Summary
Jiangsu Hengke New Material Co., Ltd. faced poor power factor, utility penalties, and harmonic distortion associated with motor-driven production loads and six-pulse variable frequency drives.
SET adopted a coordinated architecture combining two 450 A Active Harmonic Filter panels with four 400 kVAr Static Var Generator panels. The project report indicates improved harmonic compensation and more stable reactive power support after implementation.
Project Background
Jiangsu Hengke New Material Co., Ltd. operates a large-scale petrochemical manufacturing site in Nantong, Jiangsu Province. Located within the Hengli Textile New Material Industrial Park, the site forms part of an integrated production base for differentiated and functional fibers, polyester materials, and other high-performance textile materials. The industrial park is being developed in phases, with a total planned investment of RMB 20 billion and an annual planned production capacity of 2.4 million tonnes.
As a continuous-process manufacturing facility, the site relies heavily on motor-driven equipment, including pumps, compressors, fans, spinning machines, and auxiliary process systems. To improve process control and operational flexibility, many of these loads are operated through variable frequency drives.
At this site, six-pulse frequency converters generated characteristic harmonic currents, while the large and continuously changing inductive motor loads caused fluctuating reactive power demand. The resulting power factor issues led to significant utility penalties. A coordinated power quality solution was therefore required to improve power factor, provide dynamic reactive power compensation, and manage harmonic conditions without creating additional risks for conventional capacitor-based compensation equipment.
Power Quality Challenge
The site presented two related power quality problems:
- Dynamic reactive power demand: Motor loading changed with production conditions, causing the required reactive compensation capacity to vary over time.
- Harmonic current from six-pulse drives: The main reported harmonic components were the 5th and 7th orders, which are characteristic of six-pulse rectifier loads.
Using only fixed capacitor stages would not adequately respond to rapid load variation. In addition, capacitors connected to a harmonic-rich system may experience increased current and thermal stress or interact with system impedance to form a resonance condition.
The project therefore required separate control paths for harmonic current and reactive current, coordinated at the low-voltage distribution level.
Hybrid AHF + SVG Solution Architecture
The project configuration comprised:
- 2 × 450 A Active Harmonic Filter panels for harmonic current compensation;
- 4 × 400 kVAr Static Var Generator panels for dynamic reactive power compensation;
- Real-time load-current detection through current transformers;
- Parallel connection to the affected low-voltage bus sections.
The Active Harmonic Filters monitor the nonlinear load current, calculate the harmonic components, and inject compensating current with the opposite phase. The filtering strategy focuses on the dominant harmonic orders generated by the six-pulse drives, particularly the 5th and 7th harmonics.
The Static Var Generators independently calculate the reactive component of the load current and deliver continuously adjustable capacitive or inductive reactive current. This allows the system to follow changing motor loads more quickly and precisely than conventional stepped capacitor switching.
Separating the AHF and SVG functions prevents the reactive compensation equipment from being treated as a substitute for harmonic filtering. The architecture also makes commissioning and capacity allocation clearer: AHF capacity is selected from harmonic current demand, while SVG capacity is selected from reactive power demand.
Key System Configuration
| Equipment | Quantity | Rated Capacity | Primary Function |
|---|---|---|---|
| Active Harmonic Filter panel | 2 sets | 450 A per panel | Mitigation of load harmonic current, including dominant 5th- and 7th-order components |
| Static Var Generator panel | 4 sets | 400 kVAr per panel | Dynamic reactive power compensation and power factor improvement |
Deployment Plan
1. Baseline Measurement
Power quality measurements should be collected during representative production cycles. The assessment should include phase current, active and reactive power, power factor, THDi, THDv, individual harmonic orders, load variation, and transformer loading.
Measurements should distinguish harmonic current demand from reactive current demand. This separation is necessary because AHF capacity is stated in amperes, whereas SVG capacity is stated in kVAr.
2. Capacity Allocation
The two 450 A AHF panels should be allocated according to the measured harmonic current and the distribution of the six-pulse drive loads. The four 400 kVAr SVG panels should be assigned according to the reactive power demand of the relevant bus sections and the plant’s power factor target.
Engineering allowance should be included for load simultaneity, operating variation, future equipment expansion, ambient temperature, and panel ventilation.
3. Parallel Connection and CT Coordination
Both AHF and SVG panels should be connected in parallel with the affected low-voltage distribution system. CT location, polarity, phase sequence, ratio, and signal sharing must be checked carefully so that each controller interprets the load current correctly.
Where several panels operate in parallel, the control settings must ensure stable load sharing and prevent one panel from reaching its current limit while the others remain underutilized.
4. Commissioning Sequence
Commissioning should be performed in stages:
- Verify primary wiring, protection, grounding, ventilation, and communication;
- Confirm CT installation and current direction;
- Commission SVG reactive compensation and confirm stable power factor response;
- Commission AHF harmonic filtering and confirm the selected harmonic priorities;
- Operate the combined system under changing production loads;
- Record before-and-after measurements at the same monitoring point.
5. Acceptance and Monitoring
Acceptance should be based on confirmed site measurements rather than controller display values alone. The plant should record the measurement point, production condition, active filter output current, SVG reactive output, power factor, THDi, THDv, individual harmonic content, equipment temperature, and alarm status.
Advantages of the AHF + SVG Architecture
Independent Control of Two Power Quality Problems
The AHF handles nonlinear harmonic current, while the SVG handles dynamic reactive current. Each device is therefore applied to the electrical quantity it is designed to control.
Fast Response to Changing Motor Loads
Petrochemical processes can produce rapid load changes as pumps, compressors, fans, and process lines enter different operating states. SVG compensation adjusts continuously rather than waiting for fixed capacitor steps to switch.
Targeted Mitigation of Drive Harmonics
The AHF can identify and compensate multiple harmonic orders simultaneously, including the dominant 5th and 7th components associated with six-pulse converters.
Reduced Dependence on Fixed Capacitor Switching
Dynamic SVG output reduces frequent capacitor-step switching and avoids overcompensation or undercompensation during changing production demand.
Lower Resonance Exposure
Using active compensation reduces reliance on fixed LC branches. This helps avoid introducing an unsuitable tuning point into a system that already contains significant drive-generated harmonics.
Modular Capacity and Operational Flexibility
Multiple AHF and SVG panels can share the required compensation output. This modular arrangement supports staged operation, maintenance planning, and future production expansion.
Reported Result
The project description reports that the combined system produced an effective compensation result. The AHF panels reduced the harmonic current associated with the plant’s drive loads, while the SVG panels supplied dynamic reactive power to support power factor improvement.
The configuration directly addressed the two conditions identified during the project assessment: 5th- and 7th-order harmonic current from six-pulse frequency converters, and insufficient power factor caused by the plant’s varying motor load.
FAQ
Q: Why did this project use both AHF and SVG equipment?
A: The plant had both harmonic current and reactive power problems. An AHF mitigates harmonic current generated by nonlinear loads, while an SVG dynamically compensates reactive current. One device should not be assumed to replace the other.
Q: Why are the 5th and 7th harmonics important at this site?
A: Six-pulse rectifier front ends commonly generate characteristic harmonic currents around the 5th and 7th orders. The actual magnitude depends on the drive design, source impedance, load level, and other equipment connected to the bus.
Q: Why not use only capacitor banks to improve power factor?
A: Fixed or stepped capacitor banks can provide reactive power, but they do not actively cancel harmonic current. In a harmonic-rich network, capacitors may also experience additional current or interact with the system impedance. Site measurements are needed before selecting a capacitor-only solution.
Q: How should AHF capacity be selected?
A: AHF capacity should be based on measured harmonic current at the selected compensation point, together with load simultaneity, future growth, ambient conditions, and the required residual distortion level. It should not be selected solely from transformer rating or total load current.
Q: How should SVG capacity be selected?
A: SVG capacity should be based on the maximum and varying reactive power demand, the target power factor, expected load changes, and any need for inductive as well as capacitive compensation.
Q: Can multiple AHF and SVG panels operate in parallel?
A: Yes. Parallel operation is suitable for large or distributed loads, but CT arrangement, controller settings, communication, current sharing, protection, and commissioning sequence must be coordinated.