Inverter Circuit Capacitive Energy Store Dimensioning
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Solution Overview
Problem
Existing converter circuits face challenges in dimensioning capacitive energy stores independently of desired current and frequency at the output connection, leading to increased voltage ripple when operating with direct current or alternating current with a direct current component, requiring either external supply or infinitely large capacitors.
Innovation Solution
The method involves controlling power semiconductor switches using control signals formed from voltage signals across inductances and switching functions based on output terminal voltage, allowing for reduced voltage ripple at the capacitive energy stores, thereby allowing capacitive energy storage design to be independent of output current, with control signals generated from current signals and reference signals to manage voltage and current profiles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the converter circuit is operated with direct current or alternating current with a direct current component at the output connection, then the voltage ripple at the capacitive energy stores increases almost to infinity, but the converter circuit can provide the desired current output
Solution Approach 1:
The patent applies periodic switching actions to the power semiconductor switches, creating controlled current circulation between the two partial converter systems. This periodic action enables the capacitive energy stores to be charged and discharged in a controlled manner, preventing voltage ripple from increasing to infinity while maintaining the ability to provide DC or AC with DC component at the output.
Solution Approach 2:
The patent changes the operating parameters by introducing a circulation current between the two partial converter systems. This parameter change allows the system to operate with DC or AC with DC component at the output while maintaining controlled voltage ripple through the periodic exchange of energy between the two systems.
2Speed
If the frequency of the output current is reduced below the design frequency, then the voltage ripple at the capacitive energy stores increases, but the converter circuit can operate at lower frequencies
Solution Approach 1:
The patent implements periodic switching control that maintains controlled voltage ripple regardless of the output current frequency. The periodic action creates a circulation current between the two partial converter systems that compensates for the effects of reduced frequency, allowing the converter to operate at lower frequencies without excessive voltage ripple.
3Quantity of substance
If the capacitive energy stores are dimensioned to handle direct current operation, then the capacitors must be infinitely large or externally supplied, but the converter circuit can provide stable DC output
Solution Approach 1:
The patent divides the converter circuit into two partial converter systems connected in series, each with its own capacitive energy store. This segmentation allows the capacitive energy stores to be dimensioned independently and to a reasonable size, as the two systems work together to provide the required DC output without requiring infinitely large capacitors or external supply.
Solution Approach 2:
The patent changes the system configuration by introducing a second partial converter system in series, which fundamentally alters the energy storage requirements. This parameter change enables the use of finite, practically dimensioned capacitive energy stores while maintaining stable DC output capability.
Data Source
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AI summary
The invention relates to a method for operating an inverter circuit, wherein the inverter circuit comprises at least two phase modules (11), wherein each phase module (11) comprises a first and a second partial inverter system (1), the partial inverter systems (2) are serially interconnected for each phase module (11), the connection point of the two partial inverter systems (1, 2) forms an output connection (A), each partial inverter system (1, 2) comprises an inductance (L1, L2) and at least one two-pole switching cell (3) serially connected relative thereto, and each switching cell (3) comprises two actuatable bidirectional power semiconductor switches that are connected in series and that have controlled unidirectional current flow direction and a capacitive energy store connected in parallel to the serial connection of the power semiconductor switch. According to said method, the power semiconductor switch of the switching cells (3) of the first partial inverter system (1) is actuated by means of an actuating signal (S1) and the power semiconductor switch of the switching cells (3) of the second partial inverter system (2) is actuated by means of a further actuating signal (S2). In order to be able to dimension the capacitive energy store of the inverter circuit independent of the desired current at the output connection of the inverter circuit, that is, of the frequency thereof, the actuating signal (S1) for each phase module (11) is formed of a voltage signal (VL) by means of the inductivities (L1, L2) and a circuit function (a1) for the power semiconductor switch of the switching cells (3) of the first partial inverter system (1), the further actuating signal (S2) is formed of a voltage signal (VL) by means of the inductivities (L1, L2) and a circuit function (a2) for the power semiconductor switch of the switching cells (3) of the second partial inverter system (2), and the circuit functions (a1, a2) are formed by means of a voltage signal (VA) with respect to the voltage (Vu) at the output connection (A) and a selectable reference signal (Vref), wherein the voltage signals (VA) are selected to be in phase with respect to the voltage (Vu) at the output connections (A) of the phase modules (11).