Distortion Of Output Waveform Research Articles

Harmonic Interaction Analysis of Inverters Based on Harmonic State-Space Model Considering Dead-Zone Effect

In the context of increasing device switching frequencies year by year, non-ideal factors such as dead-zone effects in inverters not only cause output waveform distortion, but also generate harmonics that make the interaction between inverters and power grids more complex. In order to accurately describe and analyze this phenomenon and establish a more practical grid-connected inverter model, this paper proposes and establishes a three-phase LCL grid-connected inverter harmonic state space model that considers dead-zone effects. By incorporating dead-zone effects into the modeling process, the system transfer function matrix is derived to quantify the harmonic interaction coefficient between the inverter and the power grid, and the influence mechanism of dead-zone effects on the harmonic interaction process at high switching frequencies is analyzed in depth. The necessity of considering dead-zone effects is illustrated through simulation, and the effectiveness and accuracy of the inverter HSS model considering the effects of dead-zone effects are verified through experiments.

Output Waveform Distortion Suppression Method of Asymmetric Sine Wave Inverter Based on Online Identification and Linearization of System Transmission Characteristics

Limited by the switching frequency of an insulated gate bipolar transistor (IGBT), the system bandwidth of high-power inverters is low. If the amplitude and phase changes of each harmonic from the reference signal to the output waveform are defined as transmission characteristics, it can be concluded that the limited bandwidth will result in nonlinear system transmission characteristics. This results in the amplitude and phase distortion of each harmonic of the asymmetric sine wave, which in turn leads to severe distortion of the output waveform. Therefore, this article proposes a method to linearize transmission characteristics. This method effectively offsets the nonlinear effect of transmission characteristics, which is caused by the limited bandwidth, by causing distortions with respect to each harmonic in the reference signal, thereby suppressing the distortion of the output waveform. In addition, an online identification method of transmission characteristics based on a state observer is proposed to achieve the online linearization of system transmission characteristics. This method does not rely on closed-loop system control, has no stability problems, and can be used for a variety of control methods. Simulation and experiments verify the effectiveness of this method.

A Novel Dead-Time Elimination Method for Voltage Source Multilevel Converters

Voltage source multilevel converters (MLCs) are widely applied in recent years in a wide range of industrial applications. However, time delay inserted in switching signals to prevent short through can cause the dead-time effects, including output waveform distortion and voltage drop. In many kinds of MLCs, the freewheeling paths during dead time can also produce unexpected output voltage levels, which can cross a few consecutive output levels, introducing large <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dv</i> / <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dt</i> . Typical examples of those MLCs are 5L-active neutral-point-clamped, 7L-hybrid-clamped, 4L-nested neutral-point-clamped (NNPC) converter, etc. To solve this problem, a generic dead-time elimination (DTE) method is proposed. This method splits the complementary switches and replaces them with controllable switches coupled with uncontrollable diodes, decomposing the phase-leg of the converter into two basic switching cells, thus obviating the need for dead time. To address the zero-current clamping effect inherent to the DTE method, a second-order generalized integrator frequency-locked loop based current detector is also developed. The proposed DTE method is suitable for various MLCs. It cannot only effectively eliminate the unexpected levels, but also significantly reduce the output distortion and regains the output rms value. An application example of 4L-NNPC converter is given. The effectiveness of the proposed method is verified by both simulation and experiment.

Low-Frequency-Drop of Electroabsorption Modulated Lasers and the Improvement With Partially Corrugated Grating Based DFB Lasers

Electroabsorption modulated lasers (EMLs) is sensitive to the residual facet reflection (RFR), which can cause a low-frequency drop (LFD) in the modulation response. The LFD may result in output waveform distortion, especially for high-data rate and multi-level modulation. We verify by simulation and experiments that the effect of LFD on the EML performance and propose to use LFD as one of the key performance indices for qualifying EMLs in high-speed optical transceivers. LFD can be suppressed by incorporating partial-corrugated-grating (PCG) in the laser section. With PCG-DFB structure, the EMLs can maintain high single-mode yield (SMY) and an excellent quality factor even with a strong modulator reflection from EAM section. This provides the robustness in applying the PCG-DFB to achieve a flat intensity modulation response or to enhance the output waveform under large signal modulation. By designing the PCG-EML to have about 60% of grating region, it can reach >80% of SMY and improve the average Q-value from the reduced LFD in the modulation response. The PCG-EML with reduced LFD can enhance the eye-opening through reduced waveform undershoot and overshoot for transmitting 56-Gbaud/s or beyond PAM-4 signals.

Design of sliding mode adaptive DC-DC converter based on function approximation

The output power and voltage of solar photovoltaic power generation are easily affected by climate and load changes, so it is necessary to use DC-DC converter at its output to provide stable output voltage. DC-DC converter is a time-varying nonlinear system. When the output load of the converter varies widely, the output waveform distortion and dynamic response speed of the DC-DC converter will slow down. The essence of sliding mode control is a kind of switch control method, and the DC-DC converter needs the switch of switch tube to realize voltage regulation. In this paper, a sliding mode adaptive control strategy based on orthogonal polynomial function approximation is proposed, and Laguerre polynomial is selected as the basis function of DC-DC transformation system. The output voltage error and its first derivative of the system are taken as the input of the network, and the output of the network is taken as the approximation term of the system uncertainty, and the network weight is updated according to the adaptive law. Through simulation and comparison, the adaptive controller designed in this paper is superior to the ordinary sliding mode controller in reducing chattering, adaptive load change and reducing the influence of system interference.

Research on Harmonic elimination Feedback Control Technology of Sine Wave Inverter Based on Instantaneous Reactive Power Theory

Aiming at more and more occasions where the sine wave output inverter is used for power supply of a non-linear load, the sine wave output waveform distortion of the inverter caused by the non-linear load is serious. The feedback control strategy of sine wave inverter based on instantaneous reactive power is proposed. Through the fundamental wave instantaneous tracking feedback control based on the instantaneous reactive power theory and the detection and feedback control of the output harmonic signal, this paper realizes the ability of the inverter to maintain the output waveform with high sine degree and low distortion under various load conditions, it guarantees the error-free control of the fundamental wave and has a good dynamic response performance. This solution has the advantages of easy controller stability design and good implementability. The simulation circuit is built by Matlab / Smiulink, and the correctness of the theory is verified by the simulation results.

Online Feedback Dead Time Compensation Strategy for Three-Level T-Type Inverters

The insertion of dead time will lead to the distortion of output waveforms, which seriously affects the characteristics of the ac induction motor control system. In order to reduce the output distortion of three-level T-type inverters caused by dead time insertion, an online feedback dead time compensation method is developed. In this method, the compensation time is obtained and further corrected by the online feedback of duty cycle. Meanwhile, current polarity judgment is accurately realized by sampling the neutral point (NP) potential and three-phase output terminal voltage potentials. In addition, in this article, we take the NP potential fluctuation into account to approximate the true situation. The developed method can be applied to both open-loop and closed-loop motor drive systems. To verify the effectiveness of the method, essential simulation and experiments are carried out. Compared with the traditional methods, the developed method can prominently reduce the output waveform distortion. Simulation results emphasize that the proposed scheme can significantly improve the performance of three-level inverters, and the identical conclusion is obtained on 210 V/2.24 kW motor platform.

The wide range of output frequency regulation method for the inverter using the combination of PWM and DDS

PurposeThe specific modulation methods are used to control different kind of single-phase, as well as three-phase, inverters to ensure flexibility and high quality of the output waveform. This paper aims to present a combination of two classical methods, namely, pulse width modulation method and direct digital synthesis modulation method.Design/methodology/approachThe total harmonic distortion of output waveforms of single-phase inverter based on elaborated modulation method has been determined by means of fast Fourier transform analysis. Tests have been carried out by using standard low-frequency application and also a wireless resonant energy link system.FindingsApplying appropriate timer parameters of microcontroller enables to obtain a waveform for given output parameters (amplitude, frequency, frequency modulation index, etc.). The only limitation is the computing power of a microcontroller.Originality/valueThe elaborated method can be successfully used in both low- and high-frequency application ensuring high level of output waveform quality. Additional signal generators and the control of amplitude modulation ratio are no longer indispensable, what simplify immensely a control system.

Efficiency‐optimised modulation technique of three‐level NPC inverter

The three-level NPC inverter has many advantages, such as the characteristics of high output power, low device stress, and low harmonic distortion of output waveform. It is widely used in the fields of high-voltage conversion and reactive power compensation. As the most commonly used multi-level inverter, three-level NPC inverter has its own disadvantage which is the NP potential fluctuations. It may lead to poor output performance even damage to the devices. Therefore, the problem of NP potential fluctuation of three-level NPC inverter has been the hotspot of its research. This paper presents an efficiency-optimised dual modulation wave carrier-based PWM (DMWPWM) strategy of three-level NPC inverter. First, the basic principle of traditional DMWPWM is analysed, and the deficiency of traditional DMWPWM modulation technique is described. Then, the efficiency-optimised DMWPWM strategy is deduced. Compared with traditional DMWPWM strategy, the new strategy inherits the advantage of traditional DMWPWM that the NP voltage balance can be maintained in any modulation index and power factor. Moreover, it can reduce the system switching loss which leads to efficiency improvement, and it is simple and easy to implement. Finally, the proposed modulation technique is verified by simulation.

Design Analysis and Development of Inverter Topologies for Industries

This paper presents the most common inverter topologies and its design, analysis and development schemes. The main objective is to design and compare the three topologies of multilevel inverter for industries. These three topologies are mostly effectively and efficiently for quality improvement of the output voltage waveform of inverter. Photovoltaic (PV) and wind power generation (WPG) i.e. the renewable energy systems are playing a vital role in energy production. But, solar photovoltaic power (PV) has the prospective to develop one of the foremost suppliers to the future electricity supply. Therefore, Low voltage solar PV systems need a high voltage expansion converter for units of grid connection with multilevel inverter. The multilevel inverter topologies are being used in applications of medium and high power such as an active power filter, FACTS devices and a machine current due to their various merits in terms of power supplies low power dissipation, low harmonic distortion in voltage output waveform. Therefore, the simulation of multilevel inverter topologies is done and finalized that cascade multilevel inverter topology is more suitable as compared to other two by using MATLAB/SIMULINK.

Design Analysis and Development of Inverter Topologies for Industries

This paper presents the most common inverter topologies and its design, analysis and development schemes. The main objective is to design and compare the three topologies of multilevel inverter for industries. These three topologies are mostly effectively and efficiently for quality improvement of the output voltage waveform of inverter. Photovoltaic (PV) and wind power generation (WPG) i.e. the renewable energy systems are playing a vital role in energy production. But, solar photovoltaic power (PV) has the prospective to develop one of the foremost suppliers to the future electricity supply. Therefore, Low voltage solar PV systems need a high voltage expansion converter for units of grid connection with multilevel inverter. The multilevel inverter topologies are being used in applications of medium and high power such as an active power filter, FACTS devices and a machine current due to their various merits in terms of power supplies low power dissipation, low harmonic distortion in voltage output waveform. Therefore, the simulation of multilevel inverter topologies is done and finalized that cascade multilevel inverter topology is more suitable as compared to other two by using MATLAB/SIMULINK.

A New Feed-forward Compensation Inverter Control Strategy

With the development of new energy research, photovoltaic inverter is widely used in solar photovoltaic power generation system. In this paper, a new static feedforward compensation control strategy for current loop is proposed for the shortcomings of the single-phase PV inverter in the use of the typical Ⅰ-type system in the double closed-loop control system. Through the improved Park transformation, the equivalent model of the single-phase inverter is obtained. The control equation of the current is obtained by the method of feed-forward decoupling control in the equivalent inverter model. For the interference signal in the current control equation, The static feed-forward compensation control method eliminates the interference signal present in the inner loop of the current. Through this control method, the current loop in ensuring the performance of good follow at the same time effectively improve the current loop anti-jamming performance. At the same time, current loop control and voltage outer loop control using PI control, the formation of double closed-loop control system. The simulation results show that the anti - jamming performance of the double closed-loop inverter control system with static feed-forward compensation is better, the output waveform distortion rate of the inverter is low, and the PV inverter is stable in the presence of disturbance.

Control of Three-to-Five-Phase Matrix Converter Using Carrier-Based PWM Algorithm

Abstract - This paper proposes a simple Carrier-Based PWM (CBPWM) technique to control the three- to five-phase Direct Matrix Converter (3×5 DMC). The proposed technique uses the indirect modulation approach to control the 3×5 DMC such as a three-phase bidirectional rectifier followed by five-phase voltage source inverter (VSI). Based on this approach, it is possible to synthesize the desired five-phase output voltages with sinusoidal three-phase input currents and unity input power factor. A CBPWM method is suggested for each stage independently including both linear and overmodulation operating modes. By the proposed technique, in both operating modes, the maximum possible overall Voltage Transfer Ratio (VTR) are achieved. Moreover, this technique allows the input power factor to be controlled by controlling the input current displacement angle. The feasibility of the proposed technique has been verified by a series of simulation and experimental results based on Matlab/Simulink and dSPACE-DS1104 platform. The results show that, a sinusoidal output and input waveforms can be achieved with a maximum possible VTR in the linear region. However, in the overmodulation region, a maximum possible VTR is achieved at the cost of some distortion of output and input waveforms. Therefore, this technique can be used for the application where a higher VTR is essential.

Ionic pH and glucose sensors fabricated using hydrothermal ZnO nanostructures

Hydrothermally synthesized aluminum-doped ZnO (AZO) nanostructures have been adopted in extended-gate field-effect transistor (EGFET) sensors to demonstrate the sensitive and stable pH and glucose sensing characteristics of AZO-nanostructured EGFET sensors. The AZO-nanostructured EGFET sensors exhibited the following superior pH sensing characteristics: a high current sensitivity of 0.96 µA1/2/pH, a high linearity of 0.9999, less distortion of output waveforms, a small hysteresis width of 4.83 mV, good long-term repeatability, and a wide sensing range from pHs 1 to 13. The glucose sensing characteristics of AZO-nanostructured biosensors exhibited the desired sensitivity of 60.5 µA·cm−2·mM−1 and a linearity of 0.9996 up to 13.9 mM. The attractive characteristics of high sensitivity, high linearity, and repeatability of using ionic AZO-nanostructured EGFET sensors indicate their potential use as electrochemical and disposable biosensors.

Research on Attenuating Variable-Rate Reaching Sliding Mode Control Strategy for Three-Phase Current Source Inverter

A sliding-mode attenuating variable-rate reaching control strategy for three-phase current source inverter is presented. The proposed control strategy significantly improves solve the exist issues that the slow dynamic characteristic and the output waveform distortion using linear control technology in three-phase current source inverter. In order to facilitate the analysis and design of sliding mode controller, a new mathematical model of three-phase current source inverter is built, and it is further simplified through the spatial coordinate transformation. The switching surfaces and the attenuating variable-rate reaching control law are deduced. Finally, the simulation results verify the effectiveness and feasibility of the control strategy for three-phase current source inverter.

Study and Application of Sliding Mode Control Strategy for High-Power Current Source Inverter

For high-power current source inverter work object is a nonlinear time-varying systems, which could easily lead to the inverter voltage and current output waveform distortion, this paper firstly proposes a new variable-rate reaching sliding mode control scheme to solve the above problems existing in current source inverter system. In this scheme, we construct the variable structure model of the system, determine the sliding surface, give the variable-rate reaching control law and deduce the sliding domain. At last, the simulation result proves the validity and superiority of the scheme.

Output waveform analysis of an electro-hydraulic vibrator controlled by the multiple valves

The existing research of the electro-hydraulic vibrator mainly focuses on system stability, working frequency width and output waveform distortion. However, this high frequency performance of the electro-hydraulic vibrator is difficult to be improved greatly due to fast insufficiently frequency response of the servo valve itself and limited compensation capability of the control structure in the vibrator system. In this paper, to realize high frequency vibration, an improved two-dimensional valve (here within defined as a 2D valve) as a main control component is adopted to the parallel connection with a servo valve to control the electro-hydraulic vibrator. Because the output waveforms of this electro-hydraulic vibrator are incapable to be verified through timely feedback as in the conventional electro-hydraulic servo system, the analysis to the output waveform becomes crucial to the design and control of the electro-hydraulic vibrator. The mathematical models of hydraulic actuation mechanism and the orifice area of the parallel valves connection are established first. And then the vibration process is divided into two sections in terms of the direction of the flow, the analytical expression of the excited waveform is solved. Based on the analytical results, the vibration boundary positions and the relationships exist between working states and the control parameters are derived. Finally an experimental system was built to validate the theoretical analysis. It is verified that this electro-hydraulic vibration system could achieve high working frequency, up to 2 000 Hz. The excited waveform is similar to the sinusoidal waveform. And the ascent and decent slopes of the waveforms are somewhat asymmetrical. This asymmetry is not only caused by the change of the direction of the elastic force but also dependent on the bias position of the vibration. Consequently the distortion of effective working waveform is less than 10%. This electro-hydraulic vibrator controlled by the multiple valves could not only greatly enhance the working frequency but also precisely control the vibration characteristic variables such as waveform shape.

Research on Effect of Harmonics to Hysteresis Current Tracking Control Performance

A simulation model was built based on the Simulink module in the Matlab to study the effect of DC power harmonics to hysteresis current control performance. The DC power supply in the hysteresis current control circuit was obtained by a three-phase rectifier circuit, and the harmonics of DC power supply vary with the value of the capacitor which was in parallel to the rectifier circuit output. The result of experiment shows that the harmonics cause the inverter output waveform distortion, even cause hysteresis current control tracking failure.

The Analysis and Design of Three-Phase Static Inverter Deadband Effect and Harmonic Suppression

in order to solve the problem of three-phase static inverter output waveform distortion, detailed analyzed of the voltage distortion caused by the deadband effect and the resulting harmonic components. The control method is proposed to set the deadband time combining with the voltage compensation, while in order to improve the inverter output, the converter output to design a trap filter and a low pass filter cascaded filtering circuit. Simulated analysis the entire system though Saber, using the digital chip TMS320F2812 to achieve appropriate compensation strategies, simulation results and experimental results have all proved the effectiveness of the design method.

Possible analogy between the optimal digital pulse width modulation technology and the equivalent optimisation problem

A novel nonlinear searching method, immune algorithm (IA), is presented based on the immune theory in biology. This method is applied to resolve the optimal control problem of the sinusoidal pulse width modulation (SPWM) inverter, and the IA is adopted to find the optimal digital SPWM control sequences. Furthermore, the IA well fits with on-line microprocessor implementation. A single-phase full-bridge inverter is considered, and the optimal digital SPWM control sequences are calculated to minimise total harmonic distortion of output waveform. These digital sequences are used in a simulation system and experiment setup to verify the usefulness of the method.