Power Converter Control for Stable 2-Level/3-Level Switching
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Solution Overview
Problem
Conventional power converters switching between 2-level and 3-level operations experience voltage errors and resulting variations in current and torque due to unsuppressed voltage differences during mode transitions.
Innovation Solution
A control unit for a power converter that performs ON/OFF control of semiconductor elements to switch between 2-level and 3-level operations, using a compensation value to correct voltage errors and synchronize mode transitions with carrier signals, thereby stabilizing the operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the power converter switches between 2-level operation and 3-level operation based on loss reduction, then energy efficiency is improved, but voltage error occurs during mode transition causing current and torque variation
Solution Approach 1:
The control unit determines the mode transition timing in advance by comparing the absolute value of the fundamental wave component of the output voltage with a reference value. This preliminary determination allows the system to prepare for the transition before it occurs, ensuring smooth switching between 2-level and 3-level operation modes without voltage errors or current/torque variations.
Solution Approach 2:
The control unit continuously monitors the fundamental wave component of the output voltage and uses this feedback to determine when to transition between operation modes. By basing the transition decision on actual voltage measurements rather than predetermined timing, the system adapts to real-time conditions and maintains voltage stability during mode transitions.
2Object-generated harmful factors
If 3-level operation is used, then harmonic current and ripple current are reduced, but the number of semiconductor elements increases leading to higher conduction loss
Solution Approach 1:
The power converter dynamically switches between 2-level operation and 3-level operation based on real-time voltage conditions. The control unit compares the fundamental wave component of the output voltage with a reference value and transitions modes accordingly, allowing the system to adapt its configuration to minimize both harmonic content and conduction losses under different operating conditions.
Solution Approach 2:
The system changes its operational parameters by switching between two distinct operation modes: 2-level operation for conditions where conduction loss is more critical, and 3-level operation for conditions where harmonic and ripple current reduction is more important. This parameter switching enables the system to optimize performance across varying load and voltage conditions.
3Loss of energy
If 2-level operation is used, then conduction loss is reduced, but the number of semiconductor elements decreases leading to increased harmonic current and ripple current
Solution Approach 1:
The power converter dynamically switches between 2-level operation and 3-level operation based on real-time voltage conditions. The control unit compares the fundamental wave component of the output voltage with a reference value and transitions modes accordingly, allowing the system to adapt its configuration to minimize both harmonic content and conduction losses under different operating conditions.
Solution Approach 2:
The system changes its operational parameters by switching between two distinct operation modes: 2-level operation for conditions where conduction loss is more critical, and 3-level operation for conditions where harmonic and ripple current reduction is more important. This parameter switching enables the system to optimize performance across varying load and voltage conditions.
Data Source
AI summary
A controlling circuitry of a power converter performs switchover control for, on the basis of a level specification signal, switching between a 3-level operation mode of outputting AC voltage composed of 3-level voltages at a positive side and a negative side of a DC circuit and a voltage-division point of DC voltage between the positive side and the negative side of the DC circuit by performing ON/OFF control of semiconductor elements, and a 2-level operation mode of outputting AC voltage composed of 2-level voltages at the positive side and the negative side of the DC circuit by performing ON/OFF control of the semiconductor elements, and switches a compensation value for compensating error between a voltage command and AC voltage, between a case of the 2-level operation mode and a case of the 3-level operation mode.