DC Bus Voltage Control for PV Micro-Converter Safety
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Solution Overview
Problem
Existing photovoltaic electricity production systems face challenges such as reduced productivity due to shading or dirt on panels, voltage imbalances, and electrical safety concerns, particularly during maintenance, and are reliant on complex communication systems that increase the risk of electronic failure.
Innovation Solution
A control system utilizing micro-converters that autonomously manage power injection into the DC bus based on voltage thresholds, with a DC bus management device that includes a discharge system and an astronomical clock, allowing operation without integrated communication, ensuring safe and efficient energy production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If integrated communication systems are used to control photovoltaic modules, then control capability and productivity are improved, but device complexity and probability of electronic failure increase
Solution Approach 1:
The invention extracts the communication function from the control architecture by using voltage-level signaling through the DC bus instead of integrated communication systems. This removes complex electronic communication components while maintaining control capability through simple voltage-based signals that indicate operational states and coordinate micro-converter operations.
Solution Approach 2:
The DC bus voltage serves as an intermediary medium for control signaling. Instead of direct electronic communication between controllers and micro-converters, the system uses voltage levels on the DC bus to convey control information, eliminating the need for complex communication electronics while maintaining system coordination.
2Use of energy by moving object
If voltage is always present on the DC bus even during inverter shutdown, then continuous power availability is maintained, but electrical safety during maintenance is compromised
Solution Approach 1:
The invention implements dynamic voltage control on the DC bus by enabling the micro-converters to actively discharge the bus voltage through their switching operation. This dynamic discharge capability allows the system to rapidly reduce voltage to safe levels during maintenance while maintaining voltage availability during normal operation, creating a flexible safety mechanism responsive to operational state.
Solution Approach 2:
The system prepares for safety requirements in advance by equipping micro-converters with the capability to discharge DC bus voltage. This prior preparation ensures that when maintenance is needed, the voltage can be rapidly reduced to safe levels without requiring external intervention or additional safety equipment, cushioning against potential electrical hazards.
3Power
If photovoltaic modules are connected in series to increase voltage, then power output is improved, but sensitivity to shading and dirt increases
Solution Approach 1:
The invention segments the photovoltaic system into independent micro-converter units, each handling a portion of the power conversion. This segmentation allows individual modules to operate independently, so shading or dirt on one module affects only that module's output rather than the entire series-connected string, maintaining overall system productivity despite partial degradation.
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 enhances the reliability and safety of photovoltaic systems by reducing the complexity of electronics and eliminating the dependency on communication systems, ensuring continuous and efficient energy production while maintaining electrical safety during all operating phases.
Implementation Method 1
Each photovoltaic module is associated with a micro-converter of the DC/DC boost type
Implementation Method 2
the said DC bus management device triggers a time delay at least equal to twice the start-up time of the inverter and, at the end of said time delay, initiates a procedure for discharging the DC bus
Data Source
Figure 1A~1B
Figure 2~3A
Figure 3B~3C
AI summary
The invention relates to a control system for photovoltaic power generation equipment comprising a plurality of photovoltaic (PV) modules each equipped with a DC/DC micro-converter (C) connected to a DC bus (BUS), a DC bus manager (MNG), and an inverter (INV) to convert the DC current from the photovoltaic panels into AC current for an electrical distribution network (R).The device according to the invention is characterized by the fact that the DC bus (BUS) management means are configured to inject energy into the DC bus (BUS) when the voltage of said DC bus is less than a minimum voltage Vm until said minimum voltage Vm is reached, at which point the energy injection is interrupted, and by the fact that each of said micro-converters (C) is configured to inject a maximum power from the photovoltaic (PV) modules into the DC bus (BUS) when the DC bus (BUS) voltage is between a first voltage Vb and a second voltage Vc and to stop the injection of power from the photovoltaic (PV) modules into the DC bus (BUS) when the DC bus voltage is less than a low threshold voltage Va or greater than a high threshold voltage Vd, with 0 < Va < Vm < Vb < Vc < Vd.