Bug Report: Wrong conditional flag used for AC Feed-Forward in DPC_Loopctrl.c (Vienna Rectifier / Digital Power)

[k_nedelchev]

Hello Community,

I would like to report another significant logic bug in the generated firmware libraries for the Vienna Rectifier project (specifically located in the Digital Power Control stack file BSP/DPC_FW_PACK/src/DPC_Loopctrl.c).

The Issue:

Inside the function DPC_LCT_FeedForwardCtrl(..), the firmware is supposed to evaluate whether the AC Voltage Feed-Forward task is enabled before adding the d-axis and q-axis AC feed-forward grid terms (fVd_feed_sub and fVq_feed_sub) to the current loop outputs.

However, the original ST framework code erroneously checks the DC voltage feed-forward enable flag instead of the AC one.

The Code Snippet:

c

void DPC_LCT_FeedForwardCtrl(DPC_LCT_CDC_t *pCDC_sub, float *pVd_ctrl_FF_sub, float *pVq_ctrl_FF_sub)
{
  float fVd_feed_sub = pCDC_sub->fVdFeed;
  float fVq_feed_sub = pCDC_sub->fVqFeed; 
  float fVd_ctrl_sub = pCDC_sub->fVdCurrentCtrl;
  float fVq_ctrl_sub = pCDC_sub->fVqCurrentCtrl;

  /* AC feedforward task */  
  // BUG: Checks bVDC_FF_Enable instead of bFF_Enable
  if(pCDC_sub->bVDC_FF_Enable == SET) /*!< DC voltage FeedForward Enabling */
  {
    pCDC_sub->fVdFF_ctrl = fVd_ctrl_sub + fVd_feed_sub; // d-axis - Vac Feed_Forward
    pCDC_sub->fVqFF_Ctrl = fVq_ctrl_sub + fVq_feed_sub; // q-axis - Vac Feed_Forward
  }
  else
  {
    pCDC_sub->fVdFF_ctrl = fVd_ctrl_sub; // d-axis - Vac Feed_Forward bypassed
    pCDC_sub->fVqFF_Ctrl = fVq_ctrl_sub; // q-axis - Vac Feed_Forward bypassed  
  }

  /* DQ control voltage obtained */   
  *pVd_ctrl_FF_sub = pCDC_sub->fVdFF_ctrl;
  *pVq_ctrl_FF_sub = pCDC_sub->fVqFF_Ctrl;  
}

 

The Impact:

Because of this typo/copy-paste error in the library logic, if a user enables or disables AC Feed-Forward independently in their control topology parameters, the conditional branch evaluates the wrong boolean state (bVDC_FF_Enable). This compromises the decoupled current control loop (CDC) matrix, causing severe tracking errors in the DQ frame, poor THD performance, and potential instability under fast load variations.

The Elegant Non-Intrusive Fix (Linker Wrap Method):

Since modifying the library file directly inside BSP/DPC_FW_PACK/src/DPC_Loopctrl.c will cause the fix to be overwritten every time you click "Generate Code" in CubeMX, you can use the GCC linker function wrapping mechanism to fix it safely:

1. Copy the function into a safe user code section (e.g., inside app_vienna.c between USER CODE BEGIN / USER CODE END tags) and implement the corrected flag check using the __wrap_ prefix:

c

void __wrap_DPC_LCT_FeedForwardCtrl(DPC_LCT_CDC_t *pCDC_sub, float *pVd_ctrl_FF_sub, float *pVq_ctrl_FF_sub)
{
  float fVd_feed_sub = pCDC_sub->fVdFeed;
  float fVq_feed_sub = pCDC_sub->fVqFeed; 
  float fVd_ctrl_sub = pCDC_sub->fVdCurrentCtrl;
  float fVq_ctrl_sub = pCDC_sub->fVqCurrentCtrl;

  /* AC feedforward task - FIXED FLAG CHECK */  
  if(pCDC_sub->bFF_Enable == SET) /*!< AC voltage FeedForward Enabling properly checked */
  {
    pCDC_sub->fVdFF_ctrl = fVd_ctrl_sub + fVd_feed_sub;
    pCDC_sub->fVqFF_Ctrl = fVq_ctrl_sub + fVq_feed_sub;
  }
  else
  {
    pCDC_sub->fVdFF_ctrl = fVd_ctrl_sub;
    pCDC_sub->fVqFF_Ctrl = fVq_ctrl_sub;  
  }

  *pVd_ctrl_FF_sub = pCDC_sub->fVdFF_ctrl;
  *pVq_ctrl_FF_sub = pCDC_sub->fVqFF_Ctrl;  
}

 

2. Instruct the linker to redirect all calls from the original function to your fixed version. Go to:
   Project Properties > C/C++ Build > Settings > Tool Settings > MCU/MPU GCC Linker > Miscellaneous > Other flags and add:

text

-Wl,--wrap=DPC_LCT_FeedForwardCtrl

 

Best regards,

k_nedelchev