JPH0669316B2 - Power regeneration control circuit for power converter - Google Patents

Description

The present invention relates to a power converter having a DC voltage intermediate circuit, that is, a control circuit for performing power regeneration in a voltage source inverter.

[Conventional technology]

With the exception of the polarity switching method using an electromagnetic contactor, etc., in a voltage source inverter having a DC voltage intermediate circuit, unlike a power converter having a DC current intermediate circuit, that is, a current source inverter, power regeneration cannot be performed easily. .

However, conventionally, as a power converter for DC and AC motors up to about 50 KVA, a DC voltage intermediate circuit type is often used in a servo drive area by a PWM control method using a power transistor or a modification thereof. There is. In the conventional power converter of this type, most of the regenerative power is consumed as Joule heat by a resistor connected in parallel with the capacitor of the DC voltage intermediate circuit via a switch closed during regenerative operation. is there.

This regenerative power cannot be ignored as large-capacity drive systems or those that frequently repeat forward / reverse operation and acceleration / deceleration operation, and the resistor that consumes the regenerative power also becomes large and it is necessary to consider heat generation. .

Conventionally, in a power conversion device having a DC voltage intermediate circuit,
Since the converter provided between the AC power supply and the DC voltage intermediate circuit is configured as a pure diode bridge, it is not possible to regenerate power from the load motor to the AC power supply, and the processing of power during regenerative operation of the load motor is not possible. Was a problem.

There is also a double converter system in which two sets of converters are connected in anti-parallel in order to solve such a problem, but it is not practically used because the device becomes bulky.

[Object of the Invention]

Therefore, it is an object of the present invention to provide a power regeneration control circuit of a power conversion device which is compact, economical, and can satisfactorily regenerate power with simple control.

[Outline of Invention]

In order to achieve the above-mentioned object, the present invention connects a diode of each arm element of a converter with a semiconductor switching element capable of self-extinguishing in anti-parallel, and controls the semiconductor switching element based on the detection result of the AC power supply voltage. By doing so, regenerative control is performed, and the voltage of the DC voltage intermediate circuit is controlled to be substantially constant.

That is, the present invention comprises a diode and an arm element composed of a semiconductor switching element which is connected in anti-parallel to the diode and which is capable of self-extinguishing, and is bridge-connected, and a converter whose AC terminal is connected to an AC power supply, and a DC output of this converter A current-voltage intermediate circuit having a capacitor connected between terminals, a semiconductor switching element capable of self-extinguishing, and an arm element consisting of a freewheeling diode connected in anti-parallel with it are bridge-connected, and the DC terminal has a DC voltage intermediate A power regeneration control circuit of a power conversion device configured by an inverter connected to a circuit and having an AC terminal connected to a load motor, the voltage detection circuit detecting an AC power supply voltage input to the converter, and this voltage. Based on the comparison result of the AC power supply voltage detected by the detection circuit and the conduction width control voltage, the AC power supply An energization width calculation means for obtaining an energization width control signal phase-synchronized with the pressure, and a drive control signal is formed based on the energization width control signal obtained by the energization width calculation means to include in the semiconductor switching element of the converter during power running operation. And a drive circuit that constantly supplies the power.

〔Example〕

 FIG. 1 shows an embodiment of the present invention.

In FIG. 1, U, V, and W are three-phase AC power supplies, CON is a diode as a basic element, and arm elements CTR1 to CTR6 each of which is a power transistor as a semiconductor switching element connected in antiparallel to the diode and capable of self-extinguishing. Is a bridge-connected converter, D is a diode provided with a polarity that is forward to the output DC current of the converter CON, and L
Is a DC reactor connected in parallel with diode D, C
Is a smoothing capacitor connected in parallel to the DC circuit on the output side of the diode D. DC voltage intermediate circuit DC with DC reactor L, diode D and capacitor C
Configure C. INV is an arm element consisting of a power transistor, which is a semiconductor switching element capable of self-extinguishing as a basic element, and a freewheeling diode connected in antiparallel to it.
It is an inverter that connects ITR1 to ITR6 in a bridge connection.
M is a load motor.

When the electric motor M receives AC power from the inverter INV and operates the electric motor (power running operation) (power running mode)
Converts the AC power from the AC power supplies U, V, W into DC power by the converter CON, introduces it into the inverter INV via the DC voltage intermediate circuit DCC, and converts it into AC power of arbitrary frequency and voltage. The electric motor M is supplied to drive the electric motor M. Note that the control of the inverter INV during the power running, that is, the inverter control of each transistor is performed according to a known technique, and thus will not be described in detail here.

Next, when the electric motor M performs regenerative operation (regenerative operation mode)
Will be described. In this case, the alternating-current generated power corresponding to the energy held by the electric motor M is converted into direct-current power by the converter circuit configured by each return diode of the inverter INV, and the direct-current power is converted into the direct-current reactor L.
Is converted into DC power by the inverter circuit configured by each power transistor of the converter CON via the converter and regenerated into AC power supplies U, V, W.

FIG. 2 is a time chart for explaining the operation of the inverter circuit configured by each power transistor of the converter CON in the regenerative operation mode. Figure 2 (a) is phase voltages e _u of the three-phase AC power _source, e _v, e _w, and U-phase voltage e _u the phase 30 ° relative to the 90 °, 150 °, 21
Corresponds to 0 °, 270 °, 330 °, 390 °. Each time point t ₁ , t ₂ , t ₃ ,
It shows t ₄ , t ₅ , t ₆ , and t ₇ . FIG. 3B shows the conduction timing of each diode, assuming that the diodes of the arm elements CTR1 to CTR6 of the converter CON are CTR1D to CTR6D, respectively. FIG. 6C shows the base drive signal period of the power transistors of the arm elements CTR1 to CTR6 of the converter CON. If the base is always driven at the timing shown in Fig. 2 (c), that much power is needed for the base drive, but there is no need to pay any attention to the direction of the power flow, and it is not necessary to perform powering operation. Switching to regenerative operation is performed automatically and continuously.

Now, when the electric motor M is operated in the regenerative operation mode, the voltage of the capacitor C of the DC voltage intermediate circuit DCC increases. Indicating the voltage level of the voltage E _DC and converter CON output voltage V _DC of the DC voltage intermediate circuit DCC in power running mode and the regenerative operation mode in Figure 3. In the figure, 31 is the value of the voltage E _DC at maximum load, 32 is its average value, 33 is the no-load peak voltage value (V _DCP ), and 34 is the level of the voltage E _DC during regenerative operation. . When V _DC <E _DC , the flow of electric power is automatically changed from the load motor M to the DC power supply,
When V _DC ≧ E _DC , the flow of electric power is AC power supply → power running of the load motor M. Thus, it is possible to keep the voltage of the DC voltage intermediate circuit almost constant only by detecting the AC power supply voltage, without providing a special circuit, or detecting the current or the DC voltage intermediate circuit voltage. In that case, the switching of the power transmission direction, that is, the switching of the operation mode is automatically and continuously performed.

If the voltage E _DC of the DC voltage intermediate circuit DCC becomes higher than the converter output voltage V _DC obtained by rectifying the three-phase AC power supply,
As shown in FIG. 2 (c), since the power transistors of the arm elements CTR1 to CTR6 of the converter CON are base-driven, the power from the load motor M is fed to the DC voltage intermediate circuit.
It is regenerated into a three-phase AC power supply through the DCC and the transistors of each arm element CTR1 to CTR6.

The DC reactor L and the diode D that are present in the DC voltage intermediate circuit DCC, but when the power is rapidly regenerated in the regenerative operation mode, an excessive regenerative current flows in the transistor of each arm element of the converter CON. Although L suppresses, in the power running mode, it is inserted for the purpose of short-circuiting the DC reactor L by the diode D to invalidate the reactor function. Therefore, if there is a reactance having an action equivalent to that of the reactor L in the regenerative current circuit or the regenerative current is not too large, it is not necessary to insert these.

FIG. 4 (a) shows the converter CON shown in FIG. 2 (c).
3 is a block diagram of a signal forming circuit that creates a base drive signal to be given to each transistor of FIG.

In FIG. 4 (a), ACL is an AC reactor connected in series to the AC input terminal of the converter CON, and the three-phase AC power supply voltage is 3 from the power supply side of the AC reactor ACL.
The voltage is detected by the voltage detection circuit 41 including a phase voltage transformer, and the detected voltage is waveform shaped by the waveform shaping circuit 42. For this waveform shaping circuit 42 obtained through the AC power supply voltage e _{u 'and} base drive by energization width control circuit and the logic circuit 43 the energization width control voltage v _c as an input 12
A 0 ° energization signal is generated. The energization signal generated here causes the base drive circuit 44 to form the base drive signals B _P and B _N , thereby controlling the conduction of each transistor of the converter CON.

4B to 4D are explanatory views for explaining a method of generating the base drive signal in the conduction width control circuit 43.

FIG. 4 (b) shows that the AC power supply voltage e _u ′ becomes positive after passing the zero point t _{0 at} which it changes from negative to positive, and the time t ₁ at which the voltage _eu ′ crosses the conduction width control voltage v _c. then transistor for CTR1 base drive signal v _CTR1 arm element CTR1 until time t ₃ when crossing is formed as shown in FIG. 4 (c) from. The width of the base drive signal v _CTR1 , that is, the conduction width of the transistor of the arm element CTR1 can be adjusted by the magnitude (level) of the conduction width control voltage v _c .

A hardware configuration for forming the base drive signal v _CTR1 is shown in FIG. 4 (d). This circuit comprises a comparator 45, _'as inputs and conducting width control voltage v _c, e _u' AC power supply voltage e _u may be assumed to output the base drive signal v _CTR1 in ≧ v _c interval. Signal v _CTR1 is a base drive signal for the positive-side arm element, for example, negative base drive signal v _CTR2 may be assumed to occur in e _{u '≦} -v _c interval. In the figure, Td indicates the time from the phase zero point to the time point t ₁ with the U phase as a reference.

3-phase AC power supply voltage e _u, e _v, it is not necessary to detect all e _w directly. That is, as long as the AC power supplies U, V, W have a fixed frequency and a fixed voltage, it can be obtained by detecting only one phase voltage and shifting the voltage of the other phase by 120 ° based on that. Similarly, arm element CTR1
As long obtained base drive signal to the base drive signal v _CTR3 for CTR2, CTR3 like other arm element, v
_{CTR5 and the} like can be obtained by sequentially shifting the signal having a time width of v _CTR1 by 120 °.

FIG. 5 is a block diagram showing a circuit configuration of another embodiment of the present invention.

In this embodiment, a single-phase bridge power switching circuit 51 is connected to the load side of the DC voltage intermediate circuit DCC, and a DC motor DCM which is operated in four quadrants is connected to its output terminal via the power switching circuit 51. The power switching circuit 51 corresponds to the inverter INV of FIG. 1 from which the arm elements ITR5 and ITR6 are omitted. Therefore, referring to FIG. 1, the normal rotation power running operation is performed by controlling the conduction of only the transistors of the arm elements ITR1 and ITR4, and the reverse power running operation is performed by the conduction control of only the transistors of the arm elements ITR3 and ITR2. Forward rotation regeneration operation by conduction of each diode of ITR1 and ITR4,
Conduction of each diode of the arm elements ITR3 and ITR2 enables the operation of four quadrants, which is the reverse regeneration operation. In this case, the power switching circuit 51 has reversible direct current instead of alternating current, but has a circuit configuration similar to that of the inverter and performs a function similar to that of the inverter INV shown in FIG. I will call it. Further, among the input / output terminals of the power switching circuit 51, the terminal connected to the DC voltage intermediate circuit DCC is referred to as a DC terminal, and the terminal connected to the load motor DCM is referred to as an AC terminal for convenience.

According to the operation mode (any one of the four quadrants) of the DC motor DCM, when the relationship between the voltage E _DC of the DC voltage intermediate circuit DCC and the output voltage V _DC of the converter CON is V _DC <E _DC , the flow of power flows. Is a regenerative operation of the load motor DCM → AC power supply, and when V _DC ≧ E _DC , the flow of electric power is a power running operation of the AC power supply → the load motor DCM.

In each of the above embodiments, the power transistor is illustrated as the self-extinguishing semiconductor switching element provided in each arm element, but the self-extinguishing semiconductor switching element used in the device of the present invention is, for example, GTO (gate It may be a turn-off thyristor) or SIT (static induction transistor). Further, the switching element and the diode connected in anti-parallel thereto may be a so-called composite type housed in the same package, or may be a combination of independent parts.

The number of phases of the AC power supply is not limited to three and may be a single phase or a multiphase other than three phases.

Further, although a single square wave signal is shown in the above embodiment as a drive signal for the semiconductor switching element capable of self-extinguishing each arm element, the present invention is not limited to this. For example, FIGS. 6A and 6B show, for example, an inverter.
An example in which the switching element carrier frequency signal f _c of each arm element of INV is used as a control signal is shown. In FIG. 6B, when _eu ′ ≧ f _c , “0”, _eu ′
<Plurality of pulse width controlled PW to "1" when the f _c
The waveform of the regenerative current can also be controlled using the M signals 61 to 64.

[Effects of the Invention] Thus, according to the present invention, the following effects can be achieved.

1) The voltage of the DC voltage intermediate circuit can be automatically kept almost constant without performing current detection or providing any special voltage stabilizing means.

2) Bidirectional power transmission can be performed continuously and automatically.

3) Electric power can be regenerated with a power factor of 1 for the power source.

[Brief description of drawings]

FIG. 1 is a connection diagram showing the main circuit configuration of an embodiment of the present invention,
2 (a), (b), and (c) are time charts showing the AC power supply voltage, the diode conduction period of the converter, and the base drive period of the converter transistor, respectively. FIG. 3 shows the power running mode and the regenerative mode. The figure which shows the voltage level of a DC voltage intermediate circuit voltage and a converter output voltage, FIG. 4, (a), (b), (c),
(D) is a block diagram of a circuit that forms a base drive signal of the converter, a diagram showing a relationship between an AC power supply voltage and a conduction width control voltage, an explanatory diagram of the base drive signal, and a diagram showing a hardware configuration for generating the signal, FIG. 5 is a connection diagram showing a main circuit configuration of another embodiment of the present invention, FIG. 6 (a),
(B) is a pulse waveform diagram of the base drive signal in the PWM control of the present invention, and an explanatory diagram of an AC power supply waveform and a carrier control signal waveform used to generate it. U, V, W …… 3-phase AC power supply CON …… Converter CTR1 to CTR6 …… Converter arm element DCC …… DC voltage intermediate circuit INV …… Inverter ITR1 to ITR6 …… Inverter arm element M, DCM …… Load motor 41 ...... Voltage detection circuit 42 ...... Waveform shaping circuit 43 …… Conduction width control circuit and logic circuit 44 …… Base drive circuit 51 …… Single-phase bridge power switching circuit

Continuation of front page (56) Reference JP-A-51-58625 (JP, A) JP-A-55-94583 (JP, A) JP-A-58-151879 (JP, A) JP-A-58-179180 (JP , A)

Claims (1)

[Claims] 1. A converter in which an arm element composed of a diode and a semiconductor switching element which is connected in antiparallel with the diode and which can be self-extinguished is bridge-connected, and an AC terminal is connected to an AC power supply, and a DC output of this converter. A current-voltage intermediate circuit having a capacitor connected between terminals, an arm element consisting of a semiconductor switching element capable of self-extinguishing and a freewheeling diode connected in antiparallel to it is bridge-connected, and the DC terminal is the DC voltage. A power regeneration control circuit of a power conversion device comprising an inverter connected to an intermediate circuit and having an AC terminal connected to a load motor, the voltage detection circuit detecting an AC power supply voltage input to the converter, Based on the comparison result of the AC power supply voltage detected by this voltage detection circuit and the conduction width control voltage, An energization width calculation means for obtaining an energization width control signal phase-synchronized with the AC power supply voltage, and a drive control signal is formed based on the energization width control signal obtained by the energization width calculation means to perform a power running operation on the semiconductor switching element of the converter. A power regeneration control circuit for a power conversion device that includes a drive circuit that constantly supplies power including time.