电力电子技术双语课件第4章

1、Power ElectronicsChapter 4 DC to AC Converters( Inverters )Power ElectronicsChapter 4 Applications of InvertersConversion of electric power from DC type energy sources to AC type loadBatteryPhotovoltaic cell (Solar cell)Fuel cellAs a part of composite converterAC-DC-AC frequency converter (for AC mo

2、tor drive)AC-DC-AC constant-voltage constant-frequency converter (for uninterruptable power supplies)AC-DC-AC Converters for induction heatingAC-DC-AC-DC switching power suppliesApplications of InvertersConveOutline4.1 Commutation4.2 Voltage source inverters4.3 Current source inverters4.4 Multiple-i

3、nverter connections and multi-level inverters Outline4.1 Commutation4.1 Commutation typesA classification of invertersSquare-wave inverters (are discussed in this chapter)PWM inverters ( will be discussed in Chapter 6)The concept of commutationBasic operation principle of invertersLoadS1S2S3S4iouoUd

4、4.1 Commutation typesA classif4 types of commutation Device commutation: Fully-controlled devices: GTO, IGBT, MOSFET Line commutation Phase-controlled rectifier Phase-controlled AC controller Thyristor cycloconverter Load commutation Forced commutation4 types of commutation Device Load commutation C

5、ondition: Load current is leading load voltage Application: capacitive load, synchronous motorLoad commutation Condition: Lo Forced commutation (capacitance commutation)Direct-CoupledWith Coupling-Inductor Forced commutation (capacitAnother classification of commutationsSelf-commutationDevice commut

6、ationForced commutationLine commutationLoad commutation4 types of CommutationsExternal commutationFor fully-controlled devicesFor thyristorsAnother classification of comm2 classes of invertersVoltage Source Inverter (VSI)Current Source Inverter (CSI)2 classes of invertersVoltage 4.2 Voltage source i

7、nverter (VSI) DC side is constant voltage, low impedance (voltage source, or bulk cap) AC side voltage is square wave or quasi-square wave. AC side current is determined by the load. Anti-parallel diodes are necessary to provide energy feedback path. (freewheeling diodes , feedback diodes)+-CRLUdV1V

8、2V3V4VD1VD2VD3VD4uoioFeatures4.2 Voltage source inverter (VSingle-phase half bridge VSI The current conducting path is determined by the polarity of load voltage and load current. (This is true for analysis of many power electronics circuits.)-RLUdiouoV1V2VD1VD2Ud2Ud2The magnitude of output square-w

9、ave voltage is Ud/2.uoUmiot1t2t3t4t5t6V1V2V1V2VD1VD2VD1VD2UG1UG2Single-phase half bridge VSI Single-phase full bridge VSIOperation principle+-CRLUdV1V2V3V4VD1VD2VD3VD4uoio The magnitude of output square-wave voltage is Ud. The effective value of output voltage (or fundamental output voltage) can be

10、changed by changing Ud.uoUmiot1t2t3t4t5t6V1V2V1V2VD1VD2VD1VD2UG1,4UG2,3VD4VD3VD4VD34343VVVV Single-phase full bridge VSIOFourier series extension of output voltageMagnitude of output voltage fundamental component Effective value of output voltage fundamental component Single-phase full bridge VSIQua

11、ntitative analysis(4-1)(4-2)(4-3)Fourier series extension of ou Single-phase full bridge VSI Output voltage control by phase-shift+-CRLUdV1V2V3V4VD1VD2VD3VD4uoio Single-phase full bridge VSI Inverter with center-tapped transformerpush-pull inverterInverter with center-tapped tr Three-phase VSI 180o

12、conduction Dead time (blanking time) to avoid “shoot through” Three-phase VSI 180o conducti Three-phase VSIBasic equations to obtain voltage waveformsFor line voltageFor phase voltage of the load Three-phase VSIBasic equationThree-phase VSIFourier series extension of output line-to-line voltageMagni

13、tude of output voltage (line-to-line) fundamental component Effective value of output voltage (line-to-line) fundamental componentQuantitative analysis(4-8)(4-10)(4-11)Three-phase VSIFourier series 4.3 Current source inverter (CSI) DC side is constant current, high impedance (current source, or larg

14、e inductor) AC side current is quasi- square wave. AC side voltage is determined by the load. No anti-parallel diodes are needed. sometimes series diodes are needed to block reverse voltage for other power semiconductor devices.Features4.3 Current source inverter (CSingle-phase bridge CSIParallel Re

15、sonant Inverter ACRLLdIdVT1VT2VT3VT4LT1LT2LT3LT4uoio Switching frequency is a little higher than the resonant frequency so that the load becomes capacitive and load current is leading voltage to realize load commutation.Single-phase bridge CSIParalleThree-phase self-commutated CSI 120o conductionThr

16、ee-phase self-commutated CSThree-phase force-commutated CSIThree-phase force-commutated CThree-phase load-commutated CSIThree-phase load-commutated CS4.4 Multiple-inverter connections and multi-level invertersSeries connection of 2 single-phase VSIs4.4 Multiple-inverter connectiSeries connection of

17、2 3-phase VSIsSeries connection of 2 3-phaseMulti-level InvertersWays to deal with higher voltage and achieve better waveformSeries connection of multiple convertersSeries connection of multiple switch devicesMajor type of multi-level invertersNeutral point clamped multi-level inverterFlying-capacitor multi-level inverterCascade H-bridge( series connected H-bridges)In broad sense, previously discussed series connection of multiple inverters is also called multi-level inverter.In narrow sense, only NPC and FC structures are called multi-level inverters.Multi-le