Proportional Resonant Regulator Research Articles

Reduction of Auto-Power Procedure Influence on the Photovoltaic Inverter On-Board Bus System Caused by Pulsed Loads

The article presents an on-board power system designed for ships, aviation, and space vehicles using energy from photovoltaic panels. The power structure includes both DC and high-frequency AC power buses. As a result of pulse loads, this system is exposed to disturbances that cause electronic systems to reboot. To reduce the effect of the appearance of secondary disturbances in the AC bus to which the photovoltaic converter is connected, a new control strategy has been proposed. This strategy improves the operation of the proportional resonant regulator that controls the AC bus current by making the reference values linearly dependent on the DC bus voltage. A prototype of such a system was designed in the laboratory. The FPGA control board was pulse-disturbed, leading to start the auto-power procedure, and additional disturbances were observed in the AC bus for the standard system. Reduction in the impact of these disturbances was achieved using the proposed control method by reaching a limitation of the bus current in dynamic states caused by the auto-power on process from 280% to less than 100% of the steady-state value. Experimental results verified the validity of the proposed method.

A Current-Control Strategy for Grid-Connected Converter Based on Inductance Non-Linear Characteristic Compensation

Inductance is a necessary device for a grid-connected converter (GcC) to attenuate the switching-frequency harmonics in injected grid currents. However, in practice, the inductance decreases with an increase in output current. Especially when the amplitude of sinusoidal currents is higher, the inductance will vary over a wide range as the current value changes in a period. This variation may lead to system instability and cause output current fluctuation. To solve this issue, the model of the GcC with a proportional resonant regulator is firstly built, and the system stability with different current values is analyzed using the Nyquist criterion. The results show that the system stability decreases with an increase in current absolute value. Further, a loop gain compensation unit is embedded into the current regulator to maintain the loop gain constant and ensure the stability of the system under a wide variation range of current values. With this scheme, the compensation unit is only determined by the rated value and the non-linear characteristic of the filter inductance. Therefore, the loop gain compensation unit is independent of the original control system, and the traditional controller parameter design method can also be inherited. Finally, the simulated and experimental results from a 50 A static var generator (SVG) with wide filter inductance variation (using Mega-Flux core) have verified the correctness of the analyses and the effectiveness of the proposed method in this paper.

Plant integrated proportional integrating based control design for electric vehicle charger

The paper presents the control design of on-board two-stage electric vehicle (EV) charger. The first stage AC-DC converter of EV charger plays a very important role in supporting the grid reactively. Therefore, a reduced order plant integrated proportional integrating (PIPI) controller has been designed for first stage of EV charger. Generally, a proportional resonant (PR) regulator is used for tracking of grid current reference in control of AC-DC converter. However, conventional PR regulator is a third order system due to that the complexity of controller is increased. To reduce the complexity of controller, a first order PIPI regulator has been designed which has all the functionalities of conventional PR regulator and can track any periodic signal. This method is implemented in inner current control loop of first stage AC-DC converter. This results the reduction in controller complexity and better dynamic response as compared with conventional PR regulator.

Enhanced Control of Three-Phase Grid-Connected Renewables with Fault Ride-Through Capability under Voltage Sags

The uninterruptible operation of grid-connected renewables under the occurrence of grid voltage sags is addressed in this work. This is achieved due to the incorporation of an enhanced control algorithm of a renewable source. The low-voltage ride-through algorithm was developed in accordance to the voltage profile introduced by IEC 61400-21 regarding grid voltage sags. To guarantee continuous operation of the renewable agent during voltage sags, not only instantaneous reactive power but also instantaneous active power under moderate voltage sags was injected to the utility grid fulfilling grid code requirements. A dual second-order generalized integrator frequency-locked loop synchronization algorithm was used to estimate the system’s frequency, together with the positive and the negative sequences of the three-phase utility grid voltages when unbalanced sags occurred. The current control was made in a stationary reference frame by using proportional-resonant regulators, and a DC voltage source was used to emulate the primary energy from any type of renewable system. The validation of the proposed control algorithm was conducted for a three-phase grid-connected renewable system with an apparent power of 500 kVA. The results from several experimental tests demonstrated the proper behavior of the enhanced algorithm.

Power Supply and Reactive Power Compensation of a Single-Phase Higher Frequency On-Board Grid with Photovoltaic Inverter

The size reduction in on-board apparatuses in flying platforms, ships, and aerospace vehicles can be achieved by increasing the frequency of the on-board grid voltage. In the case of renewable powered platforms, a grid converter is used that has the primary task of feeding the generated energy into the on-board grid. The paper describes the developed control system of the grid converter, which, in addition to transferring the generated power to the single-phase grid, effectively compensates the reactive power occurring in it. The proposed structure of the proportional resonant regulator with finite gain that cooperates with the single-phase grid was discussed. The use of quadrature estimators of voltage and current enabled independent control of the active and reactive components of the current, thus compensating for the reactive power. The proposed control system structure was implemented on the FPGA platform and experimentally tested in steady state and dynamic condition considering grid disturbances and solar irradiance variations.

Comparison of Three Voltage Saturation Algorithms in Shunt Active Power Filters With Selective Harmonic Control

An array of proportional-resonant regulators is often used in shunt active power filters to control the grid currents and reduce the harmonic distortion caused by a distorting load. The voltage that is necessary to compensate for the current harmonics must be consistent with the available dc-link voltage. In this article, three adaptive algorithms for the exploitation of the dc-link voltage are developed and compared. These algorithms adaptively change the voltage saturation of each regulator to preserve the control capability of the fundamental component of the current when the available voltage is not enough to control the filter current. Simultaneously, they try to improve the quality of the grid current because the dc-link voltage of the active power filter is allocated to the regulators to compensate only the most significant harmonics. Some experimental results are shown to demonstrate the feasibility of the three algorithms.

Improved Control of Grid-connected DFIG-based Wind Turbine using Proportional-Resonant Regulators during Unbalanced Grid

The quality of power and current control are the greatest challenges of grid-connected wind farms during abnormal conditions. The negative- and positive-sequence components of the grid currents may be injected into a wind generation system during grid faults, which can affect the power stability and damage the wind system. The proposed work assures a low-voltage ride through capability of doubly-fed induction generator- based wind turbines under the grid voltage sag. A new technique to protect the wind system and to recompense the reactive power during failures of the utility grid according to the Spanish grid code is proposed. The control design is implemented to the power converters, and the grid current regulation is developed by using proportional-resonant regulators in a stationary two-phase (αβ) reference frame. The control performance is significantly validated by applying the real-time simulation for the rotor-side converter and the hardware in the loop simulation technique for the experiment of the generator’s grid-side converter control.

Unbalanced synchronous reference frame control of singe-phase stand-alone inverter

This paper presents harmonic damping schemes of the single-phase stand-alone inverter. The unbalanced synchronous reference frame technique is selected to control fundamental frequency voltage at the point of common coupling. The output voltage and the inductor current of the inverter are transformed to the unbalanced synchronous reference frame in which the proportional-integral regulators are used to force the error signals in the dq axes to zero. This control scheme does not require an orthogonal signal generator, and it is equivalent to the ideal proportional-resonant regulator. Harmonic regulators, orders 3rd, 5th, 7th, and 9th are added to minimize the voltage harmonics caused by the connected nonlinear load. The proposed controller is compared with the commonly-used multi-resonant controller. Simulation and experimental results of a 1.5-kVA inverter with the proposed control scheme exhibited excellent harmonic damping of the output voltage, caused by a highly nonlinear load and fast transient performance, which were better than the conventional resonant controller.

Power conditioning system control strategy for cascaded H‐bridge converter battery energy storage system

Large capability for a cascaded H-bridge converter battery energy storage system is one of the effective tools to solve the grid-connection problem of renewable energy resource such as large-scale wind farm. The power conditioning system (PCS) control strategy is used proportional-resonant regulator to implement the control with decoupled current control for instantaneous power. The balancing control of the state of charge (SOC) is divided into individual balancing control between bridges is implemented by means of the proportional controller and cluster control between three phases is based on the zero-sequence-voltage injection. The system designed in high-power medium voltage 6.6 kV combining 30 LiFePO 4 (lithium iron phosphate) battery units with cascaded H-bridge multilevel inverter. The simulation results of SOC balancing control was carried out. As a result, a steady-state error of PCS can be smaller and three-phase output power balancing has been achieved, thus, a system simulation model has verified the effectiveness of control strategy. The waveforms of PCS in quadrant operation show voltage and current at active power 1 MW.

Hardware realization of proportional-resonant regulator based advanced current control strategy for cascaded H-bridge inverter based shunt active power filter

Hardware realization of proportional-resonant regulator based advanced current control strategy for cascaded H-bridge inverter based shunt active power filter

Methodology for Analysis and Design of DiscreteTime Current Controllers for Three-Phase PWM Converters

In this work, a methodology for the analysis and design of robust, high bandwidth current controllers for three phase converters is presented. The overall goal is to demonstrate how the proposed model based control structure and the design methodology lead to an optimized digital current controller that exhibits fast and smooth dynamics as well as an excellent disturbance rejection ability. First, accurate discrete time models are derived and used to review classical current control from the perspective of the synchronous and stationary reference frame. Then, implementation options for the synchronous frame proportional integral (SFPI) regulator and the proportional resonant (PR) regulator are discussed and systematically compared in the stationary frame leading to the formulation of a general controller framework based on space vector resonators. It embodies multiple complex resonators and can represent the SFPI regulator, the PR regulator and beyond that any higher order regulator structure. For this framework, a step by step design procedure based on the complex root locus is proposed that allows an insightful optimization of its feedback gains. Finally, the performance of the presented control design techniques is evaluated experimentally.

An Experimental Assessment of Open-Phase Fault-Tolerant Virtual-Vector-Based Direct Torque Control in Five-Phase Induction Motor Drives

Direct torque control (DTC) has been recently used for the development of high-performance five-phase induction motor (IM) drives, where normal operation of the system has been usually considered and the ability of DTC to manage the situation has been analyzed in comparison with different rotor-field-oriented control (RFOC) strategies. The exploitation of fault-tolerant capabilities is also an interesting issue in multiphase machines, where the utility of RFOC controllers has been stated when the open-phase fault operation is considered. In this paper, the performance of DTC and RFOC controllers based on proportional resonant regulators and predictive control techniques is compared when an open-phase fault appears in a five-phase IM drive. Experimental tests are provided to compare the performance of the system using these control alternatives.

Stator current vector control strategy of doubly fed induction generator using proportional–resonant regulators

This study proposes the stator current vector control (VC) strategy of the doubly fed induction generator. It is implemented in the stator stationary reference frame without the phase-lock loop. As a result, the phase-locked loop is removed with a simplified structure. Then, in the stator stationary reference frame, the commanded stator current values are calculated on the basis of the instantaneous power theory. By this means, the calculations of the stator current references are irrelevant to the generator parameters. It can greatly reduce the parameter dependency of the control system. Since the currents, the voltages, and the flux linkages are ac signals, the control system would operate on the ac quantities. Then, for zero steady errors, proportional–resonant controllers, tuned at the nominal frequency, are employed to regulate the stator currents to track their commanded values. Finally, the simulation results are presented to validate the effectiveness of the proposed stator current VC strategy.

An Inductance Voltage Vector Control Strategy and Stability Study Based on Proportional Resonant Regulators under the Stationary αβ Frame for PWM Converters

The mathematical model of a three phase PWM converter under the stationary αβ reference frame is deduced and constructed based on a Proportional-Resonant (PR) regulator, which can replace trigonometric function calculation, Park transformation, real-time detection of a Phase Locked Loop and feed-forward decoupling with the proposed accurate calculation of the inductance voltage vector. To avoid the parallel resonance of the LCL topology, the active damping method of the proportional capacitor-current feedback is employed. As to current vector error elimination, an optimized PR controller of the inner current loop is proposed with the zero-pole matching (ZPM) and cancellation method to configure the regulator. The impacts on system's characteristics and stability margin caused by the PR controller and control parameter variations in the inner-current loop are analyzed, and the correlations among active damping feedback coefficient, sampling and transport delay, and system robustness have been established. An equivalent model of the inner current loop is studied via the pole-zero locus along with the pole placement method and frequency response characteristics. Then, the parameter values of the control system are chosen according to their decisive roles and performance indicators. Finally, simulation and experimental results obtained while adopting the proposed method illustrated its feasibility and effectiveness, and the inner current loop achieved zero static error tracking with a good dynamic response and steady-state performance.

Hybrid Pulsewidth Modulated Single-Phase Quasi-Z-Source Grid-Tie Photovoltaic Power System

A hybrid pulsewidth modulated single-phase quasi-Z-source grid-tie photovoltaic (PV) power system is proposed. The hybrid pulse-width modulation (HPWM) combines the pulse-width modulation (PWM) and the pulse-amplitude modulation (PAM). The PWM works when the ac output voltage is lower than the dc source voltage; otherwise, the PAM operates the single-phase quasi-Z-source inverter (qZSI). The HPWM leads to the reduction of power loss, and the quasi-Z-source capacitance and inductance. An effective control strategy is proposed for the new PV power system to manage the maximum power point tracking (MPPT) of PV panel, grid-tie power injection, and dc-link voltage. A grid-tie current controller, combining a repetitive controller and a proportional-resonant regulator, achieves strong harmonic suppression, fast dynamic, and zero tracking error. A 500-W prototype is built to verify the new system. Power loss estimation and impedance design are detailed. Experimental tests validate the HPWM, new PV power system with higher efficiency, and the related control method.

Current Zero-Crossing Duration Reduction of a Semicontrolled Open-Winding PMSG System Based on Third Harmonic Current Injection

The open-winding permanent-magnet synchronous generator (PMSG) fed by a semicontrolled converter is a promising configuration due to lower expense, simplified driving circuit, and reliable operation capability. When supplied by a common dc bus, the open-winding PMSG system can be more simplified. Because the voltage output by the diode converter is decided by the three-phase current polarity, the available voltage vector modulation range of the voltage source converter is limited. As a result, the current zero-crossing duration behavior is determined by the power factor angle, which will lead to zero-crossing voltage pulse disturbance, serious electromagnetic interference, and unexpected diode switching loss. This paper aims to reduce the current zero-crossing duration by injecting the third harmonic current into the zero-sequence current. A proportional resonant regulator is proposed to control the zero-sequence current. Finally, the proposed method is validated in a 1-kW semicontrolled open-winding PMSG experimental system.

An Efficient and Robust Hybrid Damper for <inline-formula> <tex-math notation="LaTeX">$LCL$</tex-math></inline-formula>- or <inline-formula> <tex-math notation="LaTeX">$LLCL$</tex-math></inline-formula>-Based Grid-Tied Inverter With Strong Grid-Side Harmonic Voltage Effect Rejection

A high-order ( $LCL$ or $LLCL$ ) power filter with a small grid-side inductor is becoming more preferred for a grid-tied inverter due to less total inductance and reduced costs. In a microgrid, the background harmonic voltage (BHV) may distort the injected currents of the grid-tied inverters. In order to resist the effect of the BHV, a feedforward voltage compensator and a proportional resonant regulator with harmonic compensation are often adopted. However, they still have their own limitations, particularly when there are higher order BHVs at the point of common coupling and when the equivalent grid impedance widely varies due to the different numbers of grid-tied inverters in parallel. Thus, an extra damper should be inserted to keep the system stable. In this paper, the control bandwidth limitation of a multiloop control active damping (AD) method is analyzed and illustrated by the capacitor-current-feedback AD. Based on this, a single-loop current control with a hybrid damper is proposed for a single-phase $LCL$ - or $LLCL$ -filter-based grid-tied inverter. A step-by-step design of the controller method is also introduced in detail. Experiments on a 2-kW prototype fully demonstrate the strong robustness of the stability and the high harmonic rejection ability of the inverter using the proposed control method.

Active Damping of LLCL Filters Using PR Control for Grid-Connected Three-Level T-Type Converters

In this paper, an active damping control scheme for LLCL filters based on the PR (proportional-resonant) regulator is proposed for grid-connected three-level T-type PWM converter systems. The PR controller gives an infinite gain at the resonance frequency. As a result, the oscillation can be suppressed at that frequency. In order to improve the stability of the system in the case of grid impedance variations, online grid impedance estimation is applied. Simulation and experimental results have verified the effectiveness of the proposed scheme for three-phase T-type AC/DC PWM converters.

PMSG Based WECS with PR Control Strategy for Grid Control

In this paper, a current feedback control scheme is proposed using Proportional Resonant (PR) for a grid-connected converter with an LCL Filter; PR controller with harmonic compensators has high gain at the desired frequencies for decrease harmonic distortion in the alternative voltage or current. Harmonic compensators of PR controller are limited to several low-order harmonics due to the system instability when the compensated frequency is out of system control loop’s bandwidth. The average value of current flow through inductors of LCL filter is feedback to the PR current regulator. Zero D-axis Control (ZDC) is to control the generator side converter to reduce the DC-link ripples, multi-loop harmonic current controllers are applied to regulate the higher-order harmonics by PR regulators. Consequently control strategy with LCL filter is to reduce third-order function to first-order function. By this way large control loop gain can be chosen to obtain control loop for the required harmonic components of the PR controller. The simulation and experimental results have been illustrated to validate the effectiveness of the proposed method in MATLAB Simulink.

Modelling, simulation and experimental verification for renewable agents connected to a distorted utility grid using a Real-Time Digital Simulation Platform

The large number of Photovoltaic plants and its utilization as agents of a Distributed Generation Systems justified the increasing efforts towards the optimal design of the overall grid-connected System. In a Distributed Generation environment the low voltage 3-phase utility grid could be affected by some disturbances such as voltage unbalanced, variations of frequency and harmonics distortion and it is mandatory that the control algorithms used in the inverter can be able to maintain the power flow between the renewable agent and the low voltage 3-phase utility grid; in addition a unitary power factor must be attained.A Proportional-Resonant regulator is used to performance a current control with the output current of the inverter and a Multiple Second Order Generalized Integrator Frequency-Locked Loop (MSOGI-FLL) is used to detect the frequency of the low voltage 3-phase utility grid. Some low order harmonics are introduced in the low voltage 3-phase utility grid in order to see the effect of the harmonic compensator.In order to validate the model of the Photovoltaic Renewable agent, the synchronization algorithm and the inverter control algorithm, some simulations using MATLAB/SIMULINK from The MathWorks, Inc. are shown firstly, and secondly, some Real-Time Digital Simulation tests using a Real-Time Digital Simulation (RTDS) Platform are carried out.