Multi-Inverter Bus Synchronization for DC Ripple Reduction
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Solution Overview
Problem
In motor vehicles with multiple traction motors, existing methods for synchronizing inverters connected to a direct current network fail to maintain a stable phase relationship between clock signals over time due to component tolerances, leading to alternating current load ripples and increased capacitance requirements.
Innovation Solution
A method where a common communication bus is used to send synchronization messages between control units of inverters, allowing for regular synchronization of clock signals with a fixed or variable period, which compensates for phase differences and maintains a predetermined phase reference, thereby reducing alternating current load and ripple.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If inverters are synchronized using existing methods with component tolerances, then initial phase alignment is achieved, but phase relationship stability deteriorates over time
Solution Approach 1:
The patent implements periodic resynchronization at defined resynchronization points during operation. The control units periodically exchange synchronization messages and adjust their clock signals to maintain phase alignment, counteracting the drift caused by component tolerances over time
Solution Approach 2:
The patent employs feedback mechanisms where control units continuously monitor phase relationships and exchange synchronization status information via communication buses. Based on this feedback, control units adjust their clock signals to maintain stable phase relationships despite component variations
2Reliability
If additional communication links are added for synchronization, then synchronization reliability is improved, but device complexity increases
Solution Approach 1:
The patent makes the existing communication buses serve dual purposes: their original function plus synchronization message transmission. By reusing existing communication infrastructure for synchronization, the patent avoids adding dedicated synchronization communication links while maintaining reliable synchronization
Solution Approach 2:
The patent combines synchronization communication with existing control communication buses. Multiple functions (control signals, status monitoring, and synchronization) are merged into the same communication infrastructure, reducing overall system complexity
3Object-generated harmful factors
If higher capacitance is used to dissipate AC ripples, then ripple dissipation capability is improved, but installation space and manufacturing costs increase
Solution Approach 1:
The patent converts the harmful AC ripples generated by inverter switching into beneficial effects by synchronizing inverters to operate at different phases. The AC ripples from multiple inverters cancel each other out when properly phased, dissipating harmful effects without requiring large capacitors
Solution Approach 2:
The patent changes the operational parameters of inverters by introducing phase shifts between their clock signals. By adjusting the phase parameter rather than increasing capacitance, the system achieves better ripple dissipation with smaller intermediate circuit capacitors
Data Source
AI summary
A method includes operating at least two inverters connected to a direct current network. Each inverter includes a control unit connected to a common communication bus and in each case at least one switching element, which is controlled by the control unit of the inverter with a clock signal. The common communication bus is connected to at least one further control unit, which in each case sends a message of a message type via the communication bus at different points of times. The reception of one of the messages of the message type in the control units of the inverters triggers a synchronization of their clock signals.