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Hybrid Electric Vehicle Active Rectifier Performance Analysis Ean A. Amon Oregon State University Material Covered Hybrid Electric Vehicle Design Fault Tolerance Passive Rectification Active Rectification Voltage-Controlled Active Rectifier Investigations Current-Controlled Active Rectifier Investigations Hardware Implementation Hybrid Electric Vehicle Design High Efficiency – extended operating range Reduced EMI – causes interference in communications and control systems Fault Tolerance – limp home capability Fault Tolerance of Permanent Magnet Machine Systems Multi-Phase Designs Independent Phase Configurations • separate H-bridge rectifiers • isolation of both electrical and magnetic circuits Intelligent Control • isolate damaged windings • maintain output in post-fault state Passive Rectifier Investigations Baseline Comparison of Active Rectifier Results Verification of Equivalent Circuit PM Machine Models System Parameters: - 600V dc bus - 440kW resistive load - 2400µF bus capacitance Generator Parameters: - 1.2 kHz electrical frequency - 98% efficient - 5% full-load voltage drop Generator Configurations: - 3-phase wye-connected - 6-phase wye-connected - 6-phase independent windings Passive Rectifier with PM Synchronous Machine Model PM Synchronous Machine model in Matlab Simulink utilized • 3-phase configurable machine • torque driven model, mechanical frequency feedback • no-load peak phase voltage = 368.5V (to achieve 600V dc) • phase resistance = 8.0mΩ (calculated for 98% efficiency) • phase inductance = 2.7µH (calculated for 5% voltage drop under full load) Note: Simulations were also carried out using 10% of the calculated inductance (0.27µH) due to significant generator voltage distortion at high frequency. Passive Rectifier with PM Synchronous Machine Model (continued) 3-phase (6-pulse) diode rectifier connected to PMSM model 2400µF dc bus capacitance 440kW resistive load (0.818Ω at 600V dc) Matlab Simulink Schematic: Passive Rectifier with PM Synchronous Machine Model (continued) dc bus voltage with calculated inductance (2.7µH) approx. 4.4V ripple Passive Rectifier with PM Synchronous Machine Model (continued) dc bus voltage waveforms with reduced inductance (0.27µH) approx. 16.4V ripple Passive Rectifier with PM Synchronous Machine Model (continued) Harmonic Analysis of DC Bus Voltage 2.2V 8.2V calculated inductance (2.7µH) reduced inductance (0.27µH) (THD = 0.72%) (THD = 1.37%) Note: Results with full calculated inductance are shown for all further passive rectifier simulations. Passive Rectifier with Equivalent Circuit Generator Model PMSM model removed equivalent circuit: 3 ac sources, 120° spacing, peak phase voltage = 368.5V phase resistance = 8.0mΩ phase inductance = 2.7µH Matlab Simulink Schematic: Verification of Equivalent Circuit Model equivalent circuit model PMSM model Passive Rectifier with 6-Phase Wye-Connected Generator 6 ac sources, 60° spacing, peak phase voltage = 350V phase resistance and inductance recalculated • phase resistance = 12mΩ • phase inductance = 4.1µH Matlab Simulink Schematic: Passive Rectifier with 6-Phase Wye-Connected Generator (continued) dc bus voltage waveforms and FFT dc bus ripple = 3.6V THD = 0.59% voltage ripple and THD slightly reduced from 3-phase case Passive Rectifier with 6-Phase Independent Generator 6 ac sources, 60° spacing, peak phase voltage = 698.7V phase resistance and inductance recalculated • phase resistance = 49mΩ • phase inductance = 16µH Matlab Simulink Schematic: Passive Rectifier with 6-Phase Independent Generator (continued) dc bus voltage waveforms and FFT dc ripple = 3.7V THD = 0.60% dc bus ripple and THD nearly unchanged from wye-connected case with increased phase voltage and phase impedance Active Rectifier Investigations with Voltage Control active rectifiers simulated in three configurations • 3-phase wye, 6-phase wye, and 6-phase independent simple voltage control – sinusoidal modulation referencing dc bus voltage error • product of per-unit sinusoidal input voltage and calculated modulation index “Universal Bridge” block configured as IGBT “boost” rectifier • single 3-phase, dual 3-phase, and H-bridge configurations RC snubber circuits utilized on all IGBT/diode pairs • necessary for simulation convergence • resistance = 50Ω, capacitance = 250nF switching frequencies of 10 kHz, 15 kHz, and 20 kHz with dead times of 2µs and 5µs Simple Voltage Control (Mavg)Vdc m G (Vdc Vref ) Vref (control scheme for 3-phase active rectifier) 3-Phase Wye-Connected Active Rectifier with Voltage Control peak phase voltage lowered to 285.8V (350VLL rms) phase resistance and inductance unchanged from 3-phase passive rectifier • 8.0mΩ and 2.7µH respectively Matlab Simulink Schematic: 3-Phase Wye-Connected Active Rectifier with Voltage Control (continued) dc ripple = 26V dc ripple = 30V fs = 10 kHz, 2µs dead time fs = 10 kHz, 5µs dead time 3-Phase Wye-Connected Active Rectifier with Voltage Control (continued) dc ripple = 10.5V dc ripple = 10V fs = 15 kHz, 2µs dead time fs = 15 kHz, 5µs dead time 3-Phase Wye-Connected Active Rectifier with Voltage Control (continued) dc ripple = 10V dc ripple = 8V fs = 20 kHz, 2µs dead time fs = 20 kHz, 5µs dead time 3-Phase Wye-Connected Active Rectifier with Voltage Control (continued) 15 kHz, 2µs dead time results: dominant switching harmonic, approx. 2.6V at sideband of fs THD = 0.44% fs = 15 kHz, 2µs dead time 15 kHz, 5µs dead time results: dominant switching harmonic, approx. 2.1V at sideband of fs THD = 0.48% fs = 15 kHz, 5µs dead time 6-Phase Wye-Connected Active Rectifier with Voltage Control Matlab Simulink Schematic: peak phase voltage is 285.8V utilizes two 3-phase boost rectifiers in parallel control scheme incorporates sine-triangle comparators for 3 additional phases phase resistance and inductance unchanged from 6-phase passive rectifier • 12.0mΩ and 4.1µH respectively 6-Phase Wye-Connected Active Rectifier with Voltage Control (continued) fs = 15 kHz, 5µs dead time dc ripple approx. 4.7V THD = 0.44% dominant switching harmonic, approx. 1.1V at 2fs 6-Phase Independent Active Rectifier with Voltage Control Matlab Simulink Schematic: peak phase voltage is 495V (350V rms) phase resistance and inductance unchanged from 6-phase passive rectifier model • 49.0mΩ and 16.0µH respectively single H-bridge rectifier for each phase 6-Phase Independent Active Rectifier with Voltage Control (continued) same control scheme algorithm additional sine-triangle comparators for offset gating of conducting switch pairs • two conducting devices do not switch in same instance • reduces switching harmonics 6-Phase Independent Active Rectifier with Voltage Control (continued) fs = 15 kHz, 5µs dead time dc ripple approx. 4.4V THD = 0.60% dominant switching harmonic, approx. 1.7V at 2fs Current Control of Active Rectifiers current control – compares actual input currents with reference currents, forces current to follow a sinusoidal waveform Operation: 1. reference currents (Iref) calculated using dc I ref Vdc Vdc ,ref G Vs , pu bus voltage error I mod I s , pu I ref 2. subtracting reference currents from per unit Vdc source currents produces modulation signal (Imod) Vdc,ref 3. modulation signal is then used in sine-triangle comparison Updated Simulation Specifications New generator specifications provided by BAE Systems • 6 phase windings configured as two synchronized 3-phase sets • neutral access for independent phase capability • back EMF of 380VLL rms (peak phase voltage 310.3V, 219.4V rms) • phase inductace = 60µH • phase resistance = 48mΩ • electrical frequency = 708 Hz (10 pole pairs @ 4250 rpm) switching frequency of 15 kHz, dead time of 5µs 400 kW resistive load, 2400µF dc bus capacitance snubber impedance increased • resistance = 100Ω, capacitance = 176.84nF Current-Controlled 2x3-Phase Wye Configuration Matlab Simulink Schematic Schematic of IGBT Bridge Current-Controlled 2x3-Phase Wye Configuration (continued) Schematic of PWM Generator (current-control scheme) current-control waveforms (phase A) modulation & gating signals (phase A) Current-Controlled 2x3-Phase Wye Configuration (continued) device currents (phase A rectifier leg) source voltage and current waveforms Current-Controlled 2x3-Phase Wye Configuration (continued) low dc voltage ripple, approximately 4.5V only positive currents between rectifier and capacitance Harmonic Analysis of Current-Controlled 2x3-Phase Wye Configuration Input Current FFT 12 10 Input Current FFT Results: Harmonic Magnitude (A) 8 dominant switching harmonics • approx. 11.5A and 9.5A at sidebands of fs 6 4 • approx. 6.5A and 6A at sidebands of 2fs 2 0 dominant 5th harmonic, approx. 8.2A 0 10 20 30 40 50 60 70 80 90 100 Frequency (kHz) DC-Bus Voltage FFT 1 0.9 0.8 DC Bus Voltage FFT Results: 0.7 Harmonic Magnitude (V) 0.6 0.5 dominant switching harmonics 0.4 • approx. 0.65V and 0.5V at sidebands of fs 0.3 0.2 • approx. 0.85V at 2fs 0.1 0 0 10 20 30 40 50 60 70 80 90 100 Frequency (kHz) Current-Controlled 6-Phase Independent Configuration Matlab Simulink Schematic Schematic of IGBT H-Bridge Current-Controlled 6-Phase Independent Configuration (continued) Schematic of PWM Generator (current-control scheme) current-control waveforms (phase A) Current-Controlled 6-Phase Independent Configuration (continued) Schematic of IGBT H-Bridge modulation & gating signals (phase A) Current-Controlled 6-Phase Independent Configuration (continued) device currents (phase A H-bridge) source voltage and current waveforms Current-Controlled 6-Phase Independent Configuration (continued) dc bus voltage lowered by 3 increased dc voltage ripple, approximately 6.2V only positive currents between rectifier and capacitance Harmonic Analysis of Current-Controlled 6-Phase Independent Configuration Input Current FFT 25 Input Current FFT Results: 20 3rd harmonic, approx. 22A Harmonic Magnitude (A) 15 5th harmonic, approx. 10A 10 5 dominant switching harmonics, 0 approximately 8.5A at sidebands of 2fs 0 10 20 30 40 50 60 70 80 90 100 Frequency (kHz) DC Bus Voltage FFT 2 1.8 1.6 DC Bus Voltage FFT Results: 1.4 Harmonic Magnitude (V) 1.2 1 dominant switching harmonic, 0.8 approximately 1.9V at 2fs 0.6 0.4 0.2 0 0 10 20 30 40 50 60 70 80 90 100 Frequency (kHz) Effects of Offset Gating Input Current FFT Input Current FFT 50 25 45 40 20 35 Harmonic Magnitude (A) Harmonic Magnitude (A) 30 15 25 20 10 15 10 5 5 0 0 0 10 20 30 40 50 60 70 80 90 100 0 10 20 30 40 50 60 70 80 90 100 Frequency (kHz) Frequency (kHz) DC Bus Voltage FFT DC Bus Voltage FFT 2 2 1.8 1.8 1.6 1.6 1.4 1.4 Harmonic Magnitude (V) Harmonic Magnitude (V) 1.2 1.2 1 1 0.8 0.8 0.6 0.6 0.4 0.4 0.2 0.2 0 0 0 10 20 30 40 50 60 70 80 90 100 0 10 20 30 40 50 60 70 80 90 100 Frequency (kHz) Frequency (kHz) non-offset gating offset gating Hardware Implementation Powerex Module Planned hardware testing configurations: (two rectifier legs) • 2x3-phase wye • 3-phase independent Ia Ib x4 3-Phase Powerex Module Transformer (two rectifier legs) Hardware representation: 3-Phase Ic • 120 kVA Generator = 120 kVA programmable source Programmable Id • two 3-phase transformers for Source x4 3-Phase 2x3-phase wye configuration Transformer Powerex Module (two rectifier legs) • Rectifier = Powerex configurable IGBT (Representing 2x3-Phase Wye Generator) Ie If H-bridge assemblies (4 available) • 3300µF capacitance by default Gating Signals Opal-RT HILbox x4 Rapid Prototyper x4 x4 (Rectifier Controller) x4 • Control = Opal-RT HIL Rapid Prototyping System Idc Powerex Module (used as capacitor bank) + • Load = 20kW fan-cooled resistive bank 20 kW Resisitive Load Vdc 3300µF - Hardware Implementation (continued) Powerex H-bridge Assembly 120 kVA Programmable Source Rectifier Bridge Opal-RT HIL Rapid Prototyper Test Setup Experimental Results switching frequency = 10kHz, dead time = 5µs simple voltage control used in initial testing desired full load testing • 20kW load at 600V dc • phase voltage = 219.4V rms (380VLL rms) at 708Hz 2x3-phase wye testing abandoned due to diode failures on two bridges • BAE Systems desired operation without snubber circuits • caused by voltage spikes due to di/dt at IGBT turn off continued with 3-phase wye testing • transformers and damaged bridges removed • dead time increased to 10µs voltage and frequency slowly ramped up • highest level achieved = phase voltage 140V rms at 550 Hz Experimental Results (continued) Phase A Voltage & Gating Signals Input Current Waveforms proper gating signals produced by the sinusoidal currents drawn control-scheme high reactive power voltage waveform shows PWM effects • no phase correction in simple due to source impedance voltage control Experimental Results (continued) DC Bus Voltage and Current Waveforms Ch. 1 – dc bus voltage (313.4V) Ch. 2 – rectifier output current (before capacitance) Ch. 3 – dc load current (18.6A) (after capacitance) 5.85 kW dissipated Conclusions excellent dc bus voltage regulation in all active rectifier simulations • less than 6.5V ripple with current-control current control operation produced excellent input current waveforms • sinusoidal currents with low THD H-Bridge configurations benefit from offset gating • eliminated harmonics at odd multiples of fs • little influence on other harmonic magnitudes hardware testing results show promise of high performance • modulation produces sinusoidal current waveforms • further improvement with current control • snubber circuits needed for further testing Questions?

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posted: | 9/2/2011 |

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