Multilevel Regenerative Drive PWM Strategy for Acoustic Noise and Efficiency
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Solution Overview
Problem
Elevator regenerative drives face challenges in managing acoustic noise, efficiency, neutral point stability, and thermal balancing, which are not adequately addressed by existing control systems.
Innovation Solution
A control system and method that apply unipolar and bipolar modulation to both the converter and inverter of a multilevel regenerative drive, utilizing a controller to manage power modulation and achieve improved efficiency, acoustic performance, and thermal balancing, while maintaining neutral point stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional PWM control is used in regenerative drives, then the system can operate, but acoustic noise and efficiency are not optimized
Solution Approach 1:
The control system dynamically selects between unipolar and bipolar PWM modulation modes based on operating conditions. The controller switches between different modulation strategies to optimize acoustic performance across varying load and speed conditions, making the control approach adaptive rather than static
Solution Approach 2:
The invention changes the PWM modulation parameters (switching patterns, duty cycle calculation methods) between unipolar and bipolar modes to optimize acoustic noise. By varying these control parameters based on operating conditions, the system achieves better acoustic performance without fundamental redesign
2Loss of energy
If conventional PWM control is used, then the system can operate, but efficiency and thermal balancing are not optimized
Solution Approach 1:
The control system adapts its PWM strategy dynamically based on real-time operating conditions including load, speed, and thermal states. This dynamic adjustment optimizes efficiency across the operating range and enables active thermal management by redistributing switching losses
Solution Approach 2:
The control system uses feedback from current sensors and temperature sensors to adjust PWM modulation parameters. This closed-loop control optimizes efficiency by adapting to actual operating conditions and manages thermal balance through active redistribution of switching losses among power devices
3Stability of the object's composition
If conventional PWM control is used, then the system can operate, but neutral point stability is not maintained
Solution Approach 1:
The control system continuously monitors the neutral point potential and adjusts PWM switching patterns to maintain stability. When neutral point imbalance is detected, the controller modifies the duty cycles or switching sequences to redistribute currents and restore balance, creating a closed-loop control mechanism
Data Source
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AI summary
A method (70) for controlling a multilevel regenerative drive (30) having a converter (32) and an inverter (34) is disclosed. The method (70) may include applying at least one of unipolar modulation and bipolar modulation to the converter (32), and applying at least one of unipolar modulation and bipolar modulation to the inverter (34). A control system (52) for a mechanical system (20) having a motor (28) is also disclosed. The control system (52) may comprise a converter (32) operatively connected to a power source (29), and an inverter (34) operatively connected to the motor (28) of the mechanical system (20). At least one controller may be in communication with the converter (32) and inverter (34), and may be configured to apply at least one of unipolar modulation and bipolar modulation to each of the converter (32) and the inverter (34).