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Supporting reactive power from renewables is key to preventing blackouts, but who pays?

       The CEA requires projects to have reactive capacity equal to 33% of installed generating capacity.
        The quest for energy security and clean energy has led to significant growth in renewable energy capacity in India. Among renewable energy sources, solar and wind power are both sources of intermittent power that have increased significantly and must provide reactive power compensation (grid inertia) and voltage stability to ensure grid security.
       The share of solar and wind power in total installed capacity has risen to about 25.5% as of December 2022 from less than 10% at the end of 2013, according to Mercom India Research.
        When renewable energy has much lower grid penetration, it can be plugged in or out without significantly impacting grid stability. However, as the integration of renewable energy sources into the power grid increases, any deviation will seriously affect the stability and reliability of the power system.
        Reactive power services are used to ensure that voltage levels remain within specified limits. Voltage maintains the physical transfer of power from the generator to the load. Reactive power will affect the system voltage, thereby significantly affecting the security of the network.
       The government took the steps this year after various power loss incidents threatened the national grid.
        The Central Electricity Authority (CEA) recently reported 28 incidents of grid frequency deviation from set limits since January 2022, resulting in the loss of over 1,000 MW of renewable energy. This heightens concerns about more frequent power outages.
       Most of the reported events relate to overvoltages during switching operations, low-frequency fluctuations of renewable energy sources and faults near renewable energy complexes.
       Analysis of these events shows that insufficient reactive power support from variable renewable energy sources is one of the contributing factors in both static and dynamic conditions.
        Solar and wind power projects account for nearly 63% of the country’s installed renewable energy capacity, but they violate the CEA requirement that reactive power account for 33% of a project’s generating capacity, especially in the northern region. In the second quarter of 2023 alone, India produced 30 billion units of solar energy.
       The CEA has since directed all renewable energy developers who applied for connection by April 30, 2023, to comply with the CEA’s connection rules by September 30 or face shutdown.
       According to the regulations, support for dynamically varying reactive power is required during low voltage (LVRT) and high voltage (HVRT) transmission.
        This is because fixed power capacitor banks can only provide reactive power support under steady-state conditions and gradually provide support after a delay period. Therefore, providing dynamically changing reactive power support is critical to ensure network stability and security.
       Dynamic support allows reactive power to be supplied or extracted within milliseconds to prevent failures during current/voltage overloads.
        Mercom, the system operator of GRID Controller in India, told Merccom: “One of the reasons for low voltage, even 85% or less of the rated value, is the inability of solar or wind generators to provide dynamic reactive power support. Aggregation Station. For solar projects, as the solar radiation input into the grid increases, the load on the output transmission main lines increases, which in turn causes the voltage at the aggregation substation/renewable generator connection point to drop, even below the standard 85% weighing voltage.”
        “Solar and wind projects that do not meet CEA standards may malfunction, resulting in severe generation losses. Likewise, load shedding of utility wires may in turn cause high voltage conditions. In this case, wind and solar generators will not be able to provide adequate power.” dynamic reactive power support is responsible for the voltage drop.”
        One renewable energy project developer interviewed by Mercom said fluctuations and outage problems occur in the absence of grid inertia or reactive power, which in most regions is provided by the ability to provide reactive power. Thermal or hydropower projects are supported. And also drawing it from the grid as needed.
        “The problem arises particularly in regions like Rajasthan, where the installed renewable energy capacity is 66 GW, and Gujarat, where 25-30 GW is planned in the Kafda region alone,” he said. There are not many thermal power plants or hydroelectric power plants. plants that can maintain reactive power to avoid grid failures. Most of the renewable energy projects built in the past never took this into account, which is why the grid in Rajasthan breaks down from time to time, especially in the renewable energy sector.”
       In the absence of grid inertia, thermal power or hydropower projects must install a variable compensator that can supply reactive power to the grid and extract reactive power when necessary.
        The system operator explained: “For renewable energy projects, a capacity factor of 0.95 is quite reasonable; generators located away from the load center should be able to operate from a power factor of 0.90 lagging to a power factor of 0.95 leading, while generators located near the load center should be able to operate from 0.90 s lagging power factor up to 0.95 with leading power factor From +0.85 to -0.95 with leading. For a renewable energy generator, a power factor of 0.95 is equivalent to 33% of the active power, which is reactive power. capabilities that must be provided within the rated active power range.”
        To solve this pressing problem, designers are advised to install FACTS (Flexible AC Transmission System) devices such as Static VAR Compensators or Static Synchronous Compensators (STATCOM). These devices can change their reactive power output more quickly depending on the operation of the controller. They use insulated gate bipolar transistors (IGBTs) and other thyristor controls to provide faster switching.
       Because the CEA wiring rules do not provide clear guidance on the installation of these devices, many project developers have not taken into account the obligation to provide reactive power support and have therefore factored its cost into the bidding process for many years.
        Existing renewable energy projects without such equipment require backup power from inverters installed in the system. This ensures that even if they are generating power at full load, they still have headroom to provide some lag or lead reactive power support to prevent the interconnect voltage point from exceeding acceptable limits. The only other way is to perform external compensation at the factory terminals, which is a dynamic compensation device.
       However, even with only power available, the inverter goes into sleep mode when the grid goes off, so a static or variable dynamic power factor compensator is required.
        Another renewable energy project developer said, “Earlier, developers never had to worry about these factors as they were mostly decided at the substation level or in the Indian power grid. With the increase in renewable energy coming into the grid, developers have to set such factors.” For an average 100 MW project, we need to install 10 MVAr STATCOM, which can easily cost anywhere from Rs 3 to 400 crore (approximately US$ 36.15 to 48.2 million) and considering the cost of the project, this is a tough price to pay.”
       He added: “It is expected that these additional requirements on existing projects will be taken into account in line with changes to the legal terms of power purchase agreements. When the Grid Code was released in 2017, consideration was given to whether static capacitor banks should be installed or dynamic capacitor banks. reactors, and then STATCOM. All these devices are capable of compensating for the need for reactive power of the network. Developers are not reluctant to install such devices, but cost is an issue. This cost has not previously been taken into account in tariff proposals, so it must be included in the framework of legislative changes, otherwise the project will become unviable.”
       A senior government executive agreed that the installation of dynamic reactive power support equipment would definitely impact the cost of the project and ultimately impact future electricity prices.
       He said, “STATCOM equipment used to be installed within the CTU. However, recently the CEA has introduced its interconnection rules requiring project developers to install this equipment in power plants. For projects where electricity tariffs have been finalized, developers can approach the Central Power Regulatory Commission submits a request to review the terms of the “change of law” for such cases and demand compensation. Ultimately, CERC will decide whether to provide it. As for the government executive, we view network security as a top priority and will ensure that this equipment is available to avoid disruptions in networks.”
        Since grid security is an important factor in managing growing renewable energy capacity, there seems to be no other choice but to install the necessary STATCOM equipment for operational projects, which ultimately leads to increased project costs, which may or may not depend on changes in legal conditions. .
        In the future, project developers will have to take these costs into account when bidding. Clean energy will inevitably become more expensive, but the silver lining is that India can look forward to tighter and more stable power system management, allowing for efficient integration of renewable energy into the system.


Post time: Nov-23-2023