Buck-Boost Rectifier for Continuous Power Under Varying AC Voltage

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Three-phase PWM rectifiers in vehicle refrigeration systems face challenges in managing varying AC voltage from alternators, leading to potential damage when AC voltage exceeds desired DC voltage, requiring power disconnection to prevent damage.

Innovation Solution

Incorporating a novel buck circuit within the three-phase PWM rectifier allows for continuous DC power provision by reducing DC voltage and enabling both buck and boost operations, ensuring power is always available without complete disconnection.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a conventional three-phase PWM rectifier is used to convert AC power to DC power, then DC voltage can be boosted when AC voltage is low, but the system must be completely disconnected when AC voltage exceeds desired DC voltage to prevent damage

Engineering Contradiction:

Improvesystem protectionVSAvoidcontinuous power supply

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The rectifier system is designed to perform multiple functions: it can operate in boost mode when AC voltage is low, in buck mode when AC voltage is high, and in unity power factor rectifier mode under normal conditions. This multi-functionality eliminates the need for complete system disconnection and enables continuous operation across varying voltage conditions.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The system dynamically switches between different operating modes (buck, boost, and unity power factor rectifier modes) based on the relationship between AC input voltage and desired DC output voltage. This dynamic adaptation allows the system to respond to varying voltage conditions without complete disconnection, maintaining continuous power supply while protecting against overvoltage damage.

Inventive Principle:

Principle #15Dynamics

2Reliability

If power is disconnected when AC voltage exceeds desired DC voltage to prevent damage, then system protection is achieved, but continuous power supply is interrupted

Engineering Contradiction:

Improvesystem protectionVSAvoidpower interruption

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The system incorporates a buck circuit in advance, preparing the capability to reduce DC voltage before overvoltage damage can occur. This preliminary preparation allows the system to handle high AC voltage conditions by switching to buck mode, preventing the need for emergency disconnection and avoiding power interruption.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system maintains continuous useful action by ensuring power is always available through the integrated buck circuit. Whether AC voltage is low (boost mode), normal (unity power factor mode), or high (buck mode), the system continuously provides protected DC power output without complete disconnection, eliminating gaps in power supply.

Inventive Principle:

Principle #20Continuity of useful action

3Adaptability or versatility

If only boost capability is provided in the rectifier, then DC voltage can be increased when AC voltage is low, but the system cannot handle cases where AC voltage is greater than desired DC voltage

Engineering Contradiction:

Improvevoltage regulation rangeVSAvoidsystem safety

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The system changes its operating parameters and mode based on the input voltage conditions. By switching between boost, buck, and unity power factor rectifier modes, the system adapts its voltage regulation behavior to match the actual AC voltage level, expanding its adaptability while maintaining safety through controlled operation in each mode.

Inventive Principle:

Principle #35Parameter changes

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

The solution ensures continuous power supply to refrigeration systems by dynamically adjusting DC voltage based on AC input, preventing damage and maintaining system functionality across varying AC voltage conditions.

Implementation Method 1

Three-phase PWM rectifiers convert three-phase alternating current (AC) power into direct current (DC) power

Methodology Applied

Scientific EffectRectification:

Implementation Method 2

The buck circuit enables the three-phase PWM rectifier to reduce the DC voltage generated

Methodology Applied

Scientific EffectVoltage reduction (buck conversion):

Implementation Method 3

The voltage of the DC power can be boosted and exceed the voltage of the AC power

Methodology Applied

Scientific EffectVoltage boosting:

Data Source

PatentEP2766983B1Buck-boost rectifier, refrigeration system including a buck-boost rectifier, and method of providing power to a refrigeration unit via a buck-boost rectifier

Publication Date: 2019.10.30 THERMO KING CORP

Figure 1a
Figure 1b
Figure 2

AI summary

A buck/boost rectifier. The rectifier is connectable to an alternating current power source and includes an upper bus, a lower bus, an upper rectifier, a lower rectifier, a pulse- width-modulation (PWM) controller, a phase-angle (PA) controller, and a capacitor. The upper rectifier is coupled to the upper bus, and the lower rectifier is coupled in a series-type relationship with the upper rectifier and to the lower bus. The PWM controller is coupled to the lower rectifier and is configured to boost a direct current (DC) voltage output by the rectifier. The PA controller is coupled to the lower rectifier and is configured to buck the DC voltage output by the rectifier. The capacitor is coupled between the upper bus and the lower bus.