JPS6264281A - Power source regeneration system for voltage-type inverter - Google Patents

Abstract

PURPOSE:To reduce the size of a voltage inverter by suppressing the rise of a DC intermediate circuit voltage during wasteful switching time of power converter switching time to enhance the intermediate circuit voltage at normal operation time. CONSTITUTION:The actual speed value from a speed detector 8, a torque command value from a speed regulator 306 and the actual voltage value from a DC intermediate circuit are input to a control mode switching circuit 27, and a switching command is properly output from the switching circuit 27 to a torque command switching circuit 305 and a converter switching circuit 300. When the switching circuit 27 detects the start of rising the intermediate circuit voltage due to the discharge of energy stored in a circuit inductance at current interruption time, it applies a drive torque to the switching circuit 305 to drive an induction motor 7 to consume the energy, thereby suppressing the rise of the intermediate circuit voltage.

Description

[Detailed description of the invention] [Technical field to which the invention pertains]

This invention provides a power regeneration system for a voltage source inverter in which a voltage source inverter receives power from a pair of power converters that are connected in antiparallel and perform forward and reverse switching without circulating current, and regenerates energy to an AC power source.

[Prior art and its problems]

FIG. 2 is a block diagram showing a conventional example of a voltage source inverter that receives power from a pair of power converters that perform forward and reverse switching without circulating current. In FIG. 2, the main circuit is constructed as follows. That is, the forward side thyristor converter 2F and the reverse side thyristor converter 2R, in which the thyristors are connected in a three-phase full-wave bridge, are connected in antiparallel to each other to form a pair of power converters, and these thyristor converters There is a three-phase AC power supply l on the AC side common to these converters, and a so-called DC intermediate circuit equipped with a DC reactor 4 and a smoothing capacitor 5 on the DC side common to these converters.
A transistor inverter 3 as a voltage source inverter is connected via this DC intermediate circuit. Further, an induction motor 7 as a load is connected to the AC side of the transistor inverter 3. The control method of the transistor inverter 3 is a known slip frequency speed responsive vector control method, in which the actual speed value from the speed detector 8 coupled to the induction motor 7 and the speed command value from the speed setter 307 are combined. The deviation of speed regulator 30
6, and the torque command value output from the speed regulator 306 and the actual speed value from the speed detector 8 mentioned above are applied to the vector calculator 304. The vector calculator 304 performs vector calculations on these input signals and the internally set magnetic flux command value, outputs a primary current command value, and calculates the primary current actual value detected by the current transformer 10B and this primary current command value. The deviation from the current value is input to the current regulator 303. This current regulator 30
The output signal of No. 3 becomes a sinusoidally modulated pulse in the pulse width modulator 302, which is applied in a predetermined order to the base of each transistor constituting the transistor inverter 3 via the base drive circuit 301. 3 can output AC power of a desired voltage and frequency to operate the induction motor 7 at variable speed. Head side thyristor converter 2F and opposite side thyristor converter 2R
The control method is a known voltage control method without circulating current, with a current minor loop, and with a voltage preparation circuit during forward/reverse switching, and the deviation between the voltage command value from the voltage setting device 31 and the actual DC intermediate circuit voltage value is voltage regulator 29. The current command value output from this voltage regulator 29 and the current transformer 10
The deviation from the actual current value detected by A and the rectifier 11 is given to a current regulator 28 to form a current control loop, the output of this current regulator 28 is given to a gate phase angle generator 22F or 22R, and further These outputs become gate pulses via the gate pulse generator 21F or 21R and are applied to the layer side thyristor converter 2F or the reverse side thyristor converter 2R, respectively. If the current command value output from the voltage regulator 29 has positive polarity, it is the drive mode, and when it is negative, it is the braking mode, then the current command value input to the converter switching circuit 30 has positive polarity. In this case, the drive mode, that is, the layer side thyristor converter 2F is operating. Here, when the linearity of this current command value switches from positive to negative, the converter switching circuit 30 outputs:
First, a maximum phase delay angle shift command is given to the forward side gate phase angle generator 22F to reduce the output current of the layer side thyristor converter 2F, and at the same time an output hold command is given to the current regulator 28 to reduce the output current of the layer side thyristor converter 2F. The phase angle of the converter 2R is kept in a set state. As a result, when the current transformer 10A and the rectifier 11 detect that the current in the layer-side thyristor converter 2F has become zero, this converter switching circuit 3
0 cuts off the gate pulse generator 21F for the forward side that has been selected so far and switches the gate pulse generator 21F for the reverse side.
At the same time, the phase delay angle shift command given to the gate phase angle generator 22F and the current regulator 28
Release the output hold command given to
Electric power is regenerated to the phase AC power supply 1. By the way, as mentioned above, when the operation mode is switched from the drive mode to the braking mode, that is, during the switching dead time when switching the head side thyristor converter 2F during operation to the reverse side thyristor converter 2R, the regeneration of the transistor inverter a is performed. Since the smoothing capacitor 5 installed in the DC intermediate circuit is charged by the current, the DC intermediate circuit voltage increases. Therefore, the commutation margin angles of the thyristor converters 2F and 2R must be determined taking into account this rise in DC intermediate circuit voltage. In other words, the DC intermediate circuit voltage just before switching the forward/reverse direction of the Cyrisk converter is F! , d, if the voltage increase at the time of switching is ΔEd, and the effective value of the AC power supply voltage is Ea, then the phase advance angle β is given by the following equation (13). (However, the overlap angle is ignored.) 1 .35・Ea In other words, before switching, the DC intermediate 1 circuit voltage must be lowered by the voltage increase ΔEd, so the cyrisk converters 2F and 2R and the transistor inverter 3 are elements with a large current capacity by this voltage drop. This has the major drawbacks of increasing costs and increasing the size of the device.

[Purpose of the invention]

This invention increases the DC intermediate circuit voltage during steady operation by suppressing the increase in DC intermediate circuit voltage during the switching dead time when switching a power converter from the forward side to the reverse side without circulating current. The purpose of the present invention is to provide a power regeneration method for voltage source inverters that can perform the following steps.

[Key points of the invention]

This invention enables forward-reverse switching without circulating current.Even if a voltage source inverter that receives DC power from a pair of power converters connected in antiparallel cannot switch from drive mode to regeneration mode, the power converter remains in the forward side. Switching from one side to the other side requires a switching dead time, and the regenerative energy of the voltage source inverter increases the DC intermediate circuit voltage during this switching dead time. Even if the mode is determined, the regenerative current is not allowed to flow, and in the meantime, the head side power converter is shut off, and the energy released from the circuit inductance at this time of disconnection is supplied to the load via the voltage source inverter, and the head side power converter is shut off. If zero current is confirmed in the power converter on the side, the power converter on the opposite side is commanded to start operating, and the voltage source inverter is operated in regeneration mode to prevent energy from the load from increasing the DC intermediate circuit voltage. This is to allow regeneration to the AC tB side.

[Embodiments of the invention]

FIG. 1 is a block diagram showing an embodiment of the present invention, and the details of the present invention will be explained below with reference to FIG. In Fig. 1, the three-phase AC power from the three-phase AC T4fil is supplied to the forward side Cyrisk converter 2F and the reverse side Cyrisk converter 2R, which are configured with a full-wave bridge connection of Cyrisk. The thyristor converters 2F and 2R on the side and the opposite side are connected in antiparallel to each other. Both of these thyristor converters 2F. A filter circuit formed by a DC reactor 4 and a smoothing capacitor 5 is provided in a so-called DC intermediate circuit that connects the DC side common to 2R and the DC side of the transistor inverter 3 as a voltage source inverter. . Further, an induction motor 7 as a load is connected to the AC side of the transistor inverter 3. The control of the transistor inverter 3 is as follows. That is, the deviation between the actual speed value from the speed detector 8 coupled to the induction motor 7 and the speed command value from the speed setter 307 is given to the speed regulator 306, but in the present invention, this speed adjustment The torque command switching circuit, '! 05 to the vector arithmetic unit 304. The vector calculator 304t inputs the actual speed value from the speed detector 8 mentioned above and this torque command value, and outputs the primary current command value by internal calculation, as in the case of the conventional example described above. Yes, the actual value of the primary current obtained from the current transformer 10B and this 1
Input the deviation from the next current command value to the current regulator 303,
The output of the current regulator 303 is applied in a predetermined order to the bases of the transistors constituting the transistor inverter 3 via the pulse width modulator 302 and the base drive circuit 301.
The induction motor 7 can be operated at variable speed by outputting AC power of a desired voltage and frequency. Forward side thyristor converter 2F and reverse side thyristor converter 2R
The control is as follows. That is, the deviation between the voltage command value from the voltage setting device 31 and the actual DC intermediate circuit voltage value is given to the voltage regulator 29, and the current command value outputted from the voltage regulator 29 is calculated by the current transformer 10A and the rectifier 11. The deviation from the detected actual current value is given to the current regulator 2 to form a current control loop. The output of this current regulator 2 is given to the forward side thyristor converter 2F via the gate phase angle generator 22F and the gate pulse generator 21F according to the command from the converter switching circuit 3o. Make it work or
Alternatively, the signal is applied to the opposite thyristor converter 2R via the gate phase angle generator 22R and the gate pulse generator 21R to operate it. In the present invention, a braking mode switching circuit 27 is provided, and the actual speed value from the speed detector 8, the torque command value from the speed regulator 306, and the actual voltage value from the DC intermediate circuit are set to this braking mode. The signal is input to the switching circuit 27, and from there, appropriate switching commands are output to the torque command switching circuit 305 and the converter switching circuit 30. Therefore, these operations will be described below. If the current command value output from the voltage regulator 29 has a positive polarity, it is the driving mode, and when it is negative, it is the braking mode.If this current command value is positive, the converter switching circuit 30 As a result, the output of the current regulator 28 passes through the gate phase angle generator 22F and the gate pulse generator 21F for the forward side and operates the layer side Sirisk converter 2F, so that the AC power from the three-phase AC power 1llll is transferred to the layer side Induction motor 7 via Cyrisk converter 2F and transistor inverter 3
is given, and this electric motor is operated at the speed commanded by the speed setter 307. When the speed setting device 307 is operated to reduce or zero the speed command value in order to decelerate or stop the induction motor 7 in operation, the braking mode switching circuit 27 changes the speed setting device 30
It is determined from the torque command direction input from 7 and the motor rotation direction input from speed detector 8 that the operating mode has changed to drive-braking. Therefore, this braking mode switching circuit 27 outputs a command to the converter switching circuit 30 to select the reverse side thyristor converter 2R, so the converter switching circuit 30 generates a gate phase angle for the forward side according to this command. A maximum phase delay angle shift command is given to the converter 22F to make the current in the layer-side Sirisk converter 2F zero. When the braking mode switching circuit 27 detects that the energy stored in the circuit inductance is released during this current interruption and the DC intermediate circuit voltage begins to rise, it gives a driving torque command to the torque command switching circuit 305 to control the induction motor 7. By driving, the above-mentioned energy is consumed and an increase in the DC intermediate circuit voltage is suppressed. When the DC intermediate circuit voltage reaches a state immediately before the switching operation by the above operation, the layer side thyristor converter 2F is switched to the opposite side thyristor converter 2R by the same switching operation as explained in the conventional example of FIG. However, at the same time, the drive torque command given from the braking mode switching circuit 27 to the torque command switching circuit 305 is canceled. Therefore, the transistor inverter 3 causes a normal regenerative torque current to flow, and the reverse side thyristor converter 2R regenerates this to the source 1 as a three-phase alternating current.

【Effect of the invention】

According to this invention, in a device consisting of a pair of power converters connected in antiparallel to each other and performing forward/reverse switching without circulating current, and a voltage source inverter that receives DC power from this, the operation mode is set to drive mode. When switching to braking mode, the layer-side power converter in operation is switched to the opposite-side power converter, and the increase in DC intermediate circuit voltage is suppressed during the switching dead time when switching the power converter. Therefore, the DC intermediate circuit voltage during steady operation can be increased by this voltage increase, and the voltage of the load can also be increased. Discharge power converters and voltage source inverters can reduce the current capacity commensurate with this increase in steady-state voltage, so the cost of these power converters and voltage source inverters can be reduced, and the overall equipment It also has the advantage of being compact.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG.
The figure is a block diagram showing a conventional example of a voltage source inverter that receives power from a pair of power converters that perform forward and reverse switching without wI ring current. 1: 3-phase AC tB, 2F: layer side thyristor converter as power converter, 2R: reverse side thyristor converter as power converter, 3: ii! Transistor inverter as a pressure type inverter, 4: DC reactor, 5: Smoothing capacitor, 7: Induction motor as load, 8: Speed detector,
IOA, IOB: Current transformer, 11: Rectifier, 21F,
21R: Gate pulse generator, 22F. 22R: Gate position...angular generator, 27: Braking mode switching circuit, 28: Current regulator, 29: Voltage regulator, 3o: Converter switching circuit, 31: Voltage setting device, 301: Base drive circuit, 302: B/L/S width modulator, 303:1ii
jij regulator, 304: Heku l-JL [l calculation a, 305
: Torque command switching circuit, 306: Speed regulator, 307
;Speed setting device. Group・1. mll gear tooth 17μ

Claims (1)

[Claims] 1) A voltage source inverter that converts DC power from a DC intermediate circuit into AC power and supplies it to a load; and a voltage source inverter that is connected to an AC power source and connected in antiparallel to each other with respect to the DC intermediate circuit for forward-reverse switching without circulating current. In a device configured with a pair of power converters that perform After cutting off the current of the side power converter and applying the energy in the circuit inductance released at this time to the load via the voltage source inverter, the opposite side power converter is operated, and this voltage source inverter is A power regeneration system for voltage source inverters that is characterized by operation in braking mode.