Stationary frame current regulation of PWM inverters with zero steady state error
01 Jul 1999-Vol. 2, pp 1185-1190
TL;DR: In this paper, a new type of stationary frame controller is proposed, which achieves the same steady state performance as a synchronous frame controller, and is applicable to both single phase and three phase inverters.
Abstract: Current regulators for AC inverters are commonly categorised as hysteresis, linear PI or deadbeat predictive, with a further subclassification into stationary ABC frame and synchronous DQ frame implementations. Synchronous frame controllers are generally accepted to have a better performance than stationary frame controllers do, as they operate on DC quantities and hence can eliminate steady state errors. This paper establishes a theoretical connection between these two classes of regulators and proposes a new type of stationary frame controller, which achieves the same steady state performance as a synchronous frame controller. The new controller is applicable to both single phase and three phase inverters.
Citations
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TL;DR: An overview of the structures for the DPGS based on fuel cell, photovoltaic, and wind turbines is given and the possibility of compensation for low-order harmonics is discussed.
Abstract: Renewable energy sources like wind, sun, and hydro are seen as a reliable alternative to the traditional energy sources such as oil, natural gas, or coal. Distributed power generation systems (DPGSs) based on renewable energy sources experience a large development worldwide, with Germany, Denmark, Japan, and USA as leaders in the development in this field. Due to the increasing number of DPGSs connected to the utility network, new and stricter standards in respect to power quality, safe running, and islanding protection are issued. As a consequence, the control of distributed generation systems should be improved to meet the requirements for grid interconnection. This paper gives an overview of the structures for the DPGS based on fuel cell, photovoltaic, and wind turbines. In addition, control structures of the grid-side converter are presented, and the possibility of compensation for low-order harmonics is also discussed. Moreover, control strategies when running on grid faults are treated. This paper ends up with an overview of synchronization methods and a discussion about their importance in the control
4,655 citations
Cites background from "Stationary frame current regulation..."
...Moreover, high dynamic characteristics of PR controller have been reported in different works [39], [40]....
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...Proportional resonant (PR) controller [36]–[39] gained a large popularity in the last decade in current regulation of grid-tied systems....
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09 Oct 2006
TL;DR: The proportional-resonant (PR) controllers and filters, and their suitability for current/voltage control of grid-connected converters, are described in this article.
Abstract: The recently introduced proportional-resonant (PR) controllers and filters, and their suitability for current/voltage control of grid-connected converters, are described. Using the PR controllers, the converter reference tracking performance can be enhanced and previously known shortcomings associated with conventional PI controllers can be alleviated. These shortcomings include steady-state errors in single-phase systems and the need for synchronous d-q transformation in three-phase systems. Based on similar control theory, PR filters can also be used for generating the harmonic command reference precisely in an active power filter, especially for single-phase systems, where d-q transformation theory is not directly applicable. Another advantage associated with the PR controllers and filters is the possibility of implementing selective harmonic compensation without requiring excessive computational resources. Given these advantages and the belief that PR control will find wide-ranging applications in grid-interfaced converters, PR control theory is revised in detail with a number of practical cases that have been implemented previously, described clearly to give a comprehensive reference on PR control and filtering.
1,483 citations
TL;DR: In this article, a power control strategy for a low-voltage microgrid is proposed, where the mainly resistive line impedance, the unequal impedance among distributed generation (DG) units, and the microgrid load locations make the conventional frequency and voltage droop method unpractical.
Abstract: In this paper, a power control strategy is proposed for a low-voltage microgrid, where the mainly resistive line impedance, the unequal impedance among distributed generation (DG) units, and the microgrid load locations make the conventional frequency and voltage droop method unpractical. The proposed power control strategy contains a virtual inductor at the interfacing inverter output and an accurate power control and sharing algorithm with consideration of both impedance voltage drop effect and DG local load effect. Specifically, the virtual inductance can effectively prevent the coupling between the real and reactive powers by introducing a predominantly inductive impedance even in a low-voltage network with resistive line impedances. On the other hand, based on the predominantly inductive impedance, the proposed accurate reactive power sharing algorithm functions by estimating the impedance voltage drops and significantly improves the reactive power control and sharing accuracy. Finally, considering the different locations of loads in a multibus microgrid, the reactive power control accuracy is further improved by employing an online estimated reactive power offset to compensate the effects of DG local load power demands. The proposed power control strategy has been tested in simulation and experimentally on a low-voltage microgrid prototype.
1,060 citations
Additional excerpts
...For the voltage loop, the P + resonant controllers in the form of (10) are employed in the α–β frame [20]–[22]...
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TL;DR: In this paper, the authors analyze the stability problems of grid connected inverters used in distributed generation and demonstrate that the use of active damping helps to stabilise the system in respect to many different kinds of resonances.
Abstract: The aim of this paper is to analyze the stability problems of grid connected inverters used in distributed generation. Complex controllers (e.g., multiple rotating dq-frames or resonant-based) are often required to compensate low frequency grid voltage background distortion and an LCL-filter is usually adopted for the high frequency one. The possible wide range of grid impedance values (distributed generation is suited for remote areas with radial distribution plants) challenge the stability and the effectiveness of the LCL-filter-based current controlled system. It has been found out and it will be demonstrated in this paper that the use of active damping helps to stabilise the system in respect to many different kinds of resonances. The use of active damping results in an easy plug-in feature of the generation system in a vast range of grid conditions and in a more flexible operation of the overall system able to manage sudden grid changes. In the paper, a vast measurement campaign made on a single-phase system and on a three-phase system used as scale prototypes for photovoltaic and wind turbines, respectively, validate the analysis.
997 citations
Cites background or methods from "Stationary frame current regulation..."
...5-Hz variation of the grid frequency are to be considered acceptable [15]....
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...oped, for active rectifiers and filters [15], to null the harmonics caused by the grid voltage background distortion in the grid current....
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...The adopted current controller is based on a Proportional Resonant (PR) structure [14], [15] where second-order generalized integrators (GI) are used to achieve zero steady-state error....
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...the harmonic compensators have influence only in the low frequency range [15], their zeros and poles will be omitted in the following analysis for the sake of simplicity....
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...As discussed in [15] the resonant controllers have influence only on the frequency they compensate and very little on the dynamics and stability....
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08 Oct 2000
TL;DR: In this paper, the authors proposed several concepts of integrators for sinusoidal signals, including parallel and series associations of the basic PI units using the stationary frame generalized integrators, for current control of active power filters.
Abstract: The paper proposes several concepts of integrators for sinusoidal signals. Parallel and series associations of the basic PI units using the stationary frame generalized integrators are used for current control of active power filters. Zero steady state error for the concerned current harmonics are realized, with reduced computation, under unbalanced utility or load conditions. Designing of the PI constants, digital realization of the generalized integrators, as well as compensation of the computation delay etc. are studied. Extensive test results from a 10 kW active power filter prototype are demonstrated.
838 citations
References
More filters
TL;DR: Current control techniques for three-phase voltage-source pulsewidth modulated converters, including bang-bang (hysteresis, delta modulation) controllers and predictive controllers with on-line optimization are reviewed.
Abstract: The aim of this paper is to present a review of current control techniques for three-phase voltage-source pulsewidth modulated converters. Various techniques, different in concept, have been described in two main groups: linear and nonlinear. The first includes proportional integral (stationary and synchronous) and state feedback controllers, and predictive techniques with constant switching frequency. The second comprises bang-bang (hysteresis, delta modulation) controllers and predictive controllers with on-line optimization. New trends in current control-neural networks and fuzzy-logic-based controllers-are discussed, as well. Selected oscillograms accompany the presentation in order to illustrate properties of the described controller groups.
2,086 citations
TL;DR: In this article, the inherent limitations of commanding voltages and currents in a three-phase load with an inverter are examined, and an overview of several current controllers described in the literature is presented, and computer simulations are used to compare performance.
Abstract: The inherent limitations of commanding voltages and currents in a three-phase load with an inverter are examined. An overview of several current controllers described in the literature is presented, and computer simulations are used to compare performance. A switching diagram is developed which reveals some of the operating characteristics of hysteresis controllers. For ramp comparison controllers, a frequency transfer function analysis is used to predict the line currents and provide some insight into the compensation required to reduce the current errors.
889 citations
08 Oct 2000
TL;DR: In this paper, the authors proposed several concepts of integrators for sinusoidal signals, including parallel and series associations of the basic PI units using the stationary frame generalized integrators, for current control of active power filters.
Abstract: The paper proposes several concepts of integrators for sinusoidal signals. Parallel and series associations of the basic PI units using the stationary frame generalized integrators are used for current control of active power filters. Zero steady state error for the concerned current harmonics are realized, with reduced computation, under unbalanced utility or load conditions. Designing of the PI constants, digital realization of the generalized integrators, as well as compensation of the computation delay etc. are studied. Extensive test results from a 10 kW active power filter prototype are demonstrated.
838 citations
TL;DR: In this article, a detailed model for the stationary and synchronous sine-triangle current regulators is presented, and the results demonstrate the limitations of the two most often used current regulators and the robustness of the synchronous current regulator.
Abstract: Detailed models are presented for the stationary and synchronous sine-triangle current regulators. Analytical and test results are compared for purposes of model verification and regulator evaluation. The results demonstrate the limitations of the two most often used current regulators and the robustness of the synchronous current regulator. The stationary sine-triangle and hysteretic current regulators are shown to have steady-state characteristics that depend on slip, operating frequency, and motor impedance. In contrast the synchronous regulator, because it lacks these dependencies, exhibits ideal steady-state current regulator characteristics without sacrificing bandwidth. Moreover, the complexities traditionally associated with the synchronous regulator are overcome with a simple equivalent implementation.
472 citations
TL;DR: In this paper, a new current control method based on the internal model principle in control theory is proposed for tracking an arbitrary number of harmonics: a DC component or fundamental frequency component signal.
Abstract: A new current control method based on the internal model principle in control theory is proposed. It introduces a sinusoidal internal model into the control system. It does not use any coordinate transformations. The method can be used for tracking an arbitrary number of harmonics: a DC component or fundamental frequency component signal. It is applied to a single-phase pulsewidth modulation inverter and active filter. The validity is confirmed by simulation and experimental results.
307 citations