Asymmetrical PWM Research Articles

Power quality improvement of PWM AC Chopper fed capacitor run induction motor using BFO, PSO and CSO Algorithm

This paper exhibits performance enhancement of PWM AC chopper fed capacitor run induction motor by using optimization algorithm. The PWM AC chopper utilizes enhanced asymmetrical pulse width modulation technique by incorporating four pulses in quarter cycle. The switching instants are obtained optimally by bacteria foraging optimization, particle swarm optimization and cuckoo search optimization algorithm. The power quality parameters considered in this paper are total harmonic distortion of current, total harmonic distortion of voltage, power factor and efficiency. The simulation result shows that proposed algorithm shows better performance compared to other optimization techniques.

A Symmetric Sixth-Order Step-Up Converter with Asymmetric PWM Achieved with Small Energy Storage Components

This research explores an improved operation of a recently studied converter, the so-called two-phase sixth-order boost converter (2P6OBC). The converter consists of a symmetric design of power stations followed by an LC filter; its improved operation incorporates an asymmetric pulse width modulation (PWM) scheme for transistor switching, sometimes known as an interleaved PWM approach. The new operation leads to improved performance for the 2P6OBC. Along with studying the 2P6OBC, one of the contributions of this research is providing design equations for the converter and comparing it versus the interleaved (or multiphase) boost converter, known for its competitiveness and advantages; the single-phase boost topology was also included in the comparison. The comparison consisted of a design scenario where all converters must achieve the same power conversion with an established maximum switching ripple, and then the stored energy in passive components is compared. Although the 2P6OBC requires a greater number of components, the total amount of stored energy is smaller. It is known that the stored energy is related to the size of the passive components. Still, the article includes a discussion of this topic. The new operation of the converter offers more streamlined, cost-effective, and efficient alternatives for a range of applications within power electronics. The final design of the 2P6OBC required only 68% of the stored energy in inductors compared to the multiphase boost converter, and 60% of the stored energy in capacitors. This result is outstanding, considering that the multiphase boost converter is a very competitive topology. Experimental results are provided to validate the proposed concept.

Asymmetric Space Vector Pulse Width Modulation for the Phase Current Reconstruction in Three-Phase Inverters

Asymmetric Space Vector Pulse Width Modulation for the Phase Current Reconstruction in Three-Phase Inverters

A Hybrid Asymmetric Average Zero CMV PWM Strategy With Four Nearest Vectors to Optimize Harmonic Distortion for a Three-Level NPC Converter

A Hybrid Asymmetric Average Zero CMV PWM Strategy With Four Nearest Vectors to Optimize Harmonic Distortion for a Three-Level NPC Converter

Enhanced asymmetrical modulation for half‐bridge series resonant inverters in induction heating applications

AbstractThis paper presents a method that improves the reliability of half‐bridge (HB) series resonant inverters (SRI) for high‐frequency induction heating applications. Many industrial processes, like induction heat treatments, are very repetitive. This cyclical operation represents a strong limitation of the inverter's reliability, mainly due to the accelerated stress of the power semiconductors. This method consists in an enhanced asymmetrical pulse width modulation (EAPWM) that allows distributing the losses across the components, thereby reducing the cyclic increase in junction temperature of the power devices, and thus achieves a reliability that is more than twice as high as that achieved using traditional modulation methods. The work methodology includes a theoretical study of the HB inverter and a complete analysis of losses. The presented design rules have been used to implement a 25 kW, 100 kHz inverter. The use of silicon carbide (SiC) MOSFET transistors allows reaching an efficiency greater than 99%. The analytical results obtained have been experimentally validated by testing the inverter on an induction heating test bench.

Non-Isolated Current-Fed Series Resonant Converter with Hybrid Control Algorithms for DC Microgrid

Module-level power electronics can optimize the power generation of photovoltaic panels, which requires a simple topology structure, high power conversion efficiency, and wide voltage gain, corresponding to irradiance variations. This paper proposes a non-isolated current-fed L-C series resonant converter and its control algorithms. The proposed converter can obtain a buck–boost voltage gain with the hybrid control algorithm utilizing the switching frequency modulation and asymmetric pulse width modulation. The proper power stage design can guarantee the soft-switching capability for the entire operating range. Also, the control strategy is designed to obtain a small rms current. The operational principle of proposed converter is analyzed in order to design the resonant tank and control strategy. The performance of designed converter can be verified with the experimental results with a 500 W prototype converter.

A Multimode Control Scheme for Output Regulation and Voltage Balancing in a Stacked-Switch Resonant Converter With Extended High Efficiency for Wide Gain Range Applications

In this article, a new hybrid comprehensive multimode control system is proposed for a stacked-switch bidirectional CLLC resonant converter for wide voltage gain applications. By configuring the presented leg with different switching patterns, the presented leg in the converter can operate in different modes: full-wave (FW), half-wave (HW), or voltage-doubler (VD) through the converter’s built-in circuit redundancy. The proposed hybrid control scheme consists of different control modes: variable frequency modulation, pulse-width modulation (PWM), and asymmetric PWM (APWM) control. Correspondingly, four voltage gain curves are derived from the proposed converter. With the proposed approach, the converter is able to achieve constant voltage regulation while constraining the range of switching frequency, allowing very high efficiencies to be realized for a wide range of input voltages. Soft-switching is achieved for all the semiconductor devices for the entire operating range. The steady-state and dynamic performances of the proposed hybrid comprehensive control system are verified through a proof-of-concept 400-V <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim ~1$ </tex-math></inline-formula> -kV/ 700-V, 1-kW laboratory prototype. Results confirmed that the efficiency is maintained between 95.03% and 96.97% throughout the specified input voltage range.

비대칭 PWM 방식을 이용한 이중 승압 기능을 갖는 PFC 컨버터

This paper proposes a PFC converter with a double step-up function using an asymmetrical PWM scheme. For the conventional PWM scheme, the input voltage range, which maintains a double step-up function, is limited because the proposed converter has different voltage gains and characteristics when the duty ratio(D) is less than 0.5. The proposed converter has a constant voltage gain regardless of the magnitude of the input voltage and can achieve output voltage balancing by using the asymmetrical PWM scheme. A 1.6-kW prototype of the proposed converter was built and tested to verify the performance.

A Low Q Three-Phase Series Resonant Converter for PV Applications

In this paper, a soft-switched three-phase resonant converter with a low quality factor (Q) design is proposed for Photovoltaic (PV) energy harvesting systems with a very wide range of operating conditions. Due to the low quality factor (Q ≤ 1), the voltage stress across the capacitors is drastically reduced. However, a major challenge of using a low Q design is the wide switching frequency range required for operation over a wide range of load and input conditions. In order to reduce the switching frequency range, this paper introduces a hybrid modulation technique employing asymmetric pulse width modulation (APWM) along with variable frequency modulation. The proposed modulation scheme also substantially extends the soft-switching range of the converter from full-load upto 10–35% load condition over a wide range of line voltages. To sustain soft-switching in the entire operating region of the converter, the converter is operated in a hybrid structure with single-phase and burst modes at light load conditions. A comprehensive time-domain analysis of the proposed converter is presented, which greatly improves accuracy over conventional frequency-domain modeling. Experimental results from a 1 kW prototype are presented to verify the performance of the converter and validate the theoretical analysis.

A 1-W, 6.78-MHz Wireless Power Transfer System With Up-to-16.1% Light-Load Efficiency Improvement and Instant Response Through Single-Cycle-Based D TX Control

This article presents a 6.78-MHz wireless power transfer system with transmission power control. The proposed receiver (RX) with a simplified 0X/1X structure can achieve single-stage regulation in series–series resonant tank, where the charge and discharge cycle are only dependent on the hysteresis comparator. Asymmetric pulsewidth modulation is adopted in the proposed transmitter (TX), where the duty ratio ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${D}_{\text{TX}}$</tex-math></inline-formula> ) is switched based on the charge or discharge cycle of RX. With the proposed single-cycle-based <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${D}_{\text{TX}}$</tex-math></inline-formula> control, the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${D}_{\text{TX}}$</tex-math></inline-formula> will be switched to 0.25 in the discharge cycle, while it is 0.5 in the charge cycle for maximum power transmission. Therefore, the end-to-end (E2E) efficiency especially at light-load conditions can be improved, and the recovery time is nearly instant when loading changes suddenly, i.e., neglectable voltage droop can be achieved. The RX is implemented by a printed circuit board and the TX is fabricated in a 0.18- <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">μ</i> m CMOS technology. In the measurement, an output power range from 10 to 1000 mW is achieved with 60.6% peak E2E efficiency. The significant E2E efficiency improvement is observed over 10–255 mW and the maximum improvement is 16.1%. The measured load transient response verifies that the proposed design has instant response and neglectable voltage droop.

Light load analysis and topology morphing between full-/half-bridge DC-to-DC converter

ABSTRACT To retain high efficiency in a wide output voltage range and reduce the conduction and switching losses for a DC power supply, this work makes use of topology morphing between full- and half-bridge converters. The operation of the converter is better as a phase-shift modulated (PSM) full-bridge converter for a high output voltage and as the asymmetrical pulse-width modulated (APWM) half-bridge counterpart for a low output voltage. The light load operations of PSM full-bridge and APWM half-bridge DC converter are analysed in detail to account for the voltage gain variation as well as the switching and conduction losses. A suitable control algorithm is also proposed to facilitate smooth morphing transitions and eliminates the unwanted voltage and current overshoot. A laboratory converter circuit rated at outputs up to 60 V, 1.8 kW with 180 V input voltage is designed and built to verify the operation with topology morphing. The experimental results have demonstrated by adapting the PSM full-bridge DC converter to the APWM half-bridge DC converter at the low voltage range that the circuit efficiency can be effectively improved and enhanced 6% for the best.

A Complete Online Solution of Harmonic Elimination PWM Method Using Modified-Equilibrium Optimizer-Levenberg- Marquardt Algorithm

This paper proposes a novel online solution, i.e. Modified-Equilibrium Optimizer-Levenberg-Marquardt (M-EO-LM) algorithm, for the symmetric and asymmetric harmonic elimination pulse width modulation (HEPWM) methods of the modular multilevel cascaded converters. A detailed comparison of the proposed M-EO-LM algorithm with nine state-of-the-art algorithms is also presented for twenty-nine unimodal, multimodal and composite benchmark test functions. M-EO-LM has proven its effectiveness by outperforming these algorithms. EO algorithm is first introduced for the solution of HEPWM method. Its comparison with several state-of-the-art algorithms depicts its superiority; but it gets stuck in the local minima. Modified-EO (M-EO) solves the problem by enhancing its exploration ability, and is then attached to a rapid calculus-based LM method to form the novel M-EO-LM algorithm. M-EO-LM algorithm initiates the solution process by solving the HEPWM equations for nine angles ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$N=9$ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.78\leq M\leq 6.86$ </tex-math></inline-formula> ) offline in only two iterations, depicting its remarkable convergence ability. Solution angles are then divided into several groups, serving as the search space for the online M-EO-LM algorithm. A comparison between HEPWM and nearest level modulation methods based on the output voltage THD values is provided to report the maximum number of solvable HEPWM angles for a complete online solution. These angles ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$N=8$ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.78\leq M&lt; 5.18$ </tex-math></inline-formula> ) are then solved online using the M-EO-LM algorithm. Comparing the computational times of the proposed online algorithm with differential evolution-Newton Raphson algorithm proves the rapid solution behavior of the M-EO-LM algorithm, validated through the simulation and real-time experimental results.

Zero-sequence Current Suppressing Strategy for Dual Three-phase Permanent Magnet Synchronous Machines Connected with Single Neutral Point

Dual three-phase permanent-magnet synchronous machines (DTP-PMSM) connected with a single neutral point provide a loop for zero-sequence current (ZSC). This paper proposes a novel space vector pulse width modulation (SVPWM) strategy to suppress the ZSC. Five vectors are selected as basic voltage vectors in one switching period. The fundamental and harmonic planes and the zero-sequence plane are taken into consideration to synthesis the reference voltage vector. To suppress the ZSC, a non-zero zero-sequence voltage (ZSV) is generated to compensate the third harmonic back-EMF. Rather than triangular carrier modulation, the sawtooth carrier modulation strategy is used to generate asymmetric PWM signals. The modulation range is investigated to explore the variation of modulation range caused by considering the zero-sequence plane. With the proposed method, the ZSC can be considerably reduced. The simulated and experimental results are presented to validate the effectiveness of the proposed modulation strategy.

A Step-Down Resonant Modular Multilevel DC/DC Converter With Extendable ZVS Range Based on Asymmetric Triangular Current

In this article, a new step-down resonant modular multilevel dc/dc converter is proposed for medium-voltage applications. The proposed converter is derived from the combination of the modular multilevel converter (MMC) and resonant converter with a passive auxiliary circuit. It can achieve zero voltage switching (ZVS) over a wide input voltage range for all switches compared with the conventional dc/dc MMC. Specifically, the asymmetric triangular compensating current provided by the passive auxiliary circuit is first introduced to flow into the bridge arms. Then, the current bias caused by the MMC structure is eliminated in the lower side switches of the submodules to achieve ZVS. Moreover, asymmetrical pulsewidth modulation is applied to double the equivalent switching frequency and obtain a high step-down ratio. In this way, the resonant current is reduced, and the conversion efficiency is improved. Besides, the simulation and experimental results of the prototype are presented to demonstrate the viability of the proposed converter. The results convincingly verify the ability of the proposed converter to offer ZVS for all the switches over a wide input voltagerange.

Asymmetrical PWM Scheme to Widen the Operating Range of the Three-Phase Series-Capacitor Buck Converter

The three-phase series-capacitor (3P-SC) buck converter is analyzed extensively in this study for high-voltage step-down applications with a wide input voltage range. This structure is attractive due to its high step-down conversion ratio and inherent current balancing. However, the inductor currents of the 3P-SC converter become unbalanced when the duty cycle exceeds 1/3. This results in significant stress and reduces the utilization of switching devices. This article proposes an asymmetrical pulsewidth modulation (PWM) scheme for the 3P-SC converter to overcome the limitations of the conventional PWM scheme. By using the proposed switching scheme, the duty cycle can be increased to one while retaining the high conversion ratio and current balancing functionality. Thereafter, the proposed asymmetrical PWM strategy is generalized for multiphase series-capacitor (nP-SC) converters. Finally, to validate the performance of the proposed PWM strategy, a 1.2-kW prototype 3P-SC converter is fabricated and tested.

An Asymmetrical Pulsewidth Modulation With Even Harmonics for Bidirectional Inductive Power Transfer Under Light Load Conditions

An Asymmetrical Pulsewidth Modulation With Even Harmonics for Bidirectional Inductive Power Transfer Under Light Load Conditions

A Step-Up Reconfigurable Multimode LLC Converter Module With Extended High-Efficiency Range for Wide Voltage Gain Application in Medium Voltage DC Grid Systems

In this article, a newmodular multimode reconfigurable step-up resonant converter that is capable of extending very high efficiency from full load to reduced load conditions is proposed for wide voltage gain application in medium voltage dc (MVdc) grid system. The proposed converter module is able to switch from a hybrid control scheme that consists of variable frequency and phase shift control to pulsewidth modulation (PWM) control in the auxiliary switch of the output voltage quadrupler (VQ). In addition, the input bridge can also be reconfigured to a half-bridge mode to suit high input voltage range while utilizing a hybrid control technique that consists of variable frequency and asymmetrical PWM control. With the proposed approach, the converter module is able to achieve constant output voltage regulation without requiring a wide spectrum of switching frequency or phase shift control. Hence, close-to resonance operation with very high efficiency can be maintained for a wide range of input voltage and loading conditions. Soft switching operations are always guaranteed for all the primary side switches, the output diodes and the auxiliary switch in the VQ. The steady-state and dynamic performance of the proposed modular multimode step-up converter are validated through simulation results on a silicon carbide (SiC) based 360 V–1 kV/16 kV, 80-kW system and experimental results on a proof-of-concept 150–400 V/6.6 kV, 10-kW SiC laboratory prototype. Results confirmed that the efficiency is maintained between 97.8% and 99.1% from full load to at least 20% load condition for the specified input voltage range.

Novel asymmetric space vector pulse width modulation for dead-time processing in three-phase power converters

&lt;p&gt;This research analyzes the asymmetric control strategies in multilevel inverters, including asymmetric techniques in space vector modulation of power converters. Modulation parameters such as reference voltage vector (Vref), switching time, and duty cycle are derived in the three-dimensional spatial vector geometry formulation. Asymmetric space vector pulse width modulation (SVPWM) is unique in specifying modulation parameters, has unequal tetrahedron patterns, accompanied by application examples for the upper and lower sector pairs of a tetrahedron. The combination of the switch in the form of an inclined cylinder produces twelve pairs of asymmetric tetrahedrons where the voltage vector positions are in the other twenty-four tetrahedrons. The calculation shows processing dead-time in switching, which is used for current compensation in three-phase power converters.&lt;/p&gt;

Hybrid-Modulation-Based Full-Speed Sensorless Control for Permanent Magnet Synchronous Motors

This article presents a full-speed sensorless control strategy for permanent magnet synchronous motors (PMSMs) based on a hybrid modulation strategy. The motor operating condition is divided into three ranges: low-speed range, transition range, and high-speed range. A novel two-or-three-vector switching (TTVS) method for rotor position demodulation based on an optimized asymmetric pulsewidth modulation (OAPWM) is proposed in the low-speed and transition regions. A Luenberger position observer based on the conventional symmetric space vector pulsewidth modulation is adopted to demodulate the rotor position in the high-speed region. Additionally, a switching strategy of two modulations and two position estimation observers is proposed to achieve a smooth speed and current transition. Compared with the previous work, the benefits of the TTVS method are to extend the modulation index of the OAPWM and to improve the position estimation accuracy. Finally, the feasibility of the proposed full-speed sensorless control is verified in a 500-W PMSM drive.

An Improved Full-Bridge Converter With a Five-Diode Rectifier for High Efficiency in Wide Voltage Range

This article presents an improved full-bridge converter with a five-diode rectifier. The primary side circuit is composed of a full bridge with two transformers and two split capacitors. On the secondary side, five diodes are employed in the rectifier stage. By using the asymmetrical pulse width modulation (PWM) signals, this converter can realize the zero-voltage switching (ZVS) of all switches and reduce the circulating current. The two transformers share the load power equally in whole load range. Compared with the other dual transformer isolated full-bridge converters, the transformers in the proposed converter are easy to optimize because of the load power equal sharing. Furthermore, the output filter inductance is reduced, which reduces the loss and volume. According to the loss analysis, the proposed converter has higher efficiency compared with some other dc-dc converters. The experimental results of a prototype with 300–400 V input voltage and 250 V/4 A output verify the performance of the proposed converter.