Successful application of Delta’s static var generator in Quanzhou Xiaocuo Wharf
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1 Project Background
The bridge crane and belt transmission of Xiaocuo Wharf in Quanzhou, Fujian use a large number of high-power variable frequency power supplies, which are frequently started, resulting in large reactive power fluctuations in the system, resulting in voltage fluctuations and low power factor problems, which will result in a certain amount of power factor fines every month. . At the same time, high-power variable frequency speed regulation power supply is used, which produces large harmonic interference and seriously affects the power quality of the power distribution system. Therefore, the filtering and compensation equipment of Xiaocuo Wharf must have fast response speed, high filtering efficiency and compensation effect in order to meet the power distribution system. power quality requirements.
As a result, the Xiaocuogang high-voltage compensation cabinet has not been put into operation since 2001. The main reasons why the original 10kV high-voltage compensation cabinet could not be put into use are:
(1) Since the portal cranes and bridge cranes in Xiaocuogang are fast-changing loads, the reactive power fluctuates greatly during operation; the compensation cabinets in the high-voltage power distribution room belong to static compensation cabinets, which cannot meet the fast-changing operation of the portal cranes and bridge cranes. Due to the needs of work, the compensation capacitor is often caused by the input time lag, resulting in over-compensation or under-compensation of the system. At the same time, frequent switching will also cause rapid damage to the components of the compensation cabinet.
(2) The main electrical loads in Xiaocuogang are portal cranes and bridge cranes. The main power sources of door cranes and bridge cranes are high-power inverter-controlled power sources. When high-power variable-frequency power sources are running, they will generate a large amount of high-frequency harmonic content, mainly the 5th, 7th, 11th, and 13th harmonics. , the high-frequency harmonic content leads to the reduction of capacitor capacitive reactance and the abnormal increase of capacitor current, which causes the compensation cabinet not only to fail to compensate the system inductive reactive current, but to increase the system current with the input of the capacitor, amplifying the system harmonic content , the system power factor cannot meet the standard, and the compensation cabinet cannot be put into normal operation due to abnormality.
From this, it can be understood that the main power quality problem in Xiaocuogang is that the rapid fluctuation of reactive power causes system voltage fluctuations, and at the same time, it also causes reactive power compensation to fail to track, resulting in the failure of reactive power compensation. In addition, the quality of the power supply is degraded due to the harmonic content generated by high-power inverters.
2 Solutions
Due to the load characteristics of Xiaocuogang portal cranes and bridge cranes, the high-voltage power distribution system is required to be equipped with a high-efficiency dynamic reactive power compensation device. The device should have the following characteristics: rapid and continuous compensation. The response speed should be less than 10ms; it can withstand and eliminate certain harmonic content. To this end, Delta Dentsu provided Delta’s active filter product solutions.
Delta’s active filter PQCS adopts direct PWM current control technology, and its output current waveform and phase are fully controllable. PQCS can operate within the range of rated inductive to rated capacitive. Since there is no need for large-capacity capacitors and reactors as energy storage elements, the footprint of PQCS is only 50% of that of SVC with the same capacity.
3 Features and effects of the filter compensation method of Delta’s active filter PQC-RPQCS
(1) PQCS can compensate in both directions, which can compensate both capacitive reactive power and inductive power, which is suitable for the load characteristics of bridge cranes when they are lifted and lowered;
(2) PQCS response speed <5ms;
(3) PQCS can ensure that the system power factor is above 0.97, and the voltage fluctuation range conforms to the national standard;
(4) PQCS can both compensate system reactive power and eliminate system harmonics;
(5) PQCS is basically not affected by the background harmonics of the system;
(6) PQCS is connected in parallel to the system, which can be easily expanded in parallel with the increase of system load capacity or the change of operation mode.
4 Project benefits
After using Delta’s PQCS series of active filters, the power saving of Xiaocuo Wharf is as follows:
(1) Power rate electricity bill
At present, the system uses a large number of frequency converters, the power factor is considered as 0.9, the system load is 4360kVA, after using PQCS, the system power factor is above 0.97, the power rate reward ratio is -0.75%, and the electricity fee is 0.65 yuan/kWh. Calculated according to the annual operating time of 8000h: Annual power saving rate of electricity = 4360 × 0.75% × 0.65 × 8000 = 170,000 yuan
(2) Operational efficiency of traditional FC and PQCS saves electricity
The new generation of active PQCS dynamic reactive power compensation and harmonic control device has low operation loss and small footprint, which brings obvious economic benefits to users. The operating loss of the FC filter compensation device of the thyristor-controlled capacitor-reactor bank is about 1.2%, and the operating loss of the active PQCS is about 0.5%. Considering the capacity of 1M, the annual running time is 8000h, and the electricity cost is 0.65 yuan/kWh to calculate:
Annual saving of running loss electricity = 0.65 × 1000 × (1.2%-0.5%) × 8000 = 36,400 yuan
The above two electricity-saving costs are about 206,400 yuan, and the economic benefits are significant.
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