Copyright is owned by the Author of the thesis. Permission is given for a copy to be downloaded by an individual for the purpose of research and private study only. The thesis may not be reproduced elsewhere without the permission of the Author. An Analysis of the Influences of Power Electronics Devices on Fundamental Frequency Front Ends A thesis presented in partial fulfilment of the requirements for the degree of Master of Engineering in Mechatronics at Massey University, Palmerston North, New Zealand Sascha Beck April, 2010 ii iii Abstract New power electronics devices like Fundamental Frequency Front Ends (F3E) reduce procurement costs by eliminating or reducing the intermediate capacitors usually found on the DC-side of modern rectifier-inverter combinations. This cost-saving measure, however, eliminates the quasi-decoupling of rectifier and inverter; whereas interactions between rectifier and inverter could be neglected in most applications. These interactions are relevant to the correct function and operation of the whole application in case of reduced intermediate capacitors. Without the decoupling of rectifier and inverter, the inverter input currents will be passed on to the rectifier, and ultimately, will be discernible on the power grid. As a result, the input currents of the appliance will deviate greatly from the idealised sinusoidal waveform. To reduce this effect, an input filter is used, which in turn might interact with other power electronics devices connected to the same power grid. To date, the scope of the rectifier inverter and the F3E third-party equipment interactions has not been sufficiently investigated. An examination with real devices is impractical due to the wide range of configurations possible and the potential harm to the equipment itself. In this study, the simulation models of the devices involved and the power grid connecting different appliances were developed. A theoretical analysis to identify possible areas of impaired or disturbed operation was undertaken. The areas identified were then analysed using the computer models developed. The simulation results, electrical currents, and voltages were examined with regards to their absolute values and their degree of deviation from the idealised sinusoidal form. Their harmonic spectra were likewise analysed. Finally, areas of disturbed operation and the conditions under which they occur were identified. This study, therefore, will provide the basis for the successive elimination of these areas of disturbed operation. iv Acknowledgments I would like to express my appreciation to my advisor, Dr. Liqiong Tang for her guidance, invaluable suggestions, and enthusiasm during this research. My sincere thanks to Dr. Michael Peppel for his helpful advice during the design of the simulation models. I also would like to thank all the staff at the School of Engineering and Advanced Technology, Massey University Palmerston North in New Zealand. Finally, I would like to thank my girlfriend, Lena for her support, understanding and belief in me during this work. v Table of contents Abstract iii Acknowledgements iv Table of contents v List of figures vii List of tables xi 1 Introduction 1 2 Review of literature 2 2.1 Classification of voltage levels 3 2.2 Transformer 4 2.3 Power electronics 5 2.4 Inverter 5 2.4.1 Control algorithms 9 2.5 Active Front End (AFE) 10 2.6 Alternative configurations 11 2.7 Fundamental Frequency Front End (F3E) 11 2.8 Higher harmonics 13 2.9 NETASIM 13 3 Model development 15 3.1 Structure of the F3E model 15 3.1.1 Structure of the basic model 15 3.1.2 Extension of the model to the F3E 19 3.2 The PCI model 28 3.2.1 Generation of the PWM signal 29 3.2.2 Model of the PCI circuit 33 3.2.3 Modification of the programmed PWM 33 3.3 Combination of the F3E and the PCI models 35 3.4 Optimisation of the load behaviour 39 3.5 The AFE model 42 3.5.1 Testing the model functionalities 46 3.6 Mains model used 48 4 Research implementation 51 4.1 Aspects of the research 51 vi 4.1.1 Investigation of the F3E_PWR model 51 4.1.2 Investigation of the anti-resonant circuit 55 4.2 Simulations and data evaluation 63 4.2.1 Range of grid parameter examined 63 4.2.2 Model simulation at a selected critical parameter configuration 64 5 Configuration of the AFE and F3E connected to the same mains 75 5.1 Examination of the model including F3E and AFE 75 5.1.1 Influence of the F3E on the AFE_F3E model 76 5.1.2 Influence of the AFE on the AFE_F3E model 78 5.2 Simulation of the model outside the areas of disturbance 81 5.2.1 Model parameters for the simulation 81 5.2.2 Analysis of simulation results 82 5.3 Model simulation in areas of expected disturbance 88 5.3.1 Operation with the resonant frequency of series resonant circuit 88 5.3.2 Analysis of the resulting current shapes 89 5.3.3 Analysis of the resulting higher harmonics 91 5.3.4 Operation at parallel resonant frequency 96 5.3.5 Analysis of the current shapes for Rsce=96 and Rsce=1164 100 5.3.6 Analysis of the higher harmonics spectra 104 6 Conclusions 111 Appendices 113 Bibliography vii List of figures Fig. 2.1 Single-phased alternate circuit diagram of a transformer 4 Fig. 2.2 Simplified single-phased alternate circuit diagram 5 Fig. 2.3 Topology with voltage source inverter 6 Fig. 2.4 Topology with current source inverter 6 Fig. 2.5 Internal topology of a VSI with an AC drive as load 6 Fig. 2.6 A simplified VSI topology 7 Fig. 2.7 Definition of the logical states and the associated flow of current 8 Fig. 2.8 Generation of the PWM signal 10 Fig. 2.9 The AFE with line inductors and intermediate capacitor C 11 Fig. 2.10 A B6 rectifier topology 12 Fig. 2.11 Topology of the F3E 12 Fig. 3.1 Diagram of the programmed B6 bridge 17 Fig. 3.2 The line current (INETZ) and mains voltage (UNETZ) of the first circuit 18 Fig. 3.3 The load voltage (URL) and the load current (IRL) 19 Fig. 3.4 Diagram of a single-phased input filter 20 Fig. 3.5 The B6 rectifier with the implemented F3E filter 21 Fig. 3.6 The mains voltage (UNETZ) and line current (INETZ) of the extended circuit 21 Fig. 3.7 The mains voltage (UNETZ) and line current (INETZ) with a reduced LNETZ 22 Fig. 3.8 Network lists entry for a GPV macro and alternate circuit diagram 22 Fig. 3.9 The F3E circuit 24 Fig. 3.10 Extended circuit with a DC current source and a small intermediate circuit capacitor 28 Fig. 3.11 Shape of line current (INETZ), mains voltage (UNETZ), and the adjusted direct current (DCSTROM) 29 Fig. 3.12 Schematic representation of a triangle signal 30 Fig. 3.13 Triangular voltage DR, the reference value UST1, and the resulting values for STS1 32 Fig. 3.14 Alternate circuit diagram of the programmed circuit 33 viii Fig. 3.15 Current and voltage shapes of the PCI model with a small load inductor LLAST 34 Fig. 3.16 Current and voltage shapes of the PCI model with a large load inductor LLAST 34 Fig. 3.17 The alternate circuit diagram without supply grid resulting from the new net-list 35 Fig. 3.18 The line current, mains voltage, and intermediate circuit voltage with error 36 Fig. 3.19 Placement of the shunts in the model 36 Fig. 3.20 Shapes of line current and voltage after consolidation of the control 40 Fig. 3.21 One-phased representation of an alternate circuit diagram of the motor 41 Fig 3.22 Voltage vector diagram based on the calculations in Listing 3.21 41 Fig. 3.23 Three-phased alternate circuit diagram of the load model 42 Fig. 3.24 Output waveforms of the PCI with the new load 43 Fig. 3.25 Alternate circuit diagram of the AFE circuit with line reactors LAFE1 to 3 43 Fig. 3.26 Shapes of the UPWM1, the AFDR, and the PWM signal AREG1 46 Fig. 3.27 Shape of the intermediate voltage using the parameter values of Kp and KI 47 Fig. 3.28 Change from motor operation to generator operation of the AFE 48 Fig. 3.29 Simplified alternate circuit diagram of a power supply line 49 Fig. 3.30 Simple mains model 49 Fig. 3.31 Expanded mains configuration 50 Fig. 4.1 Three line-currents of the power-supply line INETZ of the F3E filter, ICRS, and IF3EL1 52 Fig. 4.2 Harmonic spectra from 0Hz to 1250Hz 53 Fig. 4.3 Harmonic spectra from 15.3kHz to 17.3kHz 53 Fig. 4.4 Schematic diagram of a one-phased circuit 54 Fig. 4.5 One-phased alternate circuit diagram for determining the resonant frequency 54 Fig. 4.6 Alternate circuit diagram including the series resistor RCREIHE 54 Fig. 4.7 Bode diagram of the frequency response of the impedance 56 Fig. 4.8 Alternate circuit with the transformed components RNETZ_PAR and 56 ix LNETZ_PAR Fig. 4.9 The quality Q as a function of the grid PF and of Rsce 60 Fig. 4.10 Enlargement of the lower range of Rsce from Fig. 4.9 60 Fig. 4.11 Resonant frequency over Rsce with different PF values 61 Fig. 4.12 The quality Q over Rsce with PF=0.01 62 Fig. 4.13 Shapes of the net and filter voltages, and currents 65 Fig. 4.14 Shapes of ICRS and INETZ for a duration of 40ms (Rsce=721, PF=0.8, f0=4kHz) 66 Fig. 4.15 INETZ and ICRS under normal operation for a duration of 40ms (Rsce=750, PF=0.2, f0=3.175kHz) 66 Fig. 4.16 Current shape of the F3E under distorted operational conditions for a duration of 40ms 67 Fig. 4.17 Current shape of the F3E under normal operational conditions for a duration of 40ms 67 Fig. 4.18 Spectra of the three currents in the frequency range 0Hz to 1.85kHz 68 Fig. 4.19 Harmonic analysis of the three currents INETZ, ICRS, and IF3E 70 Fig. 4.20 Current and voltage shapes of grid and filter components 72 Fig. 4.21 Shapes of INETZ and ICRS for a duration of 40ms 73 Fig. 4.22 Current shape of the IF3E for a duration of 40ms 73 Fig. 4.23 The harmonic spectra within the range 3.5kHz and 4.5kHz 73 Fig. 5.1 Schematic diagram of the complete model AFE_F3E 75 Fig. 5.2 Single-phased alternate circuit diagram of the AFE_F3E model 76 Fig. 5.3 Alternate circuit for analysing the current source effects 77 Fig. 5.4 The resulting alternate circuit with mains components in serial configuration and trap circuit 77 Fig. 5.5 Alternate circuit with resonant circuit 78 Fig. 5.6 Voltage vector diagram of a resonant circuit in case of resonance 79 Fig. 5.7 Alternate circuit diagram with parallel resonant circuit 80 Fig. 5.8 Shapes of mains current and voltage 83 Fig. 5.9 Shapes of the inductor current ILAF of the AFE and input voltage UPWM_AFE 83 Fig. 5.10 Shapes of the F3E input voltage and currents (filter voltage UCRS, filter current ICRS, F3E current without filter IF3E, and F3E line current ILNF) 84 Fig. 5.11 Spectra of the higher harmonics of currents ILAF and INETZ 85 x Fig. 5.12 Higher harmonics of INETZ and ILAF in the frequency range 3.5kHz to 4.5kHz 86 Fig. 5.13 Higher harmonics of the currents ILNF, ICRS, und IF3E 86 Fig. 5.14 Higher harmonics of the currents ICRS, ILNF, and IF3E of the model without AFE 87 Fig. 5.15 Shapes of grid currents ILNF, ILAF, and INETZ 89 Fig. 5.16 Shapes of the F3E input currents IF3E, ICRS, and ILNF 90 Fig. 5.17 Shape of the F3E input currents IF3E, ICRS, and ILNF with an Rsce=750 91 Fig. 5.18 Higher harmonics range of the F3E input currents from 3.5kHz to 4.5kHz for an Rsce=33 92 Fig. 5.19 Higher harmonics range of the F3E input currents from 3.5kHz to 4.5kHz for an Rsce=750 93 Fig. 5.20 Higher harmonics range of the currents INETZ, ILAF, and ILNF from 3.5kHz to 4.5kHz for an Rsce=33 93 Fig. 5.21 Higher harmonics range of the currents INETZ, ILAF, and ILNF from 3.5kHz to 4.5kHz for an Rsce=750 94 Fig. 5.22 The ILAF, INETZ, and ILNF of the 38th harmonic as a function of Rsce 94 Fig. 5.23 Actual value of the filter current ICRS 95 Fig. 5.24 Actual value of the currents ILNF, ICRS, and IF3E at an Rsce from 33 to 750 96 Fig. 5.25 Actual value of capacitor voltage UCRS as a function of Rsce 97 Fig. 5.26 The selected value combinations for LNF3E and LNETZ 98 Fig. 5.27 The Rsce as a function of the quotient of LNETZ over LNF3E 99 Fig. 5.28 Shape of the line currents at an Rsce=96 100 Fig. 5.29 Shape of the F3E currents at an Rsce=96 101 Fig. 5.30 Filter current ICRS and filter voltage UCRS at an Rsce=96 102 Fig. 5.31 Intermediate current IRM1 feeding the PWR and intermediate voltage at an Rsce=96 102 Fig. 5.32 Output current IMOT and output voltage UUV at an Rsce=96 103 Fig. 5.33 The F3E currents at an Rsce=1164 103 Fig. 5.34 Shape of filter voltage UCRS and current ICRS at an Rsce=1164 104 Fig. 5.35 Intermediate PWR current IRM1 and intermediate voltage UCZK at an Rsce=1164 105 Fig. 5.36 Output current IMOT and voltage UUV at an Rsce=96 105 xi Fig. 5.37 Higher harmonics spectra of ILNF, IF3E, and ICRS at an Rsce=96 106 Fig. 5.38 Higher harmonics spectra of the three F3E currents ILNF, IF3E, and ICRS at an Rsce=1164 106 Fig. 5.39 Higher harmonics spectra of the F3E currents ILNF, IF3E, and ICRS at an Rsce=96 107 Fig. 5.40 Higher harmonics spectra of the F3E currents ILNF, IF3E, and ICRS at an Rsce=1164 107 Fig. 5.41 Higher harmonics spectra of ILNF at Rsce=96 and Rsce=1164 108 Fig. 5.42 Effective value of the filter current ICRS as a function of Rsce 109 Fig. 5.43 Filter voltage UCRS as a function of Rsce 109 List of tables Table 2.1 List of possible semiconductors states 7 Table 2.2 The allowed logical states 8 Table 5.1 Value pairings 100 xii