Line Current Harmonic Distortion Research Articles

Performance Evaluation of the B4 Topology for Implementing Grid-Connected Inverters in Microgrids

The B4 topology is an interesting alternative to the conventional B6 inverter due to its reduced number of parts and lower cost. Although it has been widely used in the past, especially in low-power motor drive applications, its application as a grid-connected inverter is an open area of research. In this regard, this paper analyses the feasibility of the B4 inverter topology for grid-connected applications. A versatile 7 kW inverter prototype, which may be configured as B4 and B6, was built, allowing for a comprehensive evaluation of the performance of both topologies. Through an analytical study and experimental tests, the performance of the B4 and B6 topologies was comparatively evaluated in terms of efficiency, total harmonic distortion of line currents, current unbalance, cost, and mean time between failures. The study was carried out in the context of microgrid systems, highlighting their role in the integration of renewable energy and distributed generation.

A Three-Phase Grid Connected Photovoltaic System with Modified MPPT Method

In this study, a three-phase grid-connected Photovoltaic system is demonstrated. A photovoltaic (PV) system that is connected to the grid, provides several benefits, including a topology that is simple, high efficiency and so on. Considering control scheme difficulty greatly enhanced because of all the regulatory requirements, which are maximum power point tracking (MPPT), coordinated with the supply voltage, harmonic drop as a current output, must be addressed at the same time. The DC/DC converter, solar panels, DC-link, three-phase voltage source inverter (VSI) on the grid, as well as output filters are all detailed representations of the essential components of the system in this model. Line current harmonic distortion should be reduced. A sophisticated control strategy with two PI controllers and MPPT is purposed in this paper to stabilize DC voltage. A robust phase- locked loop (PLL) synchronizes a grid-connected voltage source inverter with three phases. The simulation and practical findings reveal that the stability as well as efficiency of a three-phase grid connected PV system are high. Keywords- solar energy, grid-connected inverters, photovoltaic (PV), maximum power point tracking (MPPT).

An Optimized Hybrid SOVM Modulation Based on MDAVT for OEWIM

This paper presents a new optimized hybrid space opposite vectors modulation (SOVM) strategy based on the multiple division of active vector time (MDAVT) for a dual inverter fed open end winding induction motor (OEWIM) to reduce the common mode voltage (CMV) as well as line current harmonic distortion. Ordinarily, to drive all ac drives at variable voltage and frequencies voltage source inverters (VSIs) need to be employed. In this regard various PWM strategies came into existence to provide gating signals to VSIs. Mostly all the PWM converters yields CMV across the load terminals which in turn results common mode currents. These common mode currents lead to the electromagnetic interference and explicitly responsible for the failure of bearings in case of motor loads. In order to reduce this CMV in this paper, a SOVM strategy is adapted. The concept of an optimized MDAVT is also introduced along with the SOVM to obtain the less current ripple. Finally these adaptions lead to an optimized hybrid PWM strategy and is employed for dual two level inverter fed OEWIM. In the present work in order to evaluate the optimistic performance of proposed switching strategy for OEWIM MATLAB software is chosen. And to validate the proposed strategy experimentally dSPACE 1104 is employed for digital implementation of PWM signals. Finally the superiority of the proposed PWM scheme in terms of CMV is presented with the detailed analysis. Whereas, the superiority in terms of current THD is shown with the help of the simulation and experimental results.

An Optimized Hybrid SVPWM Strategy Based on Multiple Division of Active Vector Time (MDAVT)

This paper presents a new advanced bus-clamped space vector pulsewidth modulation (SVPWM) technique to reduce line current harmonic distortion as well as switching loss. The proposed sequence introduces multiple division of active vector time (MDAVT) in a subcycle. An analysis of optimal subdivision of active vector dwell time is presented. Existing bus-clamping pulsewidth modulation techniques use double-switching clamping sequences, which use only one zero state and apply an active vector twice in a subcycle. The proposed MDAVT-based SVPWM technique presents a hybrid SVPWM technique. The additional switching is added when the fundamental voltage crosses zero. The switching patterns for the other two phases are not changed. The harmonic performance and switching loss characteristics of the proposed hybrid SVPWM techniques over the existing SVPWM is verified with experimental results on a 415-V, 2.2-kW induction motor drive.

Analysis and Design of a DC-Side Symmetrical Class-D ZCS Rectifier for the PFC of Lighting Applications

This paper proposes the analysis and design of a DC-side symmetrical zero-current-switching (ZCS) Class-D current-source driven resonant rectifier to improve the low power-factor and high line current harmonic distortion of lighting applications. An analysis of the junction capacitance effect of Class-D ZCS rectifier diodes, which has a significant impact on line current harmonic distortion, is discussed in this paper. The design procedure is based on the principle of the symmetrical Class-D ZCS rectifier, which ensures more accurate results and provides a more systematic and feasible analysis methodology. Improvement in the power quality is achieved by using the output characteristics of the DC-side Class-D ZCS rectifier, which is inserted between the front-end bridge-rectifier and the bulk-filter capacitor. By using this symmetrical topology, the conduction angle of the bridge-rectifier diode current is increased and the low line harmonic distortion and power-factor near unity were naturally achieved. The peak and ripple values of the line current are also reduced, which allows for a reduced filter-inductor volume of the electromagnetic interference (EMI) filter. In addition, low-cost standard-recovery diodes can be employed as a bridge-rectifier. The validity of the theoretical analysis is confirmed by simulation and experimental results.

Interleaved Boundary Conduction Mode (BCM) Buck Power Factor Correction (PFC) Converter

An interleaved boundary conduction mode power-factor-correction buck converter that maintains high efficiency across entire load and line range is proposed. The adaptive master-slave interleaving method maintains stable 180° out-of-phase operation during any transient. By interleaving two parallel-connected buck converters, the input current ripple is halved while the ripple frequency is doubled, which leads to a smaller differential mode line filter. The line current harmonic distortion is analyzed to examine the allowable output voltage range while meeting harmonic regulations. The operation and performance of the proposed circuit is verified on a 300 W, universal line experimental prototype with 80 V output. The measured efficiencies remain above 96% down to 20% of full load across the entire universal line range. Even at 10% of full-load condition, the efficiency remains above 94%. The input current harmonics also meet the IEC61000-3-2 (class D) standard.

A Microcomputer-Based Predictive Digital Current Programmed Control System for Three-phase PWM Rectifier

The paper describes a microcomputer control system, which uses the floating-point digital signal processor TMS320LF2407 from Texas Instruments, for three-phase PWM rectifier. It could effectively eliminate harmonic distortion of line currents and provides power factor correction. Moreover, it can be save electrical energy and reduction of production cost. In the control system, the predictive current control in two-dimensional (α-β) stationary frame, makes the input current following the phase voltage in phase to get unity power factor; and space vector pulse wide modulation (SVPWM) generates the modulation wave. Finally, the three-phase PWM rectifier using the proposed control system is designed in Simulink/Matlab and executed in laboratory prototype, and the results are provided to verify the proposed control system in the end of the paper.

Optimal Reactive Compensators in Power Systems Under Asymmetrical and Nonsinusoidal Conditions

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> Based on the condition for the minimum rms value of line currents, a method for improving the power factor in power systems under asymmetrical and nonsinusoidal conditions is presented. This paper offers straightforward and convenient formulations of active currents for the three-phase four-wire, three-phase three-wire, and single-phase systems. Owing to the transformation matrix introduced in this paper, the formulation of active currents is valid regardless of whether the voltages and currents are balanced or unbalanced and it permits any point of the system to be chosen for the voltage reference. Observing the constraints related to the reactive compensators, the line current minimization procedure is used for the determination of optimal compensating capacitances for the three-phase four-wire, three-phase three-wire, and single-phase systems. The optimal reactive compensators based on up to six capacitors are proposed. The definitions of power factors before and after compensation are introduced. The influence analysis of nonactive power compensation on harmonic distortion of line currents has been also performed. Experimental results are obtained to confirm the validity and applicability of the proposed compensation procedure. </para>

A passivity‐based controller design for three‐phase active rectifiers without dynamic feedback

In this paper, a new passivity‐based design which does not employ dynamical state feedback is developed to achieve dc‐bus voltage regulation and unity‐power factor control for a three‐phase boost‐type PWM active rectifier. The results may be considered as an improvement to the previously published scheme of Lee using the passivity‐based control theory of Euler‐Lagrange (EL) systems. The proposed controller can retain the advantages of dynamic state‐feedback controller, which yields fast dynamic response, near unity power factor, low harmonic distortion in line currents, decoupled current‐loop dynamics and guaranteed zero steady‐state error. Since the passivity‐based methodology is a nonlinear approach, good tracking response and global stability can be assured under large perturbations in parameters and loads. Experimental results are given. Comparison of the performance of the proposed design with classical linear proportional‐integral and passivity‐based dynamic state‐feedback controllers are also discussed.

Space Vector PWM as a Modified Form of Sine-Triangle PWM for Simple Analog or Digital Implementation

Conventional space vector PWM (CSVPWM) has the advantages of yielding up to 15% higher fundamental line-side voltage for a given DC bus voltage and also less harmonic distortion in line currents over sine-triangle PWM (SPWM). However, no analog implementation of CSVPWM is possible in its traditional form. Digital implementation of CSVPWM is also more complex than that of SPWM. This paper analyses the two techniques. The analysis establishes that CSVPWM can be viewed as a modified form of SPWM, and leads to a simple method to implement CSVPWM. The simplified method does not require evaluation of trigonometric functions, look-up tables, sector identification etc. An existing line of products employing SPWM can easily be upgraded to exploit the benefits of CSVPWM. The work serves to unify the understanding of triangle-comparison based PWM and space vector based PWM techniques. The work is of tutorial value to students and engineers.

A high-frequency-transformer-isolated two-switch three-phase ac-to-dc converter with low harmonic distortion

This paper presents a high-frequency-transformer-isolated, single-stage, fixed-frequency, soft-switching, three-phase ac-to-dc converter with low line-current harmonic distortion. The converter uses only two switches and a simple control circuit without any active control scheme. Various operating modes of the converter are presented and analyzed. Based on the analysis, design curves are obtained and a design example is presented. The performance of the proposed converter is evaluated using PSPICE simulation and a laboratory prototype with 500 W output (using IGBTs as switching devices).

A Novel Soft-Switching High-Frequency Transformer Isolated Three-Phase AC-to-DC Converter With Low Harmonic Distortion

A high-frequency transformer isolated, fixed-frequency, 3-/spl phi/ single-stage ac-to-dc converter using a boost-integrated bridge converter that employs a new gating scheme is proposed. This converter enjoys natural power factor correction with low line current harmonic distortion and symmetric high frequency voltage and current waveforms while ensuring zero-voltage switching for all the switches for a wide variation in load and line voltage. Various operating modes of the converter are presented and analyzed. Based on the analysis, design curves are obtained and an optimum design is given. A design example is presented. Results obtained from SPICE simulation and a 500 W output experimental prototype are given to verify the performance of the proposed converter for varying load as well as line voltage.

Bi-directional single-phase half-bridge rectifier for power quality compensation

A single-phase half-bridge rectifier with a capacitor clamped scheme is proposed. Four power switches and one flying capacitor are employed in the proposed rectifier. Bipolar and unipolar PWM control schemes are used to perform power factor correction and achieve low total harmonic distortion of line current. A neutral point voltage balance compensator, hysteresis current controller and DC link voltage regulator are used to balance neutral point voltage, to track line current command, and to maintain the constant DC bus voltage. The proposed control scheme and the circuit configuration can also perform a shunt active power filter operation to eliminate the harmonic currents and compensate the reactive power generated from the nonlinear load. Analytical and experimental results are presented to illustrate the validity and effectiveness of the proposed control scheme.

A multilevel buck converter based rectifier with sinusoidal inputs and unity power factor for medium voltage (4160-7200 V) applications

A novel rectifier topology for high power (0.5 to 10 MVA) current source based AC motor drives is proposed. This rectifier is composed of a multi-winding transformer, a multi-level diode rectifier and a modified multi-level buck converter. The rectifier produces near unity input power factor and sinusoidal input current under any operating conditions. In addition, the proposed rectifier features reliable operation and low manufacturing cost. In this paper, the operating principle of the proposed rectifier is introduced. A number of design issues are investigated, which include PWM switching patterns, input power factor and line current harmonic distortion. Some design considerations such as the effect of the line inductance discrepancy on system performance are addressed. Experiments on a 5 kVA/208V four-level prototype are carried out for verification.

Unity power factor boost converter with phase shifted parallel IGBT operation for medium power applications

Phase-shifted parallel (PSP) operation of IGBTs is proposed for unity pf boost converters, to increase both the converter power rating and operating frequency. This technique allows unity pf operation of medium power AC and DC motor drives, and switch mode power supplies from a single-phase, unregulated AC supply, with minimum line current harmonic distortion. Since operating frequency is increased by integer multiples of IGBT switching frequency, the same core size for the boost inductor can be used to transfer larger amounts of power at the expense of additional power switching elements and a simple pulse separation circuit. Equal average current sharing is inherent in PSP operation strategy without any external circuits for equalisation. The design and implementation of a 28 kW, 40 kHz unity pf boost converter with two phase-shifted parallel IGBTs are presented. Advantages and disadvantages of PSP IGBT operation in increasing the power rating of boost converters are also given in comparison with other converter and power semiconductor parallel operation techniques.

Dynamic and steady state analysis of a three phase buck rectifier

Current source rectifiers among other alternatives, offer several advantages over line commutated rectifiers. Advantages include displacement power factor control and reduced line current harmonic distortion. This paper analyzes the current source rectifier (CSR) in transient and steady state, the models are developed in a synchronous reference frame. The load behavior is characterized for two load conditions, resistive load or, in general, increasing current for increasing voltage, and constant output power, decreasing output current for increasing voltage. Constant power operation can occur for a converter system supplying a pulse width modulation (PWM) inverter with high dynamics. Several static converter characteristics such as power factor, real and reactive power are analyzed for both types of load. Transient characteristics are analyzed for both types of load by exact small-signal model with full set of equations.

Single-phase power-factor-correction AC/DC converters with three PWM control schemes

Three pulse-width modulation (PWM) control schemes for a single-phase power-factor-correction (PFC) AC/DC converter are presented to improve the power quality. A diode bridge with two power switches is employed as a PFC circuit to achieve a high power factor and low line current harmonic distortion. The control schemes are based on look-up tables with hysteresis current controller (HCC) to generate two-level or three-level PWM on the DC side of diode rectifier. Based on the proposed three control schemes, the line current is driven to follow the sinusoidal current command which is in phase with the supply voltage, and two capacitor voltages on the DC bus are controlled to be balanced. The simulation and experimental results of a 1 kW converter with load as well as line voltage variation and shown to verify the proposed control schemes. It is shown that unity PFC is achieved using a simple control circuit and the measured line current harmonics satisfy the IEC 1000-3-2 requirements.

Soft-switching single-stage AC-to-DC converter with low harmonic distortion

A 1 /spl phi/ high-frequency (HF) transformer isolated, soft-switching single-stage ac-dc converter with low line-current harmonic distortion is presented. Its operation is explained with equivalent circuits for the various intervals. The converter is analyzed and design curves are obtained. An optimization parameter is introduced and a systematic design procedure is illustrated with a design example. Detailed SPICE simulation and experimental results of a 500 W converter with load as well as line voltage variation are given to verify theory. The proposed converter employs a zero-voltage transition (ZVT) network to ensure zero-voltage switching (ZVS) at all loads, and natural power factor correction is ensured using a simple control circuit.

A hybrid resonant converter operated as a low harmonic rectifier with and without active control

A 1-/spl phi/ high-frequency transformer-isolated AC-to-DC-controlled rectifier with low-line-current harmonic distortion using a variable-frequency-controlled hybrid parallel-series resonant converter bridge is proposed. Operation with and without active line-current waveshaping is presented. The state-space analysis method is used to get various design curves and to predict theoretically the waveforms and line-current harmonic distortion. By exercising active current control, power factor (PF) close to unity with low-line-current distortion is maintained for the entire range of operation in addition to zero-voltage switching (ZVS). Simulation results obtained from the state-space model, SPICE3 (without active control), and experimental results (rated at 150 W with and without active control) are given to demonstrate and validate the operating principle and characteristics of the proposed converter.

Operation of the LCC-type parallel resonant converter as a low harmonic rectifier

A single-phase high-frequency transformer isolated single-stage AC-to-DC controlled rectifier with low line current harmonic distortion using a variable-frequency controlled LCC-type (or series-parallel) resonant power converter (SPRC) is presented. A simple analysis and design procedure is used for designing the converter for low line current harmonic distortion and high power factor operation. The converter performance characteristics have been verified with SPICE3 simulations (without active control) and experimental prototype SPRC (rated at 150 W, with and without active control) for variation in load as well as line voltage. When operated with active current shaping, this converter operates in zero-voltage-switching mode for the complete range, maintaining power factor close to unity with low line current distortion and low peak current compared to the parallel resonant converter.