Hysteresis control technique in Power Electronics - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define the hysteresis band width variable.

Power Electronics

hysteresis_band = [1]

Drag options to blanks, or click blank then click option'

A0.1

B10

C1.0

D0.05

Attempts:

3 left

💡 Hint

Common Mistakes

Using a very large value for the hysteresis band width.

Setting the band width to zero, which disables hysteresis.

The hysteresis band width is typically a small positive value like 0.05 to control switching.

2fill in blank

medium

Complete the code to check if the output current exceeds the upper hysteresis limit.

Power Electronics

if current > set_point + [1]:

Drag options to blanks, or click blank then click option'

Aset_point

B0

Chysteresis_band

Dcurrent

Attempts:

3 left

💡 Hint

Common Mistakes

Comparing current to set_point without adding the hysteresis band.

Using zero instead of the hysteresis band.

The upper limit is the set point plus the hysteresis band width.

3fill in blank

hard

Fix the error in the condition to check if current is below the lower hysteresis limit.

Power Electronics

if current [1] set_point - hysteresis_band:

Drag options to blanks, or click blank then click option'

A>

B<

C==

D>=

Attempts:

3 left

💡 Hint

Common Mistakes

Using greater than instead of less than.

Using equality operator which is too strict.

The condition should check if current is less than the lower limit (set_point minus hysteresis band).

4fill in blank

hard

Fill both blanks to complete the hysteresis control logic for switching.

Power Electronics

if current [1] set_point + hysteresis_band:
    switch_state = [2]

Drag options to blanks, or click blank then click option'

A>

BTrue

CFalse

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' instead of '>' in the condition.

Setting switch_state to True when current is too high.

If current exceeds the upper limit, the switch should turn off (False).

5fill in blank

hard

Fill all three blanks to complete the hysteresis control logic for turning the switch on when current is below the lower limit.

Power Electronics

if current [1] set_point - hysteresis_band:
    switch_state = [2]
else:
    switch_state = [3]

Drag options to blanks, or click blank then click option'

A<

BTrue

CFalse

D>

Attempts:

3 left

💡 Hint

Common Mistakes

Using '>' instead of '<' in the condition.

Reversing True and False for switch_state.

If current is less than the lower limit, switch turns on (True), else off (False).

Practice

1. What is the main purpose of the hysteresis control technique in power electronics?

easy

A. To convert AC signals into DC signals

B. To increase the frequency of switching devices continuously

C. To keep signals within set upper and lower limits by switching devices ON or OFF

D. To measure the power consumption of a device

Solution

1. Step 1: Understand the role of hysteresis control

   Hysteresis control is designed to maintain a signal within a specific range by switching devices ON or OFF when the signal crosses set limits.

2. Step 2: Compare options with this role

   Only To keep signals within set upper and lower limits by switching devices ON or OFF describes this behavior correctly. Other options describe unrelated functions.

3. Final Answer:

   To keep signals within set upper and lower limits by switching devices ON or OFF -> Option C

4. Quick Check:

   Hysteresis control = signal limits control [OK]

Hint: Remember: hysteresis controls signal range by switching [OK]

Common Mistakes:

• Confusing hysteresis control with signal conversion
• Thinking it increases switching frequency continuously
• Assuming it measures power consumption

2. Which of the following correctly describes the switching action in hysteresis control?

easy

A. Switch ON when signal is below lower limit, switch OFF when above upper limit

B. Switch OFF when signal is below lower limit, switch ON when above upper limit

C. Switch ON and OFF randomly without limits

D. Switch ON only when signal equals the upper limit

Solution

1. Step 1: Recall hysteresis switching rules

   In hysteresis control, the device switches ON when the signal falls below the lower limit and switches OFF when it rises above the upper limit.

2. Step 2: Match options with this rule

   Switch ON when signal is below lower limit, switch OFF when above upper limit matches this exactly. Other options describe incorrect or random switching.

3. Final Answer:

   Switch ON when signal is below lower limit, switch OFF when above upper limit -> Option A

4. Quick Check:

   Switch ON below lower limit = correct switching [OK]

Hint: ON below lower limit, OFF above upper limit [OK]

Common Mistakes:

• Reversing ON and OFF conditions
• Assuming random switching
• Switching only at exact limits

3. Consider a hysteresis controller with upper limit 5A and lower limit 3A controlling current. If the current is 4A and rising, what will the controller do next?

medium

A. Ignore the current and maintain previous state

B. Switch OFF the device immediately

C. Switch ON the device immediately

D. Keep the device ON until current exceeds 5A

Solution

1. Step 1: Analyze current position relative to limits

   The current is 4A, which is between the lower limit (3A) and upper limit (5A), and it is rising.

2. Step 2: Apply hysteresis control logic

   The device remains ON until the current exceeds the upper limit (5A), then it switches OFF. Since current is rising but below 5A, device stays ON.

3. Final Answer:

   Keep the device ON until current exceeds 5A -> Option D

4. Quick Check:

   Current rising between limits = device stays ON [OK]

Hint: Device switches OFF only after exceeding upper limit [OK]

Common Mistakes:

• Switching OFF too early before upper limit
• Switching ON again unnecessarily
• Ignoring current trend

4. A hysteresis controller is designed with upper limit 10V and lower limit 8V. If the controller switches ON at 9V and OFF at 11V, what is the error in design?

medium

A. Switch ON and OFF limits do not match hysteresis band

B. Switching ON at 9V is correct

C. Switching OFF at 11V is within limits

D. No error, design is correct

Solution

1. Step 1: Compare given switching points with hysteresis limits

   The hysteresis band is between 8V (lower) and 10V (upper). The controller should switch ON at or below 8V and OFF at or above 10V.

2. Step 2: Identify mismatch in switching points

   Switching ON at 9V (above lower limit) and OFF at 11V (above upper limit) does not match the defined hysteresis band, causing incorrect control.

3. Final Answer:

   Switch ON and OFF limits do not match hysteresis band -> Option A

4. Quick Check:

   Switch points must match hysteresis limits [OK]

Hint: Switch points must align exactly with hysteresis limits [OK]

Common Mistakes:

• Ignoring mismatch in switching thresholds
• Assuming switching at any point is valid
• Confusing upper and lower limits

5. In a power converter using hysteresis control, if the hysteresis band is made very narrow, what is the likely effect on the switching frequency and system performance?

hard

A. System stops switching and remains fixed

B. Switching frequency increases, causing higher losses and possible instability

C. No change in switching frequency or performance

D. Switching frequency decreases, improving efficiency

Solution

1. Step 1: Understand effect of hysteresis band width

   A narrow hysteresis band means the signal crosses limits more frequently, causing the controller to switch ON and OFF more often.

2. Step 2: Analyze impact on switching frequency and performance

   Higher switching frequency leads to increased switching losses and can cause instability due to rapid switching.

3. Final Answer:

   Switching frequency increases, causing higher losses and possible instability -> Option B

4. Quick Check:

   Narrow band = more switching = losses [OK]

Hint: Narrow band means more switching, more losses [OK]

Common Mistakes:

• Assuming narrow band reduces switching frequency
• Thinking performance improves with narrow band
• Ignoring switching losses