DC-Link Voltage Power Clipping in PV Inverters
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Solution Overview
Problem
Conventional PV systems with high array-to-inverter ratios face inefficiencies in power production due to unnecessary power clipping by DC/DC converters, which cannot dynamically adjust to maximize overall installation power output and require complex communication networks for effective power management.
Innovation Solution
The method utilizes the DC-link voltage to automatically control DC/DC converters, allowing power clipping without relying on traditional communication networks, by modifying inverter software to adjust the DC-link voltage based on power output, enabling dynamic power management and maximizing overall system efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If each DC/DC converter is provided with a pre-established maximum power setting, then power clipping is achieved in a simple way, but the maximum power production from the complete installation is not maximized and dynamic power limits are not possible
Solution Approach 1:
The inverter measures the actual power being injected to the grid and uses this feedback information to control the DC/DC converters. The measured power value is communicated back to the converters, enabling them to adjust their output dynamically based on actual system conditions rather than operating with fixed pre-established limits.
Solution Approach 2:
A communication network acts as an intermediary between the inverter and the DC/DC converters, transmitting the measured power information from the inverter to the converters. This intermediary enables coordinated control without requiring direct complex control architecture, allowing dynamic power limit adjustment while maintaining system simplicity.
2Productivity
If a communication network is used to actively clamp the power from each converter based on the power measured by the inverter, then power production is maximized, but the system becomes complex, slow in response and costly to implement
Solution Approach 1:
The communication network serves as a simple intermediary that only transmits power measurement data from the inverter to the DC/DC converters. By limiting the communication function to this single purpose, the system achieves dynamic power optimization without the complexity of bidirectional control commands or sophisticated communication protocols.
Solution Approach 2:
Each DC/DC converter autonomously adjusts its own power output based on the measured power information it receives from the inverter. The converters self-regulate their operation without requiring external control commands, eliminating the need for complex centralized control logic while maximizing total power production.
3Power
If the inverter limits power by reducing current drawn from the PV array, then power clipping is achieved, but the operation point moves away from the maximum power point
Solution Approach 1:
The power control function is segmented between the inverter and the DC/DC converters. The inverter maintains maximum power point tracking by keeping the array operation point optimal, while the DC/DC converters perform the actual power limiting at their output stage. This segmentation allows power clipping without sacrificing MPPT efficiency.
Solution Approach 2:
The power clipping function is extracted from the inverter's current control and relocated to the DC/DC converters. By separating the power limitation function from the MPPT function, the system can clip power at the converter output while the inverter continues to operate the array at the maximum power point, eliminating the efficiency loss associated with moving the operation point away from optimal conditions.
Data Source
AI summary
An improved method for controlling an electrical distribution system of the type having a plurality of electrical sources, a load, a DC link coupling the electrical sources to the load and a control means for controlling the output of at least one of the plurality of electrical sources so that the plurality of sources deliver to the load an amount of power appropriate to the load. The improvement comprises an adaptation in respect of the load that provides for the DC link voltage to vary; and an adaptation of the control means resulting in the output being controlled as a direct function of the DC link voltage.