"Possibilities of wide tolerance +300V residential distribution grids, and +-300V for industrial"

Transcription

1 "Possibilities of wide tolerance +300V residential distribution grids, and +-300V for industrial" Presenter and author: Prof. Alex Van den Bossche Ghent University, Electrical Energy Lab Technologiepark 913, Zwijnaarde, Gent, Belgium Round table 17 May , Rue De Mot, 1040 Brussels Round table Organised by EC DG, Unit C2 - New energy technologies, innovation and clean coal

2 Abstract "Possibilities of wide tolerance +300V residential distribution grids, and +-300V for industrial" Abstract: A lot of appliances could work in practice already now in a quite wide range around 300Vdc and retrofitting other appliances could be possible using pulsed DC. This voltage level permits a higher power at lower losses for a lower risk in occasional contact compared to 230 Vac. It is compatible with a dual supply of 300/600V that would be sufficient for a quite fast charge of cars using a light cable. It would allow a cheaper interface with PV and other renewable types of generation and emergency supplies. Proposed: Vdc ±10% at grid level, ±15% normal ±20% not destroyed or bad functioning Vdc = 600V total for higher power (industrial) use. Pulsed 300 Vdc: minimal 1-2 ms pause on a period of 10 ms (100 Hz) to avoid arcing problems with switches. 2/13

3 Some history of DC-levels, Table 1 (without railway) Approximate period Application Nominal DC Voltage Radio (lead acid) 4.2 V direct heated filament 80 V Anode very local use 55V (arc lamp) small grid 110 V (two arcs in series, or with gap feedback) 1900-now emergency reserve 120 V (still safe ) Cars, small Tractors 6 V 1950-now Cars 12 V (14V alternator) 1950-now Trucks, busses larger tractors 24 V (28 V alternator) Automotive project of car voltage 42 V (3x14V) 1900-now Telecom 48 V 2010-? 300 V+ converter 1960-now Digital IC 5 V down to 1.1 V 1960 Analog -- control 12 V, 15 V -- 24V 1960 Measuring 9 V 1980-now Rectified Vac 300 V 1980-now Rectified Vac 550 V 1950-now Forklifts 48 V 1990-now Newer forklifts 72 V, 96V, 120 V, 300 V 2000-now Power factor controller output V 2010-now Automotive, mild hybrid 48 V 2010-now Automotive, small car 300 V 2010-now Automotive, large car 375 V Tesla 360 ( V) Renault Zoe 2010-now Automotive: bus, truck V 3/13

4 Cable length and output at 10%voltage drop Table 2: distance and power output at 10% drop in a 2.5mm 2 cable, used at 15A 2.5mm2 Cu wire, 10% voltage drop, =20*10-9 m 16 m /m cable giving 0.24V/m drop at 15A DC Voltage [V] Length [m] Power out [W] (230 Vac) (95.8) (3105) Notes: At 300Vdc: significant more cable length than 230Vac 300 Vdc is already sufficient for garden or as extension cable for hand tools For 2% cable loss (= ECO -use) divide length by 5 or the power by about 2.3 4/13

5 Dual system in DC 300/600 V Table 3: Dual system in DC 300/600 V Example: (4+PE)x4mm 2 Cu cable, 25A/wire, For single phase and DC two wires are used in parallel. in three phase, the three lines, neutral not used The PE (protective earth does not carry current). Voltage Power [kw] Loss W/m (230 Vac) (11.5) 100 (400 Vac 3ph+N) (17.3) /600 Vdc 15.0 / /700 Vdc 17.5 / /800 Vdc 20.0 / Using 600 Vdc = +and- 300Vdc same tolerances Charging vehicles at 30 kw is possible with still a light cable (x4mm 2 ), A neutral is needed in the 600 V grid, but not in the cable to the vehicle But the installation should be rather at 10 mm 2 instead of 4 mm 2 to limit losses. The consumption of electric cars to be a bit ECO should be rather below 15 kwh/100 km. 5/13

6 Direct DC use Direct DC use: problem setting A lot of equipment could principally work directly on 300Vdc: Electronic power supplies, CFL lamps, LED lamps, If pulsed, chopped, also resistances, commutator motors can be used. Normal 230 V (magneto-thermal) protections for 400V 3ph, work only up to about 125Vdc max However PV DC circuit breakers are rather 250V/element In large systems 800V and 1500V Normal switches only separate 30 Vdc/contact, e.g. thermostat in boilers, the problem is arcing Grid protection can be adapted to detect arcing and switch electronically off before mechanic separation. 6/13

7 Pulsed DC principle Pulsed DC = solution for retrofit? +300 V Pulsed +0 V Load with switch A chopper close to the non-compatible appliance? If some 1-2 ms interruption is created, the arc has the time to cool down (de-ionize), This can be created by pulsating the current. (Limited slopes for radio interference) Avoiding problems with switches Adapt to the correct voltage using duty ratio May be needed inside/before e.g. cooking appliances Pulse length for 10 ms period: Avoid arcing and to correct rms voltage DC Voltage [V] Pulse [ms] Pause [ms] Pulsed V [Vrms] (= +10%) (= +20%) (= -10%) (= -20%) /13

8 Device compatibility Device AC DC Pulsed DC 300 V± 20% Laptop adapter without PFC , ±10% V no arcing by the presence of an internal capacitor 8ms on 2 ms off PCB typical internal supply 5 V 3 W 5, Vac no-load <0.15W Vdc Wide range possible Electric Boiler 230 ±10% Not directly 300 Vdc 5.9 ms on 4.1 ms off, can accept lower Cooking appliance 230 ±10% Not directly At 300V 300*0.59^0.5 = 230V rms 8/13

9 Device compatibility Device AC DC Pulsed DC 300 V± 20% Scooter charger 84 V 10A 72V LiFePO4 batt Led lamp, Filament look, other led 110V, 220V or Vac ± 10% May be Possibly Normally yes Possibly Garden instruments Cost effective DC protections exist, mainly developed for PV panel market, contain magnets Higher voltage DC circuit breaker Vac ± 10% Not: because of switch voltage and inductive 250Vdc single pole 500 Vdc double pole IEC IEC Vdc double pole IEC Pulsed 70%: results in the same average voltage (before the pulsed DC, only an example) (before the pulsed DC, only an example) 9/13

10 Compatibility with renawables Compatibility with PV is easier DC-DC converters need < 50% of the components and 30% of the development time. -> Factor 2 less cost? In fact the inverters have them already in the converters for the strings, Much less complicated synchronization, simpler processors, longer lifetime Design without electrolytic capacitors and simple processors, less circuit = 100% longer lifetime -> Factor 2more lifetime? Compatibility CHP combined heat power and stand-alone generators Generators at arbitrary frequency have much less losses and can be rectified -> Factor 2 in losses? Their weight of the generator can be 5 times less for the same power (PM outer rotor concentrated pole) -> Factor 5 less weight Compatibility with fuel cells Fuel cells are also DC, but typically lower voltage than 300V grid, converter may be: -> Factor 2 less cost? -> Factor 2more lifetime? 10/13

11 Safety of 230Vac compared to 300Vdc Safety aspects Body impedance typical ohm depending on contact surface 300Vdc, 1000 ohm is below 200 ms, good enough DC: less risk in long contact time at small contact surface But the voltage level should not be much higher than 300Vdc IEC graphs 11/13

12 Societal advantages/disadvantages of 300Vdc based systems Societal advantages of 300Vdc based systems On household base, 3500 kwh/year, about of 10kWh/day Cumulated over 30years Less losses for the same power: now 6% loss in the grid, could be reduced to 2% loss (also a part cables at the user side) At 3500 kwh/year, 30 years 3% at 0.3 /kwh 630? Savings in losses of PV grid inverters 1500 kwh/year, 2% 405 (1/3 of dwellings compensate 100%) Savings in costs of PV grid inverters: factor 2, three times in 30years (300 *3=900 )? Sum: 1935 (order of magnitude of TCO total cost of ownership) A lot of equipment is already compatible, other will be more cost effective. Laptop supplies, small internal supplies The DC side of PV converters, even loads directly on PV (electric boilers) UPS for data centers and communication is already DC V (48V was too low) Battery, supercap, fuel cell: better compatible Less consequences in large black outs: no synchronization problems Power electronics is already controlling most appliances, this transition is easy. Pulsed DC can solve transition problems A market advantage for people/companies that know it, can create jobs while saving energy. Societal disadvantages of dc based systems A transient period where equipment is not made compatible from the manufacturer side DC300 ready A learning period is needed 12/13

13 Conclusion A warm Thank You 13/13

14 Conclusion ADDENDUM: F2E for two electric at Ghent University. Ultralight closed vehicle under construction, (master student 1m90) Side windows are not yet mounted in. Vehicle about 140 kg. 96 V LiFePO4 battery, about 3kWh/100 km, so much less than 15 kwh/ Design for max speed 90 km/h; 50 km/h in 8 seconds Two outer rotor BLDC motors, front wheel drive, Charger can be DC-compatible 14/13