US-12627149-B2 - Method of active and reactive power control in ABC frame of a grid-tied converter

US12627149B2US 12627149 B2US12627149 B2US 12627149B2US-12627149-B2

Abstract

A method for controlling active and reactive powers in grid-tied converters having a grid side and a battery side, in which said grid side supplies an alternative current to said converter whereas the battery side receives a direct current from said converter, said method comprising direct active and reactive power control in ABC frame where no transformation is used, and wherein active power is controlled by controlling the battery charging and discharging currents, and reactive power is controlled by controlling the phase shift between power factor correction current and voltage.

Inventors

Ahmed Rédha MEGHNOUS
Jean-Christophe CALAMOTE

Assignees

WATT & WELL

Dates

Publication Date: 20260512
Application Date: 20230331
Priority Date: 20220331

Claims (8)

1 . A grid-tied converter having a grid side that supplies an alternative current to the grid-tied converter, and a battery side that receives a direct current from the grid-tied converter, the grid-tied converter comprising: an AC/DC converter; and a bidirectional resonant DC/DC converter for controlling injection and absorption of grid side active and reactive powers by controlling direct active and reactive power injection or absorption from or to grid side in ABC frame where no DQ transformation is used, and wherein absorbed active power is controlled by controlling a battery charging current, and wherein injected active power is controlled by controlling discharging currents, and reactive power is controlled by controlling a phase shift angle between power factor correction current and voltage for each grid phase, wherein the bidirectional resonant DC/DC converter includes a full-bridge coupled to a resonant tank and a power transformer and rectifier stage, said full-bridge comprising a first pair of power switches S 1 /S 2 and a second pair of power switches S 3 /S 4 , the bidirectional resonant DC/DC converter being configured such that in a first mode of operation: switch S 1 and switch S 4 are driven by a same two pulse pattern with a phase shift β 1 , said two pulse pattern comprising a first pulse P 1 of width t 1 and a second pulse P 2 of width t 2 , P 1 and P 2 being separated by an off-time t 3 , and switch S 2 and switch S 3 are driven by a same single pulse pattern comprising pulse P 4 of width t 4 with a phase shift β 2 , wherein the grid-tied converter is configured to detect a grid configuration based on a grid side voltage and grid side angle measurement to determine a number of connected phases, and then automatically adapt a configuration of the grid-tied converter to the detected grid configuration.
2 . The grid-tied converter of claim 1 , further comprising a configurator having a detection system configured to detect the grid configuration between a single-phase grid configuration, a two-phase grid configuration, and a three-phase grid configuration.
3 . The grid-tied converter of claim 2 , wherein the configurator is provided with a system to configure a set of switches according to the detected grid configuration.
4 . The grid-tied converter of claim 1 , wherein: the grid side is a three-phase grid and/or a single-phase grid, and the grid-tied converter is configured as a single-phase converter or a three-phase converter selected automatically upon the detected grid configuration.
5 . The grid-tied converter of claim 1 , further comprising a switching bridge comprising a full bridge, coupled to a resonant tank, a transformer and a rectifier, and an output capacitor.
6 . The grid-tied converter of claim 1 , wherein the grid-tied converter is configured to operate as a single phase converter and/or a three-phase converter.
7 . The grid-tied converter of claim 6 , wherein a configuration of the grid-tied converter as a single-phase converter or a three-phase converter is automatically selected upon the detected grid configuration.
8 . A grid-tied converter having a grid side that supplies an alternative current to the grid-tied converter, and a battery side that receives a direct current from the grid-tied converter, the grid-tied converter comprising: an AC/DC converter; and a bidirectional resonant DC/DC converter having a full-bridge coupled to a resonant tank and a power transformer and rectifier stage, said full-bridge comprising a first pair of power switches S 1 /S 2 and a second pair of power switches S 3 /S 4 , the bidirectional DC/DC converter being operable for controlling: injection and absorption of grid side active and reactive powers by controlling direct active and reactive power injection or absorption from or to grid side in ABC frame where no DQ transformation is used, battery charging current to control the absorbed active power, discharging currents to control an injected active power, and a phase shift angle between power factor correction current and voltage for each grid phase to control reactive power, a detection system configured to detect a grid configuration based on a grid side voltage and a grid side angle measurement to determine a number of connected phases, wherein the grid-tied converter is configured to automatically adapt a configuration of the grid-tied converter to the detected grid configuration, wherein in a first mode of operation of the bidirectional DC/DC converter: switch S 1 and switch S 4 are driven by a same two pulse pattern with a phase shift β 1 , said two pulse pattern comprising a first pulse P 1 of width t 1 and a second pulse P 2 of width t 2 , P 1 and P 2 being separated by an off-time t 3 , and switch S 2 and switch S 3 are driven by a same single pulse pattern comprising pulse P 4 of width t 4 with a phase shift β 2 .

Description

CROSS-REFERENCE TO RELATED APPLICATIONS The present application claims priority 35 U.S.C. § 119 to European Patent Publication No. DE 102021210616.1 (filed on Mar. 31, 2022), the contents of which is hereby incorporated by reference in its complete entirety. TECHNICAL FIELD The present invention relates to power electronics, and in particular to grid-tied converters such as battery chargers, in particular for use with electrical vehicles. Battery chargers for use with electrical vehicles are composed of two power stages: an AC/DC converter and a DC/DC converter. The present invention relates in particular to a method for active and reactive power direct control in ABC frame of grid tied converters, in particular in relation with power factor correction in DC/DC converters. BACKGROUND Bidirectional battery chargers for electrical vehicles capable of Grid-to-Vehicle (G2V) and Vehicle-to-Grid (V2G) operations have attracted great interest these last years within smart grid applications. An accurate control of active and reactive powers remains necessary to ensure stable integration of a high number of chargers in smart and micro-grids. Most of existing control techniques are based on instantaneous power theory (commonly called «PQ theory») where dq frame transformation for three phase converters and then active and reactive powers control turns to direct and quadrature current control; this approach has been proposed by L. P. Sampaio et al. (“Grid-tie three-phase inverter with active and reactive power flow control capability”, published in Electrôn. Potôn., Campo Grande, v. 19, n. 4, p. 397-405 (2014)). PQ theory can also be adapted to single phase converters, as proposed by S. Peng, A. Luo, Z. Lv, J. Wu and L. Yu, “Power control for single-phase microgrid based on the PQ theory” (2011 6th IEEE Conference on Industrial Electronics and Applications, Beijing, 2011, pp. 1274-1277. The main drawback of these techniques is the utilization of the dq transformation that assumes that the grid is balanced. In case of imbalance, it is necessary to consider positive, negative and zero sequences of currents and voltages which means the transformation must be calculated three times and all control loops must be tripled. This has a huge impact on the CPU load of the employed digital controller or DSP, for computation and control implementation, where a more performant calculator is needed, which will increase the cost of the charger. The aim of the present invention is to propose a new control strategy that is capable of reducing the computation burden of the CPU and to use common power control strategy for single and three phase converters of battery chargers for electrical vehicles (EV). A known solution to this problem is based on the idea to control directly and in a decoupled way the active and reactive power exchanged by the inverter with the electrical grid, avoiding any current control; this is called Direct Power Control (DPC). A comparison of different control techniques using DPC is given in G. Giglia et al., «Comparison of Control Techniques for Three-Phase Distributed Generation Based on VOC and DPC», Renewable Energy and Power Quality Journal vol. 1 no 6, p. 659-666, (2008)(doi.org/10.24084/repqj06.401). The main disadvantage of DPC is that it is a hysteresis based control method, which causes problems related to electromagnetic compatibility (EMC) leading to unwanted chattering noise, significant harmonic content and high Total Harmonic Distortion (THD). As a consequence, DPC is not a satisfactory solution in many cases. SUMMARY According to the invention, the problem is solved by a method using direct active and reactive power control in ABC frame where no transformation is used. This reduces the computation burden and also enhances harmonic content by current shaping. The strategy is developed for a grid-tied charger comprising a bidirectional resonant DC/DC converter using Power Factor Correction (PFC) (see FIG. 1). More precisely, a first object of the invention is a method for controlling active and reactive powers in grid-tied converters, comprising direct active and reactive power control in ABC frame where no transformation is used, and wherein active power is controlled by controlling the battery charging and discharging currents, and reactive power is controlled by controlling the phase shift between PFC current and voltage. Another object of the invention is a circuit topology for carrying out said method. Active power is the real power transformed to actual physical work by the DC/DC stage load (EV battery); this is the power consumed by the battery upon charging or delivered by the battery to the grid. According to the invention, the active power control is achieved by controlling the battery charging and discharging currents. The reactive power control is achieved by controlling the phase-shift between PFC current and voltage at the AC side of the converter. This can be done through a linearize