Transient recovery voltage

About: Transient recovery voltage is a research topic. Over the lifetime, 2634 publications have been published within this topic receiving 27176 citations. The topic is also known as: TRV.

Solid-state circuit breakers and current limiters for medium-voltage systems having distributed power systems

Abstract: State-of-the-art mechanical circuit breakers in medium-voltage systems allow a safe handling of short-circuits if the short circuit power of the grid is limited. Using delayed turn-off times, the circuit breakers can be coordinated with lower level protection gear. Hence, a high availability of the grid can be guaranteed. However, during a short-circuit a significant voltage sag can be noticed locally in the medium-voltage grid. Sensitive loads such as computers will fail even if the voltage returns within a few seconds. A semiconductor circuit breaker, however, is able to switch fast enough to keep voltage disturbance within acceptable limits. The optimization and selection of power electronic switch topologies is critical. In this paper, different semiconductors are briefly compared considering the requirements of a solid-state switch integrated into a 20-kV medium-voltage grid. Based on these semiconductor characteristics, various switch topologies are developed, which are compared under technical and economical aspects. It is shown that solid-state circuit breakers offer significant advantages when compared to present solutions and can be used in today's medium-voltage power systems.

Method of converting a direct current voltage from a source of direct current voltage, more specifically from a photovoltaic source of direct current voltage, into a alternating current voltage

Abstract: An inverter is devised to avoid high-frequency voltages at input terminals and to allow good efficiency thanks to its simple and cost-optimized circuit layout. This is achieved by a method of converting a direct current voltage, more specifically from a photovoltaic source of direct current voltage, into an alternating current voltage at a frequency through a bridge circuit comprising switching elements (V 1 -V 4 ) and free-wheeling elements (D 1 -D 4 ), said switching elements (V 1 -V 4 ) being on the one side gated at the frequency and on the other side clocked at a high clock rate, a direct current voltage circuit, an alternating current voltage circuit and a plurality of free-wheeling phases being provided. It is provided that, during the free-wheeling phases, the alternating current voltage circuit is decoupled from the direct current voltage circuit by means of a switching element disposed in the direct current voltage circuit, a free-wheeling current flowing through one of the free-wheeling elements (D 1 ) in the bridge circuit when in the decoupled state.

Transient operation of grid-connected voltage source converter under unbalanced voltage conditions

Abstract: In this paper, the operation of shunt-connected voltage source converters under unbalanced voltage conditions is investigated. The attention focuses on voltage dips, thus on transient operation. The importance of using a fast and accurate method for detection of sequence components of the grid voltage affected by a fault is emphasized. Four different sequence-detection techniques are presented and compared on the basis of their transient response. Three different current controllers for VSCs are implemented and compared in both cases of constant and regulated DC-link voltage. In the latter case, the corresponding DC-link voltage controllers are described. The operation of the VSC equipped with the different current controllers is analyzed with constant-power and fluctuating-power loads. Results obtained with different type of loads demonstrate that the optimal choice of the controller depends on the expected application.

Memory sensing circuit and method for low voltage operation

Abstract: A sensing module operates with a sense amplifier sensing a conduction current of a memory cell via a coupled bit line under constant voltage condition in order to minimize bit-line to bit-line coupling. The rate of discharge of a dedicated capacitor as measured by a change in the voltage drop thereacross in a predetermined period is used to indicate the magnitude of the conduction current. The voltage cannot drop below a minimum level imposed by a circuit for maintaining the constant voltage condition on the bit line. A voltage shifter is used to boost the voltage during the discharge and to unboost the voltage after the discharge, so that the change in voltage drop properly reflects the rate of discharge without running into the minimum level.

A Surgeless Solid-State DC Circuit Breaker for Voltage-Source-Converter-Based HVDC Systems

Abstract: This paper proposes a dc circuit breaker for voltage source converter (VSC) based high-voltage dc transmission (HVDC) systems. Technical challenges for applying dc circuit breakers are to increase blocking voltage and to suppress surge voltage at the current clearing. The proposed dc circuit breaker is a solid-state breaker which consists of a number of semiconductor devices in series. It maintains equal voltage balancing among the devices to apply it to high-voltage applications. Moreover, the surge voltage across the circuit breaker is reduced by employing a freewheeling diode. Considering a system rated at 300 MW in power and 250 kV in dc voltage, the conduction loss of the proposed circuit breaker is estimated to be 0.045% of the rated power. The value is smaller than the power loss of the VSCs. A downscaled HVDC system rated at 10 kW in power and 360 V in dc voltage was built and tested. A series of experimental results demonstrates the dc fault clearing and rapid restoration of power transmission.