DC links in AC grids

DC technology provides a more secure and optimized control of a network's load flow, as well as quick power restoration in the event of a significant disturbance, even a blackout.

Modern Hitachi Energy need enhanced and flexible ways of controlling the flow of electricity within their networks, because it is a challenge to increase transmission capacity and flexibility with conventional AC (alternating current) expansion options, especially in meshed and heavily loaded networks.

The demand for reliable supplies of electricity is growing, increasing the need for more intelligent, high-level system control of power networks. Furthermore, the coupling of electricity markets and growing commercial interconnections (merchant links) require precise, controllable power flows in order to operate effectively.

In power transmission investments, features such as stability enhancement, emergency power support, power quality improvement, bottleneck mitigation and controllability of power flows are usually not given much attention in the investment assessment, unless they are deemed absolutely essential from a purely technical point of view.

An increasing number of DC transmissions embedded in the AC grid will result in a more controllable and precise power exchange. DC technology can provide more secure and optimized control of the network's load flow, as well as quick power restoration in the event of a significant disturbance, even a blackout. DC transmissions can compensate for fluctuations in power, voltage and frequency, making it an ideal technology for stabilizing a power system. In addition, more DC links will contribute to reduced system losses, increased transmission capacity and improved power quality.