The series or parallel approach of passive resistors increases system damping to address the resonance problems inherent in LCL filters. As shown in Figure 1, the passive damping method of series resistance on the capacitor branch can attenuate the LCL resonant peak to a large extent, so that the amplitude-frequency curve is below the 0dB […]
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The three-phase inverter can be equivalent to two single-phase inverters with a coupling relationship after coordinate transformation. The research on the resonance problem can be carried out based on the single-phase grid-connected inverter model. In order to facilitate the subsequent description, Figure 1 shows a single-phase grid-connected inverter using an LCL filter. The LCL filter […]
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The overall control block diagram of the three-phase L-filter grid-connected inverter is shown in Figure 1. Among them, eabc and iabc represent the three-phase grid voltage and grid current, Udc is the DC bus voltage, and Ldbc is the grid-side inductance., iαβ is the component of the three-phase grid side current in the two-phase static αβ coordinate system, id*, iq* are […]
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In order to achieve lower harmonic distortion of grid-connected current, problems such as low-frequency harmonic distortion of grid-connected current must be solved. This article briefly analyzes the causes of low spectrum waves and introduces several current control methods for current suppression of low spectrum waves commonly used in L-filter solar grid tie inverter. Read more: Influence […]
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The previous analysis only considers the influence of the artificially added dead time on the output voltage of the bridge arm and the incoming current of the bridge arm to prevent the bridge arm from passing through. However, the turn-on and turn-off of actual power devices is not instantaneous, and there is a turn-on voltage […]
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1. The influence of low frequency harmonics of grid voltage The equivalent model of the grid-connected inverter is shown in Figure 1, in which the output voltage uinv of the bridge arm of the inverter is equivalent to a controlled voltage source (the specific form is related to the inverter control). Using the superposition theorem, […]
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In order to achieve a higher power factor, the fundamental tracking error of the incoming current must be resolved. This paper briefly introduces several fundamental current tracking control methods commonly used in L-filter grid-connected inverters 1. Proportional-integral (PI) regulator The form of the PI regulator is as follows: Among them, kp is the proportional gain, Ti is […]
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Overview of current control techniques for single L filter grid-tied inverters The current control block diagram of the single-L filter grid-connected inverter is shown in Figure 1. The inverter bridge is simply equivalent to a proportional link with a gain of kPWM, and kPWM is the ratio of the DC side voltage to the amplitude […]
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In the grid-connected situation, considering the line impedance and the inductive and resistive impedance existing in the actual power grid, Zload is equivalent to resistive-inductive. Therefore, the model established above and the voltage sharing control strategy discussed are also applicable to the half-bridge grid-connected inverter, the only difference being that Zload is a relatively small resistive and […]
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According to the equalization control idea of class B, the equalization control method based on the self-balancing characteristic is discussed below. According to the effect of closed-loop control on the self-balancing characteristics of 3L-NPC, in order to satisfy the idea of B-type equalizing control, the closed-loop control needs to meet two conditions under the action […]
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