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ECEN 613 Rectifier & Inverter Circuits Module-7c Professor: Dr. P. Enjeti with Michael T. Daniel Rm. 024, WEB Email: [email protected] [email protected] Textbook: Power Electronics – Converters, Applications & Design (Third edition), by: Ned Mohan et al., John Wiley COURSE WEBPAGE: http://eCampus.tamu.edu ECEN 613 Rectifiers & Inverters Dr. Prasad Enjeti, Department of Electrical & Computer Engineering, Texas A&M University http://www.ece.tamu.edu/People/bios/benjetip.html 1 Chapter 18 Utility Interface ECEN 613 Rectifiers & Inverters Dr. Prasad Enjeti, Department of Electrical & Computer Engineering, Texas A&M University http://enjeti.tamu.edu 2 PWM Rectifiers: 1-Phase Voltage Source – Example The PWM rectifier shown in the top figure is employed for managing power flow between an electric vehicle and the grid. The equivalent circuit is shown in the bottom figure. The converter can draw power (Watts) from the grid to charge the a vehicle or draw power from the vehicle and feed it to the grid. It can also supply + reactive power (VARs) to the grid. Vs The input voltage VS can be either 120 Vrms or 220 Vrms, at 60Hz. When Vs = 120 Vrms the charging / discharging rate is 100W ≤ P ≤ 1 kW. When Vs = 220 Vrms the charging / discharging rate is 100W ≤ P ≤ 3 kW. When the vehicle is charging or discharging it is required to maintain unity PF. Xs is 0.1 p.u. given Vbase = √2*220 Vrms and Pbase = 3 kW. Xs - + VAO - + A Vdc - O Xs Vs 0o VAO,1 δo (a) When Vs = 120 Vrms, find the minimum Vdc to exchange 1 kW with the grid. Assume m = 1. (b) When Vs = 120 Vrms, find δ to charge the vehicle at 1 kW. (c) When Vs = 120 Vrms, find δ to supply 500 W to the grid from the vehicle. (d) When Vs = 220 Vrms, find the minimum Vdc to exchange 3 kW with the grid. Assume m = 1. ECEN 613 Rectifiers & Inverters Dr. Prasad Enjeti, Department of Electrical & Computer Engineering, Texas A&M University http://enjeti.tamu.edu 3 PWM Rectifiers: 1-Phase Voltage Source – Example a Xs + + Vs - + A Vdc VAO - O - Xs Vs 0o ECEN 613 Rectifiers & Inverters Dr. Prasad Enjeti, Department of Electrical & Computer Engineering, Texas A&M University http://enjeti.tamu.edu VAO,1 δo 4 PWM Rectifiers: 1-Phase Voltage Source – Example a Xs + + Vs - + A Vdc VAO - O - Xs Vs 0o ECEN 613 Rectifiers & Inverters Dr. Prasad Enjeti, Department of Electrical & Computer Engineering, Texas A&M University http://enjeti.tamu.edu VAO,1 δo 5 PWM Rectifiers: 1-Phase Voltage Source – Example a Xs + + Vs - + A Vdc VAO - O - Xs Vs 0o ECEN 613 Rectifiers & Inverters Dr. Prasad Enjeti, Department of Electrical & Computer Engineering, Texas A&M University http://enjeti.tamu.edu VAO,1 δo 6 PWM Rectifiers: 1-Phase Voltage Source – Example a Xs + + Vs - + A Vdc VAO - O - Xs Vs 0o ECEN 613 Rectifiers & Inverters Dr. Prasad Enjeti, Department of Electrical & Computer Engineering, Texas A&M University http://enjeti.tamu.edu VAO,1 δo 7 PWM Rectifiers: 1-Phase Voltage Source – Example a Xs + + Vs - + A Vdc VAO - O - Xs Vs 0o ECEN 613 Rectifiers & Inverters Dr. Prasad Enjeti, Department of Electrical & Computer Engineering, Texas A&M University http://enjeti.tamu.edu VAO,1 δo 8 PWM Rectifiers: 1-Phase Voltage Source – Example a Xs + + Vs - + A Vdc VAO - O - Xs Vs 0o ECEN 613 Rectifiers & Inverters Dr. Prasad Enjeti, Department of Electrical & Computer Engineering, Texas A&M University http://enjeti.tamu.edu VAO,1 δo 9 PWM Rectifiers: 1-Phase Voltage Source – Example a Xs + + Vs - + A Vdc VAO - O - Xs Vs 0o ECEN 613 Rectifiers & Inverters Dr. Prasad Enjeti, Department of Electrical & Computer Engineering, Texas A&M University http://enjeti.tamu.edu VAO,1 δo 10 PWM Rectifiers: 1-Phase Voltage Source – Example (e) During the night when the vehicle does not need to charge and the grid does not require additional real power, it is desired that the converter supply reactive power to the grid. Assume the DC voltage is increased to 600 Vdc. If Vs = 120 Vrms with this Vdc, what is the maximum amount of capacitive reactive power that the converter can supply to the grid? a Xs + + Vs - (g) What value would we need to select for each parameter to supply only ¼ of the reactive power found in part (e)? O - Xs Vs 0o Rectifiers & Inverters Vdc VAO - (f) If we need to supply less reactive power than the maximum found in part (e) what are two parameters that we could use to reduce the amount of reactive power supplied ECEN 613 + A Dr. Prasad Enjeti, Department of Electrical & Computer Engineering, Texas A&M University http://enjeti.tamu.edu VAO,1 δo 11 a Xs + Vs - ECEN 613 Rectifiers & Inverters Dr. Prasad Enjeti, Department of Electrical & Computer Engineering, Texas A&M University http://enjeti.tamu.edu + VAO - + A Vdc O - 12 PWM Rectifiers: 1-Phase Voltage Source – Example a Xs + + Vs - + A Vdc VAO - O - Xs Vs 0o ECEN 613 Rectifiers & Inverters Dr. Prasad Enjeti, Department of Electrical & Computer Engineering, Texas A&M University http://enjeti.tamu.edu VAO,1 δo 13 PWM Rectifiers: 1-Phase Voltage Source – Example a Xs + + Vs - + A Vdc VAO - O - Xs Vs 0o ECEN 613 Rectifiers & Inverters Dr. Prasad Enjeti, Department of Electrical & Computer Engineering, Texas A&M University http://enjeti.tamu.edu VAO,1 δo 14 PWM Rectifiers: 3-phase Voltage Source - Operation Analysis • Inductor limits the harmonics in the input current due to PWM switching • VAO,1 magnitude and phase angle ECEN 613 Rectifiers & Inverters can be adjusted to control the direction of power flow Dr. Prasad Enjeti, Department of Electrical & Computer Engineering, Texas A&M University http://enjeti.tamu.edu PWM Rectifiers: 3-phase Voltage Source - Operation Analysis Design Example: ECEN 613 Rectifiers & Inverters Dr. Prasad Enjeti, Department of Electrical & Computer Engineering, Texas A&M University http://enjeti.tamu.edu PWM Rectifiers: 3-phase Voltage Source: Closed loop Control Vs ⋅ E a ,1 ⋅ sin(δ ) P = Xs 2 Q= Vs Xs Ea ,1 1 − ⋅ cos(δ ) Vs Control of Three Phase PWM Rectifier/Inverter The most popular control algorithm for three phase PWM rectifier/inverter is known as Current Control (CC). This algorithm calculates reference currents needed to satisfy reference dc-link voltage as well as zero reactive power transfer. Then line currents are controlled corresponding to reference currents through closed loop current regulators. Advantages of current control include – utilize space vector PWM, minimize switching loss, and reduce current ripple due to high switching frequency. ECEN 613 Rectifiers & Inverters ω Dr. Prasad Enjeti, Department of Electrical & Computer Engineering, Texas A&M University http://enjeti.tamu.edu ω 17 PWM Rectifiers: 1-phase Voltage doubler configuration • 1-phase UPS – with LV and HV battery • 1-phase to 3-phase Converter ECEN 613 Rectifiers & Inverters Dr. Prasad Enjeti, Department of Electrical & Computer Engineering, Texas A&M University http://enjeti.tamu.edu 18 ECEN 613 Rectifiers & Inverters Dr. Prasad Enjeti, Department of Electrical & Computer Engineering, Texas A&M University http://enjeti.tamu.edu 19 PWM Rectifiers: 1-phase UPS configuration ECEN 613 Rectifiers & Inverters Dr. Prasad Enjeti, Department of Electrical & Computer Engineering, Texas A&M University http://enjeti.tamu.edu 20 PWM Rectifier - Static VAR Compensator ECEN 613 Rectifiers & Inverters Dr. Prasad Enjeti, Department of Electrical & Computer Engineering, Texas A&M University http://enjeti.tamu.edu 21