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When operating, various electric equipment all require some reactive power to set up electromagnetic field or some other working environments for the normal operation of the equipment. Reactive power increases total current in circuit and reactive loss of electric line, meanwhile it also lead to the problems of decrease in receiving-side voltage, decline in utilization of electric equipment, etc. For the reactive power needed by power users, it adopts the nearest track compensation which can effectively reduce line losses, improve voltage quality, fully work out the potentialities of power supply equipment, and save electricity costs for users. Thus it is characterized by economic and social benefits.

As power electronic equipment are increasingly widely used today, many industrial equipment are characterized by high content of harmonics, rapid fluctuations of reactive power demand, which increase the harmonic content and fluctuations of reactive power in power distribution system. Traditional capacitor reactive power compensation equipment are deficient in incapacity of restraining harmonics, low switching speed, impulsive transient, etc. so they cannot rapidly conduct dynamic compensation with load reactive power. Besides, they can also cause problems of ultra-harmonics amplification, harmonic resonance, overload and burnout of compensating equipment, etc, which would prevent normal running.

PFMax-V Series dynamic reactive power compensator for dynamic harmonic elimination is the automatic dynamic reactive power compensator for dynamic harmonic elimination, adopting microprocessor control, thyristor switched tuning capacitor-TSC. It is the renewal product of reactive-load compensation equipment. The product uses real-time detection of reactive power microprocessor, thyristor zero fast switching transition, restraining harmonic current and other advanced technologies, so the product can thus be used in various complex industrial field environments. It can conduct accurate, rapid, not transiently disturbed dynamic reactive power compensation, effectively enhance power factors of various electric equipment, enhance output of power equipment, improve user power quality, decrease line loss, and attain the goals of energy saving and cost reducing.

Introductions to Technology Advantages of PFMax-V Series Products

1. Reactor Elimination in Series Technology
According to different field conditions, PFMax-V uses 5%-7% or 12%-14% detuning reactor in series in capacity loop, transfers harmonic frequency of capacitor or electric network to harmonic frequency lower than main ones (quintuple harmonics or triple harmonics), avoid capacitor damage or even collapse of electric network caused by capacitors and harmonic resonance. The following picture is the typical capacitor/network amplification factor graph which reflects 6% reactor in series transfers harmonic frequency of system from close to quintuple harmonics to close to triple harmonics

Series Reactor transfers system harmonic frequency to avoid the amplification of harmonic resonance

2. Transient-free switching tuning / detuning capacitor bank Technology
When capacitor bank is put into system in normal manner, it can produce huge transient flow impact, which would impose negative influences on capacitors, fling-cut switches and electric equipment. Consequently, it may reduce the service life of capacitors and fling-cut switches, produce great electromagnetic disturbance in power distribution system and disturb the normal operation of electric equipment. PFMax-V adopts zero transitional course tuning capacitor switching technology, which can completely eliminate transient flow and disturbance when capacitor bank switches, enhance greatly the tracing speed of compensating equipment, enhance the reliability of capacitors and fling-cut switches, and extend their service life.

The flow when tuning/detuning capacitor bank is put into random use Transient-free switching technology can effectively avoid input flow

3. Scan mode of capacitors
PFMax-V uses specific scan mode to protect capacitors. When the need for compensation capacity decreases, the capacitor bank that keeps on working for the longest time would be turned off first. When the need for compensation capacity increases, the capacitor bank that is not put into use for the longest time would be used first. When the need for compensation capacity keeps unchanged for a long time, electronic switches conduct alternate operation continually, according to the set intervals, switches will switch off one capacitor bank at the same time it switches on another one, thus to keep the total compensation capacity unchanged. Through such operation, it can guarantee that each capacitor bank can be put into use in alternation, avoid unbalanced operation of capacitor banks, and ensure the total external compensation capacity can meet the compensation need. Therefore, the balanced and low duty cycle can reduce the average current of capacitors, decrease their working stress and thus extend their service life.

4. High-speed real-time tracking compensation Technology
PFMax-V controller uses instantaneous reactive power theory to real-time calculation reactive power the system needs. Meanwhile it also adopts solid electronic switches to switch tuning/detuning capacitor bank during zero-transitional course, which means it can avoid surge current caused when traditional contractor switches capacitor, and it also can switch all needed capacitor banks within 20ms. All the information such as electric parameters, states of system, and detailed records of historical events can be displayed on LCD widescreen. It can also upload data to computer system through com ports, to form centralized lubrication system.

High-speed PFMax-V is an ideal solution to the control of power quality. In power distribution system, high-speed PFMax-V can reach almost perfect effects in the aspects of power factor control, electric network voltage stabilization, and energy saving and cost reducing.

In the power distribution system where active power changes rapidly, high-speed PFMax-V is the only proper compensation method. Low-speed compensation system or quasi-realtime compensation system will lower power quality, produce electrical energy waste, or even cause system resonance. The following example is the comparative result of rapidly changing reactive power compensation by high-speed PFMax-V system and quasi-realtime compensation system respectively.

The top half of the diagram shows the compensation effects by high-speed PFMax-V system. When load current increases suddenly, high-speed PFMax-V would put into use all needed capacitors within 20ms, and the total current would obviously decrease. When load is removed, high-speed PFMax-V would switch off all relevant capacitors within 20ms.

The latter part of the diagram shows the incorrect compensation mode by quasi-realtime compensation system. In the system, switching one groups capacitors requires 3 cycles, and switching all four groups requires 12 cycles. Due to the time delay of switching, compensation capacitor would be added step by step, and the total current is also reduced step by step. As to the time delay of removal, capacitor is turned off gradually, and overcompensation current thus appears. However, for the fast-changing reactive power, such compensation effects will impose negative impacts. There would be an increase in total system current instead of decrease, and overcompensation or under compensation can result in voltage fluctuation and flicker.

The following diagram is the measured data of real-time tracing compensation effects by PFMax-V series high-speed dynamic reactive power compensator for harmonic elimination. The black curve stands for the load current with rapid fluctuation, the red curve stands for the real-time tracing compensation current, and the blue curve stands for compensated side current. The tracing by PFMax-V is rapid and correct. Before compensation, the load summit current is as high as 1423 A, while after compensation it falls to 693 A. And the current fluctuation amplitude falls from around 900 A to around 350 A.

Measured data of PFMax-V real-time tracing compensation effects
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