Capacitor Discharge Control in Power Converters
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Solution Overview
Problem
Existing electrical circuits with power semiconductor components, such as IGBTs, face damage or destruction when the intermediate circuit voltage exceeds specified limits, requiring additional components like chopper circuits for voltage regulation, increasing complexity and cost.
Innovation Solution
The method involves discharging the capacitor without additional components by switching power semiconductor components to their conductive state only when the DC voltage is below the maximum voltage or synchronized with the AC voltage, allowing the capacitor to discharge into the power supply network, thereby maintaining voltage within safe limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a chopper circuit is added to discharge the capacitor when intermediate circuit voltage exceeds maximum voltage, then the power semiconductor components are protected from damage, but the device complexity and cost increase
Solution Approach 1:
The patent applies the self-service principle by enabling the converter circuit itself to discharge the capacitor through its existing power semiconductor components. When the intermediate circuit voltage exceeds the maximum voltage, the control device activates the power semiconductor components to create a discharge path, allowing the circuit to regulate its own voltage without requiring external protective circuitry like chopper circuits.
Solution Approach 2:
The patent demonstrates multi-functionality by making the power semiconductor components serve dual purposes: they perform the converter's normal power conversion function and simultaneously act as discharge switches for voltage regulation. This eliminates the need for dedicated protective components, as the existing components are utilized for both operational and protective functions.
2Reliability
If a chopper circuit is added to discharge the capacitor, then the intermediate circuit voltage can be regulated, but the manufacturing cost increases
Solution Approach 1:
The patent reduces manufacturing cost by making the power semiconductor components perform multiple functions. These components handle both the primary power conversion task and the secondary voltage regulation task, eliminating the need for additional protective components that would increase bill of materials cost and assembly complexity.
Solution Approach 2:
By enabling the converter circuit to regulate its own voltage through intelligent control of existing components, the patent eliminates the need for separate protective circuitry. This self-service approach reduces component count, simplifies manufacturing, and lowers overall system cost while maintaining reliable voltage regulation.
3Speed
If power semiconductor components are switched on continuously to discharge the capacitor, then the voltage is regulated quickly, but energy loss increases
Solution Approach 1:
The patent employs periodic action by controlling the power semiconductor components to switch on and off in a regulated manner during capacitor discharge. Rather than maintaining continuous conduction, the control device activates the components in controlled intervals, allowing the capacitor to discharge in a regulated periodic fashion. This reduces unnecessary energy losses while maintaining effective voltage regulation through pulsed discharge action.
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 approach prevents damage to power semiconductor components by safely regulating the intermediate circuit voltage without additional components, reducing complexity and operational effort.
Implementation Method 1
the capacitor can discharge via the resistor and the intermediate circuit voltage thus decreases
Implementation Method 2
switching power semiconductor components to their conductive state
Data Source
Figure 1
Figure 2
AI summary
The method involves connecting network-side power converter (11) with capacitor (15). The serially connected power semiconductor components (18a-18f), are connected in parallel with the capacitor. The power supply network (13) is coupled with power converter. The direct current (DC) voltage (Vdc) of capacitor is determined. The two of the power semiconductor components are switched into its conducting state, so that capacitor discharge towards direction of power supply network, if DC voltage of capacitor is greater than the maximum voltage. An independent claim is included for electrical circuit.