The GaN HEMT offers fast switching and low on-state resistance which makes it ideal for applications such as high efficiency and high power density power supplies. Unfortunately, the low threshold voltage makes GaN HE...
详细信息
ISBN:
(数字)9781728153018
ISBN:
(纸本)9781728153025
The GaN HEMT offers fast switching and low on-state resistance which makes it ideal for applications such as high efficiency and high power density power supplies. Unfortunately, the low threshold voltage makes GaN HEMT extremely vulnerable to false turn-on, which compromises the performance and potentially causes shoot-through. In the half-bridge circuit topology, the resonant circuit formed by the parasitic inductance and capacitance can trigger false turn-on with a fast commutation. A practical method to avoid this phenomenon is to apply a negative bias voltage during the commutation by either using a separate power supply or using a capacitor charge pump to produce the negative turn-off bias. The first method necessitates many extra components and the second method cannot provide a fixed negative voltage. This paper rectifies these issues by proposing a negative turn-off bias generator with a new charge pump based approach which offers a stable negative turn-off voltage under different switching frequencies and duty cycles. The proposed circuit has been practically implemented during experimental testing. These results demonstrate that false turn-on events are eliminated without compromising the high-frequency and highspeed characteristics of the GaN HEMT.
With the large-scale integration of distributed generations (DGs), a centralized control approach is being challenged concerning communication efficiency, resiliency to communication failure, privacy, and scalability....
详细信息
ISBN:
(纸本)9798350399677
With the large-scale integration of distributed generations (DGs), a centralized control approach is being challenged concerning communication efficiency, resiliency to communication failure, privacy, and scalability. An autonomous decentralized control for DGs in distribution networks is proposed to ensure privacy while also reducing the computational burden. Meanwhile,a multi-agent reinforcement learning method considering privacy protection constraints is developed to solve the autonomous decentralized control problem. The effectiveness of the proposed control method is verified by the numerical example of the modified 141-bus distribution system test_feeder.
China AC-DC powersystems are interconnected to form a huge power grid. The nanoseconds, microseconds, milliseconds electromagnetic transient were generated due to AC-DC system operation and fault, the DC converter va...
详细信息
China AC-DC powersystems are interconnected to form a huge power grid. The nanoseconds, microseconds, milliseconds electromagnetic transient were generated due to AC-DC system operation and fault, the DC converter valve movement, the load generated by changes in the interaction of AC-DC interconnected system electromagnetic transient, which can pose a hazard on AC and DC powersystems, in particular, can lead to the commutation of DC system failures and atresia such serious incidents. Based on the broadband characteristics model which can accurately reflect the existing AC-DC interconnected system electromagnetic transient characteristics of the key components, we applied the PSCAD/EMTDC platform to establish a computational model, and revealed DC side electromagnetic transient interaction on AC side. The results show that the DC system has little effect on AC system electromagnetic transient, In various types of failures, the overvoltage produced at side of 750 kV, 330 kV lines and bus are in the allowable range.
Huge interconnected power grids are formed in AC and DC powersystems in China. The nanoseconds, microseconds, milliseconds electromagnetic transient due to AC and DC system operation and fault, the DC converter valve...
详细信息
Huge interconnected power grids are formed in AC and DC powersystems in China. The nanoseconds, microseconds, milliseconds electromagnetic transient due to AC and DC system operation and fault, the DC converter valve movement, the load generated by changes interact in the AC and DC interconnected system, impairing AC and DC powersystems, especially leading to the commutation of DC system failures and atresia such serious incidents. Consequently, a theoretical analysis was combined with a test method to establish an over ground network, considering DC electrical networks, controlsystems and underground grounding system of the full-wave process of the UHV system, Finally, converter transformer was modeled with UMEC model, and transmission line was modeled with J-Marti frequency dependent model;moreover, valve was modeled with transistor, RLC circuit, and other units including DC controller, and DC filter and AC filter were modeled with RLC circuit. The broadband characteristics of electromagnetic transient models of key units in DC sides for the analysis of AC and DC interconnected system were also analyzed.
For some domestic large thermal power plants delivering electric energy over long distances, the sub-synchronous resonance (SSR), which is induced by the fixed series compensation (FSC), attracts much attention. Eigen...
详细信息
For some domestic large thermal power plants delivering electric energy over long distances, the sub-synchronous resonance (SSR), which is induced by the fixed series compensation (FSC), attracts much attention. Eigenvalue analysis is one of the primary methods to assess the risk and explore the countermeasure. However, for handling multi-machine and multi-mode SSR problems, no practical toolkit based on eigenvalue analysis is on hand for the moment. In this paper, a systematic modeling approach and analysis flows for the purpose of eigenvalue analysis of multimachine plant-to-grid transmission systems with FSC were proposed. The equating technique of machines and networks was presented, and the effect of the q-axis damping windings on the SSR was also explored. The applicability of the proposed method was verified with an actual multimachine system. Furthermore, its advantage over existing SMIB based eigenvalue analysis was clarified by a comparative study between the original multi-machine system and the simplified single-machine system.
In order to better accommodate renewable energy sources (RESs), a general coordinated mechanism for modern power system has been proposed, which is simultaneously appropriate for economic dispatch and market clearing ...
In order to better accommodate renewable energy sources (RESs), a general coordinated mechanism for modern power system has been proposed, which is simultaneously appropriate for economic dispatch and market clearing under the current structure of wholesale markets. In which, the system operator can achieve a global optimum under uncertainties by investing independent aggregators (IAs) with better autonomies on trade-offs between expected profits and risks. Meanwhile, IAs with RESs are free to model their internal uncertainty in a heterogeneous manner and integrate the local information into tailored bids without revealing privacy. Moreover, a parametric-programming-based distributed (PPD) algorithm is designed to support the once-daily communication mechanism. The case studies validated the performance of the proposed mechanism.
Along with the power fluctuation and other problems caused by large-scale grid connection of renewable energy, electrochemical energy storage has been widely concerned by researchers. Firstly, the technical characteri...
Along with the power fluctuation and other problems caused by large-scale grid connection of renewable energy, electrochemical energy storage has been widely concerned by researchers. Firstly, the technical characteristics and application scenarios of important electrochemical energy storage are summarized in this paper. Then the analysis focus on the evaluation indexes of the economic and social benefits of electrochemical energy storage on the generation side, grid side and user side. Finally, in order to adapt to the landing of carbon peaking and carbon neutral targets, and combined with the implementation of time-sharing tariffs, energy storage planning problems that need further in-depth research are proposed in view of the shortcomings in existing energy storage planning studies, which are of great significance for improving the adaptability of subsequent energy storage planning studies.
Combined with a single circuit UHV power transmission project in one million voltage from Jincheng to Jingzhou via Nanyang which is reasoned by State power Grid Corp. of China, its switching overvoltages, including th...
详细信息
Combined with a single circuit UHV power transmission project in one million voltage from Jincheng to Jingzhou via Nanyang which is reasoned by State power Grid Corp. of China, its switching overvoltages, including three-phases closing with no load and single-phase auto-reclosing, are considered. The switching overvoltages are calculated with Electromagnetic Transient Program (EMTDC). The calculation shows that the switching overvoltage is too high up to 1.80 pu if only with parallel resistor in circuit breaker or high performance ZnO arrester. Combining arrester and parallel resistor is a good measure to limit switching overvoltage without such high requirement on arrester's or resister's thermal capacity.
The cumulative installed capacity of wind power worldwide has grown rapidly in recent years. Fixed reactive powercontrol is adopted by wind turbines (WTs) to receive cycle instruction of wind farm (WF) automatic volt...
详细信息
This study investigated the air-gap magnetic field distribution and inductance characteristics of a long primary sectional powered variable pole pitch linear induction motor (VPPLIM). A one-dimensional analytical mode...
详细信息
暂无评论