* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Pure Sinusoidal PWM Signal Generation Technique
Integrating ADC wikipedia , lookup
Wien bridge oscillator wikipedia , lookup
Analog television wikipedia , lookup
Transistor–transistor logic wikipedia , lookup
Analog-to-digital converter wikipedia , lookup
Electronic engineering wikipedia , lookup
Standing wave ratio wikipedia , lookup
Oscilloscope history wikipedia , lookup
Audio power wikipedia , lookup
Schmitt trigger wikipedia , lookup
Operational amplifier wikipedia , lookup
Regenerative circuit wikipedia , lookup
Voltage regulator wikipedia , lookup
Phase-locked loop wikipedia , lookup
Current mirror wikipedia , lookup
Power MOSFET wikipedia , lookup
Valve audio amplifier technical specification wikipedia , lookup
Resistive opto-isolator wikipedia , lookup
Surge protector wikipedia , lookup
Valve RF amplifier wikipedia , lookup
Index of electronics articles wikipedia , lookup
Radio transmitter design wikipedia , lookup
Switched-mode power supply wikipedia , lookup
Opto-isolator wikipedia , lookup
Pure Sinusoidal PWM Signal Generation Technique for Three Phase Voltage Source Inverter with Simulation of PWM Inverter Aftab Rafeeq and Atta-ur-Rehman Department of Electrical Engineering Superior University Main Raiwind Road, Lahore, Punjab Province, Pakistan {aftab_rafeeq & rehman10138}@yahoo.com Abstract - Inverter is the most important device to the everincreasing reliance on electronic devices which utilize alternating current power highlights the problems associated with the unexpected loss of power from the Electric grid and in the industry. The main purpose is to design pure sine wave inverter otherwise it disturb the power quality like variation in voltage magnitude, transient in voltages and currents, harmonic content in the waveforms for AC power etc. The places where the electrical infrastructure is not well-developed, brown-outs can prove to be fatal which makes electronic instruments defective. Therefore, there is a need for cost-effective and reliable pure-sine wave inverters. The Pulse Width Modulation (PWM) technique is one of the most popular new techniques, with this technique harmonics are reduced of inverters. These are used by three sine waves displaced with 120 phase difference as reference signals for three phase inverter which is obtaining pure sine wave in direct current-to-alternating current inverter [1]. The output waveforms in the proposed Pulse-width modulation inverter are investigated both theoretically and experimentally. The switching scheme from direct current to alternating current results in unwanted harmonic voltages in the range of the switching frequency and higher, which can be easily filtered out. Simulations and experimental work are carried out and results presented to demonstrate the feasibility of the proposed approach. Simulation is carried out by using PROTEUS (software) and in the experimental work an innovative design prototype model is proposed and developed to verify the simulation results. In this project automatic voltage regulator microcontroller (ATMEGA 328P) is used to generate the Pulsewidth modulation pulses. The simulation results are shown harmonic reduction pure sine wave with PWM techniques. If we do not have pure sine signal, our appliances give sound during their working due to harmonics. If we have impure signal, our load will heat up. Due to impure signal the life of load decreases. Due to pure sine wave we can improve power quality and power factor. Index-PWM, AC, DC, UART, ADC I. INTRODUCTION In the last years, new energy sources have been proposed and developed due to the dependency and constant increase of costs of fossil fuels. On other hand, fossil fuels have a huge negative impact on the environment. In this context, the new Bilal Masood Department of Electrical Engineering Superior University Main Raiwind Road, Lahore, Punjab Province, Pakistan [email protected] energy sources are essentially renewable energies. It is estimated that the electrical energy generation from renewable energy sources will increase from 19%, in 2010, to 32%, in 2030, leading to a consequent reduction of CO2 emission. In rural areas particularly in the developing world, where most of the population up to 80% is located, more than 1 billion people lack the essential energy services to satisfy the most basic needs and to improve their social and economic status. The growing energy demand around the world led us to utilize these renewable energy resources. In recent years, the efforts to spread the use of renewable energy resources instead of pollutant fossil fuels and other forms have increased. To utilize these renewable energy resources an inverter is essential which converts DC power to AC power as most of the renewable energy is found in DC form. In hybrid power system and micro-grid system the use of inverter is significant. In industrial applications, such as single phase and Three Phase Induction Motor & other rotating machines, variable frequency &variable voltage supply is needed. To vary the supply frequency and supply voltage, voltage source inverter (VSI) is used. The voltage source inverters (VSIs), where the independently controlled AC output is a voltage waveform, behave as voltage sources required by many industrial applications. While the single-phase VSIs cover low-range power applications, three-phase VSIs cover medium to highpower applications. Inverter is the most important device to utilize the renewable energy sources efficiently. The Sinusoidal Pulse Width Modulation (SPWM) technique is one of the most popular PWM techniques for harmonic reduction of inverters since there are used three sine waves displaced in 1200 phase difference as reference signals for three phase inverter. In present, the SPWM switching signal is developed with the help of distinct FPGAs, micro-controllers and microprocessors. But for these types of accessories, it is necessary the programming or coding. This paper shows the SPWM technique for harmonic reduction & represents how to generate SPWM switching signal using different simple Operational-Amplifier (Op-Amp) circuits/analog circuits for three phase pulse width modulated (PWM) voltage source inverter (VSI). All the Op-Amp circuits are simulated and their outputs are shown step by step. This analog circuit (Op- Amp) controlled voltage source inverter is simulated for both standalone load & high voltage sensitive loads/systems like micro-grid system and large industrial machines respectively without transformer & with transformer. Before and after the harmonic reduction, the simulation results are shown, and appropriate passive filter is used in it. Moreover, the paper expresses two classic inverter based micro grid system structures where one is with common DC bus & another one is with common AC bus. Conventionally, there are two ways Direct current (DC) or Alternating current (AC) in which electrical power is transmitted. Direct current (DC) comes from a source of constant voltage and is suited for small devices and short level transmission. Alternating current (AC) power consists of a sinusoidal voltage source in which a continuously changing voltage (and current) can be used to employ magnetic factors. Long distance electrical transmission support AC power, since the voltage can be promoted easily with the use of transformers and powerplants. By enhancing the voltage, low current is needed to provide a given amount of power to a load, decreasing the resistive loss through conductors. However, AC power is not always available and the need for mobility and simplicity has given batteries an advantage in portable power. Since the energy stored in a battery is in dc form so to use this stored power from battery we need to convert this dc form of energy in to ac form. For this conversion, here comes the concept of power inverters [2]. The device which can convert electrical energy of DC form into AC form is known as power inverter. Inverters can come in many distinct varieties, differing in price, efficiency, power and purpose. Generally inverters are of two types: single and three phase inverters. According to their output there are classified into three types: square wave, modified-sine wave and pure sine wave. Square wave and modified-sine wave inverters are less expensive to make but high heat generation and high unused harmonic energy delivered to a load. The output is not appropriate for delicate electronic devices which rely on particular timing. Pure sine wave inverters provide more accuracy, less heat generation and less unused harmonic energy delivered to a load, but they are more expensive and more complex in design. Pure sine wave inversion is accomplished by taking a DC voltage source and switching it across a load using an H-bridge. If this voltage needs to be enhanced from the DC source, it can be accomplished either after the AC stage by using a boost transformer, or before the AC stage by using a DC-DC boost converter. The inverted signal itself is collected of a pulsewidth-modulated (PWM) signal which encodes a sine wave. The role cycle of the output is changed such that the power transmitted is exactly that of a sine-wave. This output can be used alternatively and can be filtered easily into a pure sine wave. Here, the design of a true sine wave inverter, directing on the inversion of a DC high-voltage source. It therefore astimate the creation of a DC-DC enhance phase. DC-AC inverters have been widely used in industrial applications such as static frequency changes, uninterruptible power supplies and AC motor drives. Nowadays , the inverters are also playing important roles in renewable energy applications as they are used to link a photovoltaic or wind system to a power grid. II. SINUSOIDAL PWM FOR THREE PHASE INVERTER For three phase inverters there are three sinusoidal reference waves (Vra, Vrb, Vrc) each shifted by 120 0. A carrier wave is compared with reference signal corresponding to a phase to generate the gating signals for that phase. Comparing the carrier signal Vcr with reference phases Vra, Vrb and Vrc produces g1, g3 and g5 respectively. The instantaneous line to line output voltage is Vab = Vs. (g1 g3) The output voltage is generated by eliminating the condition that two switching devices in the same arm cannot conduct at the same time [3-6]. The normalized carrier frequency mf should be odd multiples of three. Thus, all phase-voltage are identical, but 1200 out of phase without even harmonics. Moreover, harmonics at frequencies multiple of three are identical in amplitude and phase in all phases. For instance, if the ninth harmonic voltage is in phase a Van9(t) = V9sin(9wt) The corresponding ninth harmonic in phase b will be, Vbn9(t) = V9 sin(9(wt – 1200)) = V9 sin(9wt 10800) = V9 sin(9wt) Thus, the ac output line voltage does not contain the ninth harmonic. Vab = Van Vbn Therefore, for odd multiples of three times the normalized carrier frequency mf the harmonics in the AC output voltage appear at normalized frequencies fh centered around mf and its multiplies, specially at n = jmf ± k Where j = 1, 3, 5…….for k = 2, 4, 6…. And j = 2, 4,….for k = 1, 5, 7….. Such that n is not a multiple of three. For nearly sinusoidal AC load current, the harmonics in the DC link current are at frequencies given by: where j = 0,2,4….for k = 1,5,7…and j = 1,3,5…for k = 2,4,6…,such that is positive and not a multiple of three. Because the maximum amplitude of the fundamental phase voltage in the linear region (M ≤ 1) is , the maximum amplitude of the fundamental ac output line voltage is . Therefore, one can write the peak amplitude as: For 0 <M< 1 To further increase the amplitude of the load voltage, the amplitude of the modulating signal can be made higher than the amplitude of the carrier signal, which leads to over modulation. The benefit of choosing the PWM over analog control is increased noise immunity which the PWM is sometimes used for communication. Diverting from an analog signal to PWM can increase the length of a communications channel dramatically. At the receiving end, a suitable RC (resistor-capacitor) or LC (inductor-capacitor) network can remove the modulating high frequency square wave and return the signal to analog form. So, the filter requirement can be decreased and the overall inverter size can be reduced. The disadvantages of PWM are like more complex circuit for the switching, higher switching loss due more to frequent switching, difficult to implement and more Electro Magnetic Interference (EMI) loss. III. 180° CONDUCTION In 180° conduction each transistor conducts 180⁰. Generally, there are six modes of operating the switches, where in a cycle the phase shift of each mode is 60º. In order to generate a desired voltage waveform, the transistor conduction moves from one state to another. The gating signals as shown in Figure 1 are shifted from each other by 60º to obtain 3-phase balanced (fundamental) voltages [8-11]. These all switching states are shown in Table 1. The load can be connected in wye or delta connection. The line current is determined when the phase current are known. For a wye connected load, the line to neutral voltages must be determined to find the phase current. Table 1 Switch states State S1,s2,s6 on S4,s5,s3 off S2,s3,s1 on S5,s6,s4 off S3,s4,s2 on S6,s1,s5 off S4,s5,s3 on S1,s2,s6 off S5,s6,s4 on S2,s3 ,s1 off S6,s1,s5 on S3,s4,s2 off S1,s3,s5 on S4,s6,s2 S4,s6,s2 on S1,s3,s5 off State no 1 Switch state 100 Vab Vbc Vca Vdc 0 -Vs 2 110 0 Vdc -Vdc 3 010 -Vdc Vdc 0 4 011 -Vdc 0 Vdc 5 001 0 -Vdc Vdc 6 101 Vdc -Vdc 0 7 111 0 0 0 8 000 0 0 0 IV. PROPOSED MODEL For DC-AC, we required Automatic Voltage Regulator (AVR), Microcontrollers, Logic circuit, Gate drivers, Amplifiers and filters. We build a block diagram, as shown in figure 2, Here we show out the diagram of single phase for simplicity. In three phases we simply combine three single phase circuits. AVR and Controllers control the circuit Voltages and give a proper signal to Logic gates. Logic Gates starts their switching and gives a high or (require) signal to Gate Driver, with the help of Amplifiers. Gate Driver select the mode And the send an AC signal to the Power Circuit. We Get our Out Put from Power Circuit Fig. 1 Waveforms gating signal 180⁰ PWM Fig. 2 Block Diagram of pure sine wave inverter A. Microcontrollers In our Circuit we use 2 Microcontrollers AT89C51 and ATMEGA-328P. Selection of Microcontroller contains following features: Internal EEPROM, Serial synchronous communication, Serial UART, Timers, Out-compares, Input captures, PWM, ADC, Modem device, Digital signal processing (DSP), Ports with wireless interface and related processing instructions capable CPU, USB/PCI interface devices. A microcontroller already contains all components which allow it to operate standalone and it has been designed in particular for monitoring and/or control tasks. The processor includes memory; various interface controllers, timers, an interrupt controller, general purpose I/O pins which allow it to directly interface to the other equipment. Controller AT89C51 get the input from DC source and start their operation as we required from this [12-16]. Internally pin configuration of micro controller AT89C51 is shown in Figure 3. Microcontroller ATMEGA328P circuit contains AVR series. It is programmed to generate six 180° conduction gate signals at digital PWM pins of 3, 5, 6, 9, 10 and 11. A PWM signal is generated at a pin. Digital input output pins are 14 in which 6 provide PWM output. AT89C51 was also used for generating the three phase shift in the circuit. These circuits are implemented on PROTEUS. Fig. 4 Schematic diagram of logic circuit. C. Gate Driver The basic purpose of gate driver module is to optically isolate the Microcontroller circuit from the Gates. The requirment of the isolation is due to back emf of motor capacity and hazardous peak voltage clamors that can disturb the control logic inward the micro-controller. For this function a TLP 250, a high speed opto coupler is used [18]. In our project, Gate Driver get the input from Logic Circuit, start their work an give an output to power circuit, as shown in Figure. Fig. 3 Schematic Diagram of AT89C51 B. Logic Circuit Logic circuit consist of an IC 74HC08. The main importance of logic circuit is it protects the push-pull transistors and to generate the square PWM in the circuit before the gate driver signal, as shown in Figure 5. When the upper gate is ON, the lower gate stays off and vice versa. First pair of AND gate generates the Square PWM while the second AND gate generates the negative and inverted square PWM. The output of the logic circuit is supplied to Gate driver module [17]. Fig. 5 Schematic Diagram of Gate driver circuit D. Filter Circuit This circuit is used to filter the unwanted level, harmonics and distortion in the circuit. It contains diodes, heat sinkers, zener diodes, capacitors and inductors. After achieving the waveform, then is will delivered to the filter circuit. Where it is filtered and final three phase pure sine wave is achieved. V.SIMULATION RESULTS The Schematic diagram contains six IGBTs gates with built in freewheeling diodes which is supplied by six pulses and DC voltage source. Need of separate power supplies is due to a fact that at any instance of operation Van, Vbn, and Vcn can have any value (different from each other) so, if they have particular supply they would little to give the same voltage level of all 3 levels [19]. That is why individual Vpulse is needed for 3 phase inverter. These simulation results are carried out in PROTEUS. Simulation in PROTEUS is done 220V DC inverter. It shows various figures of both resistive or linear load and Non resistive load such as motor load. Non resistive load are basically inductive loads. The AVR and Atmel are used to generate PWM signal and Square wave signal with phase shift. The both signal are then synchronized by the logic circuit to generate positive and negative cycles. The two cycles are produced which then further transferred to the amplifier circuit. The amplifier circuit will amplify the signals. Gate drive circuit is granting PWM signal to the IGBT’s. Signal given to the power circuit is then increases and being inverted to give AC signal. Filters are used at the output of the power circuit to give pure AC signal. The whole single phase proposed model simulation result is shown in Figure 6. Fig. 7 Schematic diagram of pure three phase sine wave Inverter Fig. 6 Schematic diagram of pure sine wave of Inverter For three phase wave we use a Schematic Diagram as shown in figure 7. In this circuit three single phase circuits are used for required output. We can see our output wave diagram of three phase inverter in figure 8. All three phases are shown in different colours. Fig. 8 Graph of pure sine wave inverter VI. CONCLUSION The goals for this project were to produce a pure sine wave DC-AC inverter that would output at 50 Hz, 440 volts RMS, would be cheap to manufacture, and fairly efficient through this method. At 12 volts powering, the H-Bridge output is a clean 50 Hz sine wave that can easily be controlled in size by the size of the sine reference in the control circuit. It is in this capability that the option of a closed loop control circuit could be implemented. In looking at the components selected and the simulations created before the actual construction of the inverter, all plan was built in mind for the purpose of effictiveness and keeping power losses to a minimum as possible. One of the main elements in the power savings is the use of a three level PWM signal rather of a two level, this allows a much less average power output to produce the sine wave required and assisting in the efficiency of the device. This project is a stepping stone to a cheaper and efficient pure sine wave inverter, by using the data collected, schematics and recommendations of the product can be boost up. Simple inclusion such as circuit protection and a closed loop control scheme could greatly improve the performance of this project. In its present condition, the project does work in the manner, the team wished and has met every goal set at the commencement of this venture. From all the simulation results it is seen that the designed Op-Amp/Analog circuit controlled PWM inverter works accurately. It fulfills all the requirements for a voltage source inverter. The THD is less than 5% after filtering. The inverter outputs can be varied by varying the resistance of potentiometer. The inverter responses better for standalone inductive loads like induction motor. If the power is not enough to supply to the grid then it will supply the power to the local standalone loads. If the carrier frequency is increased much enough then the filtering system will be much better and the loss will be less. But better response can be achieved by using the feedback system, means the closed loop control system. The future work can be done on the feedback loop system. VII. ACKNOWLEGDMENT Alhamdulillah, the highest thank to ALLAH because with His Willingness I possible to complete the research paper. I would like to thank my supervisor Mr. Bilal Masood for his advice and support throughout this paper. At the same time I would like to express my gratitude to Dr. Farooq Aslam for sharing his valuables ideas as well as his knowledge. I also wish acknowledgement to the people who gives support direct or indirectly to the paper, project and during the thesis writing. Once again, thank you very much. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. VIII. REFERENCES 15. M.H. Rashid, “Power electronics: circuits, devices, and applications”, Third Edition, Prentice Hall, 2004. R.S Annada Murth, V. Nattarasu, “ power electronics” , second revised edition B.K. Bose, “Modern power electronics and AC drives,” Prentice Hall, 2002 Y. Kang and J.D. Lavers, “Power electronics simulation: current progress and future development”, IEEE PES Summer Meeting, 1994, pp. 169-174 P.J. Van Duijsen, P. Bauer and D. Gospodaric, “Simulation based optimization of electrical drives”, PCIM 04, Nurnberg, May 25-27, ISBN 3-928643-398, pp. 922-927. P. Bauer, P. Korondi and P.J. van Duijsen, “Integrated control and circuit simulation for a motion control system”, EPE 2003, Toulouse, 2-4 September 2003, ISBN 9075815-07-7. U. Drofenik, J.W. Kolar, P.J. van Duijsen and P. Bauer, “New web-based interactive e-learning in power electronics and electrical machines”, Conference Record of the 2001 IEEE Industry Applications Conference, 36th IAS Annual Meeting, Chicago (Illinois), USA, Sept. 30 - Oct. 4, Vol. 3, pp. 1858 - 1865 (2001). G. Kron, “Equivalent circuits of electric machinery” John Wiley, New York, 1951. Zhang, R.; Boroyevich, D.; Prasad, V.H.; Mao, H.C.; Lee, F.C.; Dubovsky, S.; , "A three-phase inverter with a neutral leg with space vector modulation," Applied Power Electronics Conference and Exposition, 1997. APEC '97 Conference Proceedings 1997., Twelfth Annual , vol.2, no., pp.857-863 vol.2, 23-27 Feb 1997 A.E. Fitzgerald, C. Kingsley and S.D. Umans, “Electric machinery”, McGraw-Hill, New York, 1983. Kukrer, O, "Deadbeat control of a three-phase inverter with an output LC filter ," Power Electronics, IEEE Transactions on , vol.11, no.1, pp.16-23, Jan 1996 D. Stanciu, C.N. Popescu, "PWM Three-Level Inverter Control," aqtr, vol. 1, pp.243-247, 2006 IEEE International Conference on Automation, Quality and Testing, Robotics, 2006 Brod, David M.; Novotny, Donald W.; , "Current Control of VSI-PWM Inverters," Industry Applications, IEEE Transactions on , vol.IA-21, no.3, pp.562-570, May 1985 Bhagwat, Pradeep M.; Stefanovic, V. R.; "Generalized Structure of a Multilevel PWM Inverter," Industry Applications, IEEE Transactions on, vol.IA-19, no.6, pp.1057-1069, Nov. 1983 Amin, M.M.N.; Mohammed, O.A.; , "Vector oriented control of voltage source PWM inverter as a dynamic VAR compensator for wind energy conversion 16. 17. 18. 19. 20. system connected to utility grid," Applied Power Electronics Conference and Exposition (APEC), 2010 Twenty-Fifth Annual IEEE , vol., no., pp.16401650, 21-25 Feb. 2010 I.Hamzaoui, F. Bouchafaa, A. Hadjammar, “Investigation of the behavior of a three phase grid connected photovoltaic system to control active and reactive power with DPC”, Energy Procedia 2011, Elsevier, Volume 6, 2011, Pages 493–502. I. Colak, E. Kabalci, “Developing a novel sinusoidal pulse width modulation (SPWM) technique to eliminate side band harmonics”, International Journal of Electrical Power & Energy System, Volume 44, Issue 1, January 2013 – Elsevier, Pages 861–871. Bose, B.K., 2002, Modern Power Electronics and AC Drives, Prentice Hall PTR, New Jersey. K.S. Rajashekara, Joseph Vithayathill, “Harmonics in the voltage Source PWM Inverters,” International Journal of Electronics, Vol. 50, Issue 5. Pp. 325 337. Nazmul Islam Raju, Md. Shahinur Islam, Ahmed Ahsan Uddin, “Sinusoidal PWM Signal Generation Technique for Three Phase Voltage Source Inverter with Analog Circuit & Simulation of PWM Inverter for Standalone Load & Micro-grid System,” International Journal of Renewable Energy Research, Vol. 3, Issue 3, Pp. 1-6.