Analysis and Design of Multicell DC/DC Converters Using Vectorized Models

Thierry Meynard is Directeur de Recherches CNRS at Laboratoire LAPLACE, ENSEEIHT, INPT, University of Toulouse, France and part-time consultant at CIRTEM (Centre d'ingénierie et de recherche en technologies de l'électrotechnique moderne). He is the co-inventor of various topologies of series multicell (multilevel) converters and has been involved in the transfer of several of these topologies to industry, especially in the field of medium voltage drives (typ. 1-10kV, 1-10MW). In recent years his research interests have focused on parallel multicell (interleaved) converters for application in low voltage embedded applications (<1kV) and on the design of corresponding magnetic components.

• CHAPTER 1. GENERAL PROPERTIES OF MULTILEVEL CONVERTERS 11.1. Time-domain: multilevel waveform and apparent switching frequency 11.2. Frequency domain: harmonic cancellation 41.3. Transient response 51.4. Conclusion 6CHAPTER 2. TOPOLOGIES OF MULTILEVEL DC/DC CONVERTERS 92.1. Series connection 92.1.1. Direct series connection with isolated sources 92.1.2. Flying capacitor 112.2. Parallel connection 142.2.1. Interleaved choppers with star-connected inductors 142.2.2. Interleaved choppers with InterCell Transformers (ICTs) 172.3. Series-parallel connection 20CHAPTER 3. CONCEPT OF VECTORIZATION IN PLECS 233.1. Vectorized components 233.2. Star-connection block and parallel multicell converter 253.3. Series connection block and series multicell converter 273.4. Generalized multicell commutation cell 283.5. Practice 343.5.1. How to? 343.5.2. Basic blocks 34CHAPTER 4. VECTORIZED MODULATOR FOR MULTILEVEL CHOPPERS 374.1. General principle 374.2. xZOH: equalizing multisampler for multilevel choppers 384.2.1. Control as the main source of perturbation 384.2.2. Handling duty cycle variation 384.2.3. Frequency response of the equalizing sampler and modulator 514.3. Practice 53CHAPTER 5. VOLTAGE BALANCE IN SERIES MULTILEVEL CONVERTERS 575.1. Basic principles 575.2. Linear circuits 585.2.1. Internal balancers 585.2.2. External balance boosters 595.2.3. Pros and cons of internal/external balance boosters 645.3. Nonlinear variants 655.3.1. Internal balance boosters 655.3.2. External balance boosters 665.4. Loss-based design 675.4.1. Introduction 675.4.2. Internal balance boosters 685.4.3. External balance boosters 685.5. Vectorized models of balance boosters 69CHAPTER 6. FILTER DESIGN 756.1. Requirements 756.1.1. Steady state: current ripple, voltage ripple and standards 756.1.2. Transients 836.1.3. Extra design constraints 846.2. Design process 85CHAPTER 7. DESIGN OF MAGNETIC COMPONENTS FOR MULTILEVEL CHOPPERS 897.1. Requirements and problem formulation 897.2. Area product 927.2.1. Low frequency – low ripple formulation for filtering inductors 927.2.2. General formulation for filtering inductors 947.2.3. Application to inductors for interleaved converters 957.2.4. Extension to InterCell Transformers 977.3. Optimal area product of magnetic components for interleaved converters 997.3.1. Optimal area product for inductors 997.3.2. Optimal area product for InterCell Transformers 1017.4. Weight-optimal dimensions for a given area product 1017.4.1. For inductors 1017.4.2. For InterCell Transformers 1077.5. Volume-optimal dimensions for a given area product 1187.6. Number of turns and air gap 1207.7. Accounting for current overload 1237.8. Optimal phase sequence for InterCell Transformers 1237.9. Vectorized reluctance model of magnetics 1257.9.1. Inductors 1257.9.2. Cyclic cascade InterCell Transformers 1267.9.3. Monolithic InterCell Transformers 1287.10. Design process 130CHAPTER 8. CLOSED-LOOP CONTROL OF MULTILEVEL DC/DC CONVERTERS 1318.1. Principle 1318.2. Corresponding PLECS block 1338.3. Average model of the macrocommutation cell for transient studies 1368.4. Conclusion 140BIBLIOGRAPHY 141INDEX 145