JPS6042682B2 - Electric vehicle chip control system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention provides a method for keeping the conduction time of a chopper constant at startup when an electric car driven by a DC motor is digitally controlled by a control device using a small computer such as a microcomputer. Gradually increase the chopping frequency along the current pattern while monitoring the motor current, and after reaching the normal chopping frequency, increase the chopper conduction time (i.e., conduction) at a constant chopping frequency along the current pattern. This invention relates to a chopper control method that limits inrush current by controlling the flow rate (flow rate) and enables smooth startup.

Figure 1 shows the power running main circuit of a typical chopper-controlled electric vehicle.

In the figure, 1 is a current collector, 2, 3, 9, and 18 are unit switches,
14 is a weak field contactor, 4 is a high-speed flow reducer, 5 is a flow reduction resistor, 6 is a filter reactor, 10 is an electric motor element, 1
1 is a field winding, 12 is an inductive shunt, 13 is a weak field resistance,
15 is a main smoothing reactor, 16 is a free polling diode, 17 is a chopper, and 19 is a capacitor.
In the power running main circuit with this configuration, the chopper is controlled at a constant frequency in consideration of coordination with ground safety equipment, but due to the characteristics of the thyristor, there is a limit to the minimum conductivity at a constant frequency. If the train is started at a constant frequency, an excessive amount of current will flow until the main motor generates reverse starting force, causing the train to spin and become uncomfortable.

The following three methods can be considered to solve this startup problem.

(a) At startup, insert a startup resistor to suppress inrush current.

(b) Substantially reduces conduction rate as a low frequency startup method
Suppresses inrush current. (c) Weaken the motor field to suppress torque even if the motor current is large.

Among these, (a) and (b) due to the configuration and stability of the control system.
) method has been put into practical use.

An example of the starting resistor insertion method shown in (a) is shown in FIG.
In the figure, the same symbols are used for the same parts as in FIG. 1. 7 indicates a brake converter cam switch, and 8 indicates a starting resistance.

In this method, the cam switch 7 is opened at the time of starting, and the main circuit current flows through the starting resistor 8, thereby suppressing the rush current at the time of starting. After a certain period of time has elapsed after starting, the cam switch 7 is turned on and normal control is started.
This starting resistor insertion method requires a starting resistor, a brake converter cam switch, and a cam switch time-limited closing circuit in the control circuit, compared to the main circuit in the steady state shown in FIG.

The low frequency starting method (b) does not require the starting resistor and brake converter cam switch of the starting resistor insertion method (a), and the main circuit during power running is as shown in FIG.

FIG. 3 shows a block diagram of an embodiment of this low frequency starting type thyristor gate control circuit.

In the figure, 20 is a gate start signal, 21 is a power running notch command, 22 is a variable load device output, 23 is a motor current feedback amount, 24 is a reference oscillator, 25 is a frequency dividing circuit, 26 is a frequency switching circuit, and 27 is a phase shifter. , 28, 29 are timers,
30 is a current limit value pattern generation circuit, 31 is a comparison amplification calculation circuit, 32 is a thyristor gate on pulse signal, and 33 is a thyristor gate off pulse signal. Generally, a crystal oscillator with a stable oscillation frequency is used as the reference oscillator No. 24, and generates a clock signal having a frequency that is an integral multiple of the chopping frequency (hereinafter referred to as FCH).

The oscillation frequency of the crystal oscillator is considerably higher than FCH, and the frequency dividing circuit 25 divides this frequency up to FCH to improve the accuracy of the chopping frequency. 26 is a switching circuit having a switching function, which detects the rise of the output signal of the timer 28 started in synchronization with the gate start signal 20, changes the output frequency from FOH/4 to FcH/2, and changes the output frequency of the timer 29 from FOH/4 to FcH/2. It has the function of detecting the rising edge of the output signal and switching the output frequency from FcH/2 to FCH.

The current limit value pattern generation circuit 30 generates a power running notch command 21.
At the same time, a current limit value pattern corresponding to the variable load output 22 is generated, and the pattern is input to the comparison amplification calculation circuit 31.

The comparison and amplification calculation circuit 31 performs comparison and amplification calculations on this current limit value pattern and the motor current 23 as the main circuit feedback amount, and outputs the result to the phase shifter 27 . The phase shifter 27 is a switching circuit 26
At the beginning of each cycle, an on pulse is given to the chopper in synchronization with the output clock signal of the output clock signal, and a sawtooth wave is generated, and when this sawtooth wave becomes larger than the output of the comparison amplification calculation circuit 31, an off pulse is given to the chopper. This controls the conduction rate and thereby the motor current. Therefore, as shown in FIG. 4, the chopping frequency at startup is FcH/4 from startup until the output of the timer 28 rises (seconds), and thereafter until the output of the timer 29 rises (T. -t1) seconds is controlled by FCH/2, and after T2 seconds, the constant chopping frequency FCH
controlled by

This low-frequency starting method eliminates the need for a starting resistor and cam switch compared to the starting resistor insertion method as described above, and only requires adding a few new ICs to the gate control circuit, resulting in a more compact device. becomes possible.

However, due to the circuit configuration, the switching frequency must be selected from the frequency FcH/2N, which is a division of the steady chopping frequency FCH, and the chopping frequency cannot be controlled while being finely switched.

Normally, the appropriate number of switching stages is from 1 to 3 stages, but as mentioned above, frequency switching using this method is time-controlled by a timer regardless of the motor current, so when switching, the motor current spring Smooth control along the current limit value pattern is difficult due to rises and falls, and it is necessary to perform a motor load test to select the optimum value for the timer setting. As a method of controlling the frequency at startup, by providing a circuit with a frequency subtraction/switching function in the portions corresponding to the frequency switching circuit 26 and timer circuits 28 and 29 in FIG. 3, the frequency at startup can be controlled. For example, FCH/8→FcH/4→FcH/
3→FcH/2→7.

There is also a method of controlling H/3→NOFCH, but this method also relies on a timer for frequency switching timing, and is essentially the same as the method shown in Figure 3 above. Compared to the above, relatively smooth control along the current limit value pattern is possible, but the control circuit becomes complicated due to the addition of the frequency subtraction/switching circuit, which is not preferable. The present invention includes a sequence control circuit and an operational amplifier using conventional relay logic.
Analog gate control circuit using transistors etc.
A chopper control device consisting of an analog protection detection circuit is configured by a dedicated microcomputer, and when the chopper is digitally controlled, the inrush current at startup is smoothly controlled according to the current limit value pattern.

FIG. 5 is a block diagram showing an embodiment of the present invention,
In the figure, 40, 41, 42, 43, 44, 45 are analog input signals, 40 is the motor current value from the current detector, 41
is the filter capacitor voltage from the voltage detector, 42 is the motor voltage value from another voltage detector, 43 is the power running current limit command from the load variable device, 44 is the brake torque command from the brake control device, and 45 is the motor voltage value from another voltage detector. Shows the motor rotation speed obtained by frequency/voltage conversion of the output from the tacho generator.

46 is a multiplexer which has the function of selecting one from the five analog signals 41 to 45, 47 is A
The /D converter converts the analog signal selected by the multiplexer 46 into a digital signal.

The number of bits of the digital signal is determined by the number of data bits that can be handled by the CPU 5l used, and in the embodiment shown in FIG. 5, it is 8 bits. Note that the portion indicated by double lines in FIG. 5 indicates an 8-bit data line. 48 is an input port, and normally the gate of the data line is closed, and when an input command is received from the CPU 5l, each gate is opened according to this input command signal.
During this time, the CPU reads the data.

Since this input command corresponds one-to-one to each gate, there is no chance of data being mixed. For example, CPU5l
executes the command RIN48J, input port 4
8 is opened, and the CPU 5l reads the A/D converted digital signal from the A/D converter 47 via this input port. 51 is a central processing unit generally called a CPU, which reads data from an input port or memory according to a predetermined program in synchronization with a clock signal of about 2M pressure.
Writes data to the output port or memory and performs logical and arithmetic operations.

52 is a clock generator that generates a clock with a frequency N times the chopping frequency (generally several hundred Hz); 53 is R;
The OM (ReadOnlyMemOry) read-only memory 54 is RAM (RandOmAccessMe
mOry) is a memory that can be read and written. Of this memory, the ROM 53 stores programs for controlling the chopper device, and the CPU 5l controls the chopper device by sequentially executing the programs stored here. The RAM 54 stores temporary data when the CPU 51 executes a control program to determine the conduction rate of the thyristor, and also stores data when providing a timer mechanism by increasing or decreasing the number for each cycle of the chopper. Used for memory, etc. Reference numeral 55 is the main controller, and digital signals indicating the train operation modes such as forward/backward commands, power running/braking commands, and notch commands such as 1-notch, 2-notch, 3-notch, and 4-notch are output from this master controller. .

57 is an input interface circuit, which converts the digital signal (usually DClOOV) to a TTL level and at the same time insulates the DClOO■ circuit and the TTL level circuit to prevent noise from entering using relays, photocouplers, etc. .

49 is the same input port as 48.

56 is a high-speed current reducer of the chopper main circuit, a unit switch,
Interlock signals for the brake converter, reverser, weak field switch, pre-excitation contactor, etc. are displayed, and digital signals regarding the state of the main circuit of the chopper are output from these interlocks.

58 is the same input interface circuit as 57, and has the functions of level conversion and insulation.

50 is the same input port as 48 and 49.

Reference numerals 59, 60, and 61 are output ports, and data is held in each output port according to an output command from the CPU 5l.

For example, when executing the instruction ℃UT59J, CPU5
The data in the l register is held in the output port 59.
Numeral 62 is a digital phase shifter using a counter. Simultaneously with the command to turn on the chopper, data corresponding to the conduction rate is output from the CPU 5l to the output port 59, and at the same time, a trigger signal is given to the counter. It automatically starts counting down in synchronization with the next clock signal, and when the counter value reaches O, a borrow signal is generated, which becomes the chopper-off signal.

The oscillation frequency of the clock generator 63 is 2MXfcH when the number of bits is M1 and the chopper frequency is FCH. That is, M
=8, the maximum number represented by 8 bits is 7-1=
255, and this value corresponds to a conduction rate of 100%. Therefore, when the conduction rate is 50%, the CPU 5l issues a chopper-on command and simultaneously outputs 128 to the counter. The counter starts counting down in synchronization with the clock signal 63 (frequency 7 x FcH), and when it has counted 12 times (1 = ηr has passed since the on-pulse was output).
At 256×FCH, a borrow signal is output and becomes a chopper-off signal, and the conduction rate is controlled to 50%.

In reality, it takes about 150 μS for the chopper to turn off completely after the chopper off signal is output, so 7-
1 does not correspond to 100% conduction rate, but corresponds to 100% conduction rate obtained by subtracting the time required for turning off from 7-1. 64 is a one-shot multi-circuit that generates a pulse having a width equal to the off-pulse width in response to the rising edge of the borrow signal from the counter.

67 is a gate amplifier circuit, and 69 is a commutating thyristor.

65 is a one-shot multi-circuit similar to 64, and generates a pulse having a width equal to the on-pulse width.

68 is the same gate amplifier circuit as 67, and 70 is a main thyristor.

Reference numeral 66 is an output interface circuit, and main circuit configuration commands are outputted from the CPU 5l via the output boat 61, namely, forward/reverse switching command, braking conversion command, unit switch closing/opening command, weak field switch closing/opening command, preliminary excitation. Contactor closing/starting command etc. from TT'L level to DOlOOV
It has the function of level conversion and insulation at the same time.

The outline of the control of the chopper control device using the microcomputer shown in FIG. 5 is as follows.

When the control circuit power is activated by the driver's operation, the CP
U5l is written to the ROM memory 53. The programs that are located are executed sequentially starting from address O. First, the CPU 5l reads commands from the master controller 55 via the input boat 49, and according to the commands from the master controller, switches forward and backward through the output boat 61, configures the power running/braking circuit, turns on the unit switch, etc. Performs sequence control of the main circuit. This sequence control is executed while checking the interlock signal read through the input port 50. When the configuration of the main circuit is completed, the chopper conductivity is calculated based on the power running or braking pattern voltage value, motor current value, motor voltage value, and filter capacitor voltage value read through the input port 48. control. This chopper conduction rate control program is repeatedly executed once for each TCH cycle, assuming that the frequency of the chopper is TcH (=1/FcH). Of course, the processing time for one time is TCH of the chopper cycle.
Needs to be shorter. This repetitive program is executed in synchronization with the clock signal from the clock generator 52 by using it as an interrupt signal to the CPU 5l. The frequency of this clock signal is NX
fcH (N: integer), the CPU 5l interrupts the processing it has been executing and performs the interrupt processing every time an interrupt is generated by this clock signal. In interrupt processing, the CPU 5l counts the number of interrupts caused by this clock signal, and when this number reaches N, sets this count to 0 and executes the CPU control program from the beginning. Do this like this. As a result, the chopper control program is repeatedly executed once every chopper period TCH.The operation when N=4 is shown in the time chart of FIG. 6.1 represents an interrupt signal; An interrupt occurs to the CPU at a cycle of TcH/4.

2 represents the time during which interrupt processing is being executed,
When the count reaches 4 due to an interrupt at a certain time, the CPU 5l resets the count to 0 and executes the chopper control program from the beginning.

This processing is executed during periods 3, A, 3, C, 2, and E, and is interrupted by interrupt processing 3 (indicated by diagonal lines). As mentioned above, the chopper control program needs to be shorter than TCH, and the period indicated by E corresponds to the margin in which the CPU 5l waits for an interrupt signal without executing anything in the RWAITJ state. Time Tl, t2
, the count increases to 1, 2, and 3 due to the interrupt at t3, and the count becomes 4 due to the interrupt at time, so the CPU resets the count and executes the chopper control program again from A. I will do it. The conductivity calculated in control programs A, C, C, and II becomes the conductivity of the next cycle. At the beginning of the control program, an on-pulse is generated via the one-shot multi-circuit 65 by an output command to the output port 60 in FIG. 5 (as shown in FIG. 6). The CPU 5l outputs data corresponding to the conduction rate calculated in the previous cycle to the digital counter 62 via the output port 59 immediately before or after outputting this on-pulse. After a corresponding period of time has elapsed, a hello signal is output and an off pulse is generated by the one-shot multi-circuit 64 (shown at 5 in FIG. 6). The explanation so far relates to control when the chopper frequency other than during startup is a steady FCH, and if the chopper frequency is controlled at a constant FCH during startup, the ride quality will deteriorate due to torque shock due to rush current as described above. There are drawbacks. In order to solve this problem, the present invention enables smooth startup by gradually increasing the chopper frequency from a low frequency to FCH along the startup pattern at startup. In order to suppress the inrush current, it is possible to reduce the chopper's conduction rate, but the minimum conduction time of the chopper has a lower limit due to the characteristics of the thyristor and commutation circuit used, so it cannot be reduced unnecessarily, and the constant frequency FCH The minimum conductivity in this case is generally on the order of several percent.

Therefore, at startup, if the chopping frequency is lowered while keeping the flow time at the minimum flow time, the flow rate can be equivalently lowered. According to the present invention, the chopping frequency can be easily changed by changing the number of counts. That is, by counting N times,
Since it is controlled by the steady frequency FCH, the number of counts is K.
Reset the counter by incrementing it by N+K times. If the control program is executed from the beginning, the chopping frequency will be FCH x 1, and the minimum conduction rate will be αCH, . n, nX becomes blue, and as K increases, the chopping frequency also becomes minimum. The conductivity also becomes smaller. FIG. 7 shows the relationship between the increase in count K and the conduction rate. In the frequency control method at the time of startup according to the present invention, if the increase in the number of counts is K, the number of counts at the time of startup is N+
K. ．． ax, and the current limit value pattern voltage is read every cycle (the output from the variable load device is made into a relaxation pattern by the CR circuit).

) and the feedback amount of the motor current, and while the motor current value is larger than the pattern voltage value, the increase in the number of counts K is kept constant, and when the motor current value becomes smaller than the pattern voltage value, the number of counts increases. Subtract the increment K by 1 to K. ．． Set aO-1 and count number N+K! Max
-1 increases the chopping frequency.
Thereafter, the same control is repeated and the current limit value pattern voltage value is compared with the feedback amount of the motor current, and the increment K of the count number is decreased one by one until it becomes 0. During this period, the chopper flow time is the minimum flow time T5. The data output to the counter 62 via the output port 59 in FIG. 5 at the beginning of the control program is T. n. Data corresponding to n, n, that is, Tllllゝ
Out MlnO2ゞ (However, TOnyaml♂αCH9mln8
TcHl2M-AOTcH).

Therefore, at startup, the chopping frequency is FCH×−N−
There is no need to perform calculations for conduction rate control until the chopping frequency FCH gradually increases from 1 to 5 and reaches the steady chopping N+Kmax frequency FCH.

When the increment K of the count becomes 0, the chopping frequency becomes FCH, so from then on, control is performed at a constant frequency FCH, and the current limit value pattern is calculated while changing the current flow rate of the chopper by calculating the current flow rate. Controls motor current according to voltage value. In order to explain the frequency control method at startup according to the present invention, FIG. 8 shows an enlarged view of the relationship among the current limit value pattern voltage, motor current value, and chopper frequency.

In Figure 8, FcHXN/(N+KO)
When it is detected that the motor current value has become smaller than the current limit value pattern at a certain time, the count number is decreased by 1 and the frequency becomes FcHXN/(N+KO-1). Control with.

During this time, the conduction time of the chopper is constant, so the average voltage applied to the motor is equivalently (N+KO)/(N+KO
-1) Since the voltage has doubled, constant voltage control is performed using that voltage. The motor current increases by an amount corresponding to the increase in voltage, and then gradually decreases as the reverse starting force of the motor increases. While the motor current is larger than the current limit value pattern, it continues to be controlled at a constant frequency of FcHXN/(N+KO-1), but when the motor current becomes smaller than the current limit value pattern at Tokison 2, the number of counts is changed from then on. by one (N
+KO-2), and by repeating this process and changing the chopper frequency while keeping the chopper conduction time constant, the motor current is smoothly controlled along the current limit value pattern. Finally, when the increase in the count reaches 0 and the count reaches N, the chopper frequency remains constant at FCH and the conduction time of the chopper is changed to control the conduction rate, thereby changing the motor current to the limit value pattern. control according to the In this way, in contrast to the conventional startup control method, which was controlled temporally by a timer regardless of the motor current, the present invention uses the motor current value as a feedback amount and compares it with the current limit value pattern to control the chopper frequency. This enables smooth control along the current limit value pattern without the motor current spring-up or drop seen in conventional starting methods.

Further, it has various excellent effects, such as eliminating the need for complicated adjustments such as selection of the optimum value of the timer set value through motor combination tests in the conventional starting method.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing an example of the power running main circuit of a chopper-controlled electric vehicle, Fig. 2 is a circuit diagram showing an example of a starting resistance insertion method as a conventional starting control method, and Fig. 3 is a circuit diagram showing an example of a starting resistance insertion method as a conventional starting control method. A circuit diagram showing an embodiment of the low frequency starting method as a control method, FIG. 4 is a time chart explaining the operation of the low frequency starting method shown in FIG. 3, and FIG. 5 is a circuit showing an embodiment of the present invention. 6 is a time chart for explaining the present invention in detail, FIG. 7 is a diagram showing the relationship between the increase in the number of counts and the conduction rate for explaining the present invention in detail, and FIG. 8 is a time chart for explaining the present invention in detail. FIG. 3 is a diagram for explaining a control method according to the present invention. 46... Multiplexer, 47... A/D converter, 48... Input board, 51... CPU
l52...Clock generator, 53...ROMl5
4...To RN55...Main controller, 57...
...Input interface circuit, 58...Input interface, 59,60,61...Output port,
62... Counter 5 counter, 64... One shot multi circuit, 65... Gate amplifier circuit, 69...
... Commutation thyristor.

Claims (1)

[Claims] 1. In an electric vehicle in which a DC motor is controlled by a chopper, the chopper control device is configured using a microcomputer, and a clock signal generator that generates a clock signal with a frequency N times the chopping frequency of the chopper is provided, In a chopping control method for an electric vehicle in which the clock signal is counted as an interrupt signal of the microcomputer, and when the count reaches a set value, the count is cleared and the chopper control program is repeatedly executed, the chopper is activated at startup. Control is started with the set value set to N+K while keeping the conduction time at the minimum conduction time, and on the condition that the motor current becomes smaller than the current limit value pattern, the set value is reduced by a certain amount Δk and set to N+K−. By repeating similar control, the motor current is controlled according to the current limit value pattern, and when the set value reaches N, the set value is kept constant at N and the chopper frequency is kept constant. An electric vehicle chopper control method, characterized in that the motor current is controlled in a current limit value pattern by changing the chopper conduction time.