Unbalanced Output Power Research Articles

Predictive Control of Grid-Connected Modified-CHB With Reserve Batteries in Photovoltaic Application Under Asymmetric Operating Condition

The system stability and injection of maximum active power to the grid are among the most important technical issues in cascaded H-bridge (CHB) based photovoltaic (PV) systems, especially when the irradiation of PV arrays connected to CHB cells are not uniform. In other words, the unequal irradiation of PV arrays leads to the unbalanced output power of H-bridge cells, which causes overmodulation and increased grid current total harmonic distortion in the CHB inverter. Conventional control methods cannot maintain the stability of a grid-connected CHB inverter under asymmetric operating conditions. So, this article proposes a new CHB-based structure with reserve batteries and a novel modulation technique to stabilize the system in heavy mismatching conditions and avoid overmodulation. Furthermore, the number of switches and series batteries is reduced, and the number of output voltage levels is increased compared to the conventional PV-CHB system with energy storage. The validity of the proposed solution is verified by simulation in MATLAB/Simulink, and then the experimental results are presented to confirm the theoretical and simulation results.

Implementation of Solar Panel Static Mppt on Partial Shading Conditions Based on the Boost Topology Converter with Firefly Algorithm

Indonesia has a large potential for new and renewable energy, one of which is solar energy. Solar energy can be converted into electrical energy using solar panels. The output power of a photovoltaic (PV) system is primarily affected by ambient temperature, solar irradiation, and the angle of incidence of the sun. Differences in the level of solar irradiation received by PV modules can be caused by cloudy weather, trees, buildings, and other objects that can cover the surface of the solar panels. When a PV module is partially shaded, the power output of the module becomes imbalanced. Unbalanced output power can cause multiple peaks on the PV characteristic curve, reducing overall output power. To obtain global-peak, a method for maximizing solar panel output power and an algorithm are required. The method is MPPT (Maximum Power Point Tracking). The goal of this research is to determine the maximum power point of PV in the condition of a partially shaded PV module and to design a boost converter. In this study, the MPPT control method with the Firefly algorithm is used to analyze solar panel output power in partially shaded conditions in order to avoid being trapped in the local peak. At 950 W/m2 irradiation and 35°C temperature, the maximum power output generated by the MPPT system on a 200 WP solar panel with the value of 56 Ω and 100 Ω loads is 82.85 W and 82.99 W. In partial shaded conditions on the solar panel by 25% at a temperature of 35ᴼC, the maximum power output generated by MPPT is 40.98 W and 40.82 W. In partial shaded conditions on the solar panel by 50% at a temperature of 35ᴼC, the maximum power output generated by MPPT is 38.81 W and 38.95 W. Partial shading conditions affect the maximum power point gain. The maximum output power of the panel will decrease as the panel surface is partially shaded.

A novel algorithm for increased power balance in cascaded H-bridge multilevel cells in a hybrid power amplifier

This paper concerns the issue of unbalanced output power among cells in cascaded H-bridge multilevel (CHBM) converters with conventional staircase modulation techniques under low modulation signals. This is a common condition in high-voltage/frequency hybrid power amplifiers (HPAs) consisting of a CHBM converter in series with a linear power amplifier (LPA). The online implementation of a modulation technique called split-voltage first-in first-out (SV-FIFO) that mitigates this issue is presented in this study. Differently from conventional techniques, it needs to take into consideration the magnitude and frequency of the reference voltage to generate the gating signals of the CHBM converter. This paper also introduces a design procedure for a series-type HPA and a means for generating online the gating signals of the CHBM converter, with SV-FIFO, and the reference signal for the LPA in closed loop with a mixed signal controller. Experimental results for a series-type HPA with a six-cell CHBM converter and a commercial LPA are provided to validate the design procedure of the HPA and demonstrate the enhanced (active) power balance of SV-FIFO and the effectiveness of the proposed control scheme for the HPA under transient and steady-state conditions.

Harmonic Compensation Strategy for Single-Phase Cascaded H-Bridge PV Inverter Under Unbalanced Power Conditions

Cascaded H-bridge (CHB) inverter has the advantages of easy modularization, the low harmonic content of output current, and that all power units are capable of achieving independent maximum power point tracking (MPPT). However, aging or partial shielding of photovoltaic (PV) panels will lead to the unbalanced output power of each PV module, which will result in the overmodulation of H-bridges and increased harmonic components of the grid current. In this article, a novel harmonic compensation strategy for single-phase CHB inverter is proposed, it can extend the linear modulation range of single-phase CHB inverters to about 1.27. Moreover, this strategy will not reduce energy harvesting, and also can maintain the system to operate in the unit power factor. Simulation and experimental results all verify the effectiveness of the proposed strategy.

Research on Power Equalization of Three-Phase Cascaded H-Bridge Photovoltaic Inverter Based on the Combination of Hybrid Modulation Strategy and Zero-Sequence Injection Methods

Due to the nonuniform solar irradiance, unequal ambient temperatures, or inconsistent degradation of photovoltaic (PV) modules in three-phase cascaded H-bridge (CHB) PV inverter, the unbalanced output power among PV modules will lead to the imbalanced power between phases and bridges, resulting in unbalanced or even distorted grid current between three phases, which cannot meet the requirements of grid codes. Concerning this issue, this article proposes a novel power equalization method based on the combination of hybrid modulation strategy and zero-sequence injection methods, which deals with interbridge power imbalance by hybrid modulation and interphase power imbalance by zero-sequence injection methods. By utilizing the proposed method, three-phase-balanced grid currents with low total harmonic distortion are able to be achieved even when the interbridge and the interphase power are seriously unbalanced. In addition, each H-bridge cell in three-phase CHB inverter uses square-wave modulation, which maximizes the dc-side voltage utilization of each H-bridge cell, thus extending its power balance region. Experimental results achieved by a laboratory prototype of a three-phase seven-level CHB inverter demonstrate both feasibility and validity of the proposed method.

Research on Power-Balance Control Strategy of CHB Multilevel Inverter Based on TPWM

Against to the problems of low utilization rate of DC-side voltage of Cascaded H-bridge (CHB) multi-level inverter Carrier Disposition (CD) modulation strategy and unbalanced output power of each cascaded H-bridge units, a power balanced based In-Phase Disposition Trapezoidal Pulse Width Modulation (IPD-TPWM) strategy is proposed in this article. By selecting an appropriate trapezoidal wave triangulation rate $\delta $ , the modulation strategy can greatly increase the amplitude of the CHB inverter output voltage fundamental wave while ensuring the waveform quality of output phase voltage, and realize the power-balance of H-bridge units within a full modulation ratio range by changing the arrangement of triangular carriers in the vertical direction while using the carrier segment in the half carrier period of the IPD-TPWM strategy as the basic unit. Therefore, it has solved the problem of low utilization rate of DC-side voltage and unbalanced output power of each unit. At the same time, the Total Harmonic Distortion (THD) of output line voltage of the modulation strategy is lower than that of IPD-SPWM strategy in the whole modulation degree, which effectively improves the quality waveform of the output line voltage, and can be conveniently used in N-level CHB inverters. Moreover, the working stress of all the unit switching tubes is the same, the heat dissipation distribution is uniform, the switching loss is effectively reduced, and the service life and system reliability are improved. Finally, the Matlab/Simulink simulation model and experimental platform are established to verify the validity and practicality of the modulation strategy.

An Optimized Third Harmonic Compensation Strategy for Single-Phase Cascaded H-Bridge Photovoltaic Inverter

Due to the unequal solar radiations or dust accumulation of photovoltaic modules in a single-phase cascaded H-bridge photovoltaic inverter, the unbalanced output power among photovoltaic modules will make the H-bridges with higher power overmodulation, resulting in deteriorated grid current. Concerning this issue, this paper proposes an optimized third harmonic compensation strategy that injects moderate amount of third harmonic into the overmodulation H-bridges to keep the amplitudes of their modulation waveforms just being unity, then compensates the same amount of opposite harmonic sequence and properly distributes it to rest of the H-bridges. The proposed method can ensure that all the power units will be free from overmodulation under some heavy power imbalance conditions and will not increase the third harmonic component of the grid current. The validity and effectiveness of the proposed method is verified by simulation and experimental results.

Study on microwave coherent power combining based on 20-kW S-band CW power-adjustable magnetrons

In order to meet the requirements of large-power capacity in microwave-energy industry, the microwave coherent power combining by multiple magnetrons is a valid method to gain a large-power and high efficiency microwave source. In microwave energy applications, microwave absorption of industrial materials is varying in the heating duration and dependent on the dynamic change of materials. It is the first time that a 20-kW continuously power-adjustable injection-locked magnetron source has been achieved, and according to the experiment results, the maximum microwave coherent power combining output reaches 33.1 kW, and the coherent power combining efficiency is higher than 93%. The experiments show that the unbalanced output power between the two magnetrons does not affect greatly on the microwave coherent power combining efficiency. It is a great progress to develop the microwave power source which satisfies the power capacity requirement of microwave energy industry with the real-time power adjustment for the microwave industrial applications.

Concurrent Dual-Band Digital Predistortion With a Single Feedback Loop

This paper proposes a compact and low-cost architecture with only a single feedback loop to implement concurrent dual-band digital predistortion (DPD) of power amplifiers (PAs). This technique is based on a new approach, down-converted carrier co-location $({\rm DC}^{3})$ , in conjunction with a 2-D carrier co-located memory polynomial model in PA forward modeling. The concurrent dual-band DPD models for each band can then be extracted successfully according to the forward modeling results. Experimental tests have been performed for a commercial Mini Circuits amplifier and a 120-W peak power GaN base-station PA. Different signal combinations have been tested for both balanced and unbalanced output power operations in the dual bands. The results validate that the proposed method is able to achieve linearization performances comparable to those of the conventional two parallel feedback loops based technique. Even when a nonideal feedback loop with nonflat frequency responses in the two bands is used, the new method performs well when the feedback loop is calibrated in advance. This single feedback loop based concurrent dual-band DPD architecture is a strong candidate for future broadband dual-band transmitting systems.