JPH025624Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a harmonic suppression device that is connected to an electric power system, supplies current to compensate for harmonic current generated in a load, and suppresses generation of harmonics in the electric power system.

A harmonic suppression device includes, for example, a pulse width modulation (PWM) thyristor converter, a constant current source such as a DC reactor on the DC side of the converter, and a filter for removing the PWM carrier wave component on the AC side of the converter. A harmonic component waveform obtained from the detected current of the power system is used as a modulation wave for PWM control of the thyristor converter, and a harmonic-compensated current output is obtained from the converter.

These harmonic suppression devices have a good harmonic suppression effect under normal power system conditions, but when there are no harmonic generation factors in the power system, the devices may actually become a cause of harmonic generation. .

This idea was made in view of the above-mentioned circumstances.
By determining whether harmonics are expected to occur in the power system based on the magnitude of the grid current or harmonic current, and stopping the harmonic suppression operation as necessary based on this determination, it is possible to perform appropriate harmonic suppression. The purpose of the present invention is to provide a harmonic suppression device that achieves the following.

FIG. 1 shows an embodiment of the present invention, in which the harmonic suppression operation is stopped due to the magnitude of the grid current. In order to supply power from the power source 1 to the load 2, the harmonic suppressor main body 3 is connected to the grid. The device body 3 detects harmonic components from the system current detection signal obtained from the current transformer 4, and supplies a necessary compensation current to the system based on this detected value. Here, in this embodiment, the detected current of the current transformer 4 is also taken into the rectifier circuit 5 to obtain an absolute value signal of the system current by the rectifier circuit 5, and this absolute value signal is passed through the low-pass filter 6. This average value is used as a comparative input of the comparator 7 and compared with the set value, and when the average value becomes less than the set value, the output of the comparator 7 is used as a command to stop the operation of the harmonic suppression device main body 3. I have to. The set value of the comparator 7 serves as a criterion for determining the magnitude of the grid current. Therefore, when the grid current drops below a certain value, the harmonic suppression operation is stopped and the device main body 3
This eliminates unnecessary operating power and prevents harmonics from occurring in the system. Since this operation control is the operation control of the device main body 3 according to the magnitude of the grid current, the control is performed at an appropriate time regardless of daily or hourly changes in the power grid state. In addition, comparator 7
It is preferable to determine the setting value by actually operating the device main body 3 and measuring the system current state in which the device main body becomes a harmonic generation source.

FIG. 2 shows another embodiment of the present invention, in which the operation of the main body of the apparatus is controlled based on the magnitude of harmonic current in the system. The detected current of the current transformer 4 is extracted as a harmonic component signal by removing the fundamental wave component by a band reject filter 8, and this signal is sent to a rectifier circuit 9.
The average signal is then passed through a low-pass filter 1 to convert it into an absolute value and an average value, and this average value signal is compared with a set value in a comparator 11. From this comparison result, when the magnitude of the harmonic exceeds the set value, The harmonic suppression device main body 3 is controlled to stop.

In this embodiment, since the harmonic suppression operation is stopped directly depending on the magnitude of the harmonic, harmonic suppression can be performed appropriately without being affected by changes in the daily load pattern of the system. Note that the harmonic signal detected by the band reject filter 8 is also used as a control signal for the main body 3 of the apparatus.

As described above, according to the present invention, since it is determined from the grid current or grid harmonic current that the harmonic suppression device is a cause of harmonic generation and the device is controlled to stop, harmonic suppression in the grid is ensured and appropriate. This has the effect of making it possible to reduce energy consumption, and it also has the effect of reducing power consumption by lowering the device transfer rate.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram showing one embodiment of the present invention;
The figure is a circuit diagram showing another embodiment of the present invention. 2...Load, 3...Harmonic suppressor main body, 5,
9... Rectifier circuit, 6, 10... Low pass filter, 7, 11... Comparator, 8... Band reject filter.

Claims (1)

[Scope of utility model registration request] In a harmonic suppression device that is connected to a power grid and supplies current to compensate for harmonic current generated in a grid load, harmonics are detected by comparing the magnitude of the grid current or the harmonic current included in the grid current with a set value. A harmonic suppression device characterized by comprising a control means for controlling operation and stop of a wave suppression operation.