JP5045053B2 - System parallel insertion device for synchronous motor - Google Patents

Description

  The present invention relates to a synchronous motor system paralleling device for charging a synchronous motor to a power system at a predetermined timing.

FIG. 7 is a configuration diagram of a conventional system parallel insertion device for a synchronous motor.
In FIG. 7, 10 is a power system into which the synchronous motor SM is inserted, 11 is a transformer connected to the primary side of the power system 10, and 20 is connected to the secondary side of the transformer 11 to the field winding 13 of the motor SM. A field converter for supplying a predetermined field current, CB-S is a circuit breaker connected to the power system 10, 12 is a transformer, 30 is a starter connected to the secondary side of the transformer 12, and CB-6 is A circuit breaker connected between the starter 30 and the armature winding of the electric motor SM, CB-42 is a circuit breaker for charging the electric motor SM into the electric power system 10, PT ₁ and PT ₂ are instrument transformers, Reference numeral 40 denotes a synchronizing device connected between the instrument transformers PT ₁ and PT ₂ , and 50 denotes an AVR (automatic voltage regulator) circuit connected in parallel to the synchronous device 40.

Next, the operation of FIG. 7 will be described with reference to the timing chart of FIG. First, in the initial state, the circuit breakers CB-S, CB-6, and CB-42 are all open.
First, a current is passed from the field converter 20 to the field winding 13 to excite the synchronous motor SM. Next, the circuit breaker CB-S, a CB-6 was charged at time t ₁ in FIG. 8, by applying a current to the armature winding of the motor SM to generate a torque by the starting device 30 to start the synchronous motor SM .

Then, after accelerating the motor SM until the difference between the operating frequency of the motor SM and the system frequency becomes a minute value of about 0.3 Hz, the AVR circuit 50 connected between the instrument transformers PT ₁ and PT ₂ In response to the output signal, the field current is manipulated through the field converter 20 to control the motor terminal voltage (motor voltage) and the system voltage to coincide with each other.

At this time, since the difference between the operating frequency of the motor SM and the system frequency is about 0.3 Hz and is very small, the phases of the motor voltage and the system voltage coincide with each other at intervals of several seconds.
A system voltage and an electric motor voltage are input to the synchronization input device 40 via instrument transformers PT ₁ and PT ₂ , and the amplitude and phase of the AC voltage are monitored. The synchronization inserting device 40 is earlier by a predetermined time than the timing of the phase matches the motor voltage and the system voltage, at time t ₂ in FIG. 8, it outputs a closing command to the circuit breaker CB-42. Thereafter, at the time when the phases of both voltages coincide, the main contact of the circuit breaker CB-42 comes into contact.
That is, there is a delay time (breaker closing time) from when the synchronous closing device 40 outputs a closing command to the circuit breaker CB-42 to excite the closing coil until the main contact actually contacts.

FIG. 9 is a timing chart showing the operation of the circuit breaker CB-42.
Closing command of the circuit breaker CB-42 from the synchronization inserting device 40 at time t ₄ in FIG. 9 is output, the phase difference between the delayed time t _{5 (system} voltage and motor voltage circuit breaker on time Δt from the time t ₄ is At the time of zero), the main contact of the circuit breaker CB-42 is actually turned on.

Then, at time t ₃ when a predetermined time has elapsed from the time t ₂ in FIG. 8, after confirming the insertion of the main contacts of the circuit breaker CB-42, the opening command to the circuit breaker CB-6 to block it is outputted Thus, the supply of the armature current through the starter 30 is stopped, and thereafter, the electric power is supplied from the power system 10 to the electric motor SM.

  In addition, the system parallel insertion apparatus for synchronous motors as described above is described in, for example, Patent Documents 1 and 2 below.

JP-A-62-247776 (page 2, upper left column, line 10 to lower right column, line 18, FIG. 3 etc.) JP-A-57-88881 (the first page, lower right column, lines 9 to 18)

As described above, the breaker CB-42 has a closing time Δt as a delay time from the excitation of the closing coil to the contact of the main contact. It depends on. However, if the charging time Δt changes, the main contact may come into contact with the system voltage and the motor voltage being out of phase, which causes power supply disturbance to the power system 10.
For this reason, it is necessary to periodically measure the closing time Δt of the circuit breaker and reset the measured value in the synchronous closing device 40, which requires a lot of labor and labor.

  Therefore, a problem to be solved by the present invention is to provide a synchronous motor system paralleling apparatus that allows a synchronous motor to be input into the system without maintenance, without being troubled by resetting the input time Δt.

In order to solve the above problems, the present invention has been made paying attention to a voltage phase control method for a synchronous motor when a system is turned on.
That is, the invention described in claim 1 is a circuit breaker provided between the electric power system and the electric motor at the timing when the frequency difference, amplitude difference and phase difference between the terminal voltage of the synchronous motor and the system voltage become substantially zero. In the system paralleling device for synchronous motors, in which the electric motor is inserted and the electric motor is synchronously inserted into the electric power system,
A first calculation means for phase-converting each of the system voltage and the motor voltage and performing coordinate conversion using the system voltage phase to calculate an orthogonal biaxial component of the motor voltage;
Second computing means for computing a phase difference between the system voltage and the motor voltage from the orthogonal two-axis component;
A phase adjusting means for generating a correction signal of a speed command value of the electric motor so that the phase difference becomes zero;
Speed adjusting means for adjusting the deviation between the speed command value corrected by the correction signal and the speed detection value to zero and outputting the current command value of the motor;
Current adjusting means for performing an adjustment operation so as to make the deviation between the current command value and the current detection value zero and outputting a PWM command;
PWM means for generating a drive signal for a switching element of a PWM inverter that starts the electric motor according to the PWM command,
At the time of starting the electric motor, the inverter is started at a driving frequency slightly lower than the system voltage frequency by the inverter, and the phase adjusting means is at a timing when the phase difference calculated by the second calculating means becomes zero. operating the amplitude difference and previous SL phase difference between the system integrated voltage and the motor voltage outputs closing command for the circuit breaker at a timing becomes zero, then cuts off the power supply to the motor by the inverter Is.

According to a second aspect of the present invention, in the synchronous motor system parallel insertion device according to the first aspect, the current adjustment is performed so that the control of the inverter does not become unstable when the electric motor is synchronously input to the electric power system. a shall switch the constant means.

According to the present invention, there is no need for a synchronous closing device that outputs a synchronous closing command in consideration of a preset circuit breaker closing time as in the prior art, and a phase difference between the system voltage and the motor voltage is controlled by the control device. Is detected by a simple method, and the inverter is controlled based on the output of the adjusting means that makes the phase difference zero, so that the synchronous motor is input to the power system at a timing satisfying a predetermined synchronous input condition. Can do. Therefore, it is possible to realize a parallel insertion device capable of supplying a synchronous motor without maintenance without being bothered by resetting the breaker closing time.
Further, by utilizing the PLL circuit constituting the phase adjusting means at a predetermined timing, the synchronous motor can always be operated in power, and can be applied to an inverter having no regenerative function.
Furthermore, if the constant of the current adjusting means is switched, it is possible to prevent the inverter control from becoming unstable before and after the synchronization is turned on.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
First, FIG. 1 is a control block diagram showing the configuration of this embodiment. The same components as those in FIG. 7 are denoted by the same reference numerals and the description thereof will be omitted. Hereinafter, different portions will be mainly described.

In FIG. 1, reference numeral 31 denotes a PWM inverter as a stationary starter connected to the secondary side of the transformer 12. The AC voltage output from the PWM inverter 31 can be supplied to the armature winding of the synchronous motor SM via the circuit breaker CB-6, and the inverter 31 is used when starting and accelerating the motor SM. is there.
The power system 10 and the armature winding of the synchronous motor SM can be connected via the circuit breaker CB-42 and are connected to the control device 100 via the instrument transformers PT ₁ and PT ₂ . . The control device 100 outputs the field current command value and the gate signal for the switching element of the PWM inverter 31 by using the secondary voltages of the instrument transformers PT ₁ and PT ₂ as inputs.

Next, the configuration and operation of the control device 100 will be described.
The deviation of the secondary voltage of the instrument transformers PT ₁ and PT ₂ is obtained by the adder / subtractor 121, and this deviation is input to the AVR circuit 103. In the AVR circuit 103, a complementary setting signal Δφ of the magnetic flux command value is obtained, and this complementary setting signal Δφ is added to the magnetic flux setting value by the adder / subtractor 122. Deviation from the detected value is obtained. The magnetic flux adjuster 104 calculates a field current command value that eliminates the deviation, and the field current command value is input to the field converter 20.

The secondary voltages of the instrument transformers PT ₁ and PT ₂ are also input to the phase difference calculation circuit 101, and the phase difference as the output is input to the PLL circuit 102 and the circuit breaker closing condition calculation circuit 105. Yes. Here, the PLL circuit 102 constitutes phase adjusting means. Note that the output of the adder / subtractor 121 is also input to the arithmetic circuit 105.
The circuit breaker closing condition calculation circuit 105 determines that the closing condition of the circuit breaker CB-42 is satisfied from the output of the phase difference calculation circuit 101 and the output of the adder / subtractor 121, and the circuit breaker on the system 10 side of the synchronous motor SM. The input command for CB-42 is output.

The output of the PLL circuit 102 is added to the speed setting value by the adder / subtractor 124 as a correction signal for the speed setting value of the motor SM, and the deviation between the output speed command value and the speed detection value is calculated by the adder / subtractor 125. The This deviation is input to an ASR (automatic speed adjustment) circuit 106, and a current command value that eliminates the deviation is calculated, and a deviation between the current command value and the current detection value of the motor SM is calculated by the adder / subtractor 126. .
An ACR (automatic current adjustment) circuit 107 performs an adjustment operation so as to eliminate the deviation between the current command value and the current detection value, and its output is given to the PWM circuit 108 as a PWM command. The PWM circuit 108 generates a gate signal for the switching element of the PWM inverter 31 and supplies the gate signal to the PWM inverter 31 to turn on / off the switching element.

Next, the operation of this embodiment will be described.
First, as described above, in the initial state, the circuit breakers CB-S, CB-6, and CB-42 are all open, and a current is passed from the field converter 20 to the field winding 13 to excite the synchronous motor SM. To do. Next, the circuit breakers CB-S and CB-6 are turned on, and the synchronous motor SM is accelerated by the PWM inverter 31. At this time, the speed set value of the synchronous motor SM is given to the adder / subtractor 124 as a frequency slightly lower than the system frequency.

  After the actual speed of the synchronous motor SM coincides with the speed setting value, the AVR circuit 103 calculates a complementary setting signal Δφ of the magnetic flux command value, and the auxiliary setting signal Δφ is added to the magnetic flux setting value in the adder / subtractor 122. . The magnetic flux regulator 104 calculates and outputs the field current command value so that the deviation between the magnetic flux command value and the detected magnetic flux value, which is the addition result, is zero. The field converter 20 adjusts the field current according to the command value, so that the magnitude of the motor voltage matches the magnitude of the system voltage, and the input deviation of the AVR circuit 103 becomes zero.

FIG. 2 is a block diagram showing a configuration of the phase difference calculation circuit 101.
After the system voltage (line voltage) V _rs , V _st and the motor voltage (line voltage) V _uv , V _vw input from the instrument transformers PT ₁ , PT ₂ are respectively converted into three-phase quantities, The signal is converted into a two-phase quantity by the three-phase / two-phase converters 101a and 101b, further coordinate-converted by the vector rotators (VD) 101c and 101d, and the DC signals V _ms , V _ts , V _mm , V from the AC signal. Each _tm is calculated. These DC signals V _ms , V _ts , V _mm , and V _tm are input to the V _δ and V _γ calculator 101e, and the δ-axis component V _δ and the γ-axis component V _{γ of} the motor voltage V _m are calculated.
Here, the three-phase / two-phase converters 101a and 101b, the vector rotators 101c and 101d, and the V _δ and V _γ arithmetic units 101e constitute first arithmetic means.

Assuming that the axis having the same phase as the system voltage V _s is the γ axis and the axis advanced by 90 ° el (electrical angle) with respect to the γ axis is the δ axis as shown in FIG. 3, the δ of the motor voltage V _m The axial component V _δ and the γ-axis component V _γ can be obtained by a simple calculation such as the following formulas 1 and 2. Note that θ _s represents the system voltage phase, and φ represents the phase difference between the system voltage V _s and the motor voltage V _m .

[Formula 1]
_{V δ = V m × sinφ =} V m × sin (φ + θ s -θ s)
= V _m * {sin (φ + θ _s ) cos (−θ _s ) + sin (−θ _s ) cos (φ + θ _s )}
_{= V m × {sin (φ} + θ s) × V ms / V s -V ts / V s × cos (φ + θ s)}
_{= V tm × V ms / V} s -V mm × V ts / V s
= 1 / V _s × (V _tm × V _ms −V _mm × V _ts )

[Formula 2]
V _γ = V _m × cos φ = V _m × cos (φ + θ _s −θ _s )
= V _m × {cos (φ + θ _s ) cos (−θ _s ) + sin (−θ _s ) sin (φ + θ _s )}
_{= V m × {cos (φ} + θ s) × V ms / V s + V ts / V s × sin (φ + θ s)}
= V _mm × V _ms / V _s + V _tm × V _ts / V _s
= 1 / V _s × (V _mm × V _ms + V _tm × V _ts )

In the above formulas 1 and 2, the magnitude of the system voltage V _s can be calculated by formula 3.
[Formula 3]
V _s = √ (V _ms ² + V _ts ² )

Of V _[delta] Figure 2, V _gamma calculator 101e is V _[delta] by the equation 1 Equation 3 calculates the V _gamma, phase difference calculator 101f as a second arithmetic means, these V _[delta], the V _gamma Then, the phase difference φ between the system voltage V _s and the motor voltage V _m is calculated by φ = tan ⁻¹ (V _δ / V _γ ).

In FIG. 1 again, the circuit breaker closing condition calculation circuit 105 has zero deviation between the system voltage V _s and the motor voltage V _m, and the phase difference φ is set by the phase difference calculation circuit 101 (phase difference calculation unit 101f). When it becomes zero, it is determined that the closing condition is satisfied, a closing command is sent to the breaker CB-42, and the breaker CB-42 is turned on. After that, after confirming that the main contact of the circuit breaker CB-42 is turned on as in the conventional case, a circuit break command is output to the circuit breaker CB-6, and this is cut off, whereby the armature current from the PWM inverter 31 is output. Then, power is supplied from the power system 10 to the motor SM.

Here, the PLL circuit 102 outputs a correction signal for correcting the speed set value so that the phase difference φ becomes zero, and operates so that the phase of the motor voltage matches the phase of the system voltage.
Before using (operating) the PLL circuit 102, the drive frequency of the electric motor SM by the PWM inverter 31 is set slightly lower than the system frequency as described above. For this reason, if the difference between the drive frequency and the system frequency is Δf, the phase of the motor voltage and the system voltage coincide with each other at a period of 1 / Δf, and then the system voltage is shifted in the advance direction with respect to the motor voltage. Repeat the process.

In this case, if the PLL circuit 102 is utilized at an arbitrary timing, the speed setting value is corrected by the operation and becomes a value lower than the system frequency. As a result, the current command value may become negative due to the operation of the ASR circuit 106. is there. That is, when the electric motor SM is in a regenerative operation and the PWM inverter 31 does not have a regenerative function, a problem occurs.
In order to prevent this, in other words, in order to make the electric motor SM always perform a power running operation when the PLL circuit 102 is utilized, it is desirable to determine the timing for utilizing the PLL circuit 102 by the following method.

FIG. 4 is a diagram showing the phase difference between the system voltage and the motor voltage, the waveforms of V _δ and V _γ , and the timing at which the PLL circuit 102 is utilized.
In order to make the electric motor SM perform a power running operation when the PLL circuit 102 is utilized, the system frequency is higher than the driving frequency of the electric motor SM, so that the phase of the system voltage is equal to the phase of the electric motor voltage. By making use of this, the motor voltage supplied from the PWM inverter 31 follows the system voltage, and is always a power running operation.
Therefore, based on the waveforms of V _δ and V _γ in FIG. 4, the timing t ₀ when the phase difference between the system voltage and the motor voltage becomes _zero is detected, and the PLL circuit 102 is utilized at this timing t ₀ . That's fine.

Figure 5 is a circuit configuration for generating a timing _{t 0} to utilize the PLL circuit 102 described above, 91, 92, 94 is a comparator determines the sign of the input signal, 93 and 95 show an AND gate.
In FIG. 5, the current calculation value and the previous calculation value of V _{δ that} change as shown in FIG. 4 are respectively input to the comparators 91 and 92, so that the output signal of the AND gate 93 is “High” at the zero cross point of V _δ. Become a level.
At the same time, when V _γ ≧ 0, the output signal of the comparator 94 becomes the “High” level, and the output signal of the AND gate 95 to which this signal and the output signal of the AND gate 93 are input becomes the “High” level and the PLL. A timing t ₀ that makes use of the circuit 102 is generated.
Here, the reason why the condition of V _γ ≧ 0 is necessary is that there are two zero cross points of V _δ as apparent from FIG.

FIG. 6 shows the configuration of ACR constant selection means for switching the constants of the ACR circuit 107 so that the control of the PWM inverter 31 does not become unstable.
When the system breaker CB-42 is turned on, the motor SM is connected in parallel to the system, and the output impedance of the PWM inverter 31 decreases, so the constant (proportional gain or integral gain) of the ACR circuit 107 (current control system) Must be automatically switched to an appropriate value.

  For this reason, as shown in FIG. 6, the ACR constant at the time of acceleration and the ACR constant at the time of synchronizing are held in advance, and the switching means 96 is operated to synchronize from the ACR constant at the time of acceleration when the completion of acceleration is confirmed. Switch to the hour ACR constant. However, in order to perform the operation of the ACR circuit 107 in a shockless manner, it is desirable to gradually change the ACR constant by interposing the ramp function HLR on the ACR constant side when the synchronization is turned on.

It is a control block diagram which shows embodiment of this invention. It is a block diagram of the phase difference calculating circuit in FIG. It is a vector diagram, such as a system voltage in an embodiment, and a motor voltage. Phase difference between the system voltage and the motor voltage, V _[delta], is a diagram showing a timing to make use of the waveform of V _gamma, and a PLL circuit. It is a circuit block diagram for producing | generating the timing which utilizes a PLL circuit. It is a block diagram of an ACR constant selection means. It is a block diagram of the conventional system | straining apparatus for synchronous motors. It is a timing chart which shows operation | movement of the circuit breaker in FIG. FIG. 8 is a timing chart for explaining a closing time of the circuit breaker CB-42 in FIG. 7.

Explanation of symbols

10: Power system 11, 12: Transformer 13: Field winding 20: Field converter 31: PWM inverter 91, 92, 94: Comparator 93, 95: AND gate 96: Switching means 100: Control device 101: Phase difference Arithmetic circuits 101a, 101b: 3-phase / 2-phase converters 101c, 101d: vector rotators 101e: V _δ , V _γ computing units 101f: phase difference computing units 102: PLL circuits 103: AVR circuits 104: magnetic flux regulators 105: circuit breaker closing condition calculating circuit 106: ASR circuit 107: ACR circuit 108: PWM circuit SM: synchronous motor CB-S, CB-6, CB-42: breaker PT _1, PT _2: potential transformer HLR: ramp

Claims (2)

A circuit breaker provided between the electric power system and the motor is inserted at the timing when the frequency difference, amplitude difference and phase difference between the terminal voltage of the synchronous motor and the system voltage become almost zero, and the electric motor is made into the electric power system. In the system parallel input device for synchronous motors to be synchronized,
A first calculation means for phase-converting each of the system voltage and the motor voltage and performing coordinate conversion using the system voltage phase to calculate an orthogonal biaxial component of the motor voltage;
Second computing means for computing a phase difference between the system voltage and the motor voltage from the orthogonal two-axis component;
A phase adjusting means for generating a correction signal of a speed command value of the electric motor so that the phase difference becomes zero;
Speed adjusting means for adjusting the deviation between the speed command value corrected by the correction signal and the speed detection value to zero and outputting the current command value of the motor;
Current adjusting means for performing an adjustment operation so as to make the deviation between the current command value and the current detection value zero and outputting a PWM command;
PWM means for generating a drive signal for a switching element of a PWM inverter that starts the electric motor according to the PWM command,
At the time of starting the electric motor, the inverter is started at a driving frequency slightly lower than the system voltage frequency by the inverter, and the phase adjusting means is at a timing when the phase difference calculated by the second calculating means becomes zero. operating the amplitude difference and previous SL phase difference between the system integrated voltage and the motor voltage outputs closing command for the circuit breaker at a timing becomes zero, then cuts off the power supply to the motor by the inverter The system parallel installation apparatus for synchronous motors characterized by the above-mentioned. In the synchronous motor system parallel insertion device according to claim 1,
It said electric motor when synchronizing charged to the power grid, the synchronous motor for line parallel input and wherein the control is a to switch between the constant of the current regulating means so as not to unstable the inverter.

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