Central Control Unit for Photovoltaic Inverter Load Balancing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing photovoltaic systems face challenges in meeting energy supply network requirements, such as balancing power differences between phases, remote switching of decentralized feeders, and island grid detection, which increase costs and are not effectively addressed by existing solutions like power balancers and central monitoring systems.
Innovation Solution
A photovoltaic system with a central control and monitoring unit connected between inverters and the power supply network, featuring network monitoring at the feed-in point, communication links between inverters and the control unit, and intelligent network coupling switches, allowing for centralized management of unbalanced loads and islanding detection, enabling efficient power balancing and remote switching without a central network section switch.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a power balancer with individual failure detection circuits and automatic disconnect points is used for each inverter, then unbalanced load requirements can be met, but device complexity and cost increase due to additional central switching devices and mains contactors
Solution Approach 1:
The patent merges the monitoring and control functions into a single central control unit that manages all inverters through a communication bus, eliminating the need for individual failure detection circuits and automatic disconnect points in each inverter. The central control unit receives power measurements from all inverters and coordinates switching operations, thereby reducing device complexity while maintaining unbalanced load compliance.
Solution Approach 2:
The central control unit serves multiple functions: it monitors power output from all inverters, detects unbalanced loads, controls the mains contactor switching, and communicates with the energy supply company. This multi-functional approach replaces the need for separate failure detection circuits and disconnect points in each inverter, reducing overall system complexity.
2Reliability
If a central control and monitoring device with communication bus connecting all inverters is used, then mutual interference and unnecessary shutdown can be prevented, but monitoring can only be done at central measuring point and cannot be designed as power balancer
Solution Approach 1:
The patent introduces a communication bus as an intermediary that connects all inverters to the central control unit, enabling data exchange and coordinated control. This allows the system to function as a power balancer by enabling the central control unit to receive power measurements from all inverters and coordinate their operation, while preventing mutual interference through centralized management.
Solution Approach 2:
The central control unit receives continuous power measurements from all inverters through the communication bus and uses this feedback to detect unbalanced loads and coordinate switching operations. This feedback mechanism enables the system to maintain power balance while preventing unnecessary shutdowns, combining the reliability benefits of central monitoring with the adaptability of power balancing capability.
3Reliability
If grid monitoring device switches off inverters based on voltage or frequency criteria, then grid safety can be ensured, but passive island grid monitoring is not permitted for inverters that regulate their phase currents individually
Solution Approach 1:
The patent uses active feedback-based islanding detection where the central control unit continuously receives power measurements from all inverters and compares the sum against expected values. This active detection method is compatible with inverters that regulate their phase currents individually, as it monitors the actual power output rather than relying on passive voltage or frequency changes, thereby ensuring both grid safety and inverter type compatibility.
4Ease of operation
If multiple single-phase inverters with individual disconnecting devices are used, then remote switching capability is achieved, but a central network section switch is still required
Solution Approach 1:
The patent extracts the central switching function from the individual inverter level and consolidates it at the network level with a single mains contactor controlled by the central control unit. Each inverter is equipped with individual disconnecting devices for remote switching capability, but the central network section switch is replaced by the centrally coordinated mains contactor, reducing the total number of switching devices while maintaining remote switching functionality.
Data Source
Figure 1
AI summary
A photovoltaic system (1) for three-phase feed-in into an electrical power supply network (2) with several single- or three-phase photovoltaic inverters (11-16) which can be connected to the power supply network (2) on the output side, wherein each photovoltaic inverter (11-16) has a disconnecting device (3) on the output side, and several photovoltaic generators (G) which are connected to the input side of the photovoltaic inverters (11-16), is intended to meet the requirements of an energy supply company and also be cost-effective.This is achieved by a central control and monitoring unit (4) connected between the photovoltaic inverters (11-16) and the power supply network (2), wherein the control and monitoring unit (4) has a network monitoring device at the feed-in point (7) of the network, which measures one or more network parameters, and at least one communication link (5) between the individual photovoltaic inverters (11-16) or the individual disconnecting devices (3) and the connected central control and monitoring unit (4), so that the individual photovoltaic inverters (11-16) can be disconnected from the power supply network (2) via their disconnecting devices (3) by means of a control command signal of the communication link (5).