Single-Phase Compensator Current for Non-Sinusoidal Waveforms
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Solution Overview
Problem
Existing methods for improving power factor and reducing total harmonic distortion (THD) in single-phase alternating current electrical circuits with periodic non-sinusoidal waveforms require multiple compensators, leading to instability and increased complexity.
Innovation Solution
A method for determining a compensator current waveform using a single current source connected in parallel with the load, which decomposes the source voltage and current into even and odd components, and identifies a useful and detrimental current component to eliminate, thereby reducing THD and improving power factor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If two compensators are used to improve power factor and reduce THD, then the source power factor increases and THD decreases, but the device complexity increases and stability deteriorates
Solution Approach 1:
The patent combines the functions of voltage compensation and current compensation into a single compensator device. The compensator simultaneously performs both voltage and current compensation tasks, eliminating the need for two separate compensators and reducing system complexity while maintaining the benefits of improved power factor and reduced THD
Solution Approach 2:
The compensator is designed with multi-functionality, serving both as a voltage compensator and a current compensator. This universal device can handle both voltage and current waveform distortions, making the system more compact and easier to control while achieving the desired improvement in source operating conditions
2Loss of energy
If series compensation is used to improve power factor, then the effective current value reduces, but the stability of electromechanical systems deteriorates
Solution Approach 1:
The patent introduces a parallel compensator as an intermediary element that compensates for current harmonics without directly altering the voltage structure. This approach reduces active power losses and improves power factor while avoiding the stability issues associated with series compensation, as the compensator operates in parallel and does not interfere with the fundamental voltage-stability relationship
Data Source
Figure 1~2
AI summary
The subject of the invention is a method for determining compensator current in a single-phase alternating current electrical circuit with a linear resistive-inductive load and with periodic non-sinusoidal waveforms of voltage and current, which can be written, taking into account the initial phases of voltage harmonics, in the form of Fourier series as a sum of sinusoidal functions with a dominant first harmonic. The periodic non-sinusoidal waveforms of power source voltage and current, after shifting in time such that the phase of the first harmonic of voltage equals zero, are decomposed into even and odd components. The odd component of the source current is the sum of useful current in the form of iut=∑n=1∞2Insinnωtcosφncosψn−nψ1, where: n - harmonic order, In - effective value of the n-th harmonic of current, ω - angular frequency of the fundamental harmonic, ϕn - phase shift between the n-th harmonic of voltage and current, ψn - initial phase of the n-th harmonic of voltage, wherein the terms of the useful current iu(t) add up with the first harmonic component of the source current and these terms in the form of sinusoidal waveforms are proportional to the corresponding harmonics of the odd component of the source voltage, and of orthogonal detrimental current with a value equal to idt=∑n=2∞2Insinnωtsinφnsinψn−nψ1, the terms of which do not add up with the first harmonic of the source current, and which is particularly important due to the possibility of determining the compensator current. Then, based on an analysis of instantaneous and active power of the source, using the source current in the form of a sum of the even component ipt=∑n=1∞2Incosnωtcosφnsinψn−nψ1−sinφncosψn−nψ1 and of the odd component of the source current in(t) composed of the useful current iu(t) and the detrimental current id(t), a component of the source current ik(t) is determined, which should be eliminated from the waveform of the source current by means of a known compensator (K) in the form of a current source with a value of ikt=idt+ipt=∑n=2∞2Insinnωtsinφnsinψn−nψ1+∑n=1∞2Incosnωtcosφnsinψn−nψ1−∑n=1∞2Incosnωtsinφncosψn−nψ1 connected in parallel to the load.