Variable Speed Drive DC Bus Voltage Amplification
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Solution Overview
Problem
Existing variable speed drives with energy recovery devices fail to amplify the DC bus voltage beyond the rectifier output voltage, cannot regulate DC bus voltage to reduce motor current distortion, and have high total harmonic distortion rates, especially when there are disturbances in the external power supply network, which affects motor torque and flux control.
Innovation Solution
A variable speed drive with a DC power supply bus and an inverter module, incorporating a first non-isolated monodirectional DC/DC converter and a second bidirectional DC/DC converter, along with an electrical energy storage module, which includes super-capacitors, to manage voltage and current harmonics, and provide a boost function for the DC bus voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If existing energy recovery solutions are used, then energy can be stored during braking mode, but the DC bus voltage cannot be amplified beyond the rectifier output voltage
Solution Approach 1:
The power conversion system is divided into two separate DC/DC converter stages: a first DC/DC converter connected in series on the positive line for voltage amplification, and a second DC/DC converter connected between positive and negative lines for energy recovery. This segmentation allows each converter to perform its specific function optimally without requiring a single complex converter to handle all functions.
Solution Approach 2:
The invention combines the voltage amplification function (first DC/DC converter) and the energy recovery function (second DC/DC converter) into a unified system architecture. Both converters work together with the energy storage module to achieve multiple objectives: voltage boosting beyond rectifier output, regenerative braking, and DC bus voltage regulation, without requiring separate independent systems.
2Manufacturing precision
If existing energy recovery solutions are used, then energy can be recovered during braking, but the DC bus voltage oscillations cannot be regulated to reduce motor current distortion
Solution Approach 1:
The control system continuously monitors the DC bus voltage and adjusts the switching duties of both DC/DC converters to maintain voltage stability. The first converter's switching duty is controlled to regulate the DC bus voltage at a value greater than the rectified voltage, while the second converter's switching duty is adjusted to manage energy flow during braking. This feedback control reduces DC bus voltage oscillations and consequently reduces motor current total harmonic distortion.
3Object-affected harmful factors
If existing energy recovery solutions are used, then energy storage is possible, but the rectifier current total harmonic distortion rate remains above 30%
Solution Approach 1:
The system dynamically adjusts the switching duties of both DC/DC converters based on real-time operating conditions. The first converter's switching duty is controlled to maintain DC bus voltage above the rectified voltage, which actively shapes the rectifier current waveform to reduce harmonics. The second converter dynamically manages energy recovery during braking. This dynamic control simultaneously reduces rectifier current total harmonic distortion below 30% while maintaining efficient energy recovery.
4Ease of operation
If existing energy recovery solutions are used, then basic energy storage is achieved, but the duty cycle of switches is not optimized
Solution Approach 1:
The invention replaces traditional mechanical or simple electronic switching control with advanced pulse-width modulation (PWM) control of the DC/DC converters. The switching duties of both converters are precisely controlled through PWM techniques, optimizing the switching timing and duration to minimize switching losses while achieving the desired voltage amplification and energy recovery functions. This electronic control substitution enables efficient operation across varying load conditions.
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 solution effectively reduces current harmonic distortion, stabilizes the DC bus voltage, enhances motor control, and provides an energy reserve by boosting the DC bus voltage, improving overall drive performance and energy efficiency.
Implementation Method 1
The term 'super-capacitor' (super-capacitor) or 'ultra-capacitor' (ultra-capacitor) designates a known component which is capable of storing a greater quantity of electrical energy than a conventional capacitor
Implementation Method 2
increase the DC bus voltage supplied by the drive rectifier module (boost function), which provides an energy reserve
Implementation Method 3
the DC bus voltage cannot be regulated to reduce the oscillations of the DC bus so as to reduce the rate of distortion of the motor currents
Data Source
Figure 1~2
Figure 3~4d
Figure 5~6
AI summary
The invention relates to a variable speed drive including a continuous power bus having a positive line (16) and a negative line (17), and an inverter module (14) supplied by the continuous bus to provide a variable voltage to an electric charge (M). The drive includes a power recovery device (10) comprising: a first DC/DC converter (20), the output stage of the first converter (20) being connected in series on the positive line of the continuous bus; a second DC/DC converter (30), the input stage of the second converter (30) being connected between the positive line and the negative line of the continuous bus; and an electric power storage module (Cs), connected in parallel to the input stage of the first converter (20) and to the output stage of the second converter (30).