Power Factor Correction Input Circuit Kevin Wong, Paul Glaze, Ethan Hotchkiss, Jethro Baliao Advisor: Prof. Ali Bazzi 10/27/2016 JETHRO Introduce Ourselves Copyright © 2016 – Advanced Power Electronics & Electric Drives Lab (APEDL)

Outline JETHRO Go over what the course of the presentation will be Background Power Factor (PF) Power Factor Correction (PFC) Problem Statement Importance for Lenze Specifications Constraints Approach Active vs passive rectification DC/DC Design Topologies Boost Buck-Boost Sepic Flyback Design simulations Timeline moving forward JETHRO Go over what the course of the presentation will be Copyright © 2016 – Advanced Power Electronics & Electric Drives Lab (APEDL)

Power Factor(PF)=cos=(P/S) What is Power Factor? The ratio of real power to apparent power in the circuit Power Factor(PF)=cos=(P/S) Another way of looking at this relationship is from the power triangle. The apparent power, S can be determined by taking the vector sum of the reactive power, Q and the real power. S = √(P2 * Q2) JETHRO Working Power(Actual Power, Active Power, or Real Power) is what powers equipment Reactive Power is Power that transformers and motors to produce magnetic flux Apparent power is the vectorial summation of Reactive Power and Working Power Beer Analogy 2000W @120V is 16.7A at Unity Power Factor but 2000W @23.8A at a 0.7 Power Factor This would not trip a breaker at Unity Power Factor but at a 0.7 Power Factor it would. Copyright © 2016 – Advanced Power Electronics & Electric Drives Lab (APEDL)

What is Power Factor Correction? Reducing the reactive power consumed by an inductive load improves power factor Power factor correction methods: Capacitor Banks Pros: Simple, inexpensive, quiet Cons: Large size, limited adjustment Synchronous Condenser Pros: Extensive adjustment Cons: Large size, noise, expensive Power Electronics Switching Converter Pros: Extensive adjustment, small size, quiet Cons: Expensive JETHRO Simply Put, Reducing the Foam improves the amount of Beer you get Examples of improving PF is the following Capacitor Banks store electrical energy and corrects power supply error in electric motors and transformers Synchronous Condenser would absorb reactive power Power Electronics are small, generate no noise

Why is this important for Lenze? Looking for a circuit to improve the Power Factor in one of their drives due to more consumer market requests. PFC creates less distortion on the line for the customer Design and manufacture affordable Variable Frequency Drives(VFDs). VFDs control the frequencies and voltages to motors. This is important because: Reduction in Energy Consumption and Costs Increase Longevity and Reduce Maintenance on Equipment Efficiency saves on power component and thermal management, and therefore Size and Cost JETHRO Lenze manufactures VFDs in Uxbridge MA Appliances include Heating, Ventilation and Air Conditioning (HVAC), Drills, and Pumps. Importance of VFD’s Reduction in Energy Consumption If an application does not have to function at full load, a VFD can cut down on the extra costs by controlling the motor. The VFD will match the load and the input to maximize efficiency. Electric Motor systems account for more than 60% of the power consumption in industry. Having one can potentially reduce energy consumption by 70% depending on the application Longevity and Maintenance The VFD will have the motor operate at its optimal speed preventing any overloads, under voltage, over voltage, etc.

Block Diagram KEVIN NEXT JETHRO Simple Block Diagram showing how we plan on approaching this project First the AC input runs through a Diode Bridge Rectifier That DC output will run into our choice of topology: Buck That output will feedback into the Switch/MOSFET using either: PID Controller Analog Controller Microcontroller KEVIN NEXT

Specifications Input Requirements Output Requirements Voltage Input: 90Vac-132Vac Power Factor: >0.95 Frequency: 48-62Hz Inrush Current: <40A Output Requirements Voltage Output: 325Vdc Max Continuous Power: 1472 Voltage Ripple: 20Vpk-pk System Requirements Operating Temperature: -10 to 55 °C Switching Frequency: >20KHz Kevin

Constraints Lenze is looking for PAUL NEXT Low Cost Small Footprint High Efficiency PCB Design Possible Three-Phase Circuit 230Vac to 325Vdc KEVIN Something Cheap, they plan on mass producing this product Small Footprint is a plus, this will be going to be working with one of their VFDs High Efficiency is Key to saving money and energy PCB design would be great for Lenze, although a hardwired project would also be helpful too before working with the final design Three-Phase is one of the extra goals for this project Three-Phase is advantageous over Single-Phase because Due to the Instantaneous Power (power consumed and power generated at anytime during a cycle) Consistent Power Delivery and more efficient PAUL NEXT

Active vs Passive Rectification Pros: Lower voltage drop Bi-directional current Higher efficiency Cons: Requires control More expensive More complex Passive: Pros: No external control Simple Inexpensive Cons: Uni-directional current Higher voltage drop Lower efficiency PAUL

Possible DC/DC Topologies Boost Flyback SEPIC Buck Boost PAUL ETHAN NEXT Copyright © 2016 – Advanced Power Electronics & Electric Drives Lab (APEDL)

Boost Converter Diagram ETHAN

Ideal Boost Waveforms Output Voltage ETHAN Power ~1325-1525W Input Current ~0-50A Power Factor >0.9999 ETHAN All visible ripples are at fundamental frequency(60Hz) Not at the PWM switching frequency (>20kHz) Very high power factor due to ideal components and control circuit Output Voltage Copyright © 2016 – Advanced Power Electronics & Electric Drives Lab (APEDL)

Boost Pros Pros: Small Footprint Simple Design PF well over 0.99 Inexpensive No transformer required Operates at large range of power ETHAN Requires only 4 components at most basic level With control circuit, capable of very high PF Due to simplicity, boost converter is relatively inexpensive Does not require a transformer(saves on weight and space) Large range of Power applications

Boost Cons Cons: Difficult to stabilize High voltage ripple High current inrush Requires a large inductor ETHAN Difficult to stabilize due to RHP zero High Vo ripple and IL ripple in the case of PFC because of input dropping to 0V Requires a large inductor to control inrush current JETHRO NEXT

Flyback Converter Diagram JETHRO The Flyback Converter is a derivative of the buck-boost converter The centerpiece is known as a “Flyback Transformer” Current does not flow simultaneously in both windings So when the switch closes current will flow through the primary winding (Left side). This will induce a voltage over the secondary winding. On the right side of the circuit the diode is reversed biased so there will be no secondary current. There is a snubber circuit to suppress voltage spikes caused by the switch

Ideal Flyback Waveforms Input Current: 0A~59A Output Power: 900W~1180W Output Voltage: 290V~340V JETHRO These are the Ideal Flyback Waveforms Using Simulink to simulate Used a 1ohm resistor to limit the inrush current that was around 500A without it. If the lower ohm resistor is used the output voltage would be significantly greater than the required specifications. A greater ohm resistor will result in a lower output voltage compared to the required specifications The inrush current is also 3 times greater than the specified amount which is >40A Output Power is less than the requested which is 1472W continuous instead of 1180W The Voltage Ripple for the Output Voltage is around 40Vpk-pk which is twice the amount needed The Power Factor was hovering around 0.998 Power Factor: 0.998

Flyback Pros Pros No need for an additional inductor Offers Single or Multiple Isolated Output Voltages Great for High Voltages (at Low Power) Simple Design Low Cost Similar Advantages from a Buck-Boost Converter JETHRO No additional inductor is needed because of the Flyback Transformer Due to the Flyback Transformer the Flyback Topology can have the output voltages adjusted by varying the turns ratio in the Transformer Great for low-power applications (But we are working something over 1000 watts) Similar advantages to the Buck-Boost which will be explained later Copyright © 2016 – Advanced Power Electronics & Electric Drives Lab (APEDL)

Flyback Cons Cons Due to the use of a Transformer the Converter is not suitable for high power applications Feedback Loop requires a lower bandwidth due to a Right hand plane (RHP) zero in response of the converter High-Value Output Capacitor In CCM, the control loop needs slope compensation when the duty cycle is above 50%. High Current Stress of the Switch and Output Diode can cause EMI problems JETHRO Not suitable for High power yet is good for high voltages outputs Not only does the Boost have RHP (imaginary pole) problems but so does the Flyback making this Topology Difficult to stabilize Requires a Separate snubber design(which was shown in the Diagram before High-Value Output Capacitor will increase the size of the topology Boost and Flyback don't require high side drivers Flyback also capable of true shutdown Components and layout are also important to efficiency KEVIN NEXT Copyright © 2016 – Advanced Power Electronics & Electric Drives Lab (APEDL) 10/20/16

SEPIC Converter Diagram KEVIN Mosfet switched to 1, closed; Input voltage increases current in inductor 1 and loops back down. C1 discharges, increasing the current in Inductor 2. When Switch is 0 or open, then both inductors produce current through load and capacitors are charged.

Ideal SEPIC Waveforms Output Voltage: 322V-329V Input Current: 0-150A KEVIN Open Loop Results. The Output Voltage is within the requirements but the input current is much greater than what it should be. Output voltage is 322-329V and the Input Current after the inrush current is 0 to 150A. Input Current: 0-150A

SEPIC Pros Pros Can increase or decrease input voltage values Output same polarity High Power Efficiency Inductor is on input side, limiting slope of current KEVIN Copyright © 2016 – Advanced Power Electronics & Electric Drives Lab (APEDL) 10/20/16

SEPIC Cons Cons Transfers all its energy via series capacitor, capacitor requires high capacitance and current handling capability Voltage Drop on Diode is critical to reliability and efficiency (switching time needs to be fast to not generate high voltage spikes across inductors) Schottky diodes solution Larger number of components as well as high complexity KEVIN PAUL NEXT Copyright © 2016 – Advanced Power Electronics & Electric Drives Lab (APEDL) 10/20/16

Buck-Boost Converter Diagram PAUL

Ideal Buck-Boost Waveforms Open Loop Output Voltage ~-315-335V Power ~1325-1525W Input Current ~0-50A Power Factor ~0.93 PAUL Output Voltage Copyright © 2016 – Advanced Power Electronics & Electric Drives Lab (APEDL)

Buck-Boost Pros Pros: Large frequency range No transformer No inrush current or precharge like the boost More stable output voltage PAUL

Buck-Boost Cons Cons: High transients Voltage stress on the FET (switch) Less efficient than flyback or boost Calculations for control are more difficult Boost and buck-boost only have one possible voltage Difficult to stabilize Power is inverted No Common Ground Adaptations: EMI filter (may cost more in efficiency) High quality FET Additional supply for controls PAUL Inductor current = Iin+iout Inverted output no common ground

Buck-Boost There is a high quality pdf of this uploaded in the simulation file. This simulation is now working but I was able to get some data from before the simulation had an error. The chip is LT8312 Boost power correction factor controller. It had to be almost tricked to work. That is why there are so many passive components. The LT4320 was used to control the mosfets for rectification. PAUL ETHAN NEXT

DC/DC Converter Pros & Cons ETHAN

Which methods fit our needs? DC/DC Converter Topology We presented the pros and cons of each topology along with preliminary simulations to Lenze on Monday and they have decided that they want us to move forward with the boost converter. Active vs. Passive Rectification Lenze has also stated that they would like us to start with passive rectification in order to simplify the design. ETHAN

What is next? Small signal modeling of the boost converter Optimize closed-loop control simulation Size components Convert ideal simulation in Simulink to non-ideal simulation in both Simulink and LT Spice? Explore control options(programmable microcontroller vs. modifying a pre-made IC chip) Begin physical prototyping Begin PCB design ETHAN JETHRO NEXT

Fall Timeline JETHRO Sepic and Buck Boost are probably the bulkiest options Flyback has limited power Boost is probably the best option Look at power levels Lenze looks for Low cost and simple option Mosfet Based bridge input instead of Diode could give more control Copyright © 2016 – Advanced Power Electronics & Electric Drives Lab (APEDL) 10/20/16

Spring Timeline JETHRO How out next semester looks Mostly Testing and Delivering Weekly reports (assuming we get the prototype functional by the end of this semester) This is still subject to change however

Resources J. Betten. (2011, Q2) “Benefits of a coupled-inductor SEPIC converter” Analog Applications Journal [Online] Available: http://www.ti.com/lit/an/slyt411/slyt411.pdf [October 14 2016]. G. Sharp. “Sepic Converter Design and Operation.” BS, WPI, Worcester, MA, 2014. ST. “TM sepic converter in PFC pre-regulator.” Internet: http://www.st.com/content/ccc/resource/technical/document/application_note/48/9d/ 34/73/b9/27/48/65/CD00134778.pdf/files/CD00134778.pdf/jcr:content/translations/en.C D00134778.pdf, March 2007[October 10, 2016]. J.W. Kolar and T. Friedli. “The Essence of Three-Phase PFC Rectifier Systems-Part I.” IEEE Transactions on Power Electronics, Vol. 28, No.1,pp176-198, [ September 20, 2016]. H. Wei, and I. Batarseh. (1998) “Comparison of Basic Converter Topologies For Power Factor Correction.” [September 20, 2016] "The Flyback Converter," in University of Colorado. [Online]. Available: http://ecee.colorado.edu/~ecen4517/materials/flyback.pdf. [Oct. 27, 2016]. De Nardo et al, “Power Stage Design of Fourth-Order DC-DC Converters by Means of Principal Components Analysis.”IEEE Transactions on power Electronics, Vol. 23 No. 6,pp2867-2877 Consistent w/ citations Include Problem Statement What is PFC? Why is this important for Lenze? Include Block Diagram Constraints Design Options Literature Build a pros/cons table Gantt Chart Copyright © 2016 – Advanced Power Electronics & Electric Drives Lab (APEDL)

Semiconductor Options IGBT Voltage Rating: >1kv Current Rating: >500A Slower switching More expensive MOSFET Voltage Rating: <1kV Current Rating: <200A Faster switching Less expensive

Frequency Domain Analysis: Buck-Boost Current vs Voltage 100k Ohm Load PAUL FFT of current with no load at 100kHz

Frequency Domain Analysis: Buck-Boost Current vs Voltage 100 ohm 100 ohm load FFT of current PAUL

Frequency Domain Analysis: Buck-Boost In the 100 ohm FFT there was an 80 db harmonic and a 60db. Not terrible but an emi filter would help the true power correction a lot. With the loaded voltage vs current source we see the big advantage of Buck Boost, a steady rise in current. The inrush current was inherently limited by the boost controller’s soft start and orientation of the FET. The power factor here is about 1. The distortion power factor is very bad. A proper filter will round off the square wave PAUL Because of the error I did not get a good efficiency calculation. If you look at the scale of the input current it is in KAmp. The efficiency should be very high but it must be less than the boost as it has fewer and smaller components.

Questions?