Regenerative Variable Frequency Drive Active Converter
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Solution Overview
Problem
Existing variable frequency drives with diode rectifiers cannot efficiently handle regenerative power from single-phase AC sources, leading to voltage rise on the DC bus, increased complexity, and harmonic distortions, which are not suitable for residential and rural areas with single-phase AC power supply.
Innovation Solution
A regenerative variable frequency drive with an active converter that converts single-phase AC power to DC and back to three-phase AC power, using an active half-bridge converter and inverter, along with a filter capacitor and bus capacitors, to manage power flow and boost voltage, allowing power to be put back onto the grid.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a diode rectifier is used to convert AC power to DC power, then the conversion is simple and reliable, but the generated power causes voltage rise on the DC bus and requires dynamic braking resistors that add complexity and expense
Solution Approach 1:
The patent inverts the conventional diode rectifier approach by using an active converter that can operate in reverse mode. Instead of allowing generated power to cause voltage rise (harmful effect), the active converter actively manages power flow to prevent voltage rise and enables regenerative braking by returning power to the grid. This inversion transforms a harmful effect into a useful function.
Solution Approach 2:
The active converter serves multiple functions: it acts as a rectifier during motor acceleration, as a regenerative brake during deceleration, and as a power factor correction device throughout operation. This multi-functionality eliminates the need for separate dynamic braking resistors and power factor correction circuits, reducing overall system complexity while improving reliability.
2Use of energy by moving object
If a regenerative variable frequency drive with active converter is used to handle generated power, then power consumption is reduced and generated power is returned to the line, but three-phase active converters cannot convert power from single-phase AC source
Solution Approach 1:
The patent segments the power conversion process into two distinct stages: first, a single-phase active converter converts single-phase AC to DC, and second, a three-phase inverter converts DC to variable frequency three-phase AC. This segmentation allows each converter to be optimized for its specific function, enabling the system to accept single-phase input while delivering three-phase output.
Solution Approach 2:
The DC bus acts as an intermediary between the single-phase active converter and the three-phase inverter. The single-phase converter charges the DC bus, and the three-phase inverter draws from it, allowing power to be transferred from single-phase to three-phase without requiring a direct conversion path. This intermediary approach enables adaptability to single-phase sources while maintaining three-phase output capability.
3Ease of manufacture
If diode rectifier converters are used to convert AC power, then the conversion is straightforward, but harmonic distortions are created that affect other users on the grid and reduce power factor
Solution Approach 1:
The active converter incorporates feedback control that monitors grid voltage and current, and adjusts its operation to minimize harmonic distortion and maintain unity power factor. The controller continuously adjusts the switching patterns of the active switches based on real-time measurements, creating a feedback loop that eliminates the harmful effects of traditional diode rectifiers while maintaining conversion simplicity through integrated control.
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 reduces power consumption, eliminates the need for dynamic braking resistors, and minimizes harmonic distortions, enabling efficient operation with single-phase AC power and providing a higher power factor, suitable for both residential and industrial applications.
Implementation Method 1
an active converter that converts single phase AC power to DC power and DC power to single phase AC power
Implementation Method 2
an inverter that converts DC power to variable frequency, three phase AC power
Implementation Method 3
a filter capacitor, active half bridge first and second modules, a positive bus bar, a negative bus bar, first and second bus capacitors
Implementation Method 4
The converter includes first and second input lines that connect to a single phase AC power source, first and second inductors
Implementation Method 5
The controller monitors voltages and input current, and drives the switches with a pulse width modulated signal having a modulation index
Data Source
AI summary
A regenerative variable frequency drive includes an active converter connected to an inverter. The converter has a filter capacitor, an inductor, two half bridges, bus bars that connect to the inverter and bus capacitors. The converter converts single phase AC power to DC power and DC power to single phase AC power, boosts the AC power, reduces input line harmonics, maintains input current in phase with utility voltage in order to achieve near unity power factor, and maintains constant DC voltage between the bus bars.