The Central Electricity Regulatory Commission (CERC) order, providing relief to Suzlon for the
retrofitting of its 7,400 MW of wind energy project, has yet again reinforced the need for decisive
clarity on many critical aspects including the Low Voltage Ride Through (LVRT) requirement criteria, solution features of LVRT retrofitting, Wind Turbine Generation (WTG) certification, and the
retrofitting cost reimbursement.
That brings us to the crux of the matter: what exactly is LVRT? It’s a capability requirement in wind
power generation that pertains to fault conditions, unlike the reactive power control that applies to
normal operating conditions.
From the perspective of grid security, LVRT assumes critical significance. Given the growing
prominence of wind farms in India, it is imperative to ensure that advantages of the conventional
power plants are not lost during systemic faults. That’s precisely why the Central Electricity
Authority (CEA) spelt out the mandatory LVRT capability requirements for Indian wind turbines.
Why is the regulation swimming in murky waters?
This is the outcome of a host of thorny issues plaguing implementation. First and foremost, LVRT
operation varies with the turbine type in question which can be either Type I, which is Fixed speed
induction, Type II, wound rotor induction, Type III, Doubly Fed induction or Type IV, Wound rotor
synchronous. Type I and Type II call for external grid support. Type III, the most popular, and highly
sensitive to grid faults, and Type IV, with its full scale power converters come largely equipped with
credible software-driven LVRT capabilities.
Now, LVRT provision, as the experts contend, is not possible for legacy turbines of up to 700 kW.
The CEA was supposed to probe deep into this aspect through a feasibility study and present its findings six months from the issue of the CERC order dated January 1, 2016, that called for LVRT
implementation for all wind turbines (except Stall Types) commissioned before April 15, 2014, with
installed capacities of 500 kW or more.
For more than 700 kW turbines, LVRT is possible as a retrofit solution. But this route is marked with
numerous hurdles: in some cases, it may call for structural modifications to sustain the mechanical
stress of LVRT, in other cases, the retrofit may cause increased load on the drive train and allied
components and unless the design is commensurately high-margin, it is bound to invite a fault
situation.
The industry has already appealed to the government to adopt a more practical stance about the
LVRT diktat considering the cost considerations, additional investments and the need for prudent
compensation mechanisms to arrest the effective loss following the retrofit. Besides, there are a few
unwanted situations in the offing. Like for instance, the retrofit may invalidate the type certification
of the turbine and affect the insurance claim in case of any major damage.
The industry has also put forth an argument that the absence of LVRT does not cause wind
generation loss. The non-availability of well-equipped wind evacuation systems, it contends, is
responsible for loss of wind generation during grid turbulence and cascade tripping of windmills.
The Ministry of New and Renewable Energy (MNRE) has already recommended an action plan, by
directing WTG manufacturers to apply for LVRT certification from a globally accredited testing body
and imposing various penalties for non-compliance.
As the Suzlon petition has duly highlighted, the onus is now on the CEA to furnish the pending
feasibility study for the LVRT installation in turbines of installed capacity less than 500 kW. Without
the study, imposing any mandate and penalty would only prove counterproductive.
Involving all stakeholders in the thought churn – manufactures as well as leading testing agencies
like DNV GL – will help arrive at a feasible solution in this sunrise space of renewable energy,
absolutely critical in the context of India’s burgeoning power requirements.
retrofitting of its 7,400 MW of wind energy project, has yet again reinforced the need for decisive
clarity on many critical aspects including the Low Voltage Ride Through (LVRT) requirement criteria, solution features of LVRT retrofitting, Wind Turbine Generation (WTG) certification, and the
retrofitting cost reimbursement.
That brings us to the crux of the matter: what exactly is LVRT? It’s a capability requirement in wind
power generation that pertains to fault conditions, unlike the reactive power control that applies to
normal operating conditions.
From the perspective of grid security, LVRT assumes critical significance. Given the growing
prominence of wind farms in India, it is imperative to ensure that advantages of the conventional
power plants are not lost during systemic faults. That’s precisely why the Central Electricity
Authority (CEA) spelt out the mandatory LVRT capability requirements for Indian wind turbines.
Why is the regulation swimming in murky waters?
This is the outcome of a host of thorny issues plaguing implementation. First and foremost, LVRT
operation varies with the turbine type in question which can be either Type I, which is Fixed speed
induction, Type II, wound rotor induction, Type III, Doubly Fed induction or Type IV, Wound rotor
synchronous. Type I and Type II call for external grid support. Type III, the most popular, and highly
sensitive to grid faults, and Type IV, with its full scale power converters come largely equipped with
credible software-driven LVRT capabilities.
Now, LVRT provision, as the experts contend, is not possible for legacy turbines of up to 700 kW.
The CEA was supposed to probe deep into this aspect through a feasibility study and present its findings six months from the issue of the CERC order dated January 1, 2016, that called for LVRT
implementation for all wind turbines (except Stall Types) commissioned before April 15, 2014, with
installed capacities of 500 kW or more.
For more than 700 kW turbines, LVRT is possible as a retrofit solution. But this route is marked with
numerous hurdles: in some cases, it may call for structural modifications to sustain the mechanical
stress of LVRT, in other cases, the retrofit may cause increased load on the drive train and allied
components and unless the design is commensurately high-margin, it is bound to invite a fault
situation.
The industry has already appealed to the government to adopt a more practical stance about the
LVRT diktat considering the cost considerations, additional investments and the need for prudent
compensation mechanisms to arrest the effective loss following the retrofit. Besides, there are a few
unwanted situations in the offing. Like for instance, the retrofit may invalidate the type certification
of the turbine and affect the insurance claim in case of any major damage.
The industry has also put forth an argument that the absence of LVRT does not cause wind
generation loss. The non-availability of well-equipped wind evacuation systems, it contends, is
responsible for loss of wind generation during grid turbulence and cascade tripping of windmills.
The Ministry of New and Renewable Energy (MNRE) has already recommended an action plan, by
directing WTG manufacturers to apply for LVRT certification from a globally accredited testing body
and imposing various penalties for non-compliance.
As the Suzlon petition has duly highlighted, the onus is now on the CEA to furnish the pending
feasibility study for the LVRT installation in turbines of installed capacity less than 500 kW. Without
the study, imposing any mandate and penalty would only prove counterproductive.
Involving all stakeholders in the thought churn – manufactures as well as leading testing agencies
like DNV GL – will help arrive at a feasible solution in this sunrise space of renewable energy,
absolutely critical in the context of India’s burgeoning power requirements.