Bidirectional Power Converter Phase Control for Noise Filter
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Solution Overview
Problem
Existing bidirectional power conversion systems for vehicles, such as PHEVs and EVs, face challenges in improving the power factor due to phase advances caused by shunt currents in noise filter circuits, which hinder efficient energy transfer between AC and DC sides.
Innovation Solution
A control method and apparatus that utilize a bidirectional conversion circuit with a filter circuit including a capacitor, where the control unit manages the phase of AC current to align with AC voltage by reversing polarity during specific phases of the AC cycle, canceling out phase advances and improving the power factor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a noise filter circuit with capacitor is provided on the AC side of the bidirectional conversion circuit, then noise removal is improved, but phase advance occurs due to shunt current which deteriorates power factor
Solution Approach 1:
The control unit applies preliminary anti-action by detecting the phase advance caused by the capacitor and proactively adjusting the AC current phase in the opposite direction. The control unit calculates the required phase correction amount based on the capacitor's impedance and adjusts the bidirectional conversion circuit to generate AC current with a phase that compensates for the anticipated phase advance, thereby preventing power factor deterioration before it occurs.
Solution Approach 2:
The control unit dynamically changes the phase parameter of the AC current output by the bidirectional conversion circuit. By adjusting the phase angle of the AC current relative to the AC voltage based on real-time detection of phase relationships and capacitor characteristics, the system optimizes the power factor while maintaining noise filtering effectiveness. This parameter adjustment allows the system to adapt to varying operating conditions and capacitor values.
2Loss of energy
If AC current phase is adjusted to compensate for phase advance, then power factor is improved, but control complexity increases
Solution Approach 1:
The control unit implements feedback control by continuously detecting the phase relationship between AC voltage and AC current, calculating the phase advance amount caused by the capacitor, and adjusting the AC current phase accordingly. This closed-loop feedback mechanism automatically maintains optimal power factor without requiring manual intervention or complex external control systems, as the control unit self-regulates based on real-time system state.
Solution Approach 2:
The control system performs self-service by autonomously detecting its own operational parameters (phase relationships, current magnitude) and automatically adjusting its control strategy to compensate for the capacitor's effects. The control unit calculates the necessary phase correction based on its own detected state and capacitor characteristics, enabling the system to self-optimize without external assistance or additional complex control infrastructure.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively improves the power factor by ensuring the phase of AC voltage and AC current coincide, enhancing energy transfer efficiency and reducing power loss during both charging and discharging operations.
Implementation Method 1
a filter circuit that is provided on an AC side of the bidirectional conversion circuit and includes a capacitor
Implementation Method 2
an AC-DC conversion circuit having a power factor correction (hereinafter referred to as PFC) function of converting AC to DC upon charging and an inverter function of converting DC to AC upon discharging
Data Source
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AI summary
A power conversion apparatus comprises a bidirectional conversion circuit that enables first conversion converting DC to AC and second conversion converting AC to DC and a filter circuit that is provided on an AC side of the bidirectional conversion circuit and that includes a capacitor. A control unit is provided for performing control such that the bidirectional conversion circuit makes the first conversion during the former stage of each half cycle of AC voltage, and performing control such that the bidirectional conversion circuit makes the second conversion during the latter stage of each half cycle of AC voltage. The control unit performs control such that AC current of an opposite polarity to that of the AC voltage flows to an AC side of the bidirectional conversion circuit during the former stage and performs control such that AC current of the same polarity as that of the AC voltage flows to the AC side of the bidirectional conversion circuit during the latter stage.