Neutral point clamped inverter for enhanced grid connected pv system performance based on hexagonal space vector modulation

ABSTRACT The increasing global demand for renewable energy has accelerated the adoption of grid-connected photovoltaic (PV) systems. However, conventional PV inverters often rely on

transformers, which add to the system’s cost, size, and power losses. Transformerless inverter topologies have emerged as a promising alternative, offering improved efficiency, compact

design, and lower costs. Despite these advantages, challenges such as high total harmonic distortion (THD), common mode voltage (CMV) issues, and neutral current imbalance must be addressed

to ensure reliable grid integration. This research investigates a transformerless five-level neutral point clamped (NPC) inverter for grid-connected PV applications, aiming to overcome these

challenges. The study focuses on analysing THD, mitigating CMV to enhance system reliability, and optimizing output voltage levels to meet grid standards. The proposed transformerless

five-level NPC inverter, incorporating a coupled inductor, is controlled using Hexagonal Space Vector Modulation (HSVM) to improve performance. Additionally, the research evaluates neutral

current behavior to ensure stability and compliance with grid codes. Simulation and experimental results validate the proposed system’s effectiveness under varying operating conditions,

highlighting its potential as a high-efficiency, cost-effective solution for sustainable energy integration into the grid. SIMILAR CONTENT BEING VIEWED BY OTHERS A NEW H6 NEUTRAL POINT

CLAMPED TRANSFORMERLESS PHOTO VOLTAIC INVERTER Article Open access 26 March 2025 IMPLEMENTATION OF ADAPTIVE HYSTERESIS CURRENT CONTROLLER IN GRID TIED MULTILEVEL CONVERTER WITH BATTERY

STORAGE SYSTEM Article Open access 23 May 2025 LOW COST AND COMPACT SIX SWITCH SEVEN LEVEL GRID TIED TRANSFORMERLESS PV INVERTER Article Open access 14 March 2025 INTRODUCTION Photovoltaic

(PV) systems have emerged as a reliable and sustainable energy source, addressing the growing global demand for clean electricity1. With advancements in PV technology, grid-connected PV

systems are now widely deployed in residential, commercial, and industrial applications2. Efficient inverters are necessary for PV system integration with the power grid to transform the DC

output from PV panels into AC voltage that is compatible with the grid3. Transformerless inverters are becoming more and more popular among different inverter topologies because of their

lower cost, weight, and size as well as their higher overall efficiency4,5,6. In a grid-connected PV system, the inverter plays a critical role in ensuring high energy conversion efficiency

while meeting stringent grid standards for power quality and safety7. In this context, the five-level Neutral Point Clamped (NPC) inverter is a desirable architecture because it provides low

switching loss, lower THD, and greater voltage levels than conventional two-level or three-level inverters. Moreover, the transformerless configuration eliminates the bulky transformer,

further improving efficiency and cost-effectiveness, while requiring careful management of leakage currents and common-mode voltage to ensure safety and reliability8. Its importance can be

highlighted as follows: most electrical grids and household appliances operate on AC. The inverter ensures that the DC output from PV panels is efficiently transformed into usable AC power.

For grid-connected systems, the inverter synchronizes the output voltage, frequency, and phase with the grid, ensuring seamless integration. Modern inverters minimize Total Harmonic

Distortion (THD) and provide high-quality AC output, improving system efficiency and reliability9. Advanced inverters optimize the power extraction from PV panels by continuously adjusting

to the panels’ maximum power point under varying conditions10,11,12. Multilevel inverters (MLIs) are an essential advancement in power electronics, particularly for applications involving

renewable energy integration, industrial drives, and high-voltage systems. Their unique ability to synthesize high-quality voltage waveforms with multiple voltage levels offers several

advantages over conventional two-level inverters13,14,15. The importance of multilevel inverters includes: MLIs produce output waveforms that closely approximate sinusoidal AC, significantly

reducing THD. This improves power quality, minimizing the need for large filter components and reducing electromagnetic interference16. By operating at lower voltage steps, MLIs minimize

switching losses compared to two-level inverters, leading to higher overall system efficiency. MLIs can handle higher voltage levels without requiring high-voltage-rated semiconductor

devices17. This makes them appropriate for high-power usages like grid-tied renewable energy systems, industrial motor drives, and electric vehicles. The stepped output waveform of MLIs

reduces voltage stress on power electronic devices, increasing their lifespan and reliability. Multilevel inverters can be configured in numerous topologies, such as NPC method, CHB method,

and Flying Capacitor. This modularity allows designers to choose the most suitable configuration for specific applications. The smoother voltage transitions in MLIs help in reducing

electromagnetic interference, enhancing the electromagnetic compatibility of the system18. MLIs are ideal for interfacing renewable energy sources like solar PV and wind turbines with the

grid due to their ability to handle variable DC input and produce high-quality AC output. MLIs facilitate better synchronization with the grid by providing high-quality output voltage,

meeting stringent grid codes for harmonic limits and power factor19. Since they establish the switching states of power semiconductor devices to construct the required output voltage and

current, pulse width modulation (PWM) techniques are crucial for regulating inverters20. Several PWM techniques have been created for multilevel inverters to enhance performance indicators

such power quality, efficiency, and total harmonic distortion (THD). SPWM has a limited modulation index and increased switching losses at low frequencies because it generates switching

signals by comparing a sinusoidal reference signal with one or more triangular carrier waves21. LSPWM is a specific form of SPWM used in multilevel inverters, where multiple triangular

carrier waves are shifted in levels corresponding to the number of voltage steps, here demerit is imbalanced capacitor voltages in certain topologies22. In Phase-Shifted PWM, the triangular

carriers for each leg are phase-shifted relative to each other; implementation is complex in higher-level inverters23. In Selective Harmonic Elimination, calculating specific switching

angles to eliminate selected harmonic components24-25. By synthesizing the reference voltage vector from the inverter’s discrete switching states, the conventional SVM employs the idea of

space vectors to control the inverter. It has several advantages, including a higher modulation index, better DC-link voltage utilization, and a lower THD. This article deals with

investigation of Hexagonal SVM Transformerless five-level NPCI for grid connected PV system, which provides reduced THD of the output waveform, mitigating Common Mode Voltage (CMV) to

enhance reliability, and optimizing output voltage levels to meet grid standards. Various PWM methods are utilized in multilevel inverters, each with its unique benefits and trade-offs.

Among these, Space Vector Modulation (SVM) stands out as a versatile and efficient technique, offering superior DC-link voltage utilization, low THD, and reduced switching losses. Its

advantages make SVM particularly suitable for transformerless five-level Neutral Point Clamped (NPC) inverters, ensuring high-performance and reliable operation in grid-connected PV systems.

The Schematic diagram of proposed research work is shown in Fig. 1. PV SYSTEM AND MPPT Using solar panels to transfers sunlight into direct current (DC) electricity, a photovoltaic (PV)

system uses the sun’s energy to establish electricity26. Multiple solar cells composed of semiconductor materials, such as silicon, that display the photovoltaic effect make up each panel.

The cells produce an electric current in response to the incident solar irradiation when they are exposed to sunlight. PV systems are modular, scalable, and environmentally friendly, making

them a key component of renewable energy solutions. They can be deployed in standalone configurations for off-grid applications or integrated with the electrical grid to support large-scale

power generation. A PV system’s performance is influenced by a number of variables, such as temperature, shading, solar irradiation, and the electrical load that is connected to the system.

For optimal energy generation, PV systems are typically paired with power electronics such as DC-DC converters and inverters to regulate voltage, current, and power output. In grid-connected

systems, the inverter plays a crucial role in synchronizing the PV-generated power with the grid. Accurate modelling of PV systems is essential to predict their behaviour under varying

environmental conditions and to design efficient power management strategies. The equivalent PV system and I-V characteristics of PV panel is shown in Fig. 2. Based on fuzzy logic An

intelligent and flexible method called Maximum Power Point Tracking (MPPT) is intended to maximize a photovoltaic system’s power output in the face of changing climatic conditions.

$$\:\text{I}={\text{I}}_{\text{s}\text{c}}-{\text{I}}_{\text{d}}$$ (1) $$\:{\text{I}}_{\text{d}}={\text{I}}_{0}({\text{e}}^{\text{q}{\text{v}}_{\text{d}}/\text{k}\text{T}}-1)$$ (2) Fuzzy

logic MPPT does not necessitate a comprehensive mathematical model of the PV array, in contrast to standard MPPT procedures like Perturb and Observe (P&O) or Incremental Conductance.

Instead, it makes judgments based on the relationship between input variables, including the change in voltage (ΔV) and power (ΔP), using a rule-based system. The algorithm makes sure that

the PV system runs at its maximum power point even in the face of rapidly fluctuating temperature or irradiance by continuously modifying the duty cycle of the DC-DC converter. Fuzzy logic

MPPT’s resilience and capacity to manage the nonlinear properties of PV systems are two of its many noteworthy benefits. It can swiftly and oscillation-free converge to the maximum power

point in situations including partial shading. The fuzzy logic controller consists of three stages: fuzzification, where input variables are converted into fuzzy sets; inference, where

decision rules are applied; and defuzzification, where the output is converted into a crisp control signal. This method is ideal for contemporary renewable energy applications since it not

only increases the PV system’s efficiency but also guarantees steady and dependable operation. Figure 3 displays the photovoltaic cell’s P-V characteristics curve and the tracking of an

MPP-based fuzzy system under various irradiance levels. To track the maximum power from the PV system, fuzzy MPPT control is used. Figure 4 displays the surface view of fuzzy rules along

with the error membership function, duty cycle membership function, and error rete membership function. TRANSFORMERLESS FIVE-LEVEL NEUTRAL POINT CLAMPED INVERTER A transformerless five-level

NPCI (Fig. 5) is a highly efficient and compact power conversion system widely used in renewable energy applications, especially grid-connected photovoltaic (PV) systems. Unlike traditional

transformer-based inverters, transformerless designs eliminate the bulky transformer, resulting in reduced cost, size, and weight. The five-level NPC inverter further enhances power quality

by synthesizing output voltages with five discrete levels, which closely approximate a sinusoidal waveform. This significantly reduces THD, minimizes the need for large output filters, and

improves overall efficiency. Its ability to produce high-quality voltage and current waveforms makes it ideal for complying with grid standards and ensuring compatibility with sensitive

electrical equipment. The transformerless design introduces challenges, such as common-mode voltage and leakage currents, which can compromise system performance and safety. However, the

five-level NPC topology addresses these issues by employing innovative modulation techniques, such as Space Vector Modulation (SVM), to minimize common-mode voltage and reduce leakage

currents effectively. Additionally, the five-level NPC inverter offers benefits like lower switching losses, balanced voltage stress across components, and modularity for scalability in

high-power applications. These advantages make it a preferred choice for modern PV systems aiming to achieve high efficiency, compactness, and grid compliance without compromising safety and

performance. The use of coupled inductors instead of transformers in inverter-fed grid-connected systems offers several advantages. Coupled inductors eliminate leakage currents caused by

parasitic capacitance, which is common in transformers, thereby enhancing system performance. They are smaller, lighter, and more cost-effective, making the overall system compact and

economical. With lower core losses and no magnetizing current, coupled inductors improve efficiency and reliability by reducing the risk of failure and avoiding issues like DC magnetization

and saturation that transformers often face. Additionally, their simpler design reduces circuit complexity and component count. Coupled inductors provide better filtering characteristics,

leading to improved power quality and reduced harmonic distortion, while also lowering electromagnetic interference (EMI). Furthermore, they are easier to scale for various voltage levels

and power ratings, making them more flexible for modern renewable energy applications. These benefits make coupled inductors a superior choice over transformers in grid-connected inverter

systems. The transformerless five-level NPCI with a coupled inductor, as shown in Fig. 6, is designed to eliminate the need for a transformer, thereby reducing system complexity and

addressing leakage current issues associated with transformers. Each leg of the inverter consists of 8 IGBT power switches, 6 clamping diodes, and 2 coupled inductors. The coupled inductors

play a crucial role in maintaining voltage stability without the use of a transformer. The DC power source is divided across four capacitors (C1, C2, C3, C4) to produce multiple voltage

levels. To produce different output voltage levels, the inverter has 125 switching modes in total. Among these, Fig. 6 depicts three ways of operation. The output voltage is + Vdc/2 in Fig. 

6a, where switches Sa1, Sa2, Sa3, and Sa4 are turned on and capacitors C1 and C2 are energized. The output voltage is − Vdc/2 in Fig. 6b, where switches Sa5, Sa6, Sa7, and Sa8 are turned on

and capacitors C3 and C4 are activated. The output voltage is + Vdc/4 in Fig. 6c, where switches Sa2, Sa3, and Sa4 are turned on and capacitor C1 is activated. The suggested inverter can

efficiently reach the required voltage levels under a variety of switching configurations. The 3-phase, five-level NPCI’s switching modes and voltage level are displayed in Table 1. Here

@-switches ON. HEXAGONAL SPACE VECTOR MODULATION Hexagonal SVM is an advanced control technique used for transformerless five-level NPCI, offering high-quality output waveforms, enhanced

efficiency, and improved DC bus voltage utilization. In this approach, the inverter’s voltage vectors are represented in a hexagonal coordinate system, where the 125 switching states of the

five-level NPC inverter form a multi-level hexagonal structure. The hexagon is divided into six main sectors, each containing subregions that correspond to specific switching combinations,

which is represented in Fig. 7. HSVM determines the reference voltage vector within this hexagonal space and decomposes it into nearby vectors for smooth transitions and minimal voltage

ripple. Capacitor voltage unbalance is one of the major drawback of a NPCI. Generally during the ideal condition, the voltage across the capacitors is equal. In non-ideal condition the

voltage across the capacitors is not equal. The causes for capacitor voltage unbalance is due to the non-uniform in the switching of the power device, dc link capacitors are in non-ideal

condition, unequal commutation of semiconductor devices, asymmetrical phase currents in switching states and injection of third harmonic current in the neutral point. Due to the above

reasons the capacitor voltage imbalance occurs in NPCI. The effects of capacitor voltage unbalance are leads to affects performance of inverter, increase voltage stress increase across the

switch, additional harmonic content in the inverter output voltage and increase in load current magnitude, which leads to increase bearing current and will damage motor bearing of the ac

drives. The modulation technique optimizes switching sequences to reduce power losses and maintain capacitor voltage balance among C1,C2,C3, and C4, which is critical for stable operation in

transformerless systems. By ensuring a continuous common-mode voltage profile, HSVM also minimizes high-frequency leakage currents, a key challenge in transformerless configurations. The

implementation involves calculating the reference vector based on the desired output voltage and phase angle, identifying the sector and subregion, selecting appropriate switching vectors,

and allocating time durations for each vector. This enables precise generation of the output waveform while maintaining system efficiency and reliability. HSVM’s ability to reduce switching

losses, improve harmonic performance, and balance capacitor voltages makes it ideal for applications such as grid-connected renewable energy systems, electric vehicle chargers, and

high-performance motor drives, where it ensures optimal performance and minimal leakage currents. There are 125 different switching modes in a three-phase, five-level NPC inverter, with each

leg having five different switching states: +Vdc/2, +Vdc/4, 0, −Vdc/4, and − Vdc/2. These consist of 30 medium and big vectors, 60 small vectors, and 5 null (or zero) vectors. Only small

vectors exhibit duplicate switching states in the Hexagonal SVM approach, which represents all switching vectors within a hexagonal region. Each of the six sectors that make up the hexagonal

region has four triangular subregions. Figure 8 illustrates the Nearest Switching Vector (NSV) technique, which is used to choose the switching vectors to efficiently balance the capacitor

voltages. This approach prioritizes the use of medium and large vectors, minimizing fluctuations at the neutral point and ensuring stable inverter operation. The control strategy employs six

sectors, with each sector further divided into sixteen triangles. To achieve voltage balance across the capacitor, NSV technique utilizes various switching state voltage vectors. Neutral

point fluctuations are minimized by using large and medium state vectors. The reference vectors are chosen to control the system’s output current and increase the output voltage. The

following is the mathematical expression for these vectors: $$\:{\:\:V}^{*}{\delta\:}_{S1}+{V}^{*}{\delta\:}_{S2}+{V}^{*}{\delta\:}_{M1}={V}^{*\:\:\:}$$ (3)

$$\:{\delta\:}_{S1}+{\delta\:}_{S2}+{\delta\:}_{M1}=1$$ (4) where δS1, δS2, and δM1 are the SV1, SV2, and MV of different triangles located in the hexagonal margin, and V* is the reference

vector. The following steps are involved in the process for identifying the reference vector: * 1. Identifying the position of the various sector. * 2. Locating the specific triangle within

the sector. * 3. Generating the gating pulses. The gating time for the NPCI is computed using the equation: $$T=T_{M1}\:+\:T_{M3}\:+\:T_{M4}$$ (5) In relation to M1, M3 and M4’s positions

vary by 1.0 and 0.5 h, respectively. When we enter these magnitude values into the equation above, so obtain, $$\:V_{dx}T\:=\:T_{M3}\:+\:0.5T_{M4}\:$$ (6) $$\:V_{qx}T\:=\:T_{M4}h$$ (7)

$$\:T_{M4}\:=\:V_{qx}T\:/h$$ (8) $$T_{M3} = \:T(V_{dx} - 0.5V_{qx}/h)$$ (9) $$\:and\:T_{M1}=T\:-\:(T_{M4}\:+\:T_{M3})$$ (10) The same Eq. (6) through (10), can be used to determine the

gating time for the other triangles. The 3-phase, five-level NPCI’s switching pulses are produced based on the switching time. POWER LOSS AND EFFICIENCY CALCULATION The average conduction

loss of the power switch and diode is calculated as, $$\:{P}_{CS}={u}_{CS}{I}_{Cav}+{r}_{C}{I}_{Srms}$$ (11) $$\:{P}_{CD}={u}_{CD}{I}_{Dav}+{r}_{D}{I}_{Drms}$$ (12) Here PCS and PCD are

average conduction loss of switch and diode; ICav & IDav are average Switch and Diode currents; ISrms & IDrms are rms current of switch and diode; UCD, UCS, rC & rD are the

voltage and internal resistance of switch and diode, which is taken from the datasheets. The Efficiency of the 3-level NPC inverter is, The energy loss during ON period of the switch is

obtained by,

$$\:{S}_{E\left(ON\right)}=\left(\frac{{E}_{ON\:}{R}_{G}}{{E}_{ON}\left({{R}_{G}}_{datasheet}\right)}\:\frac{{V}_{DC\left(ON\right)}}{{V}_{D{C}_{datasheet}}}\:\frac{{T}_{j}}{{T}_{{j}_{datasheet}}}\right){I}_{cON}$$

(13) Here, EON is energy loss during ON period of the switch; RG gate resistance of the switch; IcON is current through switch during ON period; VDC(ON) is applied dc input voltage of

inverter; Tj is junction temperature of the switch. The total switching loss of the NPC inverter is, $$\:{T}_{SL}=\left({S}_{E\left(ON\right)}+{S}_{E\left(OFF\right)}\right){f}_{T}$$ (14)

Where SE(ON) & SE(OFF) are energy loss during ON & OFF period of the power switch; fT is fundamental frequency. The efficiency of the NPC inverter is attained by,

$$\:{\upeta\:}=\frac{{P}_{out}}{{P}_{out}+{\sum\:P}_{losses}}$$ (15) Basen on the equations the power losses and efficiency of the 3-level NPC inverter of the proposed system is obtained.

SIMULATION RESULTS AND DISCUSSION The simulation of a Hexagonal SVM strategy for a transformerless five-level NPCI integrated into a grid-connected PV system was carried out using

MATLAB/Simulink. The results demonstrate improved output voltage waveforms with reduced Total Harmonic Distortion (THD), ensuring compliance with grid standards. The hexagonal SVM

effectively balanced the capacitor voltage while minimizing neutral point fluctuations, leading to stable operation under varying solar irradiance and load conditions. Efficient power

transmission and unity power factor were confirmed by the inverter’s output voltage and current being synchronized with the grid. Furthermore, switching losses and component thermal stress

were significantly reduced by the switching technique. The resilience of the control technique was confirmed by the system’s performance under dynamic situations, establishing it as a

dependable option for grid-connected PV applications. Figure 9 displays the PV system’s output voltage and current. In Fig. 10, the suggested system’s rectified output voltage is displayed.

Figure 11a and b depict the dynamic operating temperature and the comparison of the optimal DC power obtained with various MPPT controllers. The fuzzy logic-based MPPT controller offers

superior tracking when compared to other traditional MPPT tracking techniques. Figure 12 illustrates the common mode voltage mitigation for the suggested transformerless five-level NPCI with

connected inductor. This is proof that the suggested hexagonal SVM offers superior CMV mitigation when compared to other traditional PWM control strategies. Figure 12a illustrates CMV

mitigation using the SPWM method with a voltage of 248 V, which is Vdc/2 times of applied dc input voltage; Fig. 12b illustrates CMV mitigation using the hysteresis control method with a

voltage of 168 V, which is Vdc/3 times of applied dc input voltage; and Fig. 12c illustrates CMV mitigation using the hexagonal SVM method with a voltage of 84 V, which is Vdc/6 times of

applied dc input voltage. displays the transformerless five-level NPCI output voltage, which is 499.6 V. Figure 14 displays the system’s THD analysis; Fig. 14a shows the THD for output

voltage, which is 0.42%, and Fig. 14b shows the THD for output current, which is 3.63%. Figure 15 illustrates the capacitor voltage balancing spanning C1 to C4, where the capacitors’

imbalance is decreased to 1.2%. Figure 16 displays the output voltage of a transformerless five-level NPCI with a linked inductor, which does away with the need for a transformer and other

synchronization devices. Figure 17 illustrates how hexagonal SVM is used to generate switching pulses for transformerless five-level NPC inverters. EXPERIMENTAL RESULTS AND DISCUSSION The

experimental validation of the Transformerless five-Level NPCI employing Hexagonal SVM was conducted using a test bench comprising 16 A IGBT power switches and an FPGA Spartan 6 controller.

The results exhibited a high-quality output voltage waveform with significantly mitigated THD, meeting grid interconnection standards. The FPGA-based control ensured precise implementation

of Hexagonal SVM, leading to balanced capacitor voltages and reduced neutral point fluctuations. During operation, the inverter achieved efficient power transfer with minimal switching

losses, maintaining a unity power factor. Under varying load and PV irradiance conditions, the system demonstrated stability and robustness, with the grid-synchronized output current closely

matching the reference waveform. The thermal performance of the IGBT switches indicated uniform heat distribution, ensuring reliable operation. With the potential for scalability and

increased energy efficiency, our results validate the feasibility of the suggested system for sophisticated grid-connected PV applications. Figure 18 displays the five-level NPC inverter’s

experimental output voltage. Additionally, Fig. 19 illustrates the use of hexagonal SVM for capacitor voltage imbalance minimization. CONCLUSION This research presents a transformerless

five-level neutral point clamped (NPC) inverter with a coupled inductor for grid-connected PV systems, addressing key challenges such as total harmonic distortion (THD) reduction, common

mode voltage (CMV) mitigation, and neutral current balancing. The proposed system is controlled using Hexagonal Space Vector Modulation (HSVM) to optimize output voltage levels and enhance

overall performance. Through simulation and experimental validation, the proposed inverter demonstrates high efficiency, improved power quality, and compliance with grid standards under

varying operating conditions. The results confirm the effectiveness of the topology in minimizing CMV, reducing THD, and ensuring system stability. The findings suggest that the proposed

system offers a cost-effective and reliable solution for integrating renewable energy into the grid, making it a promising approach for future sustainable power generation applications. The

highlight of the work includes: * The CMV level is reduced to Vdc/6 times of applied input voltage. * The capacitor unbalance is minimized to 1.2%. * The THD range is minimized to 1.26% for

output voltage and 4.98% for output current. DATA AVAILABILITY The datasets used and/or analyzed during the current study available from the corresponding author on reasonable request.

ABBREVIATIONS * PV: Photovoltaic * MPPT: Maximum Power Point Tracking * NPC: Neutral Point Clamped inverter * PO: Perturb and Observe * VSI: Voltage Source Inverter * THD: Total Harmonic

Distortion * NSV: Nearest Switching Vector * CMV: Common Mode Voltage * CVU: Capacitor Voltage Unbalance * MI: Modulation Index * NPF: Neutral Point Fluctuation * FPGA: Field Programmable

Gate Array * EMI: Electromagnetic Interference * PWM: Pulse width modulation * HSVPWM: Hexagonal Space Vector pulse width modulation * VDC : Supply voltage * Vout : Output voltage * IL :

Photo generated current * ID : Diode current * Ish : Shunt current * I: Output current * Mi: Medium Vectors * Si: Small Vectors * Li: Large Vectors * Ts: Switching frequency * Vc: Capacitor

Voltage REFERENCES * Sandeep, N. & Yaragatti, U. R. Design and implementation of a sensorless multilevel inverter with reduced part count, IEEE Trans. Power Electron., vol. 32, no. 9,

pp. 6677–6683, Sep. (2017). * Zhang, X., Zhao, T., Mao, W., Tan, D. & Chang, L. Multilevel inverters for grid-connected photovoltaic applications: examining emerging trends. _IEEE Power

Electron. Mag_. 5 (4), 32–41 (Dec. 2018). * Aghazadeh, A., Davari, M., Nafisi, H. & Blaabjerg, F. Grid integration of a dual two-level voltage-source inverter considering grid impedance

and phase-locked loop. _IEEE J. Emerg. Sel. Top. Power Electron._ 9 (1), 401–422 (Feb. 2021). * Chen, K., Jiang, W. & Wang, P. An extended DPWM strategy with unconditional balanced

neutral point voltage for neutral point clamped three-level converter, IEEE Trans. Ind. Electron., vol. 66, no. 11, pp. 8402–8413, Nov. (2019). * Tanaka, Y. et al. Three-level neutral point

clamping PWM inverter and neutral point voltage controller. _U S Patent_ (2004). 6 795 323 B2, Sep. 21. * Xu, S. et al. Operation of a seven-level T-type active neutral-point-clamped

converter with modified level-shifted PWM, IEEE Trans. Ind. Electron., vol. 68, no. 11, pp. 10970–10981, Nov. (2021). * Zhuang, J. et al. Active neutral point clamped inverter, zero-crossing

switching method and zero-crossing switching apparatus thereof. _U S Patent 2018_ (2018). /0316 276 A1, Nov. 1. * Gao, F. Non-isolated photovoltaic grid-connected inverter and control

method therefor, WO 2013/163777 AI, Nov. 7, (2013). * Rojas, C. A., Aguirre, M., Kouro, S., Geyer, T. & Gutierrez, E. Leakage current mitigation in photovoltaic string inverter using

predictive control with fixed average switching frequency, IEEE Trans. Ind. Electron., vol. 64, no. 12, pp. 9344–9354, Dec. (2017). * Srivastava, A. & Seshadrinath, J. A single-phase

sevenleveltriple boostinverter for grid-connected transformerless PV applications, IEEE Trans. Ind. Electron., vol. 70, no. 9, pp. 9004–9015, Sep. (2023). * Dhara, S. & Somasekhar, V. T.

A nine-level transformerless boost inverter with leakage current reduction and fractional direct power transfer capability for PV applications, IEEE J. Emerg. Sel. Topics Power Electron.,

vol. 10, no. 6, pp. 7938–7949, Dec. (2022). * Majumdar, S., Jana, K. C., Pal, P. K., Sangwongwanich, A. & Blaabjerg, F. Design and implementation of a single-source 17-level inverter for

a single-phase transformer-less grid-connected photovoltaic systems, IEEE J. Emerg. Sel. Topics Power Electron., vol. 10, no. 4, pp. 4469–4485, Aug. (2022). * Salem, A., Van Khang, H.,

Jiya, I. N. & Robbersmyr, K. G. Hybrid three-phase transformer-based multilevel inverter with reduced component count. _IEEE Access._ 10, 47754–47763 (2022). Article  Google Scholar  *

Karthik, A. & Loganathan, U. A reduced component count five-level inverter topology for high reliability electric drives, IEEE Trans. Power Electron., vol. 35, no. 1, pp. 725–732, Jan.

(2020). * Yadav, A. K., Gopakumar, K., Umanand, K. R. R. L., Bhattacharya, S. & Jarzyna, W. A hybrid 7-level inverter using low-voltage devices and operation with single DC-link, IEEE

Trans. Power Electron., vol. 34, no. 10, pp. 9844–9853, Oct. (2019). * Amamra, S., Meghriche, K., Cherifi, A. & Francois, B. Multilevel inverter topology for renewable energy grid

integration, IEEE Trans. Ind. Electron., vol. 64, no. 11, pp. 8855–8866, Nov. (2017). * Lewicki, A., Odeh, C. & Morawiec, M. Space vector pulsewidth modulation strategy for multilevel

cascaded H-bridge inverter with DC-link voltage balancing ability. _IEEE Trans. Ind. Electron._ 70 (2), 1161–1170 (Feb. 2023). * Khan, M. N. H. et al. Transformerless inverter topologies for

single-phase photovoltaic systems: A comparative review, IEEE J. Emerg. Sel. Topics Power Electron., vol. 8, no. 1, pp. 805–835, Mar. (2020). * Xiao, H. Overview of transformerless

photovoltaic grid-connected inverters, IEEE Trans. Power Electron., vol. 36, no. 1, pp. 533–548, Jan. (2021). * Grigoletto, F. B. Five-level transformerless inverter for single-phase solar

photovoltaic applications, IEEE J. Emerg. Sel. Topics Power Electron., vol. 8, no. 4, pp. 3411–3422, Dec. (2020). * Gupta, B. K., Sekhar, K. R. & Kumar, A. A novel multigain single-stage

grid-connected inverter with asynchronous switching for intra-inverter circulating current elimination, IEEE Trans. Power Electron., vol. 37, no. 12, pp. 15641–15653, Dec. (2022). * Aamri,

F. E. et al. Jul., Stability analysis for DC-link voltage controller design in single-stage single-phase grid-connected PV inverters, IEEE J. Photovolt., vol. 13, no. 4, pp. 580–589, (2023).

* Dekka, A., Ramezani, A., Ouni, S. & Narimani, M. A new five-level voltage source inverter: Modulation and control, IEEE Trans. Ind. Appl., vol. 56, no. 5, pp. 5553–5564, Sep./Oct.

(2020). * Tak, N., Chattopadhyay, S. K. & Chakraborty, C. Performance of reduced-DC-source-based three-phase high-resolution multilevel inverter with optimal asymmetry, IEEE Trans. Power

Electron., vol. 37, no. 9, pp. 10713–10726, Sep. (2022). * Tak, N. & Chattopadhyay, S. K. Single dc source based three phase high resolution transformerless multilevel inverter, in

Proc. IEEE IAS Glob. Conf. Emerg. Technol., pp. 527–532 (2022). * Samylingam, L., Aslfattahi, N., Saidur, R., Mohd, S. & Afzal, A. Solar energy materials and solar cells thermal and

energy performance improvement of hybrid PV / T system by using Olein palm oil with MXene as a new class of heat transfer fluid. _Sol Energy Mater. Sol Cells_. 218, 110754.

https://doi.org/10.1016/j.solmat.2020.110754 (2020). Article  CAS  Google Scholar  Download references ACKNOWLEDGEMENTS The authors extend their appreciation to the Deanship of Scientific

Research at King Khalid University for funding this work under Grant No. RGP2/306/44. This research was partially funded by a grant from Multimedia University, Malaysia (MMUI/220086). AUTHOR

INFORMATION AUTHORS AND AFFILIATIONS * Department of Electrical and Electronics Engineering, College of Engineering and Technology, SRM Institute of Science and Technology, Kattankulathur,

Chennai, Tamilnadu, 603203, India R. Palanisamy & K. Vijayakumar * Faculty of Engineering and Informatics, Department of Computer Science & Engineering, Ala-Too International

University, Bishkek, Kyrgyzstan Mohammad Imtiyaz Gulbarga * Department of Industrial Engineering, College of Engineering, King Khalid University, P.O. Box 394, Abha, 61421, Saudi Arabia

Mohammed Al Awadh * Center for Engineering and Technology Innovations, King Khalid University, Abha, 61421, Saudi Arabia Mohammed Al Awadh * Centre for Intelligent Cloud Computing (CICC),

COE of Advanced Cloud, Faculty of Information Science & Technology, Multimedia University, Jalan Ayer Keroh Lama, Bukit Beruang, Melaka, 75450, Malaysia Liew Tze Hui Authors * R.

Palanisamy View author publications You can also search for this author inPubMed Google Scholar * K. Vijayakumar View author publications You can also search for this author inPubMed Google

Scholar * Mohammad Imtiyaz Gulbarga View author publications You can also search for this author inPubMed Google Scholar * Mohammed Al Awadh View author publications You can also search for

this author inPubMed Google Scholar * Liew Tze Hui View author publications You can also search for this author inPubMed Google Scholar CONTRIBUTIONS R. Palanisamy: Writing – original draft,

Methodology, Investigation, Formal analysis, Conceptualization. Vijayakumar K: Writing – original draft, Validation, Methodology, Investigation, Formal analysis, Conceptualization. Mohammad

Imtiyaz Gulbarga: Formal analysis, Methodology, Software, Validation. Mohammed Al Awadh: Visualization, Validation, Methodology, Investigation, Formal analysis, Conceptualization. Liew Tze

Hui : Investigation, Methodology, Software, Validation, Visualization, Writing – review & editing. CORRESPONDING AUTHORS Correspondence to R. Palanisamy or Liew Tze Hui. ETHICS

DECLARATIONS COMPETING INTERESTS The authors declare no competing interests. ADDITIONAL INFORMATION PUBLISHER’S NOTE Springer Nature remains neutral with regard to jurisdictional claims in

published maps and institutional affiliations. RIGHTS AND PERMISSIONS OPEN ACCESS This article is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International

License, which permits any non-commercial use, sharing, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the

source, provide a link to the Creative Commons licence, and indicate if you modified the licensed material. You do not have permission under this licence to share adapted material derived

from this article or parts of it. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line

to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will

need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by-nc-nd/4.0/. Reprints and permissions ABOUT THIS

ARTICLE CITE THIS ARTICLE Palanisamy, R., Vijayakumar, K., Gulbarga, M.I. _et al._ Neutral point clamped inverter for enhanced grid connected PV system performance based on hexagonal space

vector modulation. _Sci Rep_ 15, 18881 (2025). https://doi.org/10.1038/s41598-025-02506-w Download citation * Received: 13 January 2025 * Accepted: 13 May 2025 * Published: 29 May 2025 *

DOI: https://doi.org/10.1038/s41598-025-02506-w SHARE THIS ARTICLE Anyone you share the following link with will be able to read this content: Get shareable link Sorry, a shareable link is

not currently available for this article. Copy to clipboard Provided by the Springer Nature SharedIt content-sharing initiative KEYWORDS * Photovoltaic (PV) systems * Total harmonic

distortion (THD) * Common mode voltage (CMV) * Transformerless five-level neutral point clamped (NPCI) inverter * Capacitor voltage unbalance (CVU)