Improving energy performance power station of ship with integrated electric propulsion

The article presents the method of calculating the power plant fuel consumption on the basis of dieselgenerating installation (DGI) with variable speed for ships with integrated electric propulsion. Application DGI with variable speed allows saving fuel and therefore reducing harmful emissions into the atmosphere. In the paper calculated the fuel efficiency of unified power station on the basis of a variable speed DGI power of 1000 kW.


Introduction
On water transport are increasingly using integrated electric propulsion.This propulsion motors (PM) can be supplied together with other consumers from a unified power station (UPS).Application UPS simplifies maintenance and improves the reliability of the energy system of autonomous object by reducing the total number of system elements.The primary engine UPS widely used internal combustion engines (ICE).
As a rule, UPS are based on diesel DGI of constant rotation speed rotation.The electric power station gain in performance is possible due to variable speed rotation of DGI application.Fuel saving in this case is performed by setting for each load power value the optimal ICE shaft rotation frequency corresponding to the minimal fuelconsumption rate [1,2].
The UPS -DGI with variable speed rotation is a relatively new technical trend in small power.Research this systems carried out several foreign companies such as Fubag, Honda, Hyundai, Kypor, ABB, Wartsila etc.In Russia research carried out -JSC "R&D Center for power engineering" (Moscow), JSC "ZVEZDA" (St.Petersburg), JSC "Sigma" (Kovrov), VSUWT and NNSTU (N.Novgorod).
The use of UPS -DGI can reduce the absolute and relative Fuel consumption and ensure optimal thermal operation of DGI, improve service life and reduce the amount of harmful emissions into the atmosphere.

Fuel saving calculation of UPS with variable speed rotation
Determination the relative and absolute indexes of fuel consumption of UPS with a variable frequency of rotation DGI has been carried out as shown by UPS ship with electric propulsion [4].The calculation takes into account the energy loss of each element of the power structure of the UPS (fig. 1) when the load power changing over the entire range.On fig. 1 energy diagram, where Gabsolute fuel consumption rate, P mpower of DGI, P SGpower of SG, P FCpower of frequency converter, P Tpower of transformer, ΔP m , ΔP SG , ΔP FC , ΔP Tpower loss.
It should be noted that the change load power in UPS causes a change speed shaft of DGI [3].When calculating UPS efficiency it is taken into account those electrical equipment elements, comprised in UPS with a variable frequency of rotation DGI (synchronous generator (SG), PM, transformer (T), frequency converter (FC)) operate at variable frequency and voltage range.The ICE fuel consumption rate is determined according to the multivariate ICE characteristic [1].

UPS elements efficiency calculation
To calculate the efficiency of the UPS are used depending on the efficiency of the voltage frequency for each power element of UPS.

Efficiency of synchronous machine
The synchronous machine efficiency (SM) is determined through the following equations In ( 1) are used η SMsynchronous machine efficiency Р 1power consumption, p Σtotal losses in a machine, p i iron losses, p bbrush friction losses, p ccopper losses, p addadditional losses, p mechmechanical losses, p 1,0/50specific magnetic losses, fstator voltage frequency, B s1 , B s2induction corresponding to stator finger and lamination, Kcorrecting coefficient, βcoefficient, considering the steel losses dependency on the magnetization ratio; m s1stator finger mass; m s2stator lamination mass, r 1effective resistance of stator coil phase, m tratio considering the coil heat.
Fig 2 shows the efficiency dependencies on stator primary voltage frequency for a synchronous machine МСК1250-1500 (P N = 1000 kW, n = 1500 min -1 ).The dependencies correspond to load power P 1 = 0,25P N ; 0,5P N ; 0,75P N ; P N .According to [1] synchronous machines of МСК series the operate duration at stator current I=1,25I N is not to exceed 0,5 h.Fig. 2 and the following ones the dotted line limits the area of currents control Id1,25I N .

Efficiency of transformer
The transformer efficiency is determined by mainly the following equations In ( 2) the following notations are used η Ttransformer efficiency; p Σtotal losses, p w1 , p w2electrical losses ones in winding, p iTsteel losses, υ′specific steel losses [1,5], G C -core steel mass, mthe transformer phase number, m tcoil heat ratio; I 1 , I 2 , r 1 , r 2 respectively currents and resistance values of primary and secondary transformer windings.
Fig. 3 shows dependencies of the efficiency of voltage frequency of transformer ТСЗМ 1000-75.ОМ5.

Efficiency of frequency converter
Frequency converter (Fig. 4) efficiency as shown are calculated according to the following equations

UPS fuel economy estimate at load power «propulsion engine»
Installed power of the SM is the sum propulsion power and the onboard ship power (fig.1).
Fuel consumption of ICE is calculated in a range of screw-propeller (SP) speeds from 75 to 300 min -1 in increments of 25 min -1 .
To determine the ICE fuel consumption is used multivariable characteristic [6,7].ICE with a nominal speed of 400 min -1 and a power 1100 kW is selected to perform the calculations [1].
The shat moment on the SP is determined according to the equation where K -torque coefficient SP, ρmedium density, nfrequency of rotation SP, D рdiameter SP.
The supply voltage frequency SM is determined through the expression where f 0nominal frequency SM, n SPcurrent frequency SP, n SP_0nominal frequency of DGI.Determine the efficiency of the FC, T, SM for each specified speed of SP.
The power SM is determined through the following equation There have been obtained the graphs of specific fuel consumption rate (G e ) on the SP rotation (n) for the two UPS modes with the controlled and uncontrolled DGI (Fig. 6-9).The obtained figures show UPS with the controlled rotation frequency of DGI as compared to UPS without frequency control of DGI.In absolute fuel consumption UPS with regulation frequency of DGI economical system without regulation by 25-27%.

UPS calculation of fuel economy considering at the SM control
The above characteristics of specific and absolute fuel consumption rate have been obtained without taking into account SM excitation control.To enhance the economy of UPS, it is necessary to control the SM with respect to load power as related to the expression [1,8,9] (7) where i ex =I ex /I ex_nom , p 1 =P 1 /S NOM.
As shown in graphs (Fig. 10, 11), at the excitation control (Fig. 10, curves 1,3), the fuel consumption rate increases by the range of light and average loads.

Conclusion
Application UPS on the variable speed of ICE allows to efficiently economizing fuel consumption rate and reduces air emissions.Providing optimal mode of ICE in terms of fuel efficiency requires a new approach to the fuel supply control and can be implemented on modern management tools, including intelligent neural networktype control systems.
In the paper calculated the fuel efficiency of unified power station on the basis of a variable speed DGI power of 1000 kW.On the basis of the calculation results obtained by the comparative characteristics of the specific and absolute fuel consumption for the two modes of operation: a speed control of rotation DGI, depending on the load and a constant frequency of rotation of the DGI.In UPS of 1000 kW fuel savings can be up to 31% in absolute consumption.department «Electrical equipment, electric drive and automatics» of Nizhny Novgorod State Technical University n.a.R.E.Alekseev.

Figure 1 .
Figure 1.Energy diagram of power circuit UPS with variable speed DGI.

Figure 2 .
Figure 2. Dependency of МСК1250-1500 SM efficiency on frequency of power voltage at variable power P 1 .
are used η FCefficiency of frequency converter, η recefficiency of rectifier, η pwcefficiency of pulsewidth converter, η f1,2efficiency of filter, η invefficiency inverter, P dactive power at the rectifier outlets, ∆P recrectifier losses, P sem -semi-conducting equipment devices losses, ∆P subcooling system, system protection and control system losses, ∆.P FAVdiode losses resulting from direct current flow I FAV , k ϕcurrent form ratio, r Tdifferential resistance, U T0threshold voltage, ∆P L -filter inductance losses, ∆P IGBT -IGBT DOI: 10.1051/ , D -dynamic in IGBT transistor losses, P SWstatic in IGBT transistor losses, P DF -built-in IGBT diode losses, I CAVthe average impulse current conductivity collector value, U CE(Ic)saturation voltage at the given collector current , E tstotal energy losses at the collector losses current together with block drive circuit , I FМdiode average current; U FМdiode voltage at current I FM .

Figure 4 .
Figure 4. Flowchart of UPS frequency converter: recout-ofcontrol rectifier, PWMpulse width converter, F1, F2filters, Invstand-alone inverter.Fig.5 shows the dependencies of the efficiency of voltage frequency for the frequency converter having the nominal power 1000 kW.

Figure 5 .
Figure 5.The dependence of the efficiency of the frequency converter power 1000 kW from the utility power frequency.

Figure 6 .
Figure 6.ICE fuel consumption rate of UPS power 1000 kW: 1 -without regulation of speed DGI, 2with frequency regulation of speed DGI.

Figure 7 .
Figure 7. ICE fuel consumption rate UPS powered by 1000 kW.

Figure 8 .Figure 9 .
Figure 8. ICE absolute fuel consumption of UPS powered by 1000 kW: 1 with the regulation of frequency DGI; 2 without the frequency regulation of DGI.

Figure 11 .
Figure 11.The ICE fuel consumption rate economy in UPS power 1000 kW with SM excitation control.

Figure 12 .
Figure 12.Absolute fuel rate consumption of ICE in UPS: 1,2without regulation speed of ICE, 3,4with speed regulation of ICE, 1,3with regulation current excitation of SM, 2,4without with regulation current excitation of SM.

Figure 13 .
Figure 13. .Absolute fuel consumption of ICE in UPS power 1000 kW with regulation current excitation of SM.