Design example of LCL filter

A calculation method of ripple current was given in the design of a single inductance filter in the previous article, and another method of calculation of ripple current will be introduced here. Also considering that the prototype adopts the unipolar SPWM strategy, the expression of the bridge arm output voltage Uinv is Among them, M is […]

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The structure and design basis of LCL filter

The structure of the LCL filter The filtering capability of a single inductor is limited and the volume and loss are relatively large. However, the LCL type filter has the advantages of small size and low loss, and is widely used in grid-connected inverters. The grid-connected inverter structure using LCL filter is shown in Figure […]

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Overview of the network filter and the parameter design of L filter

Overview of the network filter The PWM modulation of the grid inverter leads to a large number of switching frequency and its multiplier harmonic voltages in the output voltage of the bridge arm, and finally leads to corresponding harmonic currents in the grid current. However, in order to make the grid-connected inverter friendly to the […]

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Leakage current suppression of three-phase grid-connected inverter

The previous article analyzed the analysis and improvement of leakage current analysis model, leakage current suppression methods and various topologies based on single-phase non-isolated photovoltaic grid-connected inverters, but the summarized leakage current model and suppression approach can also be analogized to a three-phase grid-connected inverter. Topology using inhibitory pathway A 1. Add an isolation transformer Like […]

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Construction of single-phase non-isolated bridge inverter topology

From the previous analysis, it is known that the suppression approach A is to increase the common-mode loop impedance and reduce the high-frequency leakage current in the case of high-frequency changes in the common-mode voltage. The suppression pathways B and C eliminate the high-frequency voltage of the common-mode loop to eliminate the leakage current. Compared […]

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Bridge inverter topology with suppression path C

1. Half-bridge inverter topology In Figure 1, if the bridge arm 1 is a capacitor branch and the bridge arm 2 is a power tube, it constitutes a single-phase half-bridge inverter circuit. The driving logic is shown in Figure 3, that is, the upper and lower tubes of the bridge arm 2 are turned on […]

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Bridge type inverter topology adopting suppression path B

1. Adopt bipolar SPWM full-bridge inverter Commonly used SPWM strategies for single-phase full-bridge grid-connected inverters include unipolar SPWM, unipolar frequency doubling SPWM and bipolar SPWM. Since the unipolar SPWM strategy has many combinations, the table shows that the upper and lower tubes of the bridge arm 1 in Figure 1 are high-frequency tubes, and the […]

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Analysis of leakage current suppression mechanism of Heric change topology and double parallel Buck inverter topology

1. Heric change topology 1 Figure 1 shows a non-isolated topology based on the Heric structure. This topology moves a freewheeling switch in the Heric topology to a group of bridge arms. Using the unipolar SPWM strategy shown in Figure 2, in the power transmission stage, current flows through S3-S2 (positive direction) and S1-S5-S4 (negative direction); In […]

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Analysis of leakage current suppression mechanism of H5 changing topology

1. H5 change topology 1 Figure 1 is a circuit structure of a six-switch non-isolated inverter, using the unipolar SPWM strategy shown in Figure 2. This topology adds a switch tube based on the H5 topology. In the power transmission phase, current flows through S5-S1-S4 (positive direction) and S6-S2 (negative direction); in the freewheeling phase, the current flows […]

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Analysis of leakage current suppression mechanism of H5, Heric and H6 topology

1. H5 topology Figure 1 is SMA SoLdr’s patented topology-H5 topology [8], this topology has a switch S5 in series in the main loop of the full bridge circuit. The H5 topology uses unipolar SPWM modulation, and its driving logic diagram is shown in Figure 2. In the power transmission phase, current flows through S5-S1-S4 (positive direction) and […]

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