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Both poor cooling methods and complex heat dissipation lead to prominent asymmetry in transformer temperature distribution. Both the operating life and load capacity of a power transformer are closely related to the winding hotspot temperature. Realizing accurate prediction of the hotspot temperature of transformer windings is the key to effectively preventing thermal faults in transformers, thus ensuring the reliable operation of transformers and accurately predicting transformer operating lifetimes. In this paper, a hot spot temperature prediction method is proposed based on the transformer operating parameters through the particle filter optimization support vector regression model. Based on the monitored transformer temperature, load rate, transformer cooling type, and ambient temperature, the hotspot temperature of a dry-type transformer can be predicted by a support vector regression method. The hyperparameters of the support vector regression are dynamically optimized here according to the particle filter to improve the optimization accuracy. The validity and accuracy of the proposed method are verified by comparing the proposed method with a traditional support vector regression method based on the real operating data of a 35 kV dry-type transformer.
Yuanyuan Sun; Gongde Xu; Na Li; Kejun Li; Yongliang Liang; Hui Zhong; Lina Zhang; Ping Liu. Hotspot Temperature Prediction of Dry-Type Transformers Based on Particle Filter Optimization with Support Vector Regression. Symmetry 2021, 13, 1320 .
AMA StyleYuanyuan Sun, Gongde Xu, Na Li, Kejun Li, Yongliang Liang, Hui Zhong, Lina Zhang, Ping Liu. Hotspot Temperature Prediction of Dry-Type Transformers Based on Particle Filter Optimization with Support Vector Regression. Symmetry. 2021; 13 (8):1320.
Chicago/Turabian StyleYuanyuan Sun; Gongde Xu; Na Li; Kejun Li; Yongliang Liang; Hui Zhong; Lina Zhang; Ping Liu. 2021. "Hotspot Temperature Prediction of Dry-Type Transformers Based on Particle Filter Optimization with Support Vector Regression." Symmetry 13, no. 8: 1320.
Compressed natural gas has been proven to be more advantageous than gasoline and diesel in terms of emission cleanliness and equipment wear. The replacement of gasoline and diesel by CNG can be accelerated through the economic scheduling of CNG fueling stations. Due to the highly electrified equipment in the station, electricity cost is an important part of CNG operation costs. The critical peak pricing mechanism being implemented by the grid company provides opportunities for the economic scheduling of CNG fueling stations. This paper presents an improved operation model for a CNG main station, which considers the pre-system for the first time, including the dehydration device and buffer tank. Then, considering critical peak pricing, an economic scheduling model for the CNG main station is proposed. This optimal scheduling model is searched by an improved multi-population genetic algorithm combined with the elite retention strategy and repair operator. The results show that the electricity operating costs were effectively reduced by 34.62%, and the switching frequency of the compressor was decreased by 62.50%.
Yong-Liang Liang; Chen-Xian Guo; Ke-Jun Li; Ming-Yang Li. Economic scheduling of compressed natural gas main station considering critical peak pricing. Applied Energy 2021, 292, 116937 .
AMA StyleYong-Liang Liang, Chen-Xian Guo, Ke-Jun Li, Ming-Yang Li. Economic scheduling of compressed natural gas main station considering critical peak pricing. Applied Energy. 2021; 292 ():116937.
Chicago/Turabian StyleYong-Liang Liang; Chen-Xian Guo; Ke-Jun Li; Ming-Yang Li. 2021. "Economic scheduling of compressed natural gas main station considering critical peak pricing." Applied Energy 292, no. : 116937.
The coastal urban multi-terminal DC (CU-MTDC) is a prospective solution for enhancing the power supply security of the coastal urban power (CUP) grid and integrating the large-scale offshore wind farm. However, the large DC disturbances may significantly impact the CUP power supply security. The existing DC unbalanced power distribution methods are difficult to be applied in the CU-MTDC because of the complicated optimization process and the expansion of the influence range of a DC fault. To solve the above problems, this paper proposes a coordinated control strategy of CU-MTDC under abnormal conditions. First, calculation principles for the active power reference of center coastal urban power (CCUP) grid converters are proposed. Second, a DC unbalanced power coordinated distribution strategy under abnormal conditions is used based on the dynamic priority control to ensure power supply security of the critical AC lines. Third, the controller parameters of CCUP grid converters are calculated. Through a simple control process, the number of the regulation converters is dynamically scheduled according to the DC unbalanced power. The DC fault influence range on the urban power grid can be limited in a sufficiently small area. Simulation verified the effectiveness of the proposed control strategy.
Zhuodi Wang; Kejun Li; Jun Liang; Kaiqi Sun; Jinyu Wang; Zhijie Liu. Coordinated Control Strategy of CU-MTDC under Abnormal Conditions Considering Power Supply Security. Applied Sciences 2021, 11, 1539 .
AMA StyleZhuodi Wang, Kejun Li, Jun Liang, Kaiqi Sun, Jinyu Wang, Zhijie Liu. Coordinated Control Strategy of CU-MTDC under Abnormal Conditions Considering Power Supply Security. Applied Sciences. 2021; 11 (4):1539.
Chicago/Turabian StyleZhuodi Wang; Kejun Li; Jun Liang; Kaiqi Sun; Jinyu Wang; Zhijie Liu. 2021. "Coordinated Control Strategy of CU-MTDC under Abnormal Conditions Considering Power Supply Security." Applied Sciences 11, no. 4: 1539.
In this paper, a model is proposed for the optimal operation of multi-energy microgrids (MEMGs) in the presence of solar photovoltaics (PV), heterogeneous energy storage (HES) and integrated demand response (IDR), considering technical and economic ties among the resources. Uncertainty of solar power as well as the flexibility of electrical, cooling and heat load demand are taken into account. A p-efficient point method is applied to compute PV power at different confidence levels based on historical data. This method converts the uncertain PV energy from stochastic to deterministic to be included in the optimization model. The concept of demand response is extended and mathematically modeled using a linear function based on the quantized flexibility interval of multi-energy load demand. As a result, the overall model is formulated as a mixed-integer linear program, which can be effectively solved by the commercial solvers. The proposed model is implemented on two typical summer and winter days for various cases. Results of case studies show the important benefits for maximum PV utilization, energy efficiency and economic system operation. Moreover, the influence of the different confidence levels of PV power and effectiveness of IDR in the stochastic circumstances are addressed in the optimization-based operation.
Jingshan Wang; Ke-Jun Li; Yongliang Liang; Zahid Javid. Optimization of Multi-Energy Microgrid Operation in the Presence of PV, Heterogeneous Energy Storage and Integrated Demand Response. Applied Sciences 2021, 11, 1005 .
AMA StyleJingshan Wang, Ke-Jun Li, Yongliang Liang, Zahid Javid. Optimization of Multi-Energy Microgrid Operation in the Presence of PV, Heterogeneous Energy Storage and Integrated Demand Response. Applied Sciences. 2021; 11 (3):1005.
Chicago/Turabian StyleJingshan Wang; Ke-Jun Li; Yongliang Liang; Zahid Javid. 2021. "Optimization of Multi-Energy Microgrid Operation in the Presence of PV, Heterogeneous Energy Storage and Integrated Demand Response." Applied Sciences 11, no. 3: 1005.
In non-solidly earthed distribution networks, single-phase-to-ground faults (SPGFs) significantly threaten the safety of people and equipment. Although selection and location techniques for the existing fault lines have made remarkable contributions in reducing the damage due to SPGFs, a certain amount of power loss still exists in the SPGF owing to its low efficiency in detection and maintenance. Multiple-dimension classification of the SPGF may help reveal the nature of the fault from different perspectives; therefore, in this study, a multi-label classification model for recognizing types of SPGF is proposed. In the proposed model, the SPGF is classified considering five dimensions, namely time-domain continuity, time-domain stability, volt-ampere characteristics of transition impedance, transition impedance size, and fault point medium. Subsequently, the corresponding features are determined. In addition, a multi-label classification model of the SPGF is constructed with an 8-dimensional feature space and a 14-label fault-type space. Finally, a k-nearest neighbors Bayesian method is designed to solve the multi-label classification problem. The feasibility and advantages of the proposed model and methods are verified using field data and through comparison with the KNN method.
Yongliang Liang; Ke-Jun Li; Zhao Ma; Wei-Jen Lee. Multilabel Classification Model for Type Recognition of Single-Phase-to-Ground Fault Based on KNN-Bayesian Method. IEEE Transactions on Industry Applications 2021, 57, 1294 -1302.
AMA StyleYongliang Liang, Ke-Jun Li, Zhao Ma, Wei-Jen Lee. Multilabel Classification Model for Type Recognition of Single-Phase-to-Ground Fault Based on KNN-Bayesian Method. IEEE Transactions on Industry Applications. 2021; 57 (2):1294-1302.
Chicago/Turabian StyleYongliang Liang; Ke-Jun Li; Zhao Ma; Wei-Jen Lee. 2021. "Multilabel Classification Model for Type Recognition of Single-Phase-to-Ground Fault Based on KNN-Bayesian Method." IEEE Transactions on Industry Applications 57, no. 2: 1294-1302.
In recent years, VSC-HVDC has been widely used in windfarm integration owing to its ability of connecting the weak AC system. And the hybrid modular multilevel converter based HVDC(MMC-HVDC) has attracted more attention because of its DC fault blocking capability. However, most of the researches about MMC-HVDC connected to windfarm are focused on frequency response and wind farm fault ride through, without assisting AC system to maintain the voltage via the converter's reactive power control capacity. Based on this, this paper proposes a mode switch control and reactive power support control scheme for the grid connected inverter connected to windfarms. The switch mode control scheme provides three operation modes for MMC to adapt to different operation situations. The reactive power support coordination control scheme is an advanced control scheme for cooperating converter, unloading resistor and wind farm. With the cooperating control, the PCC voltage sag due to the fault is alleviated while reducing the impact of grid failures on the wind farm. Finally, the presented control strategy is simulated in PSCAD/ EMTDC, which verifies the effectiveness of the scheme proposed.
Jin Zhang; Ke-Jun Li; Wentao Liu; Kaiqi Sun; Zhijie Liu; Zhuo-Di Wang. Grid side reactive power support strategy for MMC-HVDC connected to the wind farms based on unloading resistor. Electric Power Systems Research 2020, 193, 107010 .
AMA StyleJin Zhang, Ke-Jun Li, Wentao Liu, Kaiqi Sun, Zhijie Liu, Zhuo-Di Wang. Grid side reactive power support strategy for MMC-HVDC connected to the wind farms based on unloading resistor. Electric Power Systems Research. 2020; 193 ():107010.
Chicago/Turabian StyleJin Zhang; Ke-Jun Li; Wentao Liu; Kaiqi Sun; Zhijie Liu; Zhuo-Di Wang. 2020. "Grid side reactive power support strategy for MMC-HVDC connected to the wind farms based on unloading resistor." Electric Power Systems Research 193, no. : 107010.
The Single-phase-to-ground fault (SPGF) affects reliability and security of distribution system greatly. Accurate online recognition of fault causes can help improve the efficiency of weak components finding and maintenance. In this paper, various symptom features of the SPGF by typical causes are analyzed and a fuzzy inference system (FIS) for fault cause recognition is established for overhead lines in non-solidly earthed distribution networks. Based on the survey of fault causes in a certain city in China, artificial grounding experiments are designed for six typical fault causes, including arrester breakdown, insulator flashover, line-to-crossbar discharge, line fallen on wet mud, line fallen on wet sand, and line fallen into pond for waveform data collection. Through multiple time-frequency analysis on waveform data of various causes, five features are extracted and the statistical results are obtained, including self-recoverability, zero current time, transition time, degree of distortion, and randomness. Based on above, a FIS for cause recognition for SPGFs is established. The experimental results and the comparison with BPNN model show that the proposed method has good performance and feasibility.
Yong-Liang Liang; Ke-Jun Li; Zhao Ma; Wei-Jen Lee. Typical Fault Cause Recognition of Single-Phase-to-Ground Fault for Overhead Lines in Nonsolidly Earthed Distribution Networks. IEEE Transactions on Industry Applications 2020, 56, 6298 -6306.
AMA StyleYong-Liang Liang, Ke-Jun Li, Zhao Ma, Wei-Jen Lee. Typical Fault Cause Recognition of Single-Phase-to-Ground Fault for Overhead Lines in Nonsolidly Earthed Distribution Networks. IEEE Transactions on Industry Applications. 2020; 56 (6):6298-6306.
Chicago/Turabian StyleYong-Liang Liang; Ke-Jun Li; Zhao Ma; Wei-Jen Lee. 2020. "Typical Fault Cause Recognition of Single-Phase-to-Ground Fault for Overhead Lines in Nonsolidly Earthed Distribution Networks." IEEE Transactions on Industry Applications 56, no. 6: 6298-6306.
Background: With the increasing development of voltage source converter based high voltage direct current (HVDC), it will become a reality to interconnect different DC networks into DC grid with DC-DC converters. Methods: In this paper, three operation scenarios for the DC grid with DC-DC converters are proposed, by which the DC networks can reinforce each other with relative independence. In order to achieve the flexible switching of the proposed scenarios, the DC-DC combined control and principle of parameter selection are presented. In addition, two coordination controls for different scenarios are given to optimize the distribution of unbalanced power when the disturbances occur in the grid. With the proposed scenarios and control strategy, the impacts caused by the disturbances are alleviated and the uninterrupted operation of the grid is guaranteed. Results: A simulation model is established on the PSCAD/EMTDC and the simulation results verify the effectiveness of the proposed operation scenarios and control strategy. Conclusion: Finally, the effectiveness of the proposed operation scenarios and control strategy is verified by the simulation results in PSCAD/EMTDC.
Meiyan Wang; Ke-Jun Li; Kaiqi Sun; Zhijie Liu. Operation Scenario and Coordination Control of DC Grid with DC-DC Converters. Recent Advances in Electrical & Electronic Engineering (Formerly Recent Patents on Electrical & Electronic Engineering) 2020, 13, 369 -377.
AMA StyleMeiyan Wang, Ke-Jun Li, Kaiqi Sun, Zhijie Liu. Operation Scenario and Coordination Control of DC Grid with DC-DC Converters. Recent Advances in Electrical & Electronic Engineering (Formerly Recent Patents on Electrical & Electronic Engineering). 2020; 13 (3):369-377.
Chicago/Turabian StyleMeiyan Wang; Ke-Jun Li; Kaiqi Sun; Zhijie Liu. 2020. "Operation Scenario and Coordination Control of DC Grid with DC-DC Converters." Recent Advances in Electrical & Electronic Engineering (Formerly Recent Patents on Electrical & Electronic Engineering) 13, no. 3: 369-377.
The steady-state performance of modular multilevel converter (MMC) can be optimized by the following methods: circulating current injection, third-harmonic signal injection, and average capacitor voltage control. However, most of the papers, due to the deficiencies of their MMC models, are limited to the study of just adopting one method and only optimizing a single-aspect performance. Thus, this paper proposes a general MMC model for the comprehensive study of the steady-state performance optimization. The general model is built based on an equilibrium equation between the internal quantities and the external quantities of the MMC. This general model is capable of analyzing the optimization where the optimizing methods are used in combination to improve the multi-aspect performance of the MMC. In addition, more influence factors are taken into account; hence the calculation error can be smaller than 1% and even the minor effect of each optimizing method can be reflected. The proposed model is compared with traditional models; and it is found that both dc and fundamental components in modulation signals will be affected by the injected circulating current, rather than constant values in the traditional models. Finally, the proposed MMC model is verified by both simulation and experiment.
Zhijie Liu; Ke-Jun Li; Jinyu Wang; Wentao Liu; Zahid Javid; Zhuo-Di Wang. General Model of Modular Multilevel Converter for Analyzing the Steady-State Performance Optimization. IEEE Transactions on Industrial Electronics 2020, 68, 925 -937.
AMA StyleZhijie Liu, Ke-Jun Li, Jinyu Wang, Wentao Liu, Zahid Javid, Zhuo-Di Wang. General Model of Modular Multilevel Converter for Analyzing the Steady-State Performance Optimization. IEEE Transactions on Industrial Electronics. 2020; 68 (2):925-937.
Chicago/Turabian StyleZhijie Liu; Ke-Jun Li; Jinyu Wang; Wentao Liu; Zahid Javid; Zhuo-Di Wang. 2020. "General Model of Modular Multilevel Converter for Analyzing the Steady-State Performance Optimization." IEEE Transactions on Industrial Electronics 68, no. 2: 925-937.
Modular multilevel converter (MMC) has been widely concerned due to its inherent excellent performance in recent years. However, in practical engineering, one of the technical challenges of MMC operation control is how to complete the submodule (SM) capacitors precharging safely and effectively, and reduce the impact of overcurrent phenomenon on the converter during the start -up process. In this paper, a simple and novel precharging control strategy is proposed. It can precharging all SMs of the converter at the same time, without the need for capacitor voltage balance algorithm, extra measurements and additional power supplies. It takes advantage of the symmetry of the grid voltage and the structural characteristics of MMC to form boost circuits between the arms by specific switching operations. Furthermore, the proposed method is not limited by the SM topology. The most commonly used SM topologies can also be converted into boost circuits and have the similar precharging process. By selecting appropriate control parameters, the precharging speed and efficiency of the converter can be improved. The effectiveness of the proposed control strategy is verified by simulations and experiments.
Wentao Liu; Ke-Jun Li; Zhijie Liu; Meiyan Wang. A Simple and Novel Precharging Control Strategy for Modular Multilevel Converter. IEEE Access 2019, 7, 170500 -170512.
AMA StyleWentao Liu, Ke-Jun Li, Zhijie Liu, Meiyan Wang. A Simple and Novel Precharging Control Strategy for Modular Multilevel Converter. IEEE Access. 2019; 7 (99):170500-170512.
Chicago/Turabian StyleWentao Liu; Ke-Jun Li; Zhijie Liu; Meiyan Wang. 2019. "A Simple and Novel Precharging Control Strategy for Modular Multilevel Converter." IEEE Access 7, no. 99: 170500-170512.
Dc–dc converters are emerging as a key device for future dc transmission networks. This paper develops a switch mode control and a dc–dc coordination control for dc–dc converters’ coordinated operation in the multi-voltage-level dc grid. The switch mode control is a local controller on the dc–dc converter to enable the automatic switch of the dc–dc operation mode. The dc–dc coordination control is an advanced control based on the switch mode control. With the dc–dc coordination control, unbalanced power from one dc grid could be optimally distributed to other grids, in order to avoid serious power fluctuation events. Simulation results are provided to demonstrate the performance of the switch mode control and dc–dc coordination control.
Kaiqi Sun; Ke-Jun Li; Meiyan Wang; Guanyu Tian; Zhuo-Di Wang; Zhijie Liu. Coordination control for multi-voltage-level dc grid based on the dc–dc converters. Electric Power Systems Research 2019, 178, 106050 .
AMA StyleKaiqi Sun, Ke-Jun Li, Meiyan Wang, Guanyu Tian, Zhuo-Di Wang, Zhijie Liu. Coordination control for multi-voltage-level dc grid based on the dc–dc converters. Electric Power Systems Research. 2019; 178 ():106050.
Chicago/Turabian StyleKaiqi Sun; Ke-Jun Li; Meiyan Wang; Guanyu Tian; Zhuo-Di Wang; Zhijie Liu. 2019. "Coordination control for multi-voltage-level dc grid based on the dc–dc converters." Electric Power Systems Research 178, no. : 106050.
With the increasing integration of rooftop photovoltaic (PV) generation and plug-in electric vehicles (EVs) into the households at user level, household consumers become prosumers. The coordination between the household prosumers and distribution network (DN) becomes essential to the energy management and optimal operation for both entities. In this paper, the residential prosumer cluster is considered as a residential microgrid (RMG) and a hierarchical DN integration method for the multi-RMGs is presented. A two-level hierarchical distributed optimization model is established based on the analytical target cascading to coordinate the RMGs and DNs. At the RMGs level, each RMG is required to individually optimize the energy consumption scheduling in every household by taking into account the effect of time-of-use electricity price on the demand response of EVs and flexible loads. At the DN level, the optimally coordinated operation problem is formulated as a relaxed optimal power flow model based on the second order cone programming by considering the power flow balance constraints. Case studies on the modified IEEE 33-bus system demonstrate the feasibility and effectiveness of the proposed method by achieving coordinated economic optimality as well as coordinated operating points for all entities.
Jingshan Wang; Ke-Jun Li; Zahid Javid; Yuanyuan Sun. Distributed Optimal Coordinated Operation for Distribution System with the Integration of Residential Microgrids. Applied Sciences 2019, 9, 2136 .
AMA StyleJingshan Wang, Ke-Jun Li, Zahid Javid, Yuanyuan Sun. Distributed Optimal Coordinated Operation for Distribution System with the Integration of Residential Microgrids. Applied Sciences. 2019; 9 (10):2136.
Chicago/Turabian StyleJingshan Wang; Ke-Jun Li; Zahid Javid; Yuanyuan Sun. 2019. "Distributed Optimal Coordinated Operation for Distribution System with the Integration of Residential Microgrids." Applied Sciences 9, no. 10: 2136.
Because of the steady increase of wind and solar capacity installations in recent years, the goal of the Paris Agreement is expected to be reached. However, due to the intermittent characteristics of renewable generation, challenges are presented for the power grid to operate reliably and economically under the high uncertainty of wind and solar power productions. Sufficient responsive reserves must be available for the power grid to maintain the balance between the supply and demand. To be fair to the market participants, the renewable generation companies should pay for the received grid ancillary services. In this paper, an optimal combined operation scheme is proposed for pumped storage hydro and hybrid wind-photovoltaic complementary power generation system interconnected by a Voltage Source Converter-based multi-terminal HVDC system. The optimal combined operation scheme has two real-time control functions. The pumped storage hydro control function enables automatic dispatch of the pumped storage hydro to effectively suppress or compensate for the output deviations of wind and solar generation from the forecasted production; and the output control function is able to distribute the non-compensated production surplus or deficit to different ac systems based on the market regulating service prices. A Case study is provided to demonstrate the improved power generation profile and reduced revenue losses of the pumped storage hydro and hybrid wind-photovoltaic complementary power generation system.
Kaiqi Sun; Ke-Jun Li; Jiuping Pan; Yong Liu; Yilu Liu. An optimal combined operation scheme for pumped storage and hybrid wind-photovoltaic complementary power generation system. Applied Energy 2019, 242, 1155 -1163.
AMA StyleKaiqi Sun, Ke-Jun Li, Jiuping Pan, Yong Liu, Yilu Liu. An optimal combined operation scheme for pumped storage and hybrid wind-photovoltaic complementary power generation system. Applied Energy. 2019; 242 ():1155-1163.
Chicago/Turabian StyleKaiqi Sun; Ke-Jun Li; Jiuping Pan; Yong Liu; Yilu Liu. 2019. "An optimal combined operation scheme for pumped storage and hybrid wind-photovoltaic complementary power generation system." Applied Energy 242, no. : 1155-1163.
Kaiqi Sun; Ke-Jun Li; Wei-Jen Lee; Zhuo-Di Wang; Weiyu Bao; Zhijie Liu; Meiyan Wang. VSC-MTDC System Integrating Offshore Wind Farms Based Optimal Distribution Method for Financial Improvement on Wind Producers. IEEE Transactions on Industry Applications 2019, 55, 2232 -2240.
AMA StyleKaiqi Sun, Ke-Jun Li, Wei-Jen Lee, Zhuo-Di Wang, Weiyu Bao, Zhijie Liu, Meiyan Wang. VSC-MTDC System Integrating Offshore Wind Farms Based Optimal Distribution Method for Financial Improvement on Wind Producers. IEEE Transactions on Industry Applications. 2019; 55 (3):2232-2240.
Chicago/Turabian StyleKaiqi Sun; Ke-Jun Li; Wei-Jen Lee; Zhuo-Di Wang; Weiyu Bao; Zhijie Liu; Meiyan Wang. 2019. "VSC-MTDC System Integrating Offshore Wind Farms Based Optimal Distribution Method for Financial Improvement on Wind Producers." IEEE Transactions on Industry Applications 55, no. 3: 2232-2240.
Zhijie Liu; Ke-Jun Li; Jinyu Wang; Zahid Javid; Meiyan Wang; Kaiqi Sun. Research on Capacitance Selection for Modular Multi-Level Converter. IEEE Transactions on Power Electronics 2018, 34, 8417 -8434.
AMA StyleZhijie Liu, Ke-Jun Li, Jinyu Wang, Zahid Javid, Meiyan Wang, Kaiqi Sun. Research on Capacitance Selection for Modular Multi-Level Converter. IEEE Transactions on Power Electronics. 2018; 34 (9):8417-8434.
Chicago/Turabian StyleZhijie Liu; Ke-Jun Li; Jinyu Wang; Zahid Javid; Meiyan Wang; Kaiqi Sun. 2018. "Research on Capacitance Selection for Modular Multi-Level Converter." IEEE Transactions on Power Electronics 34, no. 9: 8417-8434.
As the typical clean and renewable energy, wind energy has witness a continuous annual increase in last few decades. Due to the random and intermittent characteristics, the wind producers in the electric market meet serious financial losses caused by deviation between the actual power output and forecasting result. Increasing the accurate of forecasting is difficult to achieve in a short time, how to improve the financial income has become a major task to wind producers and academia. As the backbone network of the offshore wind farms, VSC-MTDC has been regarded as one of the effective solutions to transport wind power. In this paper, an optimal distribution method is proposed for VSC-MTDC system integrating offshore wind farms to reduce the financial loss due to deviation between the actual wind power output and forecasting result. The proposed method could be divided into two parts. The first part of the proposed method is to analyze the onshore external system according to the historical system operation data and adjust the droop coefficient with analytic hierarchy process. The second part of the proposed method is to do the further adjusting according to the regulating price. With the simulation results, the proposed optimal distribution method is proved that it could bring more benefit to wind producers without more additional investment.
Kaiqi Sun; Ke-Jun Li; Wei-Jen Lee; Zhuo-Di Wang; Weiyu Bao; Zhijie Liu; Meiyan Wang. VSC-MTDC System Integrating Offshore Wind Farms Based Optimal Distribution Method for Financial Improvement on Wind Producers. 2018 IEEE Industry Applications Society Annual Meeting (IAS) 2018, 1 -7.
AMA StyleKaiqi Sun, Ke-Jun Li, Wei-Jen Lee, Zhuo-Di Wang, Weiyu Bao, Zhijie Liu, Meiyan Wang. VSC-MTDC System Integrating Offshore Wind Farms Based Optimal Distribution Method for Financial Improvement on Wind Producers. 2018 IEEE Industry Applications Society Annual Meeting (IAS). 2018; ():1-7.
Chicago/Turabian StyleKaiqi Sun; Ke-Jun Li; Wei-Jen Lee; Zhuo-Di Wang; Weiyu Bao; Zhijie Liu; Meiyan Wang. 2018. "VSC-MTDC System Integrating Offshore Wind Farms Based Optimal Distribution Method for Financial Improvement on Wind Producers." 2018 IEEE Industry Applications Society Annual Meeting (IAS) , no. : 1-7.
Modular multilevel converters (MMCs) have shown great potential in the area of multi-megawatt wind energy conversion system (WECS) based on permanent magnet synchronous generators (PMSGs). However, the studies in this area are few, and most of them refer to the MMC used in high-voltage direct current (HVDC) systems, and hence the characteristics of the PMSG are not considered. This paper proposes a steady-state analysis method for MMCs connected to a PMSG-based WECS. In the proposed method, only the wind speed (operating condition) is required as input, and all the electrical quantities in the MMC, including the amplitudes, phase angles and their harmonics, can be calculated step by step. The analysis method is built on the proposed d-q frame mathematical model. Interactions of electrical quantities between the MMC and PMSG are comprehensively considered. Moreover, a new way to calculate the average switching functions are adopted in order to improve the accuracy of the analysis method. Applications of the proposed method are also presented, which includes the characteristic analysis of capacitor voltage ripples and the capacitor sizing. Finally, the accuracy of the method and the correctness of the analysis are verified by simulations and experiments.
Zhijie Liu; Kejun Li; Yuanyuan Sun; Jinyu Wang; Zhuodi Wang; Kaiqi Sun; Meiyan Wang. A Steady-State Analysis Method for Modular Multilevel Converters Connected to Permanent Magnet Synchronous Generator-Based Wind Energy Conversion Systems. Energies 2018, 11, 461 .
AMA StyleZhijie Liu, Kejun Li, Yuanyuan Sun, Jinyu Wang, Zhuodi Wang, Kaiqi Sun, Meiyan Wang. A Steady-State Analysis Method for Modular Multilevel Converters Connected to Permanent Magnet Synchronous Generator-Based Wind Energy Conversion Systems. Energies. 2018; 11 (2):461.
Chicago/Turabian StyleZhijie Liu; Kejun Li; Yuanyuan Sun; Jinyu Wang; Zhuodi Wang; Kaiqi Sun; Meiyan Wang. 2018. "A Steady-State Analysis Method for Modular Multilevel Converters Connected to Permanent Magnet Synchronous Generator-Based Wind Energy Conversion Systems." Energies 11, no. 2: 461.
This paper presents a decentralized technique based protection and control scheme for the active radial distribution network. A partitioning method for radial distribution network with multi-distributed energy resources is developed considering island operation possibility of DER, hence, the active distribution network is partitioned into zones with DER and zones without DER. Directional node configuring method is proposed to identify the positional relation of circuit breakers (CBs) on boundaries of zones. After configuring each intelligent feeder terminal units (IFTUs) with the directional node relationship information, the connection relationship between zones can be obtained automatically. So that only by communicating with its neighbors, the IFTU can decide which CBs should be opened when a fault occurs. Peer to peer communication technique is established for interacting fault measurement information among the adjacent IFTUs, fast and accurate faulted zone location and isolation can be achieved. Meanwhile, seamless islanding of the zone integrating DERs can be realized to keep supplying power to the islanded feeder continuously after distribution network splitting. Moreover, power balance control for intentional islanding is discussed to ensure the islanding stable. Finally, results of case studies demonstrate the feasibility and effectiveness of the proposed scheme.
Jingshan Wang; Ke-Jun Li; Mingqiang Wang; Ying Sun; Zahid Javid. A decentralized technique based protection and control scheme for distribution network with high DER penetration. 2017 IEEE Industry Applications Society Annual Meeting 2017, 1 -6.
AMA StyleJingshan Wang, Ke-Jun Li, Mingqiang Wang, Ying Sun, Zahid Javid. A decentralized technique based protection and control scheme for distribution network with high DER penetration. 2017 IEEE Industry Applications Society Annual Meeting. 2017; ():1-6.
Chicago/Turabian StyleJingshan Wang; Ke-Jun Li; Mingqiang Wang; Ying Sun; Zahid Javid. 2017. "A decentralized technique based protection and control scheme for distribution network with high DER penetration." 2017 IEEE Industry Applications Society Annual Meeting , no. : 1-6.
With the increasing penetration of renewable energies, the seamless integration and related energy management problems present challenges to the traditional power grid. Voltage source converter based multi-terminal HVDC (VSC-MTDC) has been regarded as a prospective emerging technology for the above mentioned issues. With its flexible control characteristics, it is expected that VSC-MTDC systems will play important role in the future power grid. Furthermore, a multi-voltage level VSC-MTDC systems will have the potential to enhance the flexibility and redundancy of the power system. This paper presents control algorithms for a multi-voltage-level DC network to improve the utilization rate of renewable energies and mitigate the coordinated and interconnected problems of distributed renewable energies and urban power load. The operating of auto-power-balancing mode and the power cooperation mode and their corresponding control strategies are analyzed in this paper. For the auto-power-balancing mode, the centralized DC power control is proposed to mitigate the disturbance caused by power fluctuation. For the power cooperation mode, the unbalanced power redistribution control is proposed to eliminate the unbalanced power when the master station encounters problems. The simulation in PSCAD/EMTDC for a twelve VSC-MTDC system demonstrates the effectiveness of the proposed operation modes and corresponding control strategies.
Kaiqi Sun; Ke-Jun Li; Wei-Jen Lee; Zhuo-Di Wang; Zhijie Liu; Meiyan Wang; Zahid Javid. Operation and control for multi-voltage-level dc network to improve the utilization rate of renewable energies. 2017 IEEE Industry Applications Society Annual Meeting 2017, 1 -8.
AMA StyleKaiqi Sun, Ke-Jun Li, Wei-Jen Lee, Zhuo-Di Wang, Zhijie Liu, Meiyan Wang, Zahid Javid. Operation and control for multi-voltage-level dc network to improve the utilization rate of renewable energies. 2017 IEEE Industry Applications Society Annual Meeting. 2017; ():1-8.
Chicago/Turabian StyleKaiqi Sun; Ke-Jun Li; Wei-Jen Lee; Zhuo-Di Wang; Zhijie Liu; Meiyan Wang; Zahid Javid. 2017. "Operation and control for multi-voltage-level dc network to improve the utilization rate of renewable energies." 2017 IEEE Industry Applications Society Annual Meeting , no. : 1-8.
Shuang Hu; Ke-Jun Li; Yanshun Xu; Zhijie Liu; Jing Guo; Zhuodi Wang. Research on three-phase unbalanced distribution network reconfiguration strategy. IOP Conference Series: Earth and Environmental Science 2017, 52, 12037 .
AMA StyleShuang Hu, Ke-Jun Li, Yanshun Xu, Zhijie Liu, Jing Guo, Zhuodi Wang. Research on three-phase unbalanced distribution network reconfiguration strategy. IOP Conference Series: Earth and Environmental Science. 2017; 52 ():12037.
Chicago/Turabian StyleShuang Hu; Ke-Jun Li; Yanshun Xu; Zhijie Liu; Jing Guo; Zhuodi Wang. 2017. "Research on three-phase unbalanced distribution network reconfiguration strategy." IOP Conference Series: Earth and Environmental Science 52, no. : 12037.