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Dip coating was employed to apply low temperature co-firing ceramic (LTCC) zinc molybdate coatings to the surfaces of Ni-coated Cu conductor wires. Zinc molybdate ceramic powders were synthesized via a solid state route; ceramic suspensions for dip coating were prepared by mixing the LTCC powders in an organic solution. By optimizing the dip coating parameters and subsequent heat treatment, ceramic films, with a typical insulation thickness of 47.3 μm and dielectric strength of 24.2 kV•mm -1 , were formed on the surfaces of Ni test discs. The processing parameters were transferrable to the coating of Ni-coated Cu wires; the resulting wires exhibited an insulation thickness of 40.3 μm and breakdown voltage of 798 V.

Summary Classic control methods commonly used for a unified power quality conditioner (UPQC) include the following: proportional integral (PI) control, proportional resonance (PR) control, and repetitive control. Generally, the main weaknesses of these control methods are poor compensation accuracy and low response speed. In this article, in order to enhance the overall performance of the system, we introduce an innovative nonlinear control strategy based on the Lyapunov function for the three‐phase three‐wire neutral‐point clamp (NPC) type three‐level UPQC. We first develop the mathematical UPQC model, then obtain from the model the control law which we use to construct the switching function by creating the Lyapunov function, thus avoiding the introduction of closed‐loop feedback. The suggested strategy also achieves system stability and dynamic performance by selecting appropriate parameters, after which a carrier‐based pulse width modulation control method based on the injected zero‐sequence component is applied to maintain the stability and balance of the DC‐side capacitor voltage. In addition, both numerical simulation and comparison of experimental results using traditional PI control, passivity‐based control methods, and sliding mode control shows that the proposed nonlinear control strategy for three‐phase three‐wire NPC type three‐level UPQC has an excellent response speed and compensation efficiency.

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