Transcript Research On Periodic Oscillation Test Equipment for

Research On Periodic Oscillation Test
Equipment for Thyristor Valves
Reporter: Liu Bufeng
TBEA Shenyang Transformer Group Co., Ltd.
TBEA Energy (India) Pvt Ltd.
2013 Nov.
1. Background Introduction
With the development of smart grid, more and more power electronic products,
such as SVC, HVDC etc., are focused and applied in power system.
Thyristor valve is the most important part of these devices, but also the most
vulnerable sector. The reliability and stability of valve will influence the
products’ prospect applied and promoted in power system.
In the real application environment, the safe and reliable turn-on and turn-off
of valve is the key during running.
2. Question Provided
To ensure PE products meet the stability and reliability requirements
during running, some tests need to be done in valve to verify the
consistency of cyclic turn-on and turn-off of thyristor valves, to ensure the
valve can bear the maximum of voltage, current, thermal intensity etc.,
and simultaneously, to examine the voltage wave when thyristor valve is
triggered uniformly and the voltage wave when BOD works because of
triggering inactivation.
To verify this, the Periodic Oscillation Test is necessary.
Under the limited test conditions, how to do the Periodic Oscillation Test?
3. Purpose of the paper
The purpose of this paper provides a simple and practical solution to
research the Periodic Oscillation Test Equipment, thus, it can meet the
requirements of cyclic triggering and blanking test under the limited test
conditions.
The paper analyses the security of service to thyristor valve in theory
based on the model of valve, and determines the minimum voltage,
current, the interval time of triggering between positive and inverse
group of valve, etc. And some matters need attention are also
mentioned.
To make the valve run in actual conditions, the equivalent test should be
done which should reflect the actual running condition.
4. Periodic Oscillation Circuit Design
(1) Principle
The test is to use the charge and discharge of capacitor and reactor to
simulate large current flowing thyristor valve.
(2) Circuit
(3) Triggering system
380V
Filtering
Synchronous
Sampling
Divide
Control
1Hz
2.5Hz
5Hz
6.5Hz
Differential
Amplifier
Pulse of positive group
Delay
Pulse of Anit-group
5. Theory Analysis
Parameters calculation:
(1) Determine the maximum values of voltage and current
Oscillating current bottom width is
The wave impedance during discharging is
The peak current during discharging is
(2) Determine the bottom width of oscillation current
If the bottom width is narrow, then the peak current during
discharging Im can be transferred large. If the bottom width is wide,
then he peak current during discharging Im can be transferred small.
(3) Determine the time interval between positive and anti-group
It is better to trigger anti-group after the positive group withstands the
reverse voltage for 1ms.
6. Application Result
(1) Test waveform
According to the test circuit, the peak
current and the wave impendance can be
different by adjusting the L value and C
value. The test is mainly to observe the
dynamic voltage-sharing during opening
and closing.
(2) Analysis of test results
a. The voltage-sharing during
opening process
b. Overshoot factor test during
shutdown
7. Matters need attention
(1) The pulses of triggering positive group and anti-group are got in the
negative half-cycle which means the power stops charging. One reason
is to avoid accidental short circuit of power, and the other reason is to
avoid the test in the charging process so that the measurement error will
be caused by uncertain magnitude.
(2) After the triggering of postive group, the reverse voltage during
shutdown is formed. The triggering of anti-group should avoid the
transient peak voltage, so the triggering should be delayed for 0.5ms to
2ms. Thus, positive group and anti-group are both tested, and the
reverse voltage after the oscillating current occurred in anti-group is
completed can connect the next positive half-cycle energy.
8. Conclusion
The above tests show that to use this periodic oscillation test
circuit to test valve under limited testing conditions has some
advantages.
(1) Test circuit consumes little energy, thus simple laboratory can implement it.
(2) Energy-saving effect is remarkable. The test has no disturbance to the grid,
and it can save space and money, thus has good economic result.
(3) Test items and parameters can be easily configured without a lot of changes.
The test is more flexible.
(4) The test circuit is simple, and the test component also has high security and
is not easy to be damaged due to the failure of the test circuit.
(5) The valve after testing via the periodic oscillation device generally has no
problem in system test.
Thanks！