In October 2017 Siemens launched the new Medium Voltage Direct Current transmission solution MVDC PLUS at the European Utility Week in Amsterdam, Netherlands. This solution can be used for different applications, e.g. to connect weak and unstable grids, to increase power infeed or for power transmission over longer distances up to 200 km.

As an example Mirko Düsel (CEO of Energy Management Transmission Solutions) mentioned Indonesia with its thousands of islands. For those islands, as well as for all other energy self-sufficient communities Diesel generators are often the only solution to offer power supply. Here MVDC PLUS can be an option to bridge the distance to a public grid connection and enable efficient sharing of power resources.

I wanted to know more about what has to be considered by power transmission over longer distances.

Considerations regarding efficient power supply

MVDC PLUS offers three standardized solutions for different type rates with positive impacts on costs and execution time for power transmission solutions from 30 MW up to 150 MW at different medium voltage levels of +/- 24 kV, +/- 30 kV or +/- 50 kV. From the white paper I have learnt that the efficiency (indicated by losses) in power supply depends on:

For the last point the specific use case has to be considered, to offer a constant power capacity or to transmit variable generated power from renewables.

Are there other alternatives available?

There are always additional opportunities. These are the options which can be used:

Let us have a deeper look at AC lines. The reactive power, skin and proximity effect result in transmission losses. AC links offer economic transmission for a similar DC power capacity only on high voltage level, but due to the known transmission losses there is no economic solution for AC transmission on MV level. Additional investments in Flexible AC transmission solutions (FACTS) may provide increased power transfer capabilities and voltage support. But this ends up with higher cost for the additional equipment of course.

That means alernatives are only available at high voltage level.

The Right Design Makes a Difference

Basically for each project the price/performance ratio has to be checked referring the alternatives. Nevertheless MVDC PLUS offers an attractive price due to:

Additional features like load flow control, an increased power transfer compared to AC systems (on similar voltage level) of around 20% can be considered. In case of down-time of the DC link both stations can operate as STATCOM.

Customers from all around the world are wrestling with cost-efficiency, reliability and availability in power supply. MVDC PLUS offers an economical solution to bridge the distance for the integration of remote areas or consumers, like onshore windfarms, utility scale photovoltaic, mining sites or as backup solution for existing local supply.

Related Links:

MVDC PLUS – proven technology for the future electrical grid

Future Energy: The new MVDC PLUS solution (medium-voltage direct current)

Autonomous distribution grids in power ranges up to 150 megawatts

Future Energy: The new MVDC PLUS solution (medium-voltage direct current)