PV system impacts at high-pen

1. PV system impacts at high-
pen
Michael Ropp, Ph.D., P.E.
Northern Plains Power Technologies
Brookings, SD USA

2. Impacts occur on two levels
• Local (Area EPS) level
• Voltage rise
• Flicker/voltage modulation
• Risk of unintentional islanding
• Impacts on voltage regulators
• Potential negative impacts on
protection/coordination
• Ground Fault Over Voltage
• System (Bulk EPS) level
• Impacts on transient performance
• Reduction in inertial response
• Mass tripping events
• Minimum generator loading
constraints
• Reduction of UFLS effectiveness
For today’s presentation, focus on two specific local issues: Load Rejection Over
Voltage (LROV), and Single-Phase Open Detection (SPOD)
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3. LROV
Why it’s a challenge: speed of detection required. LROV must typically be detected
within a few milliseconds. Thus, detection must be in the inverter and must be based
on gate blocking. 3

4. LROV and antiparallel rectifiers
• (Nearly) every inverter
contains an antiparallel
rectifier
• Antiparallel rectifiers
limit LROV to the
inverter’s Clamping
Voltage (CV)
• What about circuits with
inverters with different
CVs?
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5. SPOD
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How should an inverter detect this?

6. SPOD
• Islanding detection generally will not catch this because the inverter
is not islanded.
• Negative sequence voltage relaying
• Very low-cost—redundant relay generally can implement this.
• Would work nearly all the time, but not if there happens to be a generation-
load balance, on the open phase, on the inverter side of the open.
• Power Line Carrier Permissive (PLCP)
• Should be effective in most cases as long as signal does not cross between
phases (cross-coupling, delta transformer windings, neutral currents…).
• But where would the PLCP signal generator need to be? May not be a
feasible solution.
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