Stabilizing the Grid with the PCS100 Static Frequency Converter

The dependability of the power supply across the country is of paramount importance to industry, homes, and businesses. In general, electrical power is produced as alternating current (AC). This means that it alternates between positive and negative voltage. This oscillation is known as electrical frequency and is vital in the maintenance of a constant power supply. Alternating current oscillating at 50-times a second as it does in the UK is said to have a frequency of 50 hertz (Hz).

In general, electrical equipment in homes, factories, and offices are designed to operate at 50 Hz within a tight tolerance. Changes in supply and demand for electricity can have a major effect on the frequency of the grid. For instance, if there’s more demand for electricity than there is supply, the frequency will fall. Or if there is over-supply the frequency will rise. Any power with a frequency as little as one percent above or below the standard 50 Hz risks damaging equipment and infrastructure.

Changing Frequency, Applications

Not all areas of the world operate at the same frequency or indeed the same voltage. In general, 220-240 V supplies will operate at 50 Hz, while 110 V supplies will operate at 60 Hz. This means that some incompatibility is inevitable and special arrangements are required. For example, the majority of ships’ power generation units operate at a frequency of 60 Hz, whereas the local grid in most parts of the world is 50 Hz. To provide docking ships with electrical power a shore-side electricity supply arrangement is required. To ensure the same frequency diesel generators are usually used but these are inefficient and polluting. Another important situation is the installing or relocation of expensive factory plant or testing equipment from a 60 Hz to a 50 Hz region.  This would also require a special power supply of some sort (possibly a generator). Local cogeneration combined heat and power systems are another concern. These tend to operate at 40 Hz and because there could be fluctuations in supply stabilization control is required to prevent potentially damaging frequency changes. Overall, there is a requirement for equipment that can regulate both voltage and frequency and keep the electricity supply constant and safe.

In the Past

In the case of marine applications and factory equipment, there has always been the option of using diesel generators to provide electrical supply at the constant correct frequency (where 60 Hz is required in a 50 Hz region). Certainly, in the case of ships at dock generating power for their onboard system during cold ironing when the engines have been shut down problems have been highlighted. The process of switching off all the diesel engines of the vessels while at berth and supplying the power to the vessels by shore-side electricity is called cold ironing. For example, during a 10-hour stay in port, the diesel engines of a single cruise ship burn 20 metric tons of fuel and produce 60 metric tons of carbon dioxide. Equivalent to the total yearly emissions of 25 average-sized European cars. The cheap quality fuel used by diesel engines in marine vessels during a stay at berth is an environmental threat, and its extensive gaseous emissions are harmful to human health. It is believed that one billion tons of carbon dioxide (CO2) is from shipping, and the major source of emissions to air from ships are main engines, auxiliary engines, and boilers. More than 90% of global trade relies on maritime transport and to make this sustainable the IMO (International Marine Organization) believes that mitigating emissions and increasing energy efficiency is crucial.

Shoreside Power, a New Paradigm

By supplying the ship’s infrastructure with shore-side power port operators can improve energy efficiency, productivity, and sustainability of operations minimizing environmental impact. Ports are seeing increasing goods and passenger traffic as well as ever more stringent emissions regulations. These changes have required fresh thinking such as successful shore-to-ship power supply solutions. To accomplish the standardization of power between ship and shore it is not just a matter of hooking up some cables. The process requires specialized equipment. Fortunately, ABBs PCS100 Static Frequency Converter (SFC) allows the interconnection of electrical grid systems with varying frequencies. The PCS100 SFC can offer the ideal solution for shore to ship, plant relocation and even testing facility applications. Operating as part of a Harbour Area Smart Grid (HASG) the PCS100 SFC can supply power for ship’s services. It can facilitate both onshore power supply as well as charging of batteries for future hybrid and electric vessels.

ABB’s PCS100 SFC

ABB delivered the first shore-to-ship power solution to the Swedish port of Gothenburg in 2000. Their Power Conditioning portfolio is unique consisting of static frequency converters, UPSs, voltage and power conditioners that can solve power quality problems, stabilize networks and allow standardization between multiple frequency supplies. Onshore, the solution comprises the entire chain from the main incoming substation receiving power from the local grid, via systems matching voltage and frequency to the levels required by the vessels, to the power outlet at the berth. Onboard, the shore-to-ship power equipment is fully integrated with the ship’s electrical and automation system, enabling seamless power transfer from onboard generator supply to shore power. The system allows generators to be turned off while at the port to save fuel and eliminate pollution.

How Does It Work

The PCS100 SFC essentially allows connection of 60 Hz powered equipment to a 50 Hz supply network and 50 Hz powered equipment to a 60 Hz supply network. The static frequency converter can also, if required, convert the supply voltage to a different voltage to match the requirement of the load. The system functions by converting the input AC power through a sine-wave rectifier to a DC link and then through an AC sine-wave inverter to produce a clean, full sine-wave output at the new frequency and voltage. The PCS100 SFC system is constructed using state-of-the-art power modules that act as rectifiers to source sinusoidal current from the supply, and inverters to reproduce the AC waveforms on the output.

The connection and power transfer can be done smooth and without any interruption while the ship still runs on diesel generators. The PCS100 SFC connects in parallel with the diesel and shares the load. Now the diesel generators can be switched off while the ship gets supplied from shore power via the PCS100 SFC. The retransfer to diesel is similar.  

What Makes the PCS100 SFC Ideal?

The voltage and frequency of sensitive and expensive loads need to be protected and the PCS100 SFC has:

  • The ability to parallel with multiple generators
  • High system availability through advanced power module redundancy
  • The capacity to provide output immunity to input disturbances (for voltage drops and frequency shift)
  • Can act as a clean power supply to isolate an unstable grid from a critical load

References

  1. Tadeusz Borkowski, Dariusz Tarnapowicz, “SHORE TO SHIP” SYSTEM – AN ALTERNATIVE ELECTRIC POWER SUPPLY IN PORT, Journal of KONES Powertrain and Transport, Vol. 19, No. 2012
  2. Tarnapowicz, Dariusz & German-Galkin, Sergey. (2018). International Standardization in the Design of “Shore to Ship” - Power Supply Systems of Ships in Port. Management Systems in Production Engineering. 26. 10.2478/mspe-2018-0001
  3. PRODUCT PRESENTATION, PCS100 SFC, Static Frequency Converter, ABB, September 2018
  4. Jagdesh Kumar, Lauri Kumpulainen, Kimmo Kauhaniemi, Technical design aspects of harbour area grid for shore to ship power: State of the art and future solutions, International Journal of Electrical Power & Energy Systems, Volume 104, January 2019, Pages 840-852

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