A concept for a DC grid in industrial production

Size: px

Start display at page:

Download "A concept for a DC grid in industrial production"

Ashley Fox
5 years ago
Views:

1 DC-INDUSTRIE pril 2018 concept for a DC grid in industrial production erbundvorhaben: DC-Industrie Intelligentes offenes DC-Netz in der Industrie für hocheffiziente Systemlösungen mit elektrischen ntrieben

2 Table of contents 1) Targets and boundaries of an industrial DC grid 2) Concept for load sectors 3) Concept for grounding and EMC 4) Concept for protection 5) oltage control 6) Conclusions Page 2 pril 2018

3 Customer expectations Requirement DC grid features Reduced downtime ery fast disconnection from C grid faults by semiconductor switch Long ride through capability by storage devices and renewable energy sources Improved energy efficiency regenerative braking via the DC link Reduced conversion losses for storage and renewable energy Page 3 pril 2018

4 Typical devices in an industrial DC grid ariable speed drives + - Passive loads Infeed from the C grid DC - Bus Storage devices (e.g. batteries, capacitors, flywheels) renewable energy sources (solar, wind) Page 4 pril 2018

5 Boundaries of an industrial DC grid Industrial environment (no private homes) Spatial extension up to one production hall (e.g. 400m) Indoor (no overhead lines) Page 5 pril 2018

6 Table of contents 1) Targets and boundaries of an industrial DC grid 2) Concept of load sectors 3) Concept for grounding and EMC 4) Concept for protection 5) oltage control 6) Conclusions Page 6 pril 2018

7 Overview of the DC grid Netz storage LZ1 LS1 LZ2 LZ3 LS2 LS3 LS4 LZ4 generation Load sectors form a common logical unit contain components with strong functional interconnections DC network LZ5 LS5 LS6 LZ6 network management system control planning simulation contain sufficient capacitance to keep transient events inside themselves are connected to the DC grid via a DC connection box M M M M M M M communication network Page 7 pril 2018

Connection of the load sectors Features of the DC connection box Protection of other load sectors and lines Disconnection of the load sector Connection point DC connection box Pre-charging of

8 Connection of the load sectors Features of the DC connection box Protection of other load sectors and lines Disconnection of the load sector Connection point DC connection box Pre-charging of the load sector Optionally: Measurement functions Challenges Switching of DC current Connection point B Fast current rise ll load sectors feed into a short circuit Selectivity Page 8 pril 2018

9 Table of contents 1) Targets and boundaries of an industrial DC grid 2) Concept of load sectors 3) Concept for grounding and EMC 4) Concept for protection 5) oltage control 6) Conclusions Page 9 pril 2018

10 Grounding concept: principles and solutions Principles: Simple solutions (diode rectifier infeed) shall be possible Fast transients of the DC grid against ground should be prohibited for EMC reasons ll grounding concepts shall require the same creepage and clearance distances inside the equipment Two dedicated solutions: a) Low impedance grounding of the star point of the C grid b) Capacitive grounding of the DC midpoint Page 10 pril 2018

11 Low impedance grounding of the C grid star point Grounded secondary side of the C transformer Line switch C fuse C side EMC filter Infeed (e.g. diode rectifier) DC connection box transformer housing filter housing infeed housing Infeed will usually be an uncontrolled rectifier DC voltage to ground is impressed, both DC lines require a protective device. Page 11 pril 2018

12 Capacitive grounding of the DC midpoint Insulated secondary side of the C transformer Line switch C fuse C side EMC filter Infeed (e.g. ctive infeed converter) Grounding and insulation monitoring DC connection box transformer housing filter housing infeed housing The DC grid is de facto operated without connection to ground ( quasi-it ), there is only a high ohmic resistive ( >75kΩ for the complete installation) and capacitive grounding Stable potential of the DC lines to ground due to EMC capacitors The C grid is insulated from ground (insulating transformer) Only one DC line requires a fast protection device Operation may continue in case of one DC fault to ground Page 12 pril 2018

13 Overview of EMC ports C grid: conducted emission limits according to the environment + - No long overhead lines to renewable energy sources DC - Bus DC-BUS: Unscreened DC cables / rails Conducted limits similar to limits on C side EMC filter in each individual equipment Shielded motor cables Page 13 pril 2018

14 EMC concept - requirements Two basic requirements: 1) ll pieces of equipment in the industrial production site must not disturb each other 2) Radiated emissions must not disturb radio services Standard requirements for motor cables and C grid ports are identical to equipment used in today s C grids Page 14 pril 2018

15 EMC concept - solutions Particular issues for a DC grid: 1) High frequency common mode transients (DC ground) may radiate grounding concept avoids those 2) High frequency DC current may radiate minimize area between DC rails keep high frequency currents inside a load sector (e.g. use shielded cabinet) shielding of DC rails is unwanted by customers First artificial test results are positive Final validation on test sites Page 15 pril 2018

16 Table of contents 1) Targets and boundaries of an industrial DC grid 2) Concept of load sectors 3) Concept for grounding and EMC 4) Concept for protection 5) oltage control 6) Conclusions Page 16 pril 2018

17 Scenario 1: Fault inside a load sector Netz storage generation LZ1 LS1 LZ2 LZ3 LS2 LS3 LS4 LZ4 ll equipment in LS 6 is down Equipment inside LS 6 must protect itself DC connection box of LS 6 must open quickly LZ5 LS5 DC network LS6 LZ6 network management system control planning simulation LS 1 to 5 continue operation without interruption fter clearing the fault, the DC connection box of LS 6 closes and precharges LS6. Equipment in LS 6 starts operation again. M M M M M M M communication network Page 17 pril 2018

18 Scenario 2: Fault on the DC bus Netz storage generation LZ1 LS1 LZ2 LZ3 LS2 LS3 LS4 LZ4 ll load sectors feed into the fault ll DC connection boxes open ll equipment is down DC network No equipment is damaged LZ5 LS5 LS6 LZ6 network management system control planning simulation fter clearing the fault, the DC grid is powered up again. M M M M M M M communication network Page 18 pril 2018

19 Today s ideas for fast protection switches a) Fully electronic b) Hybrid: + T2 B + + S L B + T1 T2 - B - T1 D - B - ery fast reaction time (few µs) High on-state losses Low on-state losses Slower reaction time (few hundred µs) Choke required (careful design of resonances) Page 19 pril 2018

20 Table of contents 1) Targets and boundaries of an industrial DC grid 2) Concept of load sectors 3) Concept for grounding and EMC 4) Concept for protection 5) oltage control 6) Conclusions Page 20 pril 2018

21 oltage ranges Two possible rated voltages for the DC grid 540: Suitable for 400 passive infeed 650: Suitable for 400 active infeed and 480 passive infeed Rated operating range: Operation of equipment without restrictions Range of stationary over / under voltage: Equipment may be permanently operated in this range Functionality of equipment may be reduced (e.g. reduced power capability) ctive equipment tries to compensate the voltage deviation Range of transient over / under voltage Equipment may lose its function, but has to start operation again without any additional measures when the voltage comes back into the specified range oltage may stay in this range for a limited time only Protection limits: 400 / 800 Equipment switches off permanently Manufacturers may define different power ratings for equipment when operated at different rated voltage Eigenschutz Unterspannung Transiente Unterspannung Stationäre Unterspannung Nennbetrieb Stationäre Überspannung Transiente Überspannung Eigenschutz Überspannung DC-Spannung in olt Page 21 pril C & rdeter Sternpunkt 400 C

22 oltage regulation algorithms a) Uncontrolled operation (basic solution): No active control of the DC voltage (diode rectifier) b) Droop control (decentralized voltage control): ll active infeeds control their power according to the DC voltage Non-linear control characteristic No communication required c) Extended decentralized voltage control: Control characteristic is adapted during operation by a central control unit Slow communication required d) Central voltage control: Central control unit calculates setpoint values for the power of the infeeds Fast communication required The support of one or more algorithms is a feature of the equipment and not defined by the concept Page 22 pril 2018

23 Table of contents 1) Targets and boundaries of an industrial DC grid 2) Concept of load sectors 3) Concept for grounding and EMC 4) Concept for protection 5) oltage control 6) Conclusions Page 23 pril 2018

24 Conclusions The DC grid consists of several independent load sectors Energy exchange between different loads and sources is very easy Grounding concepts are fixed and allow to use existing equipment with regard to creepage and clearance distances Main challenge is the development of fast and low loss protection devices oltage ranges are fixed The DC grid may be operated with or without a higher-ranking management system for energy control Page 24 pril 2018

25 ssoz. Partner: BB STOTZ-KONTKT, E-T- Elektrotechnische pparate, HRTING, HOMG Group, Jean Müller GmbH Elektrotechnische Fabrik, U.I. Lapp, LEONI Special Cables, Phoenix Contact, SEW-Eurodrive, Yaskawa, ZEI. Page 25 pril 2018

Intelligent Grid Management of DC Grids in Production

DC-INDUSTRIE November 2018 Intelligent Grid Management of DC Grids in Production Verbundvorhaben: DC-Industrie Intelligentes offenes DC-Netz in der Industrie für hocheffiziente Systemlösungen mit elektrischen