The effects of manganese dioxide (MnO 2 ) additives on the electrical characteristics of the Al-doped ZnO varistors are investigated. The leakage current densities of the samples decrease first and then increase again...
详细信息
The effects of manganese dioxide (MnO 2 ) additives on the electrical characteristics of the Al-doped ZnO varistors are investigated. The leakage current densities of the samples decrease first and then increase again with the increase of the amount of MnO 2 additives. Correspondingly, the nonlinear coefficients of the samples keep on increasing and then decrease. In addition, the donor densities increase monotonously with the amount of the doped MnO 2 increasing. The effects of MnO 2 additives on the electrical characteristics of the samples are different from the conclusion of previous literatures. The reasons of the distinct effects are supposed to be related with the donor and interface state densities of the samples.
Recently, several power grids of China came across low frequency oscillations which are difficult to explain by the traditional negative damping mechanism. Some researchers suggest that those oscillations be caused by...
详细信息
Recently, several power grids of China came across low frequency oscillations which are difficult to explain by the traditional negative damping mechanism. Some researchers suggest that those oscillations be caused by external periodic disturbances according to the forced oscillation mechanism. It takes no doubt that the oscillation source location (means locating the disturbances) is imperative and decisive to eliminate such a kind of oscillations. This paper proposes a location methodology based on Energy Supply on Port derived from the Port-controlled Hamiltonian theory. By calculating the energy injected to the network at corresponding ports, the oscillation sources can be effectively located, even in complicated systems containing various kinds of control devices such as governors and exciters. Different from the traditional methodology based on eigen-analysis, the proposed methodology is naturally decentralized without the dependency on global measurements. Case studies on the standard 4-machine 2-area system and the IEEE-118 bus system show the effectiveness and efficiency of the proposed methodology.
Neither electromechanical transient stability analysis (TSA) program nor electromagnetic transient (EMT) programs can be used individually for the transient stability studies of the large scale AC/DC systems. This pap...
详细信息
In China, coal is a dominant component of energy mix, and it is expected to remain as such over the next 30 to 40 years. Coal is expected to be used even more in powergeneration. The direct combustion of coal already...
详细信息
In China, coal is a dominant component of energy mix, and it is expected to remain as such over the next 30 to 40 years. Coal is expected to be used even more in powergeneration. The direct combustion of coal already has been causing severe pollution and ecological degradation, and it is quite difficult to address the need to reduce greenhouse gas (GHG) given the direct combustion of coal. Therefore, the polygenerationsystem based on coal gasification, which is one of the major examples of synergistic utilization of coal, is proposed. It is a comprehensive solution to meet the energy challenges China is facing. Furthermore, the synergy of fossil fuels (especially coal) with renewable energy, the synergy of different kinds of energy for energy storage, the synergy of centralized and distributed supply of different kinds of energy, and the synergy of different kinds of energy in smart energy grid (power, gas, heat, and water) are the keys to making China a low-carbon economy. Carbon dioxide (CO2) mitigation in China should begin from the coalchemical industry given their accumulated relevant experiences. The mitigation process should gradually be transformed into the 'IGCC + polygeneration + CCUS'.The objectives of this paper are to describe the synergistic utilization of coal, and to analyze the synergy of coal with other energy resources, and to propose the scientific and technological problems to achieve these synergies.
The key parameters of SOA (safe operating area) of semiconductor devices are hard to be measured when converter is operating, which is not helpful to protect converter at any time. On the other hand, surplus estimatin...
详细信息
Hard-switching technique under the high voltage and high current is one of main trends of high power inverters. Under this switching mode, the stray parameters of the commutating loops, especially the stray inductance...
详细信息
This paper presents a predictive control scheme of DC-link voltage for back-to-back converters based on energy balance modeling. Since the variation of DC-link voltage is affected by the energy mismatch between rectif...
详细信息
Condition classification has been widely used for assessing equipment status for machine condition monitoring and diagnostics. An engine was fitted with one temperature and two pressure sensors to study the machine co...
详细信息
This paper discusses period properties of some linear maps which are employed in various applications such as image encryption, public key cryptography and watermarking. Conditions for the bijectiveness of such maps a...
详细信息
This paper discusses period properties of some linear maps which are employed in various applications such as image encryption, public key cryptography and watermarking. Conditions for the bijectiveness of such maps and the existence of a period are presented. Period structure is also given. Then, the recurrence equation theory is adopted to address the period distribution problem. Finally, a framework to solve the problem is proposed with a demonstration of its effectiveness and efficiency into some applications.
Grid-connected LCL filter of voltage source PWM rectifier (VSR) can not only reduce the values of inductance, improve the system dynamic response, but also reduce the cost. However, LCL filter brings stability problem...
详细信息
暂无评论