Converter Circuit Voltage Ripple Reduction
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Solution Overview
Problem
Converter circuits struggle to design capacitive energy stores independently of the desired current at the output connection, particularly when dealing with varying frequencies or the production of direct or alternating currents with direct-current components, as existing designs result in increased voltage ripple.
Innovation Solution
The method involves controlling power semiconductor switches in series-connected partial converter systems using control signals formed from voltage oscillation signals across inductances and switching functions relative to the output connection voltage, allowing for reduced voltage ripple and independent design of capacitive energy stores.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the capacitive energy stores are designed for a given maximum current and frequency, then the voltage ripple remains within a predetermined fluctuation range, but the voltage ripple rises significantly when operating at lower frequencies or with direct current components
Solution Approach 1:
The control method dynamically adjusts the switching functions based on the actual operating conditions (current frequency and type). By continuously adapting the control signals to match the desired output current characteristics, the system maintains optimal voltage ripple performance across varying frequencies and current types without requiring redesign of the capacitive energy stores
Solution Approach 2:
The invention changes the control parameters (switching functions derived from voltage oscillation signals and reference signals) rather than changing the physical parameters of the capacitive energy stores. This allows the same hardware design to operate effectively across different frequencies and current types by simply adjusting the control signals
2Adaptability or versatility
If the capacitive energy stores are designed to handle direct current operation, then they would need to be infinitely large or externally fed, but this increases device complexity and cost
Solution Approach 1:
The control system uses feedback from the voltage oscillation signal across the inductances and the voltage at the output connection to continuously adjust the switching functions. This feedback mechanism enables the system to maintain stable direct current operation with standard-sized capacitive energy stores by dynamically compensating for energy fluctuations
Solution Approach 2:
The same converter circuit and capacitive energy stores can operate in multiple modes (AC output, DC output, varying frequencies) without requiring different hardware designs. The universal control method enables a single design to serve multiple functions across different operating conditions
3Device complexity
If standard control methods are used for the power semiconductor switches, then the control circuits are simple, but the voltage ripple increases when operating outside the design frequency
Solution Approach 1:
The control method prepares the switching functions in advance based on the desired output current characteristics before actual operation. By pre-calculating the appropriate switching functions from the voltage oscillation signal and reference signal, the system ensures optimal voltage ripple control is ready before operation begins, regardless of the operating frequency or current type
Data Source
AI summary
An exemplary method is disclosed for operation of a converter circuit having first and second partial converter systems, the partial converter systems being connected in series to one another via two series-connected inductances. A junction point of the two series-connected inductances forms an output connection. Each partial converter system can include at least one two-pole switching cell, each switching cell having two series-connected controllable bidirectional power semiconductor switches. The power semiconductor switches in the switching cells of the first and second partial converter system are controlled by first and second control signals. A capacitive energy store in the converter circuit can be designed independent of desired current at the output connection of the converter circuit.