Three-Circuit Voltage Spike Protection for Photovoltaic Systems
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Photovoltaic systems with freely floating potentials face challenges in operating at high voltages without exceeding permissible limits, risking module and inverter destruction, especially when disconnected from the grid or experiencing ground faults, leading to potential overvoltage issues that can damage components.
Innovation Solution
A protective device with switching elements connected to the DC voltage input of the inverter, controlled by a device that opens when voltage limits are exceeded, ensuring the positive and negative poles are short-circuited to prevent overvoltage, using a control device to manage switching elements and limit values to safeguard against excessive voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the number of modules per string is increased to operate at higher voltages (e.g., 1000V), then the use of insulation resistance and operating efficiency are improved, but the risk of exceeding permissible voltage limits during no-load operation increases, leading to potential destruction of modules and inverter
Solution Approach 1:
The protective device performs preliminary action by detecting voltage conditions before dangerous overvoltage occurs. The control device continuously monitors the voltage between positive and negative poles and preemptively activates switching elements to short-circuit the poles when voltage approaches unsafe levels, preventing module and inverter destruction before it can occur.
Solution Approach 2:
The protective device acts as an intermediary between the photovoltaic generator and the inverter. It includes switching elements (first and second switching elements) that can be opened to disconnect the inverter from the photovoltaic generator, and a third switching element that short-circuits the poles. This intermediary structure enables safe operation at high voltages by mediating the voltage conditions between the two components.
2Reliability
If a short-circuit switch is placed between positive and negative poles to protect against overvoltage, then system protection is improved, but the device complexity and cabling requirements increase
Solution Approach 1:
The protective device integrates multiple functions into a single unified system. It combines voltage detection, control logic, and three switching elements that can operate in different modes: the first and second switching elements disconnect the inverter when voltage exceeds thresholds, while the third switching element short-circuits the poles. This multi-functional integration reduces overall system complexity compared to separate protective devices.
Solution Approach 2:
The patent merges the protective switching elements and control device into an integrated protective device that is connected in parallel to the photovoltaic generator. The first, second, and third switching elements are combined in a single protective unit with unified control logic, reducing the number of separate components and simplifying installation and maintenance.
3Adaptability or versatility
If the system operates with freely floating potentials to accommodate ground faults, then adaptability is improved, but voltage control becomes difficult, risking overvoltage conditions
Solution Approach 1:
The control device implements feedback by continuously monitoring the voltage between the positive and negative poles of the photovoltaic generator. When the voltage exceeds predetermined threshold values, the control device automatically activates the appropriate switching elements to restore safe voltage conditions. This closed-loop feedback mechanism enables the system to maintain voltage control while operating with freely floating potentials and tolerating ground faults.
Data Source
Figure 1
AI summary
A photovoltaic system (1) comprises a photovoltaic generator (3) which has several parallel strings (7) of series-connected photovoltaic modules (9), the strings having a positive and a negative terminal (11 and 13, respectively). The string voltage is determined by the number of series-connected photovoltaic modules and is greater than 1000 volts when the photovoltaic generator is open-circuited. An inverter (5), whose DC input is connected to the two terminals, can be connected to a power supply network (L1, L2, L3) on its output side. The positive and negative terminals can be connected to the DC input of the inverter via a first and a second switching element (17, 19), respectively.A control device (23) generates two control signals (S1, S2) that cause at least one of the two switching elements (17, 19) to open when the voltage of the positive terminal relative to ground exceeds a first predetermined limit value or when the voltage of the negative terminal relative to ground falls below a second predetermined limit value. A third control signal (S3) generated by the control device initiates the closing of a third switching element (21) located between the positive and negative terminals. The closing occurs while the first and/or the second switching element is opening or when at least one of the two switching elements is open. The closed third switching element connects the positive and negative terminals of the photovoltaic generator. The arrangement is designed to safely disconnect the photovoltaic generator if a voltage limit value is exceeded at the PV modules.