DC Link Voltage Boosting for Transient High-Torque Motor Drives
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Solution Overview
Problem
Existing variable frequency drive systems are limited by reduced DC link voltage, which restricts high-speed performance and torque capabilities of electric motors, particularly during transient operations.
Innovation Solution
A system and process that transiently boosts the DC link voltage using an energy storage system, such as a battery bank, capacitor bank, or flywheel, directly connected to the DC link, allowing for higher voltage operation and enhanced motor performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If DC link voltage is limited by conventional rectifier-fed variable frequency drive, then system complexity is reduced, but motor high-speed performance and torque capability are restricted
Solution Approach 1:
An energy storage system (capacitor or battery) is introduced as an intermediary component between the rectifier and the inverter. This energy storage system temporarily stores electrical energy and releases it during transient high-torque operations, enabling the motor to exceed conventional torque limits without requiring a complete redesign of the variable frequency drive architecture.
Solution Approach 2:
The system dynamically changes the DC link voltage parameter by charging the energy storage system during normal operation and then utilizing stored energy to temporarily boost the DC link voltage during high-torque demands. This allows the motor to operate at higher voltages and speeds transiently, increasing torque capability without permanently altering the system's rated parameters.
2Power
If DC link voltage is boosted using energy storage system, then motor high-speed performance and torque capacity are improved, but device complexity increases
Solution Approach 1:
The energy storage system serves multiple functions: it acts as a buffer for regenerative braking energy, provides transient torque boosting capability, and can function as part of the DC link voltage regulation system. This multi-functionality justifies the added complexity by delivering multiple performance benefits from a single added component.
Solution Approach 2:
The energy storage system is positioned as an intermediary between the rectifier and inverter, managing energy flow and smoothing transitions. This intermediary role allows the system to handle transient power demands without requiring complex control algorithms or multiple separate components, thereby limiting the increase in overall device complexity.
3Speed
If energy storage system is connected to DC link, then transient high-speed operation is enabled, but loss of energy increases due to additional components
Solution Approach 1:
The system captures regenerative braking energy that would otherwise be wasted and stores it in the energy storage system. This converted harm (energy loss during braking) into benefit (stored energy available for acceleration), reducing overall energy losses and improving efficiency during transient operations.
Solution Approach 2:
The energy storage system maintains continuous energy availability by charging during regenerative braking and discharging during acceleration phases. This continuity ensures that useful energy action is maintained throughout the entire operation cycle, minimizing energy losses and maximizing motor performance during transient high-speed operations.
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 system enables electric motors to operate at higher voltages and speeds, matching acceleration and deceleration performance, and increases torque capacity, overcoming the limitations of conventional DC link voltage constraints.
Implementation Method 1
a rectifier connected to the AC power supply and adapted to convert the polyphase AC voltage into a DC voltage
Implementation Method 2
an inverter module connected to the DC link so as to convert the DC voltage to an alternating current
Implementation Method 3
an energy storage system that stores electrical energy, said energy storage system being connected to said DC link so as to pass power to the DC link
Data Source
Figure 1
Figure 2
Figure 3A~3C
AI summary
A process for transiently increasing performance of an electric motor includes boosting a DC link voltage of a rectifier-fed variable frequency drive of the electric motor by using an energy storage system. The energy storage system delivers power directly to a DC link of the variable frequency drive. The energy storage system can be at least one of a battery bank, capacitor bank and a flywheel. Feedback from the DC link is delivered to a DC link controller.