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In the conventional variable speed drive, the dc-link including the dc-choke and electrolytic capacitor is bulky with limited lifetime. The slim dc-link drive is thus proposed for the lower cost and longer lifetime by using the film capacitor to replace the electrolytic capacitor and dc-choke. However, such drive system suffers from the potential instability issue, due to the negative incremental...
A large amount of distributed generation is connected to the grid, reducing rotational inertia of the power system. Based on the Static Synchronous Generator Model, inertia controller is introduced on outer voltage loop in this paper to enhance grid inertia. The developed inertia controller can generate inertial current superposed in conventional current reference. The inertial current can be adjusted...
This paper discussed the tuning process of the power system stabilizer (PSS) for a nuclear turbine-generator excitation system. By measuring the non-compensated phase-frequency characteristic of the excitation without PSS, and through calculation and critical gain test, the PSS parameters are determined. Through step response and anti-regulation experiment, the effectiveness of the PSS is verified.
Grid-connected inverters equipped with LCL filters are very popular in utility applications for their better power quality features, while the LCL resonance may threaten system stability. To dampen the LCL resonance, the widely used active damping method is based on the proportional feedback of the filter capacitor current. However, it has been revealed that when the LCL resonance frequency is above...
STATCOMs provide grid with not only reactive power compensation but auxiliary stability support through exerting influence on the dynamic behavior of Synchronous Generator (SG) during grid power oscillations. In this paper, method of electrical torque analysis is utilized to analyze the mechanism of STATCOM affecting the transient performance of SG when operates in power oscillations suppression mode,...
A compact 2-terminal, series-pass active damping circuit utilizing semiconductor device is proposed. It is implemented with linearly-operated device such as MOSFET using current feedback control at very low dropout voltage. The damping device features a simple internal structure and is connected in series with a generic switching mode power supply (SMPS). It can damp unwanted oscillation due to the...
The recently proposed concept virtual synchronous generator (VSG) has been intensively researched. Its core idea is to add a segment in traditional inverter control to simulate synchronous generator's rotor motion characteristic so that the distributed energy resources (DER) can have virtual inertia. VSG control usually contains output current amplitude limiting part to avoid too large current from...
Virtual synchronous generator (VSG) has been developed recent years as a promising grid-tied inverter control strategy because it can improve the penetration of the renewable energy. Due to introducing virtual inertia, the active power loop of VSG behaves as a typical second-order system, which may cause active power oscillation. It is a key issue that designing the parameters of active power control...
In this paper, a sensorless active damping scheme of LCL-filter is proposed in grid-connected parallel inverters for battery energy storage systems. The proposed damping method is superior to the conventional notch filter and virtual damping methods with respect of robustness on the variation of resonance of the filter and unnecessary additional current sensors. The theoretical analysis of the proposed...
This paper presents a mitigation strategy to reduce the risk of Subsynchronous Controller Interaction (SSCI) in Doubly-Fed Induction Generator (DFIG) based wind farms. SSCI mitigation is achieved through the modification of the controller structure within the DFIG turbine. A proportional damping controller tuned to the SSCI oscillatory frequency is proposed and implemented in the current controller...
To improve reliability of micro-grid system without energy storage, a maximum power point tracking (MPPT) algorithm considered spinning reserve capacity was proposed. Using implicit curve fitting method, the algorithm set aside 10% of PV array's maximum output power as spinning reserve of distributed generation (DG), and tracked maximum power point of load in real simultaneously. Moreover, to improve...
This study examines the P+ multi resonant based voltage control for the voltage harmonics compensation under the islanded mode of a microgrid. In islanded mode, the inverter is defined as a voltage source to supply the full local load demand without a connection to the grid. On the other hand, the output voltage waveform is distorted by the negative and zero sequence and current harmonics due to the...
The LCL-filter is one of the methods to reduce the size of the filter inductor but it leads to resonance in the system. The resonance usually results in unstable system and triggers the over-current protection. An active damping technique based on the virtual resistor is provided in this paper. The concept and the mathematical analysis of the proposed method are explained, and then the stability of...
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