Search Results (29)

The conventional model predictive control (MPC) experiences a tremendous number of switching state evaluations per control cycle when applied to multilevel converters, which makes it computationally impractical. To address this issue, this article proposes a computationally efficient MPC (EMPC) for the cascaded H-bridge (CHB) static synchronous compensator (STATCOM), which is enabled by the sorting of the H-bridge submodules upon their dc capacitor voltages, such that the candidate switching states are restricted to the scope in which the lower-voltage submodules are charged and the higher-voltage submodules are discharged. And therefore, the exponentially increasing switching states in the CHB-STATCOM can be dramatically reduced while the computational efficiency is greatly improved. In addition, prior to control implementation, a generic discrete-time prediction model with the incorporation of a zero-sequence component is established to merge the balanced and unbalanced scenarios into one framework, so as to address the issues related to either grid and/or load unbalances in the CHB-STATCOM for distribution grids. Both simulation and hardware-in-loop experimental studies are provided to verify the effectiveness of the EMPC strategy. Full article

The increasing penetration of inverter-based renewable energy resources, especially photovoltaic (PV) systems, has decreased the available system inertia and introduced challenges in maintaining stable grid-forming operation. This paper presents a grid-forming photovoltaic multilevel inverter (MLI) with a modified delta-connected cascaded H-bridge (CHB) multilevel configuration. The proposed system decreases the number of semiconductor switches and provides inherent voltage balancing, while also achieving high power quality, rendering it suitable for grid-forming applications. Each H-bridge cell is connected to an isolated Cúk converter to enable maximum power point tracking (MPPT) of distributed PV modules, allowing for flexible and modular DC-side integration. The proposed MLI operates as a virtual synchronous generator. A control scheme is proposed to attain grid-forming capability, hence providing stable voltage and frequency support. Moreover, a DC-link voltage regulation strategy is also developed to maintain the DC-link voltage at the reference voltage. A detailed mathematical model is developed to characterize the associated dynamics of the proposed MLI and the control system with a grid interface. The model is built in the SIMULINK environment, and the simulation results are presented under variations in solar radiation and grid voltage disturbances to exhibit the functionality of the proposed system and the effectiveness of the control scheme in providing a well-damped frequency response and stable generated voltage and currents. The results demonstrate stable frequency regulation with a settling time of approximately 0.3 s, and the output current exhibits low harmonic distortion, with a Total Harmonic Distortion (THD) of about 0.53%. Simulation results show stable operation and confirm that the proposed approach is a competitive solution for PV-based grid-forming applications. Full article

With the increasing integration of renewable energy sources into the grid, power quality at the point of common coupling (PCC)—particularly harmonic distortion introduced by power electronic converters—has become a critical concern. This paper presents a rigorous design and evaluation of a three-phase, fifteen-level cascaded H-bridge multilevel inverter (CHB MLI) with an LCL filter, selected for its superior harmonic attenuation, compact size, and cost-effectiveness compared to conventional passive filters. The proposed system employs Phase-Shifted Pulse Width Modulation (PS PWM) for balanced operation and low output distortion. A systematic, reproducible methodology is used to design the LCL filter, which is then tested across a wide range of switching frequencies (1–5 kHz) and grid impedance ratios (X/R = 2–9) in MATLAB/Simulink R2025a. Comprehensive simulations confirm that the filter effectively reduces both voltage and current total harmonic distortion (THD) to levels well below the 5% limit specified by IEEE 519, with optimal performance (0.53% current THD, 0.69% voltage THD) achieved at 3 kHz and X/R ≈ 5.6. The filter demonstrates robust performance regardless of grid conditions, making it a practical and scalable solution for modern renewable energy integration. These results, further supported by parametric validation and clear design guidelines, provide actionable insights for academic research and industrial deployment. Full article

The large-scale integration of renewable energy grid-connected converters into the grid has given rise to many broadband oscillation accidents, primarily due to impedance mismatching with the grid. Consequently, accurate measurement of both the grid-connected converter and the grid impedance is a prerequisite for system stability assessment. However, conventional impedance measurement methods are constrained by the breakdown voltage of semiconductor switches, thus rendering them unsuitable for high-voltage, high-capacity applications. This paper aims to enable impedance measurement in large-capacity, high-voltage applications by presenting a newly developed method that overcomes the voltage limitations of conventional approaches. First, a cascaded H-bridge (CHB) topology is adopted to fulfill the impedance measurement requirements in large-capacity, high-voltage renewable energy station applications. Subsequently, a quasi-proportional-resonant (PR) controlled perturbation injection strategy is proposed to achieve rapid current injection across the 10–1000 Hz frequency range. Finally, the effectiveness and accuracy of the proposed impedance measurement method in capturing harmonic impedance are demonstrated through a hardware-in-the-loop (HIL) experiment conducted on an RTDS platform. Full article

Smart transformers (STs), which are power electronic-based transformers with control and communication capabilities, facilitate managing future distribution grids with distributed generators (DGs) and battery energy storage systems (BESSs). This paper presents a current-fed quadruple active-bridge (CF-QAB) DC–DC converters-based cascaded H-bridge (CHB) ST architecture in which it is easy to coordinate the system-level power transmission and distribution. Compared with the QAB/DAB + Boost baseline, this topology achieves a reduction of approximately 20% in device count. For the core component of the proposed ST architecture, the operation principles are illustrated and the small-signal model is derived. Based on that, the control system obtained by using the individual channel design method is proposed to decouple the highly coupled LV and BESS DC ports, which significantly simplify the control system structure and design process. The experimental results are shown to validate the effectiveness of the proposed DC–DC converter and associated control system. Full article

Soft open point (SOP) offers a viable alternative to traditional tie switches for optimizing power flow distribution between connected feeders, thereby improving power quality and enhancing the reliability of distribution networks (DNs). Among existing medium-voltage (MV) SOP demonstration projects, the modular multilevel converter (MMC) back-to-back voltage source converter (BTB-VSC) is the most commonly adopted configuration. However, MMC BTB-VSC suffers from high cost and significant volume, with device requirements increasing substantially as the number of feeders grows. To address these challenges, this paper proposes a novel star-connected cascaded H-bridge (CHB) STATCOM SOP (SCS-SOP). The SCS-SOP integrates the static synchronous compensator (STATCOM) and low-voltage (LV) BTB-VSC into a single device, enabling reactive power support within feeders and active power exchange between feeders, while achieving reduced component cost and volume, simplified power decoupling control, and increasing power quality management capabilities. The topology derivation, configuration, operational principles, and control strategies of the SCS-SOP are elaborated. Finally, simulation and experimental models of a two-port 3 Mvar/300 kW SCS-SOP are developed, with results validating the theoretical analysis. Full article

When connecting a renewable energy source to a medium-voltage grid, it has to fulfil grid codes and be able to work in a medium-voltage range (>10 kV). Multilevel converters (MLCs) are recognized for their low total harmonic distortion (THD) and ability to work at high voltage compared to other converter types, making them ideal for applications connected to medium-voltage grids whilst being compliant with grid codes and voltage ratings. Cascaded H-bridge multilevel converters (CHBs-MLC) are a type of MLC topology, and they does not need any capacitors or diodes for clamping like other MLC topologies. One of the problems in these types of converters involves the double-frequency harmonics in the DC linking voltage and power, which can increase the size of the capacitors and converters. The use of line frequency transformers for isolation is another factor that increases the system’s size. This paper proposes an isolated CHBs-MLC topology that effectively overcomes double-line frequency harmonics and offers isolation. In the proposed topology, each DC source (renewable energy source) supplies a three-phase load rather than a single-phase load that is seen in conventional MLCs. This is achieved by employing a multi-winding high-frequency transformer (HFT). The primary winding consists of a winding connected to the DC sources. The secondary windings consist of three windings, each supplying one phase of the load. This configuration reduces the DC voltage link ripples, thus improving the power quality. Photovoltaic (PV) renewable energy sources are considered as the DC sources. A case study of a 1.0 MW and 13.8 kV photovoltaic (PV) system is presented, considering two scenarios: variations in solar irradiation and 25% partial panel shedding. The simulations and design results show the benefits of the proposed topology, including a seven-fold reduction in capacitor volume, a 2.7-fold reduction in transformer core volume, a 50% decrease in the current THD, and a 30% reduction in the voltage THD compared to conventional MLCs. The main challenge of the proposed topology is the use of more switches compared to conventional MLCs. However, with advancing technology, the cost is expected to decrease over time. Full article

The paper proposes an original single-phase transformerless three-level (S-PT) photovoltaic (PV) inverter in the cascade H bridge (CHB) configuration. The DC-link voltage of the inverter is created by two serial voltage sources with a voltage twice as low as the DC-link voltage. An appropriate V_CC DC-link voltage is generated by a two-phase DC-DC boost converter, fed from the string panel output at a level determined by the maximum power point tracking (MPPT) algorithm. Two symmetrical sources with V_CC/2 are formed by a divider of two series-connected capacitors of large and the same capacitance. The common mode (CM) voltage of the proposed inverter is constant, and the voltage stresses across all switches, diodes and gate drive circuits are half of the DC-link voltage. The principles of operation of the S-PT inverter, an implementation of a complete gate control system with galvanic isolation for all IGBTs, are also presented. The proposed inverter topologies have been implemented using high-speed IGBTs and simulated in PSPICE, as well as being experimentally validated. Full article

The control of medium-voltage cascaded H-bridge (CHB) converters demands precise, high-bandwidth, low-latency, and isolated measurements. Traditional analog-to-digital converters (ADCs) can facilitate multisampling methods to meet these requirements but do not provide the high-voltage galvanic isolation that may be necessary in a system operating at medium voltage. Sigma-Delta ADCs (SD-ADCs) present a promising alternative due to their superior noise rejection capabilities and direct integration with the optical fiber interface. However, the inherent latency associated with SD-ADCs, stemming from their operating principles, poses challenges when integrating them with multisampling methods. This paper analyzes the integration of multisampling techniques with SD-ADCs for medium-voltage CHB converter control. First, the impact of SD-ADC-induced delays on the control system is elucidated from the passivity perspective. Second, the practical implementation of multisampling with SD-ADCs is discussed in detail. Finally, experimental results from a 2400 Vrms medium-voltage CHB converter are presented to validate the analysis and illustrate the effectiveness of the proposed implementation. Full article

The cascaded H-bridge (CHB) inverter has become pivotal in grid-connected photovoltaic (PV) systems owing to its numerous benefits. Typically, DC–DC converters are employed to boost the input voltage in grid-connected systems to meet the grid’s higher voltage requirements, but this approach increases equipment size and cost. To enhance inverter efficiency, this paper proposes a boost-type, three-phase CHB PV grid-connected inverter. This design can raise the input voltage and satisfy grid requirements with only a few additional components. Additionally, PV environmental fluctuations can cause variations in PV power generation, leading to a power imbalance in the inverter and potentially affecting the stability of the PV system. Based on this, we consider grid voltage fluctuations induced by unbalanced power output from the inverter and propose an improved control method based on the superposition of zero-sequence components. Finally, we construct a simulation model and conduct experimental verification using the MATLAB/Simulink platform. The validation results demonstrate that this topology reduces equipment volume and effectively enhances the efficiency of PV power generation systems. Furthermore, the designed control method ensures system stability while effectively mitigating power imbalances caused by PV module and grid voltage fluctuations. Full article

This paper presents capacitor dimensioning to increase a system’s power density while the converter performance for the delta-connected cascaded H-bridge (CHB) active power filter (APF) is not impaired. After comparing aluminum electrolytic capacitors with film capacitors, this paper proposes capacitance design requirements for film capacitors. With the help of trigonometric transformation for periodic time-varying variables, including capacitor voltages and branch voltages, the capacitance design requirements can be represented as positive univariate polynomials, the coefficients of which are with regard to the capacitance value. The optimization solver SeDuMi is then applied to determine whether a capacitance value is feasible by checking the positiveness of the polynomials. This research has very appealing theoretical and practical properties: the time-domain analysis capability for periodic variables is improved, therefore, enabling a fast computation and a broad application. Both the simulations and experimental results validate the proposed strategy. Compared with the previous work, the proposed method can result in a lower capacitance value without degrading the performance, which is beneficial for a low-cost and low-volume system. Full article

The scientific literature acknowledges cascaded H-bridge (CHB) converters as a viable alternative to two-level inverters in electric vehicle (EV) powertrain applications. In the context of an electric vehicle engine connected to a DC charger, this study introduces a state of charge (SOC)-governed method for charging li-ion battery modules using a cascaded H-bridge converter. The key strength of this algorithm lies in its ability to achieve balanced charging of battery modules across all three-phase submodules while simultaneously controlling the DC charger, eliminating the need for an additional intermediate converter. Moreover, the algorithm is highly customizable, allowing adaptation to various configurations involving different numbers of submodules per phase. Simulative and experimental results are presented to demonstrate the effectiveness of the proposed charging algorithm, validating its practical application. Full article

The paper deals with a grid-connected single-phase battery charger integrated with photovoltaic generators (PVGs). The circuit topology consists of a multilevel architecture based on a Cascaded H-Bridge (CHB) rectifier. Its main task is to charge the batteries, primarily from the PVGs, by also assuring to keep their state-of-charge (SOC) balanced. Nevertheless, when the battery SOC overcomes a predefined upper limit, beyond which the charging process could be interrupted, the available PV power can no longer be transferred to the batteries. Therefore, to avoid an undesired curtailment of PV power production, this latter can be supplied to the grid by inverting the system operation. The paper shows how to achieve this result by implementing a dedicated control action based on a multi-step procedure. Numerical investigations are carried out on a 19-level CHB converter implemented in the PLECS environment to validate the feasibility and effectiveness of the proposed control technique. Full article

The multilevel back-to-back cascaded H-bridge converter (CHB-B2B) presents a significantly reduced components per level in comparison to other classical back-to-back multilevel topologies. However, this advantage cannot be fulfilled because of the several internal short circuits presented in the CHB-B2B when a conventional PWM modulation is applied. To solve this issue, a powerful math tool known as graph theory emerges as a solution for defining the converter switching matrix to be used with an appropriate control strategy, such as the model-based predictive control (MPC). Therefore, this research paper proposes a MPC with the graph theory approach applied to CHB-B2B which capable of not only eliminating the short circuit stages, but also exploring all the switching states remaining without losing the converter controllability and power quality. To demonstrate the proposed strategy applicability, the MPC with graph theory approach is tested in four different types of SST configurations, input-parallel output-parallel (IPOP), input-parallel output series (IPOS), input-series output-parallel (ISOP), and input-series output series (ISOS), attending distribution grids with different voltage and power levels. Real-time experimental results obtained in a hardware-in-the-loop (HIL) platform demonstrate the proposed strategy’s effectiveness, such as DC-link voltages regulation, multilevel voltage synthesis, and currents with reduced harmonic content. Full article

This paper presents a method for switching reduction in cascaded H-bridge converters. Given the wide applicability of this topology, it would be especially desirable to increase its efficiency with switching losses reduction techniques. Since this type of converter requires voltage balancing methods, several modulation methods consider the possibility of combining the balancing and switching reduction goals together. In this paper, a previously disclosed optimization-based balance method was modified further to consider the switching losses in its objective function. Each commutation was penalized in proportion to the phase current and the module voltage, thus avoiding commutations that would produce the most losses but tolerating low-losses commutations. The structure of the original method was maintained so that the algorithm could be applied with minimal change. The results show that it is possible to reduce the switching up to 14% without any noticeable drawback and up to 22% at the cost of a greater DC-link ripple. It is also possible to selectively reduce the effective switching frequency of only some modules, making it significantly low. This extends the adaptability of the converter, possibly allowing hybrid converters with modules of different transistor technologies. Full article