Inverter Phase Synchronization via Wobble Signal PLL
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Solution Overview
Problem
Existing grid-connected inverters with frequency-varying auxiliary signals face challenges in preventing compensating currents when operated in parallel, as known synchronization methods are ineffective for swept auxiliary voltage signals, leading to unwanted current loads on electronic components.
Innovation Solution
Incorporating a further synchronization unit for phase synchronization of the periodic wobble signal with the power supply grid, using PLL circuits with frequency converters and correction signal generators to ensure all inverters operate with synchronized frequency and phase, preventing compensating currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If multiple inverters are operated in parallel with asynchronous auxiliary signals, then system capacity is increased, but high-frequency equalizing currents occur between inverters
Solution Approach 1:
Before the inverters operate in parallel to increase system capacity, the synchronization unit performs preliminary phase alignment of their auxiliary signals. This pre-synchronization ensures that all inverters switch at the same phase positions despite using frequency-varying signals, thereby preventing the voltage differences that would otherwise drive high-frequency equalizing currents between the parallel-connected inverters.
2Ease of operation
If fixed frequency auxiliary signals are used, then synchronization between parallel inverters is easier, but electromagnetic interference amplitude is higher and filter requirements increase
Solution Approach 1:
The synchronization unit performs preliminary phase alignment of the frequency-varying auxiliary signals from multiple inverters. By pre-synchronizing the phase positions before the inverters operate in parallel, the system maintains ease of operation comparable to fixed frequency signals, while simultaneously benefiting from the reduced electromagnetic interference amplitude that frequency variation provides.
Solution Approach 2:
The system changes the frequency parameter of the auxiliary signals from fixed to varying frequency, while using the synchronization unit to maintain phase alignment. This parameter change reduces electromagnetic interference amplitude by distributing energy across a wider frequency spectrum, while the synchronization unit ensures that phase differences do not cause compensating currents, thus maintaining operational ease.
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 synchronizes the frequency and phase of periodic auxiliary signals across multiple inverters, preventing compensating currents and reducing electromagnetic interference, allowing for reduced inductance in output filters and minimizing material costs.
Implementation Method 1
The synchronization unit has a PLL circuit with which the periodic auxiliary signal can be synchronized in terms of phase
Implementation Method 2
provision is made for the periodic wobble signal to be synchronized in terms of phase with the power supply network via a frequency converter
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), having an output bridge arrangement (230) 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 (230), the frequency of which auxiliary signal varies according to a predefined periodic wobble signal (Umod), and having a synchronization unit (243) for phase synchronisation of the auxiliary signal with the energy supply network (5), wherein the synchronization unit (243) is configured to set a predefined phase offset (ΔΦ0) of the periodic auxiliary signal in relation to a phase of the energy supply network (5). The inverter (2) is characterized in that an additional synchronization unit (245) is present which is configured for phase synchronization of the periodic wobble signal (Umod) with the energy supply network (5). The synchronization unit (243) and the additional synchronization unit (245) each comprise a phase-locked loop circuit, and the periodic wobble signal (Umod) is passed via a correction signal generator (216) and an adder (203) for oscillation suppression on a control section of the phase-locked loop circuit of the synchronization unit (243). The invention also relates to an arrangement having at least two inverters (2) of this type, and to a method for operating an inverter arrangement of this type.