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On high voltage power lines the bare hand method is the commonly used live-line maintenance (LLM) working technology. In different standards and regulations different clearances can be found. Although the calculation of minimal approach distance is similar in each method, it depends on the magnitude of transient overvoltage. To limit the possible peak of overvoltage, portable protective air gap (PPAG)...
This paper addresses the problem of voltage regulation by multiple DC/DC converters and without communication amongst the converters. In DC systems where multiple different energy storage devices need to regulate a common DC bus while executing their individual battery management algorithms, it is necessary to find an automatic mechanism to coordinate how the different converters share the responsibility...
Various fault scenarios have been analyzed by running a number of differently combined 380 VDC microgrid tests. These tests represented a common grid topology with low system impedance at grid resonance points within the single- or lower double-digit kHz range. At serial arc faults, self-excited resonant modes of the arc plasma column have been observed. They lead to an increased arc column stability...
In this paper the transistor open-circuit fault diagnosis strategy based on the converter voltage estimation error in the voltage oriented controlled three-phase two-level AC/DC lineside converter was presented. In accordance with the developed method, for the converter voltage estimation, the signals of the duty cycles of the voltage modulator as well as simple calculations, that use the line-to-line...
The paper describes a fully-dispatchable microgrid architecture that features i) the adoption of a master/slave power-based control in the central dispatcher to drive distributed power generators and ii) the connection of a suitable power converter equipped with energy storage, called Utility Interface, at the point of common coupling with the mains. Property i) ensures scalability and capability...
This paper presents a modified droop-based control for dc voltage restoration in a Multi-Terminal dc (MTdc) system of parallel-operated buck converters. The proposed control structure is introduced to a proportional-derivative (PD) droop controller, which realises the active power — dc voltage droop control method. The additional control structure consists of an adaptive integrator, which decreases...
The Modular Multilevel Converter (MMC), being a complex system, requires a number of controllers to function properly. These range from low level switching pattern generation to high level control loops. Among these controllers are modulation techniques that calculate the insertion indices, control inputs that decide the number of sub-modules inserted in a given arm. One such technique is compensated...
We propose a Least Squares Estimation procedure for estimating the admittance matrix of multi-bus DC MicroGrids (MGs). In the proposed solution, the generators simultaneously inject training signals in the form of small deterministic perturbations of the primary droop control parameters and measure the related steady state deviations of the bus voltage. When the training signals meet sufficient excitation...
This study proposes an enhanced current control strategy to eliminate DC and harmonic current at the output current of three-phase grid-connected inverters caused by DC offset and scaling error in grid voltage measurement. The proposed current controller designed in the stationary (α-β) reference frame is developed with a proportional integral (PI) plus three resonant controllers where the resonant...
This paper describes a concept for the coordination of active applications in LV networks to avoid unacceptable voltages and to ensure a stable control operation. The concept has been kept simple, without using an extensive algorithm. This ensures an uncomplicated implementation and operation. The focus of the paper lies on the explanation of the algorithm and the practical implementation. Furthermore,...
5 V and 12 V embedded low drop output (LDO) units are designed as parts of Multi-Functional Power Converter Control Integrated Circuits (MFPCC IC) and fabricated using 250 nm 40 V BCD (Bipolar, CMOS, DMOS) technology. Measured LDO parameters are in agreement with designed parameters in the temperature operation range −40…+85°C. It has been shown that developed LDO units operate properly in a wide...
A real-time control scheme is proposed to correct undesired voltages in distribution networks by adjusting the reactive powers produced by Dispersed Generation Units (DGUs). This is performed at two levels: locally, in DGU controllers, and centrally by a supervisory controller acting on some of the DGUs only. The centralized, discrete controller solves a multi-time-step constrained optimization inspired...
Increasing penetration of converter-based generations in power system has led to new system challenges. Short circuit power response from converter-based generations is different from that of traditional synchronous generators. Power electronic converters can be designed for over-current only up to 1.1–1.25 times of its nominal value. Low availability of short circuit power can cause many challenges...
The great number of power modules (PMs) imposes great computational challenge on the voltage balancing of modular multilevel converter (MMC) as the sorting of the PM capacitor voltages is usually adopted. This paper presents a distributed control method for PM capacitor voltage balancing in MMC. With this method, all PMs in one arm are grouped and the sorting algorithm of the voltage balancing in...
In order to simplify the configuration of photovoltaic (PV) grid-connection system, this paper proposes to adopt a buck-boost dc-dc converter, and then develops a single-phase inverter via the connection with an H-bridge unfolding circuit with line-commutated. Depending on the conditions of dc input-voltage and ac output-voltage, the proposed circuit can work functionally as either a step-down or...
This paper describes a design for fast and robust nonlinear deadbeat control for boost DC-DC converters. Nonlinear current reference deadbeat control is derived based on nonlinear state equation of the converter. Load disturbance compensation is implemented thus forming a new robust nonlinear controller. Both experiments and simulations of boost converter with input 12 V, output 20 V, load 4 Ω and...
Conventional 12-pulse diode rectifiers have advantages such as: simplicity, high reliability, and low DC bus voltage ripple; however, they also result in some disadvantages including harmonic current and the lack of re-generation capability. Therefore, this study proposes an auxiliary converter (AXC) for 12-pulse diode rectifiers to mitigate the harmonic current and provide re-generation capability...
The paper presents aspects related to the connection of renewable sources of energy to the grid and focuses on the Photo Voltaic Power Plant (PVPP). The correlation of this process with Power Quality (PQ) issues and conditions for certification of each plant in accordance with regulations are included in our work as well. Results of measurements of PQ in the Points of Common Coupling (PCC) in the...
This paper proposes a novel control scheme for frequency support among asynchronous AC areas through HVDC grids. It is based on local controllers, each acting on a voltage source converter, using locally available measurements only, and supporting frequency of the adjacent AC area after a significant disturbance. The controller is combined with the existing DC voltage droop technique and is inspired...
The increasing penetration of distributed generation has lead international authorities to integrate the rules for the connection of active end-users to distribution networks. Thus, power regulating functions aiming at supporting the voltage and frequency stability of the main grid have been recently introduced in European grid codes. In this paper, the consequences of adopting such regulating functions...
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