Inverter Reactive Current Control via Space Vector Voltage
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Solution Overview
Problem
Existing methods for feeding reactive power into a three-phase electrical supply network are slow to respond to voltage changes, as determining positive and negative sequence voltages is a time-consuming process, leading to delayed reactive current adjustments.
Innovation Solution
The method involves using a space vector voltage calculation to quickly respond to voltage changes during fault operations, transitioning from positive sequence voltage to space vector voltage and back, with a controller managing the reactive current feed based on these voltage references to ensure rapid reactive power tracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If positive and negative sequence voltage determination is used for reactive current feed-in, then reactive power tracking is achieved, but the response speed to voltage changes is slow
Solution Approach 1:
The patent dynamically switches between two different voltage determination methods (sequence component method and space vector method) based on the operational state. During fault conditions, it uses the space vector method for rapid response, while during normal operation, it uses the sequence component method for precise reactive power tracking. This dynamic adaptation resolves the contradiction by optimizing the method selection according to real-time needs.
Solution Approach 2:
The patent changes the fundamental parameter used for voltage determination from sequence components (which require full-period measurement) to space vector (which can be calculated instantaneously). This parameter change enables the system to transition from a slow but accurate method to a fast method when needed, particularly during fault conditions where rapid response is critical.
2Measurement precision
If full-period voltage measurement is used for sequence voltage determination, then accurate reactive power control is achieved, but the reaction time to voltage changes is delayed
Solution Approach 1:
The patent calculates the space vector voltage continuously and preliminarily, ready for immediate use when faults occur. The space vector can be determined instantaneously without waiting for a full voltage period, so when a fault is detected, the system already has the necessary voltage information ready, eliminating the time delay that would otherwise occur during fault response.
Solution Approach 2:
The space vector voltage serves as an intermediary measurement that bridges the gap between the slow sequence component method and the need for rapid fault response. It provides a intermediate solution that can be calculated quickly and used to trigger the fault condition detection, which then initiates the switch to the appropriate control mode.
3Speed
If space vector voltage is used for rapid voltage change detection, then response speed is improved, but system complexity increases
Solution Approach 1:
The patent implements a dynamic control strategy that activates the space vector method only during fault conditions rather than continuously. This reduces the overall system complexity by keeping the fast response capability available but not constantly engaged, switching to the simpler sequence component method during normal operation.
Solution Approach 2:
The patent changes the operational parameter from continuous use of space vector method to conditional use based on fault detection. This parameter change (from always-on to event-driven) reduces the effective complexity of the system while maintaining the rapid response capability when needed, as the complex calculations are only performed when actually required.
Data Source
AI summary
A method for feeding electrical power into an electrical, three-phase supply network by means of an inverter device, wherein the electrical supply network has a three-phase line voltage with a first, second and third line voltage phase, comprising the steps: feeding the electrical power during normal operation if a fault-free operation has been identified for the electrical supply network, wherein during normal operation a positive sequence voltage and optionally a negative sequence voltage is recorded from the line voltage and a reactive current is specified at least depending on the positive sequence voltage and optionally depending on the negative sequence voltage, and changing to a fault operation if a voltage change in the line voltage meets a predetermined fault criterion, in particular if the voltage change exceeds a predeterminable minimum amount of change or a minimum amount of change gradient, wherein during the fault operation, at least directly after the change, the reactive current is specified depending on a space vector voltage.