ENERGY STORAGE DEVICES IN DC TRACTION POWER GRIDS

Transcription

1 ENERGY STORAGE DEVICES IN DC TRACTION POWER GRIDS

2 Energy Storage Devices: Why? Voltage Stability Prevent DC Traction Power Grids voltage variations during train acceleration and/or deceleration. Energy & Cost Savings Re-cycle energy generated during train deceleration. Peak shaving

3 Wasted Braking Energy DC Traction Power Grid Power Substation Voltage Rise due to Excess Energy DC Voltage Nominal Line Voltage Train braking Time

4 Wasted Braking Energy Concerns EFFECTS DC traction grid voltage increase Wasted Energy: Braking energy for 1 metro-type car: 10 MJ (mega joules) of energy = 2.8 kwh (kilo Watt hour) CONCERNS DC traction grid over-voltage shutdowns Use of line power dissipation devices = Loss of $$$$ Equivalent to powering 28 x 100W light bulbs for 1 hour.

5 Energy Demand during Acceleration DC Traction Power Grid Power Substation Voltage Decrease due to Energy Demand DC Voltage Train accelerating Time Nominal Line Voltage

6 Energy Demand During Acceleration Concerns: CAUSES EFFECTS DC traction grid line voltage collapse due to: Line impedance Higher current demand from newer trains Reduced headways Lower acceleration speed, hiccups, shutdowns Over current protection trips breaker open (power loss) Schedule delays

7 Energy Storage Devices Solution: SYSTEM GAINS: Stores energy in excess Energy re-use Minimum infrastructure impact: Add-on solution to existing network Mobile solution BENEFITS: DC traction grid line voltage stabilization Train performance improvement Limited infrastructure cost impact

8 BASS Solution Evolution Installed at SacRT (Sacramento, CA) in January VRLA batteries as storage device. Meeting all expectations: >160 cycles per weekday Line voltage support Improvements: Batteries limitations on re-charge current impact on energy capture performance High number of operating cycles lifecycle cost Addressed with ultracapacitor option

9 Ultracapacitor Technology Handles high charging and discharging currents = Ideal for storage and power assist modes 25% of VRLA batteries losses= more efficient 1 million cycles can be achieved=min. 10 years life and lower maintenance

10 Ultracapacitor Operation (1 of 3) Same behaviour as a capacitor used in electronic circuits. Technology currently used in: Consumer electronic products Telecom industry Traction power More energy storage capacity now available. Energy in an Ultracapacitor: 165 Farads, 48Vdc ultracapacitor: E = ½*C*V i ² - ½*C*V F ² E: energy C: Capacitor V i : Initial capacitor voltage V F : Final capacitor voltage, typically = V i /2 E = ½*C*3/4*Vi² = Joules

11 Ultracapacitor Operation (2 of 3) Number of modules required: Need modules in series to meet the operating voltage requirement. Need modules in parallel to meet the energy requirement. Example Line voltage: 950Vdc 10 MJoules of energy 165 Farad, 48Vdc module Number of modules in series: N = 950Vdc / 48Vdc N = 19.79, rounded up to 20. Number of strings: String energy = ½*C*3/4*(V i /20)² * 20 = 2.79 MJoules Number of strings = 10 MJ / 2.79 MJ = 3.58, rounded up to 4.

12 Ultracapacitor Operation (3 of 3) Energy Storage Mode (Train braking) capacitor recharge Charge voltage 950Vdc Voltage Regulator current from train Line voltage varies between 550 to 950Vdc Voltage Regulator Benefits Guarantees maximal energy highest voltage (E= ½*C*3/4*Vi² ) Power Assist Mode (Train accelerating) capacitor discharge Voltage Regulator current to train Maximal energy transfer with dynamic adjustment of VR output voltage Ucap discharges from 950 to 500Vdc Voltage dynamic control to ensure energy transfer

13 Braking Energy Recuperation DC Traction Power Grid Voltage Regulator Power Substation ENVISTORE Energy Absorption in Storage DC Voltage Nominal Line Voltage Train braking Time

14 Acceleration Energy Provision DC Traction Power Grid Voltage Regulator Power Substation ENVISTORE Energy Assist during Acceleration DC Voltage Nominal Line Voltage Train Accelerating Time

15 The Envistore Product: Scalable energy storage solution based on ultracapacitor technology. Based on 2 building blocks: The voltage regulator cabinet Maximum capacity of 1000Adc The ultracapacitor cabinet 2 strings of 20 ultracapacitors Maximum capacity of 5.6 MJoules (2 x 2.8 MJ)

16 Envistore: Scalability 2.8 MJoules to 45 MJoules

17 Envistore: Product Views Voltage Regulator Cabinet: 600mm x 1600mm x 2100mm 23.5 x 63 x 82.5 in. (W x D x H) Real-Time Controls Bi-directional DC-to-DC converter, 1000A max. Built-in contactors Remote control by GUI (over IP) and SCADA

18 Envistore: Product Views Ultracapacitor Cabinet: 600mm x 1600mm x 2100mm 23.5 x 63 x 82.5 in. (W x D x H) Front access drawer-type assembly for ease of maintenance 2.8 and 5.6 MJoules Capacity No moving part: The energy is stored on ultracapacitors modules

19 Envistore: Product Views Basic System View: 1 Voltage Regulator Cabinet 1 Ultracapacitor cabinet Add to the existing TPSS alignment

20 Envistore: Product Views System View with an expansion: 1 Voltage Regulator Cabinet 2 Ultracapacitor cabinets Up to 4 Ultracapacitor Cabinets per System 2 systems can run in parallel to increase capacity

21 ENVISTORE SMART POWER