电力电子技术第5版教学课件作者王兆安刘进军chapter04课件幻灯片.ppt

Series connection of 3 H-bridges Power Electronics Chapter 4 DC to AC Converters( Inverters ) Applications of Inverters Conversion of electric power from DC type energy sources to AC type load Battery Photovoltaic cell (Solar cell) Fuel cell As a part of composite converter AC-DC-AC frequency converter (for AC motor drive) AC-DC-AC constant-voltage constant-frequency converter (for uninterruptable power supplies) AC-DC-AC Converters for induction heating AC-DC-AC-DC switching power supplies Outline 4.1 Commutation 4.2 Voltage source inverters 4.3 Current source inverters 4.4 Multiple-inverter connections and multi-level inverters 4.1 Commutation types A classification of inverters Square-wave inverters (are discussed in this chapter) PWM inverters ( will be discussed in Chapter 6) The concept of commutation Basic operation principle of inverters Load S 1 S 2 S 3 S 4 i o u o U d 4 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 commutation Load commutation Condition: Load current is leading load voltage Application: capacitive load, synchronous motor Forced commutation  (capacitance commutation) Direct-Coupled With Coupling-Inductor Another classification of commutations Self-commutation Device commutation Forced commutation Line commutation Load commutation 4 types of Commutations External commutation For fully-controlled devices For thyristors 2 classes of inverters Voltage Source Inverter (VSI) Current Source Inverter (CSI) 4.2 Voltage source inverter (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. (freew