Reactive Current Detection Method Research Articles

Improved ip-iq Reactive Current Detection Method Without PLL

As the traditional d-q transformation method is not sufficient in detecting the three-phase asymmetric components, a new detection method in which a single phase voltage is input to a differentiator to get an orthogonal differential is proposed. The synchronous rotary angle can be obtained by using the orthogonality relationship based on mathematical relationship. The new detection method is suitable for both asymmetric load and asymmetric supply voltage systems. The effect of time delay caused by phase-locked loop (PLL) is eliminated without using PLL circuit to obtain synchronous rotation angle in the detection process. The phase shifting deviation is solved without shifting the phase of three-phase current. The unbalance degree of input voltage in Static Synchronous Compensator (STATCOM) is effectively reduced by using this method. Simulation and experiment results show that the proposed method is valid and feasible.

Improved Reactive Current Detection Method of SVG

The static VAR generator (SVG) is an important device in flexible AC transmission systems (FACTS) for the development of smart grids. Based on the basis principle of SVG and instantaneous reactive power theory, the conventional ip–iq and dq methods have a certain error when the three phase voltages are unbalanced. In this paper, the current detection algorithm is improved in cases of three-phase power asymmetry by using the fundamental positive-sequence reactive current instead of the voltage as the input of phase locked loop (PLL). So the problems caused by unbalanced three-phase voltages could be avoided. In addition, a moving average filter is designed to improve the performance of the detection accuracy and dynamic response. Experiments verify the correctness and effectiveness of the proposed scheme.

Fast reactive current detection method for single‐phase grid‐connected inverters

This study presents a fast reactive current detection (RCD) method based on closed-loop resonant filter for single-phase grid-connected inverters. The developed closed-loop resonant filter-based RCD (CLRF-RCD) technique with shorter time delay can enhance the dynamic performance of reactive current detection, which is beneficial for achieving faster reactive current compensation and/or reactive power regulation in single-phase grid-connected power systems. The optimal design of CLRF-RCD is presented in detail, together with the comparison of CLRF-RCD with the conventional second-order generalised integrator-based RCD. Finally, the simulation and experimental results validate the feasibility of the developed CLRF-RCD algorithm.

An Improved Reactive Current Detection and Power Control Method for Single-Phase Photovoltaic Grid-Connected DG System

In the single-phase photovoltaic (PV) grid-connected distributed generation (DG) system located at the end of the feeder, it is necessary to provide quickly active and reactive power to the local loads. In this paper, an improved reactive current detection and power control method are proposed to realize active power control and reactive power compensation. To detect quickly the loads reactive current, a fast reactive current detection method using the derivative and i <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p</sub> -i <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">q</sub> algorithm is presented, and it can overcome the long delay in a conventional phase-shift method. In the inner current loop, the quasi-proportional-resonant (QPR) control method with grid voltage feed-forward is presented to control accurately the grid current with zero steady error, and to reduce the current distortion due to the frequency offset and distortion of the grid voltage. The inner loop stability is analyzed, and the proper parameters are selected. In the outer loop, proportional-integrator (PI) controller is applied to stabilize the dc-link voltage, and power feed-forward is introduced to speed up system response. Simulation and experimental results verified the validity of the proposed control method.

Robust predictive dual‐loop control strategy with reactive power compensation for single‐phase grid‐connected distributed generation system

A robust predictive dual-loop control strategy with reactive power compensation is proposed for single-phase gridconnected distributed generation (DG) system located at the end of the feeder. The proposed control strategy mainly includes improved reactive current detection and robust predictive dual-loop control. To reduce the long time delay in the conventional reactive current detection, the improved reactive current detection method based on the derivative and i p - i q algorithm is presented. In the inner current loop, a robust predictive deadbeat control (RPDC) is proposed to reduce the control delay in digital signal processor, and also enhances system robustness due to the filter inductance mismatch. In the outer loop, proportional-integral controller is applied to stabilise the dc-link voltage, and power feedforward is used to speed up the system response. In z-domain, the stability of RPDC is discussed, and the proper parameters are selected. Simulation and experimental results verified the validity of the proposed strategy.