Harmonic Suppression and Stability Enhancement for Parallel Multiple Grid-Connected Inverters Based on Passive Inverter Output Impedance

Qian, Qiang; Xie, Shaojun; Huang, Liuliu; Xu, Jinming; Zhang, Zhao; Zhang, Binfeng

doi:10.1109/tie.2017.2711526

Cited by 92 publications

(34 citation statements)

References 27 publications

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“…Based on [18]- [21], the ratio of Z g and Z out must satisfy the Nyquist Criterion by counting the number of ±180 • −crossings in the frequency range with gains above 0dB.…”

Section: B Inverter Output Impedance Modelingsmentioning

confidence: 99%

“…The system parameters used in this study are given in Table 1. As proved by [21] and [33], reducing G f (s) is helpful to improve the robustness of the system, while the harmonic resonant controller with phase compensation (HQR-PC) can effectively suppress the low-order current harmonics and improve the phase of the system. Following [21], the feedforward factor G f (s) is selected as 0.6, and G c (s) is expressed as:…”

Section: A Controllers and Parametersmentioning

confidence: 99%

“…As proved by [13], [14], the LCL resonance damping, the harmonic resonant controller and the PCC voltage feedforward could all cause the instability due to many reasons, such as the reduction of resonance frequency, the bandwidth reduction and the extra feedback loop related to the PCC feedforward. Thus, for the weak grid applications, the robust or adaptive methods are proposed, e.g., the robust AD in [14]- [16], the robust controllers in [17]- [19], the robust voltage feedforward based on impedance shaping in [20], [21], the adaptive algorithms based on the impedance estimation in [13], [22], [23], and the adaptive feedforward without the grid impedance estimation in [24]. As above studies proved, the harmonics at several hundreds of Hz to several kHz (usually, much higher than the PLL bandwidth) can be solved.…”

Section: Introductionmentioning

confidence: 99%

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Robustness Improvement of Single-Phase Inverters Under Weak Grid Cases by Adding Grid Current Feedforward in Delay-Based Phase-Locked Loop

Bian

Qian

et al. 2020

IEEE Access

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For inverters, a phase-locked loop (PLL) is usually needed for the grid synchronization. Typically, for the single-phase inverters, the orthogonal-signal-generators based PLLs (e.g., delay-based PLL) can be used. However, if the grid at the point of common coupling (PCC) exhibits a large grid impedance, the inverter may not work well or even be unstable. In order to work satisfactorily in the very weak grid, this study aims to formulate a robust PLL. At first, by modeling the inverter output impedance and considering the frequency coupling effect, the stability of the typical delay-based PLL has been analyzed and the reason for the performance degradation has been explained. Then, based on analyzing the differences of PLL blocks under different PCC conditions, the robust PLL with the grid current feedforward is discussed. Compared with the typical PLL, the improvement of the system behaviors in the weak grid cases is mainly attributed to the extra term on the numerator of output impedance, which is introduced by the current feedforward of the proposed PLL. The selection of control parameters has been emphasized for maintaining the high robustness. At last, selected comparative waveforms have verified that the single-phase inverter can perform well even with the large grid impedance, without the grid impedance estimation.

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“…Based on [18]- [21], the ratio of Z g and Z out must satisfy the Nyquist Criterion by counting the number of ±180 • −crossings in the frequency range with gains above 0dB.…”

Section: B Inverter Output Impedance Modelingsmentioning

confidence: 99%

Section: A Controllers and Parametersmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Robustness Improvement of Single-Phase Inverters Under Weak Grid Cases by Adding Grid Current Feedforward in Delay-Based Phase-Locked Loop

Bian

Qian

et al. 2020

IEEE Access

Self Cite

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“…However, in these studies, the harmonics introduced by the mutual current were not considered. In [13], the mutual current harmonics were investigated. The harmonics were divided into the low-and high-frequency components.…”

Section: Literature Reviewmentioning

confidence: 99%

Active Disturbance Rejection Control Scheme for Reducing Mutual Current and Harmonics in Multi-Parallel Grid-Connected Inverters

Saleem

Kim

et al. 2019

Energies

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With the increasing penetration of renewable energy sources into modern power systems, parallel inverters with LCL filters are commonly employed in the grid interface, giving rise to potential resonance problems. Among the different resonances, interactive resonance is triggered by interaction among inverters when different current references are applied to parallel inverters. It may also feature a mutual current that circulates among inverters instead of flowing into the grid and introduces harmonics or instability in the control system. In this paper, active disturbance rejection control based on a reduced-order extended state observer (RESO) was proposed for parallel inverters. With the proposed scheme, the interaction between inverters is considered as an exogenous disturbance caused by other parallel inverters, estimated by the RESO, and rejected by the controller. In the results, the mutual current and interactive harmonics, calculated via fast Fourier transform, were reduced with the proposed control scheme. Thus, the lower total harmonic distortion of each current was achieved. Additionally, the robust stability and less model-dependent control design are the other additive advantages over the derivative filtered capacitor voltage feedforward-based active damping using PI control. The simulation and real-time experimental results of the conventional and proposed scheme, obtained using the hardware-in-loop, were presented to verify the theoretical analysis under the similar and different current reference cases.

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“…TPPII is widely used in large-capacity energy storage system (ESS), uninterruptible power supply (UPS) and motor drive applications [1][2][3][4]. Generally, to control the current of TPPII, the output current that composes each inverter's phase current is detected [5].…”

Section: Introductionmentioning

confidence: 99%

A Current Reconstruction at Parallel Three Phase Inverters Using Two Current Sensors

et al. 2019

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In this paper, a current restoration method which can be applied to three phase parallel interleaved inverters (TPPII) using two current sensors has been proposed. In the proposed current reconstruction method, the branch current and the phase current of the two phases of the TPPII are sampled concurrently at the peak and valley of the pulse width modulation (PWM) carrier using two hall-effect sensors. Then, the phase current of each inverter is reconstructed by analyzing the sensed current with the current conduction path information according to the switch state in the peak and valley of the PWM carrier. This paper additionally analyzes the characteristics of the offset occurring in the detection process of two current sensors and it proposes a compensation method to reduce the offset on-line. In order to at once reduce the offset of the three-phase recovery current caused by the DC offset of the sensor, a coordinate conversion method and a low pass are used. To verify the performance of the proposed current recovery method and real-time offset compensation method, a simulation using PSIM software was performed, and experiments were conducted using a three phase parallel inverter composed of insulated gate bipolar transistor (IGBT) modules. In particular, the AC offset that occurred in the sampling process during the experiment was analyzed and modeled, and it was reduced by simple calculation.

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Harmonic Suppression and Stability Enhancement for Parallel Multiple Grid-Connected Inverters Based on Passive Inverter Output Impedance

Cited by 92 publications

References 27 publications

Robustness Improvement of Single-Phase Inverters Under Weak Grid Cases by Adding Grid Current Feedforward in Delay-Based Phase-Locked Loop

Robustness Improvement of Single-Phase Inverters Under Weak Grid Cases by Adding Grid Current Feedforward in Delay-Based Phase-Locked Loop

Active Disturbance Rejection Control Scheme for Reducing Mutual Current and Harmonics in Multi-Parallel Grid-Connected Inverters

A Current Reconstruction at Parallel Three Phase Inverters Using Two Current Sensors

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