PWM Converter Research Articles

Improving the Dynamics of an Electrical Drive Using a Modified Controller Structure Accompanied by Delayed Inputs

This paper presents the operation of a modified speed controller with a standard PI/PID structure that includes the preprocessing of the controller’s input signal, focusing on the past behavior of control errors. The modification involves adding a delay line, with the outputs of the individual line segments summed with a weighting method, as detailed in the paper. One of the significant advantages of this method is its use of a standard industrial controller structure, which makes it highly practical and easily implementable in existing systems. By relying on well-established control frameworks, this approach reduces the need for specialized hardware or complex modifications, allowing for smoother integration and lower implementation costs. The delay-based signal shaping shows excellent properties for the electric drive system powered by a hard-switching PWM converter. The set of weighted delays acts as a filter whose parameters are chosen using the quality function to test different configurations for optimal performance. When tested in a speed control system for a Permanent Magnet Synchronous Motor, the modifications improved the control quality index, indicating better performance and efficiency. Importantly, the system allows for reducing or eliminating the gain in the differentiating part of the controller, which decreases motor current chattering and noise. This paper includes an experimental verification of the proposed solution in a laboratory setting under semi-industrial conditions.

Single-switch PWM converters for DC-to-DC power with reliability tolerance for battery power purposes

The functioning of fault-tolerant boosted conversions in both good and bad circumstances is covered in this work. The majority of our power plants and automotive applications make extensive use of surge conversions. Every component in a converter is accountable for causing one of the many problem kinds that affect the converter. In order to construct a tolerant of faults DC-DC converter, the reaction of the single switch DC-DC converter under various potential failures was examined. Utilizing a MATLAB Simulink approach, the response of each device across both typical and various potential fault scenarios was derived. The booster converter can also undergo additional heat research to determine how the converters react at various temps.

Field-Oriented Control of a Nine-Phase Cage Induction Generator with Large Speed Changes and Variable Load

This paper presents a voltage control system for multiphase squirrel-cage induction generators operating at a high variability of speed and variable load. Field-oriented vector control was used with a change in the sequence of the stator phase currents what changes the number of poles of the magnetic field produced by nine-phase stator winding. At low speeds, the current sequence is changed so that the number of poles increases allowing for the desired voltage to be obtained with greater efficiency. The task of the automatic control system was to control the DC voltage to a desired value at the output of the multiphase PWM converter. This is an alternative control method to the scalar control of voltage and frequency presented in a previous work. The control method and parameters of the automatic control system result from the mathematical model of the multiphase induction machine. The results of the laboratory tests were compared with the effects of the operation of the same nine-phase scalar controlled generator.

Maximum Power Control of DFIG Based Grid Connected Wind Turbine Generator System

This paper presents a simulation model of variable speed wind turbine with a doubly fed induction generator developed in Matlab/simulink. Vector control of a doubly fed induction generator (DFIG) drive for variable speed wind power generation is described. A slip ring (wound rotor) induction generator with back to back three phase PWM converter between its rotor and the grid forms the electrical system. A vector control scheme for the PWM converters results in independent control of active and reactive power. Line (supply) voltage oriented reference frame has been used to independently control the active and reactive power. Results are provided at the end for sub synchronous and super-synchronous operation of the DFIG.

Analysis of a Single-Phase Line-Interactive UPS System

This paper presents an analysis of a single-phase line interactive uninterruptible power supply (UPS) system, allowing output voltage conditioning, such as voltage harmonic suppression and sag/swell compensation. Additionally, the UPS input current is also compensated, allowing current harmonic suppression and reactive power compensation. In other words, the UPS system acts as a true unified power quality conditioner (UPQC), when working in standby operation mode. The power rate handled by both series and parallel PWM converters depend on the operation conditions of the UPS system, such as the amplitude of the fundamental input voltage, the total harmonic distortion of the load current, fundamental power factor of the load, battery charging, among others. In standby mode, the amplitude of the UPS output voltage will be allowed to vary in order to follow the amplitude of the input voltage within a limited range defined by design requirements. This strategy will allow an effective optimization of the efficiency of the UPS system. Mathematical analyses of the single-phase line interactive UPS system are presented in order to obtain the state space models of the two PWM converters. Validation results are presented in order to evaluate the performance of the line interactive UPS system

Behavior analysis of dual-star permanent magnet synchronous generator with inter-turn short fault

ABSTRACT The dual-star PMSMs (DSPMSM) are widely used in high-power applications due to their robustness and reliability. As they mostly work in harsh environments, they are commonly subject to many faults. One of the most dangerous faults is the inter-turn short fault (ITSF), which induces torque vibrations and overheating inside the machine, and may lead to other faults. To properly handle this issue, it must be correctly understood, and the relationship between different machine’s quantities (speed, dq currents, fault ratio and resistance) and the severity of the fault (torque’s oscillations and short-circuit current) must be established. In this context, this paper presents a detailed analysis of the DSPMSM behavior under a single ITSF, considering the influence of the mentioned quantities and the PWM converter on torque oscillations and short-circuit current. A mathematical model of the machine is developed, and a hysteresis current controller is used to impose the desired direct and quadrature axis stator currents. Simulation tests are conducted by considering different scenarios. Simulation results showed that to reduce fault severity, a trade-off between speed reduction and flux weakening must be accomplished, consequently accepting some performance degradation. Also, results showed the complex behavior of the short-circuit current, as it does not rely linearly on fault parameters.

Bidirectional PWM Converter to Interface AC Part to DC Microgrid with Neutral Potential Balancing

This research presents a description of a bidirectional pulse width modulated converter that functions as a rectifier by using the direct power control strategy and space vector modulation technology. In contrast to the voltage-oriented control strategy, this method minimises the number of internal current loops and requires more tuning. While functioning as an inverter, it applies the space vector modulation technique as well. The approach, on the other hand, is not the same as rectifiers since it calculates the duty ratio of the neighbouring voltage vectors in each small triangle that is generated in each sector that has a period of 60 degrees. In both situations, the neutral point potential has been brought back into equilibrium.

Simple Control Schme of Three-Level PWM Converter Connecting Wind Turbine with Grid.

This paper proposes a simple direct power control using space vector modulation (DPC-SVM) for three-phase three level neutral point clamped (3L-NPC) PWM converter connecting a wind turbine generator with grid. The active and reactive power are used as the control variables instead of the currents applied in conventional control method. Moreover, grid voltage sensors are replaced by a virtual flux (VF) estimator. The theoretical principle of this method as well as the synthesis of the active and reactive power controllers are discussed. It is shown that the proposed method exhibits several features as: simple and robust algorithm as well as simple tuning procedure of PI power controllers. Furthermore the paper presents a LCL-filter design, which fulfils IEEE-SCR 20-50 recommendation. Simulation results have proven an excellent performance and verified the validity of the proposed system.

Noise-Robust Online Measurement of the On-State Resistance of the Power Semiconductor Devices in PWM Converters

Noise-Robust Online Measurement of the On-State Resistance of the Power Semiconductor Devices in PWM Converters

Research on Grid-Connected Control Strategy of Photovoltaic (PV) Energy Storage Based on Constant Power Operation

In order to effectively mitigate the issue of frequent fluctuations in the output power of a PV system, this paper proposes a working mode for PV and energy storage battery integration. To address maximum power point tracking of PV cells, a fuzzy control-based tracking strategy is adopted. The principles and corresponding mathematical models are analyzed for the three-phase voltage PWM converter and bidirectional DC/DC converter, while feedforward decoupling double closed loop, constant power (PQ), and constant voltage charge/discharge control strategies are proposed. Space vector pulse width modulation (SVPWM) technology is utilized to generate power switching tube driver signals. Finally, a simulation model is developed in MATLAB/Simulink for system analysis. The results demonstrate that the proposed method enables constant grid-connected power generation and constant voltage charging of the energy storage battery when the PV cell’s power generation exceeds that of the grid. When insufficient solar power generation occurs, both the PV system and energy storage battery work together to achieve constant grid-connected power.

Smart Nonlinear Energy Feedback Power Electronic Load to Simulate Power Quality Problems

This paper proposes a design approach for an energy feedback power electronic load (PEL) based on back-to-back voltage source PWM converters. It can simulate not only constant linear loads but also a class of nonlinear loads to simulate power quality problems. The rectifier side and the inverter side are decoupled in control by using a DC capacitor. The rectifier side is responsible for tracking designed current commands to achieve the designed load characteristics, and based on the characteristics of the current commands, a multi-resonant controller plus state feedback controller was designed by using the internal model principle. The inverter side employs an LCL filter with active damping to control the phase of the grid-connected current, enabling energy to feed back to the grid. A simulation model of this PEL is established in Simulink software, and the simulation results verify the effectiveness of the proposed control strategy.

Control of a wind energy conversion system based on brushless doubly fed induction generator

This paper discusses the control a new topology of a brushless doubly-fed induction generator (BDFIG) using back-to-back PWM converters. The goal of BDFIG control is to achieve a similar dynamic performance to the doubly fed induction generator (DFIG), The control strategy for flexible power flow control is developed. Currently the BDFIG has been the subject of current investigation and it shows to be a valid alternative for wind energy systems.

Optimal Frequency and Voltage Control of Self-Excited Induction Generator for Wind Power Generation Using PWM Converter and Load Management

Optimal Frequency and Voltage Control of Self-Excited Induction Generator for Wind Power Generation Using PWM Converter and Load Management

The DC Inductor Current Ripple Reduction Method for a Two-Stage Power Conversion System

This paper proposes a method for minimizing the inductor current ripple of a DC–DC converter in a two-stage power conversion system consisting of a grid-connected PWM converter and an interleaved multiphase three-level DC–DC converter. To reduce the output voltage ripple, the three-level DC–DC converter is configured in parallel and operated interleaved. However, a circulating current generated by the interleaved operation increases the inductor current ripple of each DC–DC converter and causes system loss and inductor saturation. In this paper, the inductor and output current ripple of the interleaved three-phase three-level DC–DC converter is mathematically analyzed and the effect of the DC–DC converter’s duty ratio and output voltage on each current ripple is described. Based on this analysis, a method is proposed for controlling the optimal DC link voltage through the PWM converter, so that the DC–DC converter is controlled with the duty ratio that minimizes the inductor current ripple. The simulation and experimental results under various operating conditions are presented to verify the feasibility of the proposed control method.

A Switching Oscillation Event-Triggered Switch Fault Detection Method for SiC DC–DC Converter

Switch fault detection is critical for the safety and reliability of a SiC dc–dc converter, which is however difficult by directly comparing the PWM voltage and the gate signal due to the harsh electromagnetic environment and ultrahigh switching frequency. To address the challenges, a novel method is proposed to detect and diagnose the switch fault using the converter PWM high-frequency (HF) switching oscillation. First, the switching event status in a SiC dc–dc converter is captured from the HF switching oscillation current in a noncontact way. Then, the switch fault is detected and diagnosed by checking the signal integrity of the switching events with no need for a gate signal. Finally, a switching oscillation event-triggered switch fault detection system is developed including the HF oscillation sensor, switching event capture circuit, and switch fault detection and diagnosis unit. Experimental work is carried out and the results demonstrate the performance of the method with high safety up to MHz.

Space Vector Modulation technique implementation for the control of a Three-Phase Matrix Converter

The Three-Phase Matrix Converter (3ph-MC) is a direct AC-AC converter that employs controlled semiconductor switches to enable a direct connection between the three-phase source and load. This setup enables an unlimited output frequency, thanks to the use of semiconductor switches with controlled turn-off capability. However, the 3ph-MC suffers from the simultaneous commutation of bidirectional switches, which has limited its popularity. Fortunately, several control techniques have been developed to overcome this issue and ensure safe switch operation. Among these strategies, Roy, Venturi, and the Space Vector Modulation (SVM) Techniques are the moste widely used. In this context, the present paper investigates the implementation under Matlab / Simulink of a 3ph-MC using SVM. Unlike conventional PWM converters, the 3ph-MC does not cause switching common mode voltage across the load system terminals, which can lead to common mode current and bearing failure in load drive. The use of SVM can rectify these issues and minimize the effect of harmonic fluctuation in AC output voltage. The paper includes simulation results to validate the proposed system.

Research on control system for improving the grid-connected efficiency of small hydropower

Aiming at the problem of low efficiency at low flow in small hydropower stations, a permanent magnet direct-drive hydropower generation control system based on dual PWM converters is proposed to realize wide-range variable-speed constant-frequency hydropower generation of hydraulic turbine units and improve the comprehensive power generation efficiency of small hydropower stations. In this control system, the hydraulic turbine is coaxially connected to the permanent magnet synchronous generator(PMSG) through the flywheel, and the power grid is connected by back-to-back dual PWM converters, and the bidirectional energy flow is realized by the voltage space vector pulse width modulation method. The generator-side converter controls the rotating speed of hydraulic turbine units and tracks the optimal speed point of the hydraulic turbine units in real time to realize the maximum power output of hydraulic turbine units. The grid-side converter adopts active power and reactive power decomposition control method to stabilize the DC bus voltage and provide the reactive power required by the grid. Finally, the effectiveness of the proposed control system was proved by comparative experiments in a 400V/200kW/428rpm small hydropower station.

Research on supraharmonic emission characteristics and influence factors of two-stage single-phase frequency converter

PWM converters, switching power supply, and other power electronic equipment inject a large quantity of supraharmonics into the power distribution network when they are connected to the network on a large scale, resulting in more and more serious power quality problems. In this paper, a two-stage single-phase frequency converter is selected and studied in depth about its supraharmonic emission characteristics and influence factors. First, a Fourier series equation of the grid side current of the frequency converter is derived using switching function method, which shows great simplicity and convenience in the theoretical analysis. The equation shows that the grid side current supraharmonics include odd supraharmonics and sideband supraharmonics related to the input and output frequencies of the frequency converter. Then, the supraharmonic ratio is calculated and it can be found that the ratio is associated with the output power of the frequency converter and the capacitance of the filter capacitor. The existence of the power system impedance also affects the supraharmonic ratio. Finally, the correctness of the theoretical analysis is verified by simulations on Matlab. An experiment of actual equipment was also carried out to prove theoretical results, which measured the conducted emission of a compact fluorescent lamp electronic ballast with load. The study will provide a reference for quantification, detection, and monitoring of supraharmonics in the power distribution network.

Accurate Design of Output Filter for DC–DC PWM Buck Converter and Derived Topologies

This paper presents an analysis of an LCR second-order low-pass filter capacitor to achieve a specified ripple output voltage in Buck, forward, Zeta, and Ćuk PWM DC-DC power converters for continuous-conduction mode (CCM). Current and voltage waveforms across output filter components are derived. Using the waveform of the ac component of the output voltage, an expression for the ripple voltage is developed in terms of the filter capacitance and equivalent series resistance. The results can be used for all PWM converters with the LCR output filter, such as Buck, forward, Zeta, and Ćuk PWM DC-DC converters. Theoretical results were in good agreement with simulation and experimental results.

Reduction of Zero-Sequence and Differential-Mode Circulating Currents and Common-Mode Voltage in Parallel PWM Converters

This paper aims to present a reduction strategy for circulating current and common mode voltage in parallel PWM converters. As the common mode voltage reduction is possible only with the elimination of some switching vectors, it may affect the circulating current paths. Elimination of both mentioned parameters at the same time is impossible for the systems with two-level converters. Therefore, in addition to the modification of the PWM strategy, an interface circuit is introduced to reduce the circulating current as well as reducing current ripple and losses. This topological modification adds some degree of freedom and leads to a reduction of circulating currents passing through each switch which releases its current carrying capability and reducing conduction losses especially in higher power and voltage applications. Simulation and experimental results are presented to verify the analysis of the proposed strategy.