Inverter Control via Neutral Potential Calculation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Inverters without a connection to the neutral conductor of a three-phase voltage network face challenges in determining phase conductor voltages relative to the neutral potential, as direct measurement is unsafe due to electrical safety concerns and existing methods are inefficient.
Innovation Solution
A microcontroller-based system that detects and calculates phase conductor voltages against the neutral potential by using an internal reference potential and measuring voltage values, allowing for the determination of phase conductor voltages relative to the neutral conductor without a direct connection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the inverter operates without a connection to the neutral conductor, then the voltage load on power semiconductors is reduced and efficiency increases, but the inverter cannot directly measure phase conductor voltages against neutral potential
Solution Approach 1:
The patent introduces an intermediary calculation method that uses the measured voltages of the two capacitors (C1 and C2) and the known DC link voltage to derive the phase conductor voltages against neutral potential. Instead of directly measuring against neutral, the system uses these intermediary voltage measurements and mathematical relationships to obtain the required phase voltages, thus resolving the measurement difficulty while maintaining the neutral-free operation that improves efficiency
2Difficulty of detecting and measuring
If a direct connection to the neutral conductor is made for voltage measurement, then phase conductor voltages can be directly measured, but electrical safety is compromised
Solution Approach 1:
The patent uses intermediary voltage measurements across capacitors C1 and C2 as mediators to indirectly obtain phase conductor voltages. By measuring voltages at these intermediate points and using mathematical relationships (u_L1 = u_C1 - u_C2, u_L2 = -u_C2, u_L3 = u_C2 - u_C1), the system achieves accurate phase voltage measurement without requiring direct connection to the neutral conductor, thus maintaining electrical safety while solving the measurement problem
3Strength
If the inverter uses a lower intermediate circuit voltage, then the voltage load on power semiconductors is reduced, but the control complexity increases due to need for voltage calculations
Solution Approach 1:
The patent implements a feedback control system where the microcontroller continuously measures the capacitor voltages u_C1 and u_C2, calculates the phase conductor voltages using the established relationships, and uses this information for optimal inverter control. This feedback mechanism enables the system to operate efficiently at lower voltage levels while maintaining precise control through real-time voltage information derived from the capacitor measurements
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
Enables accurate and efficient determination of phase conductor voltages relative to the neutral potential, ensuring optimal inverter control and operation without compromising electrical safety.
Implementation Method 1
the microcontroller detects the voltage at the connection point of the capacitors against the internal reference potential by measuring the voltage
Data Source
Figure 1
Figure 2
Figure 3a~4
AI summary
The inverter (WR) has a direct current (DC) input for a DC power source (DC), and a three-phase bridge circuit with output phase conductors (P1-P3) connected with a three-phase alternating voltage system (WN). Capacitors (CX1-CX3) connected with the phase conductors comprise a common junction (VK). A microcontroller (MC) detects and computes voltages (uL1-WR-uL3-WR) of the phase conductors against an internal reference potential (BZ) and potential of a neutral conductor at the junction of the capacitors by stress measurement or from the detected voltages.