Advanced Materials Research Vols. 805-806

Abstract: In order to study the feasibility ofrespective control mode that high voltage side valve group and low voltage side valve group in a single poleare respectively controlled, and the merits and demerits of this mode and jointcontrol modethattwo 12-pulse converter groups are jointlycontrolled in UHVDC power transmission systems simulation.±800 kV UHVDC transmission project model is set up. The operation characteristics of steady state and deblocking and blocking of high voltage side valve group are simulated. The comparison and analysis results show that: steady-state simulation waveforms of the two control mode can be a good correspondence; the basic strategies of blocking and deblockingare same, the dynamic characteristics are similar; therespective control mode is entirely feasible in UHVDC power transmission systems simulation.

Abstract: Experienced engineers in transformer substation can judge the equipment condition via just listening to the working sounds of electrical equipments. Use audio signal processing applied in engines and other mechanical equipments for reference. A scheme to monitor the working condition of electrical equipments is proposed. Firstly, the basic principles and system structure of this scheme is outlined. It introduces the method of colleting electrical equipments working sounds by Microphone array, because Microphone array form a beam to target the source sound, which can reduce the noise and reverberation. When substation is working, the environmental background interference sounds exist and are independent from electrical working sound. So we can use FastICA algorithm that is based on the largest negentropy to separate the collected sound to several independent source signals. It has the advantage of fast convergence and robust. The simulation result shows this algorithm can effectively separate the multiple independent source signals. The separation accuracy is above 95% for typical sample mixed sounds and the reliability of electrical equipment fault detection system based on audio signal processing is ensured.

Abstract: The power load modeling system is designed with denoising and parameter identification. This system consists of signal acquisition, signal preprocessing, parameter identification, different load modeling methods such as ZIP model and Dynamic modeling. Original signal can be read from Excel file, which is the simulated signal or measurement signal. Then some kinds of denoising methods can be selected, which are mean filtering, medial filtering and wavelet denoising. After being denoised, the load signal is suitable for the parameter identification process. ZIP model is used to simulate the static load model, and the dynamic model is used to simulate the dynamic load model which is changeable during different periods. With the parameter identification and simulation process, measurement power load signal is used in the experiment, the dynamic model is more suitable for the variable load voltage features description.

Abstract: Combined with the contents of the study-PSS low-pass link parameter identification. Least-squares method is selected. Using least-square method for PSS low-pass link mathematical model are also deduced. For the results, because of the mathematical model is solving nonlinear equations, cannot used by the Newton method directly. So we choose to use Newton iterations, with this feature, choose to use MATLAB software to solve the equation. Identification of the use of MATLAB software lags after the PSS parameters obtained recognition results compared with national standards, identifying and verifying the practicability.

Abstract: SoPC technology provides a more convenient, flexible and reliable hardware and software co-design for embedded system design. In this paper we use this method in respect of software and hardware to design a new high performance hydropower on-line monitoring system. The device has been successfully integrated in the hydropower on-line monitoring system. The practical application confirms it has high performance, good stability, scalability, and the design method for power occasions other similar applications are also of great referential significance.

Abstract: The thermal power units operational reliability is the fundamental guarantee of smooth operation of electricity system. According to the problem of thermal power units operational reliability evaluation, a comprehensive evaluation method is put forward based on grey fuzzy theory. Firstly, this paper establishes an evaluation index system by the analysis of factors affecting the reliability of thermal power units. And then a reliability evaluation model of thermal power units operation is built based on grey fuzzy comprehensive evaluation which combined with the grey cluster theory and the fuzzy algorithm. At last, the numerical example is shown to verify the feasibility of the grey fuzzy comprehensive evaluation method.

Abstract: In this paper, a supplementary index, Equal Area Stability Margin (EASM), is proposed to evaluate the system strength for ac-dc interconnected system at sending end. This index can reflect the dynamic characteristic of the interconnected system. Therefore, EASM can be an effective supplement to SCR to evaluate the system strength for ac-dc interconnected system at sending end. Moreover, the solution method of EASM is also analyzed in this paper. Case study indicates the validity of this index.

Abstract: Heffron-Philips model including excitation reactive current compensation (RCC) is set up, impact analysis of RCC on the stability of power system is carried out by theoretical analysis and time domain simulation. Analysis results show that positive RCC increases damping torque while reduces synchronous torque; negative compensation increases synchronizing torque while reduces damping torque, and this phenomenon is more obvious in heavy load. Combined with the actual situation in Sichuan power grid, the role of negative RCC to increase transient stability and provide dynamic reactive power for emergency HVDC power support is analyzed, also negative RCC's influence on the damping characteristics in Sichuan power grid is evaluated.

Abstract: This paper expatiates on the transfer characteristics of current transformer (CT) affected by DC bias. It explains the causations and approaches of the DC bias established, base on equivalent circuit models, electromagnetic equations and results of test analyze the effects of CT by DC bias. Result indicates that, the DC bias current will move error curve of instrument CTs to negative coordinate, and accelerate initial saturation time of protective CTs. Finally, simulation has been done to prove theory analysis. The presented result provides consultation for proper selection of both instrument and protective CTs.

Abstract: This paper presents a new procedure for allocating transmission losses to generators and loads. Based on the superposition theorem, the paper proposes that electrical power flow in transmission line can be separated into a series of power component induced by each individual power supplies, and transmission line power losses can be separated into a series of power loss component induced by each individual power supplies. Thus, each power supplys contribution to the branch power loss is resolved. Based on the theory founded above, corresponding loss allocation model is established. Results illustrate the validity and rationality of the new allocation process with expected results.