RF Inverter Load Distribution via Virtual Resistance
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Solution Overview
Problem
Existing methods for controlling voltage and power in parallel high-frequency inverters are complex, require high control effort, and are sensitive to measurement inaccuracies, leading to inefficient load distribution and response time issues.
Innovation Solution
The method simulates a virtual internal resistance for each high-frequency inverter to regulate the intermediate circuit voltage, eliminating the need for cross-current detection and using a reduction variable calculated from input power and an adjustment factor to stabilize the system and distribute load effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If transverse current detection and evaluation is implemented to regulate output voltage, then voltage control is achieved, but control complexity and control effort increase significantly
Solution Approach 1:
The patent extracts and eliminates the complex transverse current detection and evaluation mechanism from the control system. Instead of measuring and evaluating cross currents between inverters, the invention uses a simplified approach where each inverter independently regulates its own intermediate circuit voltage based on its own output current and a calculated virtual voltage drop, thereby removing the need for complex inter-inverter current detection while maintaining effective voltage control
Solution Approach 2:
Each inverter is equipped with autonomous control capability to regulate its own intermediate circuit voltage without requiring external detection of transverse currents. The control device in each inverter independently calculates the virtual voltage drop based on its own operating parameters and adjusts its output accordingly, enabling self-service control that reduces overall system complexity
2Reliability
If transverse current measurement and control is implemented, then load distribution is improved, but response time decreases due to high control effort
Solution Approach 1:
The patent implements preliminary action by pre-calculating and storing the internal resistance values of each inverter in memory before operation. During control, the system directly retrieves these pre-stored values and calculates the virtual voltage drop using the formula UVR = Pi * Ki, where Pi is the output current and Ki is the pre-stored internal resistance. This eliminates the need for real-time measurement and evaluation of transverse currents, significantly reducing control effort and improving response time while maintaining accurate load distribution
Solution Approach 2:
The invention replaces the mechanical/electrical measurement system for detecting transverse currents with a computational approach. Instead of using physical current detectors to measure cross currents between inverters, the system uses mathematical calculations based on each inverter's own output current and pre-stored resistance values to determine the appropriate control action, thereby reducing measurement complexity and improving response speed
3Reliability
If cross current detection is used to suppress transverse currents, then output stability is improved, but measurement inaccuracies directly affect control leading to falsified actual values
Solution Approach 1:
The patent extracts and eliminates the transverse current measurement环节 from the control system. By not measuring cross currents at all, the system removes the source of measurement inaccuracies that would otherwise directly affect control. Each inverter independently regulates based on its own measured output current and pre-stored resistance values, avoiding the propagation of measurement errors that occurs when transverse currents are measured and used for control
Solution Approach 2:
The invention creates a virtual model of the inverter's internal resistance characteristics through pre-stored values Ki in memory. This virtual resistance model allows the control system to calculate the virtual voltage drop UVR = Pi * Ki without needing to physically measure or infer transverse currents. The copied resistance characteristics enable accurate control while avoiding measurement inaccuracies associated with direct transverse current detection
Data Source
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AI summary
The invention relates to a method for control of the voltage and power of a plurality of RF inverters (2), which are connected in parallel at the output, of an insular inverter installation and for splitting the load between these RF inverters (2), which each comprise at least one DC/DC converter (3), an intermediate circuit (4) and a DC/AC converter (5), with a reference variable (U1') being formed for each RF inverter in order to preset a nominal value for control of an intermediate-circuit voltage (üz?i) on the intermediate circuit (4) of the RF inverter (2). In each RF inverter (2), a control apparatus (13) determines the load on each RF inverter (2) by measurement of the current required or of the power required, simulates an internal resistance of the RF inverter (2) across which a virtual voltage drop (UVR) which is dependent on the determined load is caused, which voltage drop is used to control the voltage (UZKi) of the intermediate circuit (4), such that this results in a deliberate change in the output voltage of each RF inverter (2).