Can Active Power Filters (APF) and Static Var Generators (SVG) Provide Significant Solutions for the Rapidly Growing EV Charging Pile/Station Market?

Can Active Power Filters (APF) and Static Var Generators (SVG) Provide Significant Solutions for the Rapidly Growing EV Charging Pile/Station Market?

As global EV ownership surges, power quality issues in charging infrastructure have become increasingly prominent. As nonlinear loads, EV chargers generate harmonic pollution and reactive power fluctuations during operation, leading to grid voltage distortion, equipment overheating, and reduced energy efficiency. In severe cases, this may trigger false operations of electrical protection devices. Active Power Filters (APF) and Static Var Generators (SVG), as dynamic mitigation devices, not only effectively address these issues but can also reduce overall operational costs through innovative technical integration. This analysis systematically examines the core value of these two technologies in charging facilities from technical principles, application solutions, and economic perspectives.

1. Power Quality Issues Caused by EV Chargers

EV chargers (especially on-board chargers in AC piles) typically adopt three-phase uncontrolled rectifier topologies, whose nonlinear characteristics cause severe current waveform distortion. Test data show that a single 7kW AC pile under full load can generate 25%-35% Total Harmonic Distortion of current (THDi), with dominant 5th, 7th, and 11th harmonics. When multiple piles operate simultaneously, harmonic current superposition may overheat distribution transformer windings, accelerate insulation aging, and even cause electrical fires.

Concurrently, phase control in chargers results in power factor (PF) fluctuations between 0.6-0.8, far below the grid standard of >0.9. For example, measurements from a 10-pile station show an average PF of 0.72 without compensation, meaning ~30% of apparent power constitutes reactive components. This increases line losses and causes voltage sags. Crucially, harmonic currents passing through traditional energy meters (designed for fundamental waves) result in 5%-15% underbilling of actual energy consumption, directly reducing operator revenue.

Table: Typical Power Quality Issues in Charging Stations

2. Active Power Filter Solutions

For harmonic mitigation, integrated APFs have become critical. Advanced designs embed H-bridge converters directly into charger topologies, achieving "localized harmonic elimination" via post-meter parallel connection. A 7kW prototype developed by Anhui University of Technology employs dual-zero proportional resonant control, reducing grid-side THDi to <3% with >95% compensation accuracy for harmonics below 30th order.

Modular H-bridge APFs demonstrate significant advantages: 50% lower DC bus voltage requirement (650VDC), 40% reduced output current ripple, and ~25% lower switching losses. Deployment at a bus charging station (20×120kW DC piles) showed THDi reduction from 29.7% to 2.1%, saving $17,000/year in avoided penalties.

Breakthroughs in control algorithms enhance dynamic response. Discrete Sliding-Window Fourier Transform (DSFT) detects harmonics within 1ms, while PI + repetitive composite control achieves <10ms transient response—critical for EV charging’s step-changing profiles.

3. Static Var Generator Solutions

SVGs regulate capacitive/inductive current via voltage-source inverters, responding 100× faster (<5ms) than capacitor banks. In Hunan Electric Power’s coordinated system, chargers handle PF correction (±0.95 range) while SVGs provide dynamic reactive support during voltage transients.

The core multi-objective optimization model minimizes configuration cost and voltage deviation, constrained by initial SOC and battery characteristics. Simulations show SVGs restore voltage to ±2% nominal within 0.2s during 8% sags. Optimized SVG sizing reduces required capacity by 35% (e.g., 1.2Mvar vs. 2Mvar for 30 piles).

Table: SVG Configuration Economics

4. Hybrid Systems & Innovations

Cutting-edge research integrates APF/SVG functionalities. India’s Sreenidhi Institute proposes a three-level Hybrid APF (HAPF) combining harmonic suppression and reactive compensation, powered by renewable DC buses. Its Jaya-Grey Wolf hybrid algorithm (GWJA) reduces voltage stabilization time by 50% and maintains THDi<4% under PV fluctuations.

T-type three-level inverters emerge as a key trend, halving switch voltage stress—especially vital for 800V ultra-fast charging. Tests on 350kW systems show 98.2% efficiency, 2.5% higher than two-level designs.

5. Techno-Economic Analysis

Despite higher upfront costs ($20-40/kW), APF/SVG delivers compelling ROI:

• Harmonic billing loss elimination: Saves ~$120/year per 7kW AC pile
• Reduced communication faults: Maintenance costs down 60%
• PF incentive rebates: 0.5% electricity bill rebate for PF>0.95
• Extended equipment life: Transformer lifespan increases 3-5 years

For large stations (30×120kW piles + 1.2Mvar SVG):

• Avoided PF penalties: ~$3,000/month savings
• Lower transformer costs: 35% reduction ($50,000 saved) via downsizing
• Improved voltage stability: 90% fewer charging interruptions

6. Application Recommendations

• Distributed AC piles (residential/commercial): Built-in APF for 7-22kW piles
• Centralized stations (bus depots/highways): "SVG + clustered APF" with SVG sized at 30%-40% of total load
• Renewable-integrated stations: Three-level HAPF with GWJA optimization

7. Future Trends

Wide-bandgap devices (SiC/GaN) will enable higher frequency (>50kHz) and smaller APF/SVG (40% size reduction), ideal for space-constrained sites. Deep reinforcement learning algorithms will predict harmonic trends for 99% compensation accuracy.

New standards (e.g., China’s 2023 Technical Specification for Power Quality Management) mandate THDi≤5% and PF≥0.95, creating non-negotiable demand for APF/SVG solutions.