Three level inverter
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The document presents a project on diode clamp three-level inverters, detailing the principles of inverters, specifically multi-level inverters, and their topologies such as diode clamped, flying capacitor, and cascaded H-bridge types. It discusses the advantages and disadvantages of each type, their applications in high-voltage systems, and techniques like sinusoidal PWM for controlling output voltage. Additionally, it covers hardware implementations, simulation results, and comparisons between conventional and multi-level inverters.
Three level inverter
- 1. PROJECT PRESENTATION ON DIODE CLAMP THREE LEVEL INVERTER UNDER THE GUIDENCE OF; Mr. Ashish Srivastava PRESENTED BY; Vinay singh
- 2. INTRODUCTION TO INVERTER A power inverter, or inverter, is an electronic device or circuitry that changes direct current (DC) to alternating current (AC). The input voltage, output voltage and frequency, and overall power handling depend on the design of the specific device or circuitry. The inverter does not produce any power; the power is provided by the DC source.
- 3. CONCEPT OF MULTI-LEVEL INVERTER Mostly a two-level inverter is used in order to generate the AC voltage from DC voltage A two-level Inverter creates two different voltages for the load If Input Voltage is Vdc. Then it produces output as +Vdc/2 AND –Vdc/2 based on switching of power devices. This method of generating AC output seems to be Effective but posses following drawbacks: • High Harmonic Distortion in Output Voltage. • High dv/dt.
- 4. CONCEPT OF MULTI-LEVEL INVERTER In order to create a smoother stepped output waveform, more than two voltage levels are combined together and the output waveform obtained in this case has lower dv/dt and also lower harmonic distortions. Smoothness of the waveform is proportional to the voltage levels, as we increase the voltage level the waveform becomes smoother but the complexity of controller circuit and components also increase. 2-Level output 3-Level Output 5-Level Output
- 5. MULTI LEVEL INVERTER TOPOLOGIES The elementary concept of a multilevel converter to achieve higher power is to use a series of power semiconductor switches with several lower voltage dc sources to perform the power conversion by synthesizing a staircase voltage waveform. Capacitors, batteries, and renewable energy voltage sources can be used as the multiple dc voltage sources. however, the rated voltage of the power semiconductor switches depends only upon the rating of the dc voltage sources to which they are connected. There are several topologies of multilevel inverters available. The difference lies in the mechanism of switching and the source of input voltage to the multilevel inverters. Three most commonly used multilevel inverter topologies are: • Cascaded H-bridge multilevel inverters • Diode Clamped multilevel inverters • Flying Capacitor multilevel inverters. 5
- 6. MULTI LEVEL INVERTER TOPOLOGIES DIODE CLAMPED MULTI LEVEL INVERTER This topology uses clamping diodes in order to limit the voltage stress of power devices. It was first proposed in 1981 by Nabae, Takashi and Akagi. A k level diode clamped inverter needs • (2k – 2) switching devices, • (k – 1) input voltage source and • (k – 1) (k – 2) diodes in order to operate. Vdc is the voltage present across each diode and the switch. Three level diode clamp multi-level inverter (one leg) Switching states in one leg of the three-level diode clamped inverter
- 7. FLYING CAPACITOR MULTILEVEL INVERTER This configuration is quite similar to previous one except the difference that here flying capacitors is used in order to limit the voltage instead of diodes. The input DC voltages are divided by the capacitors here. The voltage over each capacitor and each switch is Vdc. A k level flying capacitor inverter requires. • (k - 1) x (k - 2)/2 auxiliary capacitors per phase leg • (2k – 2) switches and • (k – 1) number of capacitors in order to operate. Switching state is same as diode clamped Multilevel Inverter Advantages of Flying Capacitor Multilevel Inverters • Static var generation is the best application of Capacitor Clamped Multilevel Inverters. • For balancing capacitors’ voltage levels, phase redundancies are available. • We can control reactive and real power flow Disadvantages of Flying Capacitor Multilevel Inverters • Voltage control is difficult for all the capacitors • Complex startup • Switching efficiency is poor • Capacitors are expansive than diodes Three level Flying Capacitor multi-level inverter (one leg)
- 8. CASCADE H-BRIGDE MULTI LEVEL INVERTER Each cell contains one H-bridge and the output voltage generated by this multilevel inverter is actually the sum of all the voltages generated by each cell i.e. if there are k cells in a H-bridge multilevel inverter then number of output voltage levels will be 2k+1. Advantages of Cascade H Bridge Multilevel Inverters • Output voltages levels are doubled the number of sources • Manufacturing can be done easily and quickly • Packaging and Layout is modularized. • Cheap Disadvantages of Cascade H Bridge Multilevel Inverters • Every H Bridge needs a separate dc source. • Limited applications due to large number of sources. Cascaded inverter circuit topology and its associated waveform
- 9. COMPARISON OF DIFFERENT MULTILEVEL INVERTER TOPOLOGIES S.No. Topology Diode Clamped Flying Capacitor Cascaded 1 Power semiconductor switches 2(m-1) 2(m-1) 2(m-1) 2 Clamping diodes per phase (m-1)(m-2) 0 0 3 DC bus capacitors (m-1) (m-1) (m-1)/2 4 Balancing capacitors per Phase 0 (m-1)(m-2)/2 0 5 Voltage unbalancing Average High Very small 6 Applications Motor drive system, STATCOM Motor drive system, STATCOM Motor drive system, PV, fuel cells, battery system
- 10. Sinusoidal PWM Technique In this technique, an isosceles triangle carrier wave of frequency fc is compared with the fundamental frequency fr sinusoidal modulating wave, and the points of intersection determines the switching points of power devices. Two important parameters of the design process are • Amplitude Modulation Index Ma= 𝐕𝐫 𝐕𝐜 where Vr = Peak amplitude of reference control signals Vc = Peak amplitude of the Triangular carrier wave. • Frequency Modulation Index Mf = 𝐟𝐜 𝐟𝐫 where fc = frequency of the carrier wave fr = reference sinusoidal signal frequency. Ma determines the magnitude of output Voltage fr controls the frequency of output voltage fc determines switching frequency of power semiconductor devices. 10
- 11. Sinusoidal PWM Technique Types of Multiple Carrier-based SPWM Techniques: Sinusoidal PWM can be classified according to carrier and modulating signals. This work used the intersection of a sine wave with a triangular wave to generate firing pulses. There are many alternative strategies, such as: I. In-Phase Disposition (PD) II. Phase Opposition Disposition (POD) III. Alternative Phase Opposition Disposition (APOD) I. In-Phase Disposition (PD): In this technique, All the triangular carrier waves are In-Phase with each other. 11
- 12. II. Phase Opposition Disposition (POD): In this technique, the carrier signal above Zero reference are In-Phase but Phase shifted by 180° from those carrier signals which are below zero reference. III. Alternative Phase Opposition Disposition (APOD): In this method, each carrier signal is phase shifted by 180° from the adjacent carrier signal. 12
- 13. MODELING OF PHASE DISPOSITION(PD) MODULATION TECHNIQUE GENERATION OF MODULATING SINE WAVE In order to generate fundamental component of output voltage at 50Hz frequency, the frequency of reference sine wave is set to 50Hz itself. 13 This option is used to apply PHASE SHIFT in Sine wave in terms of RADIANS. 120° = 2*pi/3 240° = -2*pi/3 This option is used to apply desired frequency of Sine wave in terms of RADIANS
- 14. MODELING OF PHASE DISPOSITION(PD) MODULATION TECHNIQUE GENERATION OF TRIANGULAR CARRIER WAVE Let the switching frequency, fs = 1.1 kHz Fundamental(Output) Frequency, fr = 50 Hz Hence, Frequency Modulation ratio, Mf = 22( 𝑓 𝑠 𝑓 𝑟 ) which means there exist 22 cycles of triangular wave for each cycle of Sine wave. Time Period, T 𝑠 = 1 𝑓 𝑠 = 1 1100 = 9.09 * 10-4 sec. Let, 𝑥 = 𝑇 𝑠 4 = 0.0002273 sec. 14
- 15. MODELING OF PHASE DISPOSITION(PD) MODULATION TECHNIQUE GENERATION OF FIRING PULSES PD SPWM GENERATION FOR 3-LEVEL INVERTER : • Three level pulse width modulated waveforms can be generated by sine-carrier PWM. • Sine carrier PWM is generated by comparing the three reference control signals (one for each phase) with two triangular carrier waves. Vdc/2 , Vref,i > Vtri,1 Vio = 0 , Vtri,1 > Vref,i > Vtri,2 Where i= a, b or c phase -Vdc/2 , Vtri,2 > Vref, Simulated SPWM output for 3-Level Inverter 15
- 16. MODELING OF PHASE DISPOSITION(PD) MODULATION TECHNIQUE GENERATION OF FIRING PULSES PD SPWM GENERATION FOR 3-LEVEL INVERTER : Simulink Model for 3-Level PD SPWM Generation Firing Pulses for Upper & Lower Switches for a-Phase of 3-Level inverter 16
- 17. SIMULATION MODELS OF DIODE CLAMPED THREE LEVEL INVERTER Specifications(For both 3-Level & 5-Level Inverter): • Supply Voltage = 200V • Fundamental Frequency (fr) = 50 Hz • Switching Frequency (fs) = 1.1 KHz • Amplitude Modulation Index (Ma) = Variable • Frequency Modulation Index (Mf) = 22 Simulink Model of THREE Level Diode Clamped SPWM Inverter 17
- 18. SIMULATION RESULTS Simulated Line voltage of 3-Level diode clamped inverter Harmonic Spectrum of 3-Level diode clamped inverter for R= 25Ω/phase and ma=0.9 18
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- 20. SIMULATION RESULTS Simulated Line voltage of 2-Level diode clamped inverter Harmonic Spectrum of 2-Level diode clamped inverter
- 21. HARDWARE IMPLEMENTATION MOSFET DRIVE CIRCUIT A gate driver is used when a pulse width- modulation (PWM) controller cannot provide the output current required to drive the gate capacitance of the MOSFET. Gate drivers may be implemented as dedicated ICs, discrete transistors, or transformers. They can also be integrated within a controller IC. Partitioning the gate-drive function off the PWM controller allows the controller to run cooler and be more stable by eliminating the high peak currents and heat dissipation needed to drive a power MOSFET at very high frequencies. 21
- 22. COMPONENTS USED MOSFET (IRF 840) TRANSISTER (BD 139) OPTOCOUPLER (PC 817) VARISTOR (MOV-20D751K) ZENER DIODE RESISTANCE CAPACITOR DIODE APPARATUS USED IN TESTING PULSE GENERATOR DSO POWER SUPPLY LOAD 22
- 23. TESTING OF MOSFET DRIVE CIRCUIT 23
- 24. ARDUINO Arduino Uno is a microcontroller board based on the ATmega328P (datasheet). It has 14 digital input/output pins (of which 6 can be used as PWM outputs), 6 analog inputs, a 16 MHz quartz crystal, a USB connection, a power jack, an ICSP header and a reset button. It contains everything needed to support the microcontroller; simply connect it to a computer with a USB cable or power it with a AC-to-DC adapter or battery to get started "Uno" means one in Italian and was chosen to mark the release of Arduino Software (IDE) 1.0.
- 25. IMPLEMENTED HARDWARE AND RESULT 25
- 26. COMPARISON OF CONVENTIONAL TWO LEVEL INVERTERS AND MULTILEVEL INVERTER S.No. Conventional Inverter Multilevel Inverter 1 Higher THD in output voltage Low THD in output voltage 2 More switching stresses on devices Reduced switching stresses on devices 3 Not applicable for high voltage applications Applicable for high voltage applications 4 Higher voltage levels are not produced Higher voltage levels are produced 5 Since dv/dt is high, the EMI from system is high Since dv/dt is low, the EMI from system is low 6 Higher switching frequency is used hence switching losses is high Lower switching frequency can be used and hence reduction in switching losses 7 Power bus structure, control schemes are simple control scheme becomes complex as number of levels increases 8 Reliability is high Reliability can be improved, rack swapping of levels is possible 26
- 27. ADVANTAGES OF THREE LEVEL INVERTER The multilevel inverters produce common mode voltage, reducing the stress of the motor and don’t damage the motor. Multilevel inverters can draw input current with low distortion. The multilevel inverter can operate at both fundamental switching frequencies that are higher switching frequency and lower switching frequency. It should be noted that the lower switching frequency means lower switching loss and higher efficiency is achieved. Selective harmonic elimination technique along with the multi level topology results the total harmonic distortion becomes low in the output waveform without using any filter circuit. All of the phases share a common dc bus. Reactive power flow can be controlled. 27
- 28. DISADVANTAGES OF THREE LEVEL INVERTER Need high voltage rating diodes to block the reverse voltages. circuit increases with the increase in the number of output voltage levels. Extra clamping diodes required are (n-1)(n-2) per phase.
- 29. APPLICATIONS OF MULTILEVEL INVERTER High-voltage and Medium-voltage motor drives. High voltage dc transmission. Flexible AC transmission system (FACTS). Traction. Active filtering. Utility interface for renewable energy systems. Variable speed motor drives. High voltage system interconnections.