JPH0475425A - Higher harmonic current suppresser - Google Patents

Abstract

PURPOSE:To exhibit a sufficiently low impedance for basic wave current and a high impedance for higher harmonic current by producing a voltage for canceling the basic wave voltage produced in a reactor in a voltage type inverter. CONSTITUTION:A load 1 is fed with power from an AC power supply 2 and the primary of a current transformer 3 is connected in series with the charging point of the load 1. A reactor 4 and a voltage type inverter 5 are connected in series with the secondary of the current transformer 3. Secondary current of the current transformer 3 is detected through a reactor current detecting current transformer 6A and fed to a higher harmonic current eliminating means 6B and an operating means 6C operates the basic wave voltage across the reactor 4. A basic wave voltage is induced across the voltage type inverter 5 through a gate pulse generating circuit 7 in order to cancel the basic wave voltage induced across the reactor. Consequently, reactance can be determined with no consideration on the basic wave voltage drop due to the reactor.

Description

[Detailed Description of the Invention] [Purpose of the Invention (Industrial Application Field) The present invention is directed to suppressing harmonic current flowing out from a load to a power supply system, or suppressing harmonic current flowing into a load from a power supply system. The present invention relates to a harmonic current suppression device for.

(Prior Art) In recent years, as power electronic devices have become widespread in various industrial fields, harmonic currents generated from these devices have leaked into power supply systems, which has become a major problem. As a measure to prevent this harmonic current from flowing into or out of the power supply system, a reactor whose impedance increases in proportion to the frequency is installed at the receiving point of conventional equipment, and this reactor is used to prevent harmonic current from flowing into or out of the power supply system. A method has been used to suppress the inflow and outflow of harmonic current by setting it to a high impedance.

(Problem to be solved by the invention) In this case, since the accelerator installed at the equipment power receiving point has not only harmonic impedance components but also fundamental wave impedance components, the fundamental wave voltage decreases due to the fundamental wave impedance voltage drop. It was not possible to install a reactor with a large enough impedance to suppress the harmonic current.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a harmonic current suppressing device that has sufficiently low impedance for fundamental wave current and high impedance for harmonic current. do.

[Structure of the Invention] (Means for Solving the Problem) In order to achieve the above object, the present invention connects the primary side of a current transformer in series with an electric circuit that supplies power to a load from a power supply system, A voltage source inverter having a reactor and a switching element is connected in series to the secondary side of the current transformer, and the current flowing through the circuit of the reactor and the inverter is detected to detect harmonics from the negative '6:I to the power supply system. remove the current,
Alternatively, a harmonic current removing means for removing harmonic current from the power supply system to the load and outputting the remaining current after removing the harmonic current is provided, and the current output from this harmonic current removing means is inputted, and the A gate pulse generation circuit that is provided with a calculation means for calculating the fundamental wave voltage generated in the reactor, manually inputs the fundamental wave voltage calculated by the calculation means, and generates a voltage in the voltage type generator to offset the fundamental wave voltage. The present invention is characterized in that a switching element of the voltage type inverter circuit is controlled to be turned on or off by a voltage signal from the gate pulse generating circuit.

(Function) According to the configuration of the present invention described above, the harmonic current on the primary side of the current transformer is converted to the secondary side by the current transformer, and the harmonic current is connected to the secondary side of the current transformer, and the , the fundamental wave voltage and the harmonic voltage are induced, or the fundamental wave voltage is canceled by the voltage generated from the voltage source inverter, and the current transformer secondary voltage is induced by the harmonic voltage, and the current transformer secondary voltage is induced by the harmonic voltage. The load on the side becomes only the harmonic component, and in order to save money, the impedance on the primary side of the current transformer becomes only the harmonic impedance. Therefore, the reactance value can be determined without considering the fundamental voltage drop due to the reactor, and the effect of suppressing harmonic current can be increased.

(Example) Hereinafter, an example of the present invention will be described based on FIG. 1. In Fig. 1, power is supplied to a load 1 by an AC power supply 2, the primary winding (primary side) of a current transformer 3 is connected in series to the charging point of the load 1, and the secondary winding of the current transformer 3 is connected in series to the charging point of the load 1. A reactor 4 and a voltage source inverter 5 are connected in series. A circuit 6 for detecting the fundamental wave voltage across the reactor 4
As a current transformer 6A for detecting the secondary current of the current transformer 3 or the current transformer 6A for detecting the current transformer, harmonic current is removed from the current signal detected by this current transformer 6A, and the remaining harmonic current is removed. Harmonic current removal means 6 for controlling the current
B comprises, for example, a calculating means 6C which inputs the output signals of the harmonic current suppressing reactor and the harmonic current removing means 6B and calculates the fundamental wave voltage across the reactor 4.

The gate pulse generation circuit 7 inputs the fundamental wave voltage signal at both ends of the reactor 4, outputs a gate pulse that becomes a voltage that cancels out the fundamental wave voltage, and applies it to the voltage source inverter 5. It is designed to induce a fundamental wave voltage.

Next, the operation of this embodiment configured as described above will be explained with reference to FIG. 1 as well.

First, the fundamental wave of the load current is 11, the harmonic current is 18, the secondary current of the current transformer 3 is 11, and il, i corresponds to IH.
Similarly, assume that the secondary current of the reactor current detecting current transformer 6A is L%+lH. The secondary current i, ', +iH' of the current transformer for reactor current detection is harmonic removal means 6B.
iH' is removed by
(reactance value) and obtain the voltage signal v1' across the handlebar 4. The gate pulse generation circuit 7 has V,
' generates a gate pulse of ¥V and sends it to the voltage type in/<- 5, and the voltage type inverter 5 outputs ¥■
Generates 1. Therefore, the voltage v, +yH of the reactor 4
and the voltage of the voltage type inverter 5, the secondary voltage of the current transformer becomes vH. Current transformer 1 corresponding to the current transformer secondary voltage vH
VH is induced on the next side. The harmonic impedance on the primary side of the current transformer is Vu/IH-IH/n.ωL/IH/n-ωL/n2 (n: current transformation ratio).

[Effects of the Invention] According to the harmonic current suppressing device of the present invention described above, the fundamental wave voltage of the voltage induced across the reactor is canceled out by the voltage generated by the voltage source inverter, so that the fundamental wave voltage due to the reactor is canceled out by the voltage generated by the voltage source inverter. The reactance value can be determined without considering voltage drop, and the effect of suppressing harmonic current can be increased.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention. 1...Load, 2...Power supply, 3...Current transformer, 4...
Reactor, 5... Voltage type inverter, 6... Circuit for detecting the fundamental wave voltage across both ends of the reactor, 6A... Current transformer, 6B... Harmonic current removal means, 6c... Arithmetic means, 7. ...Gate pulse generation circuit. Applicant's agent Patent attorney Takehiko Suzue

Claims (1)

[Scope of Claims] A voltage source inverter in which the primary side of a current transformer is connected in series to an electric circuit that supplies power to a load from a power supply system, and has a reactor and a switching element on the secondary side of the current transformer. are connected in series and detect the current flowing through the circuit of the reactor and the inverter to remove harmonic current from the load to the power supply system, or remove harmonic current from the power supply system to the load, and remove the harmonic current from the power supply system to the load. A harmonic current removing means for outputting a residual current after removing the current is provided, and a calculating means is provided for inputting the current output from the harmonic current removing means and calculating a fundamental voltage generated in the reactor, and this calculation is performed. A gate pulse generation circuit is provided which inputs the fundamental wave voltage calculated by the means and causes the voltage source inverter to generate a voltage that offsets this fundamental wave voltage, and the voltage signal from the gate pulse generation circuit causes the voltage source inverter circuit to A harmonic current control device characterized by controlling on/off of a switching element.