DC/AC Power Converter Double-Frequency Pulsation Suppression
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Solution Overview
Problem
Semiconductor power converters face challenges in suppressing double-frequency power pulsations on the DC side when the AC power supply is faulty, despite enhanced current controlling performance.
Innovation Solution
A semiconductor power converter with three-phase bridge connections, self-extinguishing semiconductor devices, voltage and current measuring devices, phase detectors, and AC current adjusters that calculate and output commanded pulses to manage positive and negative-sequence voltage and current vectors, effectively suppressing double-frequency pulsations by adding commanded negative-sequence currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If enhanced current controlling performance is implemented, then current control capability is improved, but double-frequency power pulsations on the DC side cannot be suppressed
Solution Approach 1:
The patent segments the current control into positive-sequence current control and negative-sequence current control. By separating these two control components, the system can independently manage active power transfer (positive sequence) and suppress double-frequency pulsations (negative sequence), resolving the contradiction between current control capability and pulsation suppression.
Solution Approach 2:
The patent introduces a new control dimension by adding negative-sequence current injection to the traditional positive-sequence current control. This dimensional expansion allows the system to address pulsation suppression as an independent control objective alongside current regulation, eliminating the trade-off between the two.
2Reliability
If the AC power supply is faulty, then continuous operation is required, but double-frequency pulsations occur on the DC side
Solution Approach 1:
The patent applies preliminary anti-action by pre-calculating and injecting negative-sequence currents in anticipation of AC side faults. The controller continuously monitors AC voltage and automatically activates negative-sequence current injection when faults are detected, preventing double-frequency pulsations before they significantly impact DC side stability.
Solution Approach 2:
The patent implements feedback control by continuously measuring AC voltage, detecting phase information, and adjusting both positive-sequence and negative-sequence current commands based on real-time system state. This closed-loop feedback ensures stable continuous operation while suppressing pulsations caused by AC side faults.
3Object-generated harmful factors
If negative-sequence current control is added, then double-frequency pulsations are suppressed, but control system complexity increases
Solution Approach 1:
The patent achieves multi-functionality by using the same current control platform to perform both positive-sequence current regulation and negative-sequence pulsation suppression. The control system universally handles both functions through a unified current command structure, avoiding the need for separate independent control systems and minimizing additional complexity.
Solution Approach 2:
The patent changes control parameters by introducing negative-sequence current components (idn, iqn) alongside the traditional positive-sequence currents. By systematically organizing these parameters and using coordinate transformation techniques, the patent manages the increased parameter complexity in a structured manner that minimizes computational burden.
Data Source
AI summary
A commanded negative-sequence current is added to a commanded current so as to suppress double-frequency pulsation on the DC side. The commanded negative-sequence current is found from three values (i.e., the detected value of positive-sequence voltage vector on the power-supply side, the detected value of negative-sequence voltage vector, and a commanded positive-sequence current). Thus, the pulsations which occur on the DC side of a semiconductor power converter and which have a frequency double the power-supply frequency are suppressed even when the AC power supply is at fault while assuring stability of the current control system, thus permitting stable and continuous operation.