Direct Power Converter Pulsation Control via Segmented Buffer and Boost Circuits
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Solution Overview
Problem
The charge and discharge circuits in existing direct power converters require high power capacity to compensate for pulsating components of single-phase AC voltage, making it difficult to configure them inexpensively due to the need for high-capacity capacitors like film or laminated ceramic capacitors.
Innovation Solution
A method for controlling a direct power converter that includes a buffer circuit with a capacitor and a switch connected in series, and a boost circuit with a reactor and another switch, where power is provided and received between the power supply lines based on the phase angle of the AC waveform, reducing the power capacity required by controlling the switches to manage power pulsations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a charge and discharge circuit with high power capacity is used to compensate for pulsating components of single-phase AC voltage, then the reliability and performance of the direct power converter is improved, but the cost and device complexity increase due to the need for high-capacity capacitors
Solution Approach 1:
The charge and discharge circuit is segmented into two independent circuits: a buffer circuit for high-frequency switching operations and a boost circuit for low-frequency power pulsation compensation. This segmentation allows each circuit to be optimized for its specific function, enabling the use of smaller, less expensive capacitors in the buffer circuit while the boost circuit handles the remaining power compensation requirements more efficiently.
Solution Approach 2:
The invention introduces dynamic control of switching elements with pulse-width modulation (PWM) to dynamically adjust the operation of the buffer and boost circuits. By dynamically controlling the switching elements based on detected power pulsations, the system can adaptively manage power flow, reducing the required power capacity of the charge and discharge circuit while maintaining reliable operation.
2Stability of the object's composition
If the power capacity of the buffer circuit is increased to handle power pulsations, then the stability of DC voltage is improved, but the volume and weight of the capacitor increase
Solution Approach 1:
The buffer circuit is separated from the main charge and discharge circuit, allowing it to handle high-frequency switching operations with a smaller capacitor. The boost circuit then handles the remaining power pulsation compensation, which reduces the overall power capacity requirement for the buffer capacitor, thereby reducing its volume and weight while maintaining DC voltage stability.
Solution Approach 2:
Dynamic PWM control of the buffer circuit switching element allows the system to respond rapidly to power pulsations, maintaining DC voltage stability with a smaller capacitor. The dynamic adjustment of switching duty ratios enables the buffer circuit to compensate for power variations without requiring excessive energy storage capacity.
3Device complexity
If conventional charge and discharge circuits are used without dynamic control, then the circuit structure is simpler, but the power efficiency and voltage utilization are reduced
Solution Approach 1:
The invention introduces dynamic PWM control to the buffer and boost circuits, allowing real-time adjustment of switching element duty ratios based on detected power pulsations. This dynamic control optimizes power transfer efficiency and voltage utilization by adapting the circuit operation to instantaneous power requirements, significantly improving overall system efficiency despite the added control complexity.
Solution Approach 2:
The control circuit detects power pulsations and uses this feedback information to dynamically adjust the switching element duty ratios in both the buffer and boost circuits. This feedback mechanism ensures that the circuits operate at optimal efficiency points, maximizing power transfer and voltage utilization while minimizing losses.
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 reduces the power provided/received by the buffer circuit, decreases the required power capacity, and improves voltage utilization, allowing for a more efficient and cost-effective design.
Implementation Method 1
a buffer circuit including a capacitor and a switch connected in series with the capacitor at a side close to the first power supply line between the first power supply line and the second power supply line
Implementation Method 2
a boost circuit that boosts a rectified voltage from the converter to charge the capacitor. The boost circuit includes a reactor and another switch connected in series with the reactor at a side close to the second power supply line
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A converter (3) performs full-wave rectification on a single-phase voltage (Vin), thus outputting a rectified voltage (Vrec) across DC power supply lines (LL, LH). An inverter (5) receives the rectified voltage (Vrec) and then supplies a three-phase AC current (Iu, Iv, Iw) to an inductive load (6). Between the DC power supply lines (LL, LH) is connected a charge and discharge circuit (4). The charge and discharge circuit (4) includes a buffer circuit (4a) and a boost circuit (4b). The buffer circuit (4a) includes a series connection between a capacitor (C4) and a switch (Sc). The boost circuit (4b), which may be configured by a boost chopper, includes a switch (S1), a reactor (L4) and a diode (D40). The charge and discharge circuit (4) provides and receives part of pulsations of the power input to the converter (3) between the DC power supply lines (LL, LH).