Photovoltaic Inverter Separation Point Testing
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Solution Overview
Problem
Existing methods for testing the separation point of a photovoltaic inverter are complex, costly, and require significant hardware, often causing leakage currents and failing to function in standalone or isolated networks without a mains voltage.
Innovation Solution
A method using an auxiliary voltage generated by the photovoltaic inverter to test the separation point, where switching contacts are alternately closed and opened, allowing for quick and cost-effective functionality checks without relying on mains voltage, thus avoiding leakage currents and reducing hardware requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If mains voltage is used to test switching contacts, then the separation point can be tested, but leakage currents are generated that trigger the residual current switch
Solution Approach 1:
A current-limiting impedance is introduced as an intermediary element in the test circuit. This impedance limits the test current to a safe level that prevents triggering the residual current switch while still allowing voltage measurements to detect switching contact functionality. The impedance acts as a mediator between the test voltage source and the separation point, enabling safe testing.
Solution Approach 2:
The test method changes the electrical parameters of the test circuit by using a current-limiting impedance to restrict the test current magnitude. By controlling the current parameter within safe limits, the method enables testing without generating harmful leakage currents that would trigger protective devices.
2Measurement precision
If complex test equipment is used to test the separation point, then measurement accuracy is improved, but hardware cost and complexity increase
Solution Approach 1:
The test method is designed to be universally applicable to different inverter types and network configurations without requiring specialized test equipment. The same basic test circuit with voltage source and current-limiting impedance can test various separation point configurations, making the method multi-functional and eliminating the need for complex dedicated test devices.
Solution Approach 2:
The test method uses a simplified electrical model that replicates the essential testing function without copying the complexity of the actual separation point or requiring expensive measurement equipment. By measuring voltages at key points and deriving contact status, the method creates a functional copy of the testing capability using minimal hardware.
3Reliability
If traditional test methods are used, then separation point functionality can be checked, but the testing process is time-consuming and requires significant hardware effort
Solution Approach 1:
The test procedure is designed to be performed as a preliminary check before grid connection or after maintenance. The simplified test circuit allows for rapid preliminary assessment of separation point functionality without requiring complex setup or lengthy measurement sequences, enabling quick verification before critical operations.
Solution Approach 2:
The test method extracts only the essential testing function from complex traditional test systems. By removing unnecessary hardware components and measurement steps, the method achieves the core goal of separation point verification with minimal equipment and time investment.
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
Enables rapid and inexpensive testing of separation point functionality with minimal hardware, applicable to various network types, including standalone and isolated systems, without triggering residual current switches.
Implementation Method 1
an auxiliary voltage generated by the photovoltaic inverter, in particular its output DC-AC converter, is applied
Implementation Method 2
the first switching contacts of the separation point are alternately closed and the second switching contacts are opened and then the second switching contacts are closed and the first switching contacts are opened
Implementation Method 3
the voltages between the output of each line of the separation point and the intermediate circuit potential are measured for each switching pattern of the switching contacts and from the measured voltages for each switching pattern of the switching contacts the functionality of each switching contact is derived
Data Source
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AI summary
The invention relates to a method for testing a disconnection point (12) of a photovoltaic inverter (1) and to a photovoltaic inverter (1) of this type. According to the invention, in a testing mode, an auxiliary voltage (U_Lx) is applied between the input (E_Lx) of each line (Lx) of the disconnection point (12) and a DC link potential (M); in each case, the first switching contacts (SW_Lx,1) are closed and the second switching contacts (SW_Lx,2) are opened alternately and vice versa, according to a switching pattern; and, for each switching pattern, the voltages (U_Lx,GD; U_MN) between the output (A_Lx) of each line (Lx) of the disconnection point (12) and the DC link potential (M) are measured, and the functionality of each switching contact (SW_Lx,j) is derived from the measured voltages (U_Lx,GD; U_MN).