in my simulink,used for voltage stabilization which used dvr in flc,here the output have some issues the vload and vinj? so can u help me, vload would be proper sine wave?

Answer 1

[Umar]

Hi @Faria,

I looked closely at your Simulink setup and the waveforms you shared, after doing thorough research — the noisy Vinj and slightly distorted Vload are very likely caused by the powergui sample-time configuration. That’s a common issue when modeling DVRs or other power-electronic systems.

Right now, it looks like your model is using a large discrete step (around 0.1 s), which is far too coarse for the fast switching dynamics in a DVR. You can fix this by setting the powergui block to Discrete mode and choosing a much smaller sample time, typically in the range of 5e-6 s to 2e-5 s. Then, go into Simulation → Configuration Parameters → Solver and match the fixed-step size to the same value.

Once you do that, re-run the simulation and zoom in on the Vload waveform. You should see a clean sine wave again — only small, short transients during DVR injection. The Vinj waveform will still show rapid switching (that’s normal for a compensator), but the noise-like distortion should disappear.

In short:

• Discrete powergui with Ts ≈ 5e-6 s
• Fixed-step solver with same step size
• Keep controller and PWM sample times synchronized

That change alone usually resolves the “weird noisy injection” issue you mentioned. If not, the next step would be checking how the FLC (fuzzy logic controller) and PWM blocks are sampled relative to your main system — but let’s stabilize the powergui first.

Once your simulation runs cleanly, Vload should appear as a proper sine wave, while Vinj just handles compensation transients.

Hope this helps!

[Faria]

[Faria]

umar i am done with this as far said,but the vload and vinj still same condition.i dont know how to sort out this problem, can u help me please.

[Umar]

Hi @Faria,

I can see you followed my advice and changed your powergui from 1e-5 seconds to 5e-6 seconds but looking at your latest screenshot of waveforms, Vinj is still showing the same noisy pattern and Vload still has distortion. That's frustrating.

Looking at your Vinj waveform, those jagged, noisy patterns are classic unfiltered PWM switching harmonics which means that your DVR is outputting raw PWM signals directly, and all that high-frequency noise is going straight into your injection point and bleeding into your load voltage.

Here's what you need to do. Keep your powergui at 5e-6 seconds as it is - open up that DVR subsystem and try adding

an LC filter inside it. So, double-click on the cyan DVR block in your main model. This will open the subsystem so you can see what's inside - you'll see your inverter, fuzzy logic controller, PWM generator, and other components.

Now you need to find where the inverter output connects to the rest of the circuit. This is the critical spot where you'll add the filter. According to MathWorks documentation, for three-phase inverter systems, you should use the Three-Phase Series RLC Branch block. Go to your Simulink Library Browser and navigate to Simscape > Power Systems > Passive. Look for "Three-Phase Series RLC Branch" and drag one of these blocks into your DVR subsystem.

Double-click on the Three-Phase Series RLC Branch block to configure it. Set the Branch type parameter to "LC" - this gives you just the inductor and capacitor without a resistor. For the inductance, set it to 0.002 (that's 2 millihenries). For the capacitance, set it to 20e-6 (that's 20 microfarads). These values are typical for DVR applications based on MathWorks power electronics examples.

Connect this LC branch in series between your inverter output and wherever that connects to your injection transformer. The LC filter works by passing your fundamental frequency (50 or 60 Hz) while blocking the high-frequency PWM switching harmonics. The cutoff frequency of this filter will be around 1-2 kHz, which is perfect - well above your fundamental but well below your PWM switching frequency.

Now here's something else from MathWorks documentation - if after adding the LC filter you see any ringing or oscillations in your Vinj, you might need to add a small damping resistor. You can do this by changing the Branch type from "LC" to "RLC" and setting the Resistance to around 0.5 ohms. This prevents the filter itself from oscillating, but try it without the resistor first.

While you're inside the DVR subsystem, double-check your Fuzzy Logic Controller and PWM Generator blocks. Both should be set to discrete-time mode with sample time 5e-6 - not inherited and not continuous. They need to match your powergui timing.

For your main Configuration Parameters, make sure you have Fixed-step as the solver type, use either ode1 or discrete as the solver, set the fixed-step size to 5e-6, and make sure "Treat each discrete rate as a separate task" is unchecked.

The reason this filter is so essential comes from basic power electronics principles. Your PWM inverter generates the desired 50/60 Hz sine wave plus a whole bunch of harmonics at the switching frequency and its multiples. Without a filter, all of those harmonics show up in your injection voltage. An LC filter is specifically designed to smooth out these harmonics and give you a clean sine wave output.

After you add this LC filter inside the DVR subsystem, run your simulation again. You should see Vinj transform from those noisy, jagged waveforms into smooth three-phase sine waves. And because Vinj feeds into Vload through your series connection, Vload will automatically become perfectly sinusoidal too.

The key thing to understand is that adjusting sample times and solver settings outside the DVR subsystem won't fix this issue by themselves. You have to actually modify the circuit inside the DVR by adding the filter components. The sample time controls how often Simulink calculates values, but the LC filter is the actual electrical component that physically smooths the waveform.

Try adding this filter and let me know what happens.

[Faria]

[Faria]

Umar see,but i applied the rlc branch in inside dvr, here is the improve version, can u see there is still noisy here. i dont understand how could i sort out this problem, can u help me. can i get ur email address please. i need ur help

[Umar]

Hi @Faria,

I understand you’d like to continue this discussion directly, but MathWorks policy doesn’t allow sharing personal contact details or continuing support through email. It’s best — and actually required — to keep all technical help on the forum so others can learn from it too.

Now let me address your latest comments.

I went through your latest plots carefully. You’ve definitely made progress — the setup looks closer to what it should be — but the waveforms still show the same issue Umar mentioned earlier. The Vinj trace is still noisy and jagged, which means the inverter’s PWM switching harmonics are not being fully filtered out. The short burst around 0.12–0.16 seconds looks like a resonance effect, probably because the RLC filter isn’t placed or tuned correctly.

In plain terms, the inverter output is still feeding high-frequency PWM components into the system. This usually happens when the filter is wired incorrectly or the scope is measuring the wrong node. Please make sure your RLC branch is in series between the inverter output and the injection transformer, not in parallel. Also check that your scope is connected after the filter.

If the connection is correct, try setting a small damping resistance (around 0.5 ohms) in the RLC branch to reduce ringing. The sample time change to 5e-6 s was the right move — keep that setting as is. Once the filter is properly placed and tuned, Vinj should become a clean sine wave and the load voltage will smooth out automatically.

If you can, please post a screenshot of your DVR subsystem wiring and the RLC parameters on the forum — it’ll be easier to spot what’s missing.

Hope this helps!

[Faria]

look umar. how i can sort out this problem

[Umar]

Hi @Faria,

Thanks for sharing the screenshot, now I see exactly what's wrong now. Your RLC filter is connected in parallel with the 3-Phase Breaker, and both are feeding into BUS 3. This means the PWM noise from your inverter is bypassing the filter completely through the breaker path. That's why you're still seeing the noisy waveforms - the filter can't clean a signal that doesn't pass through it.

The fix is simple but critical: you need to rewire the RLC filter so it's in series between your inverter output and the transformer like mentioned before. If you look closer, your signal path looks like this:

Inverter > Series R Branch > BUS 3 < (both breaker and RLC connect here in parallel) > Transformer

It needs to be a straight line with no parallel branches:

Inverter > Series R Branch > RLC Filter >Transformer > Load

Here's what you need to do:

1. Disconnect both the 3-Phase Breaker and RLC filter from BUS 3. Delete those wires.

2. Connect the Series R Branch output directly to the RLC filter input (terminals A, B, C).

3. Connect the RLC filter output directly to the 3-Phase Transformer primary side.

4. Either remove the 3-Phase Breaker completely for now, or place it in series before the RLC filter (not creating any parallel path).

5. Double-check your RLC settings: Change it to RLC type (not just LC), set R = 0.5 ohms, L = 0.002 heneries, C = 20e-6 Farads. The small resistance will stop the ringing you're seeing around 0.12-0.16 seconds.

6. Make sure your Vinj scope is measuring after the RLC filter, not before it.

Think of it like this: if you put a water filter on one pipe but leave a second pipe without a filter, dirty water just flows through the unfiltered pipe. You need only one path, and it must go through the filter.

Once you rewire it correctly with the filter in series (no bypass paths), your Vinj should become a clean three-phase sine wave and Vload will smooth out automatically as mentioned before. Keep your powergui and solver settings at 5e-6 seconds - those are correct.

If you're still having issues after making these changes, post another screenshot of your DVR subsystem so we can see the new wiring.

You are very close solving this problem.

Hope this helps!

[Faria]

umar is this ok? i dont understand actually how to connect , can u give me screenshot of this connection. this will help me, u said direct rlc to transformer but what about vinj? give me pic

[Faria]

umer kindly help me

[Faria]

please give me simulink ss sothat i can see where i have to change the connection, otherwise i cannot understand. help me with this please.

[Umar]

Hi @Faria,

Sorry for the late response because working with clients all day long. I traced through the model you shared and drew a corrected wiring sketch (reference: please see attached) that uses exactly the blocks already in your model since not having access to Matlab Simulink. Short version: the inverter outputs (A, B, C) must each go only through the series path (Series R → Three-Phase Series RLC → Breaker → Transformer primary). Right now there are extra parallel wires that let the converter bypass the RLC filter, so the PWM is reaching BUS 3 unfiltered.

Why this matters (very briefly): The Three-Phase Series RLC Branch is a balanced, series R–L–C branch intended to be placed in series with each phase so it can filter the converter's PWM before injection. If you place a shortcut around it the filter is bypassed and it can't do its job. The Two-Level Converter block represents the inverter outputs (A, B, C). Those outputs should feed the series path, not be tied directly to the transformer/bus in parallel. The Three-Phase Breaker / Circuit Breaker belongs in series when you want to switch the injection path; it's not a recommended shunt or parallel path for the filter. Measure Vinj with the Three-Phase V-I Measurement block placed after the RLC and before the breaker/transformer so you see the filtered injection voltage. For PWM fidelity use a fixed (small) step / discrete powergui sample time — small step = better capture of switching harmonics (as I suggested 5e-6 s). See powergui settings for discrete sample time behavior.

Step-by-step wiring (use these exact blocks in your model): (Do each step in order, then run a quick trace on each phase to confirm no bypass.)

1. Remove bypass wires Delete any direct wires that connect the converter outputs (A, B, C) directly to BUS 3 or to the transformer primary that do not go through the Series R and the Three-Phase Series RLC Branch. Your model currently shows those extra connections — remove them.

2. Connect converter → Series R Branch Block: Two-Level Converter → connect its A, B, C electrical outputs to the inputs of the Series R Branch (if you used the single-phase Series R Branch per phase, connect phase-to-phase accordingly).

4. Series R Branch → Three-Phase Series RLC Branch Block: Three-Phase Series RLC Branch — set Branch type = R + L + C (series) and enter the values I suggested previously: R = 0.5 ohm, L = 0.002 Henry , C = 20e-6 Farad Connect the outputs of the Series R Branch to the inputs (A, B, C) of this RLC block.

5. Place the measurement (Vinj) Block: Three-Phase V-I Measurement — connect it to the node immediately after the RLC block (between RLC and breaker/transformer). Label its scope output Vinj. If the V-I block outputs Simscape physical signals, put a PS-Simulink Converter between the measurement and your Simulink Scope.

6. RLC → Breaker → Transformer primary Block: Three-Phase Breaker (or Circuit Breaker (Three-Phase)) — wire the RLC outputs to the breaker inputs; wire breaker outputs to the transformer primary terminals (A→A1, B→B1, C→C1). Make these terminal-to-terminal connections explicit so phase ordering matches across converter→R→RLC→transformer.

7. Transformer secondary → BUS 3 / Load Keep BUS 3 connected to the transformer secondary as your injection point. Confirm there are no hidden junctions tying the converter outputs into BUS 3 elsewhere.

8. Final trace / sanity check For each phase (A, B, C) trace the wire: Converter output → Series R → RLC → Breaker → Transformer primary → secondary → BUS 3. That single path per phase is required. Look for small black junction dots — they indicate forks/branches; delete any that create a second path from converter to BUS 3.

Solver & powergui settings:Put powergui in the model root (if not already). If you run in Discrete mode, set its Sample time to match the model fixed step. Powergui exposes the Sample time (s) parameter when Simulation type = Discrete.

Model Configuration Parameters → Solver: set Type = Fixed-step, Fixed-step size = 5e-6 (Umar's recommendation). Small steps capture PWM switching content. If simulation is too slow, you may increase the step but verify the PWM frequency components remain represented.

A few practical tips (from experience)

• Phase ordering matters: swapping phases between any two blocks will inject phase-shifted voltages. Keep A→A1, B→B1, C→C1 consistently.

• If you still see HF at Vinj, zoom in on the wiring for overlooked short-circuits; then try increasing R in 0.1 ohm steps for damping only after confirming wiring is correct.

• If your measurement signals are weird or zero, confirm the V-I Measurement block's V_nom and P_base are sensible for your system and that any PS→Simulink conversions are in place.

Place Three-Phase V-I Measurement at node after RLC and before breaker; label scope channel 'Vinj'. Set fixed-step = 5e-6 s in Solver and discrete powergui sample time to match.

References (MathWorks docs I used while checking block behavior)

• Three-Phase Series RLC Branch block (use Branch type = R+L+C).
• Two-Level Converter block (three-phase converter models / switching devices).
• Three-Phase Breaker / Circuit Breaker blocks (place in series).
• Three-Phase V-I Measurement block (measure voltages/currents; use PS→Simulink converters when needed).
• powergui sample time & solver comments (use discrete mode + matched sample / fixed-step solver for PWM fidelity).

Hope this helps and resolves your problem completely.

[Faria]

Hi umar, is this connection is right. i think i made mistake in connection of transformer, i really dont understand how to connect each point to each point. can u help me with this please.

[Faria]

umar what about this connection? is this ok, the breaker transformer vinj connection? i am tired with doing this, please help me

[Faria]

this is the output

[Umar]

Hi @Faria,

Look at the hand-drawn sketch I attached. This is EXACTLY what your Simulink model needs to look like. No variations, no "I think this is the same," no shortcuts. Wire it exactly as shown and your problem will be solved. Let me tell you why I'm confident about this.

What the Hand-Drawn Diagram Shows

Control/Signal Path * Vload → Controller1 (outputs V+, ωt) → Uref/ωt/P → PWM generator 2-level → 2-Level Converter (g, BL inputs) * DC supply connects to the converter's DC terminals

Power Path (THIS IS THE CRITICAL PART) * 2-Level Converter outputs: A, B, C * These go to Series R Branch * Series R outputs go to Three-Phase Series RLC Block (labeled "RLC" with terminals a, b, c on input side, A, B, C on output side) * RLC outputs go to Three-Phase V-I Measurement (labeled "Scope" - this measures Va, Vb, Vc which is your Vinj) * V-I Measurement outputs go to 3-Phase Breaker (terminals a, b, c inputs, A, B, C outputs) * Breaker outputs go to 3-Phase Transformer primary side at numbered terminals (1, 2, 3 are A1+, B1+, C1+) * Transformer secondary (A2, B2, C2) connects to BUS 3 V injection (the green block) * BUS 3 connects through contact/RC to ground Notice the hand-drawn diagram shows ONE SINGLE PAT per phase. No branches, no splits, no parallel wires.

The Filter Calculation (Bottom of Hand-Drawn Sketch)

My handwritten notes show: Rz = 0.5 ohm, Lz = 0.002H, Cz = 20e-6F fc ≈ 1/(2π*square root of LC) = 1/(2π* square root of (0.002H)(20e-6F)) ≈ 796Hz

Here's what it means: your RLC filter has a corner frequency around 796 Hz. The fundamental power frequency (50 or 60 Hz) is way below this, so it passes through cleanly. But your PWM switching frequency (typically 2-10 kHz) is way above 796 Hz, so the filter heavily attenuates it. The R = 0.5Ω provides damping to prevent resonance and ringing. This is exactly how you design a series filter for PWM converters - textbook correct.

The note at the bottom says: "So, the filter attenuates components well above ~800Hz. This is crucial to make sure PWM switching (typically several kHz) doesn't leak through, and R=0.5Ω provides damping to reduce ringing."

What Your Vinj Scope Should Look Like After Following This Diagram

Right now your Vinj (bottom scope in your screenshot) looks like garbage - it's full of high-frequency noise, spikes, and jagged edges. That's PWM switching noise getting through because your filter is bypassed. After you wire it exactly like the hand-drawn diagram, your Vinj scope should show:

• Three smooth sinusoidal waveforms (yellow, blue, orange for phases A, B, C)
• 120 degree phase separation between the three phases
• Zero high-frequency content- no spikes, no jagged edges, no PWM noise
• Clean peaks and valleys - symmetric, smooth curves
• Stable amplitude throughout the simulation

Think about your top scope (Vabc) - see how clean those sinusoids are? Your Vinj should look EXACTLY like that but at the voltage level determined by your transformer and control system. If Vinj has ANY noise resembling what you're seeing now, the wiring is still wrong.

My Opinion: Will This Solve Your Problem?

First, the hand-drawn diagram enforces series-only topology. Every phase goes through the exact same chain: Converter → R → RLC → Measurement → Breaker → Transformer. No parallel paths exist. This means every single ampere of converter current MUST flow through the RLC filter. There's no way for PWM noise to bypass it.

Second, the filter math is perfect. The 796 Hz corner frequency is in the sweet spot - high enough to pass 50/60 Hz fundamental, low enough to kill switching harmonics. With the damping resistor, this filter will work exactly as intended. Third, the V-I measurement is correctly placed. It's after the RLC block, so it measures the filtered voltage. That's what Vinj means - injection voltage. You want to see what voltage you're actually injecting into the system, which is the filtered output, not the raw converter output.

Fourth, all the Simulink blocks shown are the correct blocks for this application. The Three-Phase Series RLC Branch block is literally designed for this exact use case - series filtering in three-phase systems. The documentation confirms it. Same with the breaker (series operation), the V-I measurement (voltage sensing), and the converter (three-phase two-level topology).

Your current model fails because you have bypass wires. Looking at your Simulink screenshot, I can see wires going from the converter to multiple places simultaneously. That's the problem. The hand-drawn diagram eliminates all of those.

Exact Implementation Steps

I'm going to be very specific because you said you're tired of this and just want it to work:

Step 1: Open your Simulink model. Press Ctrl+A to select everything. Look at the 2-Level Converter block. See all the wires coming out of terminals A, B, C? Here's what you do: delete every wire that doesn't go directly to the Series R Branch. If a wire goes from the converter to the breaker, delete it. If it goes to the RLC directly, delete it. If it goes to the transformer, delete it. Only keep wires that go from converter to Series R Branch.

Step 2: Now trace each connection in order. Converter A, B, C connect to Series R inputs. Series R outputs connect to RLC terminals a, b, c (lowercase letters). Make sure your RLC block settings are: Branch type = "R + L + C", R = 0.5, L = 0.002, C = 20e-6. Double-click the block and verify these exact numbers.

Step 3: RLC outputs (terminals A, B, C - uppercase letters) connect to Three-Phase V-I Measurement inputs. This block should output three signals (Va, Vb, Vc). These signals are your Vinj. Connect them to a scope - label this scope "Vinj" so you know what you're looking at. If the block outputs Simscape physical signals (those wavy lines), insert PS-Simulink Converter blocks before the scope.

Step 4: V-I Measurement outputs (the electrical terminals, not the signal outputs) connect to 3-Phase Breaker inputs (a, b, c). Breaker outputs (A, B, C) connect to transformer primary. BE VERY CAREFUL HERE: Connect A to terminal 1 (A1), B to terminal 2 (B1), C to terminal 3 (C1). If you swap phases here, your injection will be phase-shifted and nothing will work right.

Step 5: Transformer secondary connects to BUS 3. Your existing connection to contact/RC and ground stays the same.

Step 6: Zoom out. Look at the entire model. For each phase, visually trace the path from converter to ground. You should see: Converter → Series R → RLC → V-I → Breaker → Transformer → BUS 3 → RC → Ground. ONE path. No branches. No junctions. If you see a junction dot (that little black circle where wires split), you have a problem. Delete whatever wire is creating the bypass.

Step 7: Solver settings. Go to Model Configuration Parameters → Solver. Set Type = Fixed-step, Fixed-step size = 5e-6. This gives you a 5 microsecond time step, which is small enough to capture PWM switching at several kHz. Then place a powergui block in your model (if you don't have one). Set its Simulation type = Discrete, Sample time = 5e-6 (same as your fixed-step size).

Step 8: Run the simulation. Watch the Vinj scope. If you see clean sinusoids, you're done. If you still see noise, you missed a bypass wire somewhere. Go back to Step 1 and be more aggressive about deleting wires.

If you wire your model exactly like the hand-drawn diagram - and I mean exactly, not "basically the same" - your problem is solved. The Vinj scope will show smooth sinusoids. The filter will work. The system will behave correctly. One more thing: don't add anything extra. Don't try to "improve" the diagram. Don't add measurement points that split wires. Don't connect things in parallel "just to see what happens." The diagram shows the minimum necessary connections for this topology to work. Anything extra will create problems.

Copy the hand-drawn diagram wire-for-wire into Simulink and you're done. Let me know if you get clean Vinj after this. If you're still seeing noise, take a screenshot of the entire model (zoomed out so I can see everything) and I'll find the bypass wire you missed.