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Chen F.,Shandong University | Chen F.,University of Jinan | Han X.,Shandong University | Kang K.,Yantai Power Supply Company
Dianli Xitong Zidonghua/Automation of Electric Power Systems | Year: 2011

In generalized state estimation, to identify the misinformation of the connected region formed by the closed breakers, the concept of virtual breakers is used to build the minimum feature network based on the generalized network that does not affect the quality of identification. In addition to analog measurements, zero-voltage-drop for virtual closed switch as equality constraint is added to formulate the model of weighted least squares with equality constraints. The relation between residual and Lagrange multiplier from the probability standpoint is discussed alongside the approach to identifying bad data. Furthermore, it can be seen that the identification of the bad analog data is distinguished from that of the bad breaker status under normal conditions. Finally, the validity of the model and algorithm is verified with a three-node simple system and the data from Yantai grid of Shandong Province. © 2010 State Electric Power Research Institute Press.


Wang J.,Harbin Institute of Technology | Wang J.,ShenYang Agricultural University | Cai X.,Harbin Institute of Technology | Ji F.,Harbin Institute of Technology | Li X.,Yantai Power Supply Company
Dianli Xitong Zidonghua/Automation of Electric Power Systems | Year: 2012

With the rapid development of renewable energy power generation, its intermittence and stochastic of output power have significant influence on available transfer capability (ATC). The characteristics of the renewable energy power generation, e. g. the intermittence, stochastic, load fluctuation, and status uncertainty, are simulated through Monte Carlo simulation method. The ATC under specific status and parameters of system are solved through optimal power flow. The probability density of ATC samples is defined by applying probability statistics theory to establish a risk benefit model, and to achieve ATC with maximum comprehensive benefits. To analyze the influence of renewable energy power generation on ATC, with respect to position of power generation equipment, uncertainty of power output and penetration level etc. The method is validated by simulation on a modified IEEE 118 system involving wind power and solar power.


Yu J.-Y.,North China Electrical Power University | Wang Z.-P.,North China Electrical Power University | Sun J.,Yantai Power Supply Company | Yang G.-S.,China Electric Power Research Institute
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2014

To solve the premature issue of particle swarm optimization (PSO), this paper introduces the idea of simulated annealing into the dynamic inertia weight adjustment to make the inertia weight decrease with the increase in the number of iterations and avoid the algorithm falling into local optimization. And it uses population fitness variance to judge the particles' similarity in order to mutate the particle adaptively, i.e. control the mutation number "big then small" and select particles randomly and rebuild displacement. In order to improve the search speed of PSO algorithm, the PSO algorithm and branch exchange algorithm are combined, in which the particle displacement is just the contact switch connecting non-fault power-lossing area and normal area, as for the scheme of forming looped network, the branch exchange algorithm is used to determine the section switch to open. The combination of PSO and branch exchange could ensure the radial operation requirements of distribution grid, and make the network formed by a lower net loss. The example shows that the distribution network fault recovery based on branch exchange-PSO can quickly restore power supply of power failure area.


Yuan J.,Shandong University | Gao F.,Shandong University | Gao H.,Shandong University | Liu B.,Yantai Power Supply Company | And 2 more authors.
Diangong Jishu Xuebao/Transactions of China Electrotechnical Society | Year: 2011

The stand-alone photovoltaic (PV) systems depend on batteries or adjustable load to keep the balance of generated power and load. The control modes of PV generation transit among maximum power point tracking (MPPT), voltage regulating or current limiting modes using the traditional energy management system. This paper proposes a unified energy control strategy for stand-alone PV system to control PV generation, charging and discharging of battery, consumption as a whole according to the inherent theory of energy balance and DC bus voltage variation. The proposed strategy optimizes rear-end load power including battery by regulating dc bus voltage. And then it controls PV generation following load variation smoothly without using the traditional transition of control modes. Meanwhile, under the unified energy control strategy, an optimal searching method of PV working point is presented to avoid dc conversion failure. Matlab simulations show the performance of proposed control method with captured results presented for viewing.


Huamao Z.,North China Electrical Power University | Yazhou L.,North China Electrical Power University | Yazhou L.,Yantai Power Supply Company | Shusheng Z.,North China Electrical Power University
IEEE Sensors Journal | Year: 2016

Ultra-high-frequency (UHF) sensor is the vital component of a partial discharge detection system and its coupling performance is affected by structural parameters. On the basis of the cavity model theory, this paper studied the influence of the disc electrode diameter, the thickness, the dielectric constant of the dielectric substrate, and the position of the coaxial connection on the performance of the disc-type UHF sensor with the application of the XFdtd software. The simplified finite-difference time-domain simulation model for the gigahertz transverse electromagnetic (GTEM) cell has been established, and the influence of the coaxial feed position on the performance of the disc-type UHF sensor is studied via the frequency domain effective heights in the simulation. The result shows that as the disc electrode diameter, the thickness, and the dielectric constant of the dielectric substrate increase, the working frequency band shifts toward the reducing direction. The position of the coaxial connection has an obvious effect on the resonant mode of sensor, too. © 2016 IEEE.


Yuan J.,Shandong University | Gao H.,Shandong University | Gao F.,Shandong University | Wang R.,Yantai Power Supply Company | And 2 more authors.
Dianli Xitong Zidonghua/Automation of Electric Power Systems | Year: 2010

A novel indirect DC-link voltage control scheme is presented for two-stage three-phase grid-connected inverter, which is applicable to connecting renewable energy generation system to the power grid. Different from the traditional direct DC-link voltage control scheme, the method proposed is realized by calculating and controlling the amplitude of sinusoidal modulation signals. This eliminates the DC-link voltage sensor and makes the whole system more reliable and less expensive. After analyzing the operational principle under balanced operation condition, the indirect DC-link voltage control method has then been successfully extended to implement in three-phase voltage unbalance condition. MATLAB simulations prove the validity of the control method proposed. © State Grid Electric Power Research Institute Press.


Li Z.,Shandong University | Han X.,Shandong University | Yang M.,Shandong University | Lei Y.,Shandong University | Kang K.,Yantai Power Supply Company
Dianli Xitong Zidonghua/Automation of Electric Power Systems | Year: 2010

As wind power capacity in a power grid reaches a certain level, the system dispatch becomes more complex for efficient utilization of wind power. In a power grid with wind farms connected, there is a contradiction between fuel cost and effective utilization of wind power in the scheduling process. The fuel cost saved by the wind power is taken as the measurement for the value of wind power. A scheduling method considering wind power integration is proposed so that a fluctuation range can be calculated to coordinate the fuel cost and wind power grid connection. Case study in the Yantai power grid shows that the method proposed is appropriate for the power grid scheduling in accordance with the principle of economic generation dispatch. © 2010 State Grid Electric Power Research Institute Press.


Li Z.,Shandong University | Han X.,Shandong University | Han L.,China International Engineering Consulting Corporation | Kang K.,Yantai Power Supply Company
Dianli Xitong Zidonghua/Automation of Electric Power Systems | Year: 2010

Considering a regional grid with several wind farms integrated, the total wind power has a better regularity comparing to that of a single wind farm. An ultra-short-term wind power forecasting method is proposed based on the concepts of total wind power and distribution factor. The least-square support vector machine (LS-SVM) and Kalman filter are adopted respectively to forecast the total wind power and distribution factor recursively, so that the good regularity of total wind power can be restored. Case studies show that the method not only improves the forecasting accuracy but also reduces the distribution range of the forecasting errors. © 2010 State Grid Electric Power Research Institute Press.


Chen F.,Shandong University | Han X.,Shandong University | Kang K.,Yantai Power Supply Company | Li H.,Shandong Electric Power Research Institute
Dianli Xitong Zidonghua/Automation of Electric Power Systems | Year: 2010

Based on SCADA information, the soft realization idea for dynamic thermal rating (DTR) is presented, which establishes continuous estimation model of transmission line temperature and parameters of its heat balance differential equation (HBE). Firstly, based on the explicit analytic physical rules for relationship between conductor's resistance and temperature, an extended estimation model of line resistance is established with measurements of the line, then the transmission line's temperature can be obtained indirectly; Secondly, considering resistance change Markov property, the adjacent time priori information of resistance is used to modify the estimation result so as to improve its accuracy; Finally, with the known transmission line temperature series, a fading-memory recursive least square method is used to estimate parameters of reduced HBE, hence, the function of DTR hardware is realized indirectly through electric measurement of transmission line. The feasibility of the proposed method is verified by the tested data from Yantai grid of Shandong province. ©2010 State Grid Electric Power Research Institute Press.


Yuan J.,China Three Gorges University | Gao H.,Shandong University | Gao F.,Shandong University | Wu J.,Shandong University | And 3 more authors.
Dianwang Jishu/Power System Technology | Year: 2012

Photo voltaic (PV) generation and energy storage devices are mainly configured in sub DC network of hybrid AC/DC microgrid and provide power supply for DC load, and using parallel PV inverters a part of PV generations can be connected with sub AC network via point of common coupling (PCC) to supply power for AC loads, thus when sub AC network is being disconnected from conventional power grid the fluctuation of power output of PV generation in sub AC network should be eliminated. A control strategy for parallel PV inverters under the condition of disconnecting sub AC network from conventional grid was proposed: the parallel PV inverter configured in DC network was regarded as master inverter and supply total reactive power and part of active power for sub AC network by constant voltage amplitude and power-frequency droop method; a part of PV inverters with lower capacities were regarded as slave inverters, which did not supply reactive power and supplied only active power controlled by adaptive droop coefficient method, and this part of active power was matched with maximum real-time power of PV generation, thus not only the voltage stability of sub AC network could be maintained, but also the capabilities of PV generations could be fully utilized. Both correctness and feasibility of the proposed control strategy were verified by results of simulation based on Matlab.

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