Xilinx Fpga Based Pwm Technique For Controlling Multilevel Inverter

This chapter deals with the classification and basic operation of electric variable speed drive system and scope, merits and demerits of DC and AC drives. Then AC induction motor drive is selected for complete description. Here AC drive system is presented with its components like inverters, position sensors and current controller.

Fig. 11 shows a comparison of DPWM2O, DPWMLPF2 and GDPWMO at 0.4 modulation index. The inverter is operating with 160 Hz fundamental frequency and 7.68 kHz switching frequency. The output power factor angle is 45°. It can be seen that each strategy produces 32 pulses in one cycle. However, the clamping interval of the GDPWMO strategy is perfectly aligned with the line current peaks, whereas the DPWM2O and DPWMLPF2 strategies incurs switching instances around the current peaks.

The innovative inverter technology produces safe, smooth power, protecting your sensitive electronics (computers, smartphones, etc.) from damage.

Though there are different types of generators are available like DC shunt ,series and compound generator and AC types parallel and compound DC generators, synchronous and asynchronous(induction generators), so there will be considerable increase in complexity of embedded

Firstly the hybrid HVDC transmission system configuration is given. Next MMC description is given and then the control strategies for the rectifier and inverter is presented. Finally the performance of system under steady state and transient conditions is discussed with the help of MATLAB results.

Now a days, the switching power supply market is flourishing quickly. The trend is for DC-AC converters with low cost, higher efficiency, power saving that enable maximum features. In this project, a single-stage three-switch buck-boost inverter is designed, where stepping up, stepping down and inversion operation will takes place in single stage. This proposed inverter will overcome all the drawbacks of traditional one. Coupled inductor plays a very important role in energy transfer and eliminates the use of line frequency transformer. As the inverter having only three switches, the controlling of switches also easier than conventional one. And it has also advantages like compact design, reduced switching losses, component size, and cost.

The number of power switches is reduced by using single power conversion stage and by properly choosing the subsystems of the inverter.

Moreover, input node voltages and currents can be referred to the input terminal voltages of the inverter with reference to ground point and the corresponding currents from each node of the capacitors to the inverter respectively. As an example, input node (dc) currents by I_1,I_2 etc., and input node (dc) voltages are designed by V_1,V_2, etc as shown in Figure 1a. V_a,V_b and V_c are the root mean square (rms) values of line load voltages; I_a,I_b and I_c are the rms values of the line load currents. Figure 3.1 a shows the schematic of a pole in a multilevel inverter where V_a indicates an output phase voltage that can predicted at any voltage level depending on the selection of node (dc) voltage V_1,V_2 etc. By connecting switch to one node at a time, one can easily obtain the desired output. Figure 3.2 shows the typical output voltage of a five-level inverter. The structure of multilevel inverter must (1) have less switching devices as far as possible, (2) have capability of withstanding at very high input voltage for high-power applications, and (3) have lower switching frequency for each switching

To study the impact of VSFPWM on switching loss reduction over the entire modulation index range, the simulations were carried out different speeds (modulation indices) for a constant load torque. Table II and Table III compares the current ripple, and the percentage change in the current distortion and the switching losses for CSFSVPWM-VSFSVPWM and CSFDPWM2-VSFDPWM2 techniques respectively. Similar to the analytical results at section II, there is higher switching loss reduction capability at higher speed due to higher variation in current ripple at higher speeds (modulation indices). For example, with VSFSVPWM, around 15% switching loss reduction is obtained, whereas with VSFDPWM2, around 7.2% switching loss reduction is obtained. The difference in switching loss reduction capability in comparison to analytical results is attributed to the

Space Vector PWM (SVPWM) refers to a special switching sequence of the upper three power transistors of a three-phase power inverter. It has been shown to generate less harmonic distortion in the output voltages and or currents applied to the phases of an AC motor and to provide more efficient use of supply voltage compared with sinusoidal modulation technique. The biggest difference from other PWM methods is that the SVPWM uses a vector as a reference. This gives the advantage of a better overview of the system.

For reverse voltage blocking a diode is used in series with the self-commutating device (IGBT) . However, GTO-based configurations have restricted frequency of switching they do not need the series diode. They are considered sufficiently reliable, but have higher losses and require higher values of parallel ac power capacitors. Moreover, they cannot be used in multilevel or multistep versions to improve performance in higher ratings.

A few recent papers [53]-[56] have demonstrated a virtual synchronous machine (VSM) concept, particularly for microgrid applications and usually for distributed generators utilizing the same ac-dc-ac conversion stages. The same concept applied on flywheel based energy storage is discussed in [57]. Given the similarities existed in the MEA power grid and motor controlled thermal storage, it is deemed feasible to implement the VSM concept in this research. A high-level description is shown in Fig. 3. For a synchronous machine in the rotating reference frame, the d-q voltage and current relationship is shown in (1a-b), where vg is the grid voltage, R is the stator resistance, M is the magnetizing, and Ld = Lq = L is assumed. On the other hand, the active front end (i.e., the hex-bridge converter connected to the gird) follows (2a-b) in d-q reference frame at ωc rotating speed, where Rg and Lg are grid tied resistance and inductance, and vc is the output voltage at the converter controlled by modulation index from the dc voltage bus []. The analogy between (1a-b) and (2a-b) is straightforward. By equating the first three terms and varying the modulation indices, md and mq, the active front end mimics the VSM proposed in [ZhongQC]. The purpose of the ac motor-tied inverter (i.e., the left hex-bridge converter in Fig. 3) is to main a constant 270 V dc bus by adjusting the motor speed and torque using conventional vector controls. Given the limited

Brushless DC (BLDC) motors are used for many low and medium power drives applications due to their high efficiency, high flux density per unit volume, low maintenance requirement, low EMI problems, high ruggedness and a range of speed control. The commutation in PMBLDCM is accomplished by solid state switches of a three phase voltage source inverter (VSI). There is a necessity of an improved power quality (PQ) as per the

Abstract—for very high voltage gain of a Photo-Voltaic system, this paper proposed a buck-boost inverter of single stage. DCM (Discontinuous conduction mode) and MPPT (maximum power point tracking) is employed to get one power factor. Minimization of switching losses is employed with only two switches and operated at very high frequency. Easy control capability, optimum size, affordable cost with high voltage gain made the system employable. AC voltage conversion is achieved along with boosting of DC voltage of Photo-Voltaic system of inverter. Obstacle shadow variations also reduced by means of having the possibility of reduced series connected modules; this ability is due to the high voltage gain. Since the proposed design has the two buck boost converter each one operates for only one half cycle and the Discontinuous conduction mode operates at unit power factor. Simulation results assure the proposed idea of the single stage interleaved inverter for high voltage gain applications.

In the present era of advanced technologies, power electronics devices have wide applications. These devices are important for industrial and domestic uses but they generate the power quality problems [1-2].these problems are created on account of these devices