Siemens has developed a transmission system for electricity grid operators that need to expand their infrastructure to manage increasing volumes of power supplied to the distribution system from distributed and renewable energy sources, and also to maintain the stability of their networks. The MVDC PLUS allows for the connection of distances of up to 200 kilometers. Siemens offers this medium-voltage direct current (DVC) transmission system as a compact unit in three variants with transmission capacities of approximately 50, 100, and 150 megawatts (MW), with DC transmission voltages from 20 to 50 kV.
In this way, MVDC Plus is suitable for connecting small communities in sparsely populated regions to the electrical grid, and for connecting and stabilizing low-power distribution networks regardless of their voltages and frequencies. This system allows for regulated power exchange between regional medium-voltage networks and microgrids. It also offers greater independence from the high-voltage grid. Both cables and overhead lines can be used for transmission. Existing routes can also be used when it is necessary to increase power capacity without upgrading to high voltage.
The transmission system also allows operators to establish a power connection between islands or offshore platforms and the mainland, avoiding the maintenance and costs associated with a backup diesel generator set. For example, the system can be used as a medium-voltage backup solution in the manufacturing industry, increasing the availability of machinery and equipment and reducing production losses. As a backup power system for data centers, the MVDC Plus guarantees, for example, a quality level ("tier") rating. The medium-voltage direct current transmission system is also attractive due to its cost-effectiveness and rapid deployment in local combinations with different financing models, which is becoming increasingly important in countries with a growing proportion of renewable and distributed energy sources.
MVDC technology is based on the HVDC Plus technology used in Siemens' HVDC transmission system, but reduced to its core functions. Like HVDC Plus, the medium-voltage transmission system operates with voltage source converters (VSCs) in a modular multi-level converter (MMC) design that converts alternating current (AC) to direct current (DC) and vice versa. Current in the transmission path can flow in both directions. Thanks to the use of insulated-gate bipolar transistors (IGBTs), the switching processes in the converter are independent of the grid voltage. Both converter stations can be operated as a static synchronous compensator (statcom). The high-speed intervention of the converter control and protection systems ensures the stability of the transmission system, reducing grid faults and abnormal operation in the three-phase power grid. This significantly improves security of supply for both energy providers and customers.
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- Category: Medium Voltage
Medium Voltage DC (MVDC) Direct Current Transmission System
With the MVDC Plus (Medium Voltage Direct Current Power Link Universal System), Siemens introduces to the market a new direct current transmission system that will allow efficient transmission routes in medium voltage alternating current electrical networks of 30 to 150 kilovolts (kV).
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