Inverter Speed Command Correction During DC Bus Voltage Drops
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Solution Overview
Problem
Elevator systems face challenges in maintaining operation during instantaneous power supply voltage drops, leading to accelerated or decelerated movement due to reduced motor torque, without explicit triggers for safety measures like emergency brakes.
Innovation Solution
A motor drive system with a first and second power conversion device, including a DC voltage control and speed control system, that adjusts speed command values based on DC voltage fluctuations to stabilize operation during voltage drops.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If conventional field current control is used to suppress speed drop during voltage drops, then speed stability is improved, but the system cannot provide explicit triggers for safety measures and the duration of operation is limited
Solution Approach 1:
The invention implements a feedback mechanism by monitoring DC voltage levels and using this information to dynamically adjust speed command values. The control device receives DC voltage information, compares it against threshold values, and automatically modifies operational parameters accordingly, creating a closed-loop system that enhances both stability and safety.
Solution Approach 2:
The system performs preliminary action by detecting DC voltage drops in advance and proactively adjusting speed command values before the voltage drop causes dangerous operational conditions. This anticipatory control allows the system to maintain stability during voltage fluctuations and provides early triggers for safety measures.
2Use of energy by moving object
If the motor torque is reduced due to instantaneous power supply voltage drop, then energy consumption is reduced, but the elevator accelerates or decelerates due to gravity effects
Solution Approach 1:
The invention applies dynamics by making the speed command value adaptive rather than fixed. The control device dynamically adjusts the speed command based on real-time DC voltage conditions, allowing the system to optimize energy consumption during voltage drops while maintaining position stability through controlled adjustments rather than rigid torque maintenance.
Solution Approach 2:
The system changes operational parameters by modifying speed command values in response to DC voltage fluctuations. Instead of maintaining constant torque, the system adjusts speed parameters dynamically, allowing energy-efficient operation during voltage drops while preventing uncontrolled acceleration or deceleration through controlled parameter adaptation.
3Reliability
If the inverter driving is discontinued during voltage drops, then safety is improved, but operational continuity is reduced
Solution Approach 1:
The system performs preliminary action by detecting voltage drops early and adjusting operational parameters before safety thresholds are breached. This allows the elevator to continue operating safely during brief voltage fluctuations, extending operational continuity while maintaining safety through proactive control adjustments rather than immediate shutdown.
Solution Approach 2:
The invention enables dynamic operational adjustment by continuously monitoring DC voltage and adapting speed command values in real-time. This dynamic response allows the system to maintain safe operation during voltage drops, extending the duration of continuous operation while preserving safety through adaptive control rather than static discontinuation thresholds.
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 extends the duration of inverter driving during voltage drops, preventing operational interruptions and ensuring safety by stabilizing motor speed and activating emergency brakes when necessary.
Implementation Method 1
a first power conversion device (10) that converts a first AC voltage supplied from an AC power supply (1) into a DC voltage
Implementation Method 2
a second power conversion device (50) that converts the DC voltage into a second AC voltage
Implementation Method 3
outputs the second AC voltage to a motor (2)
Data Source
Figure 1
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AI summary
A motor drive system according to an embodiment includes a converter device and an inverter device. The converter device converts a first AC voltage into a DC voltage. The inverter device converts the DC voltage into a second AC voltage and outputs the second AC voltage to a motor. The converter device causes the DC voltage to follow a DC voltage command value. The inverter device causes a speed of the motor to follow a speed command value. The inverter device corrects the speed command value based on the DC voltage command value and the DC voltage. The inverter device controls the motor by applying the corrected speed command value.