Power Electronic Converters, 1993
DC-AC Conversion
Electric Energy Systems and Engineering Series

This is the final volume in a four-volume series concerning POWER ELEC­ TRONIC CONVERTERS. The first volume studies AC/DC conversion, the second studies AC/ AC conversion, and the third DC/DC conversion. This final volume deals with DC/AC conversion, i.e. with inverters. At the output of an inverter fed by a DC voltage supply, this voltage is alternatively found with one polarity and then with the other; in other words, an AC voltage made up of square pulses is obtained. Filtering must be carried out if, as is normally the case, a virtually sinusoidal voltage is required: this problem of filtering underlies the entire study of inverters. In some applications, the load itself provides the filtering. In others, a filter is installed between the inverter and the load; however, as it will be shown in Chap. 2, in cases where the filtered voltage is at industrial network frequency and comprises only a single square-wave pulse per half-cycle, the filter becomes bulky and costly, and the results obtained are poor. Filtering problems explain the considerable development of inverters during the last years: - Firstly there is increasing use of pulse width modulation: each half-cycle is cut up into several pulses of suitable widths; this greatly simplifies filtering. The use of a chopping frequency which is much greater than the frequency of the fundamental components of the inverter output voltage and current has only been made possible by progress in the field of semiconductor devices.

1 Introduction and Presentation.- 1.1 Types of Inverters: Principles.- 1.1.1 Voltage-Source Inverters.- 1.1.2 Current-Source Inverters.- 1.1.3 Resonant Load Inverters.- 1.2 Types of Semiconductor Devices. Supply and Load Imperfections. Filters.- 1.2.1 Types of Semiconductor Devices.- 1.2.2 DC-Supply Imperfection. Input Filter.- 1.2.3 AC-Load Imperfection. Output Filter.- 1.2.4 Remarks on Reversibility.- 1.3 Principal Applications. Consequences on the Study.- 1.3.1 Constant Frequency and Voltage Supplies.- 1.3.2 Speed Variation of AC-Current Motors.- 1.3.3 Load-Resonant Inverter Applications.- 2 Voltage-Source Inverters with One Square-Pulse per Half-Cycle.- 2.1 Single-Phase Inverter with Centre-Tapped Transformer.- 2.1.1 Principle.- 2.1.2 Characteristics.- 2.2 Single-Phase Half-Bridge Inverter.- 2.2.1 Principle.- 2.2.2 Characteristics.- 2.3 Single-Phase Full-Bridge Inverter.- 2.3.1 Principle.- 2.3.2 Characteristics.- 2.3.3 Comparison of the Three Single-Phase Voltage-Source Inverters.- 2.4 Three-Phase Full-Bridge Inverter.- 2.4.1 Balanced Mode Operation.- 2.4.2 Balanced Operation Characteristics.- 2.4.3 Delta-Connected AC Load.- 2.4.4 Operation with an Unbalanced Load.- 2.5 Input Filter.- 2.5.1 Input Current and Output Voltage Harmonics.- 2.5.2 Application to the Different Inverters.- 2.5.3 Remark Concerning the Use of the Half-Bridge Inverter Divider as an Input Filter Element.- 2.6 Output Filter.- 2.6.1 General Equations.- 2.6.2 Effects of the Filter on the Fundamental.- 2.6.3 Effects of the Filter on the Harmonics.- 2.6.4 Choosing L and C.- 2.6.5 Notes on Other Filters.- 2.6.6 Notes on Variable Frequency-Supplied Loads.- 3 Pulse-Width-Modulated Voltage-Source Inverters.- 3.1 Single-Phase Half-Bridge Inverter.- 3.1.1 “Switch” Control. Waveforms.- 3.1.2 Output Voltage.- 3.1.3 Currents.- 3.1.4 Remarks on Control Phase Lock and on Asynchronous Modulation.- 3.2 Three-Phase Full-Bridge Inverter.- 3.2.1 “Switch” Control. Waveforms.- 3.2.2 Sinusoidal Reference.- 3.2.3 Injection of Harmonic 3 into the Reference.- 3.2.4 Other Modifications of the Control Law.- 3.3 Single-Phase Full-Bridge Inverter.- 3.3.1 “Switch” Control. Waveforms.- 3.3.2 Study of the Output Voltage.- 3.3.3 Study of the Currents.- 3.3.4 Digital Reference.- 3.4 Computed Modulation.- 3.4.1 Characterising the Output Voltage.- 3.4.2 Eliminating the First Harmonics of the Output Voltage.- 3.4.3 Minimising the Weighted Harmonic Rate.- 3.4.4 Control of the Full-Bridge Inverter by Shifting the Voltage of the Two Half-Bridges.- 4 Commutations in Voltage-Source Inverters.- 4.1 Commutation of the Bipolar Transistor in Full-Wave Inverters.- 4.1.1 Commutation Process with RC Snubber.- 4.1.2 Computing the Losses.- 4.2 Commutations of the Bipolar Transistor in PWM Inverters.- 4.2.1 Commutation at Turn-On.- 4.2.2 Commutation at Turn-Off.- 4.2.3 Power Dissipated in the Resistances.- 4.2.4 Remarks on Reverse Conduction in the Transistor.- 4.3 GTO Thyristor Commutations.- 4.3.1 Commutation at Turn-On.- 4.3.2 Commutation at Turn-Off.- 4.3.3 Power Dissipated in the Resistance.- 4.4 Field Effect Transistor Commutations.- 4.4.1 ON-Commutation.- 4.4.2 OFF-Commutation.- 5 Current-Source Inverters.- 5.1 Single-Phase Inverters.- 5.1.1 Inverters with a Centre-Tapped Transformer.- 5.1.2 Full-Bridge Inverter with One Square-Wave Pulse per Alternance.- 5.1.3 PWM-Controlled Full-Bridge Inverter.- 5.1.4 Remarks on PWM Current-Source Inverters.- 5.2 Full-Bridge Three-Phase Inverter.- 5.2.1 Full-Wave Control.- 5.2.2 PWM Control with Sinusoidal Modulation.- 5.2.3 PWM Control with Computed Modulation.- 5.3 Feeding an Inductive Load.- 5.3.1 Thyristor Current-Source Inverter with Auxiliary Commutation Bridge.- 5.3.2 Self-Commuted Current-Source Inverter with Thyristors.- 5.3.3 GTO Current Inverter with Clamping Circuit.- 5.4 Notes on the Configurations with a Pulse Number Greater than 6.- 5.4.1 Configuration with Pulse Number Equal to 12.- 5.4.2 Configuration with Pulse Number Equal to 18.- 5.5 Notes on the Computation of the Current-Source Inverter Input Filter.- 6 Resonant Inverters.- 6.1 Series Resonant Inverter.- 6.1.1 Response of the Series Resonant Circuit to a Square-Wave Voltage.- 6.1.2 First Harmonic Method.- 6.1.3 Operation and Control of the Inverter.- 6.1.4 Characteristics.- 6.1.5 Starting. Protection.- 6.1.6 Variants.- 6.2 Parallel Resonant Inverter.- 6.2.1 Response of the Parallel Resonant Circuit to a Square-Wave Current.- 6.2.2 Inverter Operation and Control.- 6.2.3 Characteristics.- 6.2.4 Starting. Protection.- 6.2.5 Variants.- 6.3 Resonant Supplies.- 6.3.1 Supply with a Series Resonant Inverter.- 6.3.2 Supply with a Series-Parallel Resonant Inverter.- 6.3.3 Double Resonance Supplies.- Appendices.- Appendix A: Input Filter in Voltage-Source Inverters.- A.1 Inverters with Two “Switches” per Phase.- A.2 Full-Bridge Single-Phase Inverter.- Appendix B: “Sinusoidal” Voltage-Source Inverters.- B.1 Voltage Waveform.- B.2 Production of Optimized Waveforms.- B.3 Variation in the Output Voltage.- B.4 The most Usual Type of Configuration.- Appendix C: Forced Turn-Off of Thyristors in Voltage-Source Inverters.- C.1 Parallel Commutation by Oscillating Circuit.- C.2 Parallel Commutation by Capacitor.- C.3 Series Commutation.- Appendix D: PWM Rectifier.- D.1 The Structure.- D.2 The Converter Alone.- D.3 The Converter and its Input Filter.- D.4 The Converter with its Input and Output Filters.- Appendix E: Use of the Four-Quadrant Chopper as a PWM Rectifier.- E.1 “Switch” Control.- E.2 Current Harmonics Taken from the Supply.