JPS5947553B2 - Current control device in cycloconverter - Google Patents

Description

Detailed Description of the Invention The present invention provides a cycloconverter that supplies a multiphase load current to a load without connecting the neutral point of the load and the neutral point of the cycloconverter. This invention relates to a current control device for matching the current value.

Hereinafter, three-phase AC will be explained as an example of polyphase AC. When supplying load current from a cycloconverter to a three-phase alternating current machine, there are cases where the load current is supplied without connecting the neutral point of the load and the neutral point of the converter. This is the case, for example, when it is impossible to extract the neutral point of the load to the outside, or when it is not desired to flow a zero-sequence current. An example of disconnecting the neutral point on the load side and the neutral point on the cycloconverter side in order to prevent zero-sequence current from flowing is to control the output voltage waveform of the converter so that it has a trapezoidal wave-like time transition characteristic. , a case where the ratio of the converter's output voltage fundamental wave effective value to the output voltage maximum value is made larger than when the converter's output voltage waveform is controlled to have a sinusoidal time-varying characteristic. In this case, if the three-phase output voltage of the converter includes a zero-sequence component and the load-side neutral point and converter-side neutral point are connected, a large zero-sequence current determined by the load resistance will flow. Generally, the load side neutral point and the converter side neutral point are not connected. In this case,
It is already known that even though the output voltage of the converter has a trapezoidal waveform, the line voltage of the load remains approximately sinusoidal, and each phase current also has an approximately sinusoidal waveform. Now, in a cycloconverter that supplies load current to the load without connecting the load-side neutral point and the converter-side neutral point, current control is carried out to make the actual value of the load current match the command value. If you do this, a problem will arise.

This problem will be explained next with reference to FIG.
FIG. 1 is a block diagram showing an example of the configuration of a conventional current control device in a cycloconverter.

In the figure, 1a to 1c are current regulators for each phase, and 2 is a voltage shaping circuit. Current controller 1a~
1c is provided corresponding to each phase, and indicates the actual values 1a, ib, i0 and command values 1a*, Ib, I of the current supplied to the load from the cycloconverter (not shown).
The amount of difference from O (indicates that the value is the command value) is input, and the adjustment outputs Ea*, Eb,
It outputs Ec and supplies it to the voltage shaping circuit 2. When the voltage shaping circuit 2 makes the output voltage into a trapezoidal waveform,
It is provided as necessary. Here, the current regulators 1a to 1c are generally used in order to speed up the response of the control system and eliminate steady-state deviation of the control amount especially at low frequencies.
In addition to proportional operation (P operation), it also has the function of integral operation (I operation). Now, the current command value is 1a, I
If the zero-phase component is included non-theoretically due to a calculation error, if the neutral point on the load side and the neutral point on the converter side are not connected, the line connecting the neutral points Therefore, since the zero-sequence current cannot flow, at least one of the three-phase current regulators 1a to 1c integrates the zero-sequence current command value. There was a problem that it could become saturated and become uncontrollable. This invention has been made in order to solve the problems in the prior art as described above, and an object of the invention is to solve the problems in the prior art as described above, and therefore, an object of the invention is to solve the problems in the prior art as described above. In a cycloconverter that supplies a load current, each multiphase current regulator constantly controls the current of each phase without integrating the zero-sequence current command value and therefore without becoming saturated. We present a current control device that makes it possible.

It is about providing. The above-mentioned problems in the conventional technology are as follows.
This is due to the fact that a three-phase current regulator with I operation is used to control load current including zero-sequence current.

By the way, the three-phase alternating current can be calculated by coordinate transformation, for example, α, which stands on the same axis as the a phase 4 ((one of the three phases)).
It can be decomposed into an axial component, a β-axis component perpendicular to it, and a zero-phase component. The vector relationships among these quantities are shown in the vector diagram of FIG. 2, so please refer to it. Therefore 3
If only the α-axis component current and the β-axis component current obtained by coordinate transformation of the phase current flow are controlled by a current regulator with operation, the zero-sequence current will not be integrated.
The above-mentioned problems in the prior art can be solved. The main points of the configuration of this invention are as mentioned above. Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 3 is a block diagram showing one embodiment of the present invention. In the figure, 11a to 11c are current regulators with P operation, and 12a and 12b are I, respectively.
This is a current regulator that is an actuated regulator. 13a, 13
b are 3-phase/2-phase coordinate converters, and 13a is a 3-phase/2-phase coordinate converter.
The phase current command value (from Ia* to Ic) is converted to the two-phase current command value (
13b is the three-phase current actual value (Ia-10
) is converted into two-phase actual current values (Ia, lβ).

The arithmetic expression for the conversion is given by the following equation. Note that the zero-sequence current is given by the following equation. Reference numeral 14 denotes a two-phase/three-phase coordinate converter, which performs the inverse calculation of the three-phase/two-phase coordinate converter 13a or 13b, and its calculation formula is given by the following equation.

Reference numeral 15 denotes a voltage shaping circuit, which is provided as necessary when obtaining a trapezoidal waveform voltage, and is provided as needed to obtain a desired trapezoidal waveform voltage command value Ea.
*5 to EO rice 5 obtained.

A feature of the present invention is that regulators 11a to 11c with P operation are used for each of the three-phase current regulators, and the three-phase currents are controlled by these regulators, and the current command values and actual values of the three-phase quantities are transferred to the coordinate converter 13a, 13b calculates α-axis and β-axis current components that do not include zero-phase components, and two-phase current control is performed for these using regulators 12a and 12b with I operation. The outputs Ea and eβ of the regulators 12a and 12b with I action are inversely transformed by the 2-phase/3-phase coordinate converter 14, and the resulting outputs Ea and Ect and the regulator with P action Ila Each output signal of Ilc is Al. ~ECl.
The voltage command values Ea to Ec are obtained by adding the voltage command values Ea to Ec. In this embodiment, even if the sinusoidal current command values Ia to 1c include non-theoretical zero-phase components, since the three-phase current regulators Ila to Ilc are regulators with P operation,
The zero-sequence current command value is never integrated, so the regulator never becomes saturated. Furthermore, in order to speed up the response of the control system and eliminate steady-state deviation of the controlled variable, especially at low frequencies, 3.
Convert the phase current to an αβ two-phase amount that does not include the zero phase component, and
A regulator with I action is provided for the phase quantity, and in this case, no control is applied to the zero-sequence current, so saturation of the regulator due to the integration of the non-theoretical zero-sequence current command value does not occur. .

FIG. 4 is a block diagram showing another embodiment of the invention.

In the figure, the current command value is given in polar coordinate format. That is, the magnitude of the current K is given by the current level setter 10, and the frequency is a mutually orthogonal signal SinωT, cOsO)t(ω; angular frequency,
t; time). The current command calculator 16 is
A three-phase current command value is calculated and output from the above-mentioned K, sinωT, and cOsωt.

This has a basic configuration of a two-phase/three-phase coordinate converter, and its calculation formula is given by the following equation. Once the three-phase current command value is determined here, the subsequent circuit can have a circuit configuration similar to that shown in FIG. 3, but here a different system will be shown. In other words, the two-phase currents Ia, iβ are αβ/
When the currents obtained by coordinate transformation by the Dq coordinate converter IT are defined as d-axis current (Id) and q-axis current (1q),
The configuration is such that Id and iq are controlled by I-operated droplet regulators 12a and 12b. Next, this αβ/Dq coordinate transformation will be explained. The d-q coordinate axes are a coordinate system rotating with respect to the α-β coordinate axes at an angular frequency ω that is the same as the angular frequency of the current. A vector diagram of the coordinate system is shown in FIG. 5, so please refer to it. Therefore, the currents Id and iq observed from the newly assumed dh axis are given by the following equations by known coordinate transformation. In equation (5)...equation and (4
In other words, Id and iq become DC amounts.

Also, ψ can be selected to any value, so if ψ = 0, I
, d2K, iq=0, and according to the following equation (8), αβ/
Dq coordinate transformation is performed. Also at this time, the d axis and q
The axis current command values are K and O, respectively.

As mentioned above, in the configuration example shown in FIG. 4, Id and iq are DC amounts, so the second advantage is that the steady state deviation is completely eliminated by the integral operation of the two-axis current regulators 12a and 12b. The illustrated embodiment is also included.

The explanation of the other operations is the same as that shown in FIG. 3, so no further explanation will be given. As explained above, according to the present invention, when a multiphase load current is supplied from a cycloconverter to a load without connecting the neutral point on the load side and the neutral point on the cycloconverter side, the multiphase load current This has the advantage that stable adjustment and control of the load current can be realized by PI operation without being affected by the zero-sequence current that appears in the current.

In addition, in this invention, when the two-phase current obtained by converting the number of phases of the multi-phase AC that is the load current is further converted into a DC flow rate, the steady-state deviation of the controlled variable can be removed by the regulator with I operation. In this case, even when the load side neutral point and the cycloconverter side neutral point are connected, this can be used as an effective means. Note that this invention is applicable not only to alternating current machines, but also to L-R machines, for example.
Of course, this method can also be applied to general loads such as loads (where L represents inductance and R represents resistance) when the neutral point on the load side and the neutral point on the cycloconverter side are not connected. .

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a configuration example of a conventional current control device in a cycloconverter, and FIG. 2 is a vector diagram showing the vector relationship of each AC amount when converting a three-phase AC amount into a two-phase AC amount. FIG. 3 is a block diagram showing one embodiment of the present invention, FIG. 4 is a block diagram showing another embodiment of the invention, and FIG. 5 is a phase diagram of the dq coordinate system with respect to the α-β coordinate axis It is a vector diagram showing the relationship. Explanation of symbols, 1...Current regulator, 2...
Voltage shaping circuit, 10...Current level setting device, 1
1...Current regulator with P operation, 12...
・Current regulator with I operation, 13...3-phase/2-phase coordinate converter, 14...2-phase/3-phase coordinate converter,
15... Voltage shaping circuit, 16... Current command calculator, 17... αβ/Dq coordinate converter.

Claims (1)

[Claims] 1. In a cycloconverter that supplies a multiphase load current to a load without connecting the neutral point of the load and the neutral point of the cycloconverter, the load current is made to match a current command value. A current controller with a proportional action that receives the difference between the actual value and the command value of the multiphase load current and produces a regulating output in the direction where the difference becomes zero.
(hereinafter referred to as the first regulator), a phase number converter that converts the multiphase load currents representing the actual value and the command value, respectively, into two-phase currents, and the actual value of the load current that has been converted into the two-phase number of phases. a current regulator with an integral action (hereinafter referred to as a second regulator) that receives the difference between the input value and the command value and generates a regulating output in a direction in which the difference becomes zero; and each of the first and second regulators. 1. A current control device for a cycloconverter, comprising: an adder that adds the regulated outputs of the cycloconverters and supplies the addition result to the cycloconverter again as a regulated output. 2. The current control device according to claim 1, further comprising means for converting the actual value and command value of the load current whose phase number has been converted into two phases into a DC amount. Current control device in converter.