The cost of diesel generator sets is very high, which is not conducive to reducing the operating costs.
The use of shore power for ships berthed in the port can effectively reduce environmental pollution and noise, and also play the role of energy saving and consumption reduction, which is the main trend of power supply for ships in the future port.
For example, by using shore power, a large cruise ship that stops at a port for 10 hours can save 20tons of fuel and 60tons of carbon dioxide, equivalent to the total emissions of 25 cars in a year.
2-Brief introduction of Nancal shore power
The high voltage shore power is supplied by the harbor wharf apron substation, after frequency converter, the grid power changed to the electric power supply with specifications required by the ship power input system. Using cable trench or conveying trestle facilities, power supply cable lay to dock in the junction box, then through the cable drum connection device to ship.
The whole system mainly includes: Medium voltage distribution system, Medium voltage frequency converter, sine wave filter, grid-connected excitation inrush current suppression device, output isolation transformer, terminal cable connection box, cable reel connection device, ship power input system, ship control system and other auxiliary systems.
The system diagram is as follows:
Figure 2: Nancal Shore power system diagram
NANCAL AMP H series Medium voltage shore power supply converts mains power output into 6.6kV/60hz or 6kV/50hz power output after frequency conversion, sine wave filter and isolation transformer. It has the following technical features:
1) Harmonic suppression technology
a) The input side of the shore power supply adopts multi-level PMW input, and the harmonics generated on the network side meet and exceed the requirements of IEEE 519-1992 and GB/T 14519-93 for strictest voltage distortion and current distortion.
b)The output of shore power supply is equipped with sine wave filter, which converts the PWM wave into sine wave to meet the requirements of national standards on power quality.
Fully automatic no-disturbance switching technology: when power is switched between shore power and ship power, there is no need to power off the ship, and automatic switching can be realized without manual operation, so as to reduce the risk of human operation error.
Figure 3: no-disturbance switching Algorithms
Pic 4: Converting instantaneous waveform
(Yellow—Input voltage; Red & Blue—Output voltage; Green –Output current)
3)Reverse power suppression technology: reverse power suppression can be realized through software algorithm without the need to configure brake resistance or energy feedback device. The system structure is simple and the cost is low
4) Output voltage closed-loop control technology: it can ensure the stability of output voltage even when the ship's load is abrupt, and meet the ship's power supply requirements
Pic 5: Closed-loop Algorithms
5)Onshore-offshore potential treatment technology: due to the potential difference between the ground and ship, this potential difference will generate current. The Nancal shore power system is equipped with ground current protection. When the limit is exceeded, an alarm will be issued. When the problem is serious, the output will be blocked by failure. The limit can be set by HMI.
6) Reactive power compensation technology of shore power system: when onshore power supply does not need to supply power for ships, reactive power compensation for wharf power distribution system can be realized. This technology is a patented technology of Nancal. By adding switch and CT & control software upgrading, the functions of shore power supply and SVG can be realized in time.
The scheme diagram is shown as follows:
Pic 6: Reactive power compensation in shore power supply system
3- Nancal AMP H series application in Xiamen hairun Terminal
NC AMP H Medium voltage shore power supply products produced by Shanghai Nancal Electric co., LTD were applied to xiamen hairun container terminal in China (Fujian Province) free trade zone.
Pic 7: Location of Xiamen Hairun Terminal
In this project, the shore power project adopts the Medium-voltage on-board mode, and the power capacity is designed according to 3000kVA. The rated input voltage is 10kV, the input frequency is 50Hz, and the output is 6kV/50Hz or 6.6kV /60Hz Marine power supply. The shore power meets the needs of a single container ship of 10,000-150,000 tons in the dock during berthing operation.
In the process of connection and conversion between shore power and ship power, the ship does not need power off and realizes seamless switch.
The first scheme diagram of the system is as follows:
Pic 8: Hairun terminal 3MVA Shore power system scheme diagram
The shore power supply system support local monitoring and management, and is equipped with remote monitoring and management system. The system equipment is set at the gate of the wharf. The field simulation monitoring diagram is as follows:
Pic 9: Analog monitor in the project
The shore power supply device is installed in the steel fixed size container, which can be hoisted and placed on the trailer. The scene picture is as follows:
Pic 10: Inside view of the container