Modular Multilevel Converter Control Using Observer for Disturbance Compensation
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Solution Overview
Problem
Existing converter control methods face challenges in achieving high control accuracy due to disturbance effects, measurement errors, and delays, which affect the precision and stability of converter regulation.
Innovation Solution
A method that uses an observation unit to model the converter, taking into account disturbance effects and delays, by calculating actual state values based on control voltage and current measurements, and an estimator unit to determine intermediate circuit energy values, providing undisturbed and instantaneous state values for precise control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional control methods are used without disturbance compensation, then the control structure remains simple, but control accuracy deteriorates due to disturbance effects and measurement errors
Solution Approach 1:
An observation unit is introduced as an intermediary component that receives control voltage values and measured current values, processes them through a converter model, and outputs undisturbed actual status values. This mediator filters out disturbance effects and measurement errors, providing clean state information to the control unit without requiring complex disturbance modeling throughout the entire control structure
Solution Approach 2:
A mathematical model of the converter is created and implemented in the observation unit. This model copy simulates the converter's behavior and allows the system to estimate undisturbed actual status values by comparing model predictions with measured values, thereby compensating for disturbances without modifying the physical converter structure
2Measurement precision
If measurement delays are not compensated, then the control system remains simple, but control precision deteriorates due to instantaneous value inaccuracies
Solution Approach 1:
The observation unit performs preliminary processing of measured current values by combining them with control voltage values through the converter model. This preliminary action estimates the actual status values at the current time instant even when measurements are delayed, providing accurate instantaneous values to the control unit before they are needed for control decisions
3Stability of the object's composition
If disturbance effects are not considered in the model, then the model structure remains simple, but control stability deteriorates due to accumulated errors
Solution Approach 1:
The observation unit implements a feedback mechanism where the converter model continuously processes control voltage values and measured current values to generate undisturbed actual status values. This feedback loop compensates for disturbance effects and measurement errors by continuously comparing model predictions with actual measurements and adjusting estimates accordingly, ensuring control stability without requiring complex disturbance modeling in the main control path
Data Source
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AI summary
In order to provide a method for controlling a converter (1) having controllable power semiconductors, wherein actual state values x (k), which describe the state of the converter (1), are compared with target state values x target (k) in order to obtain control difference values, which are fed to a control unit (16), which produces setting voltage values u (k) at the output of the control unit, and control electronics (19) provide control signals according to the setting voltage values u (k) and transmit said control signals to the power semiconductors (S1, S2) of the converter (1), wherein the control unit (16) generates such setting voltage values u (k) that the control difference values become as small as possible, wherein said method considers interference effects, the actual state values x (k) are calculated by an observation unit (21) based on the setting voltage values u (k), wherein the observation unit (21) models the converter (1) and considers interference effects so that the actual state values x (k) correspond to undisturbed measured current values that are freed of interference effects. The method can be expanded in such a way that delay effects are also considered and possibly state intermediate-circuit energy values are also used. The invention further relates to an arrangement for carrying out the method.