hysteresis current control

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Presentation Transcript

Slide 1: 

Single-Phase Diode Rectifier Bridge Large capacitor at the dc output for filtering and energy storage

Slide 2: 

Diode-Rectifier Bridge Analysis Two simple (idealized) cases to begin with

Slide 3: 

Waveforms with a purely resistive load and a purely dc current at the output In both cases, the dc-side voltage waveform is the same

Slide 4: 

Diode-Rectifier Bridge Input Current Idealized case with a purely dc output current

Slide 5: 

Diode-Rectifier Bridge Analysis with AC-Side Inductance Output current is assumed to be purely dc

Slide 6: 

Effect of DC-Side Current on THD, PF and DPF Very high THD at low current values

Slide 7: 

Diode-Rectifier with a Capacitor Filter Power electronics load is represented by an equivalent load resistance

Slide 8: 

Diode-Bridge Rectifier: Waveforms Analysis using PSpice

Slide 9: 

Analysis using PSpice Input Line-Current Distortion

Slide 10: 

Line-Voltage Distortion PCC is the point of common coupling

Slide 11: 

Distortion in voltage supplied to other loads Line-Voltage Distortion

Slide 12: 

Three-Phase, Full-Bridge Rectifier Commonly used

Slide 13: 

Three-Phase, Full-Bridge Rectifier: Redrawn Two groups with three diodes each

Slide 14: 

Three-Phase, Full-Bridge Rectifier Waveforms Output current is assumed to be dc

Slide 15: 

Three-Phase, Full-Bridge Rectifier: Input Line-Current Assuming output current to be purely dc and zero ac-side inductance

Slide 16: 

Three-Phase, Full-Bridge Rectifier Including the ac-side inductance

Slide 17: 

Rectifier with a Large Filter Capacitor Output voltage is assumed to be purely dc

Slide 18: 

Three-Phase, Full-Bridge Rectifier THD, PF and DPF as functions of load current

Slide 19: 

Harmonic Guidelines: IEEE 519 commonly used for specifying limits on the input current distortion

Slide 20: 

B. Hysteresis (Bang-bang) PWM (1) Three-phase inverter for hysteresis Current Control Fig. 8 Three-phase inverter for hysteresis current control. 15

Slide 21: 

II. PWM METHODS B. Hysteresis (Bang-bang) PWM (2) Hysteresis Current Controller Fig. 9 Hysteresis current controller at Phase “a”. 16

Slide 22: 

II. PWM METHODS B. Hysteresis (Bang-bang) PWM (3) Characteristics of hysteresis Current Control Advantages Drawbacks 17 Excellent dynamic response Low cost and easy implementation Large current ripple in steady-state Variation of switching frequency No intercommunication between each hysterisis controller of three phases and hence no strategy to generate zero-voltage vectors. As a result, the switching frequency increases at lower modulation index and the signal will leave the hysteresis band whenever the zero vector is turned on. The modulation process generates subharmonic components