Research on Current Control Strategy of the LCL-Type Grid-Connected Inverter Based on State Reconfiguration With Quasi Resonant-Extended State Observer

doi:10.12096/j.2096-4528.pgt.22141

Abstract

Abstract:

The LCL-type grid-connected inverter (GCI) is a critical device for realizing energy transmission between distributed generation and the power grid. The current control of the GCI typically requires multiple sensors to enable active damping and grid-side current control, which increases the system cost. A full-state observation system based on state reconfiguration with quasi resonant-extended state observer was proposed, in which just a signal inverter-side inductor current sensor was required to realize real-time observation of the desired state variables. Meanwhile, the constraint of high observer bandwidth required for conventional extended state observer to track sinusoidal signals was solved by adding a quasi resonant link to the observation channel of each state variable of extended state observer. Moreover, the active disturbance rejection control current controller was designed in the dq frame, which simplified the complicated decoupling process of conventional methods by treating the coupling as part of the total disturbance. The software numerical simulation illustrates that the control strategy show excellent observation results and current tracking performance.

Key words: LCL-type grid-connected inverter, state reconfiguration, quasi resonant-extended state observer, active damping, current decoupling control

CLC Number:

TM 464

Jian FANG, Hui LI. Research on Current Control Strategy of the LCL-Type Grid-Connected Inverter Based on State Reconfiguration With Quasi Resonant-Extended State Observer[J]. Power Generation Technology, 2024, 45(1): 170-179.

Figures/Tables 15

Fig. 1 Structure of three-phase LCL-type grid-connected inverter system

Fig. 2 Current control of GCI based on state reconfiguration with QR-ESO

Fig. 3 Flow diagram of control strategy

Fig. 4 Internal structure of QR-ESO

Fig. 5 Low-order ADRC current controller structure

Tab. 1 Main circuit parameters

参数	数值	参数	数值
直流母线电压U_dc/V	700	网侧电感 L_g/mH	2.5
电网电压u_g/V	220	逆变器侧电感 L_i/mH	5
电网频率f_g/Hz	50	滤波电容C/μF	20

Tab. 2 Controller parameters

参数	数值
状态重构QR-ESO的b₀	4×10⁹
状态重构QR-ESO的ω_o	2×10³
ADRC的b	2×10²
ADRC的 $ω ̂ o$	1.5×10³
ADRC的 $ω ̂ c$	6×10²
比例系数K_p	5.6×10⁰
积分系数K_i	1.87×10³
滤波电容电流有源阻尼系数H	2×10¹
准谐振环节当中的T₁	1×10¹
准谐振环节当中的T₂	1×10^-1

Tab. 2 Controller parameters

参数	数值
状态重构QR-ESO的b₀	4×10⁹
状态重构QR-ESO的ω_o	2×10³
ADRC的b	2×10²
ADRC的 $ω ̂ o$	1.5×10³
ADRC的 $ω ̂ c$	6×10²
比例系数K_p	5.6×10⁰
积分系数K_i	1.87×10³
滤波电容电流有源阻尼系数H	2×10¹
准谐振环节当中的T₁	1×10¹
准谐振环节当中的T₂	1×10^-1

Fig. 6 Comparison of ESO and QR-ESO observations

Fig. 7 Observation effects under parameter perturbations and grid voltage fluctuations

Fig. 8 Observation effects in the presence of harmonics in the grid voltage

Fig. 9 Observation effects in the presence of harmonics in grid-side currents

Fig. 10 Effect of current control of dq frames under normal working conditions

Fig. 11 Effect of dq frames current control under grid voltage fluctuation conditions

Fig. 12 Comparison of system open-loop Bode diagrams

Fig. 13 Comparison of system closed-loop Bode diagrams

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