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In this work, the performance of closed-loop dual phase Interleaved Buck-Boost converter (IBBC) controlled by Dragonfly Algorithm (DA) optimized Type-III compensator has been investigated. The dual phase IBBC is constructed by connecting parallel of two identical conventional Buck-Boost converter (BBC) cells, which operate in 180° phase shifting operation (i.e., interleaving technique) between them in a switching period. The closed-loop IBBC with DA optimized Type-III controller demonstrates better performance than conventional Buck-Boost (BBC) converter & IBBC with classical Type-III controller in terms of dynamic performance, efficiency, ripple in source current and in output voltage. The efficacy of the proposed control scheme is verified by both simulation & experimental results. [ABSTRACT FROM AUTHOR]

Selective harmonic minimization-pulse amplitude modulation (SHM-PAM) generates a waveform that minimizes some selected low-order harmonics instead of eliminating them completely. This approach is highly beneficial for medium-voltage high-power inverters, where allowable amplitudes for individual harmonics (mentioned in power quality standard) are required with low switching frequencies. This work applies improved SHM-PAM proposing four new types of formulations utilizing quarter-wave (QW) and half-wave (HW) symmetry-based waveforms for three-phase five-level cascaded H-bridge (CHB) multilevel inverter (MLI) to satisfy the requirements of two well-known power quality standards, namely IEC 61000-2-12 and ER G4/5. Recently reported dragonfly algorithm (DA) is used for computing the optimum switching angles and dc-link voltages required to control the CHB MLI. The effectiveness and practicality of the proposed techniques have been investigated through extensive simulations and experimentation on a laboratory scale CHB MLI. While fulfilling the IEC 61000-2-12 and ER G4/5 voltage harmonic standards, the solutions provided by QW and HW symmetry-based waveforms are compared based on several performance indices such as waveform quality and power losses. It is found that HW symmetry waveforms provide better waveform quality and power loss profile than QW symmetry waveforms. The proposed SHM-PAM has also been compared with some existing modulation techniques to justify its mastery. Finally, the practicability of the proposed SHM-PAM technique is verified on an induction motor drive application. [ABSTRACT FROM AUTHOR]

In this brief an improved Interleaved Tri-state Buck-Boost converter (ITBBC) is newly proposed and developed. The ITBBC demonstrates excellent transient performance compared to existing Interleaved Buck-Boost converter (IBBC), mainly due to right-half-plane (RHP) zero free control-to-output (CTO) transfer function. It also produces lesser ripple than the existing Tri-state Buck-Boost converter (TBBC), due to interleaving operation. An optimized generalized Type-III controller has been employed, to improve the stability and transient performance of the closed-loop converter. The output voltage response has been investigated under load transient condition. It is appeared that the output voltage of ITBBC exhibits best transient response in both buck as well as boost modes. The experimental output voltage along with input current ripples of ITBBC, TBBC, and IBBC has been determined. It is clear that the ITBBC generates lesser ripple than the TBBC, and as expected, the IBBC produces the lowest ripple. It is also realized that due to interleaving, ITBBC exhibits better efficiency than TBBC. The proposed ITBBC can be used in applications wherever fast-response buck/boost action is needed. [ABSTRACT FROM AUTHOR]

Three-level neutral-point-clamped (NPC) inverters are being widely adopted in low-voltage low-power applications. For an intended application, the modulation strategy and the operating conditions are the two key factors that highly influence the major performance indices of the NPC inverter, such as efficiency, harmonic distortion, and voltage oscillations at neutral point (NP). Considering dynamic loading applications where the operating point varies significantly, this paper proposes an improved adjustable pulsewidth modulation (PWM) strategy for a three-level NPC inverter that can alter its modulation pattern to meet desired performance objectives for the full operation range. It has been shown that by varying two control parameters namely discontinuity control parameter and bias control parameter, the proposed modulation strategy changes its pattern between the most efficient generalized discontinuous PWM to NP oscillations-free partial dipolar PWM strategy. Additionally, to obtain a tradeoff between the performance parameters—efficiency, NP oscillations, and waveform quality—The proposed strategy has the ability to settle at the intermediate modulation patterns by transforming into a hybrid modulation signal. Furthermore, considering NP voltage unbalance mitigation as major technical challenge in adjustable modulation strategy, a voltage unbalance compensator that exhibits satisfactory balancing performance for the entire variations of modulation patterns and operating conditions has also been presented. The performance of the proposed modulation strategy in conjunction with voltage unbalance compensator has been evaluated in simulation by widely varying the speed and load of induction motor, and verified in experimentation. [ABSTRACT FROM AUTHOR]

Multilevel inverters are now-a-days being applied in electric vehicles (EV). Considering the dynamic operating conditions of an EV propelled by an induction motor, this paper proposes a flexible discontinuous modulation strategy for three-level neutral-point-clamped (NPC) inverter that can shift modulation pattern seamlessly from sinusoidal pulsewidth modulation (SPWM) to discontinuous PWM (DPWM). The modulation scheme is generalized at each degree of discontinuity to ensure minimum switching losses for variable load power factors. Additionally, a hybrid voltage balancing strategy, which comprises two sets of compensating offset signals with complementary features, has been introduced to mitigate voltage deviation problem at neutral point of the inverter. The unique feature of the proposed hybrid balancing approach is that it generates uniform compensating neutral current regardless of the level of discontinuity. This results in identical and predictable voltage balancing dynamics for the entire modulation transition covering SPWM and DPWM. It has been shown that the proposed hybrid balancing strategy does not lose its unbalance compensation strength even during transition from one modulation pattern to another. The effectiveness of the proposed scheme for wide variations in operating conditions is studied through extensive simulation, and validated in experimentation using a prototype NPC inverter with induction motor loads. [ABSTRACT FROM AUTHOR]

A discontinuous pulsewidth modulation (DPWM) strategy for three-level neutral-point-clamped (NPC) traction inverter drive for electric vehicles (EVs) with minimum switching loss for the full power factor (PF) range is developed and presented in this paper. Considering the dynamic loading conditions in an EV propelled by an induction motor (IM), the discontinuous modulation strategy is generalized to obtain minimum switching loss for a wide variations in load PF and modulation depth. The dynamic operating conditions in EV may render frequent unbalances in dc-link capacitor voltages in NPC inverter. It is demonstrated that the addition of an appropriate offset signal with the reference discontinuous signals generates compensating neutral current in the right direction, which can be used to mitigate existing unbalance in two dc-link capacitor voltages. Minimum switching loss at variable PF is attained by positioning the nonswitching clamped regions of the reference auxiliary signals according to the load PF. The effectiveness of the proposed scheme for a wide range of torque/speed variations is studied through simulation by developing a MATLAB/SIMULINK model of an IM traction inverter drive with field-oriented control strategy for closed loop control. Finally, the modulation scheme is validated through experimentation in a small-scale prototype NPC inverter with motor loads. [ABSTRACT FROM AUTHOR]

This paper proposes a unique carrier-based pulse width modulation strategy for a three-level neutral-point-clamped inverter that works satisfactorily and with uniform convergence time over the full power factor (PF) range of the load variation. It has excellent control over capacitor voltages and mitigates low-frequency oscillations in the neutral point for the full PF range. First, an investigation is made to see how the load currents get modulated to generate compensating neutral current causing charging and discharging of dc-link capacitors. It is observed that when an additional modulating voltage signal that is in phase with the corresponding phase current is added in each phase, a neutral current is produced in the right direction which can be used to compensate for any prior unbalance in capacitor voltages. It is demonstrated that the performance of this scheme is insensitive to the load PF variation (full range from zero to unity). It performs satisfactorily throughout the entire linear modulation range and eliminates any undesirable low-frequency harmonic component in the compensating neutral current. The effectiveness of the proposed scheme is verified through simulation and experimental results by varying load PF as well as modulation index with both passive and motor loads. [ABSTRACT FROM PUBLISHER]