Photovoltaic Inverter Separation Point Relay Functionality Check
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Solution Overview
Problem
Existing methods for checking the separation point between a photovoltaic inverter and a power supply network with multiple phases and a neutral conductor require complex circuitry and increased costs due to the need for voltage measurements at multiple positions, and regular checks of relay functionality are necessary to prevent voltage supply issues if relays fail.
Innovation Solution
The method involves using single-pole relays connected in a switching pattern to check the functionality of the separation point by measuring voltage at least one phase with respect to the neutral conductor upstream of the separation point, comparing the measured values to assigned voltage values, and using two independent controllers connected by a data bus to control and evaluate the switching contacts, minimizing the number of measuring operations and switching states, which prolongs relay life and reduces leakage currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If voltage measurements are performed at multiple positions to check separation point functionality, then measurement accuracy is improved, but device complexity and cost increase
Solution Approach 1:
The patent combines multiple voltage measurements taken at different positions into a single evaluation process. By measuring voltage at one position (upstream of the separation point) and comparing it against expected values that account for the switching states of multiple relays, the system achieves comprehensive relay functionality checking without requiring physical measurement at each relay location. This merging of measurement and evaluation functions reduces circuitry complexity while maintaining measurement accuracy.
2Reliability
If regular relay functionality checks are performed, then system reliability is improved, but relay wear increases due to frequent switching operations
Solution Approach 1:
The system performs preliminary relay functionality checks by measuring voltage in different switching states and comparing measured values against pre-stored reference values. This allows the system to detect relay faults before they cause system failures, ensuring reliability without requiring continuous or frequent switching operations. The preliminary evaluation based on voltage comparison enables periodic checking with extended intervals between tests.
Solution Approach 2:
The patent implements periodic relay functionality checks by systematically cycling through different relay switching states and performing voltage measurements at defined intervals. Rather than continuous monitoring that would cause excessive relay wear, the system periodically evaluates relay status by stepping through switching states and comparing voltage measurements against reference values, thereby balancing reliability assurance with relay service life extension.
3Measurement precision
If multiple switching states are used for relay checking, then measurement coverage is improved, but relay wear and checking time increase
Solution Approach 1:
The patent makes the voltage measurement process universal by using a single measurement approach that works across multiple relay switching states. The same measurement circuit and evaluation method are used regardless of which relays are in which states, allowing comprehensive checking of all relays through a unified process. This multi-functional approach enables the system to evaluate different relay configurations without requiring separate measurement procedures for each state.
Solution Approach 2:
The system efficiently handles multiple switching states by changing the interpretation parameters rather than the measurement process itself. The controller adjusts the expected voltage values based on the current switching state configuration, allowing the same physical measurement to yield different evaluation results appropriate for each relay state. This parameter-based adaptation enables comprehensive relay checking across multiple states without increasing checking time or complexity.
Data Source
AI summary
The invention relates to a method for checking a separation point (14) between a photovoltaic inverter (1) and a power supply network (7) having multiple phases (L1, L2, L3) and a neutral conductor (N), wherein multiple switching contacts of the separation point (14) are controlled by the photovoltaic inverter (1), and to a photovoltaic inverter (1). To allow a simple and quick check of the functionality of the separation point (14), the switching contacts of the separation point (14) are each formed by single-pole relays (15-22) and switched in steps according to a switching pattern. For checking switching contacts, a voltage (26, 27, 28) is measured at at least one phase (L1, L2, L3) with respect to the neutral conductor (N), upstream of the separation point (14), and compared to voltage values assigned in accordance with the switching pattern, thereby to deduce the functionality of the switching contacts.