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Digital-analog hybrid simulation method combines the advantages of both real-time digital simulation and physical simulation, and will be an effective means for the simulation and analysis of future power system. However, the ideal transformer model (ITM), as the most widely used interface algorithm, is easy to encounter instability issues. A novel impedance compensation algorithm based on ITM is...
The problem of control system design is discussed for a high frequency DC-DC converter which is based on the push-pull circuit with autotransformer. The proposed converter may be used as a battery discharge unit in power supply system of satellites. The mathematical model of the converter is described. The proportional-integral (PI) current controller and PI voltage controller are designed based on...
In this paper, the simultaneous trajectory tracking of the speed and the flux state variables of induction machines is realized. Nonlinear feedback control laws are designed to make both the rotor speed and the flux variables reach the desired nominal values in finite time. In this study, the speed, the stator currents, and the flux are assumed to be available for measurement. Numerical simulations...
Future Flexible HVDC Transmission Systems will consist of several active and passive infrastructures including DC Power Flow Controller (DC-PFC) device. The addition of the DC-PFC to the future Multi-Terminal HVDC (MT-HVDC) grids arises some key concerns such as stability, system interoperability, and possible adverse interactions. Hence, a suitable model is necessary to conduct deep frequency domain...
The paper proposes a hybrid droop control strategy to enhance the stability and increase maximum constant power loads (CPLs) capability of DC microgrids in a realistic scenario. By capturing the detailed model of inner control loops and hybrid droop control and general dc MG topology, a thorough comparative study is conducted between traditional droop control and hybrid droop control. Enhanced control...
Rapid growing on the power level of renewable generation units leads to that using more adaptable and flexible control techniques in this units becomes more important for grid operators. In this paper, after introducing Renewable Static Synchronous Generation Units (RSSGU) as units with flexible dynamics capability, forming of renewable Virtual Power Plants based on this RSSGUs (VPP-SSG) is suggested...
A novel load current sharing method is proposed for multi-module LLC resonant converters in high power application in this paper. The paralleled system is controlled by the maximum current sharing method to achieve load sharing automatically. Moreover, a series inductor is connected to each LLC output side to restrain the current ripple of double switching frequency. The maximum current sharing method...
DC (Direct Current) microgrid has gained more attention caused by the development of distributed generations and DC loads. The control objectives for DC microgrid are voltage regulation and current sharing. In order to achieve these objectives, consensus based control methods with communication have been extensively studied recently. It is a common strategy to modify the voltage set point of local...
Small-signal models of impedances for grid-tied converters have recently attracting researchers' attention and shown of great importance in stability analysis. This paper proposes the impedance model in d-q frame for STATCOMs, including dynamics from synchronization, current and voltage loops and reveals the significant features compared to other types of grid-tied converters that the 1) grid impedance...
The high R/X ratio of distributed lines in low voltage microgrid causes the coupling between the active and reactive power control. Forcing the output impedance to achieve the decoupling through additional virtual inductor impedance loop heavily causes the voltage amplitude drop at the point of common coupling. Such voltage drop deteriorates the microgrid voltage stability. To avoid the problem of...
In DC microgrid, it is common that constant power loads (CPLs) exhibit negative impedance characteristics, which degrades the stability margin of the whole system. This paper focuses on the stability problem of isolated DC microgrid with multiple DC voltage control units and constant power loads. Taking controllers into account, the detailed impedance model of DC microgrid is established, and it shows...
For the effective operation of series input modular systems, it is essential to maintain input voltage sharing (IVS) or keep output voltages/currents constant (OVC/OCC). This paper investigates the steady state performance of the series input multiple outputs (SIMO) system. Based on small signal analysis, the inherent instability mechanism of OVC/OCC control strategies is revealed. Since ensuring...
Designing a control system for an induction motor (IM) is a generally twofold task: (1) controller synthesis and, (2) assessment of its stability. When using the full fifth order dq-frame model, with incomplete state information and unknown disturbances, the controller design and the proof of stability are not trivial tasks. In this paper, we propose a speed controller for the IM using a reduced-order...
Grid-connected converters have been widely used in distributed generations. However, the resonance brought by converters in weak grid has been a great threat to system stability. Impedance-based method provides a powerful tool for stability analysis. Active damping is also widely applied to improve system stability. This paper derives the impedance model of grid-connected converter system and analyzes...
In cascaded-type microgrid, the synchronization and power sharing of distributed generators (DGs) become two new issues that needs to be addressed urgently. In this paper, a unified droop control is proposed and its stability is analyzed in the islanded mode. The proposed scheme can ensure the system stability and accurate power sharing without communication in four-quadrant operations. Finally, simulation...
This paper develops a distributed cooperative control scheme for DC microgrids with time-varying coupling delays in noisy environments. The proposed distributed cooperative control, consisting of distributed primary control and secondary control, will regulate the voltage of microgrids to the desired values and through a sparse communication network with asymmetric communication delays and noise disturbances...
The optimal planning of distributed photovoltaic system is conducive to reducing the adverse impact of high-permeability random access on power distribution systems. In this paper, a optimization planning model of locating and sizing of distributed photovoltaic power generation system is established to improve the permeability of PV system on the premise of the safe operation of the power system,...
This paper investigates the effect of wind speed variations on the small-signal stability of doubly-fed induction generator-based wind turbines equipped with modified virtual inertial controllers (MVIC). MVIC is a control scheme that prudentially emulates the inertial response of the conventional synchronous generators for wind turbines in order to improve their frequency control performance. It also...
In this paper, a new control approach is proposed for PV system with hybrid energy storage system (HESS) in isolated DC grid application. The proposed control approach solves the current controller conflict problem in HESS and provides faster DC link voltage restoration. In the proposed control approach a predictive term is used to control the battery current and the supercapacitor (SC) current. In...
The accuracy and stability are two fundamental concerns of the visual servoing control system. This paper presents an enhanced image based visual servoing (IBVS) method which can increase the accuracy of visual servoing with guaranteed stability. The proposed controller combines PD control with sliding mode control (SMC) for a 6DOF manipulator. Specifically, the main benefits of this approach lie...
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