Voltage Compensation Apparatus for PV Systems
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Solution Overview
Problem
Conventional voltage compensation apparatuses for photovoltaic systems are costly and prone to circulating currents, which affect the reliability and efficiency of the system in preventing potential induced degradation (PID) effects, especially in systems with multiple PV inverters connected in parallel.
Innovation Solution
A voltage compensation apparatus that includes a current direction limiting module and a compensation power supply, connected between the output terminal of a converter and the ground, allowing unidirectional current flow to clamp the output voltage to the compensation power supply or ground, effectively preventing PID by raising or lowering the voltage of the photovoltaic system relative to the ground.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a voltage compensation apparatus is added on the direct current side of each photovoltaic inverter, then the PID effect can be prevented or reduced, but the cost increases and circulating current problems occur
Solution Approach 1:
The patent divides the voltage compensation function into separate modules that can be independently configured for each phase. The compensation apparatus is segmented into a compensation power supply unit, a switching unit, and a coupling unit, allowing selective deployment on different phases based on system requirements rather than requiring full compensation on all phases simultaneously.
Solution Approach 2:
The patent implements voltage compensation selectively on specific phases where PID issues are detected or anticipated. The system allows different compensation strategies for different phases (e.g., compensating only the neutral point on certain phases while leaving others uncompensated), optimizing resource allocation and reducing overall system complexity and cost.
2Reliability
If voltage compensation is implemented on all three phases, then PID prevention is maximized, but cost and device complexity increase significantly
Solution Approach 1:
The patent implements voltage compensation partially rather than fully across all three phases. The system allows selective activation of compensation on individual phases based on actual PID risk assessment, system configuration, and operational requirements. This partial action approach achieves sufficient PID prevention while significantly reducing the number of compensation apparatuses needed and lowering overall system complexity and cost.
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
The solution effectively prevents or reduces PID effects by utilizing the unidirectional current limiting module to clamp the output voltage, enhancing the reliability and efficiency of the photovoltaic system while reducing costs by eliminating the need for multiple voltage compensation apparatuses.
Implementation Method 1
The current direction limiting module is any one of: a diode, a body diode of a Metallic Oxide Semiconductor Field Effect Transistor (MOSFET), an anti-parallel diode of an Insulated Gate Bipolar Transistor (IGBT), a thyristor and a zener diode
Data Source
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AI summary
A voltage compensation apparatus for a photovoltaic system and a photovoltaic system are provided. The voltage compensation apparatus includes a current direction limiting module (300) and a compensation power supply (400) connected in series; or only includes a current direction limiting module (300). The current direction limiting module (300) includes at least one limiting device configured to conduct a current in a unidirectional manner. The voltage compensation apparatus is connected between the output terminal of the converter (100) and the ground. The photovoltaic system includes: a photovoltaic array, a converter (100), a transformer (200) and the voltage compensation apparatus. An output terminal of the converter (100) is connected with a primary side of the transformer (200), and an input terminal of the converter (100) is connected with the photovoltaic array. The voltage compensation apparatus is configured to raise or lower a voltage at the output terminal of the converter (100). With the limiting device which conducts a current in a unidirectional manner, the lowest or highest value of the output voltage of the converter (100) can be clamped to the voltage of the compensation power supply (400) or be clamped to the ground.