Wärtsilä has been leading the way to ever more efficient shipping since 1834. Wärtsilä’s extensive portfolio of electric propulsion solutions allows us to select the ideal configuration to meet any vessel’s needs. From high power systems for cruise vessels to low noise systems for research vessels to high redundancy systems for offshore vessels, Wärtsilä has the right solution. And with advances in energy storage systems, we are now able to supply hybrid systems using Wärtsilä’s Energy management systems to increase the vessel’s efficiency.
Electric propulsion systems are particularly economic, environmentally-friendly, and reliable. They are simple to operate and control, and have low levels of noise and vibration.
At reduced propeller speeds, the number of generators online can be selected according to the power demand. This allows increased engine efficiency and thus, reduced fuel costs.
Higher reliability and availability is made possible by redundant configuration of the propulsion system.
Flexible use of the motor torque-speed characteristic allows high-over torque at propeller standstill if required: The propeller can be also driven at all speeds and torques within the design limits without any limitations.
Changes in propeller speed and propeller reversals during at manoeuvring and positioning can be carried out at optimum acceleration rates.
There is minimal interference of the mains due to harmonics generation and voltage drops.
Lower emission levels of NOx/NO, CO, CO2 and soot, as well as reduced fuel consumption, can be achieved by operating the diesel generators within the optimal operational range as the propulsion load varies.
All propulsion drives can be controlled automatically by a ship navigation and command system, or manually from any control console. All of the functions and operating states are monitored to prevent operating mistakes and overloads.
Reduced maintenance costs and spare parts demand, compared with those of diesel mechanical driven ships, is made possible by having fewer diesel motors and cylinders, as well as by operating the diesel motors at constant speed.
LCI Converter System
Frequency converters with line controlled inverters (LCI converters also known as synchro-converters) are designed with a direct current (DC) intermediate circuit, and consist of thyristor rectifiers on the mains side, a thyristor inverter on the motor side, a DC reactor in the intermediate circuit, an excitation converter, and a control system. LCI converters are provided to supply synchronous motors.
Synchro-converter based systems were also used in Wärtsilä's former shaft alternator system design, with more than 385 units delivered since 1967.
LCI converter systems have the following advantages:
PWM Converter System
Frequency converters with pulse width modulation (PWM converters) are self-controlled converters designed with a DC voltage intermediate circuit, and comprise (in the DFE solution) a diode rectifier on the mains side, an insulated gate bipolar transistor (IGBT) or integrated gate commutated thyristor inverter (IGCT) on the motor side, DC capacitors in the intermediate circuit, and a control system. For improved mains quality and for reverse power characteristics, the diode rectifier on the mains side is replaced by an IGBT rectifier (active front end AFE design). PWM converters are provided to power either asynchronous or synchronous motors. For synchronous motors, an excitation converter is also provided.
PWM converter systems have the following advantages:
Active Front End (AFE) converters with PWM, instead of a diode rectifier input, offer the following additional benefits and are, therefore, typically used nowadays:
Low Loss Concept
For certain power system configurations, the patented Wärtsilä “Low Loss Concept” (LLC) can be used. This is designed to remove the need for either a bulky transformer for a DFE drive, or an AFE drive.
Wärtsilä has devised an ingenious way to overcome this problem by splitting the distribution bus into two sections, and placing the transformer between the two buses = Low Loss Concept (LLC).
This gives a total reduction in the number of transformers (lower footprint) for installations with more than two drives connected, compared to the DFE solution. Where more than two drives are installed, the advantage of having fewer transformers becomes even more apparent.
The advantages of this design include:
Hybrid Energy Storate Systems (ESS)
Hybrid power systems combine different power sources with energy storage devices. The introduction of the hybrid power system, and its integration with conventional diesel-electric propulsion can offer a significant improvement in efficiency by running the engines at optimal load, and by absorbing many of the load fluctuations through batteries.
The introduction of Hybrid Power Systems with energy storage is, therefore, a new and attractive means for reducing both fuel consumption and exhaust emissions.
The Wärtsilä system’s design handles the energy storage capabilities in the form of a battery pack, an hybrid control system, a power transfer system, and an energy storage system. The key element in hybrid type power systems is how to store the energy safely and efficiently. The most available technology at present is batteries. The design and the capacity of an energy storage system will depend on how the system is to be used. Knowledge concerning the actual operational profile of the vessel is therefore important.
The main objective of the Energy Management System is to control the vessel’s energy flow. Based on the selected operational mode, and whether the batteries are to be operated for peak-shaving or as the main source of power, the EMS has to control the number of engines online, whether the batteries are to be charged or discharged, and the rate of charging and discharging.
Most modern cruise liners and ferries are designed with converter-fed propulsion systems. These offer numerous advantages in terms of low noise and vibration-free operation, maximized cabin related loading capacity, more economic operation - especially the improved efficiency in partial propulsion power mode, a high degree of reliability, availability and redundancy, lower emission levels, and reduced wear and tear.
Depending on the required grade of redundancy, and on the operational profile of the vessel, synchro-converter (LCI) or PWM-converter drives with synchronous or induction motors provide well proven and reliable solutions for propulsion systems.
The propulsion systems for offshore, pipe and cable laying, as well heavy lift jack-up vessels, need to be designed with excellent dynamic characteristics in order to carry out rapid changes in speed and reversals during manoeuvring and positioning.
The speed control of the propulsion and thruster motors is realized via frequency converters with pulse-with modulation (PWM) in HV- or LV-technology. The converters are designed (in the standard solution) with a diode rectifier on the mains side, an insulated gate bipolar transistor (IGBT) or an integrated gate commutated thyristor inverter (IGCT) on the motor side, DC- capacitors in the intermediate circuit, and a control system.
Each PWM-Converter drive is equipped with a Wärtsilä Propulsion drive control panel, which controls and monitors the drive and provides the torque set value via bus connection to the PWM-Converter control. Additionally, actual data including, for example, measured values, alarms, etc., are received from the converter control for continuous data processing, which is then displayed on the 15” touch screen panel mounted in the front door. The Propulsion control panel is also interfaced with the superior ship’s automation, control and monitoring system via a serial data line.
Propulsion for Research and Survey ships, as well as Fishery Supervision Vessels
Wärtsilä has delivered the low noise diesel-electric propulsion systems for many research and survey vessels. These propulsion systems are based on the principle of speed controlled DC or AC motors driving the propeller directly or via gears. The most reliable and low noise design is the direct drive.
Propulsion for Multi-purpose Vessels and Icebreakers
Multi-purpose vessels and icebreakers require propulsion systems with excellent dynamics to permit the flexible use of the torque speed characteristic, up to high-over torques and propeller standstill.
With more than 200 installations worldwide, our propulsion systems deliver power for cruise liners and ferries, cable laying vessels, heavy-lift jack-up vessels, research and offshore vessels, and mega yachts – with a combined total of more than 3.000 MW.
The control system of converter-fed propulsion drives is designed for:
All operational requirements are achieved automatically via the electronic control device. Electronic control is achieved using microprocessor controlled devices, and it also includes the I/O channels necessary for monitoring and alarm functions integrated into the propulsion control system.
Propulsion Control & Energy Management Systems
In the Wärtsilä Propulsion Control System, the drives are configured as subordinated consumers for the power system. The propulsion output is automatically reduced if the momentary consumption exceeds the power available from the supplying diesel generator sets. In combination with the power management system, diesel generator sets are started, synchronized, and stopped automatically. In order to retain stable operation of the power plant at all times, the power consumption of the propulsion drives is reduced if:
In the case of manoeuvring or crash stop operations, the reverse power generated by the propulsion motors is fed back to the main alternators and to the mains. In order to retain stable operation of the power plant also during this operation, the reverse power generation of the propulsion drives is reduced if the speed of the diesel engines increases above admissible values.
Where Hybrid systems are used, the Wärtsilä Energy Management System is used to optimize the power flow in the system, including control of charging and discharging the energy storage and setting the speed of the engines, in addition to the standard functions of the Propulsion Control System and the Power Management System.
Monitoring Screen Displays
For local monitoring and auxiliary control of the propulsion system, colour touch screen displays are provided at each propulsion control panel and on the ECR control console with the following mimics and functions:
Remote Control System
For remote control of the propulsion drives, a combined speed control and telegraph system can be provided as the command and communication system, designed for sending speed commands from the wheelhouse, bridge wings, engine control room (ECR) or local control consoles to the converter controls. Additionally, operation panels with illuminated push buttons, warning lamps, emergency stop, safety device indications, an overriding device, control transfer facilities, control switches, and speed and power meters can be included.