Elevator Drive Unit Control for Regenerative Power Limiting
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Modern elevator systems face challenges in managing regenerative power, particularly during special operational situations like mains power outages, where existing brake chopper circuitry is large, expensive, and generates electromagnetic disturbances.
Innovation Solution
An elevator drive unit with a control unit that detects special operational situations and limits regenerative power supply by increasing power losses in the hoisting motor or frequency converter, eliminating the need for a separate brake chopper circuitry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If brake chopper circuitry is used to manage regenerative power during special operational situations, then regenerative power can be handled, but the device becomes larger, more expensive, and generates electromagnetic disturbances
Solution Approach 1:
The patent merges the regenerative power management function into the existing frequency converter by enabling bidirectional power transfer capability. The control unit integrates the logic to detect special operational situations and control power flow, eliminating the need for separate brake chopper circuitry. The frequency converter's power switches are controlled to allow power to flow from the motor back to the mains, combining multiple functions into a single integrated device.
Solution Approach 2:
The frequency converter is designed to perform multiple functions: it can operate in motoring mode to drive the motor, in regenerating mode to return power to mains, and in power limitation mode to manage regenerative power during special operational situations. This multi-functionality eliminates the need for dedicated brake chopper circuitry, reducing device complexity while maintaining reliability.
2Loss of energy
If brake chopper circuitry is used to manage regenerative power, then power can be dissipated, but electromagnetic disturbances are generated
Solution Approach 1:
Instead of dissipating regenerative power as heat through a brake resistor (which causes electromagnetic disturbances), the patent converts the regenerative power back into useful electrical energy that can be fed to the mains. The bidirectional frequency converter transforms the motor's generated power into a form suitable for mains injection, turning a potentially harmful energy recovery process into a beneficial grid interaction.
Solution Approach 2:
The frequency converter acts as an intermediary device between the motor and the mains, managing the bidirectional power flow. During regenerative operation, it mediates the power transfer by controlling the power switches to enable controlled rectification of the motor's generated power, preventing direct injection that would cause disturbances while efficiently returning energy to the grid.
3Stability of the object's composition
If regenerative power is limited during special operational situations, then power supply stability is improved, but power loss increases
Solution Approach 1:
The system dynamically adjusts its operation based on detected special operational situations. The control unit monitors system conditions and adaptively controls the frequency converter's power flow characteristics. During normal operation, full regenerative power transfer is enabled, but during special situations, the control logic dynamically limits the power transfer to maintain stability, creating a dynamic response that balances stability requirements with energy efficiency.
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
Effectively manages regenerative power without additional circuitry, reducing electromagnetic disturbances and operational costs by consuming excess power as heat within the elevator hoisting motor.
Implementation Method 1
a frequency converter for enabling a bidirectional transfer of power between the mains and the elevator hoisting motor
Implementation Method 2
an elevator hoisting motor configured to drive an elevator car in an elevator shaft between a plurality of landings
Implementation Method 3
The Brake chopper circuitry comprises a power resistor and a power transistor to control current through the resistor. By means of the brake chopper circuitry, any extra power is consumed into heat in the power resistor.
Data Source
AI summary
The invention relates to an elevator drive unit for managing a regenerative power of an elevator system. The elevator drive unit comprises: first terminals for connecting the elevator drive unit to the mains; second terminals for connecting the elevator drive unit to an elevator hoisting motor; a frequency converter for enabling a bidirectional transfer of power between the mains and the elevator hoisting motor; and a control unit. The control unit is configured to: obtain an indication representing a detection of a special operational situation of the elevator system, introduce a non-zero power limit specific to the detected special operational situation of the elevator system, and control the frequency converter to limit supply of the regenerative power from the elevator hoisting motor to the mains to the power limit. The invention relates also to an elevator system and a method for managing a regenerative power of an elevator system.