In an alternating current (AC) electric power system, synchronization is the process of matching the frequency and phase and voltage of a generator or other source to an electrical grid in order to transfer power. If two unconnected segments of a grid are to be connected to each other, they cannot safely exchange AC power until they are synchronized.
A direct current (DC) generator can be connected to a power network simply by adjusting its open-circuit terminal voltage to match the network's voltage, by either adjusting its speed or its field excitation. The exact engine speed is not critical. However, an AC generator must additionally match its timing (frequency and phase) to the network voltage, which requires both speed and excitation to be systematically controlled for synchronization. This extra complexity was one of the arguments against AC operation during the war of currents in the 1880s. In modern grids, synchronization of generators is carried out by automatic systems.
There are five conditions that must be met before the synchronization process takes place. The source (generator or sub-network) must have equal root-mean-square voltage, frequency, phase sequence, phase angle, and waveform to that of the system to which it is being synchronized.
Waveform and phase sequence are fixed by the construction of the generator and its connections to the system. During installation of a generator, careful checks are made to ensure the generator terminals and all control wiring is correct so that the order of phases (phase sequence) matches the system. Connecting a generator with the wrong phase sequence will result in large, possibly damaging, currents as the system voltages are opposite to those of the generator terminal voltages.
The voltage, frequency and phase angle must be controlled each time a generator is to be connected to a grid.
Generating units for connection to a power grid have an inherent droop speed control that allows them to share load proportional to their rating.
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The students will learn about the basic principles of wireless communication systems, including transmission and modulation schemes as well as the basic components and algorithms of a wireless receive
An electrical grid is an interconnected network for electricity delivery from producers to consumers. Electrical grids vary in size and can cover whole countries or continents. It consists of: power stations: often located near energy and away from heavily populated areas electrical substations to step voltage up or down electric power transmission to carry power long distances electric power distribution to individual customers, where voltage is stepped down again to the required service voltage(s).
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EPFL2022
Explains synchronization of synchronous machines with the power grid and analyzes power diagrams.
Explores the basics and characteristics of synchronous machines, focusing on induced voltage, power balance, and torque.
Demonstrates the synchronization process of a 250 kV synchronous machine simulator.
This paper proposes a Linear Parameter-Varying loop-shaping controller for a power-synchronized grid-following inverter (PSGFLI). This control strategy regulates the inverter output active and reactive power at the terminal instead of the point of connecti ...
2022
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The medium-voltage grid emulator is gaining popularity for testing grid-code compliance of large-capacity converters for renewable energy resources. The cascaded H-bridge converter based on active-front-ends is a promising candidate for high-power grid emu ...