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This paper analyzes Henan power circuit breakers with closing resistors operation. Selecting a typical substation as the research object, switching overvoltage and surge arrester energy absorption were simulated without the closing resistor. Measured through the field test verified the accuracy of the simulation. The relations between line length and over-voltage level was also analyzed. The result...
Microgrid has lots of advantages and effective methods in usage and control of DGs, and has developed rapidly at each country. Electric Vehicles regarded as new traffic method has been paid more common attention. Batteries of electric vehicles can be regarded as mobile power storage devices, which will affect the stability of the power grid when paralleled in the grid. A common structure of the microgrid...
Nowadays, most of the electrical railway tractions, especially the high-speed tractions are using AC-DC-AC power driving system. The best choice for the AC-DC link is four-quadrant PWM rectifier, which can provide controllable DC link voltage and better power factor for the grid. In high power drive applications, the switch frequency of the power semiconductor device cannot be very high, usually less...
Stability issues are a major concern in railway grids. Although these problems are most experienced in 16.7-Hz applications, low-frequency oscillations also occur in 50-Hz railway grids. In this paper, an advanced multivariable control concept is presented. Beside achieving very good dynamic behavior, the approach improves the introduced stability problem. The proper operation of the control is verified...
Economical and ecological motives are pushing shoreside power supply by power electronics systems for merchant ships as well as for cruise ships. Also, final tests of on-ship power systems and generation are simplified considerably. Fault scenarios on-ship and within the harbour grid and the variability of the parameters of on-ship distribution - each ship is special, and large consumers or generators...
Stability aspects are a major concern in railway-traction applications. It is well-known that low-frequency oscillations occur in 16.7-Hz railway-grids. They can be initiated either by impedance variation or by multiple traction vehicles active in one feeding section. This paper focuses on the emulation of many traction vehicles starting up in the same feeding section and hereby causing instability...
This paper explores the performance of alternative voltage control strategy applied to direct drive synchronous wind generators, more specifically with permanent magnetic (PMSG). The reactive power control of the grid-side converter is investigated for voltage control purposes. In Brazil, the Grid National Operator (ONS) requires that wind turbines stay connected to the grid during voltage dips, but...
Due to growing competition in the electricity market, the drive for efficient, stable and secure grid operation makes voltage control in the transmission grid relevant. A solution that has potential is to increase the effectiveness of the ancillary service by automatic fast control. The paper describes a Wide Area Voltage Regulation (V-WAR) that fits this framework. The V-WAR is based on Secondary...
In this paper, a new power sharing control method for a microgrid with several distributed generation units is proposed. The presence of both inertial and non-inertial sources with different power ratings, maximum power point tracking, and various types of loads pose a great challenge for the power sharing and system stability. The conventional droop control method is modified to achieve the desired...
This paper proposes a new extended boost quasi Z-source inverter (ZSI) and a simple modulation and control method based on one-cycle control for controlling a grid connected PEM fuel cell energy system. ZSIs are gaining popularity. Similarly one-cycle controllers are becoming popular due to their simplicity, ease of implementation and fast response. However, this control method has not been developed...
This paper proposes an improved current control scheme for the rotor-side converter of a doubly-fed induction generator (DFIG) wind power generation system. The control scheme consists of a proportional (P) controller and a harmonic resonant (R) regulator tuned at the grid frequency. Thus, the positive and negative sequence components of rotor current are fully regulated by the PR controller without...
Voltage sag caused by induction motor starting is one of the main causes resulting in sensitive equipment dropout. A simulation model of Dynamic voltage restorer (DVR) has been proposed to mitigate voltage sag caused by high-power induction motor starting. The relationship of starting current and voltage sag depth has been discussed in this paper. Based on these analyses, a control strategy, associating...
This paper presents a new predictive direct power control (DPC) strategy for three-phase grid connected voltage source converters with constant switching frequency. Source and converter flux are introduced to develop the power flow model of such system. Based on the predictive power model, the output converter voltage vector in each PWM period can be calculated directly. The detailed power variations...
This paper describes the configuration and control methods of wind power not connected to AC grid, but directly to DC loads in large wind farms. In order to balance the power in the bus, energy-storage units are introduced. When DC power does not balance in DC bus, voltage spikes and voltage level rising will appear in the DC bus, which are destructive to the electronic devices. The methods of restricting...
This paper discusses a control strategy of direct-drive permanent magnet wind power system, and proposes back-to-back PWM converter control method that PWM technology is employed both in generator-side and grid-side. The system consists of permanent magnet synchronous generator (PMSG), PWM rectifier in generator-side, intermediate DC circuit, and PWM inverter in grid-side. DC voltage control is used...
DC injection is a critical issue in the distributed generation systems according to IEEE Std. 1547-2003. Unfortunately, few literatures discuss this problem. In this paper, a novel control strategy is proposed to achieve zero steady-state DC injection. The proposed idea stems from a well-known fact that a capacitor can block DC component naturally. Generally, this capacitor should be large enough...
This paper presents the analysis and operation of doubly fed induction generator (DFIG)-based wind power generation system under unbalanced network voltage conditions. The limited voltage and current ratings, the control capabilities of both the grid-side and the rotor-side converter (GSC & RSC) for unbalanced network voltage compensation are investigated in detail. A new current control scheme,...
For the mathematical model of PWM inverter under the d-q rotary coordinate system, there exists coupling between the active current and reactive current, which makes it difficult manipulating the power injected into AC grid from distributed generation system. So as to handle the problem, a novel current decoupling strategy based on the input-output linearization is employed in the paper and the PI...
This paper proposes a new HVDC (High-Voltage DC) transmission topology, its modeling and control method, used for large doubly-fed induction generator (DFIG)-based offshore wind farms. The sending end is a line commutated converter (LCC) with a STATCOM (Static Compensator) while the receiving end is a current source inverter (CSI) using IGBTs. The STATCOM provides stator voltage support for DFIGs,...
An electrical balance of plant(E-BOP) of a 600 kW molten carbonate fuel cell (MCFC) has to transit from grid-connected(GC) mode to grid-independent(GI) mode when a grid is in a fault conditions. A minimum transition time is limited by four cycle for a 600 kW MCFC to ride through a grid fault. In this paper, we propose a control algorithm of a 600 kW E-BOP for a MCFC system. The E-BOP has three operation...
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