DC Bus Utilization Research Articles

A Nine-Level Midpoint-Clamped Inverter With Full DC-Bus Utilization and Suppressed Charging Current for PV Application

A Nine-Level Midpoint-Clamped Inverter With Full DC-Bus Utilization and Suppressed Charging Current for PV Application

Multilevel Inverter with Enhanced THD Value used in Grid Connected Applications

In this work, the relationships among pulse width modulation (PWM), sinusoidal pulse width modulation (SPWM), and space-vector pulse width modulation (SVPWM) for three-phase inverters will be analyzed to better comprehend their differences. detailed comparison of the three modulation schemes under study’s Total Harmonic Distortion (THD). High-power applications are increasingly concentrating on converter technology. This growing importance may be attributed to its improved output waveforms over the 3- carrier-based sinusoidal pulse width modulation (SPWM). To control and modulate multi-level inverters, many techniques are employed. These methods are categorized based on how frequently they switch. The ripple current rating, capacitance value, and voltage balance in the DC bus capacitors are all impacted by the pulse width modulation techniques. It is crucial to select the modulation method based on the current control requirements, as this determines the output voltage waveform’s harmonic content. SVPWM is gradually becoming more and more popular in industries because of its improved dc bus utilization and ease of digital realization. This work examines PWM, Sinusoidal, and SVPWM feeding a load connected to RL. Three different methodologies’ performances are compared as these methods are investigated through simulation with MATLAB/SIMULINK software.

Single Phase Sine-Wave Inverter with High DC Bus Utilization Using Natural Compensation

Abstract- In this paper, a new fixed frequency single phase sine-wave inverter topology - having high DC bus utilization - is presented. The main inverter uses six IGBT switches operating at low frequency in over-modulation mode to create a five-level voltage waveform; thus, having low switching losses with high DC bus utilization. A series active power filter (SAPF) using power MOSFETs helps to remove the major harmonic voltages. No isolated DC power supply is required across the SAPF that works on a simple feed-forward compensation (instead of feedback), based on the principle of natural compensation. The DC bus voltage needed for the SAPF is about half of the inverter, thus the SAPF has low switching loss even at the designated switching frequency. The switching frequency components of the SAPF remain in the output as they are not compensated, necessitating the use of a small filter at the output to attenuate them, to create a low total harmonic distortion output voltage with higher fundamental compared to the conventional schemes using Sinusoidal Pulse Width Modulation. The proposed inverter is suitable for fixed frequency backup power supply or other applications like renewable energy connection to the power grid.

Open-Winding Permanent Magnet Synchronous Generator for Renewable Energy—A Review

The open-winding permanent magnet synchronous machines (OW-PMSMs) have recently been gaining more attention because of their fault-tolerant capability and power quality comparable to a 3-level converter-driven system. This paper reviews the common configurations of OW-PMSM when used as a generator, highlighting its shortcomings and benefits. The OW-PMSM with a common DC bus was found to be a promising direct-drive generator solution for wind energy conversion (WEC) systems considering fault tolerance, DC bus utilization, and power quality when appropriate control algorithms are in place. The presence of the zero-sequence current is the key disadvantage of the common DC bus configuration. The review highlights the algorithms that have been proposed to suppress the zero-sequence current of the OW-PMSM under healthy and various fault conditions, especially the open-circuit fault of semiconductor switch. Shutting down remotely located wind turbines because of faults, until they can be repaired, may not make economic sense. The OW-PMSM can offer the opportunity, to run a WEC system even under fault conditions albeit with low output power. This paper will assess the literature gaps in the existing control techniques that prevent the extension via a comprehensive review.

Modulating Wave-Based Timing Calculation for a Multilevel 24-Sided Polygonal Voltage Space Vector Structure With Similar Triangles

This article proposes a multilevel 24-sided polygonal voltage space vector structure (VSVS), eliminating lower order harmonics up to 19th order and suppressing higher order harmonics in motor phase voltage throughout the modulation range. Unlike switched average vectors in literature, the proposed scheme generates real active vectors that have the advantage of less switching frequency operation. The proposed VSVS consists of two concentric polygons divided into similar triangles resulting in a simple modulation algorithm. Instantaneous error in phase voltage reduces due to the multilevel property of the proposed VSVS. The proposed scheme extends the dc bus utilization and linear range of operation. The proposed scheme is implemented on an open-end winding induction motor fed with primary and secondary inverters from either end. This article also presents a modulating wave-based method to compute nearest vector timings using sampled reference waves only. Unlike conventional methods, the proposed timing calculation method does not require trigonometric operations, sorting algorithms, and iterative search algorithms. Experimental verification of the proposed scheme is performed to validate the concept. Switching loss and Fourier analysis comparison with some existing schemes is also presented.

Investigative uses of overmodulation techniques in modular multilevel cascaded converter

Sinusoidal pulse width modulation (SPWM) is a method to generate the switching gate pulse of the converter. Overmodulation is a method where the modulation index exceeds the unity value and the system goes into the nonlinear region. To maintain the system in a linear region when operating in the overmodulation region, some techniques are developed. These techniques helped to operate the system in the linear range. Medium and high-power energy conversion systems mostly use a modular multilevel cascaded converter (MMCC), which has been an issue improving significantly in recent years. In this article, MMCC-based overmodulation techniques are compared with conventional PWM and analyzed on DC bus utilization (DBU), and total harmonic distortion (THD). MATLAB/Simulink digital platform used demonstrate overmodulation technique.

A Fault-Tolerant Inverter Circuit to Generate Thirteen-Level 24-Sided Voltage Space Vector Structure for Open-End Winding Induction Motor Drive

An inverter circuit to generate a 13-level 24-sided polygonal voltage space vector structure (VSVS) comprised of 288 real active vectors and a zero vector is proposed in this article. The proposed scheme eliminates lower order harmonics up to 19th order and suppresses higher order harmonics from motor phase voltage in the full modulation range. The 48-step operation of the proposed scheme highly improves phase voltage quality at full speed. The dc bus utilization of the proposed scheme is improved to 99.42% compared to 90.6% multilevel hexagonal VSVS. The proposed topology has inherent capacitor balancing in every sampling interval at any loading condition using pole voltage redundancies. Multilevel property of the proposed scheme reduces instantaneous error in phase voltage compared to two-level 24-sided polygonal VSVS. Generation of real active vectors reduces instantaneous error in phase voltage and reduces switching frequency compared to switched average techniques existing in the literature. Fault-tolerant feature of the proposed scheme improves the availability of the drive system. Experimental results are provided to validate the steady-state operation, capacitor balancing, transient performance, and fault-tolerant capability of the proposed scheme. The comparison of switching loss and harmonic performance of the proposed scheme is performed with existing topologies.

Modular Model-Predictive Control With Regulated Third-Harmonic Injection for Zero-Sequence Stabilized Inverter

A modular model-predictive control (MPC) method for a nonisolated three-phase <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$LCL$</tex-math></inline-formula> grid-connected converter is proposed with zero-sequence voltage control and regulated third-harmonic injection capabilities. The control method is proposed with the combination of a modified three-phase <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$LCL$</tex-math></inline-formula> converter topology to stabilize the common-mode voltage. The control mechanism consists of two layers: 1) the central-level control of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$dq$</tex-math></inline-formula> -sequence output current control cascaded with 2) the local-level control of zero-sequence voltage three-phase inductor current/capacitor voltage MPC. No grid-side inductance value is needed for the two-layer cascaded control structure, which both improves the dynamic performance from the inner MPC loop and avoids the MPC parametric error caused by the uncertainty of grid-side inductance. With the zero-sequence MPC, the common-mode voltage and leakage current can be attenuated without a bulky isolation transformer. A regulated third-harmonic injection (RTHI) method is designed based on the zero-sequence voltage control and the proposed modified converter topology to improve the dc bus utilization and avoid the overmodulation issue. Compared with the conventional third-harmonic injection methods, no extra harmonics are injected to the grid, and there is no need for a specialized grid total harmonic distortion optimization algorithm with the proposed zero-sequence-controlled RTHI. The stability and robustness of the proposed RTHI method are also improved with the zero-sequence MPC regulation. In addition, the modular concept of the local MPC module enables the extensibility for the power converter control with a flexible number of phases. The dynamic performance, leakage current attenuation, dc bus utilization, and grid-connection power quality of the proposed MPC method with RTHI have been validated experimentally.

Novel Three-Phase H10 Inverter Topology With Zero or Constant Common-Mode Voltage for Three-Phase Induction Motor Drive Applications

A traditional two-level 3-φ voltage source inverter topology operated with remote state pulsewidth modulation (RSPWM) can achieve constant common-mode voltage (CMV) without using additional passive components. However, apart from the poor harmonic performance, this topology suffers from the drawbacks of reduced dc bus utilization, increased semiconductor requirement, and higher losses. To address these issues, this letter presents a new H10 inverter topology for two-level three-phase inverter applications. The proposed topology can achieve constant CMV or zero CMV without requiring additional passive components. Compared with the RSPWM approach, the proposed H10 topology has 50% higher dc bus utilization, superior harmonic performance, reduced semiconductor requirement, and lower losses. A comparison of the proposed topology with the existing two-level solutions for CMV reduction reveals that the proposed H10 has the lowest total switch voltage rating and phase current total harmonic distortion (THD), considering zero CMV performance. Various experimental results obtained from a laboratory prototype are presented to validate the theoretical claims.

A Quick Dynamic Torque Control for an Induction-Machine-Based Traction Drive During Square-Wave Mode of Operation

In high power traction drives using induction motors, during operation above the base speed, it is generally preferred to drive the machine in the square-wave mode since it offers maximum DC-bus utilization and reduced switching loss. However, the conventional field oriented control method cannot control the drive effectively in square-wave mode since independent control of torque and flux is difficult to achieve due to stator voltage saturation. This paper proposes a new technique to control the drive in the square-wave mode where only one degree of freedom is available for control. In the square-wave mode, the proposed method controls the torque of the machine by directly varying the stator voltage angle with respect to the rotor flux axis. The flux of the machine is kept at a required value below the saturation limit by appropriate selection of the operating point. The proposed control strategy also offers good torque dynamics in the square wave operating mode. The control algorithm is experimentally verified on a 5.5 kW induction machine drive and the experimental results are presented.

Improved DC bus utilization of DVR based on repetitive controller with THIPWM technique

A DVR is being used to minimize the power quality problem. The SPWM method has been popularly used in DVR but use of the DC bus is restricted in SPWM, which is critical due to economical as well as power packaging density improvements. The proposed THIPWM scheme has been deduced from SPWM by adding one-sixth of the third harmonic signal in the fundamental signal. Repetitive Controller (RC) with Third Harmonic Injection (THI) technique is applied to achieve better dc-link utilization for medium-low voltage distribution. As an outcome, it's indeed evident that 15% reflects an increment in dc bus utilization as well as the potential to create high voltage AC. The control system comprises a feed-forward as well as feedback run to enhance the transient response & confirm the steady zero error. THD results improve when the THIPWM methodology is being used. PSCAD software is being used for the computation, which generated accurate findings for the THIPWM and Repetitive Control systems approach.

Optimal third harmonic injection based nearest level control of large‐scale solar photovoltaic multilevel converter

This paper presents a new control approach with an optimal third harmonic injection-based nearest level modulation (OTHI-NLM) technique for a large-scale solar photovoltaic (SPV) system. This system uses a single-source multilevel converter to feed solar power into the grid. The merits of the optimal third harmonic injection (OTHI) and nearest level modulation (NLM) are considered for switching the SPV converter. A unique analysis to have an adaptive optimal injection with varying solar irradiance is conducted and compared with the well-known carrier-based high-frequency switching technique. The variations of harmonics for OTHI-NLM, an optimal third harmonic pulse width modulation (OTHI-PWM), and a constant third harmonic injection method are analysed at different irradiance levels. This optimal injection provides benefits such as enhanced DC bus utilization (DBU), better harmonics performance at different solar irradiance levels. The detailed methodology of the OTHI algorithm, nearest level modulation (NLM) technique with an optimal quotient calculation, and an instantaneous optimal third harmonic injection (THI) in closed-loop are presented. The comparative analysis shows the effectiveness of the SPV grid-tied structure over well-known ones. The power quality of the renewable energy system is investigated in dynamic solar irradiations. Moreover, simulation results are presented and validated in a real-time test bench.

Extending DC Bus Utilization for Induction Motors with Stator Flux Oriented Direct Torque Control

This paper presents a method to extend the DC bus utilization on an induction motor (IM) by using a combination of Space-Vector Modulated Direct Torque Control (DTC–SVM) and conventional DTC. The scheme proposed in this paper exploits the advantages of both control methods. During the linear region, it allows for a low torque ripple and low current harmonic distortion (THD). During the overmodulation region, it allows for the fastest torque response up to the six-step operation region. In both regions, there is complete independence of the motor parameters. The paper describes a way to provide a smooth transition between the two control schemes. Non-linearities affect the stator flux angle estimation, which leads to the inability to decouple torque and flux. To overcome this problem, a novel PI-based control scheme as well as a simplification on the decoupling terms’ calculation are proposed. Simulation and experimental results are presented to verify the feasibility of the proposed method.

Space Vector Techniques for a Binary-Cascaded Multilevel Inverter Operating Under Reduced Common-Mode Voltage With Reduced Commutations

This paper presents a novel space vector pulse width modulation (SVPWM) for a three-phase binary cascaded multilevel inverter. The SVPWM could become impractical in multilevel inverters (MLIs) because of its increasing complexity with a larger number of levels. The <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">gh</i> coordinate system can ease the digital implementation, but to generate the inverter's <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">abc</i> states from the nearest three vectors (NTVs), iterative computations are required every sampling instant. This paper proposes further reduction of computations by directly generating the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">abc</i> state with minimum common-mode voltage (CMV) from a <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">gh</i> vector. Subsequently, only one vector among the NTVs is required for implementing the proposed SVPWM. The reduced CMV profile within the NTVs further permits the reduction of commutations by clamping one phase during a sampling period. The presented technique exhibits full dc bus utilization capability and can be implemented in the binary cascaded MLI (BCMLI) and further applied to any <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">M</i> -level MLI. Also, if <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">M</i> is considerably large or if switching losses and electromagnetic interference emissions must be minimized, nearest vector modulation with reduced CMV along with line-frequency operation of high-voltage cells can be implemented to reduce the switching losses. Experiment results of a BCMLI is presented to verify the effectiveness of the proposed technique.

Common-Mode Voltage Reduction Algorithm for Photovoltaic Grid-Connected Inverters with Virtual-Vector Model Predictive Control

Model predictive control (MPC) has been proven to offer excellent model-based, highly dynamic control performance in grid converters. The increasingly higher power capacity of a PV inverter has led to the industrial preference of adopting higher DC voltage design at the PV array (e.g., 750–1500 V). With high array voltage, a single stage inverter offers advantages of low component count, simpler topology, and requiring less control tuning effort. However, it is typically entailed with the issue of high common-mode voltage (CMV). This work proposes a virtual-vector model predictive control method equipped with an improved common-mode reduction (CMR) space vector pulse width modulation (SVPWM). The modulation technique essentially subdivides the hexagonal voltage vector space into 18 sub-sectors, that can be split into two groups with different CMV properties. The proposal indirectly increases the DC-bus utilization and extends the overall modulation region with improved CMV. The comparison with the virtual-vector MPC scheme equipped with the conventional SVPWM suggests that the proposed technique can effectively suppress 33.33% of the CMV, and reduce the CMV toggling frequency per fundamental cycle from 6 to either 0 or 2 (depending on which sub-sector group). It is believed that the proposed control technique can help to improve the performance of photovoltaic single-stage inverters.

A Transformerless 1-, 5-Level Half-Bridge PV Inverter Configuration Based on Switched-Capacitor Technique

Leakage current is a serious problem in the transformerless solar PV inverter configurations. The flow of leakage current is mainly due to the high-frequency oscillations in the voltage across PV parasitic capacitance (v <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CPV</sub> ). Half-bridge (HB) and common ground type inverter topologies are highly suitable for eliminating these oscillations as these configurations allow direct electrical connection between the source and the load/grid ground. However, they suffer from either poor dc-bus utilization or asymmetric operation leading to dc-offset in the output voltage. In this article, a novel 1-φ, 5-level inverter is proposed, which employs a HB structure to eliminate voltage oscillations from v <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CPV</sub> without compromising with the dc-bus utilization or symmetric operation. This is achieved by integrating a switched capacitor network with the HB structure. All the necessary analysis and design procedures are included to support the various claims. The claims are further validated using MATLAB simulations and experiments on a laboratory prototype. The proposed topology is compared with the various existing topologies of similar nature (like 5-level output voltage, common ground or HB type configuration and 1-φ) to prove its superiority.

Simulation and experimental verification of modified sinusoidal pulse width modulation technique for torque ripple attenuation in Brushless DC motor drive

The Brushless DC motor when operated with120° conduction mode with quasi square wave current in phase with trapezoid back emf leads to finite torque ripple in the commutation region with only two phases conducting at any time. To overcome this, the BLDC motor phases can be supplied with sinusoidal currents which reduce the voltage required to deal with the phase inductance instead of quasi square currents as the change in currents is smoother because of its shape. The proposed technique aims to develop closed-loop speed control of BLDC motor using Modified Sinusoidal Pulse Width modulation (MSPWM) technique by providing sinusoidal stator currents in synchronism with the trapezoid back emf to reduce the commutation torque ripple with improved dynamic performance. The closed-loop control is accomplished by providing a PI controller for a speed control loop. Hall sensors along with shaft encoder are used for detecting the accurate rotor position and speed. This technique provides a higher DC bus utilization as compared to conventional six-step control with torque ripple reduced up to 50%. To justify it, simulation is performed using MATLAB®/SIMULINK at different speed and load. The experimental verification is carried on a prototype using the STM32F407VG microcontroller with Cortex-M4 32 bit ARM controller. The experimental results validates the closed-loop speed control operation of BLDC motor using MSPWM technique.

Novel approach for SVPWM of two-level inverter fed induction motor drive

&lt;p class="Abstract"&gt;Due to their better DC bus utilization and easier digital realization, Space Vector Pulse Width Modulation (SVPWM) scheme is the most widely used PWM scheme. Also two level inverter is the traditional frequency converter because it has fewer components and is lower complex to control, but on the other hand it generates higher harmonic distortion. This paper presents the realization of novel SVPWM approaches applied to the three phase induction motor drives. Specifically various schemes are based on using more combinations of step operation in each cycle to approximate the reference vector, such as 24 and 48 step operations in each cycle. The basic principle of conventional SVPWM with different modulation index M is presented. The switching sequences of new approaches are described. The modulation signals waveforms, DC bus voltage utilization, De-rated motor torque, standard error of average torque, voltage and current harmonic of new approaches are analyzed by the MATLAB/SIMULINK software. The results confirms that 48 step SVPWM approach is the best compared to other approaches.&lt;/p&gt;

A Bus Clamping PWM-Based Improved Control of Grid Tied PV Inverter with LCL Filter Under Varying Grid Frequency Condition

ABSTRACT This paper presents a modified Synchronous Reference Frame Phase locked loop (MSRFPLL) for better synchronizing the output of the inverter with the grid. The proposed PLL is able to track the changes in the grid frequency in a faster way as compared to the conventional synchronous reference frame PLL (SRF-PLL). In order to switch the inverter, an advanced bus clamping based space vector PWM is being used which is novel for photovoltaic application. This PWM gives better DC bus utilization as compared to the conventional Sine PWM technique. To keep the THD within a permissible limit of 5% in accordance with the IEEE-519 & 1547 standard LCL filter with passive damping is implemented. DSPACE-1104 DAC card has been used for better interfacing of the experimental set up with MATLAB. The overall system is also being simulated in MATLAB/Simulink environment and the simulated results have been validated with the experimental results.

Implementation of space vector modulation for two level Three-phase inverter using dSPACE DS1104

With increasing research and advancement in solid-state power electronic devices and microprocessors, various inverter control techniques employing Pulse Width Modulation (PWM) are becoming popular especially in AC motor drive applications. The most commonly used techniques are Sinusoidal PWM (SPWM) and Space Vector modulation PWM (SVPWM). SVPWM is considered to be superior to the SPWM because of better DC bus utilization. In this paper, a real-time digital implementation of SVPWM algorithm for three-phase two level inverter using dSPACE DS1104. The results obtained from the experimentation are closer to that of simulation, which confirms the validity of the implemented algorithm.