What is power reversal in HVDC?

What is power reversal in HVDC?

In contrast to line-commutated HVDC converters, voltage-source converters maintain a constant polarity of DC voltage and power reversal is achieved instead by reversing the direction of current. This makes voltage-source converters much easier to connect into a Multi-terminal HVDC system or “DC Grid”.

How do you control power in HVDC?

The control of power in a DC link can be achieved through the control of current or voltage. From minimization of loss considerations, we need to maintain constant voltage in the link and adjust the current to meet the required power. Consider the steady state equivalent circuit of a two terminal DC link.

What are the basic objectives of HVDC control system?

An HVDC control system aims to ensure stable operation with reliable commutation in the presence of system disturbances and also to minimize system losses and converter reactive power consumption.

What are the main features of HVDC system control?

Control characteristics of HVDC system – Actual characteristics. The rectifier maintains constant current by changing α. However, α cannot be less than its minimum value (αmin). Once αmin is reached, no further voltage increase is possible, and the rectifier will operate at constant ignition angle (CIA).

What is HVDC transmission line?

A high-voltage, direct current (HVDC) electric power transmission system (also called a power superhighway or an electrical superhighway) uses direct current (DC) for the transmission of electrical power, in contrast with the more common alternating current (AC) systems.

What is the power reversal of DC link?

Constant Extinction Angle (CEA) control and Constant Current (CC) control techniques are implemented for the DC link control. The power reversal can be achieved by changing the polarity of the DC voltage. The harmonic effects of the DC links are reduced by using AC and DC filters for a more stable transmission system.

What are the requirements of reactive power control in HVDC system?

Abstract. The purpose of the reactive power control of HVDC system is to balance the reactive power exchanged between the AC and DC systems, and also to mitigate the harms of the harmonics produced by the converters to the system and the primary equipments.

What is CEA control?

What is HVDC VSC system?

VSC HVDC power transmission uses IGBT- based voltage source converters with advanced control strategies. It not only to achieves efficient power transmission, but also to provides dynamic reactive power support for the linked AC system(s). A passive or active AC network can be connected on the AC side of the VSC.

How power flow through HVDC transmission line can be reversed?

A power reversal is achieved by changing the operation modes in the converters from rectifier to inverter and vice versa and by reversing the direct voltage.

How does HVDC transmission system work?

How does it work? HVDC transmission utilizes a converter station at either end of the system. The valve at the beginning of the system converts alternating current to HVDC, the HVDC travels to the next location through a cable, and the valve at the end of the system converts the HVDC back to alternating current.

What are the advantages of HVDC over traditional transmission?

For long-distance transmission, HVDC systems may be less expensive and suffer lower electrical losses. For underwater power cables, HVDC avoids the heavy currents required to charge and discharge the cable capacitance each cycle.

What is the purpose of a HVDC link?

HVDC allows power transmission between unsynchronized AC transmission systems. Since the power flow through an HVDC link can be controlled independently of the phase angle between source and load, it can stabilize a network against disturbances due to rapid changes in power.

Why is HVDC used for underwater power cables?

For underwater power cables, HVDC avoids the heavy currents required to charge and discharge the cable capacitance each cycle. For shorter distances, the higher cost of DC conversion equipment compared to an AC system may still be justified, due to other benefits of direct current links.

What is a high-voltage direct current system?

A high-voltage, direct current ( HVDC ) system (also called a power superhighway or an electrical superhighway ) uses direct current for the bulk transmission of electrical power, in contrast with the more common alternating current (AC) systems. For long-distance transmission, HVDC systems may be less expensive and suffer lower electrical losses.