Staircase Waveform Research Articles

Self-Voltage Balanced Switched-Capacitor Seven-Level Inverter for Asymmetrical Solar PV Source Applications

In this paper, a novel structure of self-voltage balanced switched-capacitor-based seven-level inverter (SVB-SCSLI) is proposed for asymmetrical input energy source applications. SVB-SCSLI develops a seven-level staircase waveform with a minimum number of semiconductor devices compared to existing multilevel inverters (MLIs). The proposed converter is more suitable for the solar PV system where unequal DC voltage sources are available. The SVB-SCSLI also resolves the main difficulty of connecting many inverters in parallel to achieve staircase voltage. Besides, it attains voltage balancing capability at DC-link by holding constant capacitor voltage at every cycle. The detailed loss and steady-state analysis of the SVB-SCSLI are examined. Furthermore, the proposed converter’s efficiency improves with better power quality than other topologies reported in the literature. Finally, a prototype is fabricated, and experimental results are presented to validate the feasibility of SVB-SCSLI.

Intensity modulation of UV light in gas sensor array to discriminate several analytes at room temperature

AbstractIn this study, a gas sensor array along with intensity modulation of UV light was utilized to discriminate several gases at room temperature. The sensor array was consisted of two interdigitated microelectrodes and TiO2 nanofibres were electrospun on them and calcined at 540°C for 90 min. One of these sensors was coated by 2‐nm Pt using the DC sputtering method and the other one remained uncoated. In each experiment, the sensor array was located at a distance of 30 mm from a 365‐nm UV LED. For intensity modulation of UV light, a staircase waveform voltage was applied to the UV LED. The voltage was included of three voltage steps and the measured powers at a distance of 30 mm from the UV‐LED were about 450, 560, and 680 µW/cm2, respectively. Analytes including acetone, ethanol, methanol, 2‐propanol, and carbon monoxide (CO) at various concentrations ranging from 50 to 500 ppm were examined. Three‐dimensional Principal Component Analysis mapping was successfully used for the segregation of all examined gases. The examinations revealed that using sensor array along with intensity modulation of UV light is an effective method for discrimination of several analytes at room temperature.

Development of an Enhanced Selective Harmonic Elimination for a Single-Phase Multilevel Inverter with Staircase Modulation

A low device switching frequency is recommended for the operation of multilevel inverters (MLIs) to achieve reduced switching losses. Selective harmonic elimination (SHE) and total harmonic distortion (THD) minimization are the two primary switching angle estimation methodologies for low-frequency modulation control. In this regard, a new generalized condition has been developed in this paper for the SHE technique. This original condition will give an output voltage with improved THD in comparison to the conventional SHE technique, while achieving its primary objective of eliminating the specific harmonic content from the output voltage. The proposed condition has been formulated by estimating the error associated with the staircase waveform and the desired sinusoidal output at the fundamental frequency. An infinite harmonic count has been considered for the evaluation of the quality of output, to obtain an accurate THD value without any underestimation. The proposed technique is analyzed, and its critical features are studied in Simulink. The effectiveness of the present work has been also validated by the experimental results.

Partial Discharge Behavior of Typical Defects in Power Equipment Under Multilevel Staircase Voltage

With the widespread application of power electronic switching technology, power equipment is facing new electrical stresses brought about by multilevel staircase voltages during testing and operation. Therefore, the partial discharge (PD) behavior of five typical defects in power equipment under the staircase waveform needs to be investigated. This article mainly analyses the phase-resolved PD (PRPD) pattern and pulse repetition rate (PRR) of five typical defects under sinusoidal voltage and multilevel staircase voltage with different number of levels. Also, the PD behavior under staircase voltage with different step responses are investigated. By analyzing the reasons behind the PD behavior between different cases, the PD characteristics and the transformation of PRPD patterns under different staircase voltages are obtained. Moreover, this research finds that the sensitivity of different defects to the staircase voltage is different. These results provide experimental and theoretical support for the testing and diagnosis of PD under new electrical stress present in the future flexible electric grid.

Adaptive Single Carrier Modulation scheme based MLI supported TDVC for Voltage Quality enhancement

Abstract In this article, An Adaptive Single Carrier Modulation (ASCM) scheme based Multilevel Inverter (MLI) is proposed for the Transformerless Dynamic Voltage Compensator (ASCM-MLITDVC) to enhance the load Voltage Quality (VQ). The enhancement of VQ includes voltage sag, swell, unbalance and reducing Total Harmonic Distortion (THD). The Pulse Generation Unit (PGU) require more Carrier Waves (CW) for higher levels of MLI with respect to the number of switches used. This made the PGU complex, hence a carrier wave modulation scheme is proposed which can use it for n number of levels. The Position of CW is altered automatically with respect to the amplitude of Reference Staircase Waveform (RSW). The RSW is created by utilizing the Half Height Method and optimized NLM scheme which makes the least possible output THD is achieved. This scheme is implemented utilizing a real-time simulator OP4500. The results are obtained by conducting Power Hardware in Loop (P-HIL) test method to prove ASCM-MLITDVC can enhance load VQ with reduced THD.

A Dumbbell Type (D-Type) multilevel inverter based on switched capacitor concept

ABSTRACT In this paper, a new single-phase seven level inverter with reduced device count is introduced. The structure can boost the input voltage by synthesising the capacitors’ voltages in predetermined current paths. A single DC voltage source is utilised to generate the output AC staircase waveform, which is facilitated via Nearest Level Control. Self-voltage balancing ability, less number of semiconductor devices, high efficiency and control simplicity are the most significant inherent attributes of the proposed circuit. It is also noticeable that in this configuration neither bulky transformer/inductor nor filters are applied. Power loss calculation and required capacitance of the proposed inverter are investigated and theoretical efficiency of 93.31% was reached. Moreover, the proposed converter operates under various load conditions with lower Total Harmonic Distortion compared to recent topologies. Ultimately, operating principles of the proposed D-Type seven-level Inverter and simulation results in MATLAB SIMULINK environment are validated by experimental ones obtained from the laboratory prototype.

Implementation and Analysis of a Novel Switched-Boost Common-Ground Five-Level Inverter Modulated With Model Predictive Control Strategy

Common-ground (CG) string inverters with a transformerless (TL) circuit configuration have been broadly popular in grid-connected photovoltaic (PV) applications. The most important feature of a PV string TL inverter with a CG circuit connection is the elimination of leakage current concerns. Having the voltage boosting property within a single power processing stage can also be propitious to further facilitate the integration of low-scale PV string panels with higher efficiency. An efficient topology of such converters is presented in this study, which is able to produce a five-level stair-case output voltage waveform using an integrated switched-boost (SB) cell with only seven power switches. The proposed SB common grounded five-level (SBCG5L)-TL inverter can also be extended for the three-phase CG-based applications with the contribution of the same integrated SB cell. As for the single-phase configuration, it needs two dc-link capacitors and two power diodes along with two small inductors. A quasi-soft charging operation of the involved capacitors is also achieved. To control the injected current under the grid-connected condition, a single-step model predictive control (MPC) technique with a fixed switching frequency operation has also been presented. The proposed circuit description, the theoretical analysis of the applied MPC principles, and the comparative study with associated experimental results are also presented to ascertain the correctness and feasibility of the proposed SBCG5L-TL inverter.

A New 13-Level Switched-Capacitor Inverter with Reduced Device Count

Abstract This paper proposed a new voltage-boosting 13-level switched-capacitor (SC) cost-effective inverter. The proposed topology comprises fourteen transistors, three capacitors and a single DC source to produce a 13-level staircase waveform. The capacitor voltage balancing problem is inherently solved by the series/parallel technique. Structural description, working principle, calculation of optimum values of capacitance and modulation scheme are briefly described. The comparative analyses with the existing SC multilevel inverter (MLI) in terms of voltage gain, blocking voltage, total standing voltage (TSV), component per level factor and cost function illustrate the merits of the proposed topology. Further, simulation and experimental results at different loading conditions verify the feasibility of the proposed topology.

Circuit Configuration and Modulation of a Seven-Level Switched-Capacitor Inverter

In this article, a step-up seven-level inverter supplied by a single dc source suitable for renewable energy application is presented. Forming the desired output is realized by charging capacitors and synthesizing them based on a switched-capacitor concept. This structure is praised for the ability of sensorless voltage balancing of the capacitors, reducing control complexity to produce a bipolar staircase waveform. It also benefits from regenerative performance, avoiding unwanted capacitors overvoltage. A phase disposition pulsewidth modulation (PD-PWM) technique is utilized to control the circuit operation. Furthermore, a comparison with other recent topologies reveals that losses, number of semiconductor devices, and gate driver circuits are reduced. Theoretical analysis is verified through a laboratory prototype implementation. Experimental results under various types of loads approve the performance of the proposed inverter and validity of the design. Finally, maximum experimental efficiency of 94.3% (115 V, 250 W load) was reached.

A Novel High Step-Up Switched-Capacitor Multilevel Inverter With Self-Voltage Balancing

This article presents a novel high step-up multilevel inverter (MLI) with a single dc source based on switched-capacitor modules in which it is suitable for the renewable energy applications with low-voltage dc source. The proposed topology has the ability of the voltage self-balancing for the capacitors without any external or closed-loop circuits. Another merit of the proposed structure is the production of bipolar staircase waveform without any end-side full-bridge in which it reduces the voltage stress on components remarkably. The circuit topology and its operation principle, capacitance calculations and comparison of the proposed circuit with other well-known single-source MLIs are discussed in detail. Finally, a 21-level prototype of the proposed inverter with 32 V input voltage and high gain 10 by using four modules was evaluated by both simulation and experimental tests.

Three-dimensional voltammetry: Use of chronoamperometric E-t-i data to achieve second-order advantage

This work studied the use of three-dimensional voltammetry, particularly potential-time-current (E-t-i) data, on the development of electroanalytical methods. E-t-i data was obtained by taking chronoamperograms at potentials applied as pulses on a staircase waveform. By using this three-way kind of data and appropriate calibration algorithms, the possibility of achieving the second-order advantage was evaluated in the determination of ferrocyanide in the presence of the uncalibrated interference hydroquinone as a model system. The determination of acetaminophen in urine samples, where ascorbic acid and uric acid play the major roles as interferents was also studied. Parallel factor analysis (PARAFAC) and multivariate curve resolution alternating least-squares (MCR-ALS) were the algorithms employed in this work. Both algorithms successfully achieved the second-order advantage by correctly predicting the concentrations of the validation synthetic samples. Excellent predictions were obtained in the direct analysis of acetaminophen-spiked urine samples by E-t-i data and MCR-ALS.

A New Topology of Switched-Capacitor Multilevel Inverter With Eliminating Leakage Current

This paper proposes a new topology of the switched-capacitor multilevel inverter (SCMLI) for photovoltaics system, which can eliminate the leakage current. In the proposed topology, the capacitors are employed as a virtual DC power supply to boost the input voltage. Here, all capacitors are charging equal to DC source, thus, just one DC source is needed to achieve the staircase waveform. In this structure in order to make the negative levels, the capacitors are connected to the output in reverse polarity. Thus, the H-bridge circuit which is used in traditional SCMLI to build zero and negative voltage levels and leads a variable common mode voltage is removed. Due to the direct connection of the neutral terminal of the grid to the negative polarity of the PV; then this topology can eliminate the leakage current. In addition, the topology has an excellent ability to path the reverse current as well as an acceptable output waveform spectrum. The operating states of all components and loss calculations are analyzed and formulated accurately as well as simulated by using MATLAB-SIMULINK software. To confirm the performance of the proposed topology; a 500 W prototype is built and experimental results are presented.

Logic pattern-based low-frequency pulse generation technique for modified multilevel DC-link inverters

The multilevel inverter (MLI) targets on generating a low THD output, which reduces the filter size requirement. This is achieved at the expense of increased switches, which increases the control complexity. Ongoing efforts are being made by researchers to reduce the switch count of MLIs. Many reduced switch count (RSC) topologies of MLIs have been reported in the literature along with various PWM techniques for providing the gate pulses for these topologies. The modified multilevel DC-link inverter (MMLDCLI) is one of the RSC MLI topologies, where only six switches are used to generate a seven level output. The MMLDCLI consists of series connected cells to generate a unipolar staircase waveform and a simple H-bridge acting as a polarity generator. Two unequal dc sources and six switches constitute the MMLDCLI generating a seven level output. This paper proposes a versatile gate pulse generation technique for the MMLDCLI, which enables a wide range of converter operation. This technique provides a smooth changeover in the number of output levels (5 levels/7 levels) resulting in a low THD in the output voltage. The viability and impact of the proposed technique on a MMLDCLI are analyzed through simulation and they are validated through a laboratory prototype.

Pure Sinusoidal Output Single-Phase Current-Source Inverter with Minimized Switching Losses and Reduced Output Filter Size

This paper proposes a novel single-phase current-source inverter that generates a pure sinusoidal waveform with minimized switching losses and using a small-size output filter capacitor. The proposed method is investigated by incorporating a conventional multilevel current-source inverter with a linear amplifier. The conventional multilevel technique uses fundamental switching frequency instead of using high-switching frequency modulation for the H-bridge circuit. The linear amplifier such as class-A or class-D types has a function to reform the staircase waveform generated by the multilevel inverter into a pure sinusoidal by using superimposition technique. As a result, pure sinusoidal output current is generated with a small ripple and the system only requires a small output filter capacitor for smoothing the waveform. Based on the simulation and experimental results, the proposed system presents not only the optimal configuration, but also an option as to whether to obtain excellent power efficiency or very low output harmonic. Implications of the results and future research directions are also presented.

Design of Combinational Logic Circuit Prober

Abstract The objective of this paper is to design and implement a logic circuit prober to display truth tables of a three input combinational logic circuit. The truth table is to be as “1” and “0” on an ordinary 60 MHz oscilloscope. This paper meets this objective by using Lissajous Patterns to plot a “0” or a “1” on the oscilloscope screen. To plot a “0” on the oscilloscope screen, two sinusoidal signals in quadrature are supplied to the two inputs of the oscilloscope with the scope set to X-Y mode. To plot a “1” on the oscilloscope, only the signal to the Y input is allowed to reach the oscilloscope screen. To display all the 32 patterns required to obtain a three input truth table, two staircase waveforms are employed. The staircase waveforms, one eight-step and the other four-step, are added to the two sinusoidal signals to shift the patterns along the X and Y directions to produce all the 32 patterns.

Design, analysis and implementation of a generalised topology for multilevel inverters with reduced circuit devices

This study proposes a multilevel inverter with optimised structure from switching device number point of view. Configuration of the presented multilevel inverter is modular and extendable. Three different methods are introduced to determine the magnitude of DC voltage sources. Characteristics of inverter topology based on suggested methods are given and compared with each other. Also, the proposed multilevel inverter is compared with some similar topologies in terms of controlled switches, driver circuits, DC voltage sources and total blocking voltage to verify its advantages and probable disadvantages where the results show the superiority of the proposed topology in the comparison items. Selective harmonic elimination pulse width modulation technique is applied to achieve output voltage with high quality. Finally, a laboratory prototype of the proposed multilevel inverter is implemented and then, the experimental and simulation results are derived to validate the inverter capability in generating staircase waveforms.

A single-source switched-capacitor multilevel inverter for magnetic coupling wireless power transfer systems

This paper proposes a single-source switched-capacitor multilevel inverter for magnetic coupling wireless power transfer (MC-WPT) systems. The proposed inverter consists of one DC source, two half bridges, and novel extensible I-type switched-capacitor modules. It can generate a staircase waveform voltage with higher amplitude and lower total harmonic distortion, and the voltage stress of all power switches is equal to the DC input voltage, so high output power can be obtained by power switches with low voltage capacity. Compared with the existing multilevel inverters, the proposed inverter requires a less number of power switches and energy storage components to generate the same number of voltage levels, which means better voltage boost ability. Moreover, it can achieve self-voltage balancing of switched capacitors easily without balancing circuit or control algorithm. The topology, operating principle, output voltage, and self-voltage balancing ability of the proposed inverter are analyzed, and the comparison with the existing multilevel inverters is presented. The modulation strategy and value of the switched capacitor are designed, and the soft switching state and power loss are analyzed and calculated. Finally, an experimental setup of a 1-kW MC-WPT system is implemented to verify the correctness of the theoretical analysis and the feasibility and superiority of the proposed inverter.

A New Topology on Twenty one level Inverter with Reduced Number of Switches

The Multilevel inverters are known for their high power capability and reliability. They produce the output in the form of staircase waveform. If the number of level increases then almost perfect sine wave can be attained at the output. The increase in number of levels improves the power quality but it also increases the complexity in control and cost, which will increase the switching losses also. Hence there is a need for research in the multilevel inverter topology to have reduced number of switches for increased levels than the conventional and pre-proposed topologies. The purpose of this paper is to design the new topology on multilevel inverter with reduced switching devices

A New Topology on Twenty one level Inverter with Reduced Number of Switches

The Multilevel inverters are known for their high power capability and reliability. They produce the output in the form of staircase waveform. If the number of level increases then almost perfect sine wave can be attained at the output. The increase in number of levels improves the power quality but it also increases the complexity in control and cost, which will increase the switching losses also. Hence there is a need for research in the multilevel inverter topology to have reduced number of switches for increased levels than the conventional and pre-proposed topologies. The purpose of this paper is to design the new topology on multilevel inverter with reduced switching devices

A cascaded H-bridge multilevel inverter with photovoltaic MPPT control

This article presents the five levels H-Bridge cascaded multilevel inverter with photovoltaic MPPT control. The power source is composed of photovoltaic panels used as DC inputs for the cascaded H-Bridge Multilevel Inverter. The present work aims to present a control strategy to produce the best output quality possible. The algorithm P&O extract from the panels the maximum power while the supervision system tends to control the DC levels in the CHMLI inputs. Each panel possesses its own MPPT module and the cascaded H-Bridge Multi-Level Inverter uses the modules as entries to produce a staircase waveform output. A simulation using matlab/simulink is realized to verify the system performance.