Using Phasor Measurement Unit in Control Room for Monitoring Frequency Primary Regulation of Generator Unit Igor Ivanković Dalibor Brnobic Croatian Transmission Operator, HOPS Studio elektronike Rijeka Zagreb, Croatia Rijeka, Croatia [email protected] [email protected] Renata Rubeša Marko Rekić Croatian Transmission Operator, HOPS Croatian Transmission Operator, HOPS Zagreb, Croatia Zagreb, Croatia [email protected] [email protected] Abstract—Croatian TSO has finalized a Proof of Concept generator unit, contrary like SCADA or others measurements (PoC) for monitoring generators with purpose of primary with sampling rate period higher than 1 second. frequency regulation mode within Wide Area Monitoring System (WAMS) using synchrophasors in control room. The PoC has been conducted to check a possibility for main goal of PoC was testing well proven synchrophasor monitoring generators in real time in control room with technology for purposes of advanced monitoring of generator synchrophasor technology. Few typical generators were units connected to transmission network. This technology was analyzed in PoC, one thermal unit and five hydro units. Units tested on six generators connected to 220 kV and 110 kV were monitored in all operating ranges and also some archived transmission network in five power plants. For this project three data was included in this document. This synchrophasor different ways of acquiring synchrophasor data for analyses technology also successfully logs everything that happens were used. Data were collected with phasor measurement units during generator operations. (PMU) and from archives. Some PMUs were already installed on high voltage side of step up transformer earlier for other Croatian TSO placed PMUs on high voltage of step up purposes, rest of measurement campaign was done using transformer, Fig. 1. In those cases, it was 220 kV and 110 kV. portable PMUs in two power plants. Results show full potential of using this data for monitoring generator for primary HV transmission bus PMU type: regulation. Output from project gives Croatian Transmission - fixed with 12 data phasor (UL123, IL123, U120, I120) - portable with 2 data phasor (U1, I1) system operator (TSO) possible technical solution which can be implemented in control room. Keywords—frequency primary regulation, monitoring Generator bus generator modes, PMU, synchronized phasor measurement WAMS I. INTRODUCTION Fig. 1. PMU connection point on generator unit. Imbalance between production and consumption causes Two kind of PMUs were used in PoC, fix mounted deviation of frequency from its nominal value in the standard TSO multifunctional PMUs, which create 12 synchronously connected power system such as continental synchrophasor data streams to control room (3phase values for transmission network. First stage compensation of such voltages and current, and 3 sequence values for voltages and frequency deviation is done by primary frequency regulation. current). Second PMU type was portable type, which was used According to network code for transmission network [1], each for measuring campaign for 6 months on two generator units generation unit has to be able to participate in primary in two hydropower plant. It creates only two synchrophasor frequency control and each control area is obliged to have this data streams with positive sequence voltage and current. primary regulation reserve to contribute. Synchrophasor technologies have very high sampling rate The status of primary regulation is very hard to detect with resolution (20 ms) for measurement of frequency and active conventional measuring technology. To solve that problem power, with same time stamps which makes those values high sampling frequency with time synchronized comparable and applicable as a new functionality in WAMS. measurements is applied as a solution. This paper will elaborate monitoring of the primary regulation based on the TSO has obligation to determine primary regulation mode synchrophasor measurements from WAMs and analysis of for each generator and this technology gives possibility to some generator primary regulator statuses in the Croatian have full insight of generator unit operation. Slope power system. It is expected that this high sampling characteristic of f/P diagram, can be monitored in real time measurement will record any kind of transient phenomena on from minutes to daily basis, or any other wanted period. Generators on high voltage step up transformers side will be equipped with PMUs. In some cases, virtual PMUs for This work has been supported by Croatian Science Foundation, Croatian Transmission System Operator (HOPS) and HEP Generation under the generators connected on busbar can be designed, if all other project WINDLIPS – WIND Energy Integration in Low Inertia Power System, grant no. PAR-02-2017-03. 978-1-7281-7455-6/20/$31.00 ©2020 IEEE Authorized licensed use limited to: University of Zagreb: Faculty of Electrical Engineering and Computing. Downloaded on October 28,2020 at 14:30:01 UTC from IEEE Xplore. Restrictions apply. bays in switchyard has PMU. This case is not elaborated in - L , – electrical energy consumption for whole PoC, as analyses are still being performed. interconnection in two years before. u y−2 II. FREQUENCY PRIMARY REGULATION IN ENTSO-E Calculated primary regulation obligation for European TSO [4], in ENTSO-E interconnection for 2019, is given in European Transmission System Operator for Electricity Table I. (ENTSO-E) is responsible for operational rules and security of high voltage transmission network among whole of Europe. TABLE I. CALCULATED PRIMARY REGULATION Any imbalance in power system for continental European transmission network in normal condition and during minor or State [MW] medium disturbance will be compensated first with primary ALB 4 regulation and consequently with secondary or tertiary type of AUT 66 frequency regulation, depending on severity of disturbance BIH 15 Fig. 2. Each TSO is responsible in case of frequency deviation BEL 80 to compensate that frequency deviation, with generator units BUL 41 SUI 61 in operation [2]. Those units has to be declared and certified CZE 81 for that functionality, from TSO. GER 605 DEN (west) 20 Reserve / ESP 368 frequency FRA 527 GRE 46 Primary Secondary regulation Tertiary CRO 11 regulation regulation HUN 29 30 s 5-15 min 15-60 min t ITA 274 MNE 2 MKD 5 NED 111 Frequency restoration time POL 157 POR 54 Fig. 2. Time frame for respond of primary, secondary and tertiary ROU 60 frequency regulation. SER 39 SLO 15 Primary regulation mode in continental European SVK 26 transmission network interconnection should be activated in TUR 294 first 15 seconds with range from 0 – 50% reserve, and from UKR (west) 9 Total: 3000 50-100% in the next 15 seconds (total time is 30 seconds). Primary regulations has two main set points, first at frequency This value of reserve has to be maintained during the deviation of ±20 mHz and second is ± 200 mHz. whole year. In order to do that TSO has to have careful Generation Company should have units, which are planning procedures with Generation Companies. available to operate in primary regulation within some range. Those data such as available power for primary regulation, III. MONITORING WITH PHASOR MEASUREMENT UNIT respond time and droop speed control (statism) have to be For proper detection of any changes in generation unit recorded and monitored, from TSO’s side. output it is necessary to have high sampling rate measurement and also that two measurements, of frequency and active TSO contribution for primary regulation reserve is power are synchronized, in order to be able to compare those mandatory and it is calculated for each year (1) in ENTSO-E two measurements. This measurement must be very sensitive coordination [3]. and without dead zone, otherwise wrong picture of primary regulation operation can be deduced if there is a small change , , , = (1) of operating point in a band of ± 20 mHz. ,−2+ −2, WAM system was used in this PoC like platform in control ∙ � −2+ −2� Where are: room. WAM receives and archives data from six generators unit in PoC with sampling rate of 20 ms [5], [6], [7], [8]. Those P - , – TSO initial obligation for primary regulation in two measurements are compared for every frequency change. current year, i c Active power output of generator unit must follow frequency - FCR – calculated value for primary change and give support to frequency recover [9], [10], [11]. regulation in whole interconnection, In that case, that particular unit is active in primary regulation. interconnection - G , – electrical energy generation on TSO control Droop speed control characteristic for generator unit area in two years before, active in primary regulation (2) is define: i y −2 - L , – electrical energy consumption on TSO control area in two years before, Δf (2) i y−2 droop speed control = 100% f - G , – electrical energy generation for whole ΔP interconnection in two years before, P ∙ y −2 Authorized licensed use limited to: University of Zagreb: Faculty of Electrical Engineering and Computing. Downloaded on October 28,2020 at 14:30:01 UTC from IEEE Xplore. Restrictions apply. Where are: IV. GENERATORS OPERATED IN FREQUENCY PRIMARY REGULATION MODE - f – frequency deviation from nominal frequency, Hydro power plant Peruca (southern part of power system) f - Δ – nominal frequency, has two generators equipped with fixed PMUs on 110 kV - P – active power deviation from nominal value for voltage level. HPP Peruca contributes for primary regulation generator unit, with both generators unit. One detail is chosen for presentation Δ how it is created on dot for f/P diagram. Fig. 5 presents short - P – nominal power for generator unit. period (one hour) of operation for generator 2. Droop speed control on generator unit is given in relative values (%) for nominal frequency and active power value, and general characteristic is defining with f/P graph, Fig. 3, (frequency/Power). P [MW] P [MW] Linear characteristic for speed control Nonlinear characteristic for speed control ∆P ∆P f [Hz] ∆f f [Hz] Fig.