Phase, amplitude and frequency of the utility voltage are critical information for the operation of the grid-connected inverter systems. In such applications, an accurate and fast detection of the phase angle, amplotude and frequency of the utility voltage is essential to assure the correct generation of the reference signals and to cope with the new upcoming standards. This paper presents a new phase-locked-loop (PLL) method for single-phase systems. The novelty consists in generating the orthogonal voltage system using a structure based on second order generalized integrator (SOGI). The proposed structure has the following advantages: — it has a simple implementation; — the generated orthogonal system is filtered without delay by the same structure due to its resonance at the fundamental frequency, — the proposed structure is not affected by the frequency changes. The solutions for the discrete implementation of the new proposed structure are also presented. Experimental results validate the effectiveness of the proposed method.

A New Single-Phase PLL Structure Based on Second Order Generalized Integrator

This paper deals with a fundamental aspect in the control of grid-connected power converters, i.e., the detection of the positive-sequence component at fundamental frequency of the utility voltage under unbalanced and distorted conditions. Accurate and fast detection of this voltage component under grid faults is essential to keep the control over the power exchange with the grid avoiding to trip the converter protections and allowing the ride-through of the transient fault. In this paper, the systematic use of well known techniques conducts to a new positive-sequence voltage detection system which exhibits a fast, precise, and frequency-adaptive response under faulty grid conditions. Three fundamental functional blocks make up the proposed detector, these are: i) the quadrature-signals generator (QSG), ii) the positive-sequence calculator (PSC), and iii) the phase-locked loop (PLL). A key innovation of the proposed system is the use of a dual second order generalized integrator (DSOGI) to implement the QSG. For this reason, the proposed positive-sequence detector is called DSOGI-PLL. A detailed study of the DSOGI-PLL and verification by simulation are performed in this paper. From the obtained results, it can be concluded that the DSOGI-PLL is a very suitable technique for characterizing the positive-sequence voltage under grid faults.

New positive-sequence voltage detector for grid synchronization of power converters under faulty grid conditions

Active power decoupling methods are developed to deal with the inherent ripple power at twice the grid frequency in single-phase systems generally by adding active switches and energy storage units. They have obtained a wide range of applications, such as photovoltaic (PV) systems, light-emitting diodes (LEDs) drivers, fuel cell (FC) power systems, and electric vehicle (EV) battery chargers, etc. This paper provides a comprehensive review of active power decoupling circuit topologies. They are categorized into two groups in terms of the structure characteristics: independent and dependent decoupling circuit topologies. The former operates independently with the original converter, and the latter, however, shares the power semiconductor devices with the original converter partially and even completely. The development laws for the active power decoupling topologies are revealed from the view of “duality principle,” “switches sharing,” and “differential connection.” In addition, the exceptions and special cases are also briefly introduced. This paper is targeted to help researchers, engineers, and designers to construct some new decoupling circuit topologies and properly select existing ones according to the specific application.

Review of Active Power Decoupling Topologies in Single-Phase Systems

Phase angle, frequency and amplitude of the utility voltage vector are basic information for an increasing number of grid-connected power conditioning equipments, such as PWM rectifiers, uninterruptible power systems (UPS), voltage sag compensators and the emerging distributed generation systems. For these applications, accurate tracking of the utility voltage vector is essential to ensure correct operation of the control system. This paper presents a comparative study of synchronous reference frame PLL algorithms for single-phase systems. Simulation and experimental results, including operation of the PLL structures under distorted utility conditions are presented, to allow a performance evaluation of the PLL algorithms.

Performance evaluation of PLL algorithms for single-phase grid-connected systems

In this paper, a control strategy of the single-phase active filter using a novel d-q transformation is proposed This d-q transformation is implemented by using Hilbert transform, by which the instantaneous single-phase voltage and current are converted into complex vectors (analytic signals) on the instantaneous basis Since the fundamental components of voltages and currents are converted into DC components on the d-q coordinate both in the steady and transient states, the harmonics of voltages and currents can be obtained precisely through the low-pass filer installed on the d-q coordinate This results in the economical active filter with a small capacitor suppressing the DC bus voltage fluctuation because the fundamental power can be fully removed from the active filter input

http://azarrobot.persiangig.com/document/power%20filter/1%20phase%20APF.pdf

A control strategy of single-phase active filter using a novel d-q transformation

This paper deals with a new approach for single to three phase matrix converters. In almost all of these converters, three-phase voltages and currents are distorted because of the inherent fluctuation of single-phase instantaneous power. On the contrary, in our proposed matrix converter, that fluctuation is compensated for and three phase voltages and currents can be controlled to be pure sine wave. Our circuit is composed of the conventional single to three-phase matrix converter circuit, an AC reactor and three bi-directional switches. By using the single-phase instantaneous active and reactive power theory (ps-qs theory), the ripple component of the single-phase instantaneous power is detected and is sorted in the AC reactor. Some significant characteristics are verified by means of a simulation with a 200 V/3.7 kW PM motor.

A single to three phase matrix converter with a power decoupling capability

This paper deals with a fast dc voltage control strategy for a single-phase PWM rectifier. The PWM rectifier must control the active and reactive powers for regulating the dc voltage. Then, in this paper, a single-phase instantaneous active/reactive power theory (the ps-qs theory) is applied to a control strategy of a single-phase PWM rectifier. In addition, the stability of a single-phase PWM rectifier is analyzed, and a novel circuit topology and control strategy using a dc active filter is proposed. Some significant characteristics on our proposal are verified by using a 100 V/1.8 kVA experimental system.

Modeling and control strategy for a single-phase PWM rectifier using a single-phase instantaneous active/reactive power theory

The present paper deals with a single- to three- phase matrix converter with a power decoupling capability. This capability is available in not only the steady state but also the transient state. The proposed converter can then control induction motors without torque vibration. The proposed circuit and control diagrams and some important simulation results are described in the present paper.

A Single- to Three-Phase Matrix Converter for a Vector-Controlled Induction Motor

Expansion of voltage distortions along with power distribution systems, which is referred to as the harmonic propagation, is pointed out. This is caused by the LC resonances between the distribution line inductances and the power capacitors. This paper presents a modeling and harmonic suppression procedure for power distribution systems. In our proposal, a power distribution system is analyzed using the modal analysis and is represented by a reduced order model. For the harmonic suppression, a series active filter is used and its controller is designed based on the reduced order model. Some significant characteristics are verified by using a single-phase simulated full order model.

N. Matsui

Papers

A control strategy of single-phase active filter using a novel d-q transformation

A single to three phase matrix converter with a power decoupling capability

Modeling and control strategy for a single-phase PWM rectifier using a single-phase instantaneous active/reactive power theory

A Single- to Three-Phase Matrix Converter for a Vector-Controlled Induction Motor

Modeling and harmonic suppression for distribution systems