JPH0748952B2 - Power converter controller - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to improvement of a control device for a power conversion device, and in particular,
The present invention relates to an improvement of a control device equipped with a phase shifter that obtains a firing angle signal by digital calculation using a microcomputer.

[Background of the Invention]

2. Description of the Related Art A control device of a power conversion device, in particular, a phase control unit is digitized by using a microcomputer or the like.

The basic idea is described in, for example, JP-A-58-93465, JP-A-58-204762, JP-A-58-224556 and JP-A-57-170066. (1) Capture of control target value (2) Capture of feedback amount (3) Calculation of deviation between target value and feedback amount, and (4) Generation of timing signal at firing angle corresponding to this deviation. Steps are needed.

Here, the responsiveness greatly changes depending on when the steps (1) to (3) are performed and when the output is used. In each of the above publications, the procedure of (4) above is executed by the counter from the zero cross point of the AC power supply voltage. Therefore, the above (1) to (() used to generate the timing signal in this half cycle are used. The procedure of 3) is executed at least before the start of the corresponding half cycle, and the firing angle for the execution of the procedure of (4) in the half cycle is preset.

Specifically, it is not possible to capture the voltage value or current value that is the feedback amount used for control, and to calculate the firing angle of the thyristor based on this feedback amount at the same time in time. , It is necessary to perform the calculation sequentially, and it takes half a cycle of the AC power supply to capture the feedback amount.
The calculation result is set in the phase shifter at the end of the half cycle in which the calculation is performed, and the phase control based on this calculation result is performed in the next half cycle after the half cycle in which the calculation is performed. It takes at least one cycle for the fluctuation of the above to be reflected in the output of the bridge circuit.

The time required for this one cycle becomes dead time for control,
This has been a cause of impairing the control response characteristics of the control device.

On the other hand, in an analog type control device using an operational amplifier which has been conventionally prized, since the feedback amount can be captured and the firing angle of the thyristor based on this feedback amount can be calculated at the same time, It is possible to obtain ideal response characteristics.

[Object of the Invention]

An object of the present invention is to provide a control device of a power conversion device using a digital arithmetic means using a micro computer or the like, which has good control response characteristics.

[Outline of Invention]

A feature of the present invention is that in a control device for a power converter that connects a single-phase alternating current circuit and a direct current circuit, in synchronization with each half cycle of the alternating current side voltage, the initial value of the feedback amount is taken in and the target value and The digital calculation of the ignition angle including the calculation of the deviation of the feedback amount is executed once, and the calculated ignition angle data is set once as the data for generating the ignition timing signal in the half cycle. Is.

Example of Invention

An embodiment of the present invention will be described in detail below with reference to the drawings.

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

In FIG. 1, the target value setter 1 sets the current value to be passed through the DC load 2. The microcomputer 3 determines the firing angle by taking the deviation between the output of the target value setting device 1 and the feedback amount of the current flowing through the load obtained from the load current detector 4. Mixed bridge circuit 5 constituting a power converter
Performs the phase control by driving the gate circuits 61 and 62 by the firing angle, which is the output of the microcomputer 3. Through the above operation, the voltage / current control device controls the load current so as to match the predetermined current. Reference numeral 7 is an AC power supply, and 8 is a comparator for detecting the zero cross point of the voltage.

The microcomputer 3 includes a central processing unit CPU and a memory unit M.
An EM, an interrupt control unit OIC, an analog input unit AI, and gate output units GSO1 and GSO2 are provided.

The analog input section AI takes in the target value and the feedback amount by performing analog-digital conversion on the output of the target value setter 1 and the output of the load current detector 4. Gate output section
The GSO outputs a firing signal to the thyristors 51 and 52 of the bridge circuit 5 in a phase corresponding to the firing angle data set by the central processing unit CPU. The interrupt controller OIC is an AC power supply 7
A signal obtained by waveform-shaping the voltage waveform of 1 is input by the comparator 8, and the microcomputer 3 detects the start time point (zero cross point) of each half cycle of the AC power supply 7.

FIG. 2 is a flowchart of a program to be executed by the microcomputer 3 shown in FIG.

The program shown in FIG. 2 is the microcomputer 3
It is activated at the start point of each half cycle of the AC power supply 7 detected by the interrupt control unit OIC. In steps 1 and 2, the central processing unit CPU fetches the target value and the feedback amount from the analog input unit AI. In step 3, the deviation amount between the target value and the feedback amount is calculated. In step 4, the firing angle is calculated from the deviation amount. Step 5
In the half cycle starting from the time when the program of FIG. 2 is started, a numerical value corresponding to the firing angle is set in the gate output section (firing angle counter) GSO.

FIG. 3 is a waveform diagram for explaining the operation of the program shown in FIG.

In FIG. 3, the program shown in FIG. 2 is started at the starting point of each half cycle of the AC power supply. Steps 1 and 2 of FIG. 2 are executed for the feedback T ₁ , and the target value and the feedback amount are fetched. Steps 3 and 4 are executed for the feedback T ₂ , and the firing angle is calculated from the target value and the feedback amount. Step 5 is executed for the feedback T _3, and the firing angle is set at the gate output GSO. The gate output unit GSO outputs a firing signal to the thyristor at an arbitrary point in the period T ₄ according to the set firing angle. In addition, the output part
Although shown separately for GSO1 and GSO2, the output of the common counter is
It may be distributed for each positive and negative half cycle of the AC power supply voltage.

By the firing angle calculation procedure described above, the feedback amount as a result of control in a certain half cycle is reflected in the firing angle of the thyristor in the half cycle immediately after that, and the dead time of the control system is shortened. Therefore, it becomes possible to improve the control response characteristic.

In the firing angle calculation procedure described above, the thyristor cannot be fired before the period T _{4 in} FIG. That is, during the period T ₁ , the period T ₂ , and the period T ₃ required for the firing angle calculation, the thyristor cannot fire, so that the output voltage of the bridge circuit 5 may decrease.

By the way, when the thyristors 51 and 52 of the mixed bridge circuit 5 shown in FIG. 1 are ignited at any time point of the period T ₄ shown in FIG. 3, the next half cycle of the thyristor is ignited. It is always extinguished by the commutation of the power supply at the starting point of. For example, when the AC power supply 7 is in the polarity shown and current flows through the circuit of the thyristor 51 → the load 2 → the diode 54 → the AC power supply 7, if the voltage of the power supply 7 is reversed, 7 → 53 → 51 → 7.
In this circuit, the thyristor 51 is reverse-biased, and the load current flows back through the circuit of 2 → 54 → 53 → 2. Therefore, unlike power converters of other configurations, thyristor series,
Only in the case of a mixed bridge of the form shown in the series with diodes, there is always a commutation of the thyristor when the supply voltage is reversed.
At this time, the thyristor will extinguish after the commutation overlap period T _AC from the beginning of the half cycle. During this commutation overlap period T _AC , there is no output voltage from the bridge circuit, and phase control of the thyristor cannot be originally performed. Therefore, if the firing angle of the thyristor is calculated within the commutation overlap period T _{AC that} occurs only at the fixed time, the drop in the output voltage of the bridge circuit due to the time required for the calculation can be avoided.

FIG. 4 is a waveform diagram for explaining the operation showing another embodiment of the present invention utilizing the above principle. The difference from FIG. 3 is that the program shown in FIG. 2 is executed within the commutation overlap period T _AC . According to the present embodiment, it is possible to improve the control response characteristic without reducing the output voltage of the bridge circuit.

FIG. 5 is a flow chart showing still another embodiment of the present invention. The difference from FIG. 2 is that in step 6,
Confirm the magnitude relationship between the calculated firing angle α and the planned widths T _{1 to} T _3, and if it is large, that is, if firing can be performed after T _{1 to} T ₃ , then the relevant half is the same as in FIG. Set the firing angle for firing in the cycle. On the other hand, the calculated ignition delay angle α
However, if it is narrower than the full width of the scheduled period T _{1 to} T ₃ , in order to immediately start firing by setting the firing angle as it is in period T ₃ and to recover the decrease of the output voltage due to this immediately, The firing angle calculated in the half cycle is preset as the firing angle signal in the next half cycle.

The result will be described with reference to FIG.

Now, in the first half cycle, the firing angle (represented by the delay angle) calculated up to step 4 in the period T _{1 to} T ₂ is α ₁ (α ₁ > T _{1 to} T ₃ ). Suppose In this case, the determination result of step 6 is "NO", and in step 5,
As the firing angle data for firing in the half cycle, "count value equivalent to α ₁ " is displayed in the gate output unit GSO1.
Is set. (Period T ₃₎ Supporting connexion, thyristor 51 will be fired at the control delay angle alpha _1.

Next, if the calculation result in the second half cycle is α
₂ (α ₂ <T _{1 to} T ₃ <α ₁ ). But the period T ₁
After ~ T ₃ , even if this firing angle α ₂ is set, it is no longer α ₂
It is impossible to fire at, and the firing angle α can only be T _{1 to} T ₃ .

In this case, in the second half cycle, the output voltage decreases by α−α ₂ . In order to recover this early, the firing angle α ₂ of the above calculation result is set to
Reflected in the half cycle of.

That is, in step 7, the count value corresponding to the firing angle α ₂ is preset to the gate output section GSO2.

Now, moving to the third half cycle, in this half cycle also, the calculation of the firing angle α ₃ is performed during the period T _{1 to} T ₂ , but in any case, the result is available for the period T ₄
There is nothing. However, the gate output unit GSO2 outputs the ignition timing signal to the gate circuit 62 at the time of the angle α ₂ after the start of the third half cycle since the ignition angle α ₂ has been preset. Therefore, the thyristor 52 has a firing angle α
Fired at ₂ .

In this way, the delay of the response can be improved even in the special state, and the quick response can always be obtained in the other states.

〔The invention's effect〕

According to the present invention, it is possible to provide a control device for a power converter in which a dead time of a control system is shortened and a control response characteristic is improved.

[Brief description of drawings]

FIG. 1 is a control block diagram of a control device for an electric power converter according to an embodiment of the present invention, FIG. 2 is a flow chart showing an example of a program of the microcomputer, and FIGS. 3 and 4 show the present invention. FIG. 5 is a waveform chart for explaining the operation, FIG. 5 is a flow chart of a program showing another embodiment of the present invention, and FIG. 6 is a waveform chart for explaining the operation. 1 ... Target value setter, 2 ... DC load (DC motor),
3 ... Calculation unit (microcomputer), 4 ... Current detector, 5 ... Power converter, 61, 62 ... Gate circuit, 7 ...
…AC source.

Claims (5)

[Claims] 1. A power converter including a plurality of thyristors connected between a single-phase AC circuit and a DC circuit, a gate circuit for supplying a gate signal to the thyristors of the power converter, and the gate for the gate circuit. And a digital phase shifter for providing a timing signal to generate a signal, the digital phase shifter being synchronized with each half cycle of the voltage of the AC circuit, at a desired time, to capture and target a feedback amount. Means for executing once the digital calculation of the firing angle including the calculation of the deviation amount between the value and the feedback amount, and the calculated firing angle data as the timing signal generation data in the half cycle. A control device for a power converter having a means for setting times. 2. The power converter according to claim 1, wherein the digital phase shifter comprises means for setting the calculated ignition angle data as the timing signal generating data in the half cycle and the next half cycle. Control device. 3. A mixed bridge type power converter connected between a single-phase AC power source and a DC load, one arm of which is a series body of thyristors and the other arm of which is a series body of diodes, and a power converter of this power converter. In a device provided with a gate circuit for supplying a gate signal to a thyristor and a digital phase shifter for giving a timing signal for generating the gate signal to the gate circuit, the digital phase shifter is provided with the AC power supply voltage. A means for executing once a digital calculation of the firing angle including the calculation of the deviation amount between the target value and the feedback amount within the initial scheduled period in synchronization with each half cycle, and the calculation. The generated firing angle data is used as the timing signal generating data in the half cycle concerned.
A control device for a power converter having a means for setting times. 4. The electric power according to claim 3, wherein the initial scheduled period of each half cycle of the AC power supply voltage is set within the period of the commutation flow rate required for the power commutation of the mixed bridge type power converter. Converter control unit. 5. The control device for a power converter according to claim 3, wherein the digital phase shifter includes a microcomputer.