JP2715613B2 - Inverter constant current controller - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a constant current control device for an inverter that controls a current when an electric power converted by an inverter is supplied to a load via a filter circuit according to a current command value. About.

[Conventional technology]

FIG. 5 is a block diagram showing a conventional example of a constant current control device for controlling a current supplied from an inverter to a load via a filter circuit to a predetermined value.

In FIG. 5, an inverter 1 converts power from a power supply (not shown) into AC power having a desired voltage and frequency and supplies the AC power to a load 6. In order to control the actual value I of the current flowing through the load 6 to a constant value, the current detecting means, for example, the shunt 5 detects the actual value I and feeds back the current command value I ^*. Is input to a current controller 7 constituted by a proportional-plus-integral calculator.
Since the current regulator 7 outputs a control signal for making the input deviation zero, the current from the inverter to the load 6 can always be maintained at a predetermined value by giving the control signal to the inverter 1 for control.

The inverter 1 generally has a control method of performing power conversion by pulse width modulation control. In order to suppress a ripple component included in the output of the inverter 1, a filter reactor 2, a braking resistor 3, and a filter capacitor 4 are provided. And the inverter 1
And the load 6. Here, the braking resistor 3 is for suppressing the vibration caused by the filter capacitor 4 and the filter reactor 2 constituting the filter circuit.

[Problems to be solved by the invention]

The inverter 1 performs power conversion by connecting a semiconductor switch element such as a GTO thyristor or a transistor in a bridge, and sequentially turning on and off these semiconductor switch elements. The semiconductor switch element forming the upper arm of the bridge connection is used. If the semiconductor switch elements constituting the lower arm in the same phase as this are simultaneously turned on, a so-called arm short circuit accident occurs.

In order to prevent such an arm short-circuit accident, a dead element is provided by inserting a delay element into the drive signal circuit of the semiconductor switch element, and a period during which both are turned off is provided.

FIG. 6 is a graph showing the input / output characteristics of an inverter having a dead zone. The input and the output are originally in a one-to-one relationship as shown by the broken line, but by providing a dead band width of ε, the nonlinear characteristic shown by the solid line is provided to prevent the occurrence of arm short circuit.

The load 6 is generally an inductive load, a filter circuit shown in FIG. 5 is inserted between the inverter 1 and the load 6, and the inverter 1 has a dead band characteristic shown in FIG. Therefore, when performing constant current control, there is an inconvenience that these dynamic characteristics change in accordance with the current value. Particularly, in a small current region, a satisfactory current response cannot be obtained, so that there is an inconvenience that constant current control becomes difficult.

Therefore, an object of the present invention is to provide an inverter that performs power conversion with a dead zone characteristic and an inverter that operates by inserting a filter circuit between an inductive load and a good current response regardless of the magnitude of the current. Is to do so.

[Means for solving the problem]

To achieve the above object, the constant current control device of the present invention includes an inverter that performs power conversion by providing a dead zone between the operation of the upper arm and the operation of the lower arm in order to prevent an arm short circuit, An inductive load receiving power supply from the inverter, a filter reactor and a filter capacitor connected between the inverter and the load, and a voltage command for matching an actual current value flowing through the load to a current command value. A constant current control device for an inverter having a current adjusting means for outputting a value and supplying the voltage command value to the inverter. A state observer that outputs a simulated value of the actual current value and its first and second derivatives, and the output of the current adjusting means. And a response model circuit that outputs a model current that determines the time response of the current and its first and second derivatives, a current simulation value output by the state observer, and a model current output by the response model circuit. A first addition / subtraction element for calculating the deviation of the current, a second addition / subtraction element for calculating the deviation between the primary differential value of the output current simulated value and the primary differential value of the model current, and the current simulated value output by these as well. A third addition / subtraction element for calculating the deviation between the second derivative of the model current and the second derivative of the model current, and first and second elements for multiplying the outputs of the first, second and third addition / subtraction elements by separate proportional gains. A second and third proportional element, a fourth adder / subtractor for mutually adding and subtracting the outputs of the first, second and third proportional elements, and an output of the fourth adder / subtractor are multiplied by a proportional gain, and the multiplication result is obtained. No. to output to outside A dynamic compensating circuit comprising a proportional element and a signal adder / subtractor for inputting a result obtained by adding and subtracting an output of the dynamic compensating circuit and an output of the current adjusting means to the inverter as a voltage command value; I do.

[Action]

According to the present invention, a response model circuit for providing a target of a current response is provided. The response model circuit outputs the response target current and its first and second derivative values, while simultaneously outputting a voltage command value to an inverter. A state observer for inputting the actual value of the current to the load is provided, and the state observer outputs a simulated value of the actual value of the current and its first and second derivatives. Therefore, the currents output from each of the response model circuit and the state observer, the primary differential values thereof, and the secondary differential values thereof are separately compared to obtain the deviation, and each deviation is multiplied by a predetermined number. Are added to each other, and the amplified result is added to the output of the current regulator to give a new voltage command value to the inverter.

With this configuration, if there is a difference in response between the response model and the actual state quantity, this is amplified and immediately corrected, so that the actual current value is controlled to match the dynamic characteristics of the response model. Therefore, the dead zone provided for preventing the short circuit of the arm is also apparently small.

〔Example〕

FIG. 1 is a block diagram showing an embodiment of the present invention.

In FIG. 1, the inverter 1, the filter reactor 2, the filter capacitor 4, the shunt 5, the inductive load 6, and the current regulator 7 are the same as those of the conventional circuit described in FIG. Since the functions are the same, their description is omitted.

In the present invention, a dynamic compensation circuit 8 is provided, and the output V of the current regulator 7, the actual value I of the current flowing through the load 6, and the voltage command value U inputted to the inverter 1 are inputted to the dynamic compensation circuit 8. since it is, if there is a difference in response between the actual state amount and response model, which is outputted from the dynamic compensation circuit 8 as the amplified signal U _C.

Therefore, in the signal subtractor 9, is addition output U _C is from this dynamic compensation circuit 8 to the output V of the current regulator 7, since the addition result is supplied to the inverter 1 becomes the voltage command value U, the current response Can be quickly corrected.

FIG. 2 is a block diagram showing the configuration of the dynamic compensation circuit 8 used in the embodiment circuit shown in FIG.

In FIG. 2, the state observer 20 detects the current actual value I
And the current command value U, the simulated value of the actual current value (ie, ₁ ) and its first derivative d / dt (ie,
₂ ) and the second derivative d ² / dt ² (that is, ₃ ) are output.

On the other hand, the response model circuit 50 for determining the time response of the current receives the signal V from the current regulator 7 and outputs the current I ^* (ie, X ₁ ^* ) as the time response target and its first derivative (dI / d
t) ^* (ie, X ₂ ^* ) and second derivative (d ² I / dt ² )
^* (That is, X ₃ ^* ) is output.

Therefore, the first addition / subtraction element 11 compares the current ₁ with X ₁ ^* to determine the deviation, and the first proportional element 15 calculates the deviation f ₀
Multiply. Similarly, the second addition / subtraction element 12 is a first derivative of the current.
₂ and X ₂ ^*, and the second proportional element 16 multiplies the difference by f ₁ . The third addition / subtraction element 13 calculates the deviation between each of the second derivative values ₃ of the current and X ₃ ^*, and the third proportional element 17 multiplies the deviation by f ₂ .

The fourth adding / subtracting element 14 is used for the first, second and third
Mutually adding the output of the proportional element 15, 16, 17 with a negative polarity, multiplies K the addition result in the fourth proportional element 18, and the result with the output U _C of the dynamic compensation circuit 8. That is, the second
The dynamic compensation circuit 8 shown in the figure performs the calculation of the following equation (1).

FIG. 3 is a block diagram showing the configuration of the state observer 20 used in the dynamic compensation circuit of FIG.

As shown in FIG. 3, the state observer 20 has three sets of integral elements 21, 22, and 23, one set of non-linear elements 24, and seven sets of coefficient elements 25, 26, 27, 28, 29, and 30. , 31 (The coefficient for multiplying the input by a predetermined number is
B, k ₁ , k ₂ , k ₃ , A ₀ , A ₁ , A ₂ ) and six sets of addition / subtraction elements 41, 42, 43, 44, 45, 46. The simulated value _{1 of the} actual current value is obtained from the integration element 21, the second integration element 22 obtains its primary differential value ₂ , and the third integration element 23 obtains its simulated value 2.
The next differential value ₃ is output.

The non-linear element 24 simulates the dead band characteristic of the inverter 1 by outputting a dead band characteristic having a dead band width of ε as shown in FIG.

In the circuit shown in FIG. 1 described above, V ₁ ... The input voltage of the filter circuit, V ₂ ... The voltage of the load 6, I ₁ ... The current of the filter reactor 2, I ₂ . actual current flowing to 6, the resistance of the R ... load 6, the resistance of the R ₁ ... filter reactor 2, when the S ... Laplace operator, voltage and current of the load 6 and the filter circuit of the circuit shown in FIG. 1 The relationship of (2), (3),
Equations (4) and (5) are obtained.

And a suffix of 100 indicates a rated value. L is the inductance of the load 6, L _{1 is} the inductance of the filter reactor 2, and C is the capacitance of the filter capacitor 4.

Therefore these (2) to (5) the relationship between the current actual value I and the filter circuit input voltages V ₁ from the equation becomes as follows (6).

Wherein the coefficient of the first coefficient element 25 B, the coefficient A ₀ of the fifth coefficient element 29, the coefficient A ₁ and seventh coefficient element 31 of the sixth coefficient element 30
The value of the coefficient A ₂ of (7), (8), (9),
It takes the value shown in equation (10).

The coefficient k ₁ of the second coefficient element 26, the value of the coefficient k ₃ coefficient k ₂ and the fourth coefficient elements 28 of the third coefficient element 27, is stably and tracking of the current actual value I of the current simulated value It shall be determined to be performed promptly. At this time, each integral element 21,2
The outputs ₁ , ₂ , and ₃ of ₂ , 23, respectively, are proportional to the simulated current value and its first and second derivative values, respectively, as shown in equation (11).

FIG. 4 is a block diagram showing a configuration of a response model circuit 50 used in the dynamic compensation circuit of FIG.

As shown in FIG. 4, the response model circuit 50 has three sets of integral elements 51, 52, 53 and four sets of coefficient elements 54, 55, 56, 57 (the coefficients for multiplying the input by a predetermined number are β _0, respectively). , α ₀ , α ₁ , α ₂ ) and three sets of addition / subtraction elements 61, 62, 63. By inputting the output V of the current regulator 7 shown in FIG. an input voltage V ₁ of the circuit, defines the response of the current actual value I for this. Therefore, there is a relationship shown in equation (12) between the two.

Here, the coefficient α ₀ of the ninth coefficient element 55 and the tenth coefficient element 56
And coefficient alpha ₂ of the coefficient alpha ₁ and 11 coefficient element 57, be selected in the relationship shown in the following equation (13), the response of the Butterworth filter.

When the dead zone width is ε, the following expression (14) is obtained from the dead zone characteristics shown in FIG.

U = V + ε (14) Equation (15) is obtained from equation (14). By modifying equation (15), equation (16) and equation (17) are obtained.

Therefore, if K is selected to be a large value, the second on the right side of the equation (17)
Since the term becomes zero or a value close to zero, the influence of the dead zone ε can be eliminated. At the same time, the first term on the right side of equation (17) is V ·
Since K approaches D (S) / D _m (S), the above equation (17) becomes the following equation (18) by approaching K to infinity.

Therefore, the following equation (19) is obtained, which approaches the model response.

Thus, the non-linearity of the inverter 1 is suppressed, and the current response of the inverter 1 to the voltage command approximates the response determined by the model response. What is necessary is just to adjust it considering it as a target.

〔The invention's effect〕

According to the present invention, a current simulation value, a first derivative value and a second derivative value thereof are obtained from a filter circuit and a state observer for estimating a state of the load in a circuit that supplies power converted by the inverter to the load via the filter circuit. On the other hand, the current, its primary differential value and its secondary differential value are extracted from a response model circuit that determines the response of the current to the voltage command of the inverter, and the currents of the two, the primary differential values, and the secondary differential values are extracted. Amplify the deviation of both obtained by comparing each other separately,
The circuit is configured so that the sum obtained by adding the sum to the output of the current regulator is given to the inverter as a voltage command value. Therefore, the dead zone characteristic of the inverter is suppressed and linearized. Further, the oscillation characteristic of the filter circuit for suppressing the ripple component included in the inverter output is also suppressed, so that the effect of obtaining a good current response regardless of the magnitude of the current value is exhibited. Therefore, good constant current characteristics can be obtained even in a small current region. Further, since the filter circuit can suppress the vibration characteristics even if the braking resistor is removed, the filter circuit also has the effect of avoiding disadvantages due to the braking resistor, for example, an increase in loss and accompanying heat generation and a decrease in the ripple suppression effect.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.
FIG. 3 is a block diagram showing the configuration of a dynamic compensation circuit used in the embodiment circuit shown in FIG. 1. FIG. 3 is a block diagram showing the configuration of a state observer used in the dynamic compensation circuit of FIG. FIG. 4 is a block diagram showing a configuration of a response model circuit used in the dynamic compensation circuit of FIG. 2,
FIG. 5 is a block diagram showing a conventional example of a constant current control device for controlling a current supplied from an inverter to a load via a filter circuit to a predetermined value, and FIG. 6 shows input / output characteristics of an inverter having a dead zone. It is a graph. 1 ... Inverter 2 ... Filter reactor 3 ...
Braking resistance, 4 ... Filter capacitor, 5 ... Shunt,
6 ... Load, 7 ... Current regulator, 8 ... Dynamic compensation circuit,
9 ... Signal adder / subtracter, 11, 12, 13, 14, 41, 42, 43, 44, 45, 46,
61,62,63 …… Addition / subtraction element, 15,16,17,18 …… Proportional element, 2
0 …… State observer, 21,22,23,51,52,53 …… Integral element, 24
…… non-linear elements, 25,26,27,28,29,30,31,54,55,56,57…
... coefficient element, 50 ... response model circuit.

Claims (2)

(57) [Claims] An inverter for performing power conversion by providing a dead zone between the operation of an upper arm and the operation of a lower arm to prevent a short circuit of an arm, and an inductive load receiving power supply from the inverter. A filter reactor and a filter capacitor connected between the inverter and the load, and a voltage command value for matching the actual value of the current flowing through the load to the current command value, and outputting the voltage command value as In a constant current control device for an inverter, comprising a current adjusting means for giving an inverter, a current actual value flowing to the load and a voltage command value given to the inverter are inputted to simulate a current actual value, A state observer that outputs a second derivative value and a second derivative value,
A response model circuit that receives the output of the current adjusting means and outputs a model current that determines the time response of the current, and its first and second derivatives, a current simulation value and a response that the state observer outputs A first addition / subtraction element for calculating a deviation from a model current output from the model circuit, a second addition / subtraction element for calculating a deviation between a first derivative of a model model current and a first derivative of the model current output from the model circuit, Similarly, a third addition / subtraction element for calculating a deviation between a second derivative value of the current simulation value output from the above and a second derivative value of the model current;
A first, a second, and a third proportional element for multiplying the output of the third adder / subtractor element by a separate proportional gain, and a fourth adder / subtractor element for mutually adding and subtracting the outputs of the first, second, and third proportional elements. A dynamic compensation circuit is formed by multiplying the output of the fourth addition / subtraction element by a proportional gain and outputting the result of the multiplication to the outside. The result of addition and subtraction with the output is
A constant current control device for an inverter, comprising: a signal adder / subtractor that inputs the voltage command value to the inverter. 2. An inverter for performing power conversion by providing a dead zone between the operation of the upper arm and the operation of the lower arm to prevent a short circuit of the arm, and an inductive load receiving power supply from the inverter. A filter reactor and a filter capacitor connected between the inverter and the load, and a voltage command value for matching the actual value of the current flowing through the load to the current command value, and outputting the voltage command value as In a constant current control device for an inverter, comprising a current adjusting means provided to an inverter, a dynamic compensation circuit for inputting an output of the current adjusting means and an actual current 4 and a voltage command value is provided. The state observer, which is a component of the above, has a first integral element that outputs a simulated value of the actual current value, a second integral element that outputs a first derivative of the simulated current value, and A third integral element for outputting a second derivative value of the current simulation value, a first coefficient element for multiplying the output of the first integral element by a predetermined number, and an actual current value of the current and an output of the first coefficient element. A fifth addition / subtraction element for calculating the deviation, and second and third elements for separately multiplying the output of the fifth addition / subtraction element by a predetermined number.
And a fourth coefficient element and the first, second and third coefficients
A fifth, a sixth, and a seventh coefficient element for separately multiplying the output of the integral element by a predetermined number; a non-linear element for inputting the voltage command value and outputting the characteristic of the dead zone for preventing an arm short circuit;
A sixth addition / subtraction element for adding / subtracting the output of the fifth coefficient element and the output of the sixth coefficient element, a seventh addition / subtraction element for adding / subtracting the output of the sixth addition / subtraction element and the output of the seventh coefficient element, An eighth addition / subtraction element for inputting the result of addition / subtraction between the output of the second integration element and the output of the second coefficient element to the first integration element, and the addition / subtraction result of the output of the third integration element and the output of the third coefficient element Is input to the second integration element, and the result of mutually adding and subtracting the output of the nonlinear element, the output of the fourth coefficient element, and the output of the seventh addition / subtraction element is input to the third integration element. A response model circuit comprising a tenth addition / subtraction element, and being a component of the dynamic compensation circuit, a fourth integration element for outputting a model current that determines a time response of the current, and a first derivative of the model current Output the value and The output of the fifth integrator element that is input into the fourth integral element, the second derivative of the model current,
And a sixth integral element for inputting this to the fifth integral element and an eighth integral for separately multiplying the output of the fourth integral element by a predetermined number.
A ninth coefficient element, a tenth coefficient element for multiplying the output of the fifth integration element by a predetermined number, an eleventh coefficient element for multiplying the output of the sixth integration element by a predetermined number, and an output of the ninth coefficient element An eleventh addition / subtraction element for adding and subtracting the output of the tenth coefficient element and a twelfth addition / subtraction element for adding / subtracting the output of the eleventh addition / subtraction element and the output of the eleventh coefficient element, A constant current control device for an inverter, comprising: a thirteenth addition / subtraction element for inputting a result of addition / subtraction with an output of the current adjusting means to the sixth integration element.