang, XIA Junshan, CHEN Shanqiu, ZHANG Yuliang, YANG Longkai, LUO Yanpeng, WANG Ruiqi, LIU Xiong

2021, 54(9):  45-54,118.  DOI: 10.11930/j.issn.1004-9649.202103052

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In order to timely discover the faults in the high-voltage cable cross-interconnected grounding system, this paper constructs a new criterion based on the ground currents at both ends of the metal sheath of cable to classify and locate the faults of power cables. Firstly, the amplitude and phase of grounding current of metal sheath in direct-grounding boxes at both ends of the main section of cable cross-interconnection are measured; and then a new characteristic quantity is constructed using the amplitude ratio and phase ratio of grounding current at both ends of the same metal sheath circuit and the absolute value of phase difference of grounding current at both ends of different metal sheath circuits; and finally a characteristic quantity matrix corresponding to fault criteria is established to identify the faults based on multi-dimensional characteristic fusion. The common cable faults, such as the open circuit of the cable intermediate joints, the water infiltration into the cross-interconnection grounding box, and the short circuit of the cable intermediate joints, are analyzed, and the feasibility of the new fault criterion is verified by simulation, which can provide a new method for on-line monitoring of high-voltage cable faults.

Evaluation and Improvement of Security and Stability of Jiangsu Receiving-End Power Grid with Hybrid Multi-Infeed DC

HUANG Zhiguang, CAO Lu, LI Jianhua, ZHANG Junli, WANG Guoteng, XU Zheng

2021, 54(9):  55-65.  DOI: 10.11930/j.issn.1004-9649.202007229

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The hybrid infeed DC system usually refers to a hybrid infeed DC system with line commutated converter (LCC) and modular multilevel converter (MMC). At present, the hybrid multi-infeed DC system with multiple DC terminal locations has been adopted in planning of receiving-end power grids, but its impact on the system security and stability is not clear. In order to quantitatively evaluate the security and stability of the receiving-end power grid with hybrid multi-infeed DC, this paper summarizes seven evaluation indexes and proposes an evaluation method. Then, a case study of Jiangsu power grid is carried out, which shows that the security and stability of Jiangsu receiving-end power grid is insufficient, and the most serious problem is the commutation failure of DC system. To solve the existing problems, two schemes are proposed: the scheme 1 is to change the inverter-side LCC of Binchang DC into MMC, and the scheme 2 is to construct a multi-terminal DC system mainly based on MMC. Finally, the application effects of two schemes are evaluated quantitatively, which shows that the security and stability of receiving-end power grid will be improved using MMC and constructing multi terminal DC system, and also proves the effectiveness of the proposed evaluation method.

A Characterization Method for Coupling Relation in Multi-Infeed HVDC System

LEI Xiao, SUN Xu, WANG Weiwei, LIU Lin, LI Xinnian, PANG Guangheng

2021, 54(9):  66-73.  DOI: 10.11930/j.issn.1004-9649.202006134

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At present, many HVDC/UHVDC projects are feeding into the East China Power Grid, and the interaction and coupling between AC and DC systems are complex. In order to characterize the coupling relation of multiple DC systems, an AC voltage distortion coupling coefficient of multi-infeed HVDC (ACDCC)is proposed. By calculating the bus AC voltage distortion of one inverter station caused by other HVDC system’s internal fault, the coupling coefficient of multiple DC systems is obtained, which covers an integrated assessment of such factors as the influence of DC transmission capacity on the AC system, the different response characteristics of HVDC control and protection system with different technical routes, and the AC system impedance characteristics between inverter stations. The concept of coupling area is put forward using coupling coefficient, which can be used to evaluate the simultaneous commutation failure risk of multi-infeed HVDC systems. A simulation verification is carried out on the multi-infeed system of East China Power Grid, and the results show that the proposed coupling coefficient and the characterization of coupling areas are basically consistent with the actual power system conditions. Therefore, the coupling coefficient can provide an important technical reference for the planning and operation of DC systems.

Design Method for the Governor Power System Stabilizer

FANG Risheng, LIN Yaodong, JIANG Wei, HUANG Ting, XU Zhenhua, WU Danyue, CHEN Zhi, SU Yi, LIN Jikeng

2021, 54(9):  74-82.  DOI: 10.11930/j.issn.1004-9649.201909001

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In order to suppress the low frequency oscillation caused by governors, this paper proposes a new design method for the governor power system stabilizer (GPSS), where the requirement of the regulating speed is satisfied. A new GPSS optimization model was developed in the paper. The objective is to maximize the weighted summation of damping ratio margin and the time of the system to reach 90% load as the objective function, and its constraints include speed and stabilization time of primary frequency modulation requirement and stability requirement. A particle swarm optimization (PSO) based algorithm was developed for the optimization model. Simulation results demonstrate the effectiveness and feasibility of the proposed method.

Medium and Long-Term Power Demand Forecasting Based on DE-GWO-SVR

ZHANG Yunhou, LI Wanying, DONG Fugui

2021, 54(9):  83-88.  DOI: 10.11930/j.issn.1004-9649.202105016

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Power demand forecasting is an important prerequisite for the scientific planning and operation of power systems. According to the results of the correlation analysis, the key influencing factors of power demand are selected from eight aspects: economic development level, urbanization level, industrialization level, population size, industrial structure, household consumption level, electricity price and electricity base. Using differential evolution (DE) and grey wolf optimization (GWO) algorithms to optimize the parameters of the support vector regression (SVR), the power demand forecasting model is established. Based on the historical data of power demand in Beijing, this paper makes an empirical analysis, compares the prediction results of different models, verifies the effectiveness of the combined optimization model and the accuracy of prediction, forecasts the power demand of Beijing from 2021 to 2025.

Probabilistic Interval Forecasting of Power Load Based on Structured Load model

PANG Chuanjun, ZHANG Bo, YU Jianming, LIU Yan

2021, 54(9):  89-95.  DOI: 10.11930/j.issn.1004-9649.202007217

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Probability interval forecasting has become one of the main methods for power load forecasting because of the uncertainties of power load. In order to solve the problem that the conventional probability interval forecasting methods cannot consider the impact of the uncertainties of different components on the power load, a structural power load probability interval forecasting method is proposed based on the time-series state space model. Firstly, based on an analysis of the components of power load, models are established respectively for different load components. And then, based on the historical load data, the variational bayesian inference is used to train the posterior probability distribution of model parameters. Finally, the probability distribution of the future power load is predicted based on the trained model, thus realizing the forecasting of the power load probability interval. The proposed method is verified using the real power load data and compared with other methods. The experimental results show that the proposed method has a higher forecasting interval coverage probability and a narrower forecasting interval average width.

Adjustment Factor Model of Relay Protection Equipment Failure Rate Based on Data Fitting

YANG Huping, HUANG Huang, HE Zhiqin, ZHANG Yang, YANG Wensi, ZHOU Rui

2021, 54(9):  96-101.  DOI: 10.11930/j.issn.1004-9649.202103123

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Analyzing the impact of equipment maintenance on the failure rate of relay protection equipment is helpful to the formulation of relay protection equipment maintenance plans and the realization of long-term stable and reliable operation of the power grid. Using the Matlab toolbox to fit the failure rate function of the segmented data based on the failure data of the relay protection device in a certain area. Then the genetic algorithm is used to fit the failure rate adjustment factor, a failure rate adjustment factor model based on data fitting is established. Finally, the model in paper and the model based on the Delphi method were evaluated based on equipment failure data in multiple regions. Research indicates: The failure rate adjustment factor model based on the Delphi method underestimates the ability of maintenance to reduce the failure rate of equipment. The model in the paper has a smaller cumulative residual error than the model based on the Delphi method. It can more accurately reflect the impact of maintenance on the failure rate of relay protection equipment.

Implementation Scheme of Preferential Generation in Market-oriented Environment

HU Yuou, GAO Zhiyuan, ZHANG Jing, ZHANG Tao

2021, 54(9):  102-108.  DOI: 10.11930/j.issn.1004-9649.202009102

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The preferential power generation system is an important guarantee to implement the national strategies, but there are still many challenges in its implementation in the process of electricity market reform. Based on the analysis of the relevant policies, the main problems under electricity market environment are analyzed, the relevant market-oriented implementation modes are discussed, and an implementation scheme for preferential generation in the market-oriented environment is proposed. It is concluded that: according to current relevant policies, the preferential power generation system mainly includes five types of power generation, but in actual practices, many problems are faced such as the imbalance of power generation and consumption, the imbalance of revenue and expenditure and the occupation of market trading space, so the market-oriented implementation needs a systematic market mechanism composed of multiple market types, trading varieties, deviations and settlement mechanisms; under current policy and market environment, we propose a basic implementation scheme, which is composed of six main steps, including determination of differential power plan, implementation of market-oriented implementation, and so on, and at the same time an allocation method for differentiated electricity plan is also designed. The proposed scheme has good adaptability for development of electricity market, and has been applied in Beijing-Tianjin-Tangshan power grid.

Prediction and Analysis of Transient Electric Field in DC Yard of Flexible Converter Station Under Short-Circuit Conditions

WU Sihang, SHEN Hong, QI Lei, QIU Peng, KUAI Zhaoxia

2021, 54(9):  109-118.  DOI: 10.11930/j.issn.1004-9649.201912137

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In the case of short-circuit fault, the flexible DC converter station would produce transient yet strong electromagnetic field, which would impact on the secondary equipment in the converter station. In this paper, the problem of electric field disturbance at the secondary equipment in the short circuit test of Dinghai converter station was studied systematically. The potential of the key nodes in the DC field was analyzed, and 3D model of the equipment in the DC field was established. Considering the time-varying topological structure of the DC circuit breaker, the potential function of each node in the DC field was taken as the first boundary condition of the electric quasi-static field solution area, and the electric field distribution of the secondary equipment around the DC circuit breaker under three kinds of short-circuit conditions was calculated accordingly. The following facts were revealed by the simulation results: the maximum electric field strength is 33 kV/m; the maximum rise and fall edge is 40 μs; the electric field strength could be determined by the spatial layout and voltage amplitude; and the electric field strength waveform would be consistent with the rise and fall edge of the voltage waveform.

Operation Condition and Performance Test Analysis of Distributed Energy Storage Battery

DU Xuhao, LI Bingyu, MIAO Junjie, GUO Xiaofan

2021, 54(9):  119-124.  DOI: 10.11930/j.issn.1004-9649.202104065

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Energy storage system operating conditions and battery performance are the focus of energy storage technology research. Based on actual operating curve of the energy storage battery in the wind farm tracking planned output mode, a method of reconstruction of the energy storage battery operating condition based on the factor analysis method and the cluster analysis method was proposed. This paper deeply studied the state of charge (SOC) of energy storage battery, and proposed an estimation algorithm based on (extended kalman particle filter，EKPF) as the detection method. The analysis results showed that the factor analysis method and cluster analysis method could effectively identify the characteristic parameter vector and construct the operating conditions of the energy storage battery. The proposed EKPF algorithm could also correctly estimate the state of charge of the energy storage battery. The research provided a certain reference for the construction of energy storage battery operating conditions and the performance test of energy storage battery.

Monthly Electricity Consumption Characteristics of Industries in Guangzhou and Optimized Electricity Management Based on Geographical Detector

ZHANG Yuntao, CAI Guotian, KE Shangjun, WANG Wenxiu

2021, 54(9):  125-134.  DOI: 10.11930/j.issn.1004-9649.202004118

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To implement demand-side management (DSM) to specific industries, this paper analyzed electricity consumption characteristics of each industry within 60 months from 2013 to 2017, depending on the geographical detector and the electricity consumption complementarity model. On this basis, it explored the optimal management path of industry electricity consumption from the perspective of industry and time through scenario analysis. In light of the monthly electricity consumption characteristics of different industries in Guangzhou, the main driving sub-industries for electricity consumption in the industry were identified, and the electricity consumption combinations that can offset the fluctuation in electricity consumption were employed. The research finds that optimizing the industrial electricity consumption structure and upgrading the consumption time management considering the electricity consumption level of Guangzhou in 2017 can reduce the monthly peak–valley difference of Guangzhou electricity consumption by about 225 million kW·h. In the future, the monthly electricity consumption forecast of the industry, combined with the analysis of electricity complementarity, can be used to calculate the industry’s electricity dispatching potential, so as to provide data support for the improvement in demand-side management of electricity.

Influence Analysis of Virtual Impedance on the Stability of Parallel System of Inverters with Different Voltage Levels

MA Wentao, WANG Jinmei, WANG Yongqi

2021, 54(9):  135-142,175.  DOI: 10.11930/j.issn.1004-9649.202004204

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Using virtual impedance technology to optimize the double closed-loop control structure can improve the equivalent output impedance of the inverter to be inductive and enhance the accuracy of power distribution by traditional inductive droop control strategies in low-voltage micro-grids, thus inhibiting circulating current. This approach, however, tends to overlook the impact of virtual impedance on system stability. In this regard, the transfer function of a three-loop control structure is derived, which includes virtual impedance, line impedance and common point voltage. A parallel model of inverters with different voltage levels is built, considering virtual complex impedance, and the model is simplified with the Thevenin’s equivalent. According to the Nyquist stability criterion, the effect of virtual impedance on system stability is analyzed under various operating conditions. The results show that the multi-inverter parallel system can maintain stable operation after the virtual impedance is added.

Analyzing Method of the Absorption Capability of New Energy in Distribution Network with Consideration of Regional Self-discipline and Absorption Quality

CHEN Yan, JIN Wei, WANG Wenbin, LI Huibin, HAN Shengfeng, JIA Kai

2021, 54(9):  143-155.  DOI: 10.11930/j.issn.1004-9649.202004213

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This paper proposed a transmission-distribution coordinated absorption strategy in which the new energy distribution network applied controllable resources to regional self-discipline control, and studied a method for analyzing the reasonable absorption capability of new energy satisfying regional self-discipline characteristics and absorption quality with the given distribution resources. The goal is to handle the situation that the random uncertainty of new energy power generation leads to serious power disturbance of the distribution network to the main network and improve the multi-level orderly absorption capability of new energy in the power system. Firstly, the strategy for implementing the self-discipline operation of the distribution network was unveiled, and the performance indices of self-discipline operation capability were created. Then, the optimal allocation model for the new energy absorption capability of the distribution network was constructed, and the operation behavior model of the distribution network satisfying self-discipline constraints was built based on energy storage, flexible load, and network reconstruction, and solved by the genetic algorithm. The evaluation indices of new energy absorption capability considering absorption quality were proposed and the comprehensive performance of the allocation scheme was assessed by the annual time series simulation. Finally, an economic and technological development zone in Hebei Province was taken as an example for analysis to verify the effectiveness and rationality of the proposed method.

Energy Purchasing Strategy of Electricity Retailer Considering the Responsibility of Renewable Energy Consumption

DAI Shangwen, ZHANG Li, LIU Ningning, YANG Ming, LIU Chang, CAO Shengnan

2021, 54(9):  156-164.  DOI: 10.11930/j.issn.1004-9649.202005112

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As one of the major players in electricity trading, the electricity retailer should actively undertake the responsibility of consuming renewable energy. To analyze the influence of the renewable portfolio standard (RPS) on electricity retailers, this paper constructed a new portfolio investment model of energy purchasing. Scenario analysis is performed to describe the uncertainty about the spot price and renewable energy output in electricity markets. The optimal energy purchasing strategy is developed with the minimum transaction cost based on the conditional value-at-risk (CVaR) as the goal, and the punishment mechanism for consumption responsibility examination is introduced to evaluate different examination criteria. The YALMIP toolbox in MATLAB is adopted to solve linear programming in this model. In addition, the influence of risk preference, RPS quotas, renewable-energy forecast accuracy, and the degrees of penalties from regulatory authorities on the optimal energy purchasing strategy of electricity retailers is analyzed by simulation. The results show that the proposed model is effective.

Research and Application of Multi-Area Large-Scale New Energy Integration Capability with Steady-State Security Region Constraints

SU Yiqiang, LIU Shengsong

2021, 54(9):  165-175.  DOI: 10.11930/j.issn.1004-9649.202006038

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With the rapid increase in the installed capacities of wind power and PV power in China, large-scale new energy integration has received wide attention. An evaluation method for multi-area large-scale new energy integration capability is proposed in this paper. The steady-state security region (SSSR) of a power system is defined in the multi-area new energy power injection space. According to the regional and resource characteristics of the large-scale new energy station access, a group of power growth directions is defined for each region, and a mathematical optimization model of new energy integration capability is built in one-dimension space. The optimal power flow traverses the new energy power growth directions of the whole system composed of different regions to search for the critical points of SSSR. Based on these critical points, a hyperplane is constructed to approximate the SSSR boundary of multi-area new energy power injection space, so as to evaluate the multi-area large-scale new energy integration capability in multi-dimensional space. Numerical results of a provincial 1975-bus system are presented, proving that the proposed model is practical and effective.

Optimal Design Method of Integrated Energy Systems Considering Staged Planning and Equipment Replacement

ZOU Lei, TANG Yiming, LIU Zhuping, WU Zhengyong, FANG Chao, WANG Chaoqun, WEN Fushuan

2021, 54(9):  176-186.  DOI: 10.11930/j.issn.1004-9649.202007091

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As an important physical carrier of energy internet, an integrated energy system is of great significance for improving regional comprehensive energy efficiency, ensuring energy safety and realizing energy conservation and emission reduction. In this paper, a staged collaborative planning model of the park-type integrated energy system is built on the basis of the whole life cycle. Firstly, regarding the continuation of equipment installation capacity, the equipment is divided into discrete and continuous groups, and their configuration and operation constraints are refined and unified respectively. Then, with the whole project cycle as the optimization time scale, the relationship between the equipment installation year and the current remaining life is modeled by introducing the equipment selection and operation decision variables. Finally, considering the influence of economic factors such as nominal interest rates and inflation rates, an objective function, involving investment costs, operating costs, and equipment residual value income, is constructed, with the optimal economical performance as the goal. The mixed integer linear programming technique is used to solve the model. The test results of the four scenarios show that the staged collaborative planning considering equipment replacement can cut the equipment investment by 14.76% compared to the traditional single-stage planning. After the introduction of heat storage devices and heat abandonment constraints, the operating cost of the thermoelectric coupled system can be further reduced by 11.78%.

Research on Economic Allocation of User-Side Energy Storage Capacity Based on Risk-Benefit Analysis

ZHOU Lili, XIANG Yue, CHEN Lingtian

2021, 54(9):  187-197.  DOI: 10.11930/j.issn.1004-9649.202007136

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In view of the optimal configuration of user-side energy storage (ES) capacity, by taking full account of the application markets that ES may participate and gain profits from as well as the potential risks that may be incurred, a two-stage optimal economic configuration model of ES based on portfolio theory was established. In the first stage, the optimization of the benefit and risk with ES applications are set as objective, and by taking advantage of the portfolio theory the optimal capacity allocation during each time period of ES is determined in different markets. In the second stage, the maximization of net profit of ES is taken as objective, which was calculated in terms of the full life cycle cost and operating benefit throughout the actual operating life cycle of ES. The comparison and analysis results of various scenarios show that the proposed model has effectively reduced the risks encountered in ES applications while ensuring the benefit of economic energy storage configuration. Hence it can provide certain reference for the optimal economic capacity configuration and operation for user-side ES.

Performance Analysis of Low Temperature Waste Heat Power Generation Cycle with Single Working Fluid

GENG Zhi, LIU Enshuai, XU Xipu, GU Yujiong, WEN Zhenhua, LI Renfeng

2021, 54(9):  198-207.  DOI: 10.11930/j.issn.1004-9649.202007105

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In order to improve the efficiency and economy of energy utilization, promote the application of the organic Rankine cycle system in the field of low-temperature waste heat power generation. In this paper, by establishing a thermodynamic model and programming with MATLAB software, calling the NIST Refprop database, selecting hexafluoropropane as the circulating working fluid, and simulating and analyzing various aspects of the organic Rankine cycle system performance. Based on the use of thermodynamic indicators such as cycle output power, exergy efficiency and thermal efficiency to study the thermal performance of the system, the heat exchange area and the annual CO₂ emission reduction were used as indicators to evaluate the economic performance and environmental performance of the system. The research results show that: when the condensing pressure is 150 kPa, the system performance can be ensured to achieve the best performance when the single variable is used. In the case of multiple variables, the increase of the heat source temperature will greatly reduce the economic performance, and effectively improve the thermal performance and environmental performance of the system. Comprehensively consider the temperature of the heat source to be 155 ℃~185 ℃; when the performance of the system is guaranteed to be the best, The evaporation pressure changes in different forms with the temperature of the heat source, but it never exceeds 3350 kPa.

Design and Application of Main Control System for 2 MW Direct-Driven Permanent Magnet Wind Turbine

WANG Ben, NIU Honghai, XU Weifeng, CHEN Jun

2021, 54(9):  208-220.  DOI: 10.11930/j.issn.1004-9649.202006082

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The main control system is the core component of a large-scale wind turbine. This paper presents a main control system based on PLC, aiming to realize safe and stable operation for a 2 MW direct-driven permanent magnet wind turbine under unattended operation. The graded alarms based on the state code and the automatic start-up and shut-down system (APS) based on the state machine are introduced. An approach of event snapshot based on the ring buffer with sliding window scrolling update is designed to enhance the system analysis capabilities after incidents. A real-time simulation support platform is built on the basis of GH Bladed software to verify the torque–pitch joint control strategy. The software and hardware architectures are both expounded, and the overall development of the controller logic configuration was completed with Bachmann M-PLC software. The main control system has been successfully applied to a wind farm in Shandong Province, realizing unattended operation. The measured data of the wind turbine in a project site shows that the main control system is safe and stable and the control strategy is effective, providing a reference for the design and development of the main control system in similar wind turbines.