# Design, Control and Loss Analysis of PV-based Shunt Active Filter for Improved power Quality with maximum PV power injection

Muhammad Rayyan Fazal, M.A.E. Alali, Tanguy Phulpin, Romain Le Forestier, Christophe Goasguen

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Muhammad Rayyan Fazal, M.A.E. Alali, Tanguy Phulpin, Romain Le Forestier, Christophe Goasguen. Design, Control and Loss Analysis of PV-based Shunt Active Filter for Improved power Quality with maximum PV power injection. The 26th European Conference on Power Electronics and Applications, GDR SEEDS France & EPE Association, Mar 2025, Paris, France. 10.34746/epe2025-0270. hal-05065391

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# Design, Control and Loss Analysis of PV-based Shunt Active Filter for Improved power Quality with maximum PV power injection

Muhammad Rayyan Fazal<sup>a,b,c</sup>, Mohamed Alaa Eddin Alali<sup>a</sup>, Tanguy Phulpin<sup>b</sup>, Romain Le Forestier<sup>c</sup>, Christophe Goasguen<sup>c</sup>

<sup>a</sup>QUARTZ Laboratory, EA7393, ENSEA, 6 Avenue du Ponceau, 95014 Cergy-Pontoise, France

<sup>b</sup>Université Paris-Saclay, CentraleSupélec, CNRS, GeePs, Sorbonne Université, 91192, Gif-sur-Yvette, 75252, Paris, France

<sup>c</sup>IMEON ENERGY, SA à conseil d'administration, 6 Rue de Kerbernard, 29200 Brest, France

E-Mail: rayyan.fazal@ensea.fr

## Keywords

Photovoltaic energy, MPPT algorithm, Shunt active filters, Novel grid modeling strategy, Power quality, Harmonics, Battery energy storage system

## Abstract

This research proposes the Photovoltaic (PV) based shunt active filter (SAF) connected to the storage device. This scheme generates and injects the maximum PV power into the system and ensures that the grid current is healthy by offering a high filtration quality on the grid side. It provides higher reliability, high efficiency, and increased stability. The control strategy devised for this structure works equally well for the lower and higher PV energy penetration, light and heavy loading conditions, and importing/exporting power to/from the grid. The performance of the overall scheme is analyzed by employing commercial power electronics components, MOSFETs, in the simulation using PLECS and MATLAB Simulink.

## 1. Introduction

Renewable energy resources are among the best solutions to reduce carbon footprints while offering reliability, efficiency, economic advantage, and a safe working environment. Therefore, the LCL filter of conventional series inductance: C-L series VSI grid-connected PV system is proposed for renewable energy generation [1]. The VSI is usually conventional with silicon components (C-VSI). This structure has limitations like maximum working DC voltage and switching frequency limit, i.e.,

800V/16kHz [2]. However, using the C-Lseries filter, the main concerns are difficulty in sizing, bulkiness, and heaviness while being expensive simultaneously. The output filter mainly prevents the network from high switching components and avoids system dynamics degradation [3].

In the literature [4-6], we can find an LCL-based conventional VSI alternative. It offers the additional advantages of LCL filtering, i.e., lower inductance values, while retaining the industrially adopted conventional values for DC voltage and switching frequency, i.e., 800Vdc and 16kHz. Despite offering less weight and volume than C-Lseries-based filters, the capacitive nature of the LCL filter can introduce destructive series and/or parallel resonance by interacting with the electrical networks.

Renewable energy systems like photovoltaic systems include PV panels, a converter, a voltage source inverter (VSI), and a filter [7]. The control of this circuit consists of the maximum power point detection (MPPT), regulation of DC bus voltage, and reference signal generation according to the irradiance and temperature for the converter and, hence, the corresponding current to be injected. Whereas a converter-less topology with a common control strategy is also suggested for grid-connected PV-based SAF [8]. However, its scope was limited as the PV panel arrangement was required to match the DC bus voltage, making it less flexible.

On the other hand, electrical networks must deal with various perturbations like harmonics, reactive power, and unbalance due to nonlinear loads. Various strategies like series active conditioner [9] with a comparison of multiple control approaches with and without phase lock loop (PLL) [10] have been proposed to cater to this. Still, the most modern one includes using a
Shunt active filter (SAF) [11] with a conventional VSI structure with a C-Lseries filter with simplified control. This structure resembles the previous PVG structure, which is heavy, bulky, expensive, and difficult to size, offering 800V DC bus voltage and 16kHz switching frequency.

An LCL-type filter and LCL grid connected with VSI-SAF were suggested in this context. The LCL filter had the exact value of 100µH. Using LCL in this structure is limited due to the issue of introducing a phase shift between injected and estimated harmonics and the destructive resonance problem [12]. However, unlike the PVG system, the SAF-LCL has to control the entire 2.5kHz bandwidth and use a higher-order linear controller. Meanwhile, the phase shift increases with the harmonic frequency and the output filter order. Therefore, the filtering quality is significantly degraded, and hence, the application of the SAF is affected. However, to overcome this phase shift problem, the SAF structure needs a very sophisticated and complex design, a nonlinear controller [12].

Considering all the current challenges discussed above, we propose an extended photovoltaic energy generation system integrated into VSI-SAF. In this case, the photovoltaic generators (PVGs) are installed on the upstream side of the DC bus. In addition to the perturbation compensation, this structure (PVG/SAF), in coordination with the grid, calculates and injects/dispatches the maximum power of the PV generators to the grid and loads.

**The novelty/contributions of this work are:**

1) designing a compact, reliable, and economical structure with PV and battery integration of grid-connected SAF, i.e., PVG/SAF. The PVG/SAF coordination aims to inject the MPPT-based power while ensuring high power quality on the network side.

2) A unified control strategy for MPPT detection, battery charging and discharging, and perturbation current identification under distorted grid conditions is proposed.

It is worth noting that this work presents a part of the overall project, which is an extension of the filed US patent concerning active filtering using high-switching components [13]. The principle objective of this work is to propose an extended, compact, reliable, and economic topology of renewable energy systems with storage while interacting with SAF within the main network. It offers a unique control strategy for MPPT

detection and power injection while catering to electrical perturbations (harmonics, unbalancing, etc).

We have proposed a novel structure integrating PV and battery with the SAF structure. This, in return, unifies the control algorithm of the integrated SAF structure while enhancing the overall system dynamics and stability. Also, the two-level switching-based VSI structure allows for the handling and regulating comparatively high DC bus voltages. Hence, the speed of the overall system in terms of renewable energy injection and harmonic filtration is increased.

## 2. Proposed architecture and control scheme of PV-based battery-integrated SAF

The overall structure is provided in Figure 1. It shows the proposed structural arrangement where a DC link connects the MPPT-based PV system and the battery to the SAF. Where $i_{gd}$ is the grid currents, respectively $i_{inj}$ is the injected current by SAF, PCC represents the point of common coupling, and $i_{ld}$ represents the demand current for nonlinear load. The working scheme of the SAF is also shown. However, the control scheme for reference current generation through a simple control strategy is shown in Figure 2. The control scheme utilizes the grid voltage $v_{gd}$, load current $i_{ld}$ and DC voltage control loop to identify the reference currents, i.e., $i_{inj}^*$. The Self-tuning filter (STF) is utilized in SAF control as an identification method for perturbation detection, including harmonics, reactive, and unbalanced components. In recent times, STF has been a popular technique for filtration in the literature [14] as it performs very well under dynamic conditions.

<figure><img src="image_2.png" /><figcaption>Fig. 1: Proposed PV & battery-based VSI-SAF</figcaption></figure>
<figure><img src="image_3.png" /><figcaption>Fig. 2: Proposed Control Strategy</figcaption></figure>

In this study, the structure used a high switching frequency for MOSFETs to cater to the imposed output filter constraints while allowing the introduction of an uncomplicated L-series output inductor. Hence, it prevents the switching component from propagating towards the power grid. One of the objectives of this research is to design an L-series inductor equal to the sum of LCL filter inductances and maintain the retention ratio of switching components retention, avoiding resonance or antiresonance risks. In addition, the L-series also offers 10-20 times (or more) less size than the C-Lseries, hence, one-fifth or less in weight and volume.

Therefore, a research study presents the study of LCL filter-based grid-connected SAF. This patent [13] deals with maintaining a retention rate of – 50 dB at 16 kHz switching frequency while using a sum of LCL inductors of 200 µH with $C_{LCL}=130$ µF. In this way, for L-series=200 µH, the same retention rate is archived by keeping the switching frequency of the VSI at 100 kHz. The overall structure shows significant weight and volume reduction (28 kg and 0.013 m³), i.e., a fifth and a quarter, compared to the commercialized C-Lseries with the same rated power. Meanwhile, the commercialized C-Lseries contains 2mH to 5 mH inductors used for the PVG systems, and C-SAF has operational constraints of 16kHz/800VDC with two-level Si power electronics components. The weight of the commercially available 50 kW PVG system is 70 kg, with 0.76 m height, while for 3-phase 4-wire 50A/240V conventional SAF is 70 kg for a 2 mH inductor and 105 kg for a 5 mH inductor possessing a volume of 0.066 m³ for later.

### 3. PV-based SAF Working

The shunt active filter (SAF) working under various conditions is shown in the figures below. The MATLAB Simulink/Simscape Electrical is used to carry out simulations. Different irradiance levels are used to analyze the Maximum Power Point Tracking (MPPT) of PV panels and the

response of the SAF. Also, the load has been changed to examine the overall system's working, response, and stability.

#### 3.1. System powers under dynamic irradiations and load

Figure 3 shows the maximum PV power under different irradiations (PV_Power), total demand (Load_Power), battery charging-discharging (Battery), and contribution of Grid (Grid_Power); Irradiations are selected as 100 W/m² (9720 W), 400 W/m² (40544 W), and 700 W/m² (70870 W).

<figure><img src="image_4.png" /><figcaption>Fig. 3: Load, PV, battery, and Grid power</figcaption></figure>

The corresponding DC bus voltage is shown in Figure 4. This figure indicates that the DC bus shows very stable behavior and quickly returns to normal conditions without having large spikes. That highlights the system's strength: it is very stable and efficient. An unstable DC voltage causes an output voltage imbalance that can challenge the system's stability.

<figure><img src="image_5.png" /><figcaption>Fig. 4: DC voltage under changing irradiation</figcaption></figure>
## 3.2. Analysis of our control scheme for the proposed architecture

The next step is to analyze how the SAF works against these variable conditions. We can observe from Figure 3 shows that the PV panels successfully track the maximum power with more than 99% efficiency. Also, the DC bus shows very stable behavior and quick response, as shown in Figure 4. Therefore, the nature of the load current and SAF response need to be analyzed. Consequently, we have made a condition where the load changes at 1s to check the response of the SAF and system stability. Figures 3, 4, and 5 show the corresponding results.

Figure 5 shows how SAF works under two power levels. In the first part of the simulation, i.e., till 1s, the nonlinear load of 89 kW is attached, which changes to 25 kW in the second half. We can observe that, as the irradiation of PV panels changes, the grid current value changes accordingly (Figure 5), and SAF must generate the corresponding new signal according to the system's requirements. Also, when the load changes, the SAF must change the generating signal according to the required load power.

<figure><img src="image_6.png" /><figcaption>Fig. 5: Grid current, Load current & SAF Injection current</figcaption></figure>

The topmost signal is the grid current $i_{gd}$ that is sinusoidal in shape, as shown in the zoomed pictures in Figure 5, despite being connected to the nonlinear load, i.e., the diode bridge in the Simulink. Under different changing conditions, we can analyze from Figure 5 that the grid current is adopted accordingly without being affected by the nature of the load. Also, after the load has been changed at 1s, the signal's shape doesn't change and continues to work smoothly. It may

also be noted that after every change, i.e., whether in irradiation or loading conditions, the system adapts quickly, primarily within 1 or 2 cycles. The middle signal refers to the demand current $i_{ld}$, or alternatively, the current grid has to be provided directly if we do not apply SAF to the system. Here, we have used two different load levels: high load, 89kW, connected at the beginning of the simulation, and after 1s, the load drops to a lower level, i.e., 25kW. The third signal $i_{inj}$ shows the working of SAF, i.e., the corresponding current generation being injected by the SAF to the point of common coupling between the load and the network to neutralize the effects of the perturbing nonlinear load current shown in the middle signal of Figure 5. The areas before and after load change have been zoomed in to get a better idea of the shape of the signals.

## 3.3. Simulation parameters and result discussion

Table I shows the simulation parameters. At the beginning of the simulation, the low irradiation, 100 W/m², means the PV panels generate lower power, i.e., 9720 W. Hence, against the low power, the grid power with battery discharging is included to meet the remaining part of the system. At the same time, the SAF mainly compensates for perturbations, i.e. harmonics.

<table><caption>Table I: Parameters for simulation</caption><thead><tr><th colspan="2">Simulation Parameters</th></tr></thead><tbody><tr><td colspan="2"><strong>Power Grid</strong></td></tr><tr><td>Source Voltage</td><td>220 V<sub>rms</sub></td></tr><tr><td>Frequency</td><td>50 Hz</td></tr><tr><td>Inductor</td><td>1 mH</td></tr><tr><td>Resistance</td><td>5 mΩ</td></tr><tr><td>MAF-Cut-off Frequency</td><td>100 Hz</td></tr><tr><td colspan="2"><strong>Shunt Active Filter</strong></td></tr><tr><td>L-Series Filter-inductance</td><td>0.20 mH</td></tr><tr><td>DC Link-Capacitor</td><td>450 μF</td></tr><tr><td>DC Link-Voltage</td><td>800 V</td></tr><tr><td colspan="2"><strong>PV Simulation Arrangement</strong></td></tr><tr><td>Max Power (213.15W - single panel)</td><td>100 kW</td></tr><tr><td>OCV (36.3V - single panel)</td><td>363 V</td></tr><tr><td>SCI (7.84A - single panel)</td><td>368.5 A</td></tr><tr><td>Voltage - Maximum power (29V)</td><td>290 V</td></tr><tr><td>Current - Maximum Power (7.35A)</td><td>345.5 A</td></tr></tbody></table>

In this context and from Figure 3, one can observe that at 0.5s, the irradiation of the PV power increases to 400 W/m², and more PV power is available to be injected, i.e., 40544 W. The battery still discharges at maximum capacity while the grid current is reduced accordingly. At
1s, irradiation increases to 700 W/m², and PV reaches 70,870 W, whereas, the load drops to a lower value simultaneously, i.e., from 89 kW to 25 kW. Therefore, the PV power supplies the load, and the remaining power is used to charge the battery until its maximum capacity. At the same time, the surplus is injected into the grid, as shown in Figure 3. Therefore, the load is supplied with PV power, and the surplus is sent to the grid. The SAF works efficiently in all these variations of PV power and load. It is worth noting that the surplus power injected into the grid from 1s results in grid current, phase-shifted by 180°, as shown in Figure 5. Figure 6 represents the battery's corresponding voltage, current, and state of charge (SOC). The positive and negative currents show battery discharging and charging.

<figure><img src="image_7.png" /><figcaption>Fig. 6: Battery charging/discharging</figcaption></figure>

### 3.4. THD Analysis

To further analyze the system's performance, the total harmonic distortion (THD) analysis was provided at the grid side without the work of SAF. Without the SAF, figure 7 shows the THD level for the entire simulation where the load changes at 1s can be observed. Before the load changes, 17.80% grid side THD current is observed, which becomes 25.25% after load changes. With SAF, the same grid THD current level can be observed from the upper half of Figure 7, which comes out to be 0.67% in the beginning and reaches a maximum of 4.07% in the last of the simulation while injecting surplus power into the grid, as evident from the figure. However, it is worth noting that it remains well below the IEEE-519 standard of 5%.

<figure><img src="image_8.png" /><figcaption>Fig. 7: THD of Grid before and after load change with and without our proposed scheme</figcaption></figure>

## 4. Conclusion

Our proposed scheme offers the advantages of PV and battery-based SAF integration, proving to be a compact, efficient, reliable, stable, and economical solution. It not only detects and provides the maximum power for the system but also ensures a high power quality for the grid side. Furthermore, this work also has a simplified control strategy that includes a P&O MPPT-detection algorithm and uses the output PV power for the reference signal generation. Also, an extended p-q identification algorithm combined with an advanced PLL controller is applied. The control scheme ensures grid coordination, maximum PV power generation, integration, reactive power compensation, and healthy current maintenance on the grid side, even under distorted and unbalanced grid conditions. Additionally, we have used new analytical/computation models of commercial components, e.g. C3M0021120K MOSFET- the device with an optimized switching frequency and DC voltage values.

Finally, the overall performance of the proposed structure is validated using a new modeling strategy, which is applied to the actual case study using a combination of Matlab-Simscape Electrical and PLECS. Industrial based commercial components were used to simulate the structure. More than 99% efficiency is observed with the maximum power extraction and more than 98% for the power transfer. Also, it is worth noting that our proposed scheme for PV and battery-integrated SAF structure ensures that the grid's current THD is below 5% under all significant distortion conditions, hence conforming to the IEEE standard. The presented
results are a part of the overall project. However, the work related to loss analysis and energy management is ongoing.

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