Elevator Line Bridge Filter Reactive Power Compensation
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Solution Overview
Problem
Existing building automation systems struggle to effectively compensate for reactive power produced by inductive and capacitive loads, leading to increased current and heating in power transmission lines, which is not utilized and results in inefficiencies in power supply systems.
Innovation Solution
An electrical converter system for elevators, comprising a smoothing filter and a converter matrix with a controller that determines reactive power using impedance information and makes compensative connections to mitigate reactive power, communicating with building automation systems to coordinate total reactive power compensation across multiple subsystems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If reactive power compensation is implemented using traditional building automation systems, then reactive power can be monitored and controlled, but the compensation effectiveness is insufficient and cannot fully eliminate the harmful effects of reactive power on power transmission lines
Solution Approach 1:
The patent combines the reactive power compensation function with the elevator brake energy recovery system. The electrical converter that normally converts brake energy to electrical power is also used to compensate reactive power for inductive loads in the building. This merging of functions eliminates the need for separate compensation equipment and achieves effective reactive power compensation while recovering brake energy, thereby reducing energy loss without proportionally increasing system complexity
Solution Approach 2:
The electrical converter is designed to perform multiple functions: (1) converting mechanical energy from elevator braking to electrical energy, (2) compensating reactive power for inductive loads, and (3) injecting active power back to the grid. This multi-functionality allows a single device to address multiple energy efficiency issues simultaneously, improving compensation effectiveness while avoiding the complexity of multiple separate systems
2Loss of energy
If reactive power is compensated by adding dedicated compensation equipment, then reactive power can be effectively reduced, but the system complexity and cost increase significantly
Solution Approach 1:
The patent merges reactive power compensation with the existing elevator electrical converter system. Instead of adding separate capacitor banks or active power factor correction equipment, the invention utilizes the converter's existing power electronic components (IGBTs, diodes, DC link capacitor) to perform both brake energy recovery and reactive power compensation. This approach effectively reduces reactive power loss without the need for dedicated compensation equipment, thereby avoiding significant increases in system complexity and cost
3Stability of the object's composition
If the smoothing filter is used without reactive power compensation, then the filter can smooth output currents, but the filter produces reactive power that increases current and causes heating in power transmission lines
Solution Approach 1:
The patent converts the harmful reactive power generated by the smoothing filter into a beneficial function. The electrical converter detects the reactive power produced by the filter's inductive and capacitive components and actively compensates for it by adjusting the converter's output. This transforms the filter's harmful reactive power generation into an opportunity for demonstrating the converter's compensation capability, thereby maintaining current smoothness while eliminating the harmful effects of reactive power on transmission lines
Solution Approach 2:
The system implements feedback control where the controller continuously monitors the reactive power produced by the smoothing filter using pre-determined impedance information, and dynamically adjusts the converter matrix connections to compensate for the reactive power. This closed-loop feedback mechanism ensures that the filter's reactive power generation is continuously countered, maintaining output current smoothness while preventing reactive power from causing heating in transmission lines
Data Source
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AI summary
The invention relates to a method and an electrical converter of an elevator. In the method a controller of the electrical converter determines a first reactive power produced by a smoothing filter using pre-determined information on impedance of the smoothing filter. The controller may also receive information on a second reactive power from a remote node over a communication channel, the second reactive power being produced to a grid. The controller adds the first reactive power and the second reactive power to yield a total reactive power. The controller requests the electrical converter to make a plurality of compensative connections in the converter matrix to compensate the first reactive power or the total reactive power.