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Table 3 Result of VRE Implementation Challenges

From: A critical review of the integration of renewable energy sources with various technologies

Defiance Descriptions Ref.
Balance
 Insufficient appropriateness of short-term generation Increasing generation of VRE results in changed performance requirements for conventional generation, such as speedier ramping requirements. Insufficient adequacy for these performance requirements can result in predictable short-term mismatches between generation and load, redeployment or curtailment. [25]
 Insufficient adequacy for long term generation A growing generation of VRE leads to changed performance requirements for traditional generation, such as night-time or seasonal power generation balancing. Insufficient adequacy can lead to predictable long-term mismatches between generation and load for these performance requirements. [10, 31, 118]
 Inadequate firmness of VRE generators Variability of the generation of VRE increases the uncertainty of estimates of firm capacity to generate. This results in higher reserve requirements and an increase in unplanned mismatches between generation and load, power activation balancing, re-dispatch or curtailment. [18, 23, 73]
 Insufficient VRE generator forecast Variability of the generation of VRE leads to increasing inaccuracies in the forecast. The results are unplanned mismatches between generation and load, activation of the power balance, dispatch or curtailment. [54, 65, 104]
 Limited VRE generator dispatch-ability The output range of VRE generators is limited by their fluctuating primary resource provision. Use VRE generators to offset unexpected outages of other generators is therefore minimal. This leads to unplanned inconsistencies between activation of generation and load and balance of electricity. [1, 4]
Quality
 Increased flicker The feed-in of VRE generators via electronic power inverters increases the flicker content locally. This leads to the shorter lifespan of equipment, trips or damage to equipment at end users. [72, 92, 121]
 Stepping up harmonic distortions Feed-in of VRE generators via electronic power inverters increases harmonic distortions. This leads to the shorter lifespan of equipment, trips or damage to equipment at end users. [8, 58]
 Unstable shutdown at blackout VRE generators which continue to generate electricity in areas disconnected from the larger network constitute security hazards for maintenance or repair operations. [48, 62, 106]
 Increasing excursions at the a local voltage VRE generator feed-in to lower grid rates at low-consumption times raises device voltage for end users. This results in overloading and reduced damage to the equipment, trips or equipment. [12, 111, 131]
Stability
 Insufficient supply of reactive capacity VRE generators have lower reactive power output, compared to conventional generators. To maintain system voltage, the VRE deployment and simultaneous power transmission expansion require higher levels of reactive power. The under-supply of reactive power contributes to breaches of dynamic stability legislation, redeployment or VRE generation curtailment. [99, 100]
 Reducing short-circuit power Compared to synchronous generators, VRE generators produce significantly less short-circuit power. A low short-circuit power level increases voltage instability and makes identification of faults more difficult. This leads to breaches of dynamic stability legislation, dispatch or curtailment of VRE production. [55, 99, 100]
 Reducing inertia VRE generators offer considerably less rotational inertia compared to synchronous generators. In cases of imbalance between supply and demand, this leads to faster frequency excursions. Faster frequency changes infringe dynamic stability regulations and lead to VRE generation being dispatched or curtailed. [5, 99, 100]
 Failure to manage frequency travel limits The VRE generators must fly beyond a specified frequency range. With rising rates of VRE penetration, this requirement leads to violations of the stability regulations by tripping a growing amount of generation at a particular stage. [20, 42, 91]
 Insufficient synchronization of the voltage trip limits The VRE generators must travel outside a specified voltage band. Consequently, increased voltage variations due to the VRE generation lead to increased tripping of VRE generators. This in turn, leads to cascading journeys, breaches of regulations on dynamic stability or an accumulation of incidents of stability. [27, 103, 127]
 Diminishing reserves of frequency control To stabilize system frequency, short-term instability of the VRE generation increases the need for frequency control reserves. At the same time, VRE generators do not deliver reserves of power. The lack of these reserves leads to dynamic stability regulations being violated, VRE generation being dispatched or curtailed. [15, 47, 79]
 Increasing interactions between controls Connected VRE generators that controlled inverters can interact with the electricity grid, leading to unattended power oscillations. They can lead to reduced equipment life, trips or damage to equipment if uncontrolled. [6, 64, 89]
Flow
 Missing capability on the power grid The current grid distribution system is not large enough to handle power feed-ins from VRE generators. This will result in curtailment of the VRE generators if inadequate sizing is understood. If insufficient sizing is not recognized, this will lead to a reduced lifespan, feeder trips or damage to the equipment. [35, 97]
 Increasing excursions to the regional voltage In radial distribution grid feeders, the VRE generator feed-in increases the system voltage in those areas. This leads to overloading of feeder equipment and leads to reduced service life, feeder trips or damage to equipment. [58, 123]
 Flow patterns from lower grid levels are increasingly volatile At lower voltage levels VRE generation makes power flows more volatile and less predictable. This results in increased constant or temporary curtailment of VRE generators. [44, 126, 130]
 Narrow limits of the trip voltage The VRE generators must move beyond a specified voltage band. Consequently, increased voltage variations due to the VRE generation lead to increased tripping of VRE generators. This, in turn, triggers journeys to wider grid areas, shorter lifespan of equipment or possible damage to equipment. [122]
 Increasing currents on short-circuits VRE power plants connected at low temperatures increases narrow-circuit currents in the event of network failures. The heightened currents can cause further damage to trips or equipment. [86, 105, 119]
 Greater transmission distances The area dependence of generating VRE includes increasingly long information and service among locations of generation and consumption resulting in higher energy losses. [34, 63]
 VRE generation lacking visibility Power system equipment at small power does not evaluate the load flow or the loading of the equipment. VRE feed-in in these areas results in unplanned flows resulting in reduced service life, feeder trips or damage to the equipment. [67, 68, 83]
 Inadequate protection design Protection schemes are not planned for increasingly dynamic load flows due to the VRE generation in lower voltage grid areas. Inadequate design of the protection scheme causes unintended trips or overloading, resulting in shorter lifetime or damage to the equipment. [9, 61, 122]
 Lack of grid transmission power Insufficient transmit power between locations of VRE generation and consumption leads to curtailment of VRE generation, dispatch operations or unintended transmitting flow, including loop flows. [97]
 VRE generation lacks controllability Simple VRE power stations are usually not fitted with a remote-controlled interface. Uncontrolled feed-in of VRE up the approval to unplanned energy flows resulting in decreased equipment lifetime, trips or equipment damage. [63, 96, 126]