MARINELIVE GRID EMULATOR

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1 MARINELIVE GRID EMULATOR Photo 1. Electric Machinery of Grid Emulator Photo 2. Main Switchboards with protection systems

2 Photo 3. Central Control Unit Photo 4. Fuel cell NEXA K00-792

3 Photo 5. Power Quality Event generator IPC-480V/200A

4 1. General Architecture In the framework of the MARINELIVE project, a ship electric power system emulator has been developed at the School of Naval Architecture and Marine Engineering of NTUA. The design of this prototype ship grid emulator has been perfomed by the NTUA team along with Protasis SA which commissioned the complete final system. The system is actually an AC three-phase one, comprising Generation, Distribution, Consumption, Protection and Supervising Monitoring- Control sub-systems (see Photos 1-3). A simplified one-line diagram of the system is shown in Fig. 1, in which dashed lines indicate installations planned for the near future (approximately in 2 months). IM5 IM4 GRID AC/DC/AC SAG GEN AC/DC/AC BUS1 BUS2 AC/DC/AC IM1 SG1 AC/DC/AC IM2 SG2 RL LOAD AC/DC/AC IM3 SG3 Switch for fault simulation AC/DC/AC FUEL CELL Figure 1. One-line diagram of grid emulator. The power generation sub-system comprises three synchronous generators (two of 5.9 kva/400v/50hz/pf=0.8 ind. and one of 5 kva/400v/50hz/pf=0.8 ind., see Photo 1). The installation of some other power sources via a DC/AC inverter (e.g. a fuel cell) is foreseen to be integrated in the future, esp. considering that a fuel cell unit has also been purchased (NEXA K complete model with incorporated DC load and monitoring system purchased by Heliocentris EnergieSysteme GmbH Germany, see Photo 4). Note that as the generators are of low power, they produce Low Voltage (400 V), so no transformers are used in the system.

5 An induction motor fed by the local grid via an AC/DC/AC converter plays the role of the prime mover for each generator, while the fuel injection rule is emulated via the power electronic inverter rotating the prime mover - electric motor. On the other hand, the generator output voltage is regulated via installed Automatic Voltage Regulators (AVR s) of BASLER. It is noted that the system is essentially electrically isolated with respect to the local grid, with the exception of auxiliary circuits (e.g. the AVR s of the synchronous generators and protection relays). The system loads are a passive RL load and a three-phase induction motor (see Photo 1 and Figure 1). Similarly to the synchronous generators (but with opposite power flow), the mechanical load of the motor is another induction motor connected to an AC/DC/AC converter and acting as a regenerative brake. The ensemble of the motor and AC/DC/AC converter can be used to simulate various mechanical loads, e.g. a propeller. To create contingencies to the system, a power circuit breaker has been installed to emulate threephase faults, as well as a Power Quality event generator. The Power Quality event generator has been purchased from Power Standards Laboratory - PSL (USA), see Photo 5. It is a complete unit IPC-480V/200A, which is connected in series to the grid and can bre programmed/controlled via a PC-based software so that well pre-defined power quality events (e.g. voltage sags of prescribed duration and amplitude) are provoked to the network. The installation of an AC/DC/AC converter, which will be optionally used to feed the induction motor load of the system, is foreseen in the near future. In this way, it will also be possible to emulate motor loadings e.g. the electric propulsion by uploading the propeller dynamics (look-up tables of torque vs time) to the regenerative brake controller. The power generation sub-system of the Grid emulator can be synchronized with the mains emulating the ship-to-shore connections following the Gold Ironing investigation studies. The main features of the Grid Emulator are summarized in Table 1.

6 Table 1. Summary of Ship Grid Emulator equipment. Generator sets 2 sets of 3-phase 400V/50 Hz/5.9 kw/pf=0.8 ind. (Manufacturer Focquet/Belgium, type FB4SA) 1 set of 3-phase 400V/50 Hz/5.0 kw/pf=0.8 ind. (Manufacturer GENCO /UK, type: RF201A) Motor load: R-L Passive Load Power Quality Event Generator Protection Scheme Main components Fuel Cell Unit Associated Automatic Voltage regulators: AVRs (Manufacturer BASLER/USA-France: DECS-100) AC induction Motor + Brake: 3kW (Manufacturer Focquet/Belgium, type MF3A4) Power electronic converter for braking: Siemens G120/5.5 kw/400v/50 Ha/ 4 quadrant) Three-phase, 400 V/50 Hz/4.8 kw+2 kvar scalable in 3 steps (Customized design commissioned by RITA transformers) IPC-480 V/200A (manufacturer Power Standards Laboratory-PSL (USA) SEL-700G generator protection SEL-751 A feeder protection SEL-710 Motor protection SEL-487B Bus differential relays SEL-2407 GPS Clock Manufacturer: SEL/USA NEXA K complete model with incorporated DC load and monitoring system Manufacturer : Heliocentris Energie Systeme GmbH Germany

7 2. Electric Power Management And Control System EPMACS For control and monitoring of the system, there is an Electric Power Management And Control System (EPMACS), which is consolidated with the system protection relays. The protection scheme installed comprises sophisticated SEL-relays and other associated equipment. It includes generator, feeder and motor protection relays, as well as a bus differential protection scheme. Apart from their protection functions, the digital protection relays used offer possibilities for telemetering and remote control. Using the IEC protocol, all available measurements are collected to a Supervisory Control And Data Acquisition (SCADA) System. The data network, on which the SCADA application is based, includes the digital protection relays, the central Managed Ethernet Switch (ETHSW), a Real Time Automation Controller (RTAC) and the central system computer, which is also the SCADA Server (see Fig. 2). Figure 2. Data network architecture. As shown in Fig. 2, all the relays and other devices are connected radially to the ETHSW via an Ethernet network (100Mbps - UTP Cat6). The data network functions are: Telemetering and remote control data collection, IEC MMS protocol Exchange of data between the relays and between the relays and RTAC, IEC61850.Goose protocol Data for relay configuration event recording, TELNET & FTP protocol. The data network includes a GPS clock which distributes the time signal to all the devices of the data network by means of the IRIG-B00x protocol. By means of the Human-Machine Interface (HMI) of the SCADA system (realized with specialized commercial software), various capabilities are provided: Close/Trip circuit breakers

8 Close/Trip disconnectors Automated commands Increase/Decrease Step on Inverters (e.g. frequency control, active power sharing) The initial screen of the HMI is the one-line diagram of the network. It is a dynamic image, which offers important information on the system state and refers to more detailed views of the network. The information shown on the one-line diagram concerns the state of the circuit breakers and disconnectors, as well as electric measurements. This information comes from the digital protection and control devices. Available measurements of the HMI are: Voltages/Currents Active/Reactive Power (in or out a grid component) Cosφ Energy Event/Alarm list All measurements are stored every minute in the internal database of the HMI and can be extracted as Comma Separated Values (CSV) files or to an SQL database for further processing by other software. 3. Associated software exploited for Electric Ship studies PSCAD Pro/Educational (of Manitoba HVDC Center): exploited mainly for Power Quality event studies. FLUX2D/3D (of CEDRAT/France): exploited mainly for parametric electric machine design. MOTORCAD (of Motor Design Ltd/UK, CEDRAT/France): exploited for thermal analyses of electric machines. MATLAB (of Mathworks/USA): generic multi-purpose tool. 4. Exploitation plans of the grid emulator 4.1 Exploitation to investigate Power Quality problems Project Defkalion ( (co-funded by European and Hellenic Resources - ESPA-Thalis project framework; starting date Jan 1 st, 2012; ending date: Sep 30 th, 2015) Investigation of power quality events (sags and swells), furthering methods already

9 developed to identify and classify events that have occurred and mitigation measures development. Indicatively: a) Investigation of Power quality problems due to the operatin of electric motor driven propulsion systems (the transient propeller dynamic power demands have to be emulated via the brake system). b) Establishment of a Power Quality monitoring system which identifies and classifies any Power Qualty events that have occurred. The event generator will be fully exploited to this end. 4.2 Investigation of advatages of DC grids over AC grids Project DC-ship (proposal just approved; co-funded by European and Hellenic Resources - ESPA-Thalis project framework) Comparison between AC and DC ship grids in terms of installation and operation principles, resulting in Ship Efficicency comparison in terms of EEDI/EEOI (i.e. focusing on fuel consumption and related emissions as defined by IMO directives). A DC grid of equivalent power rating is to be installed so that the two systems can be compared not only via computer simulations but in actual operating conditions (transient and steady-state operating modes). 4.3 Cold Ironing investigation studies: The in-built synchronization capability of the grid emulator with the power mains will be exploited to further develop proper ship-to-shore interconnections. Cold ironing of ships is an interesting idea to be blended in with the smart-grid concept, esp. for power peakshaving (the ports can be considered the ideal big consumers which, having invested in energy storage units, can provide the most appropriate peak-power-shaving-on-demand without large investments in smart power systems with two-way communications in numerous small power consumers). 4.4 Massive actual Data provider of ship system operating parameters. These data will be used for testing broadband ship-to-ship and ship-to-shore communication networks via mesh systems. Other foreseen applications 4.5 Development of Ship Energy Efficient Management Plan (SEEMP) integrated in the SCADA/EPMAC-System The centralized monitoring and control system of the entire electric grid (with all the critical operating parameter measurements) will be the ideal platform to develop a SEEMP for

10 electric ship. Moreover, investigation and development of EEDI/EEOI formulae for ships with electric propulsion (currently, for a number of reasons, they are exempted from IMO s regulations).