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

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E o − Q max E req ΔE ΔE Q max Q Inductive Region Capacitive Region Figure 6.6 Q versus E Droop. For Microsource 1: The total drop is (208-201.3) = 5.8V = 2 ΔE. It means that ΔE = 2.9V, so the setpoint for the voltage is: Ereq = 208-ΔE = 208-2.9 = 205.1 V Qmax was already calculated as 11.25kVar, so the slope for this droop is: m Q Δ = Q E max = 2.9 11.25 = 0.2578 V/kVar That is, the voltage is allowed to change of 0.2578 Volts for every kVar that is injected. For Microsource 2: The total drop is (208-202.2) = 6.7 V = 2 ΔE. It means that ΔE = 3.35V , so the setpoint for the voltage is: Ereq = 208-ΔE = 208-3.35 = 204.65 V And the slope for the droop is: m Q Δ = Q E max = 3.35 11.25 = 0.2978 V/kVar That is, the voltage is allowed to change of 0.2978 Volts for every kVar that is injected. 82
The filtering is achieved by a low pass LC circuit. The capacitors are connected at delta. The values for the components are: L = 1.2 mH C = 30 μF Table 6.4 summarizes all the data relevant to the microsources. Table 6.4 Summary of Microsource Data. V rated [V] S rated [kVA] P rated [kW] Q rated [kVar] MS 1 480 18.75 15.0 11.25 MS 2 480 18.75 15.0 11.25 m [rad/kW] π 15.0 π 15.0 m Q [V/kVar] X [Ω] L [mH] C [μF] 0.2578 1.88 1.2 30 0.2978 1.88 1.2 30 6.3 Control Implementation Microsource control can be implemented with a limited number of measurements passed to a hardware block that creates the pulses for the gates of the power electronic devices inside the inverter. The hardware block consists of three distinct boards. The first board is responsible for conditioning the values of the measured quantities to voltage levels that allow the interface with the second board, the DSP. The DSP implements the control block, constantly comparing desired and measured quantities to generate the gate pulses. These pulses are then passed to the third board, that amplifies the low voltage pulse signals coming out from the DSP to the voltage level needed to operate the actual power electronic devices. The control blocks are encoded in Assembly language and compiled with Metrowerks CodeWarrior software. The executable code is then passed to the program memory of the DSP board. The Digital Signal Processor (DSP) is a versatile hardware device that uploads an executable code with the information on how to manipulate inputs to generate outputs. The DSP is the ideal environment to code the control of the microsource. The input of this board are the signals coming from the sensing devices and the outputs are the firing pulses that are sent to the gates of the power electronics inside the inverter. The code is uploaded in the DSP memory through a connection with a computer, where the program is compiled to an executable format. It is possible to debug the code by executing it on the DSP and sending some of the internal variables to dedicated pins where it is possible to connect with oscilloscope probes. The sensing signals reach the board as analog signals and are converted into digital form to be processed inside the integrated circuit. It is also possible to debug the code by means of a special application called PCMaster, a program written by Motorola to support the code builders for their DSP products. 83
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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
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ω ωo ω1 Preq Pgrid P Pload Figur
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2.3 Synchronization Conditions The
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droop. The issue is that it is poss
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This synchronizing behavior is unac
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Figure 2.12 shows on the upper plot
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Chapter 3. Microsource Details This
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with different size. This control i
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u + _ K F ω o + _ ω o s P u ω o
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Q versus E Droop E req Q m Q _ + E
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currents from the microsources incr
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inverter ratings limits (in kVA) ca
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Page 45 and 46: ω Unit 2 Max Unit 2 ω o Unit 1 ω
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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
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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 and 72: 4.4 System Ratings The inverter per
Page 73 and 74: Switching Sequence 145 146 136 236
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
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Page 91 and 92: Table 6.3 Load Data Summary. Rated
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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
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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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