Hitachi L100 300 User manual

HAL100PID
HITACHI INVERTER
PID CONTROL
USERS’GUIDE
After reading this manual, keep it for future reference
Hitachi America, Ltd.
SJ/L100/300 SERIES

SJ100/L100 / PID / 2
CONTENTS
1. OVERVIEW 3
2. PID CONTROL ON SJ100/L100 INVERTERS 3
2-1 PID Control 3
(1) P : Proportional Control 4
(2) I : Integral Control 5
(3) D : Differential Control 5
(4) PID Control 5
2-2 PID Gain Adjustments & Control Characteristics 6
3. HOW TO USE 7
3-1 Structure & Parameters 7
(1) Control Mode 7
(2) Parameters 7
(3) Deviation Calculation 8
(4) Target Input 8
(5) Feedback Input & Setting PID Performance Area 8
(6) Scale Conversion 9
3-2 Summary of Parameters for PID Control 9
3-3 Examples of Set Up 11
(1) Parameter Set Up under Frequency Control Mode 11
(2) PID Set Up (Target & Feedback) 11
(3) Scale Conversion Factor Setting 12
(4) Target Input by Digital Input Signal 12
(5) PID Mode Selection 12
3-4 Example of Each Gain Adjustment (Kp & Ti) 13
(1) Adjustment of Proportional Gain (Kp) 13
(2) Adjustment of Integration time (Ti) & Readjustment of Kp 13
3-5 General Cautions 13
4. EXAMPLES OF ACTUAL APPLICATION 14
4-1 Constant Flow Control 14
4-2 Constant Temperature Control 15
5. INDEX 16

SJ100/L100 / PID / 3
1. OVERVIEW
SJ100/L100 series inverters have an integrated PID control function as standard. They can be used for
controls, such as constant flow control for fan & pump applications, and they have the following features.
lTarget signal can be given not only by the digital operator but also by an external digital signal, which can
be set to 16 different targets. Furthermore, it can also be given by an analog input signal (0 - 10V or 4 -
20mA).
lFeedback signal can be given to SJ100/L100 by analog voltage input (10V max.)or by analog current
input (20mA max.).
lFor the feedback signal, the performance area can be defined individually. For example 0 - 5V, 4 - 20mA
or others.
lUsing a scale conversion function, you can get actual values of target value and/or feedback value for air
flows, water flows or temperature on the display.
Please read this guide book to use the convenient PID function of the SJ100/L100 series inverters correctly
and without any trouble.
2. PID CONTROL ON SJ100/L100
2-1 PID Control
“P”in PID stands for Proportional, “I”for Integral, and “D”for Differential. The combination of
these controls is called PID control. PID control is widely used in various fields, such as the process
control of air flow, water flow, pressure, temperature and others. It controls the output frequency of the
inverter according to PID calculation, which is based on the deviation between target and feedback. The
inverter adjusts its output frequency to correct the deviation. This control block diagram is shown in Fig. 2-
1 below.




P : Proportional
operation
I : Integral
operation
D : Differential
operation
Integrated into SJ100/L100
Fan, pump, etc.
deviation
ε
Target Sensor &
Transducer
Frequency
command
Feedback (Flow, Pressure or temperature etc.)
Fig. 2-1 PID Control block diagram
Motor
Target
of
control
Load
Inverter

SJ100/L100 / PID / 4
SJ100/L100 series inverters have integrated PID control, which is indicated by the dotted line in Fig. 2-1.
You can use PID control by setting a target value and providing a feedback signal.
The example in Fig. 2-2 shows a connection diagram for ventilation flow control in a fan application.
(1) P : Proportional Control
This controls the output frequency so that output frequency and deviation have a proportional relation.
The coefficient of deviation and output frequency (expressed in %) is called Proportional Gain (Kp). This
parameter can be set under function [A71].
Fig. 2-3 shows the relationship between deviation and output frequency. If you set a high value of Kp,
the response of the system to a rapid change in deviation is fast. However, if Kpis too high, the system
can become unstable.
SJ100/
L100
Target Feedback Transducer (DC0-10V, 4-20mA)
Flow volume sensor
Fan
Motor
Fig. 2-2 Wiring example for flow control application
100% of output frequency of above figure is equivalent to maximum output frequency.
Kpcan be chosen between 0.2 and 5.0 in function [A71].
4 bit of digital
input signal
Fig. 2-3 Relation between deviation and output frequency of SJ100/L100
Max. frequency <---
100
75
50
Output
frequency
(%)
25
100
75
50
25
0
Deviation(%)
K
p
=2
K
p
=1
K
p
=0.75
Kp=0.5
Kp=0.25
02
5
0
.
.
≤
≤
Kp

SJ100/L100 / PID / 5
(2) I: Integral Control
This is a control to correct the output frequency by integrating the deviation. In the case of
proportional adjustment, a large deviation will result in a large output frequency adjustment, but if the
deviation is small, then the resulting adjustment of output frequency will also be small. However, you
cannot make the deviation zero. Integral performance compensates this problem.
Integral correction of output frequency is performed by accumulating the deviation over time, so that
eventually, the deviation is brought to zero. Integration Gain (Ki)is a coefficient that determines how
often the deviation is to be integrated. The reciprocal of integration gain is Integration Time Constant
(Ti: Ti=1/Ki).
(3) D : Differential Control
This is a control to correct the output frequency by differentiating the deviation. Since P control is
based on the current deviation and I control is based on the past deviation, there will always be a delay in
the control system. Differential control compensates for this problem.
Differential correction of the output frequency is performed in proportion to the rate of change of the
deviation. Therefore, D control corrects the output frequency rapidly when there is a rapid change in the
deviation. Differentiation Gain (Kd)is a coefficient to determine how often the deviation is to be
differentiated.
(4) PID Control
PID control is a combined Proportional, Integral and Differential control. You can achieve the best
control by adjusting the three factors, P-gain, I-gain and D-gain. Smooth control may be achieved without
any hunting by P-control; you can correct steady-state deviation by I-control; and by D-control, you can
achieve a quick response to sudden disturbances which can influence the feedback value. A large
deviation can be suppressed by P-control. A small deviation can be corrected by I-control.
(Note) Since D-control is performed based on the differentiation of
deviation, it is a very sensitive control. Therefore, it may also
react to extraneous signals and noise, and can easily lead to
unstable system control. D-control is not normally required for the
control of processes such as flow, pressure and temperature.
You must set the integration time constant (Ti) on the SJ100/L100 inverter. You can set the
time between 0.5 second and 150 seconds. When “0.0”seconds is set, NO integral control
will be performed.
You can set Kd between 0 and 100. Gain is (Fmax / 10) * set value of [A74] versus change in
deviation per second.

SJ100/L100 / PID / 6
2-2 PID Gain Adjustments & Control Characteristics
The optimal gain factors of PID vary from condition to condition, and from system to system. That
means it is necessary to set those parameters by taking into account the individual control characteristics
of your particular system. The following are the characteristics that are required for a good PID control:
lStable performance
lQuick response
lSmall steady-state deviation
You adjust each parameter Kp, Tiand Kdinside the stable performance area. Generally, when you
increase each gain (Kp, Ki, Kd) parameter (= decrease Integration time : Ti), you can obtain quick
response. But if you increase them too much, the control will be unstable, because the feedback value is
continuously increasing and decreasing, which leads to an oscillation of the control. In the worst case the
system is led to a divergence mode. (Refer to Fig. 2-4)
Following are the procedures to adjust each parameter.
(1) After changing target, response is slow --- Increase P-gain (Kp)
response is quick but unstable --- Decrease P-gain (Kp)
(2) Target and feedback do not become equal --- Decrease Integration time (Ti)
become equal after unstable vibration --- Increase Integration time (Ti)
(3) Even after increasing Kp, response is still slow --- Increase D-gain (Kd)
it is still unstable --- Decrease D-gain (Kd)
Controlled
object
time
Target
Controlled
object
NG : Divergence
Fig. 2-4 Example of good control and bad control (in case of step response)
Controlled
object
Target
NG : Damped oscillation
time
Controlled
object
Target
Good Control
time
Target
NG : Slow response, big
steady state deviation
time

SJ100/L100 / PID / 7
3. HOW TO USE
3-1 Structure & Parameters
(1) Control Mode Integrated operator A71 : 00 / 01
DOP, DRW F43 : PID SW ON / OFF
SJ100/L100 series inverters feature the following two control modes:
lFrequency control mode
lPID control mode
These can be selected by “PID function selection (A71)”.
Frequency control mode is the typical control mode of standard frequency inverters which enables
you to give a frequency command to the inverter from either the operator panel, or by analog voltage or
current, or by 4 bit digital command from the control terminals.
In the PID control mode, an output frequency is set automatically such that the deviation between
target value and feedback value approaches zero.
(2) Parameters
Fig. 3-1 shows the relation between control block diagram of PID control and each parameter. Function
numbers shown in the figure are based on the commands from the integrated operator of the inverter.
+
+

+
Selectable by
A01
Frequency
command
I Gain : A73

P Gain : A72
D Gain : A74
Operator
Multi stage setting
Maximum frequency is
considered to be
100%
Pot-meter
Analog voltage input
Analog current input
10V (20mA) is
considered to be 100%
Fig. 3-1 control block diagram of PID control
Scale
conversion
A75 Target value display
: F01
Target
Analog voltage input
Analog current input
Voltage / current
selection is done by
A76
Feedback
100%
A12
A11
0
A14
A13
Operation area
FB value display :
d04
Scale
conversion
A75
Reverse scale
conversion
A75-1

SJ100/L100 / PID / 8
(3) Deviation Calculation
Every calculation in PID control in the SJ100/L100 is based on “%”so that it can be used with
various applications and units of measure, such as pressure (N/m2), flow (m3/min), temperature (degrees)
and so on. For example, comparing target value and feedback value is based on % of target and % of
feedback full scale value.
However, there is a useful function called scale conversion function (A75). If you use this function,
you can set a target value and/or you can monitor target and feedback value in the actual units of the
specific application. Also, there is a “active range of PID”setting function (A11 - A14), which allows you to
define an area based on the feedback signal. Please refer to Fig.3-2 and Fig.3-3 for more detail.
(4) Target Input
Only one source for the target input can be chosen from the following:
lKeypad/Operator (Integrated operator, or DOP, or DRW)
l4 bits of digital input from the control terminals
lAnalog input terminals (O-L terminal or OI-L terminal)
In the case of digital input of the target value from the terminals, it is necessary beforehand to set the
required target values in functions A21 to A35. This allows you to define an array of target values. Then
you can select the one you require from that array according to the combination of the 4 bits of digital input
(binary). This is the same philosophy used for multi-stage speed control in the frequency control mode.
(5) Feedback Input & Setting PID Performance Area
Feedback signals should be given to one of the following units:
lAnalog voltage input terminal (O terminal : 10V maximum)
lAnalog current input terminal (OI terminal : 20mA maximum)
Select one of them using “Feedback input method selection [A76]”.
This feedback signal can be defined as shown in Fig.3-2 and Fig.3-3 below, so that you can achieve
suitable performance for your particular system. The “100%” shown at vertical axis is a maximum value
which is based on an internal calculation.
Fig. 3-2 Setting Active Range (A11=0, A12=0 or 100) : Example 1
100
%
010V2V020mA
(c) A13 = 25%
A14 = 75%
(a) A13 = 20%
A14 = 100% (b) A13 = 0% A14 = 50%
4mA0100%20%0
100
%
010V5V020mA10mA0100%50%0
100
%
010V2.5V020mA5mA0100%25%0
7.5V
15mA
75%

SJ100/L100 / PID / 9
As you can see from Fig 3-3, if you set parameters A11 and A12 other than “0”, you should set the target
value inside the valid range of the vertical axis. Otherwise it is not possible to achieve stable performance
because there is no feedback value. That means the inverter will either output maximum frequency or
stop, or it will output lower limit frequency continuously if it is set.
(6) Scale Conversion
Using this function, you can set and display the target value and display the feedback value in the
actual units of the process variable. Set the parameters individually relative to 100% of feedback value.
With the factory default setting, the input and display value is based on 0 - 100%.
Example : In case of (a) in Fig.3-3, 20mA of feedback corresponds to 100% of PID internal calculation. For
instance, if actual flow at 20mA of feedback is 60 [m3/ min], you set the parameter to 0.6 (=60 /
100) in function mode A75. Then you can get the actual feedback value on the monitor mode
d04, and you can also set the target value by actual value of the control system.
100
%
25
010V2V020mA
(a) A13 = 20%
A14 = 100%
A11 = 25%
A12 = 100%
4mA0100%
20%0
100
75
%
010V5V020mA
Fig. 3-3 Setting Active Range : Example 2
(b) A13 = 0%
A14 = 50%
A11 = 0%
A12 = 75%
10mA
0100%
50%0
100
%
010V2.5V020mA
(c) A13 = 25%
A14 = 75%
A11 = 25%
A12 = 75%
5mA0100%25%0
7.5V
15mA
75%
75
25
Fig. 3-4 Example of Scale Conversion
L100/
SJ100
Target Feedback
DC 4 -20mA
Fan
(a) Factory setting
Motor
unit = [%]
Monitor d01 =
0 - 100%
Monitor F01 =
0 - 100[%]
(b) A75 = 0.6
L100/
SJ100
Target
Monitor d01 =
0 - 60m3/min
Monitor F01 =
0 - 60[m3/min]
unit = [m3/min]
Feedback
DC 4 -20mA

SJ100/L100 / PID / 10
3-2 Summary of Parameters for PID Control
On the SJ100/L100 series inverters, the same function numbers are used for both frequency control
mode and PID control mode. The function name for each function is based on frequency control mode,
which is normally used for general application. Therefore, some functions have misleading explanations in
the instruction manual.
To avoid confusion, please find in below Table 3-1 the explanation of function names for frequency
control mode and PID control mode.
Table 3-1 Relation between Frequency Control Mode & PID Control Mode
Function No. Function name
Integral
Operator
Display
DOP, DRW Contents in case of Frequency
control mode Contents in case of PID control mode
D04 Monitor mode -PID Feedback monitor
F01 Monitor mode Output frequency monitor Target value monitor
A01 Monitor mode Frequency command origin setting Target value origin setting
A11 F31 External frequency setting START
(Unit : Hz)
Feedback value input corresponding %
for lower acceptance level (Unit : %)
A12 External frequency setting END
(unit : Hz)
Feedback value input corresponding %
for upper acceptance level (Unit : %)
A13 External frequency setting
START rate (Unit : Hz)
Feedback value of
lower acceptance level input(Unit : %)
A14 External frequency setting
END rate (unit : Hz)
Feedback value of
upper acceptance level input(Unit : %)
A21 - A35 F11 Multi-stage Speed 1 - 15 setting Multi-stage Target 1 - 15 setting
A71 F39 -PID mode selection
A72 P-gain adjustment
A73 I-gain adjustment
A74 D-gain adjustment
A75 Scale conversion ratio setting
A76 Origin of feedback signal selection