Three-phase cascade power conversion unit output pulsation control method under unbalanced power grid voltage

By calculating the positive and negative sequence dq axis components of the unbalanced grid voltage and controlling the positive and negative sequence dq component of the input current, the output side pulsation problem caused by the imbalance of the three-phase input voltage is solved, and the three-phase power balance and pulsation suppression are achieved, and the device current stress is reduced.

CN120389423APending Publication Date: 2025-07-29ZHEJIANG UNIV
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Patent Information

Application Number
CN202510514847.X
Authority / Receiving Office
CN · China
Patent Type
Applications(China)
Current Assignee / Owner
Filing Date
2025-04-23
Publication Date
2025-07-29

AI Technical Summary

Technical Problem

In the case of three-phase input voltage imbalance, the control strategy of the traditional power conversion unit cannot effectively suppress power pulsation on the output side, resulting in unstable system operation.

Method used

By calculating the positive and negative sequence dq axis components of the unbalanced grid voltage, the positive and negative sequence dq component of the input current is controlled to maintain active power balance, and the input current is maintained at the reference value through the PI controller. Combined with the bus capacitance voltage harmonic suppression module, it ensures that the phase difference between the ripple power on the output side is 2/3π, achieving three-phase power balance and pulsation suppression.

Benefits of technology

When the input grid voltage is unbalanced, the three-phase transmission power is balanced, which suppresses the low-frequency pulsation on the output side, reduces the current stress of the device, and maintains the effect of traditional dq control when the grid voltage is balanced.

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Abstract

The invention discloses a three-phase cascade power conversion unit output pulse control method under unbalanced power grid voltage. Aiming at the problem that a three-phase three-wire system cascade power conversion unit can cause three-phase input power imbalance when three-phase input grid voltage is unbalanced, so that low-frequency ripple pulsation is generated on an output side and normal work is influenced, positive and negative sequence components of input voltage and input current in a dq coordinate system are extracted through abc / dq conversion; according to the transmission power of the converter and the positive and negative sequence d-axis and q-axis components of the input voltage, reference values of the positive and negative sequence d-axis and q-axis components of the input current under the conditions that the active power at the input side is kept constant and the ripple power is zero are calculated, and the positive and negative sequence d-axis and q-axis components of the input current are controlled to be kept at the reference values by using a PI controller. Power balance control is kept under the condition that input power grid voltage is unbalanced, three-phase ripple power is equal, and the phase difference is 2 / 3 pi, so that the ripple power of an output side is suppressed.
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