Liu Dichen

Modeling of a Large-scale Photovoltaic Generation and Analysis of its Security and Stability Operation in West-Qinghai Grid

Based on modeling of photovoltaic cell and array according to project requirement and modeling of converter according to grid-connected control tragedy, the model of photovoltaic generation system is established. By principle of constant power-loss, the equivalent method of large photovoltaic station is proposed in order to being applied in large power system simulation. Thereafter, making use of the new acquired model, the analysis of security and stability of 2011 Haixi Grid integrating large-scale photovoltaic station is constructed, including security characteristic, steady state stability limit and transient stability limit in power delivery and receive mode, so as to guide the operation controlling and planning in Haixi Grid.

The study on the radio interference from ±800kV Yun Guang UHVDC transmission line

The radio interference is one of the important electromagnetic environment parameters for UHV DC transmission line. This paper validates the radio interference calculating formula of DC transmission line recommended by CISPR though measured data from three 500 kV DC transmission lines that have been built in China. The radio interference from plusmn800 kV Yun Guang UHVDC transmission line with different types of conductors, height of conductors above the ground ,and different space between anode and cathode line is calculated using CISPRs formula. It is concluded that the radio interference level of plusmn800 kV Yun Guang UHVDC transmission line should be limited in 55~58 dB(muV/m), and the conductor section of line should be chosen 5times720 or more.

Research of Adaptive Computation of Very-short-term Load Forecast in VQC

Load prediction is necessary in VQC, because if the variation tendency of voltage and reactive power can be forecasted, the system can analyze and control in advance. There are many algorithms for load prediction. This paper presents an improved control method based on very-short-term forecast. The voltage and reactive power data queues are acquired from electric line with high speed, then the values after a certain time is predicted adaptively using improved least-square method. With load prediction involved in, higher sensitivity and better effect of the control can be achieved when the reactive power changes greatly

Study on the measurement of HV insulator's leakage current based on the adaptive noise cancellation theory

In the electric power system HV transmits, contamination flashover in the HV insulator is getting worse and worse, so a way to find an HV insulator which is being invalid is of great importance in the measurement of HV insulator leakage current. On the basis of the theory of adaptive noise cancellation and adaptive line enhancement, we have provided an improved adaptive noise cancellation used in the measurement of HV insulator leakage current, which is of good performance not only in the case of LF noise cancellation like the adaptive line enhancement, but also in the case of LF noise cancellation like the normal adaptive noise cancellation, and it is proved to be efficient and robust through emulation and simulation experiments.

The study of metal meshes on electromagnetic interference shielding effectiveness

There is a good shielding effectiveness of metal meshes on electromagnetic interference caused by all kinds of reasons. 11 metal meshes of different specification of four materials are tested at different frequency steady-state fields and single variable transient fields. Also, their shielding effectiveness is calculated and analyzed. The results of the tests and analysis show that: (1) shielding effectiveness is correlated with factors such as the meshes diameter, mesh variable-density structure standards and so on; (2) within a certain frequency, the effect of mesh size on shielding effectiveness is small; metal materials shielding effectiveness changes with the frequencys variety; and (3) in shielding of the tying measure of metal mesh weld show its superiority over the screw. We must ground the shielding body reliably. The tests and analysis results of this paper are of important significance in anti-interference study and application to electromagnetic compatibility, modern monitors, communication, and computer control rooms.

A study on the radio interference of the 500kV double circuit transmission lines in the Sanxia power station

This paper has calculated the radio interference of the 500 kV double circuit transmission lines in the Sanxia power station, and it has analyzed and predicted the radio interference level of the 500 kV double circuit transmission lines in the Sanxia power station, together with factual metrical results of the operating lines.

Asynchronized synchronous generator's variable structure excitation control and its transient analysis

The asynchronized synchronous generators (ASG) rotors torque equation, electromagnetic transient equation and cycloconvertors differential equation are analyzed. Its nonlinear state space equations are put forward. The optimal exciter is designed according to the variable structure control theory. The simulator results show that the cycloconvertors transient equation is indiscernible as the state equation of ASG. The variable structure method is compared with the PID and the optimal linear control method in a one machine infinite bus. The simulation results show that the variable structure control method is effective and feasible.

Static stability of asynchronized synchronous generator for power system

An asynchronized synchronous generators (ASG) nonlinear state space equations, including the cycloconverters frequency adjusting process, are put forward. According to the state equations, the static stability of an ASG is analyzed, and the relation between the stability and the magnifying coefficient and the damping coefficient is also discussed.

Research of control strategy of SVC on subsynchronous oscillation suppression

Subsynchronous oscillation may cause the unstable torsional vibration of turbine-generator shaft system, and even damage the generator shaft, endangering the safe operation of power system. Based on the simulation, this paper uses Static Var Compensator to damp subsynchronous oscillation by utilizing extra voltage control and modal separation control. The subsynchronous oscillation effect of Static Var Compensator suppressing IEEE first benchmark model under the above two control strategies is analyzed and compared in detail. It is shown that both of the control strategies can help to damp subsynchronous oscillation, but the effect of modal separation is relatively better on the whole.

Analysis of substation noise prediction based on equivalent source method

When predicting the noise level of substation, the model of transformers and reactors as noise sources is very important. A new acoustic mode of the transformers and reactors is built in ultra-high voltage substation. Each of the transformers and reactors is equivalent to several point sources based on equivalent source method. And in the process of the equivalent, the measurement and calculation are made easier by using sound power level to represent the equivalent sources intensity. A model of 9 equivalent point sources is chosen to verify the accuracy of the model. This acoustic model of the transformers and reactors is combined with outdoor point sound sources attenuation theory to predict the substation noise value. Simulation of a 1000kV substation has been down which shows that the model is feasible to calculate the noise level anywhere inside the substation.