Control and Design of Microgrid Components - Power Systems ...

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V rms l− n = 2 V π DC Equaling the active power in the AC and DC side, it is possible to observe that the currents in the AC and DC side are related by: P I DC DC rms = V I = P = 3V − I DC DC 3 2 = I π rms line cos AC ( ϕ) rms l n line This expression shows that only the component of the AC current that is in phase with the voltage waveform is reflected to the input of the inverter, at the DC side. Figure 4.11 shows the voltage between the points A and N illustrated in Figure 4.10. It shows what switching sequence has to be applied to achieve each of the six pieces of the voltages: each devices conducts for 180 degrees. Figure 4.11 also shows what current flows in the DC bus given the switching sequence. Depending on the phase of the current on the AC side with the voltage Van, then it is possible to see that the current seen on the DC side changes. The first case shows the current Ia in phase with the voltage Van: the power factor is one and all the AC current is used to exchange power with the DC side. The second case shows a current 90 degrees apart with the voltage: the power factor is zero and none of the AC current is used to exchange power with the DC side. In fact, it is possible to see that the current is entering the DC bus for 30 degrees and leaving for the remaining 30 degrees with a zero net effect. In this case only reactive power is exchanged with the AC side. The last case shows the current with a phase displacement equal to the chosen PF of 0.8 where AC voltage and current waveforms are displaced by: o ϕ = a cos(PF) = 38.86 This case represents a contemporary exchange of active and reactive power with the AC system. cos ( ϕ) 60
Switching Sequence 145 146 136 236 235 245 AC Current Flowing in DC Bus -Ib Ia -Ic Ib -Ia Ic Van Ia Only Active Power Ia Only Reactive Power Ia PF=0.8 Figure 4.11 AC and DC Currents on the Voltage Sourced Inverter. The apparent phase of the inverter is given by: S = 3V l I rms rms −n line This last expression when combined with the expression for the active power allows to give a value for the inverter ratings starting from the value of the power of the prime mover and the power factor chosen: S = P cos DC = P Pr ime Mover ( ϕ) PF The maximum output power of the prime mover is the maximum active power that the inverter may ever be requested to deliver, while the maximum amount of reactive power that is injected is determined by the choice of the power factor. The transformer has the task to interface the three-phase world of the inverter terminals with the 4 wire environment on the feeder side to allow for single phase loads to be connected. The delta configuration on the inverter side of the transformer is a direct consequence of the fact that the inverter generates voltage on a line to line basis between phases. The feeder side of the transformer is wired at wye, with the center of the star available to be connected to the neutral 61
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PSERC Control and Design of Microgr
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Information about this project For
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Executive Summary Economic, technol
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Table of Contents Chapter 1. Introd
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List of Figures Figure 1.1 Microgri
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List of Figures (continued) Figure
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Chapter 1. Introduction Distributed
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1.2.2 Operation and Investment The
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Figure 1.1 Microgrid Architecture D
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Chapter 2. Static Switch The static
Page 21 and 22: ω ωo ω1 Preq Pgrid P Pload Figur
Page 23 and 24: 2.3 Synchronization Conditions The
Page 25 and 26: droop. The issue is that it is poss
Page 27 and 28: This synchronizing behavior is unac
Page 29 and 30: Figure 2.12 shows on the upper plot
Page 31 and 32: Chapter 3. Microsource Details This
Page 33 and 34: with different size. This control i
Page 35 and 36: u + _ K F ω o + _ ω o s P u ω o
Page 37 and 38: Q versus E Droop E req Q m Q _ + E
Page 39 and 40: currents from the microsources incr
Page 41 and 42: inverter ratings limits (in kVA) ca
Page 43 and 44: A 16 DG B 22 DG Static Switch C 8 D
Page 45 and 46: ω Unit 2 Max Unit 2 ω o Unit 1 ω
Page 47 and 48: Unit 1 Min Unit 2 ω Unit 1 ΔPmin
Page 49 and 50: positive value. When this value has
Page 51 and 52: needs of power. This solution would
Page 53 and 54: This expression is very similar to
Page 55 and 56: Li-Pmax < Fi < Li for unit ‘i’
Page 57 and 58: ω ω ω o Fo ω o Fo F F Unit Powe
Page 59 and 60: This control has been implemented i
Page 61 and 62: characteristic will coincide with t
Page 63 and 64: ating on the voltage output, establ
Page 65 and 66: Prime Mover DC Storage Voltage Sour
Page 67 and 68: linearity. A value of 30 degrees pr
Page 69 and 70: Figure 4.8 P and Q Plane Capability
Page 71: 4.4 System Ratings The inverter per
Page 75 and 76: generated by the inverter: the VA r
Page 77 and 78: % of voltage unbalance = 100 maximu
Page 79 and 80: Figure 5.2 shows the plots for P,Q
Page 81 and 82: Figure 5.5 shows the measures of P
Page 83 and 84: Figure 5.7 One Unit Connected to th
Page 85 and 86: Microsources are connected to the l
Page 87 and 88: The transformer impedance can be se
Page 89 and 90: o r 1 = 0.3277 Ω = 0.0547 Ω x x 1
Page 91 and 92: Table 6.3 Load Data Summary. Rated
Page 93 and 94: The worse case scenario is represen
Page 95 and 96: The filtering is achieved by a low
Page 97 and 98: works with an internal voltage leve
Page 99 and 100: terminals to achieve each of the th
Page 101 and 102: Table 6.5 Lookup Table for Switchin
Page 103 and 104: Chapter 7. Microgrid Tests There ar
Page 105 and 106: Table 7.1 Summary of Experiments fo
Page 107 and 108: Table 7.2 Series Configuration Cont
Page 109 and 110: Figure 7.6 Control of F1 and F2, Fe
Page 111 and 112: Figure 7.10 Control of P1 and F2, F
Page 113 and 114: pu, but when it is fed from a remot
Page 115 and 116: Unit 1: P, Q, F, Frequency, Voltage
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Unit 1: P, Q, F, Frequency, Voltage
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7.4.1 Unit 1 (F), Unit 2 (F), Impor
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Import From Grid, Setpoints are 10%
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Island, Setpoints are 10% and 90% o
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7.4.2 Unit 1 (F), Unit 2 (F), Expor
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Export to Grid, Setpoints are 10% a
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7.4.3 Unit 1 (F), Unit 2 (P), Impor
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7.4.4 Unit 1 (F), Unit 2 (P), Expor
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Chapter 8. Conclusions This work sh
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[14] Lasseter, R.,” Microgrids,
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