Dynamic Balancing Resistor Control for Series Capacitors
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Solution Overview
Problem
Series-connected electrolytic capacitors exhibit non-ideal voltage sharing due to unequal leakage currents, leading to inefficiencies and precise resistance matching requirements in balancing resistor systems, which results in significant power dissipation and accuracy challenges.
Innovation Solution
An arrangement with adjustable balancing resistor units, comprising a base resistor unit and a control resistor unit connected in series, and a switching device in parallel, allows for dynamic resistance control to maintain energy storage unit voltages within a set range by determining reference voltages based on total series voltage, effectively balancing voltages across capacitors or batteries.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If low resistance values are used in balancing resistors to ensure dominant resistor current in voltage sharing, then voltage balancing is improved, but power dissipation increases significantly
Solution Approach 1:
The patent applies dynamics by making the balancing resistor value adjustable rather than fixed. The controller dynamically changes the resistance value based on the operating state of the power converter. During startup or transient conditions, lower resistance ensures dominant balancing current. During steady-state operation, higher resistance reduces power dissipation. This dynamic adaptation resolves the contradiction between needing low resistance for voltage balancing and avoiding high power loss.
Solution Approach 2:
The patent changes the resistance parameter of the balancing resistor based on operating conditions. The controller monitors system state and adjusts the balancing resistor value accordingly. This parameter change allows the system to optimize between voltage balancing performance and power efficiency at different operational phases, resolving the technical contradiction.
2Reliability
If high accuracy resistance matching is required for series-connected balancing resistors to achieve ideal voltage sharing, then voltage balancing is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent applies self-service by using the controller to actively compensate for resistance mismatches. Instead of relying on precise passive component matching, the system uses active control to measure actual voltages across capacitors and adjust individual balancing resistor values accordingly. This allows the use of standard-tolerance resistors while achieving precise voltage balancing through feedback control.
Solution Approach 2:
The patent implements feedback control where the controller continuously monitors capacitor voltages and adjusts balancing resistor values based on measured deviations from ideal voltage sharing. This closed-loop approach compensates for manufacturing variations in resistor values, eliminating the need for high-precision passive components and reducing manufacturing complexity.
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 solution reduces power dissipation, relaxes resistance tolerance requirements, and provides a cost-effective method for maintaining balanced voltages across series-connected energy storage units, enhancing efficiency and reducing the need for precise resistance matching.
Implementation Method 1
controlling the resistance(s) of one or more of the balancing resistor units
Implementation Method 2
energy storage units for electrical energy, such as capacitors and rechargeable batteries
Data Source
AI summary
An arrangement which includes two or more energy storage units for electrical energy connected in series, and two or more balancing resistor units. Each balancing resistor unit is connected in parallel with one of the energy storage units. The arrangement also includes means for determining a voltage over all of the series-connected energy storage units and means for determining the energy storage unit voltages between poles of the energy storage units. One or more of the balancing resistor units include a base resistor unit and a control resistor unit connected in series and a switching device connected in parallel with the control resistor units. The arrangement further comprises means for determining reference voltages for the energy storage units based on the voltage over all of the series-connected capacitors and means for controlling the switching device to control the resistance of one or more of the balancing resistor units so that the energy storage unit voltage of each energy storage unit is maintained within a set range of the reference voltage for each energy storage unit.