The double closed loops control strategy composed of inner current loop and outer voltage loop in the d-q synchronous frame is a relatively common control strategy of the three-phase voltage-sourced PWM rectifier. The...
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The double closed loops control strategy composed of inner current loop and outer voltage loop in the d-q synchronous frame is a relatively common control strategy of the three-phase voltage-sourced PWM rectifier. The system can not be completely decoupled because of the variable inductance in the actual system. And for simple, the decoupled part of the controller is usually ignored. What's more, the equation of the outer voltage loop is nonlinear. According to the analysis of the model of the rectifier, a novel double closed loops control strategy composed of inner current loop in the complex vector and outer square of the voltage loop, is proposed. The inner current loop using the mentioned control strategy can be completely decoupled without the exact value of the boost inductance, and the equation of the outer square of the voltage loop is linear. From the results of the simulation, the mentioned control strategy can greatly improve the dynamic and static of the system.
Severe voltage imbalance during the turn-off transient can be observed when Connecting low-voltage power devices in series to block much higher DC-Link voltages. In all existing solutions, adjusting driving signals ti...
ISBN:
(数字)9781728148298
ISBN:
(纸本)9781728148304
Severe voltage imbalance during the turn-off transient can be observed when Connecting low-voltage power devices in series to block much higher DC-Link voltages. In all existing solutions, adjusting driving signals time delay (ADSTD) is attractive and has no penalty of sacrificing switching performance. Typically, bulk snubbers are introduced to eliminate the voltage imbalance during the tail current period of insulated gate bipolar transistor (IGBT). Fortunately, instead of using snubbers, the voltage imbalance caused by the tail current can be solved by using ADSTD as well. In this paper, an active voltage balancing control based on ADSTD is proposed and verified by experiments. Indeed, even without the snubbers, the proposed method works well and has no penalty of introducing additional snubber losses or sacrificing switching performance of IGBTs.
Honeywords is a simple and efficient method that can help the authentication server to detect password leaks. The indistinguishability between generated honeywords and real passwords is the key to the honeywords gener...
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Controllable reactors (CR) are general FACTS (Flexible AC Transmission System) apparatuses, which have played a crucial role in improving the power flow distribution of the system, adjusting the reactive power balance...
Controllable reactors (CR) are general FACTS (Flexible AC Transmission System) apparatuses, which have played a crucial role in improving the power flow distribution of the system, adjusting the reactive power balance of the power grid, stabilizing the voltage, and improving the stability of the system. This paper summarizes the characteristics of various types of controllable reactors, classifies reactors with different structures, and compares different controllable reactors from the perspectives of reactance change, response speed, harmonic problem, and control accuracy. A transformer-type controllable reactor based on flux compensation is proposed, the design scheme of secondary side multi-winding is adopted to realize the large-capacity reactor, the unity of single control winding and multi-control winding in the application is expanded, and the general principle of controllable reactor is obtained through the control of the “linear two-port network” port, and the design principle of such reactor is summarized.
Power exchange between vehicle and grid by bidirectional inductive power transfer (BIPT) system. This paper proposes a dual-side three-stage asymmetrical phase shift (TAPS) control strategy to achieve a high transmiss...
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ISBN:
(纸本)9781665448178
Power exchange between vehicle and grid by bidirectional inductive power transfer (BIPT) system. This paper proposes a dual-side three-stage asymmetrical phase shift (TAPS) control strategy to achieve a high transmission efficiency with zero voltage switching (ZVS) in a wide range of load. With the proposed dual-side TAPS strategy, asymmetrically adjust the amplitude of the ac fundamental excitation voltage with three adjacent control periods as a waveform period. A wide ZVS range and a high system power factor can be realized simultaneously. In addition, when the load is light, the number of switching actions is significantly reduced. The control scheme for the full bridge of both sides is presented, which realizes both optimization of transmission efficiency and zero-voltage switching operation for all power switches. Simulation are performed to compare the effects of triple-phase-shift (TPS) strategy and proposed TAPS strategy on the transmission efficiency, which shows that the system with proposed TAPS control strategy realizes a higher transmission efficiency in a wide range of load.
As Type-3 wind turbine (WT)has already become a vital source in power system, analyzing its fault current is necessary. Although phase-angle jump of stator voltage always occurs during short circuit, it is neglected i...
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ISBN:
(纸本)9781728116129
As Type-3 wind turbine (WT)has already become a vital source in power system, analyzing its fault current is necessary. Although phase-angle jump of stator voltage always occurs during short circuit, it is neglected in existing research and the influence of phase locked loop (PLL)on fault current is still unclear. In this paper, an analytical model of Type-3 WT considering both magnitude drop and phase-angle jump is first developed. Then, the variable-frequency phenomenon of fault current component is discovered by comparing the results of modal analysis and Hilbert-Huang Transformation (HHT). Moreover, the dominant branch causing this phenomenon is extracted so that the whole system can be decomposed into a linear subsystem and a nonlinear subsystem. Based on these subsystems, an analytical expression of fault current is deduced and validated. The conclusion of this paper indicates that the variable-frequency phenomenon may result in protective relays' maloperation.
This paper proposed a new class of motor controller topology - the series-end winding topology. This type of topology combines low cost and high performance. For a N-phase topology, it only contains N+1 bridge leg. An...
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This paper proposed a new class of motor controller topology - the series-end winding topology. This type of topology combines low cost and high performance. For a N-phase topology, it only contains N+1 bridge leg. And it has full current control freedom and high DC voltage utilization. By changing the winding series sequence, the DC voltage utilization of the proposed five-phase series-end winding topology can reach 2. At the same time, the relationship between the series-end winding topology and the open-end winding topology is explained, and the principle of zero-axis voltage elimination is also clarified. The series-end winding topology can be used as a complement to traditional half-bridge topologies and open-end winding topologies.
The reliability of relay protection in smart substations is of great significance. However, the current research methods for relay protection reliability have certain limitations. Solely using reliability block diagra...
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ISBN:
(数字)9798350349030
ISBN:
(纸本)9798350349047
The reliability of relay protection in smart substations is of great significance. However, the current research methods for relay protection reliability have certain limitations. Solely using reliability block diagram (RBD) methods cannot provide a sufficient amount of reliability indicators. Furthermore, research on the reliability of duplicated protection has not taken the impact of the independence between redundant configuration components into account. Based on the specific technical implementation of transformer protection in smart substations, this paper proposes a reliability evaluation method based on reliability block diagram and the Monte Carlo method. This method is used to obtain reliability indicators such as system unavailability, failure frequency, and mean time to failure. A comparative analysis is conducted between single transformer protection and dual transformer protection, and the component importance of secondary equipment in the transformer protection system is provided. The effectiveness and practical significance of the proposed method are verified through numerical examples.
The absorption properties of two dimensional plasmonic room temperature terahertz detectors based on semiconductor heterostructures under external magnetic field up to 10 tesla are compared for the AlGaAs/GaAs, SiGe/S...
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The absorption properties of two dimensional plasmonic room temperature terahertz detectors based on semiconductor heterostructures under external magnetic field up to 10 tesla are compared for the AlGaAs/GaAs, SiGe/Si/SiGe and GaN-based materials. The magnetic field provides a way for frequency tunability in the detection process. By sweeping the magnetic field, grating period and aspect ratio, and the barrier thickness, the absorption spectrum is optimized in the frequency range 1 ~ 5 THz.
Free electron laser Terahertz source (FEL-THz) has significant advantages, such as wide and continuously adjustable spectrums. A compact terahertz source is desired to reduce the cost and space but still provide high-...
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ISBN:
(数字)9781728196596
ISBN:
(纸本)9781728196602
Free electron laser Terahertz source (FEL-THz) has significant advantages, such as wide and continuously adjustable spectrums. A compact terahertz source is desired to reduce the cost and space but still provide high-quality terahertz beams. However, the space constraints requires all the magnets should be downscaled as well. In this paper, a combined-function corrector is designed, capable of providing vertical and horizontal correction at the same time. Poisson and Opera-3D have been used to design and optimize the magnet. The vertical correction is mainly performed by shimming and trimming the magnetic pole head, and the horizontal correction is mainly performed by adjusting the current coil. As a result, the good field range of the vertical field and the horizontal field reach the expected value, and the relative error of the integrated field meets the requirements of beam correction.
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