Power Conversion Device DC Bus Voltage Stabilization
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Solution Overview
Problem
Conventional power conversion apparatuses require an external DC voltage supply to stabilize the DC bus voltage of the inverter, making them unstable during transient variations in AC input power and load conditions.
Innovation Solution
A power conversion apparatus that controls a short-circuiting switch to maintain the DC voltage of the inverter circuit at a target voltage, eliminating the need for an external voltage supply and ensuring stable operation by bypassing the smoothing capacitor during specific phases and using PWM control to manage current and voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If an external DC voltage supply is connected to stabilize the DC bus voltage of the inverter, then the DC bus voltage stability is improved, but the device complexity and cost increase
Solution Approach 1:
The invention extracts and eliminates the external DC voltage supply component from the system by implementing an alternative voltage stabilization mechanism using the existing capacitor and switching devices in the power conversion circuit
Solution Approach 2:
The capacitor in the circuit is made to serve multiple functions: both its traditional energy storage role and a new role in stabilizing the DC bus voltage through controlled charge and discharge cycles managed by the switching devices
2Device complexity
If the externally connected DC voltage supply has insufficient supply ability relative to transient variations, then the device complexity is reduced, but the DC bus voltage varies and operational stability deteriorates
Solution Approach 1:
The control section monitors the voltage across the capacitor and dynamically adjusts the switching states of the switching devices to maintain voltage stability, implementing a feedback control mechanism that responds to transient variations in AC input power and load conditions
Solution Approach 2:
The switching devices are controlled to periodically charge and discharge the capacitor in response to transient variations, creating a rhythmic energy exchange that stabilizes the DC bus voltage during dynamic operating conditions
3Ease of operation
If the capacitor is controlled to reduce harmonics of input current, then the input power factor is improved, but the DC bus voltage becomes unstable without external supply
Solution Approach 1:
The control system dynamically adjusts the operation of switching devices based on real-time voltage conditions, transitioning the capacitor's role from static energy storage to dynamic voltage regulation while maintaining power factor correction functionality
Solution Approach 2:
The invention changes the operational parameters of the capacitor by controlling its charge and discharge cycles through switching devices, transforming it from a passive component into an active voltage stabilization element that responds to system conditions
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 solution stabilizes the DC bus voltage without an external supply, reduces switching losses, and improves the input power factor, enabling stable operation and efficient energy use.
Implementation Method 1
a series circuit including a capacitor and a diode is connected in parallel with the main switching device, and a pair of ends of the capacitor is a DC output
Implementation Method 2
A reactor is provided at a connection point between an AC power supply and a diode rectification circuit
Implementation Method 3
A reactor is provided at a connection point between an AC power supply and a diode rectification circuit
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
In a power conversion apparatus that converts AC power to DC power, an inverter circuit (100) including one or more single-phase inverters connected in series with each other is connected in series at the subsequent stage of a rectification of an AC input. At the subsequent stage of the inverter circuit (100), a smoothing capacitor (11) connected via a rectification diode (10), and a short-circuiting switch (9) for bypassing the smoothing capacitor (11) are provided. The short-circuiting switch (9) is subjected to ON/OFF control by PWM control such that a voltage of the DC voltage supply (8) of the inverter circuit (100) follows a target voltage. The inverter circuit (100) is subjected to output control such that a DC voltage of the smoothing capacitor (11) follows a target voltage and an input power factor is improved.