Journals
2018 EN
Li Peishuai · Wu Zaijun · Wang Yang
+3 more
Due to the increasing penetration of the uncertain single‐phase distributed generations (DGs), the current distribution networks are becoming more uncertain, unbalanced, and complicated than ever before, which brings great challenges for distribution network operators. This study proposes an adaptive robust optimal reactive power dispatch approach for the unbalanced distribution networks (U‐DNs) considering uncertainty caused by DGs. Leveraging the reactive power compensation from inverters of DGs, the purpose of the proposed method is to minimise power losses and maintain the voltage within regulatory limits. The feasible region of DGs is estimated and considered as a new constraint, aiming to guarantee the reliable operation of U‐DNs. The optimal reactive power dispatch problem is then formulated as an adaptive robust optimisation problem based on semidefinite programming. The adaptive function, which derives the relationship between reactive power and active power outputs of DGs, is utilised to make the method more flexible and less conservative. The cutting plane algorithm is introduced to solve the proposed adaptive robust reactive power dispatch model efficiently. Moreover, case studies are separately conducted on the modified IEEE 13‐bus and 123‐bus test systems to demonstrate the effectiveness of the proposed method.
The Institution of Engineering and Technology
Journals
2018 EN
Dou Chunxia · Zheng Yuhang · Yue Dong
+2 more
Accurate renewable resource and load forecasting plays a key role in the progress of power grid planning schemes. In this study, a hybrid short‐term forecasting method based K ‐means clustering and variational mode decomposition (VMD) technique is proposed to deal with the problem of forecasting accuracy. K ‐means clustering is a means of data mining approach and used for classifying data into several clusters. A cluster selection method is adopted to extract similar features from historical days. To better analyse the time series of historical data, VMD decomposes time series data into an ensemble of components with different frequencies. Self‐adaptive evolutionary extreme learning machine as a novel and fast regression tool is trained and used for predicting each component. Eventually, the forecasting result generated by reconstructing all the predicted components values. The performance of the proposed hybrid forecasting model is evaluated by using real data from National Renewable Energy Laboratory. The simulation results show that it can obtain better forecasting accuracy than some previously reported methods.
The Institution of Engineering and Technology
Journals
2018 EN
Zhang Bo · Dou Chunxia · Yue Dong
+1 more
Communication data in the communication network of the islanded micro‐grid can be disturbed in many ways, such as data attack or packet loss. To improve the control effect on the voltages and frequencies obtained by droop control of distributed energy resources (DERs) facing communication data disturbance (CDD), a response hierarchical control strategy is proposed in this study. Based on the concept of the cyber physical system, the control structure is divided into two layers: the cyber layer and physical layer. In the cyber layer, firstly, the effect of the CDD on the micro‐grid system is analysed and then, an event‐triggered data compensation method combining the back‐propagation neural network and extreme learning machine is proposed in this layer to solve the problem of the CDD. In the physical layer, firstly, the droop control is used as the primary control to control the voltages and frequencies of DERs and then, a novel virtual leader‐following consensus control method considering time‐delay is proposed in this layer. Also, it is used to complete the secondary control of the voltage and frequency obtained by primary control. In the end, the simulation results confirm the effectiveness of the proposed hierarchical control strategy under CDD.
The Institution of Engineering and Technology
Journals
2018 EN
Wang Xiaonan · Dou Zhengxiong · Mu Yi
Content‐centric networking (CCN) used the name of an Interest to seek the target content, where the name was a plaintext and unprotected. Apart from the name, the content in one Data is also unprotected. If an unauthorised node intercepted an Interest , it could infer what kind of content is requested. If the node intercepted a response Data , it could illegally acquire the content. This study focused on the privacy issues of CCN and proposed a CCN framework with privacy support. In this framework, the concept of a privacy name was proposed and accordingly the forwarding information base (FIB) and pending Interest table (PIT) establishment algorithms based on privacy names were proposed. On the basis of the proposed FIB and PIT, the content communication algorithm based on privacy names was presented. In this algorithm, one authorised consumer could use a privacy name to seek, retrieve and share the ciphertext of the content, so the privacy was achieved. Finally, the privacy of this framework was analysed and the performance was evaluated to justify its advantages.
The Institution of Engineering and Technology
Journals
2018 EN
Dou Zhengxiong · Wang Xiaonan · Li Yanli
With technological advancements, vehicles are equipped with abundant storage capability and powerful computing capability. This leads to an advanced kind of vehicular ad hoc network service, which enables local collaborations among vehicles to produce service data an individual cannot make alone. To support this advanced service, a vehicular cloud (VC) is proposed. One VC usually adopts flooding to acquire data, so the data acquisition cost is relatively high. To reduce the cost, the authors employ the address‐based unicast to achieve data acquisition and propose a data acquisition method based on address‐based VC. In this method, the unicast address and data address are proposed to establish a relationship between one kind of specific data and an address. On the basis of the data address, a vehicle can retrieve data from the nearest VC member in the unicast way, so the data acquisition cost is reduced. This proposal is evaluated, and the data show that the data acquisition cost is effectively reduced.
The Institution of Engineering and Technology
Journals
2018 EN
Jin Nan · Guo Leilei · Gan Chun
+2 more
Under unbalanced grid fault conditions, the current harmonic contents of a three‐phase bidirectional AC/DC converter increase significantly and twice grid‐frequency ripples exist in both active power and reactive power, which influence the output power quality of the converter. Compared with the conventional finite‐state model predictive direct power control (MPDPC), the MPDPC with power compensation (MPDPC‐PC) method is proposed for the three‐phase bidirectional AC/DC power converter to reduce harmonic currents and output power ripples without extraction of complex positive/negative sequences from the grid voltage/current and phase‐locked loop. The power compensation values are expressed by grid voltages and their quadrature signals that lag 90 electrical degrees in the αβ stationary coordinates system. MPDPC‐PC exhibits better performance by reducing the harmonic contents of grid currents and eliminating active power or reactive power ripples of the three‐phase bidirectional AC/DC converter with flexible reactive power compensation capability. Compared with the MPDPC and linear current control schemes, experimental results confirm the effectiveness of the designed method under unbalanced grid conditions.
The Institution of Engineering and Technology
Journals
2018 EN
Dou Chunxia · Zhang Bo · Yue Dong
+4 more
In order to improve the control effect on voltage and frequency of each distributed energy resource (DER) and improve the stability of the islanded micro‐grid, a novel hierarchical control strategy combined sliding mode control (SMC) and consensus control is proposed in this study. The control structure is divided into two layers: the physical layer and the cyber layer. In the physical layer, in order to improve the dynamic control effect, an improved droop control based on consensus theory with considering packet loss is proposed in this study. And the control can be completed in finite time by selecting the approximate parameters in the controller; in order to improve the stability of voltage loop and current loop, an improved double closed‐loop structure based on the SMC is proposed. Moreover, the control can also be completed in the finite time. In the cyber layer, an event‐triggered SMC‐virtual leader–following consensus protocol is proposed in this study to solve the problem of channel noise (disturbance). For improving the control effect, the protocol is used to complete the secondary control on voltage and frequency of each DER. Finally, the effectiveness of the novel control strategy is verified by simulation results.
The Institution of Engineering and Technology
Journals
2018 EN
Dou Mingwu · Zhang Wenwu
This study focuses on range estimate for life detection based on the characteristics analysis of life signs by employing the ultra‐wideband (UWB) impulse radar. Via analysing the standard deviation of life signs, the time of arrival (TOA) of the pulse from the radar receiver to detection target is estimated based on the calculated energy blocks. Based on the obtained TOA estimates, one area containing life information is determined, which is referred to as region of interest (ROI). Using the signals in ROI, the frequency of human breathing motion is measured more easily and accurately. Different experiments are carried out to test the performance of the new method in through‐wall conditions. Results show perfect capability of detection and improving signal‐to‐noise ratio.
The Institution of Engineering and Technology
Journals
2018 EN
Jingru Jia · Jinhai Zhang
UV polyurethane acrylate (PUA-1) oligomer was synthesized and used to prepare the UV-LED ceramic ink transfer film. The effects of active thinner (or active monomer), photosensitizer type, photo-sen-sitizer percentage, photosensitizer consumption, etc. on the ceramic ink transfer film performance was studied. The results showed that the prepared PUA prepolymer, single functional group thinner, and the UV-LED curing system consisting of 2,4,6-Trimethyl Benzoyl Diphenyl Phosphine Oxide (TPO), 2,4-Diethyl-9H-Thioxanthen-9-one(DETX) and Reactive Amine (P115) could meet the technical requirements of transfer film.
Journals
2018 EN
Yi Chen · Cui Rongyao · Rongbo Ju
+1 more
Shimmy stability of the nose landing gear of an aircraft is studied in this paper. Firstly, Shimmy model was built considering the dynamic characteristics of the airframe. Then the critical damping, critical velocity and frequency range of the shimmy are obtained by introducing relevant parameters into the shimmy model. The research shows that the problem of shimmy is a tire type shimmy caused by insufficient damping of dampers and brings coupled resonance with the vibration mode of the airframe, which can be avoided by increasing the damping of the shimmy. At the same time, the influence of airframe dynamics and tire stiffness on the shimmy characteristics of the landing gear is also studied. With the increase of tire torsion and lateral stiffness, the critical velocity, maximum critical damping value and shimmy frequency of the landing gear increase. However, the elasticity of the airframe makes the frequency of the aircraft landing gear lower and the stable region of the shimmy smaller, so that the phenomenon of shimmy is more likely to occur. Therefore, the influence of airframe dynamic characteristics can not be ignored when studying the shimmy stability of the landing gear of a modern large passenger aircraft.