Report

Chapter 10 Application of Power Electronics Power Application of Power Electronics 10.1 10.2 10.3 10.4 10.5 10.6 10.7 DC motor drivers ( thyristor-DC motor system ) Frequency converters and AC drivers Uninterruptible Power Supply ( UPS ) Switching Power Supply Power factor correction (PFC) Application in utility power system Other applications 2 10.1 DC motor drivers ( Thyristor-DC motor system ) 10.1.1 Rectifier mode of operation 10.1.2 Inverter mode of operation 10.1.3 Reversible DC motor drive system Power (four-quadrant operation) a iTv1 b iTv2 c iTv3 LB VT 1 LB VT2 L LB VT 3 id ud M EM + o 3 10.1.1 Rectifier mode of operation Waveforms and equations ua ud ub Ud EM R Id U Power (10-1) where 3 XB R RB RM 2 (for 3-phase half-wave) uc ud Ud E idR wt O a id ic ia ib ic wt O Waveforms of 3-phase half-wave rectifier with DC motor load 4 Speed-torque (mechanic) characteristic when load current is continuous EM Cen (10-2) For 3-phase half-wave Ud 1.17U 2 cos a 3X I (RB+RM+ 2B ) Cd e n EM 1.17U 2 cos a R Id U a1 Power (10-3) a2 1.17U 2 cos a R Id U n Ce Ce (10-4) For 3-phase bridge a3 a1<a2<a3 O Id For 3-phase half-wave 2.34U 2 cos a R n Id (10-5) Ce Ce 5 Speed-torque (mechanic) characteristic when load current is discontinuous EMF at no load (taking 3-phase half-wave as example) For a 60º Power E 0 2U 2 For a > 60º E E0 ( 2U2) E0' (0.585U2) E0 2U 2 cos(a 60 ) Idmin O discontinuouts mode continuous mode Id For 3-phase half-wave 6 Speed-torque (mechanic) characteristic when load current is discontinuous For different a Power The point of EMF at no load is raised up. E E0 boundary a1 a2 a3 a4 The droop rate becomes steer. (softer than the continuous mode) a5 discontinuous mode continuous mode O Id For 3-phase half-wave (a1< a2 < a3 60º, a5 > a4 > 60º) 7 10.1.2 Inverter mode of operation – are just the same as in the rectifier mode of operation except that Ud, EM and n become negative. E.g., in 3-phase half-wave Power EM 1.17U 2 cos a R Id U rectifier mode a1 a2 a3 a4 a =b = 2 (10-3) n 1.17U 2 cos a R Id U Ce Ce – Or in another form (10-4) E M (U d 0 cos b I d R ) (10-11) n 1 Ce U d 0 cos b IdR (10-12) a increasing n Id b4 b3 b2 inverter mode b increasing Equations b1 Speed-torque characteristic of a DC motor fed by a thyristor rectifier circuit 8 10.1.3 Reversible DC motor drive system (4-quadrant operation) +n converter 2 inverting converter 1 rectifying Id Id + L a b c converter 1 Power M EM converter 1 + EM M - Energy Udb - AC AC source source converter2 converter1 + Energy Uda forward braking(regenerating) converter 2 -T Back-to-back connection of two 3phase bridge circuits Id converter 1 EM M + - Energy Uda converter2 forward motoring O converter 2 rectifying + M E M - converter 1 inverting AC AC source source + converter2 converter1 - Id Energy + +T Udb M EM + converter2 reverse braking(regenerating) reverse motoring -n 9 4-quadrant speed-torque characteristic of Reversible DC motor drive system converter 2 n converter 1 a1 b'2 a3 a '=b '= 2 a'4 a'3 a'2 a'1 a increasing a2 b'3 b'4 a4 a =b = 2 Id b4 b3 b2 a1=b '1; a '1=b1 a2=b '2; a '2=b2 b1 b increasing a 'increasing Power b 'increasing b'1 10 10.2 Frequency converters and AC drivers Composite converter: Combination of two or more converters in cascaded connection Power Indirect AC to AC converters (AC-DC-AC converters) Composite converters Indirect DC to DC converters (Isolated DC to DC converters) 11 Indirect AC to AC converters (AC-DC-AC converters) Classifications According to type of the DC links: AC-DC-AC converters Voltage-source type Current-source type Power According to whether output voltage and frequency is variable: AC-DC-AC converters Variable voltage variable frequency (VVVF) (AC-DC-AC frequency converters) Constant voltage constant frequency (CVCF) In narrow sense, frequency converter only refers to VVVF AC-DC-AC converter. 12 10.2.1 Configurations of AC-DC-AC converters Configurations with one-direction power flow Power AC Source Voltage-source type AC Load AC Source AC Load Current-source type 13 Configuration with regenerative energy dissipating circuit Power AC Source V0 AC Load R0 Braking transistor and braking resistor 14 Configurations with regenerative power feedback through inversion-mode thyristor rectifier circuit Id Power AC Source AC Load Voltage-source type AC Source Ud UL AC Load Current-source type 15 Configurations realizing bi-directional power flow through double-sided PWM converters Source Power AC Source AC Load Voltage-source type Load a b c U V W Current-source type 16 10.2.2 Major Applications of AC-DC-AC frequency converters (VVVF converters) Power Adjustable speed AC motor drives Advantages of AC motors over DC motors Energy saving on AC motors High-performance AC motor drives Control of AC motors driven by AC-DC-AC frequency converters (VVVF converters) Constant voltage frequency ratio control Slip frequency control Vector control Direct torque control 17 10.3 Uninterruptible power supplies (UPS) Basic configuration of UPS Rectifier Inverter Power Electricity utility Load Source Major Applications of CVCF converters 18 UPS with back-up energy source Electricity utility Rectifier Power S Diesel Engine Inverter 1 Load 2 Source 19 UPS with back-up energy source and bypass lines Bypass lines Power Electricity utility Rectifier S1 Diesel Engine Inverter 1 Load 3 4 S2 2 Source 20 10.4 Switching Power Supply Linear power supply Line Line frequency frequency AC input DC Transformer Rectifier Filter Series Pass Regulator Regulated DC output Power Isolation • Switching power supply High frequency AC Line frequency AC input Rectifier DC Filter Inverter High frequency AC Transformer Rectifier Filter Regulated DC output Isolation Indirect DC to DC converter 21 Point of load regulation (POL) Power Specifically means a particular switching power supply for a large size IC chip, such as a CUP or a memory chip. Synchronous Buck Synchronous Boost 22 Power A typical application of switching power supply Power system for telecommunication equipment 23 Control of switching power supply Voltage mode control Current mode control Power – Peak current mode control – Average current mode control 24 Power Voltage mode control 25 Power Current mode control 26 Power Peak current mode control 27 Power Average current mode control 28 10.5 Power Factor Correction (PFC) Operation principle of typical PFC circuit – Single-phase boost PFC – 3-phases single-switch boost PFC Power Single stage PFC 29 Power Single-phase boost PFC 30 Power 3-phases single-switch boost PFC 31 Power Single stage PFC ( S 2 PFC ) A typical S 2 PFC converter 32 Power 10.6 Application in utility power system High voltage DC transmission (HVDC) Reactive power compensation Harmonics suppression Power quality control, FACTS and custom power 33 Power High voltage DC transmission (HVDC) 34 Reactive power compensation Power Thyristor switched capacitor (TSC) Thyristor controlled reactor (TCR) Static var generator (SVG) 35 Thyristor switched capacitor (TSC) I Power U 36 TSC waveforms when the capacitor is switched in/out us uVT 1 iC Power us uC uC C uVT1 t t VT1 VT2 iC t VT1 VT2 t t1 t2 The voltage across the thyristor must be nearly zero when switching in the capacitor, and the current of the thyristor must be zero when switching out the capacitor. 37 Power TSC with the electronic switch realized by a thyristor and an anti-parallel diode The capacitor voltage will be always charged up to the peak of source voltage. The response to switching-out command could be a little slower (maximum delay is one line-cycle). 38 Thyristor-controlled reactor (TCR) To control the effective current flowing through the reactor by controlling delay angle, therefore control the reactive power absorbed by the reactor. Power ua n ia a b ub c uc a) b) c) 图4-12 39 Static var generator (SVG) Power Also called static compensator (STATCOM) VSC based SVG CSC based SVG 40 Power Operation principle of SVG 41 Harmonic suppression Harmonic compensation Power Two solutions Power factor correction Circuit configuration of an Active power factor (APF) 42 Power Operation principle of APF 43 Power Power quality control Power quality problems Power quality controllers Current harmonics APF Reactive power SVC or SVG Voltage sag Dynamic voltage restorer (DVR) Voltage flicker Universal power quality controller (UPQC) 44 Power Flexible AC Transmission System (FACTS) FACTS is actually a general term of application if power electronic to the utility electric power transmission system - for higher controllability and larger transmission capacity. Typical FACTA devices – SVC – SVG – Thyristor Switched Series Capacitor (TSSC) – Thyristor Controlled Series Compensator (TCSC) – Static Synchronous Series Compensator (SSSC) – Unified Power Flow Controller (UPFC) 45 Power Custom Power Custom power is a general term of application of power electronics to the utility electric power distribution system for better quality and higher reliability of the power supplying to different customers. Typical Custom Power devices – SVC or SVG (D-STATCOM) – DVR – APF – Solid State Transfer Switch (SSTS) 46 10.7 Other applications Power Lighting – Power supply for different lamps – Power supply for gas discharge lamps is specifically called ballast. Typical configuration of an electronic ballast Welding Typical configuration of a welding power supply 47