Wind Power Low Voltage Ride Through

Wind power generation has taken its place in its share of electric power generation around the globe. Wind power generation normally utilizes induction generators for power production. In this case, these type of generators do not need synchronization when connecting or reconnecting to the electric grid or to any point of interconnection (POI).

When planning wind power integration, power system stability simulations are conducted to ensure system reliability with the wind power connection. In stability analysis, it is customary to analyze synchronization of generators’ rotor angles in the grid to evaluate system or generator stability. This practice is not applicable to wind power with induction generators based from the above discussion.

For power system stability, it is industry accepted to analyze low voltage ride through (LVRT) of a wind power generation rather than rotor angles. LVRT requires wind power plants to remain connected to the grid in the event of a worst short circuit which maybe nearest to the wind power plant. This is evaluated by observing the voltage at the POI of the wind power plant.

The figure below is a copy of Federal Energy Regulatory Commission (FERC) LVRT requirement. The plot shows the beginning of the voltage sag, the condition for the wind power plant to remain connected to the grid and the condition where the wind power plant is allowed not to remain connected to the grid. The voltage magnitude, plus the time duration, at the POI serves as the barometer if the wind power plant must stay connected or not.

Figure below is an illustration of LVRT requirements of different Transmission Operators and Transmission Owners relating to wind power plant interconnection. This plot is taken from this site. The figure tells us that different grids have different requirements for wind power LVRT. This maybe due to the system stiffness or inertia, system demand or wind power penetration. Moreover, some of the LVRT requirements were benchmarked from actual measured LVRT of wind power plants during system fault events.

Figure below is another interesting LVRT requirement in North America at the Western Electricity Coordinating Council (WECC). This plot is taken from this site. This illustration shows not only LVRT but also high voltage ride through (HVRT). Within the no-trip envelope, the wind power plant must stay connected to the grid but outside this condition the wind power plant can be disconnected from the grid.

The Energy Regulatory Commission in the Philippines has yet to develop voltage ride through requirement for wind power plants. There are existing and proposed or queued wind power generation located in the northern part of Luzon that maybe needed to comply with a developed LVRT. Moreover, LVRT policy can be applied not only to wind power generation but also to conventional power plants. Development of LVRT for wind power plants must be conducted for wind power generation to safeguard the stability and reliability of the power grid.

Conflict in Quality Regulation of Distribution Utilities

The Philippine Distribution Code (PDC) requires all User connection points that all Power Quality (PQ) requirements under PDC Section 3.2 be complied with. The PDC section 3.2.3.4 stresses this policy for voltage variations, see below. There are other similar statements for other PQ indices to be complied along section 3.2 of the PDC.

For new distribution system interconnection, the PDC points to the same section 3.2 that new connection points must have PQ within limitations specified in Section 3.2. In this case, the Distribution Utility (DU) must ensure that these PQ limits are complied with. See section 5.2 and further below.

The Energy Regulatory Commission (ERC) under its Work in Progress provides a seemingly conflicting objective with the PDC, as the Section 4 of the Guideline for Monitoring of PQ standards for DUs allows the DU to have 95% of connection points along a given distribution feeder to comply with section 3.2 of the PDC, see figure below. This means that 5% of the connection point can be accepted not to comply with the said PQ performance requirements. Practically, if the DU feeder has 100 connection points, 5 of those connection points can be operated not following the PQ limits specified in the PDC section 3.2.

The conflicting objective in these regulatory documents is clear. One document, the PDC, specifies that the DUs must comply with PQ limitations per section 3.2 in all connection points. On the other hand, the Guideline points that only 95% of those connection points must be ensured by the DU to have PQ level in accordance with the PDC section 3.2.

The ERC and DUs must adhere the PDC since this is the “code” of operating, financing and planning distribution systems. The Guideline must be reviewed as this is a Work in Progress. If the Guideline supersedes the PDC, then the PDC states that a PQ problem exists in the distribution system as section 3.2.1.2 below stresses this point.

Bring Down Power Rates by UP

As a Filipino living outside the Philippines, I have missed some research development like the study presentation by University of the Philippines (UP) professors on Reducing Power Rates in Generation. I have so much respect for the researchers since some of them have been my professors in my unfinished PhD degree in power systems.

Their study focuses on economic generation dispatch focus on MERALCO's power procurement. The study presents different cases or scenarios where MERALCO can procure from different power suppliers; NPC, IPPs, and WESM. In each case, the reduced power cost is reported and highlighted. This study is even utilized by one of our senators.

I agree on the principle of lowering power cost in anyway and anytime. Every effort on lowering power rates is my kind of thing.

But I am not sure if a DU which might have some purchase contracts with some IPPs will agree not to abide by those contracts. And note that these legal contracts go thru regulatory hearings.

I am not sure that the study focusing on rate economics provided a very firm ground on transmission and distribution capacity constraints of power procurement. DUs economic operation is coupled with technical constraints of the power system.

I am not sure the study related to uncertainty of demand and generation availability as they analyzed past data of the power rates. The variation of demand and generation reliability has much impact on power procurement.

I am not also sure that DUs participation in WESM is not beneficial for consumers. Most of the time, there are several hours of the day that the WESM spot price is zero! See example figure below. Thus, it can be beneficial to participate in the WESM.

Moreover, the senator said that the study is reliable since the researchers have developed a computer-simulation model. I am not sure if the senator is well versed on this. Power system engineers doing technical or economic studies have been using computer-simulation models for the past n years. The reliability or usability of a research study is not based on whether it was done using a computer-simulation model or by hand-manual computations but on the basis of its practicality.

There are a vast strategies to lower power procurement cost by DUs, in the end, legal contracts, power system constraints, uncertainty in demand and generation, and regulatory policies must be considered.

Technical Performance of an Electric Cooperative supplied with Wind Power

Wind power supply has further implications on system reliability because of its variability and can impact power quality in its nature of power production since it uses power electronics for power control that can produce harmonics and with its variability which can result to unacceptable voltage variations and voltage flickers. Ilocos Norte Electric Cooperative (INEC) source its power supply at specific times from the NorthWind Power Development Corporation.

INEC sources its power requirement to supply its franchise demand from National Power Corporation (NPC), NorthWind and Wholesale Electricity Spot Market (WESM). This is an economic operations strategy by INEC. INEC is fed by all these power suppliers from the grid via bulk power transformers to its distribution franchise.

National Electrification Administration (NEA) reports Electric Cooperatives (EC) scorecard for the year 2006. From this report, INEC performs very well technically as shown in the figure below. Aside from reliability and project implementation, INEC performed up to the expected par with all the other technical operations performance requirements. The uncoupling of power supply, voltage transformation thru transformers which go together with INEC’s own technical intervention within their distribution franchise, from the wind power to the INEC distribution system aids in delivering power with such a high quality of supply and technical performance. Overall, the analysis shows that an electric distribution system fed by a wind power plant can be operated up to the level of technical criteria required by the NEA or by Energy Regulatory Commission (ERC).

Simple Method for Selecting Overhead Distribution Line Conductor

Distribution Utilities (DUs) when planning for their distribution system, are faced with various options and constraints. One of the DUs’ process in system planning is choosing the right size of overhead distribution conductor for a given load, voltage level and expected load growth just to name a few. Most of the time, DUs have a set of standard sizes of conductors in the stock shop ready to be utilized for meeting additional demand or has a set of policies what size of conductor to be used for level of voltage or type of load. These practices do not follow that given the new conductor installation, DUs comply with various performance regulation.

In the performance regulation of DUs, it is important to meet the following:

• Supply the voltage within allowable limits - normally this is between 0.90 to 1.10 per-unit voltage.
• Minimize losses - to select a conductor is to ensure that as the power is being delivered, lesser line losses are produced.
• Minimize cost of conductor - economic regulation addressed in planning that DUs as much as possible to lower cost and at the same time operate within performance criteria.

In addition, the DUs must maximize power delivered, i.e. - the DU sees to it that the demand will be supplied with the power it needs given any time. Maximizing power transfer enables maximum utilization of the asset.

In this blog, consider a load of 200 amperes at 13.8kV level and selection between conductors ACSR sizes of 1/0 to 4/0 is to be determined for a line length of 1000 meters. The cost of conductors are derived from National Electrification Administration (NEA) website. The variations of voltage versus losses, cost of conductors versus losses and power delivered versus losses are plotted below. The conflicting patterns of voltage, cost of conductors and power delivered versus line losses are evident from the figures. The size of the conductor to be selected must be near the intersection point which minimizes the parameters involved. In this example the appropriate conductor size, the nearest conductor size to the intersection of the curves must be chosen, is ACSR 3/0.

Benefits of System Loss Reduction

Aside from impacting or not impacting electricity rates, system loss reduction has the following benefits:

• Reduction of fuel emissions due to lesser use of fossil-fuel generating plants - this has societal impact as it cover environmental concerns.
• Utility system capacity savings - decrease in losses provides released extra capacity for the distribution lines and transformers.
• Promotion of Energy Efficiency - it will be noted that the Distribution Utility (DU) is an energy-efficient electric company as it tries to decrease its system loss.
• Improvement of system voltage profile - the utility is regulated to supplying a range of voltage level and reduction of losses will produce a marginal system voltage quality that may be acceptable. This will also provide good power quality at the convenience outlets of consumers allowing their electric equipment/appliances to operate without mis-operation or loss of life.
• Increase Utility Commercial Appeal - a DU aiming at system loss reduction gets an added commercial appeal in the restructured power industry. This is important in the changing environment of the power industry, have you seen MERALCO TV commercials?

There is an optimum level of system loss reduction unique for all Distribution Utilities (DUs) where further reduction of losses will not result to further reduction of operation cost but more investment expenses. On the other hand, as demand rises in a distribution service franchise, technical losses and non-technical losses (utility own use) will at some point come with the demand increase. The equation of generation equals losses plus demand holds true. This is revealed by Philippine Power Statistics as shown in the figures below (the values include transmission and distribution losses, but this does not negate the point) :

Finding ways to reducing system loss must be a continuing program since it always provide benefits to the DUs and electric consumers.

Getting Lost with System Loss

The Energy Regulatory Commission (ERC) is calling for comments from various stakeholders on a new resolution they are proposing on reduction of distribution system losses incurred by Distribution utilities (DUs) which are Private Utilities (PUs) and Electric Cooperatives (ECs) in their operation of their service areas. Figure below is an extraction from the ERC document on the resolution.

From the illustration, the regulated system loss caps have been long withstanding for about eight years. The 9.5% and 14% loss caps for PUs and ECs respectively, are about to celebrate their ninth birthday until this new resolution on system loss caps reduction which is aimed to be implemented in January 2009 billing. The proposed 8% cap on the PUs might be tight since presently MERALCO operates its vast distribution system following a 9.5% loss policy. There are other PUs but benchmarking with MERALCO is a sure test if the other PUs can comply with the proposed 8% cap. The proposed 11% system loss cap on ECs is a product of National Electrification Administration (NEA) media declaration on system loss saying that by 2009 the national average for system loss for ECs will be 11%. The 2006 NEA scorecard does not report this 11% but points that about 53 out of a total of 84 ( I thought there are total of 98 ECs) ECs comply perfectly with system loss reduction.

Reduction of system loss caps always provide good benefits for both consumers and the electric distributor, there is no doubt on this and the currently applied caps should have been in Grade 3 in the present school year. But giving pressure to the DUs to comply within five months can be challenging. Given the facts for both PUs and ECs, the proposed resolution will be an expected regulatory debate in the ERC hearings. Aside from decreasing system loss, DUs look into improving system reliability and quality of supply in their planning and operations which I believe are of equal weight with system loss. If this resolution is implemented, DUs might get lost with reducing their system loss.

Framework for Operation Research Instruction for Future Electric Power Engineers

ABSTRACT

Philippine electric power industry has put a new face in itself: deregulation. With its new structure, optimization of planning and operations of electric power systems will be vital. Optimal performance of the power network will be highly considered may it be economics and/or technical. This paper presents a framework for Operations Research (OR) instruction for future engineers of electric power systems. The key to optimized electric network in the coming years is to educate and train electrical engineering students solve power system problems utilizing OR. The manuscript is comprised of appropriate OR solutions to power system problems. The presentation will be useful for teachers giving OR courses to students of electrical engineering.

See Full Paper - Framework for Operation Research Instruction for Future Electric Power Engineers

Philippine Electric Cooperative Analysis : Distribution, Supply and Metering (DSM) and Annual MWh Sales

Economics tells us that having more sales tend to bring down the prices. The components of electric distribution tariff consists of different items. Distribution, Supply and Metering (DSM) Charges are among basic fees that are collected from residential consumers. Figure below from the Energy Regulatory Commission (ERC), illustrates the components of the total residential distribution tariff.

In this blog, we show that increasing the electric energy sales tend to reduce the DSM charges of the Electric Cooperatives (EC). The next figure is derived from the EC data and is analyzed thereof. It is shown that the more energy sales produced by an EC, the lesser DSM fees the consumers pay. This is due to the fact that the path of electric power flow to more consumers is being utilized efficiently. More consumers means more power to be distributed, supplied and metered using the same electric distribution circuits. EC #95 having more sales charges the lowest DSM fee while EC #3 charges the highest DSM fee having the lowest energy sales. It is interesting that EC #94 charges low DSM fees while providing not so much high energy sales. This may be due to the distribution system configuration of the said EC where is utilized efficiently.

What Happened Here?

Historically, Metro Manila carries a whopping 50 to 60 percent of the total load of the Luzon Grid in the Philippines. Five bulk power substations deliver power to the metropolitan, if a disruption in the transmission lines connecting the load center to any of these substations, a power blackout is imminent in the area. And when your demand is cut into about half, the tendency is for system frequency and bus voltages to swing throughout the system.

When the crane cut off the transmission line, this produces an open circuit that may divert power flows in the power system and may produce a high impedance as seen by protection devices set to guard against system faults. Normally, the protection devices act faster for short circuit and slower to open circuits, since open circuit produces less fault (overload) currents.

Another TransCo tower in Lanao Sur bombed; 4th in 2 days

FROM MINDANEWS WEBSITE

Another power pylon of the National Transmission Corporation was bombed by unidentified attackers at dawn today, the fourth tower in Lanao to be attacked in less then 24 hours.

Avelino Dawis, Transco Lanao district manager said tower no. 29 in Bubong town was totally destroyed but caused no power interruption in Lanao del Sur and the rest of Southern Mindanao.

Col. Rey Ardo, chief of the Army 103^rd Brigade said the suspects are members of a criminal gang trying to extort money from the state-run power utility.

“The bombings are not related to what is happening in other areas of Mindanao. These are the handiwork of criminal gangs,” Ardo said.

Last Monday, explosives fashioned from 81-mm mortars shells damaged three towers in the towns of Bacolod and Kasuwagan in Lanao del Norte.

Dawis said damage on the towers were minimal except for tower no. 50 in Kauswagan which needed weeks to repair.

Since January this year, at least 20 towers of TransCo have been bombed. (MindaNews)

Philippine Electric Cooperative Analysis : Circuit Kilometer and Annual MWh Sales

In operating and planning electric distribution business, the expansion and demand growth must be intertwined. Expansion won’t happen if not demand driven. Increasing demand must be met by system expansion. The figure below is a graphical illustration of Philippine Electric Cooperatives (PECs) in year 2006, depicting their distribution line in circuit kilometers versus the annual sales in MWh.

From the figure, EC #91 has the longest ckm but does not have the highest sales. EC #96 has the highest energy sales with operating significant lesser ckm of distribution line compared to EC #96. It can by thought that EC #96 might have a service area that is very rural thus it has to erect longer lines to reach consumers. On the other hand, if this is not the case, then EC #96’s investment in distribution lines is not optimized since it has put a longer ckm with a smaller demand.

The regulation of system expansion must meet the rise of demand up to the point that it satisfies reliability and quality performance. However, investment in distribution business must not be overdone because some of these costs are passed on to the consumers.

Comments on the Enforcement of Reliability and Power Quality Standards, and Quality Reliability Index (QRI) for Distribution Utilities

In 2006, I made significant technical comments on the issues of reliability and quality of electric power supply being delivered by Distribution Utilities in the Philippines. Energy Regulatory Commission (ERC) provides the link Work in Progress for the said issues.

The complete documents of comments from various entities can be accessed here - ERC Reliability and Power Quality Comments.

Philippine Energy and Power Independence thru Wind Power

The Philippines in 2007 had installed power generation capacity of about 16,000 MW scattered around the archipelago. Of the various energy sources, renewable energy which were wind and solar accounted for 0.16% of the total capacity. Natural Gas provided a decent 17.78% contribution to the electric power demand. Most of these Natural Gas generation are located for Luzon power supply. Figure below illustrates the installed capacity from the Department of Energy website.

The electric power demand in 2007 was about 9,000 MW and is mostly is Luzon. The problem of Visayas and Mindanao is that even with small amount of demand, generation and transmission is scarce in such areas. The figure below presents the demand scenario for the entire country considering the three regions.

Wind power mapping in the Philippines presented in two studies done by National Renewable Energy Laboratory (NREL) in the United States which are:

• Philippines Wind Energy Resource Atlas Development
• Philippine Wind Farm Analysis and Site Selection Analysis

indicated that wind power in the Philippines can provide 76,600 MW considering good to excellent wind resource while at moderate to excellent wind resource, wind power can supply 173,600 MW. Several assumptions were applied in accounting for these values.

Considering the 2007 electric demand, say wind power potential is harnessed even up to half of its potential (38,300 MW), the country has more generation capacity in this scenario. Pickens Plan suggests that Natural Gas can be utilized for transportation which the Philippines must consider in view of the mapped wind power potential.

If this will happen, the Malampaya gas can be solely used for transportation which will bring down our oil imports and may bring down gas prices thereof. Electricity prices will become lower but transmission system operation will be revised with more wind power generation interconnected to the grid. Investments in wind power will surely come in if the Renewable Energy (RE) bill is enacted into law.

With wind power potential in the country, Philippines can attain energy and power independence.

Analysis of Voltage Unbalance Regulation

Abstract

This paper presents an analysis of the present voltage unbalance regulation in the deregulated power industry in the Philippines. The regulation of voltage unbalance was examined in the light of various standards pertaining to voltage unbalance. The response of three-phase electrical equipment to voltage unbalance is evaluated as per limits of Philippine Distribution Code (PDC). The voltage unbalance limits for transmission and distribution were investigated if it were practical using a numerical simulation of an electric power system. Recommendations and conclusions were drawn as per the analytical outline for voltage unbalance regulation.

See Full Paper - Voltage Unbalance Regulation

$850-M projects waiting for RE bill

$850-M projects waiting for RE bill
By Katherine Adraneda , Philippine Star
Tuesday, July 29, 2008

Some $850-million investments in renewable energy (RE) projects in the country are waiting in the wings, as investors appear to be in a wait-and-see attitude towards the passage of the RE Bill, which is said to be languishing in Congress in the past 19 years.

Former Department of Energy (DOE) chief and current chairman of World Wide Fund for Nature-Philippines (WWF) Vincent Perez Jr. said that such amount of investments on RE projects in the country is foreseen to possibly even double if only lawmakers would approve the proposed measure and President Arroyo would sign it into law immediately.

In an interview at the sidelines of the seminar on RE held over the weekend at Tagaytay City, Perez said these pending investments on RE projects in the Philippines might push between now and 2011.

“These investments are in anticipation of the (passage) of the RE Bill. These projects could perhaps be made in the next five years,” Perez said.

The US Embassy in Manila sponsored the 2008 Tagaytay seminar dubbed “Renewables: Energy for the 21st Century” wherein Perez was the keynote speaker.

Perez told reporters that the $850-million pending investments on RE projects involved the tapping of the country’s geothermal and wind resources.

Perez said the proposed geothermal energy proj-ects consist of a 20 megawatt (MW)-project in Nasulo, Dumaguete; 50MW in South Cotabato; 50MW in the Bicol area; 20MW in Mabini, Batangas; 40MW in Compostela Valley; and 40MW-project in Biliran.

On wind energy projects, Perez said proposed plans include the 80MW and 40MW projects in Ilocos Norte.

Perez explained that estimates on the cost of these proposed RE projects were derived by multiplying the expected power output of the facility by $2.5 million, said to be the prevailing approximation of the price per MW.

Meanwhile, Perez said that a 10MW solar energy project in Mindanao, worth $50 million is also pending, in anticipation of the passage of the RE Bill.

During his speech at the seminar, Perez cited his study titled “A Business Case for Investing in Renewable Power in Emerging Countries,” which has noted that the Philippines is “well-suited to renewable energy.”

Perez said that his study was a result of his “one-year of doodling” at Yale University after leaving the Arroyo Cabinet years ago. His case study was made in May 2006.

“The key factors for RE growth in the country are, of course, first, is RE resources, then RE policy support, attractive tariffs, tight local supply, and isolated grids, which should push us to really become self-sufficient,” pointed out Perez, even stressing that government policy-support on RE is pivotal to the shift and promotion on the use of RE sources.

According to Perez, the “time is ripe” for RE in the Philippines.

This is because RE could insulate the country’s economy from fuel price fluctuation, as RE could also accelerate electrification in off-grid areas, promote sustainable growth, and improve the country’s energy security.

Quoting DOE data on the Philippines’ energy mix in 2007, Perez said that the country has already become 57.2 percent energy self-sufficient as of end 2007, with geothermal as the biggest indigenous energy source, accounting for 21.5 percent.

Perez credited the introduction of the Malampaya Natural Gas Project, located off Palawan, for the increased energy self-sufficiency of the country last year.

Natural Gas accounted for 4.5 percent in the 2007 Philippine Energy Mix.

However, Perez said that the country remains “largely dependent” on imported oil as well as imported coal, which accounted for the 31.8 percent and 11 percent, respectively, of the country’s energy mix last year.

Natural gas and coal are dominant fuel sources for power generation in the country, with 60 percent.

Perez added that renewables contribute 31 percent and oil nine percent to the power generation of the Philippines.

But Perez emphasized that the Philippines is the second largest producer of geothermal energy in the world, “very closely” next to the United States.

Perez also asserted that the Philippines has a great chance of even becoming the top geothermal energy producer in the world in a decade, if only appropriate technology and government support are achieved.

Perez said that the pending RE Bill in Congress is expected to accelerate growth in the RE field in the country, especially since an additional capacity requirement of 3, 620MW is being anticipated for the entire Philippines by 2014.

Specifically, the additional capacity required by 2014 consist of 1, 950MW for Luzon; 820MW for Visayas; and 850MW for Mindanao.

Power Engineering Education for the Restructured Philippine Electricity Industry

Excerpt -

The Philippine electricity industry has been restructured by virtue of the Republic Act No.9136 (R. A. 9136), which is the Electric Power Industry Reform Act of 2001. The centralized operational approach has changed to a competitive framework. This kind of set-up is new to the country. Generation, transmission and distribution of electric energy are now more of a market environment. Generation companies, Gencos, are used to be owned by the state together with the power transmission company, Transco. In the separation of these two components, Gencos will be sold to private corporations and investors. Transco is to be privatized and work as a single entity. Distribution utilities, Discos, will retain their regulated environment and will have private companies and public cooperatives to run Discos. Another important part of electricity deregulation in the Philippines is the establishment and operation of the Philippine Electricity Market Corporation (PEMC). Energy will be traded by power producers and consumers more like a stock market at the Wholesale Electricity Spot Market (WESM).

With the changes happening in the electricity industry, the power engineering education should rightly come with self-transformation. To enable the future power engineers who will handle jobs and positions in the deregulated industry the academe should respond and assess the modifications and improvements that need to be done. Power engineering education feeds the power engineering profession.

See Full Paper -Electric Power Education