Dual AC Bus Droop Control for Equal Generator Load Sharing
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Solution Overview
Problem
In electrical power systems with alternating current (AC) busses, existing technologies face challenges in efficiently sharing power demands between generator sets while managing parasitic harmonic currents and accommodating varying auxiliary loads, which can lead to unequal power sharing and increased transformer currents.
Innovation Solution
The implementation of a control system using different droop control profiles for generator sets, allowing equal frequency operation while adjusting power outputs to accommodate differing auxiliary loads, ensuring equal sharing of propulsive loads between generators, and utilizing interconnecting transformers to mitigate harmonic currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional droop control is used with identical generator sets, then system simplicity is maintained, but unequal power sharing occurs when auxiliary loads are unbalanced
Solution Approach 1:
The patent applies local quality by assigning different droop control profiles to different generator sets based on their specific auxiliary load configurations. Each generator set's controller is configured with a droop profile tailored to its local auxiliary load conditions, enabling equal power sharing of primary loads while accommodating unbalanced auxiliary loads without requiring complex system-wide coordination.
2Power
If higher-rated transformers are used to accommodate unbalanced auxiliary loads, then load capacity is increased, but system cost and size increase
Solution Approach 1:
The patent changes the operational parameters of the generator sets by implementing different droop control profiles, which allows the system to balance power distribution dynamically. This parameter change enables the use of lower-rated transformers since the unbalanced auxiliary loads are compensated through control adjustments rather than requiring increased transformer capacity.
3Stability of the object's composition
If identical droop control profiles are used for all generator sets, then control consistency is maintained, but fundamental frequency current flows through interconnecting transformers
Solution Approach 1:
The patent introduces asymmetry by deliberately using different droop control profiles for different generator sets. This asymmetric control configuration counteracts the effect of unbalanced auxiliary loads, preventing fundamental frequency currents from flowing through the interconnecting transformers while maintaining stable and consistent system operation.
4Reliability
If load sharing is implemented between generators, then system redundancy is improved, but harmonic current mitigation becomes more difficult
Solution Approach 1:
The patent uses the differently configured droop control profiles as an intermediary mechanism that enables load sharing between generators while simultaneously preventing the generation of harmful harmonic currents. The control profiles act as a mediator that coordinates power distribution to maintain system redundancy without introducing harmonic distortion issues.
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
This approach enables efficient equal sharing of propulsive loads between generators, reducing the need for higher-rated transformers and minimizing fundamental frequency current flow, thus enhancing system efficiency and redundancy while managing harmonic distortion.
Implementation Method 1
an interconnecting transformer connected between the first and second AC busses
Implementation Method 2
a controller configured to control the first generator set according to a first droop control profile and to control the second generator set according to a second droop control profile. The first and second droop control profiles relate respective output frequencies of the first and second generator sets to respective output powers
Data Source
Figure 1
Figure 2A~2B
Figure 3A~3B
AI summary
Electrical power systems and methods of controlling electrical power systems are described. One such electrical power system comprises: a first ac bus 21 and a first generator set 11, G1 configured to supply the first ac bus 21 with ac electrical power; a second ac bus 22 and a second generator set 12, G2 configured to supply the second ac bus 22 with ac electrical power; an interconnecting transformer 15 connected between the first and second ac busses 21, 22; a primary electrical load M1, M2 connected to both the first and second ac busses 21, 22 via a converter arrangement 31, 32; an auxiliary load 51 connected to the first ac bus 21; and a controller 17 configured to control the first generator set 11, G1 according to a first droop control profile and to control the second generator set 12, G2 according to a second droop control profile, the first and second droop control profiles relating respective generator operating frequencies of the first and second generator sets 11, G1; 12, G2 to respective output powers of the first and second generator sets 11, G1; 12, G2.