Hybrid Energy Storage Unit for BLDC Motor Torque Ripple Suppression
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Solution Overview
Problem
Existing BLDCM systems face challenges in torque performance and commutation torque ripple suppression, leading to noise, vibration, and reduced motor stability, particularly due to the limitations of battery life caused by frequent charging and discharging during acceleration and braking processes.
Innovation Solution
A hybrid energy storage unit (HESU) comprising a battery, supercapacitor, and power MOSFETs, connected through a bidirectional power switch and three-phase inverter, which enables effective braking torque control, power sharing, and commutation torque ripple suppression by constructing specific voltage vectors during different operational modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If battery is used as main power supply for BLDCM, then high energy density is achieved, but power density is limited and battery life is reduced due to frequent charging and discharging
Solution Approach 1:
The power supply system is segmented into two independent energy storage devices: battery and supercapacitor. Each component handles different aspects of power delivery - battery provides sustained energy while supercapacitor handles peak power demands, resolving the contradiction between energy density and power density
Solution Approach 2:
The patent combines battery and supercapacitor into a hybrid energy storage system where both components work together through coordinated control. The merging allows the system to leverage the high energy density of battery and high power density of supercapacitor simultaneously
2Productivity
If battery supplies power during acceleration and braking, then motor operation is maintained, but battery life is shortened due to high-rate charging and discharging
Solution Approach 1:
Supercapacitor acts as an intermediary between the motor and battery during acceleration and braking. It absorbs peak power demands and regenerative braking energy, preventing direct high-rate charging/discharging of the battery while maintaining motor operation
Solution Approach 2:
The system recovers energy during braking through the supercapacitor instead of discarding it as heat. The supercapacitor captures regenerative braking energy and can reuse it during acceleration, reducing the battery's charging cycles and extending its life
3Device complexity
If supercapacitor is connected directly to load in passive HESU structure, then simple and reliable structure is achieved, but voltage utilization range of supercapacitor is limited due to battery voltage clamping effect
Solution Approach 1:
The patent employs dynamic switching control of power MOSFETs to change the circuit configuration in real-time. During certain operating conditions, the supercapacitor is connected in series with the battery to double the output voltage, while in other conditions it operates independently, making the system adaptable to different voltage requirements
4Adaptability or versatility
If HESU with DC-DC converter is used to improve voltage utilization, then voltage utilization range is improved, but system volume increases due to additional inductors
Solution Approach 1:
The patent extracts and removes the DC-DC converter and its associated inductors from the HESU structure. Instead, it uses the natural voltage characteristics of the battery-supercapacitor combination and power MOSFET switching to achieve voltage multiplication, eliminating unnecessary components and reducing system volume
5Device complexity
If conventional HESU design is used without considering torque performance, then energy management is simplified, but commutation torque ripple causes large noise and vibration
Solution Approach 1:
The patent implements feedback control by monitoring motor current and position to detect commutation torque ripple. The control system adjusts the switching timing and duty cycle of power MOSFETs based on this feedback to minimize torque ripple, reducing noise and vibration while maintaining straightforward energy management
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 proposed solution enhances energy utilization, alleviates battery life shortening, reduces system volume, and improves motor stability by effectively managing energy storage and supply during braking, acceleration, and constant speed operations, while suppressing torque ripple.
Implementation Method 1
in the braking process, the motor can convert mechanical energy into electrical energy and it can be recovered by the supercapacitor
Implementation Method 2
the battery with high energy density is often used as main power supply
Implementation Method 3
The HESU is designed with a battery, an electrolytic capacitor C, a bidirectional power switch, a first power MOSFET, a second power MOSFET and a supercapacitor SC
Data Source
AI summary
A brushless DC motor system control method provided is based on a hybrid energy storage unit. The HESU topology is designed, and the output of the designed HESU is connected to the input of three-phase inverter, and the output of three-phase inverter is connected with the three-phase windings of the BLDCM. In braking operation, two kinds of braking vectors are constructed according to the HESU and three-phase inverter. Moreover, through the combined action of the two vectors, the braking torque control is achieved and meanwhile the braking energy is fed back to the supercapacitor. In electric operation, four kinds of electric vectors are constructed according to the HESU and three-phase inverter. Moreover, the power sharing control between battery and supercapacitor is realized by different vectors action during motor acceleration mode, and the torque ripple in commutation period is suppressed by different vectors action during motor constant speed mode.