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The concepts of impedance matching and infinite feeder simulation are currently the mainstream solutions to the problem of background harmonic propagation and magnification on distribution feeders, and their principle is to eliminate reflected waves, which can dampen the harmonic voltage-magnifying factor to around 1. The standing wave compensation mitigation scheme proposed in this letter is based on a completely different concept, which can extend the feeder length to an integer multiple of the harmonic wavelength equivalently by constructing a virtual feeder. At this time, the reflection effect does not disappear but transfers to another state, and the maximum harmonic voltage-magnifying factor on the feeder is limited to 1. Furthermore, since the magnifying factor at most positions on the feeder is obviously lower than this limit, the proposed standing wave compensation-based active power filter (SWC-APF) can obtain significantly better mitigation performance than conventional schemes regardless of the installation location, and the required power capacity will not increase. Finally, the experimental results verify the effectiveness of the proposed scheme.

The overvoltage oscillation (ringing) in long-cable-fed motor drives is caused by the mismatch between motor surge impedance and cable characteristic impedance, which increases the insulation stress of motor winding while also exacerbating electromagnetic interference (EMI). Passive filters can effectively suppress overvoltage, but the drawbacks of high losses, large size, and additional costs limit their application in high-power scenarios. This brief proposes a quasi 2N+1 level modulation method for cascade H-bridge (CHB) inverters in medium-voltage motor drives. The suppression principle is to construct two or 2N steps with predetermined width during each PWM transition by changing the carrier phase shift angles within and between submodules of CHB inverter to make traveling waves cancel out in pairs on the cable. Theoretical derivation of motor terminal voltage s-domain expression with proposed method and detailed explanation of traveling waves counterbalanced were provided, the experimental results also proved its correctness and effectiveness.

The common high-frequency ac bus modular multilevel converter–based solid-state transformer (MMC-SST) scheme featured by synchronous modulation could realize the lightweight design of module capacitance without complicating the control strategy and circuit structure. However, in the lightweight MMC-SST system, the substantial reduction of submodule capacitance leads to the strong coupling between ac and dc ports. The study of tracking and antidisturbance performances of the lightweight MMC-SST based on the dynamic average model shows that the tracking performance difference could be compensated by the regulator, but the antidisturbance performance is weakened when the capacitance is reduced. A predictive controller is proposed for optimizing the antidisturbance performance, which could improve the response speed and then decrease dc-link voltage deviation. The feasibility of low inertia operation of the lightweight MMC-SST in a hybrid ac–dc distribution network, medium voltage dc power transmission system, and photovoltaic and energy storage joint power supply system is also evaluated; it shows that the normal operations of MMC-SST are not deteriorated by the inertia reduction both in the power router and generator modes. Finally, the effectiveness of the optimization strategy is verified by simulations and experiments.

Cascaded H-bridge-based solid-state transformer (CHB-SST) has been the typical scheme in medium- and low-voltage ac/dc conversion applications, and large-size capacitance caused by second-order ripple of submodules (SMs) is the inherent problem of CHB-based systems. In this article, we propose a novel low-capacitance CHB-SST based on zero-impedance resonant push–pull (ZRPP) decoupling channel for ripple power. ZRPP presents zero-impedance characteristic at its switching frequency equaling to series resonant frequency, which makes the equivalent parallel of CHB ac-link capacitors, and provides a decoupling channel for ripple power. Therefore, the horizontal SMs ripple power can achieve mutual cancelation based on their own three-phase symmetry, which significantly reduces the size of ac-link capacitance. In addition, the elimination of SMs ripple-voltage achieves the elimination of grid zero-sequence harmonics from root cause, and the mutual clamping of parallel ac-link capacitors also achieves the voltages self-balancing, which reduces the complex of system control. The CHB-SST configuration, operating principle, ripple-power decoupling, SMs voltage self-balancing, system design, and evaluation are discussed in this article. Finally, the effectiveness of the proposed CHB-SST is verified by simulation and experiment.

Cascaded H-bridge (CHB) converter has become an attractive topology for future large-scale photovoltaic (PV) plants in medium-voltage microgrids. However, the unequal irradiation and aging degree of PV arrays will lead to imbalanced and inconsistent output power between the three phases. This article presents a novel approach to integrating PV and energy storage (ES) systems inherent in microgrids, utilizing a hybrid CHB-based energy router (HCHB-ER), which is configured with a limited number of submodules to connect with the centralized ES. The proposed topology can handle serious interphase power imbalance and respond to grid-side power scheduling, without the appearance of overmodulation and common-mode voltage rise caused by traditional zero-sequence voltage injection methods. Under the three major constraints from the modulation level, the centralized energy storage maximum intrapower regulation boundary and submodule configuration ratio are analyzed in detail. Additionally, the power imbalance regulation capability of the proposed HCHB-ER across various configuration ratios is thoroughly evaluated and compared with the zero-sequence injection methods. Finally, the correctness and effectiveness of the proposed strategy are verified by simulations and experiments.