Grid-Connected Inverter Phase Offset for Equalizing Current Suppression
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Solution Overview
Problem
Inverter arrangements with inductively coupled inverters via a transformer experience problematic equalizing currents, and existing methods require the transmission of drive signals or fail to completely suppress compensating currents.
Innovation Solution
The inverter arrangement employs a phase synchronization unit with a PLL circuit to set a predetermined phase offset for the periodic auxiliary signal, ensuring that the switching times of the inverters are synchronized with the power supply network, eliminating equalizing currents without the need for control signal transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If inverters are inductively coupled via a transformer to feed current into the power supply grid, then power output capability is improved, but equalizing currents occur between the inverters causing additional current loads on power semiconductor switches
Solution Approach 1:
The patent applies parameter changes by introducing a phase offset between the periodic auxiliary signals of different inverters. Specifically, the switching times are adjusted so that voltage ripples occur at different phases, preventing simultaneous peak voltages that would cause equalizing currents. This parameter modification (phase shifting) resolves the contradiction by maintaining power output capability while eliminating the harmful equalizing currents between inductively coupled inverters
2Object-generated harmful factors
If master-slave control with drive signal transmission is used to synchronize inverters, then equalizing currents are suppressed, but device complexity and communication requirements increase
Solution Approach 1:
The patent applies the self-service principle by enabling each inverter to autonomously determine its switching times based on its own periodic auxiliary signal with a predetermined phase offset. Each inverter independently generates its control signals without requiring communication with master or slave inverters, thereby suppressing equalizing currents while eliminating the need for complex drive signal transmission systems
Solution Approach 2:
The patent applies segmentation by dividing the control function into independent segments for each inverter. Instead of a centralized master controller, each inverter operates as an independent control unit with its own phase-offsetted auxiliary signal, allowing autonomous synchronization without inter-inverter communication infrastructure
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 effectively prevents compensating currents between inductively coupled inverters, allowing for synchronized operation without transmitting drive signals, even with three-winding transformers, which are less complex and cheaper than conventional four-winding transformers.
Implementation Method 1
The inverter arrangement employs a phase synchronization unit with a PLL circuit to set a predetermined phase offset for the periodic auxiliary signal, ensuring that the switching times of the inverters are synchronized with the power supply network
Implementation Method 2
Grid-connected inverters are used in energy supply systems... feeding current via a transformer into an energy supply network, the inverters being inductively coupled to one another on the AC side
Data Source
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AI summary
The invention relates to a mains-coupled inverter (2) for feeding current into an energy supply network (5) via a transformer (4), which inverter has an output bridge arrangement which is driven via a pulse width modulator (241), wherein a periodic auxiliary signal is used to determine switching times of the output bridge arrangement. The inverter (2) also has a synchronization unit (241) for synchronizing the phase of the auxiliary signal with the energy supply network (5). The inverter (2) is distinguished by the fact that the synchronization unit (241) is set up to set a predefined phase offset (ΔΦ0) of the periodic auxiliary signal with respect to a phase of the energy supply network (5). The invention also relates to an inverter arrangement having at least two such mains-coupled inverters (2) which are inductively coupled to one another on the AC side, and to a method for operating an inverter arrangement.