Pi Source Inverter Bypassing Inductor to Eliminate DC Bus Resonance
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Solution Overview
Problem
The existing systems for hybrid electric vehicles (HEVs) with variable frequency drives suffer from resonant oscillations on the DC bus, which limit the performance and lifetime of the starter-generator and increase emissions, preventing it from operating at its full designed power.
Innovation Solution
A system with a battery, a first capacitor in parallel, an inductor in series, and two diodes is used to bypass the inductor during motor mode, eliminating resonant oscillations by ensuring no energy is stored in the inductor during this mode, and using an L-C filter during re-generation mode to filter the charging current and meet EMC constraints.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If an inductor is used in series between capacitors to filter battery charging current during re-generation mode, then EMC emissions are eliminated, but resonant oscillation occurs during motor mode that limits starter-generator power and reduces component lifetime
Solution Approach 1:
The patent applies the dynamics principle by making the inductor's participation in the circuit dynamic rather than static. A switch (such as a MOSFET or IGBT) is introduced to control the inductor's connection to the circuit based on operational mode. During re-generation mode, the switch closes to include the inductor for filtering and eliminating EMC emissions. During motor mode, the switch opens to bypass the inductor, preventing resonant oscillation and protecting components. This dynamic configuration allows the system to optimize performance for each operational mode while avoiding the harmful effects of the inductor in inappropriate modes.
2Object-affected harmful factors
If an inductor is used to filter battery charging current, then EMC constraints are met, but energy is stored in the inductor during motor mode causing resonant oscillation and power loss
Solution Approach 1:
The patent applies the dynamics principle by making the inductor's participation in the circuit dynamic rather than static. A switch (such as a MOSFET or IGBT) is introduced to control the inductor's connection to the circuit based on operational mode. During re-generation mode, the switch closes to include the inductor for filtering and eliminating EMC emissions. During motor mode, the switch opens to bypass the inductor, preventing resonant oscillation and protecting components. This dynamic configuration allows the system to optimize performance for each operational mode while avoiding the harmful effects of the inductor in inappropriate modes.
3Power
If the starter-generator operates at full designed power, then vehicle performance is improved, but resonant oscillation damages components and limits operational lifetime
Solution Approach 1:
The patent applies the dynamics principle by making the inductor's participation in the circuit dynamic rather than static. A switch (such as a MOSFET or IGBT) is introduced to control the inductor's connection to the circuit based on operational mode. During re-generation mode, the switch closes to include the inductor for filtering and eliminating EMC emissions. During motor mode, the switch opens to bypass the inductor, preventing resonant oscillation and protecting components. This dynamic configuration allows the system to optimize performance for each operational mode while avoiding the harmful effects of the inductor in inappropriate modes.
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
This configuration stabilizes the system, allows the starter-generator to operate at full power, reduces current ratings, and extends the lifetime of components by eliminating resonant oscillations and power losses, while meeting EMC requirements.
Implementation Method 1
a first diode connected in series with the inductor; a second diode connected in parallel with the inductor and the first diode
Implementation Method 2
an inductor connected in series with the first capacitor; a first diode connected in series with the inductor
Implementation Method 3
The Energy Stored in the inductor 110 may be calculated as follows: EL = 0.5 * L * I^2
Implementation Method 4
a first capacitor connected in parallel with the battery; a second capacitor connected in series with the first diode
Implementation Method 5
The Resonant Oscillation on the L-C filter 116: the current flowing in the inductor 110 is 180° lagging the current flowing in the first and second capacitors 118, 120
Data Source
AI summary
A system for reducing a resonant oscillation on a direct current bus of a power inverter/converter for an electric machine having a variable frequency drive is disclosed. The system includes a battery, a first capacitor connected in parallel with the battery; an inductor connected in series with the first capacitor; a first diode connected in series with the inductor; a second diode connected in parallel with the inductor and the first diode; a second capacitor connected in series with the first diode; and a starter-generator connected to the second capacitor. During a re-generation mode for charging the battery, a re-generation current flows from the starter-generator to the battery, passing through the first diode and the inductor and bypassing the second diode. During a motor mode, a motor current flows from the battery to the starter-generator, passing through the second diode and bypassing the first diode and the inductor.