To design and analyze the behavior of high power inverter, the definition and application of the inverter's own safe operating area (SOA) are presented in this paper. The relation between the switch devices behavi...
详细信息
To design and analyze the behavior of high power inverter, the definition and application of the inverter's own safe operating area (SOA) are presented in this paper. The relation between the switch devices behaviors and the other components of the inverter is playing a key role in the description of the novel SOA. Based on the proposed idea, the optimization of a real 1.25MW/3.3kV inverter equipped with IGCTs is presented and analyzed. The corresponding experimental results are shown.
The reliability level of STATCOM devices is a key issue concerned by all the design department, manufacturing sector and application department. A k-out-of-n: G system model of STATCOM and the basic analysis method fo...
详细信息
The reliability level of STATCOM devices is a key issue concerned by all the design department, manufacturing sector and application department. A k-out-of-n: G system model of STATCOM and the basic analysis method for it are proposed in this paper. The k-out-of-n: G system can be used to quantify the reliability benefit of redundancy units in main circuit of STATCOM. Utilizing the basic reliability indices of IGCT, GTO and IGBT provided by literatures, the reliability value and MTTF of an applied 50 MVA STATCOM device are evaluated. And the optimal redundant unit count is analyzed basing on the indices obtained in forenamed study. Finally the dynamic model is proposed to evaluate the reliability of the k-out-of-n: G system when component failure induces higher failure rates in survivors.
A risk based method is proposed to design under voltage load shedding (UVLS) scheme. Different with traditional methods, the proposed one employs a series of risk indices, which are obtained based on a full-scale cont...
详细信息
A risk based method is proposed to design under voltage load shedding (UVLS) scheme. Different with traditional methods, the proposed one employs a series of risk indices, which are obtained based on a full-scale contingencies analysis, to determine the operating parameters of load shedding. According to this method, the load bus, in which the UVLS can exert itself with the highest efficiency to prevent voltage collapse, is selected as the first candidate to execute load shedding. And the amount of loads to be shed is identified though a relationship between risk values and shedding amount. The selection of shedding time conforms to the principle that the compound risk brought by failed shedding and unexpected shedding must be the minimum. Experiments conducted for IEEE 39-bus system reveal that the proposed method redound to identify the location, amount and time of load shedding more accurately and reasonably due to taking into account a great deal of uncertain factors.
In order to make up the deficiency of traditional analytical method used in the research of voltage stability problem, we need to know the probability information concerned with voltage instability. Therefore, this pa...
详细信息
In order to make up the deficiency of traditional analytical method used in the research of voltage stability problem, we need to know the probability information concerned with voltage instability. Therefore, this paper proposes a method to calculate the probability of voltage instability based on the stochastic characteristic of load margin index. This method firstly determines the stochastic characteristic of load margin index through an analysis about the randomicity of parameters which tie up with the tracing of critical point in continue power flow computation, and then figures out the probability of voltage instability by using moment and cumulate method. Owing to take into account more uncertain factors' influence on the voltage stability, the result acquired by this method is much more accurate and reasonable. A numerical simulation based on IEEE 39-bus system reveals that the proposed method works properly.
The characteristic of the transient response of the grounding system takes on a fast rising and slow damping with the lightning excitation. An improved simultaneous time and frequency domain extrapolation method is pr...
详细信息
The characteristic of the transient response of the grounding system takes on a fast rising and slow damping with the lightning excitation. An improved simultaneous time and frequency domain extrapolation method is presented based on Hermite function expansion, which takes the above mentioned characteristic of the transient signal into account, using early time response and low-frequency data, the complete electromagnetic response is generated. By using mutually complementary data, simultaneous extrapolation in time and frequency domains are carried out by using the Hermite polynomials as the basis function. However, the extrapolation method is not suitable to deal with the transient response with the fast pulse excitation. The improvement for the extrapolation method is to pre- and post-process the transient response data with the fast pulse excitation. As a pre-processed procedure, in order to reduce the condition number of the matrix used for determined the coefficient of basis function, the scale transformation is used in time and frequency domain respectively, and the data in time domain is smoothed and padded with zero. An adaptive algorithm to determine the order of Hermite function is also proposed. As a post-processed step, the transient data are smoothed by using GPOF to obtain a convergent result. The numerical example and the field measurement are presented to illustrate the application of this methodology. The method proposed enhances the ability of the simultaneous time and frequency extrapolation techniques.
The indirect boundary element method has some special advantages for the 3D linear magnetostatic field calculation by using the equivalent magnetic surface charge. In order to improve the accuracy of solutions and dec...
详细信息
The indirect boundary element method has some special advantages for the 3D linear magnetostatic field calculation by using the equivalent magnetic surface charge. In order to improve the accuracy of solutions and decrease the computational costs, an adaptive Galerkin approach to solve the magnetostatic integral equation is presented by using the h-type refinement technology. The basic idea of the proposed approach can be summarized as follows. The error of magnetic flux density is globally minimized in the Galerkin sense in the implementation, so the continuity error of magnetic flux density of each element can be served as a criterion to guide the adaptive refinement. The singularity of geometric corners and edges can be overcome due to the scheme of the discretization of the integral equation with Galerkin's approach. In addition, a local resolution technology is proposed, which leads to the minimal refined unknown. The numerical examples show the proposed method is efficient and accurate by comparison to the analytical solutions and the measured results.
To research the influence of multi-phase winding to generators and calculate the losses in solid rotors, the stator mint of a 12-phase asynchronous generator have been well analyzed and finite element method by ANSYS ...
详细信息
ISBN:
(纸本)7506274078
To research the influence of multi-phase winding to generators and calculate the losses in solid rotors, the stator mint of a 12-phase asynchronous generator have been well analyzed and finite element method by ANSYS software has been applied to get the accurate losses in the rotor through both harmonic and transient 2-D analysis. The relationship between stator harmonic current and stator harmonic mint has been deduced and proved through ANSYS software to some extent, and rotor losses produced by both stator fundamental current and stator total current have also been obtained and compared. The results show that 12-phase stator winding with appropriate short pitch can effectively eliminate or reduce many mmf produced by stator fundamental and harmonic current and rotor losses are mainly produced by stator fundamental current.
To simplify the calculation of winding bar temperature for the condition monitoring of the water cooling stator of Three-Gorge Hydro-Generator, this paper calculates three of two-dimension thermal fields. Using the th...
详细信息
ISBN:
(纸本)7506274078
To simplify the calculation of winding bar temperature for the condition monitoring of the water cooling stator of Three-Gorge Hydro-Generator, this paper calculates three of two-dimension thermal fields. Using the three fields simulates the different section along the axial direction of the generator. The total amount of heat taken away by water can be calculated by weighting the result of three fields on the total axial length of them. Four groups of thermal-fields with different outlet-water temperature are calculated by using ANSYS multi-physical software. The calculation results of temperature of measurement-point between up-layer and down-layer bars in stator are partly supported by the measurement data. And the relatively error between the heat taken by cooling-water and the heat generated by the stator bar is always less than 5%.
In order to detect the abnormal temperature of large oil-Immersed power transformer earlier, this paper presents a new prediction-model of surface-temperature for the transformer to predict the normal surf ace-tempera...
详细信息
ISBN:
(纸本)7506274078
In order to detect the abnormal temperature of large oil-Immersed power transformer earlier, this paper presents a new prediction-model of surface-temperature for the transformer to predict the normal surf ace-temperature. And to compare the difference between the predicted value and the measured value can judge If the condition of the transformer Is fit to operate. The model parameters are estimated from the field data by using the Partial-Least-Square method, which overcomes the instability of results estimated by using the traditional Least-Square method. Furthermore, the appropriate amount of data for the parameter estimation was decided according to the principle of Heat Transfer and the characteristics of the predicted deviation, such as mean, variance and normal distribution. The prediction model is verified from the accuracy of results predicted with one year of field data.
暂无评论